Catalyst composition, method for producing same, and use thereof

Abstract

The present invention provides a process for preparing a pre-catalyst composition, the process comprising: (i) reacting an iron species selected from iron salts or hydrates thereof, or iron oxides or hydrates thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an amido group, and an amino group; and optionally, in combination with one or more transition metal species selected from the group consisting of a manganese salt or hydrate thereof, a zirconium salt or hydrate thereof, a copper salt or hydrate thereof, a zinc salt or hydrate thereof, a cobalt salt or hydrate thereof, and a nickel salt or hydrate thereof; optionally (ii) reacting a solution of an iron salt or hydrate thereof and an aqueous alkaline solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate; (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain the pre-catalyst composition. A pre-catalyst composition and catalyst composition prepared by the claimed process and its use in a process for providing a composition comprising carbon monoxide are also provided.

Description

Technical Field

[0001] The present invention provides a method for preparing a precatalyst composition and a catalyst composition. These compositions have uniform dispersibility and stable nanostructure and show high carbon dioxide conversion in the reverse water gas shift reaction without substantial methanation. A precatalyst composition and / or catalyst composition and their use in the conversion of carbon dioxide to carbon monoxide are also provided. Background Art

[0002] Rising greenhouse gas emissions are causing a climate crisis. A major challenge in reducing greenhouse gases is to reduce carbon dioxide emissions. The International Energy Agency reported in 2018 that global energy-related carbon dioxide emissions grew to a historic high of 33.1 billion tons of carbon dioxide, while only a small amount (about 230 million tons per year globally) is currently recycled or reduced.

[0003] Carbon capture and storage (CCS) or utilization (CCU) technologies are being developed with low-carbon technologies. While CCS mainly involves capturing CO2 to avoid its release into the atmosphere, CCU technologies aim to convert CO2 into a variety of value-added products such as olefins, formic acid, dimethyl ether (DME), urea, dimethyl carbonate (DMC), acetic acid, methanol or synthetic natural gas (syngas).

[0004] An important reaction for converting carbon dioxide into value-added products is the reverse water gas shift reaction (rWGS). In rWGS, a catalyst is usually used to convert carbon dioxide into carbon monoxide by hydrogenation. Carbon monoxide is an important starting material in many important commercial processes for preparing useful substances (e.g., manufacturing hydrocarbons by the Fischer-Tropsch process).

[0005] rWGS has been studied using a variety of different catalysts, including precious metals / noble metals such as Pt, Pd, Ru, and Au. et al. (Reaction Chemistry and Engineering, 2021, Vol. 6, p. 954), the catalytic activity and selectivity of Pd, Cu, Ni, Fe, and Pt catalysts for carbon monoxide were recently analyzed. The Pt catalyst showed the highest CO2 conversion, but the selectivity for CO was lower than that of Fe and Cu. Ni showed the highest methanation rate.

[0006] To improve the catalytic performance in rWGS, bimetallic catalyst combinations were also used. In particular, a Cu-ZnO system was used, where the promotion effect of ZnO was associated with a higher Cu dispersion and the Pt-Co catalyst showed a higher CO selectivity relative to the monometallic system.

[0007] Alkali metal doping has been reported to improve CO selectivity and CO conversion. For Pt and Au catalysts, the catalytic enhancement obtained by adding alkali metals is attributed to the metal-O(OH)-base interface, which stabilizes the metal particles, promotes CO dissociation, and favors CO desorption.

[0008] There are many reasons for catalyst deactivation, mainly metal sintering, carbon deposition and sulfur poisoning. The sensitivity to sintering depends on the nature of the metal and its interaction with any support material. The high stability exhibited by Pt supported on zeolite catalysts is attributed to the encapsulation of the metal particles.

[0009] Although noble metal catalysts exhibit higher reaction rates, their high price and limited availability hinder their implementation on a larger scale. The present invention aims to provide a precatalyst composition and / or a catalyst composition, which has a sufficiently low manufacturing cost to be used on a large scale, has good stability, and exhibits good catalytic performance in rWGS. The precatalyst and / or the catalyst composition preferably provides one or more of high carbon dioxide conversion, high carbon monoxide selectivity, and low methanation rate. Summary of the invention

[0010] The present invention provides a precatalyst composition, a catalyst composition and a production method thereof, wherein the composition is generally inexpensive, safe and has abundant raw materials. The precatalyst composition and / or the catalyst composition can be used for reverse water gas shift reaction, has high selectivity for carbon monoxide, has little methane byproduct, and has high carbon dioxide conversion rate.

[0011] In a first aspect, the present invention relates to a method for preparing a precatalyst composition, the method comprising:

[0012] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0013] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof are combined;

[0014] Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate;

[0015] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

[0016] In a second aspect, the present invention provides a precatalyst composition obtained or obtainable according to the method of the first aspect.

[0017] In a third aspect, the present invention provides a method for preparing a catalyst composition, the method comprising:

[0018] (a) providing a precatalyst composition according to the second aspect;

[0019] (b) optionally calcining the precatalyst composition; and

[0020] (c) activating the precatalyst composition to obtain a catalyst composition.

[0021] In a fourth aspect, the present invention provides a catalyst composition obtained or obtainable by the method described in the third aspect.

[0022] In a fifth aspect, the present invention provides a molding composition, the molding composition comprising the precatalyst composition according to the second aspect or the catalyst composition according to the fourth aspect.

[0023] In a sixth aspect, the present invention provides a method for producing a composition comprising carbon monoxide, wherein the method comprises: contacting a feed gas composition comprising carbon dioxide and hydrogen with a precatalyst composition according to the second aspect or a catalyst composition according to the fourth aspect at a temperature of at least 400°C.

[0024] In a seventh aspect, the present invention provides a reactor comprising the precatalyst composition according to the second aspect or the catalyst composition according to the fourth aspect.

[0025] Preferred, suitable and optional features of any particular aspect of the invention are also preferred, suitable and optional features of any other aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD spectra of precatalyst compositions 01, 09, 16, 17, 32, 15 and 20 in Table A herein are shown.

[0027] Figure 2Shown are: a XPS full scan spectrum of precatalyst 17 (Fe-Cr-Zn-Zr-K); b high-resolution XPS spectrum of the Fe 2p peak area of ​​precatalyst 17; c XPS spectrum of Cr 2p of precatalyst 17; d XPS spectrum of Zr 3d of precatalyst 17; e XPS spectrum of Zn 2p of precatalyst 17; f XPS spectrum of K 2p of precatalyst 17; g XPS spectrum of C1s of precatalyst 17; h XPS spectrum of O1s of precatalyst 17.

[0028] Figure 3 A TEM image of pre-catalyst composition 17 (Fe-Cr-Zn-Zr-K) is shown.

[0029] Figure 4 The SEM image, EDX spectrum and elemental analysis of the pre-catalyst composition 17 (Fe-Cr-Zn-Zr-K) are shown, including the elemental analysis of Fe, Cr, Zn, C, O (from left to right). DETAILED DESCRIPTION

[0030] definition

[0031] As used herein, the term "precatalyst" refers to a precursor of a catalytically active species. Typically, the precatalyst needs to be converted into a catalytically active species, such as by oxidation, reduction and / or thermal treatment, or a combination thereof. Activation is preferably carried out by reduction. The precatalyst can be converted into a catalytically active species (i.e., "activated") in situ (i.e., under reaction conditions), or the precatalyst can also be converted into a catalytically active species before being used in the reaction, such as as a preliminary step.

[0032] Unless otherwise indicated, the term "solid" as used herein refers to a solid physical state at standard ambient temperature and pressure (SATP), ie, a temperature of 298.15 K (25°C) and a pressure of 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm).

[0033] Unless otherwise indicated, the terms "gaseous" or "gas" as used herein refer to the gaseous physical state at standard ambient temperature and pressure (SATP), i.e., at a temperature of 298.15 K (25°C) and a pressure of 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm).

[0034] As used herein, "metallic species" refers to any compound containing a metal. Thus, unless otherwise specified, metal species include elemental metals, metal oxides, and other compounds containing metals, i.e., metal salts, alloys, hydroxides, carbides, and hydrides. When stating a specific example of a metal species, the term includes all compounds containing the metal, e.g., iron species include elemental iron, iron oxides, iron salts, iron alloys, iron hydroxides, iron carbides, and iron hydrides, etc., unless otherwise specified.

[0035] As used herein, the term "elemental metal" or specific examples such as "elemental Pd" refer only to metals in an oxidation state of zero.

[0036] Unless otherwise indicated, reference to an element using standard notation refers to that element in any available oxidation state. Similarly, when the term "metal" is used without further limitation, no limitation on oxidation state other than the available oxidation states is intended.

[0037] As used herein, the term "transition metal" refers to an element of one of three series of elements resulting from filling the 3d layer, the 4d layer, and the 5d layer. Unless otherwise indicated, reference to a transition metal generally or using the standard symbol for a specific transition metal refers to the element in any effective oxidation state.

[0038] As used herein, the term "alkali metal" refers to an element from Group 1 of the periodic table.

[0039] As used herein, the term "alkaline earth metal" refers to elements from Group 2 of the periodic table.

[0040] As used herein, the term "rare earth metal" refers to an element selected from the group consisting of scandium, yttrium, lanthanum and the lanthanide series of the periodic table.

[0041] As used herein, "synthesis gas" (also known as synthesis gas) is a fuel gas mixture consisting essentially of hydrogen and carbon monoxide. However, small amounts of carbon dioxide and hydrocarbons may be present.

[0042] Method for preparing a precatalyst composition

[0043] In a first aspect, the present invention relates to a method for preparing a precatalyst composition, the method comprising:

[0044] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0045] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof are combined;

[0046] Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate;

[0047] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

[0048] In one embodiment, the present invention is directed to a method for preparing a precatalyst composition, the method comprising:

[0049] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0050] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof are combined;

[0051] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0052] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0053] In another embodiment, the present invention is directed to a method of preparing a precatalyst composition, the method comprising:

[0054] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0055] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof and nickel salts or hydrates thereof are combined; and

[0056] (ii) calcining the product of (i) to obtain a precatalyst composition.

[0057] In one embodiment, in step (i), the iron species, the chromium salt or hydrate thereof, the organic compound and the optional one or more transition species are combined in solid form.

[0058] In one embodiment, the iron species, the chromium salt or hydrate thereof, the organic compound and the optional one or more transition species are combined with water to form an aqueous solution or mixture. In one embodiment, the aqueous solution or mixture is then dried to remove water and the resulting dried material is calcined.

[0059] Therefore, in one embodiment, the present invention relates to a method for preparing a pre-catalyst composition, the method comprising:

[0060] (i)(a) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0061] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof and nickel salts or hydrates thereof; and

[0062] Water binding;

[0063] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0064] (ii) calcining the dried material of (i)(b) to obtain a precatalyst composition.

[0065] In one embodiment, the present invention is directed to a method for preparing a precatalyst composition, the method comprising:

[0066] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0067] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0068] Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate;

[0069] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

[0070] In one embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0071] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0072] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0073] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate; and

[0074] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0075] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0076] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0077] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined; and

[0078] (ii) calcining the product of (i) to obtain a precatalyst composition.

[0079] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0080] (i)(a) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0081] One or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a zinc salt or a hydrate thereof, and a copper salt or a hydrate thereof; and

[0082] Water binding;

[0083] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0084] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0085] In step (i)(b) of any of the above embodiments, the aqueous product is preferably dried at a temperature of about 70° C. to about 100° C., more preferably at a temperature of about 80° C. to about 100° C., to remove moisture. The dried material obtained is preferably in the form of a powder or a paste.

[0086] Step (i)

[0087] In one embodiment, the iron species is an iron salt or a hydrate thereof.

[0088] In one embodiment, the ratio of the iron salt or its hydrate and the chromium salt or its hydrate is such that the atomic ratio of iron to chromium is about 100: 1 to about 5: 4. The atomic ratio of iron to chromium is preferably about 100: 1 to about 2: 1, preferably about 100: 1 to about 10: 3.

[0089] In another embodiment, the ratio of the iron salt or its hydrate and the chromium salt or its hydrate is such that the atomic ratio of iron to chromium is about 50: 1 to about 5: 1. The atomic ratio of iron to chromium is preferably about 25: 1 to about 5: 1, preferably about 20: 1 to about 5: 1, preferably about 15: 1 to about 5: 1, preferably about 10: 1 to about 5: 1, preferably 10: 1 to about 7: 1, preferably about 10: 1 to about 8: 1.

[0090] In another embodiment, the ratio of the iron salt or its hydrate and the chromium salt or its hydrate is such that the atomic ratio of iron to chromium is about 20:1 to about 5:4. The atomic ratio of iron to chromium is preferably about 20:1 to about 2:1, preferably about 20:1 to about 10:3.

[0091] In another embodiment, the ratio of the iron salt or its hydrate and the chromium salt or its hydrate is such that the atomic ratio of iron to chromium is about 10:1 to about 5:4. The atomic ratio of iron to chromium is preferably about 10:1 to about 2:1, preferably about 10:1 to about 10:3. In another embodiment, the ratio of the iron salt or its hydrate and the chromium salt or its hydrate is such that the atomic ratio of iron to chromium is about 10:1.

[0092] In one embodiment, in step (i), the iron salt or its hydrate is an iron (II) or iron (III) salt or its hydrate. For example, suitable non-limiting examples of iron (II) salts or their hydrates are FeCl2, Fe(OAc)2, FeSO4 and Fe(NO3)2 or their hydrates. Suitable non-limiting examples of iron (III) salts or their hydrates are Fe(NO3)3, FeCl3 and Fe2(SO4)3 or their hydrates.

[0093] In one embodiment, the iron salt or its hydrate of step (i) is selected from one or more of the group consisting of FeCl2, Fe(OAc)2, FeSO4, Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrate.

[0094] In another embodiment, the iron salt or its hydrate of step (i) is selected from one or more of the group consisting of FeCl2, Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrates. In another embodiment, the iron salt or its hydrate of step (i) is selected from one or more of the group consisting of Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrates. In another embodiment, the iron salt or its hydrate of step (i) is selected from one or more of the group consisting of Fe(NO3)2 and Fe(NO3)3 or their hydrates.

[0095] In another embodiment, the iron species is iron oxide or its hydrate. The iron oxide is preferably Fe3O4.

[0096] In one embodiment, the ratio of iron oxide or hydrate thereof and chromium salt or hydrate thereof is such that the atomic ratio of iron to chromium is about 100: 1 to about 5: 4. The atomic ratio of iron to chromium is preferably about 100: 1 to about 2: 1, preferably about 100: 1 to about 10: 3.

[0097] In another embodiment, the ratio of iron oxide or hydrate thereof and chromium salt or hydrate thereof is such that the atomic ratio of iron to chromium is about 20:1 to about 5:4. The atomic ratio of iron to chromium is preferably about 20:1 to about 2:1, preferably about 20:1 to about 10:3.

[0098] In another embodiment, the ratio of iron oxide or hydrate thereof and chromium salt or hydrate thereof is such that the atomic ratio of iron to chromium is about 50: 1 to about 5: 1. The atomic ratio of iron to chromium is preferably about 25: 1 to about 5: 1, preferably about 20: 1 to about 5: 1, preferably about 15: 1 to about 5: 1, preferably about 10: 1 to about 5: 1, preferably 10: 1 to about 7: 1, preferably about 10: 1 to about 8: 1.

[0099] In another embodiment, the ratio of iron oxide or hydrate thereof and chromium salt or hydrate thereof is such that the atomic ratio of iron to chromium is about 10: 1 to about 5: 4. The atomic ratio of iron to chromium is preferably about 10: 1 to about 2: 1, preferably about 10: 1 to about 10: 3, and preferably about 10: 1.

[0100] In one embodiment, in step (i), the chromium salt or its hydrate is a chromium (III) salt or its hydrate. The chromium salt or its hydrate of step (i) is not preferably a chromium (VI) salt or its hydrate. In one embodiment, the method for preparing the pre-catalyst composition does not include adding a chromium (VI) salt or its hydrate.

[0101] In one embodiment, the chromium salt or its hydrate in step (i) is selected from one or more of the group consisting of Cr(NO3)3, CrCl3, Cr(Ac)3 and Cr(OH)3 or its hydrate. The chromium salt or its hydrate in step (i) is preferably Cr(NO3)3 or its hydrate.

[0102] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and, optionally, one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof.

[0103] In another embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and optionally, one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof.

[0104] In each of the above embodiments, the iron species and the chromium salt or hydrate thereof are preferably combined with another transition metal species, preferably with another, two or three transition metal species, preferably with another or two transition metal species.

[0105] The transition metal species is preferably selected from one or more of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof and zinc salts or hydrates thereof.

[0106] In another embodiment, the transition metal species is selected from two or more of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof.

[0107] In another embodiment, the transition metal species is selected from two or more of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, and zinc salts or hydrates thereof.

[0108] In another embodiment, the transition metal species is selected from two of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof.

[0109] In another embodiment, the transition metal species is selected from two of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, and zinc salts or hydrates thereof.

[0110] In another embodiment, the transition metal species is selected from one or more of a manganese salt or a hydrate thereof or a zirconium salt or a hydrate thereof; and one or more of a copper salt or a hydrate thereof or a zinc salt or a hydrate thereof.

[0111] In another embodiment, the transition metal species is selected from:

[0112] (i) a copper salt or a hydrate thereof and a manganese salt or a hydrate thereof; or

[0113] (ii) a zinc salt or a hydrate thereof and a manganese salt or a hydrate thereof; or

[0114] (iii) a copper salt or a hydrate thereof and a zirconium salt or a hydrate thereof; or

[0115] (iv) a zinc salt or a hydrate thereof and a zirconium salt or a hydrate thereof.

[0116] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0117] In another embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino; and optionally, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0118] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0119] In another embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino; and optionally, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0120] In one embodiment, step (i) comprises: combining a manganese salt or a hydrate thereof with an iron chromium salt or a hydrate thereof. In one embodiment, in step (i), the manganese salt or a hydrate thereof is a manganese (II) or (III) salt or a hydrate thereof, preferably a manganese (II) salt or a hydrate thereof. For example, suitable non-limiting examples of manganese salts or hydrates thereof are Mn (NO3) 2, MnSO4, MnCl2, Mn (OAc) 2 and manganese citrate or a hydrate thereof. The manganese salt or a hydrate thereof is preferably Mn (NO3) 2 or a hydrate thereof.

[0121] In one embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 250:1 to about 10:1. The atomic ratio of iron to manganese is preferably from about 250:1 to about 50:1.

[0122] In one embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 100: 1 to about 10: 1. The atomic ratio of iron to manganese is preferably from about 100: 1 to about 40: 1. The atomic ratio of iron to manganese is preferably from about 80: 1 to about 40: 1. The atomic ratio of iron to manganese is preferably from about 60: 1 to about 40: 1.

[0123] In another embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 150:1 to about 10:1. The atomic ratio of iron to manganese is preferably from about 150:1 to about 50:1.

[0124] In another embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 100:1 to about 50:1.

[0125] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, one or more of a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0126] In one embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0127] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0128] In one embodiment, step (i) comprises: combining an iron (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0129] In one embodiment, step (i) comprises: combining a zirconium salt or a hydrate thereof with an iron chromium salt or a hydrate thereof. In one embodiment, in step (i), the zirconium salt or a hydrate thereof is a zirconium (III) or (IV) salt or a hydrate thereof, preferably a zirconium (IV) salt or a hydrate thereof. For example, suitable non-limiting examples of zirconium salts or hydrates thereof are Zr(NO3)4, ZrO(NO3)2, ZrOCl2, zirconium acetate or a hydrate thereof. The zirconium salt or a hydrate thereof is preferably ZrO(NO3)2 or a hydrate thereof.

[0130] In one embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 250:1 to about 10:1. The atomic ratio of iron to zirconium is preferably from about 250:1 to about 50:1.

[0131] In another embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 150:1 to about 10:1. The atomic ratio of iron to zirconium is preferably from about 150:1 to about 50:1.

[0132] In another embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 100: 1 to about 50: 1. The atomic ratio of iron to zirconium is preferably from about 100: 1 to about 80: 1. The atomic ratio of iron to zirconium is preferably about 100: 1.

[0133] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium salt or a hydrate thereof; and optionally, one or more of a manganese salt or a hydrate thereof, a copper salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0134] In one embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0135] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0136] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0137] In one embodiment, step (i) comprises: combining a copper salt or a hydrate thereof with an iron chromium salt or a hydrate thereof. In one embodiment, in step (i), the copper salt is a copper (I) or (II) salt or a hydrate thereof, preferably a copper (II) salt or a hydrate thereof. For example, suitable non-limiting examples of copper salts or hydrates thereof are Cu(NO3)2, Cu(OAc)2, CuCl2, CuSO4, Cu2CO3(OH)2, CuCl, Cu2SO4 and CuNO3 or a hydrate thereof.

[0138] The copper salt or its hydrate is preferably selected from one or more of the group consisting of Cu(NO3)2, Cu(OAc)2, CuCl2, CuSO4 and Cu2CO3(OH)2 or its hydrate. The copper salt or its hydrate is preferably selected from one or more of Cu(NO3)2 and Cu2CO3(OH)2 or its hydrate.

[0139] In one embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 250:1 to about 10:1. The atomic ratio of iron to copper is preferably from about 250:1 to about 50:1.

[0140] In one embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 100: 1 to about 10: 1. The atomic ratio of iron to copper is preferably from about 100: 1 to about 40: 1. The atomic ratio of iron to copper is preferably from about 80: 1 to about 40: 1. The atomic ratio of iron to copper is preferably from about 60: 1 to about 40: 1.

[0141] In another embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 150:1 to about 10:1. The atomic ratio of iron to copper is preferably from about 150:1 to about 50:1.

[0142] In another embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 100:1 to about 50:1.

[0143] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and optionally, one or more of a zinc salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0144] In another embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0145] In one embodiment, step (i) comprises: combining a zinc salt or a hydrate thereof with an iron chromium salt or a hydrate thereof. In one embodiment, in step (i), the zinc salt is a zinc (II) salt or a hydrate thereof. For example, suitable non-limiting examples of zinc salts or hydrates thereof are Zn (NO3) 2, Zn (OAc) 2, ZnCl2 and ZnSO4 or hydrates thereof. The zinc salt or hydrate thereof is preferably Zn (NO3) 2 or a hydrate thereof.

[0146] In one embodiment, the ratio of the iron salt to the zinc salt is such that the atomic ratio of iron to zinc is from about 250:1 to about 10:1. The atomic ratio of iron to zinc is preferably from about 250:1 to about 50:1.

[0147] In one embodiment, the ratio of the iron salt to the zinc salt is such that the atomic ratio of iron to zinc is from about 100:1 to about 10:1. The atomic ratio of iron to zinc is preferably from about 100:1 to about 40:1. The atomic ratio of iron to zinc is preferably from about 80:1 to about 40:1. The atomic ratio of iron to zinc is preferably from about 60:1 to about 40:1. The atomic ratio of iron to zinc is preferably from about 45:1 to about 40:1, preferably about 42:1.

[0148] In another embodiment, the ratio of the iron salt to the zinc salt is such that the atomic ratio of iron to zinc is from about 150:1 to about 10:1. The atomic ratio of iron to zinc is preferably from about 150:1 to about 50:1.

[0149] In another embodiment, the ratio of the iron salt to the zinc salt is such that the atomic ratio of iron to zinc is from about 100:1 to about 50:1.

[0150] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zinc salt or a hydrate thereof; and optionally, one or more of a copper salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0151] In another embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino; a zinc salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0152] In one embodiment, step (i) comprises: combining one or more of an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0153] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and optionally, a manganese salt or a hydrate thereof.

[0154] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof.

[0155] In one embodiment, step (i) comprises: combining one or more of an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof and a manganese salt or a hydrate thereof.

[0156] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0157] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and optionally, a manganese salt or a hydrate thereof.

[0158] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof.

[0159] In one embodiment, step (i) comprises: combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and a manganese salt or a hydrate thereof.

[0160] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and a manganese (II) salt or a hydrate thereof.

[0161] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0162] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zinc salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0163] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and a zirconium (III) or (IV) salt or a hydrate thereof.

[0164] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zinc (II) salt or a hydrate thereof; and a zirconium (III) or (IV) salt or a hydrate thereof.

[0165] In one embodiment, step (i) consists essentially of combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and a manganese salt or a hydrate thereof.

[0166] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0167] In one embodiment, step (i) comprises: combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0168] In one embodiment, step (i) consists essentially of combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0169] In step (i), an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino is combined with a metal salt. The organic compound preferably comprises two or more functional groups selected from carboxyl, hydroxyl, amido and amino. In another embodiment, the organic compound comprises three or more functional groups selected from carboxyl, hydroxyl, amido and amino.

[0170] The organic compound is suitably suitable for complexing metal cations, in particular iron cations. Thus, suitable organic compounds contain one or more functional groups selected from carboxylic acid, hydroxyl, amide or amino groups.

[0171] In one embodiment, the organic compound is selected from hydroxycarboxylic acid, aminocarboxylic acid, polycarboxylic acid or salts thereof. The organic compound is preferably selected from hydroxycarboxylic acid and polycarboxylic acid or salts thereof. Alternatively, the organic compound is selected from hydroxycarboxylic acid and aminocarboxylic acid or salts thereof.

[0172] In one embodiment, the organic compound is a bidentate or polydentate hydroxycarboxylic acid or a salt thereof.

[0173] In one embodiment, the organic compound is C4 to C 12 Carboxylic acid or urea.

[0174] In one embodiment, the organic compound is selected from glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, malic acid, mandelic acid, citric acid, sugar acid, tartaric acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, glycine, hippuric acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA), alanine, valine, leucine and isoleucine and their salts.

[0175] In one embodiment, the organic compound is selected from glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, malic acid, mandelic acid, citric acid, sugar acid, tartaric acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, hippuric acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0176] In one embodiment, the organic compound is selected from hydroxybutyric acid, hydroxyvaleric acid, malic acid, mandelic acid, citric acid, sugar acid, tartaric acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, hippuric acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0177] In one embodiment, the organic compound is selected from hydroxybutyric acid, hydroxyvaleric acid, malic acid, mandelic acid, citric acid, sugar acid, tartaric acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0178] In one embodiment, the organic compound is selected from citric acid, sugar acid, tartaric acid, oxalic acid, salicylic acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0179] In one embodiment, the organic compound is selected from citric acid, sugar acid, tartaric acid, oxalic acid, salicylic acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0180] In one embodiment, the organic compound is selected from citric acid, tartaric acid, oxalic acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA) or a salt thereof. The organic compound is preferably citric acid or urea.

[0181] In another embodiment, the organic compound is selected from malic acid, salicylic acid, tartaric acid, urea, oxalic acid, citric acid, nitrilotriacetic acid (NTA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0182] In one embodiment, the molar ratio of the organic compound to the metal in step (i) is from about 0.4: 1 to about 10: 1. The molar ratio of the organic compound to the metal is preferably from about 0.4: 1 to about 5: 1. The molar ratio of the organic compound to the metal is preferably from about 0.4: 1 to about 2: 1 or from about 0.4: 1 to about 1: 1.

[0183] In one embodiment, the molar ratio of the organic compound to the metal in step (i) is from about 1:1 to about 10:1. The molar ratio of the organic compound to the metal is preferably from about 1:1 to about 5:1. The molar ratio of the organic compound to the metal is preferably from about 1:1 to about 3:1 or from about 1:1 to about 1:1.

[0184] In one embodiment, the molar ratio of the organic compound to the metal in step (i) is from about 0.8: 1 to about 10: 1. The molar ratio of the organic compound to the metal is preferably from about 0.8: 1 to about 5: 1. The molar ratio of the organic compound to the metal is preferably from about 0.8: 1 to about 2: 1 or from about 0.8: to about 1: 1.

[0185] In one embodiment, the molar ratio of the organic compound to the metal in step (i) is about 1:1 to about 10:1. The molar ratio of the organic compound to the metal is preferably about 1:1 to about 5:1. The molar ratio of the organic compound to the metal is preferably about 1:1 to about 2:1.

[0186] In one embodiment, step (i) comprises: making an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a zinc salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0187] In one embodiment, step (i) comprises: making an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0188] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a zinc salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0189] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0190] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0191] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0192] In another embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a zirconium salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0193] In another embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof and a zinc salt or a hydrate thereof.

[0194] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0195] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a manganese salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0196] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0197] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid, preferably citric acid, or urea; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0198] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; and optionally, a combination of one or more of a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof.

[0199] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0200] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof.

[0201] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and optionally, a zirconium salt or a hydrate thereof.

[0202] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid, preferably citric acid, or urea; a copper(II) salt or a hydrate thereof; and, optionally, a zirconium salt or a hydrate thereof.

[0203] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0204] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0205] In one embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0206] In another embodiment, step (i) comprises: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; and a manganese (II) salt or a hydrate thereof.

[0207] In one embodiment, step (i) consists essentially of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof, a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and a manganese salt or a hydrate thereof.

[0208] In one embodiment, step (i) consists essentially of the following steps: an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and a manganese salt or a hydrate thereof.

[0209] In one embodiment, step (i) consists essentially of the following steps: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; and a manganese (II) salt or a hydrate thereof.

[0210] In one embodiment, step (i) consists essentially of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof, a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0211] In one embodiment, step (i) consists essentially of the following steps: an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; and a zirconium salt or a hydrate thereof.

[0212] In one embodiment, step (i) consists essentially of the following steps: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0213] In one embodiment, step (i) consists of / essentially consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; and a zirconium (IV) salt or a hydrate thereof.

[0214] In another embodiment, step (i) consists of / consists essentially of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; and a manganese (II) salt or a hydrate thereof.

[0215] In one embodiment, in step (i), the iron salt or hydrate thereof, or iron oxide or hydrate thereof; chromium salt or hydrate thereof; the organic compound; and optionally, the one or more transition metal species are combined in solid form under ambient conditions, respectively, and mixed or ground to form a paste or powder. Suitable mixing and grinding techniques are known in the art, including at least grinding in a pestle and mortar, or bead milling or ball milling.

[0216] In another embodiment, in step (i), one or more components may be mixed with water, and these components are combined to form an aqueous solution or a mixture. Preferably, the aqueous solution or the mixture is stirred. In one embodiment, the weight ratio of the transition metal species and the organic compound to water is about 1:1 to about 5:1, preferably about 1:1 to about 3:1, and preferably about 2:1.

[0217] Prior to the calcination step, the aqueous solution or the mixture is preferably dried. In one embodiment, the aqueous solution or the mixture is dried at a temperature of about 70° C. to about 100° C., more preferably about 80° C. to about 100° C., to remove moisture. The resulting dried material is preferably a powder or paste.

[0218] In one embodiment, step (i) comprises: (i)(a) combining an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group and an amino group; and one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof; and water; and (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance.

[0219] In another embodiment, in step (i), the iron salt or hydrate thereof, the chromium salt or hydrate thereof and the organic compound; and optionally, one or more of the manganese salt or hydrate thereof, the zinc salt or hydrate thereof, the zirconium salt or hydrate thereof and the copper salt or hydrate thereof are combined in solid form under ambient conditions, respectively, and mixed or ground to form a paste or powder. Suitable mixing and grinding techniques are known in the art and include at least grinding in a pestle and mortar, or bead or ball milling.

[0220] In one embodiment, step (i) further comprises: combining one or more of alkali metal species, alkaline earth metal species and rare earth metal species. Step (i) further preferably comprises: combining one or more of alkali metal species and / or alkaline earth metal species. Step (i) further preferably comprises: combining one or more of alkali metal species and / or rare earth metal species. Step (i) further preferably comprises: combining alkali metal species. The alkali metal species, the alkaline earth metal species or the rare earth metal species are preferably added in step (i) in the form of their salts, hydroxides, oxides or hydrates, preferably in the form of their salts or hydrates.

[0221] In one embodiment, the alkali metal species is an alkali metal salt or a hydrate thereof. In another embodiment, the alkali metal salt is an alkali metal nitrate, an alkali metal carbonate, an alkali metal bicarbonate, an alkali metal acetate or a hydrate thereof. In another embodiment, the alkali metal salt is an alkali metal nitrate or an alkali metal carbonate or a hydrate thereof.

[0222] In one embodiment, the alkali metal is selected from the group consisting of lithium, sodium, potassium and cesium. In another embodiment, the alkali metal is selected from lithium, sodium and potassium.

[0223] The alkali metal species is preferably selected from potassium nitrate, potassium carbonate, sodium nitrate, sodium carbonate, lithium carbonate, cesium carbonate or hydrates thereof.

[0224] In one embodiment, the atomic ratio of iron to alkali metal in step (i) is from about 100: 1 to about 5: 1. The atomic ratio of iron to alkali metal is preferably from about 50: 1 to about 5: 1. The atomic ratio of iron to alkali metal is preferably from about 40: 1 to about 5: 1, or from about 25: 1 to about 5: 1.

[0225] In another embodiment, the atomic ratio of iron to alkali metal in step (i) is about 50: 1 to about 5: 1. The atomic ratio of iron to alkali metal is preferably about 50: 1 to about 10: 1. The atomic ratio of iron to alkali metal is preferably about 50: 1 to about 15: 1, or about 50: 1 to about 20: 1.

[0226] In another embodiment, the atomic ratio of iron to alkali metal in step (i) is from about 40:1 to about 5:1. The atomic ratio of iron to alkali metal is preferably from about 40:1 to about 10:1. The atomic ratio of iron to alkali metal is preferably from about 40:1 to about 15:1, or from about 40:1 to about 20:1. The atomic ratio of iron to alkali metal is preferably 20:1.

[0227] In one embodiment, the alkaline earth metal species is an alkaline earth metal salt, hydroxide, oxide or hydrate thereof. In another embodiment, the alkaline earth metal species is an alkaline earth metal salt or a hydrate thereof.

[0228] In one embodiment, the alkaline earth metal salt is an alkaline earth metal nitrate, an alkaline earth metal carbonate, an alkaline earth metal bicarbonate, an alkaline earth metal acetate or a hydrate thereof. In another embodiment, the alkaline earth metal salt is an alkaline earth metal nitrate or an alkaline earth metal carbonate or a hydrate thereof.

[0229] In one embodiment, the alkaline earth metal is selected from the group consisting of magnesium, calcium and barium, preferably selected from magnesium and calcium, and more preferably selected from calcium.

[0230] The alkaline earth metal species is preferably selected from calcium salts or hydrates thereof or magnesium salts or hydrates thereof. In one embodiment, the alkaline earth metal species is selected from calcium nitrate, calcium carbonate, magnesium nitrate and magnesium carbonate or hydrates thereof. In another embodiment, the alkaline earth metal species is selected from calcium nitrate and calcium carbonate.

[0231] In one embodiment, the atomic ratio of iron to alkaline earth metal in step (i) is from about 100: 1 to about 5: 1. The atomic ratio of iron to alkaline earth metal is preferably from about 50: 1 to about 5: 1. The atomic ratio of iron to alkaline earth metal is preferably from about 40: 1 to about 5: 1 or from about 25: 1 to about 5: 1.

[0232] In another embodiment, the atomic ratio of iron to alkaline earth metal in step (i) is about 50: 1 to about 5: 1. The atomic ratio of iron to alkaline earth metal is preferably about 50: 1 to about 10: 1. The atomic ratio of iron to alkaline earth metal is preferably about 50: 1 to about 15: 1 or about 50: 1 to about 20: 1.

[0233] In another embodiment, the atomic ratio of iron to alkaline earth metal in step (i) is about 40: 1 to about 5: 1. The atomic ratio of iron to alkaline earth metal is preferably about 40: 1 to about 10: 1. The atomic ratio of iron to alkaline earth metal is preferably about 40: 1 to about 15: 1 or about 40: 1 to about 20: 1.

[0234] In one embodiment, the rare earth metal species is a rare earth metal salt, hydroxide, oxide or hydrate thereof. In another embodiment, the rare earth metal species is a rare earth metal salt or a hydrate thereof.

[0235] In one embodiment, the rare earth metal salt is a rare earth metal nitrate, a rare earth metal carbonate, a rare earth metal bicarbonate, a rare earth metal acetate or a hydrate thereof. In one embodiment, the rare earth metal salt is a rare earth metal nitrate or a rare earth metal carbonate or a hydrate thereof.

[0236] In one embodiment, the rare earth metal is selected from the group consisting of yttrium, lanthanum, cerium, praseodymium and erbium.

[0237] The rare earth metal species is preferably selected from yttrium nitrate, cerium nitrate, lanthanum nitrate, praseodymium nitrate, erbium nitrate or hydrates thereof.

[0238] In one embodiment, the atomic ratio of iron to rare earth metal in step (i) is from about 200: 1 to about 50: 1. The atomic ratio of iron to rare earth metal is preferably from about 150: 1 to about 50: 1. The atomic ratio of iron to rare earth metal is preferably from about 100: 1 to about 50: 1 or from about 100: 1 to about 75: 1.

[0239] In another embodiment, the atomic ratio of iron to rare earth metal in step (i) is about 300: 1 to about 50: 1. The atomic ratio of iron to rare earth metal is preferably about 300: 1 to about 75: 1. The atomic ratio of iron to rare earth metal is preferably about 200: 1 to about 75: 1 or about 150: 1 to about 75: 1.

[0240] In one embodiment, step (i) comprises / consists essentially of / consists of: combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof; and one or more of an alkali metal species, an alkaline earth metal species and a rare earth metal species.

[0241] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof; and an alkali metal species.

[0242] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof; and an alkaline earth metal species.

[0243] In another embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof; an alkali metal species; and a rare earth metal species.

[0244] In one embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0245] In one embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0246] In one embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zinc salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0247] In one embodiment, step (i) comprises / consists essentially of / consists of combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zinc salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0248] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a zinc salt or a hydrate thereof, and a copper salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0249] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a zinc salt or a hydrate thereof, and a copper salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0250] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0251] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0252] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0253] In one embodiment, step (i) comprises / consists essentially of / consists of the following steps: an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; a 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper salt or a hydrate thereof; one or more of a zirconium salt or a hydrate thereof or a manganese salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0254] In one embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0255] In one embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0256] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; an alkali metal salt or a hydrate thereof; and a rare earth metal salt or a hydrate thereof.

[0257] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0258] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0259] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0260] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0261] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and an alkali metal salt or a hydrate thereof.

[0262] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and an alkaline earth metal salt or a hydrate thereof.

[0263] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 The present invention is a combination of an organic compound of carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and a potassium salt or a hydrate thereof. The atomic ratio of Fe:Cr is preferably about 10:1, and / or the atomic ratio of Fe:Zr is preferably about 100:1, and / or the atomic ratio of Fe:K is preferably about 20:1, and / or the atomic ratio of Fe:Zn is preferably about 42:1.

[0264] In another embodiment, step (i) comprises / consists essentially of / consists of: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 The present invention relates to a combination of an organic compound of carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and a calcium salt or a hydrate thereof. The atomic ratio of Fe:Cr is preferably about 10:1, and / or the atomic ratio of Fe:Zr is preferably about 100:1, and / or the atomic ratio of Fe:Ca is preferably about 20:1, and / or the atomic ratio of Fe:Zn is preferably about 42:1.

[0265] Step (ii) - Precipitation

[0266] In one embodiment, the method for preparing a pre-catalyst composition comprises step (ii), i.e., combining a solution of an iron salt or its hydrate and an alkaline aqueous solution; and optionally, one or more of a manganese salt or its hydrate, a zirconium salt or its hydrate and a copper salt or its hydrate to obtain a precipitate.

[0267] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate.

[0268] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution; and optionally, a copper salt or a hydrate thereof, to obtain a precipitate.

[0269] In one embodiment, step (ii) consists essentially of combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0270] In one embodiment, in step (ii), the iron salt or its hydrate is an iron (II) or iron (III) salt or its hydrate. For example, suitable non-limiting examples of iron (II) salts or their hydrates are FeCl2, Fe(OAc)2, FeSO4 and Fe(NO3)2 or their hydrates. Suitable non-limiting examples of iron (III) salts or their hydrates are Fe(NO3)3, FeCl3 and Fe2(SO4)3 or their hydrates.

[0271] In one embodiment, the iron salt or its hydrate of step (ii) is selected from one or more of the group consisting of FeCl2, Fe(OAc)2, FeSO4, Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrate.

[0272] In another embodiment, the iron salt or its hydrate of step (ii) is selected from one or more of the group consisting of Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrate. In another embodiment, the iron salt or its hydrate of step (ii) is selected from one or more of Fe(NO3)2 and Fe(NO3)3 or its hydrate.

[0273] In one embodiment, step (ii) comprises: combining a manganese salt or a hydrate thereof with the iron salt or a hydrate thereof. In one embodiment, in step (ii), the manganese salt or a hydrate thereof is a manganese (II) or (III) salt or a hydrate thereof, preferably a manganese (II) salt or a hydrate thereof. For example, suitable non-limiting examples of manganese salts or hydrates thereof are Mn (NO3) 2, MnSO4, MnCl2, Mn (OAc) 2 and manganese citrate or a hydrate thereof. The manganese salt is preferably Mn (NO3) 2 or a hydrate thereof.

[0274] In one embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 250:1 to about 10:1. The atomic ratio of iron to manganese is preferably from about 250:1 to about 50:1.

[0275] In another embodiment, the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 150:1 to about 10:1. The atomic ratio of iron to manganese is preferably from about 150:1 to about 50:1.

[0276] In one embodiment, step (ii) comprises: combining a zirconium salt or a hydrate thereof with the iron salt or a hydrate thereof. In one embodiment, in step (ii), the zirconium salt or a hydrate thereof is a zirconium (III) or (IV) salt or a hydrate thereof, preferably a zirconium (IV) salt or a hydrate thereof. For example, suitable non-limiting examples of zirconium salts or hydrates thereof are Zr(NO3)4, ZrO(NO3)2, ZrOCl2, zirconium acetate or a hydrate thereof. The zirconium salt is preferably ZrO(NO3)2 or a hydrate thereof.

[0277] In one embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 250:1 to about 10:1. The atomic ratio of iron to zirconium is preferably from about 250:1 to about 50:1, preferably from about 250:1 to about 75:1.

[0278] In another embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is about 150:1 to about 10:1. The atomic ratio of iron to zirconium is preferably about 150:1 to about 50:1, preferably about 150:1 to about 75:1.

[0279] In another embodiment, the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 100: 1 to about 50: 1. The atomic ratio of iron to zirconium is preferably from about 100: 1 to about 75:1.

[0280] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and an alkaline aqueous solution; and optionally, a copper salt or a hydrate thereof, to obtain a precipitate.

[0281] In one embodiment, step (ii) comprises: combining a solution of an iron (II) or (III) salt or a hydrate thereof, a zirconium (IV) salt or a hydrate thereof and an alkaline aqueous solution; and optionally, a copper salt or a hydrate thereof, to obtain a precipitate.

[0282] In one embodiment, step (ii) comprises: combining a copper salt or its hydrate with the iron salt or its hydrate. In one embodiment, in step (ii), the copper salt or its hydrate is a copper (I) or (II) salt or its hydrate, preferably a copper (II) salt or its hydrate. For example, suitable non-limiting examples of copper salts or their hydrates are Cu (NO3) 2, Cu (OAc) 2, CuCl2, CuSO4, Cu2CO3 (OH) 2, CuCl, Cu2SO4 and CuNO3 or its hydrates. The copper salt or its hydrate is preferably selected from one or more of the group consisting of Cu (NO3) 2, Cu (OAc) 2, CuCl2, CuSO4 and Cu2CO3 (OH) 2 or its hydrates. The copper salt or its hydrate is preferably selected from one or more of Cu (NO3) 2 and Cu2CO3 (OH) 2 or its hydrates.

[0283] In one embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 250:1 to about 10:1. The atomic ratio of iron to copper is preferably from about 250:1 to about 50:1.

[0284] In another embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is about 150:1 to about 10:1. The atomic ratio of iron to copper is preferably about 150:1 to about 50:1, preferably about 150:1 to about 75:1.

[0285] In another embodiment, the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 100:1 to about 50:1. The atomic ratio of iron to copper is preferably from about 100:1 to about 75:1.

[0286] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof, a copper salt or a hydrate thereof, and an alkaline aqueous solution; and optionally, a zirconium salt or a hydrate thereof, to obtain a precipitate.

[0287] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof, a copper salt or a hydrate thereof, and an alkaline aqueous solution; and optionally, a manganese salt or a hydrate thereof, to obtain a precipitate.

[0288] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof, a copper salt or a hydrate thereof, a manganese salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0289] In one embodiment, step (ii) comprises: combining a solution of an iron (II) or (III) salt or a hydrate thereof, a copper (I) or (II) salt or a hydrate thereof and an alkaline aqueous solution; and optionally, a zirconium salt or a hydrate thereof, to obtain a precipitate.

[0290] In one embodiment, step (ii) comprises: combining a solution of an iron salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0291] In one embodiment, step (ii) comprises: combining a solution of an iron (II) or (III) salt or a hydrate thereof, a zirconium (IV) salt or a hydrate thereof, a copper (I) or (II) salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0292] In one embodiment, step (ii) consists essentially of combining a solution of an iron (II) and / or (III) salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0293] In one embodiment of the method for preparing a precatalyst composition, the manganese salt, the copper salt and / or the zirconium salt or a hydrate thereof are optionally added in step (i) or step (ii), but not in both step (i) and step (ii). In one embodiment, the manganese salt, the copper salt and / or the zirconium salt or a hydrate thereof are added only in step (i). In another embodiment, the manganese salt, the copper salt and / or the zirconium salt or a hydrate thereof are added only in step (ii).

[0294] In one embodiment of the method for preparing the precatalyst composition, the molar ratio of the iron salt or its hydrate in step (i) to the iron salt or its hydrate in step (ii) is about 10:1 to about 1:1, preferably about 5:1 to about 2:1.

[0295] In one embodiment, in step (ii), the alkaline aqueous solution is selected from aqueous ammonia, aqueous urea solution, aqueous hydroxide solution such as NaOH or KOH solution, aqueous carbonate solution such as sodium carbonate, etc. The alkaline aqueous solution is preferably aqueous ammonia.

[0296] The alkaline aqueous solution is used to affect the precipitation of divalent and trivalent iron compounds. The precipitation can be achieved by adding the alkaline aqueous solution to a solution of the iron salt or its hydrate, preferably to an aqueous solution of the iron salt or its hydrate. The alkaline solution is added to the iron salt solution until the pH of the combination is about 7 to about 14, preferably about 8 to about 14, preferably about 9 to about 14, preferably about 9 to about 12, preferably about 9, 10 or 11.

[0297] In one embodiment, the precipitate comprises one or more iron species selected from iron oxides or hydroxides or hydrates thereof. In one embodiment, the precipitate comprises one or more iron species selected from Fe(OH)3, Fe(OH)2 and FeO(OH) or hydrates thereof.

[0298] The precipitate is preferably formed in a temperature range of about 10°C to about 100°C. In one embodiment, step (ii) is preferably performed in a temperature range of about 20°C to about 100°C. In one embodiment, step (ii) is preferably performed in a temperature range of about 20°C to about 90°C. In another embodiment, step (ii) is preferably performed in a temperature range of about 50°C to about 90°C. In another embodiment, step (ii) is preferably performed in a temperature range of about 20°C to about 65°C. In another embodiment, step (ii) is preferably performed in a temperature range of about 50°C to about 65°C.

[0299] The precipitate may be removed from the mother liquor by filtration or the like, and may optionally be washed and dried. However, in order to avoid difficulty in filtering the viscous gelatinous iron oxides, hydroxides and hydrates thereof, the precipitate and the mother liquor may be heated at a temperature in the range of about 10°C to about 100°C to obtain a wet paste or powder. In one embodiment, in step (ii), the wet paste is preferably formed at a temperature in the range of about 50°C to about 100°C or about 50°C to about 80°C.

[0300] In one embodiment, the method of preparing the precatalyst composition comprises:

[0301] (i) combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0302] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0303] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0304] In another embodiment, the method of preparing the precatalyst composition comprises:

[0305] (i) combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0306] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0307] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0308] In one embodiment, the method of preparing the precatalyst composition comprises:

[0309] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0310] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0311] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0312] In another embodiment, the method of preparing the precatalyst composition comprises:

[0313] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0314] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0315] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0316] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0317] (i) combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0318] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0319] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0320] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0321] (i) combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0322] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0323] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0324] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0325] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0326] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0327] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0328] In another embodiment, the method of preparing the precatalyst composition comprises:

[0329] (i) combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0330] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0331] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0332] In another embodiment, the method of preparing the precatalyst composition comprises:

[0333] (i) combining an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0334] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0335] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0336] In another embodiment, the method of preparing the precatalyst composition comprises:

[0337] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0338] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0339] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0340] In another embodiment, the method of preparing the precatalyst composition comprises:

[0341] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0342] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0343] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0344] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0345] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0346] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0347] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0348] In one embodiment, the method of preparing the precatalyst composition comprises:

[0349] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; selected from C4 to C 12an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0350] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0351] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0352] In one embodiment, the method of preparing the precatalyst composition comprises:

[0353] (i) an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0354] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0355] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0356] In one embodiment, the method of preparing the precatalyst composition comprises:

[0357] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0358] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0359] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0360] In another embodiment, the method of preparing the precatalyst composition comprises:

[0361] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0362] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0363] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0364] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0365] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0366] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0367] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0368] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0369] (i) an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0370] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0371] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0372] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0373] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a manganese (II) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0374] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0375] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0376] In another embodiment, the method of preparing the precatalyst composition comprises:

[0377] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0378] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0379] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0380] In another embodiment, the method of preparing the precatalyst composition comprises:

[0381] (i) an iron salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0382] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0383] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0384] In another embodiment, the method of preparing the precatalyst composition comprises:

[0385] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0386] (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof, to obtain a precipitate;

[0387] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0388] In another embodiment, the method of preparing the precatalyst composition comprises:

[0389] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0390] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0391] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0392] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0393] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and optionally, a copper salt or a hydrate thereof;

[0394] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0395] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

[0396] Step (iii) - Calcination

[0397] In one embodiment, the product of step (i) is calcined to obtain a precatalyst composition, preferably a powder. Therefore, in certain embodiments described above lacking the precipitation step, the calcination may be labeled as step (ii). However, regardless of whether it is labeled as step (ii) or step (iii), the following embodiments apply to the calcination step.

[0398] In another embodiment, in step (iii) of the process of the present invention, the products of step (i) and step (ii) are combined and the combination is calcined to obtain a precatalyst composition, preferably a powder.

[0399] The product of step (i) is preferably combined with the product of step (ii) and mixed or ground to form a paste or powder. Suitable mixing and grinding techniques are known in the art and include at least grinding in a pestle and mortar, or bead or ball milling. Several different grinding techniques are known in the art and may be used in place of bead or ball milling.

[0400] In one embodiment, the combined product of step (i) and step (ii) is heated while mixing or grinding. Preferably, the combination is heated at a temperature in the range of about 10°C to about 100°C while mixing or grinding. In one embodiment, the combination is heated at a temperature in the range of about 50°C to about 100°C or about 50°C to about 80°C. Thereafter, a dry paste or powder may be obtained.

[0401] The product of step (i) or the combined product of steps (i) and (ii) is calcined. The effect of calcination is preferably to burn or decompose the organic compound and any organic salt remaining in the combination and to form a metal oxide.

[0402] Combustion of the organic material advantageously provides a resulting procatalyst composition having one or more advantageous properties, such as nanostructure and favorable dispersion of the metal species and promoter.

[0403] In one embodiment, the calcining is carried out at a temperature between about 400°C to about 1000°C, or about 400°C to about 700°C, or about 400°C to about 600°C, or about 500°C to about 700°C, or about 500°C to about 600°C.

[0404] In another embodiment, the calcining is carried out at a temperature between about 500°C to about 1000°C, or about 500°C to about 800°C, or about 500°C to about 700°C, or about 600°C to about 800°C, or about 600°C to about 700°C.

[0405] In another embodiment, the calcining is performed at a temperature between about 600°C and about 1000°C, or about 600°C and about 800°C, or about 600°C and about 700°C.

[0406] In another embodiment, the calcining is performed at a temperature between about 700°C and about 1000°C, or about 700°C and about 800°C, or about 700°C and about 750°C.

[0407] The calcination is preferably carried out by heating the sample at a heating rate of about 3°C ​​to about 10°C per minute, preferably about 5°C per minute. The sample is preferably heated to a temperature of about 500°C, preferably to about 600°C, preferably to about 700°C, preferably to about 750°C, preferably to about 800°C.

[0408] The calcination is preferably carried out in air, preferably in static air. Generally, the calcination will lead to the decomposition or partial combustion of the organic components of the precursor.

[0409] In one embodiment, the combination is calcined for about 1 hour to about 24 hours, preferably for about 1 hour to about 10 hours, preferably for about 2 hours to about 10 hours.

[0410] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 400° C. to about 1000° C. for about 1 hour to 24 hours to obtain a precatalyst composition.

[0411] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 400° C. to about 800° C. for about 1 hour to 24 hours to obtain a precatalyst composition.

[0412] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 400° C. to about 700° C. for about 1 hour to 24 hours to obtain a precatalyst composition.

[0413] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 400° C. to about 600° C. for about 1 hour to 24 hours to obtain a precatalyst composition.

[0414] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 500° C. to about 800° C. for about 2 hours to 10 hours to obtain a precatalyst composition.

[0415] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 500° C. to about 700° C. for about 2 hours to 10 hours to obtain a precatalyst composition.

[0416] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined at about 500° C. to about 600° C. for about 2 hours to 10 hours to obtain a precatalyst composition.

[0417] In one embodiment, in step (iii), the product of step (i) or the combined product of step (i) and step (ii) is calcined by heating to about 700° C. at a rate of about 5° C. per minute. The calcined product is preferably maintained at about 700° C. for about 4 to 8 hours, preferably for about 6 hours.

[0418] Optional further steps

[0419] In one embodiment, the method further comprises a step (iv), wherein the precatalyst composition of step (iii) is further treated with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, the treated precatalyst composition is calcined. Preferably, the precatalyst composition of step (iii) is impregnated with the one or more transition metal salts or hydrates thereof.

[0420] The transition metal solution comprising one or more transition metal salts or hydrates thereof is preferably an aqueous solution.

[0421] In one embodiment, the transition metal salt or its hydrate is selected from one or more of Pd, Pt, Ru, Rh, Au and Cu salts or their hydrates. The transition metal salt or its hydrate is preferably selected from one or more of Pd, Pt, Ru and Cu salts or their hydrates. The transition metal salt or its hydrate is preferably selected from one or more of Pd, Ru and Cu salts or their hydrates.

[0422] In one embodiment, the transition metal salt or its hydrate is a palladium salt or its hydrate. The palladium salt or its hydrate is preferably a palladium (II) salt or its hydrate. For example, suitable non-limiting examples of palladium (II) salts or their hydrates are PdCl2, Pd (OAc)2 and Pd (NO3)2 or its hydrate. In one embodiment, the transition metal salt or its hydrate is PdCl2 or its hydrate.

[0423] In one embodiment, in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal in the precatalyst composition is from about 10000: 1 to about 10: 1. The atomic ratio of iron to transition metal is preferably from about 1000: 1 to about 100: 1, preferably from about 500: 1 to about 100: 1.

[0424] In one embodiment, in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal in the precatalyst composition is from about 250: 1 to about 10: 1. The atomic ratio of iron to transition metal is preferably from about 250: 1 to about 50: 1, preferably from about 250: 1 to about 75: 1.

[0425] In another embodiment, in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal in the precatalyst composition is from about 150: 1 to about 10: 1. The atomic ratio of iron to transition metal is preferably from about 150: 1 to about 50: 1, preferably from about 150: 1 to about 75: 1.

[0426] In another embodiment, in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal is about 100: 1 to about 50: 1. The atomic ratio of iron to transition metal is preferably about 100: 1 to about 75: 1.

[0427] In one embodiment, the transition metal salt is not a cobalt salt or a hydrate thereof. In another embodiment, the transition metal salt is not a platinum salt or a hydrate thereof. In another embodiment, the transition metal salt is not a nickel salt or a hydrate thereof. In another embodiment, the transition metal salt is not a ruthenium salt or a hydrate thereof. In one embodiment, the transition metal salt is not a Co, Pt, Ni or Ru salt or a hydrate thereof.

[0428] After being treated with the transition metal salt solution, the precatalyst composition is preferably dried, for example at a temperature of about 50°C to about 100°C, and then optionally calcined.

[0429] In one embodiment, the calcining is carried out at a temperature between about 100°C to about 1000°C, or about 200°C to about 700°C, or about 500°C to about 700°C, or about 400°C to about 600°C, or about 500°C to about 600°C.

[0430] The calcination is preferably carried out in air, preferably in static air.

[0431] In one embodiment, the combination is calcined for about 1 hour to 24 hours, preferably for about 1 hour to about 10 hours, preferably for about 2 hours to about 10 hours.

[0432] In one embodiment, the method of preparing a pre-catalyst composition comprises:

[0433] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0434] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0435] Optionally (ii) a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and

[0436] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined to obtain a precipitate;

[0437] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0438] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0439] In one embodiment, the method of preparing a pre-catalyst composition comprises:

[0440] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0441] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0442] (ii) mixing a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution; and

[0443] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined to obtain a precipitate;

[0444] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0445] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0446] In one embodiment, the method of preparing a pre-catalyst composition comprises:

[0447] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0448] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0449] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0450] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0451] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0452] In one embodiment, the method of preparing a pre-catalyst composition comprises:

[0453] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0454] Optionally, one or more of a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof are combined;

[0455] (ii) mixing a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution; and

[0456] Optionally, one or more of a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof are combined to obtain a precipitate;

[0457] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0458] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0459] In another embodiment, the method of preparing the pre-catalyst composition comprises:

[0460] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; a zirconium (IV) salt or a hydrate thereof; and a copper (II) salt or a hydrate thereof;

[0461] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0462] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0463] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0464] In another embodiment, the method of preparing the pre-catalyst composition comprises:

[0465] (i) combining an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; a zirconium (IV) salt or a hydrate thereof; and a copper (II) salt or a hydrate thereof;

[0466] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0467] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0468] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more palladium salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0469] In another embodiment, the method of preparing the pre-catalyst composition comprises:

[0470] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and a copper (II) salt or a hydrate thereof;

[0471] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0472] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0473] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more palladium salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0474] In another embodiment, the method of preparing the precatalyst composition consists essentially of the following steps:

[0475] (i) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zirconium (IV) salt or a hydrate thereof; and a copper (II) salt or a hydrate thereof;

[0476] (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution to obtain a precipitate;

[0477] (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition; and

[0478] (iv) treating the precatalyst composition of (iii) with a transition metal solution comprising one or more palladium salts or hydrates thereof; and optionally, calcining the precatalyst composition.

[0479] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0480] (i)(a) combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof; and water;

[0481] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0482] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0483] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0484] (i)(a) combining an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; one or more transition metal species selected from the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, a zinc salt or a hydrate thereof, a cobalt salt or a hydrate thereof and a nickel salt or a hydrate thereof; one or more of an alkali metal species, an alkaline earth metal species and a rare earth metal species; and water;

[0485] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0486] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0487] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0488] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and a water combination;

[0489] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0490] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0491] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0492] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; an alkali metal salt or a hydrate thereof; and a water combination;

[0493] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0494] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0495] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0496] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; and a water combination;

[0497] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0498] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0499] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0500] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a zirconium (IV) salt or a hydrate thereof; an alkali metal salt or a hydrate thereof; and a water combination;

[0501] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0502] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0503] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0504] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and a water combination;

[0505] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0506] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0507] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0508] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 an organic compound of a carboxylic acid (preferably citric acid) or urea; a copper (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; an alkali metal salt or a hydrate thereof; and a water combination;

[0509] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0510] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0511] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0512] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; and a water combination;

[0513] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0514] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0515] In another embodiment, the method of preparing the pre-catalyst composition comprises / consists essentially of / consists of the following steps:

[0516] (i) (a) an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a compound selected from C4 to C 12 An organic compound of a carboxylic acid (preferably citric acid) or urea; a zinc (II) salt or a hydrate thereof; a manganese (II) salt or a hydrate thereof; an alkali metal salt or a hydrate thereof; and a water combination;

[0517] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0518] (ii) calcining the product of (i)(b) to obtain a precatalyst composition.

[0519] In one embodiment, the precatalyst composition is formed into a precatalyst unit.

[0520] In another embodiment, the product of step (iii) and / or step (iv) is formed into pre-catalyst units such as granules or tablets.

[0521] In one embodiment, the product of step (iii) and / or step (iv) is mixed with a lubricant or adhesive before being formed into a pre-catalyst unit. Suitable lubricants and adhesives are known in the art. In one embodiment, the lubricant or the adhesive is selected from one or more of the group consisting of sesbania rubber powder, calcium aluminate cement or clay. The adhesive is preferably sesbania rubber powder.

[0522] In one embodiment, the lubricant or the binder is added to the product of step (iii) and / or step (iv) in an amount of about 0.1% to about 5% (w / w).

[0523] The shaped precatalyst unit can be prepared by any suitable means known in the art. For example, the product of step (iii) and / or step (iv) can be mixed with the lubricant and / or the binder and granulated and tableted in a tablet press, or extruded in an extruder to obtain particles of a suitable size, etc.

[0524] Preferably, the maximum and minimum dimensions of the shaped precatalyst unit range from about 0.5 mm to about 25 mm, preferably from about 0.5 mm to about 20 mm.

[0525] Molding composition

[0526] In one aspect, the present invention relates to a shaped composition, comprising a precatalyst composition obtained or obtainable according to the method of the first aspect described in any one of the above embodiments.

[0527] In one embodiment, the molding composition is in the form of granules or tablets. The maximum and minimum sizes of the molding composition preferably range from about 0.5 mm to about 25 mm, preferably from about 0.5 mm to about 20 mm.

[0528] The shaped products are preferably cylindrical particles or extruded strips.

[0529] In one embodiment, in addition to the precatalyst composition, the molding composition further comprises a lubricant or a binder. In one embodiment, the lubricant or the binder is selected from one or more of the group consisting of sesbania rubber powder, calcium aluminate cement or clay. The binder is preferably sesbania rubber powder.

[0530] In one embodiment, the lubricant or the binder is present in the molding composition in an amount of about 0.1% to about 5% (w / w).

[0531] Precatalyst and catalyst composition

[0532] In another aspect, the present invention relates to a precatalyst composition obtained or obtainable according to the method of the first aspect described in any one of the above embodiments.

[0533] The precatalyst composition obtained or obtainable according to the method of the first aspect is suitable for producing a composition comprising carbon monoxide from a feed gas composition comprising carbon dioxide and hydrogen. The precatalyst composition obtained or obtainable according to the method of the first aspect is particularly suitable for reverse water gas shift reaction.

[0534] The precatalyst composition obtained or obtainable according to the method of the first aspect has favorable nanostructure and component dispersion, and thus has high activity and selectivity in the reverse water gas shift reaction.

[0535] In another aspect, the present invention provides a method for preparing a catalyst composition, the method comprising:

[0536] (a) providing a precatalyst composition obtained or obtainable according to the method of the first aspect described in any one of the above embodiments;

[0537] (b) optionally calcining the precatalyst composition; and

[0538] (c) activating the precatalyst composition to obtain a catalyst composition.

[0539] In another aspect, the present invention relates to a catalyst composition obtained or obtainable by a method according to the above aspect.

[0540] The catalyst composition described in the above aspects is suitable for producing a composition comprising carbon monoxide from a feed gas composition comprising carbon dioxide and hydrogen. The catalyst composition according to the above aspects is particularly suitable for reverse water gas shift reaction.

[0541] The calcination is preferably carried out at a temperature between about 100° C. and about 1000° C., or between about 200° C. and about 700° C., or between about 200° C. and about 600° C., preferably between about 200° C. and about 500° C., more preferably between about 300° C. and about 450° C. The calcination is preferably carried out in air, preferably in static air.

[0542] The calcined precatalyst material of step (b) or the precatalyst composition of step (a) can be activated by reduction, etc. The material to be activated is preferably exposed to a gaseous composition comprising hydrogen at a temperature of about 250°C to about 500°C, more preferably about 300°C to about 350°C.

[0543] In one embodiment, the gaseous composition comprising hydrogen is a mixture of hydrogen and nitrogen. In another embodiment, the gaseous composition is a mixture of carbon dioxide and hydrogen. In one embodiment, the precatalyst activation of (c) is performed in situ in the reaction, i.e., by process gas.

[0544] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, and one or more copper oxides.

[0545] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides; and one or more alkali metals or oxides thereof.

[0546] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, and one or more zinc oxides.

[0547] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides; and one or more alkali metals or oxides thereof.

[0548] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides; and one or more alkaline earth metals or oxides thereof.

[0549] In another aspect, the present invention provides a precatalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more zinc oxides.

[0550] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more zinc oxides; and one or more alkali metals or oxides thereof.

[0551] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more zinc oxides; and one or more alkaline earth metals or oxides thereof.

[0552] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more copper oxides; and one or more alkali metals or oxides thereof.

[0553] In another aspect, the present invention provides a pre-catalyst composition comprising / essentially consisting of / consisting of: one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more copper oxides; and one or more alkaline earth metals or oxides thereof.

[0554] In another aspect, the present invention provides a precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more copper oxides.

[0555] In another aspect, the present invention provides a precatalyst composition consisting essentially of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more copper oxides.

[0556] In another aspect, the present invention provides a precatalyst composition consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more copper oxides.

[0557] In another aspect, the present invention provides a precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, and elemental palladium or one or more oxides thereof.

[0558] In another aspect, the present invention provides a precatalyst composition consisting essentially of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, and elemental palladium or one or more oxides thereof.

[0559] In another aspect, the present invention provides a precatalyst composition consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, and elemental palladium or one or more oxides thereof.

[0560] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more copper oxides, and one or more carbon species.

[0561] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, and one or more carbon species.

[0562] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, one or more alkali metals or oxides thereof, and one or more carbon species.

[0563] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, one or more alkaline earth metals or oxides thereof, and one or more carbon species.

[0564] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides, and one or more carbon species.

[0565] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides, one or more alkali metals or oxides thereof, and one or more carbon species.

[0566] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides, one or more alkaline earth metals or oxides thereof, and one or more carbon species.

[0567] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more zinc oxides, and one or more carbon species.

[0568] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more zinc oxides, one or more alkali metals or oxides thereof, and one or more carbon species.

[0569] In another aspect, the present invention provides a pre-catalyst composition comprising / consisting essentially of / consisting of one or more iron oxides, one or more chromium oxides, one or more manganese oxides, one or more zinc oxides, one or more alkaline earth metals or oxides thereof, and one or more carbon species.

[0570] In another aspect, the present invention provides a precatalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides; calcium or its oxide; and one or more carbon species. The atomic ratio of Fe:Cr is preferably about 10:1, and / or the atomic ratio of Fe:Zr is preferably about 100:1, and / or the atomic ratio of Fe:Ca is preferably about 20:1, and / or the atomic ratio of Fe:Zn is preferably about 42:1.

[0571] In another aspect, the present invention provides a precatalyst composition comprising / consisting essentially of / consisting of: one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more zinc oxides; potassium or its oxides; and one or more carbon species. The atomic ratio of Fe:Cr is preferably about 10:1, and / or the atomic ratio of Fe:Zr is preferably about 100:1, and / or the atomic ratio of Fe:K is preferably about 20:1, and / or the atomic ratio of Fe:Zn is preferably about 42:1.

[0572] In one embodiment, the pre-catalyst composition comprises catalytically active nanoparticles.

[0573] As used herein, the term "nanoparticle" refers to a microscopic particle whose size is usually measured in nanometers (nm). Nanoparticles usually have a particle diameter of 0.5nm to 500nm. For example, nanoparticles can have a particle diameter of about 0.5nm to about 200nm. Nanoparticles preferably have a particle diameter of about 0.5nm to about 100nm, or, for example, a particle diameter of about 1nm to about 50nm. Particles (e.g., nanoparticles) can be spherical or non-spherical. For example, non-spherical particles can be plate-shaped, needle-shaped, or tubular.

[0574] As used herein, the term "particle size" refers to the diameter of a particle if the particle is spherical, or refers to the maximum Feret diameter if the particle is non-spherical.

[0575] In one embodiment, the particle size of the catalytically active particles may be nanometer-sized.

[0576] In one embodiment, the particle size is measured by microscopy, preferably by transmission electron microscopy (TEM).

[0577] In one embodiment, the precatalyst composition comprises catalytically active particles having a particle size of about 100 nm or less. For example, the particle size is about 80 nm or less; or about 70 nm or less; or about 60 nm or less; or about 50 nm or less; or about 40 nm or less; or about 30 nm or less; or about 20 nm or less; or about 10 nm or less.

[0578] In one embodiment, the precatalyst composition comprises a population of catalytically active particles having a particle size of about 5 nm to about 100 nm. For example, the particle size is about 5 nm to about 90 nm; about 5 nm to about 80 nm; or about 5 nm to about 70 nm; or about 5 nm to about 60 nm; or about 5 nm to about 50 nm; or about 5 nm to about 40 nm; or about 5 nm to about 30 nm; or about 5 nm to about 20 nm.

[0579] In one embodiment, the precatalyst composition further comprises a binder or a lubricant. Suitable lubricants and binders are known in the art. In one embodiment, the lubricant or the binder is selected from one or more of sesbania rubber powder, calcium aluminate cement, calcium magnesium oxide (CaMgO2) or clay. The binder is preferably sesbania rubber powder.

[0580] In one embodiment, the lubricant or the binder is present in the pre-catalyst composition in an amount of about 0.1 wt % to about 5 wt %.

[0581] In one embodiment, the precatalyst composition comprises about 50 wt % to about 90 wt % of one or more iron oxides. The precatalyst composition preferably comprises about 60 wt % to about 90 wt % of one or more iron oxides, and preferably comprises about 65 wt % to about 90 wt % of one or more iron oxides.

[0582] In one embodiment, the precatalyst composition comprises about 5 wt % to about 25 wt % of one or more chromium oxides. The precatalyst composition preferably comprises about 5 wt % to about 20 wt % of one or more chromium oxides, and preferably comprises about 5 wt % to about 15 wt % of one or more chromium oxides.

[0583] In one embodiment, the precatalyst composition comprises about 0.5 wt % to about 15 wt % of one or more copper oxides. The precatalyst composition preferably comprises about 1 wt % to about 15 wt % of one or more copper oxides, and preferably comprises about 1 wt % to about 10 wt % of one or more copper oxides.

[0584] In one embodiment, the precatalyst composition comprises about 0.5 wt % to about 10 wt % of one or more zirconium oxides. The precatalyst composition preferably comprises about 1 wt % to about 10 wt % of one or more zirconium oxides, and preferably comprises about 1 wt % to about 5 wt % of one or more zirconium oxides.

[0585] In one embodiment, the precatalyst composition comprises about 0.5 wt % to about 10 wt % of one or more manganese oxides. The precatalyst composition preferably comprises about 1 wt % to about 10 wt % of one or more manganese oxides, and preferably comprises about 1 wt % to about 5 wt % of one or more manganese oxides.

[0586] In one embodiment, the precatalyst composition comprises about 0.5 wt % to about 15 wt % of one or more zinc oxides. The precatalyst composition preferably comprises about 1 wt % to about 15 wt % of one or more zinc oxides, and preferably comprises about 1 wt % to about 10 wt % of one or more zinc oxides.

[0587] In one embodiment, the precatalyst composition comprises from about 60 wt % to about 90 wt % of one or more iron oxides, from about 5 wt % to about 20 wt % of one or more chromium oxides, from about 1 wt % to about 10 wt % of one or more zirconium oxides, and from about 1 wt % to about 15 wt % of one or more copper oxides.

[0588] In another embodiment, the pre-catalyst composition comprises from about 60 wt % to about 90 wt % of one or more iron oxides, from about 5 wt % to about 20 wt % of one or more chromium oxides, from about 1 wt % to about 10 wt % of one or more zirconium oxides, and from about 1 wt % to about 15 wt % of one or more zinc oxides.

[0589] In one embodiment, the pre-catalyst composition comprises from about 60 wt % to about 90 wt % of one or more iron oxides, from about 5 wt % to about 20 wt % of one or more chromium oxides, from about 1 wt % to about 10 wt % of one or more manganese oxides, and from about 1 wt % to about 15 wt % of one or more copper oxides.

[0590] In another embodiment, the pre-catalyst composition consists essentially of about 60 wt % to about 90 wt % of one or more iron oxides, about 5 wt % to about 20 wt % of one or more chromium oxides, about 1 wt % to about 10 wt % of one or more manganese oxides, and about 1 wt % to about 15 wt % of one or more copper oxides.

[0591] In another embodiment, the pre-catalyst composition consists of about 60 wt % to about 90 wt % of one or more iron oxides, about 5 wt % to about 20 wt % of one or more chromium oxides, about 1 wt % to about 10 wt % of one or more manganese oxides, and about 1 wt % to about 15 wt % of one or more copper oxides.

[0592] In one embodiment, the precatalyst composition comprises from about 0.01 wt % to about 5 wt % of elemental palladium or one or more oxides thereof. The precatalyst composition preferably comprises from about 0.05 wt % to about 5 wt % of elemental palladium or one or more oxides thereof, preferably comprises from about 0.05 wt % to about 4 wt % of elemental palladium or one or more oxides thereof, preferably comprises from about 0.05 wt % to about 3 wt % of elemental palladium or one or more oxides thereof, preferably comprises from about 0.05 wt % to about 2 wt % of elemental palladium or one or more oxides thereof, preferably comprises from about 0.05 wt % to about 1 wt % of elemental palladium or one or more oxides thereof,

[0593] In one embodiment, the pre-catalyst composition comprises from about 60 wt % to about 90 wt % of one or more iron oxides, from about 5 wt % to about 20 wt % of one or more chromium oxides, from about 1 wt % to about 10 wt % of one or more zirconium oxides, from about 1 wt % to about 15 wt % of one or more copper oxides, and from about 0.01 wt % to about 4 wt % of elemental palladium or one or more oxides thereof.

[0594] In one embodiment, the pre-catalyst composition consists essentially of about 60 wt % to about 90 wt % of one or more iron oxides, about 5 wt % to about 20 wt % of one or more chromium oxides, about 1 wt % to about 10 wt % of one or more zirconium oxides, about 1 wt % to about 15 wt % of one or more copper oxides, and about 0.01 wt % to about 4 wt % of elemental palladium or one or more oxides thereof.

[0595] In one embodiment, the pre-catalyst composition consists of about 60 wt % to about 90 wt % of one or more iron oxides, about 5 wt % to about 20 wt % of one or more chromium oxides, about 1 wt % to about 10 wt % of one or more zirconium oxides, about 1 wt % to about 15 wt % of one or more copper oxides, and about 0.01 wt % to about 4 wt % of elemental palladium or one or more oxides thereof.

[0596] In one embodiment, the precatalyst composition has at least about 20 m 2 / g, preferably at least about 50m 2 The BET surface area can be measured according to techniques known in the art. For example, the BET surface area can be determined by the equilibrium adsorption and desorption isotherms of nitrogen at -196°C.

[0597] In embodiments, the BET surface area of ​​the precatalyst composition is at least about 60 m 2 / g. For example, the precatalyst composition may have at least about 70 m 2 / g BET surface area. For example, the precatalyst composition can have at least about 80 m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​at least about 90 m 2 For example, the precatalyst composition may have a BET surface area of ​​at least 100 m 2 / g of BET surface area.

[0598] In one embodiment, the precatalyst composition has about 5 m 2 / g to about 1000m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 5 m 2 / g to about 500m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 5 m 2 / g to about 300m 2 / g of BET surface area.

[0599] In one embodiment, the precatalyst composition has about 20 m 2 / g to about 1000m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 20 m 2 / g to about 500m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 20 m 2 / g to about 300m 2 / g of BET surface area.

[0600] In another embodiment, the precatalyst composition has about 50 m 2 / g to about 1000m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 50 m 2 / g to about 500m 2 / g BET surface area. For example, the precatalyst composition may have a BET surface area of ​​about 50 m 2 / g to about 300m 2 / g of BET surface area.

[0601] The precatalyst composition is preferably used to produce a composition comprising carbon monoxide from a feed gas composition comprising carbon dioxide and hydrogen. The precatalyst composition is preferably used in a reverse water gas shift reaction. Other suitable methods in which the precatalyst composition can be used are described below.

[0602] Process for producing a composition comprising carbon monoxide

[0603] In another aspect, the present invention relates to a method for producing a composition comprising carbon monoxide, wherein the method comprises contacting a feed gas composition comprising carbon dioxide and hydrogen with a precatalyst composition or a catalyst composition as described in any one of the above embodiments at a temperature of at least 400°C.

[0604] In one embodiment, the method of producing a composition comprising carbon monoxide comprises providing a pre-catalyst composition by performing the above method. In another embodiment, the method of producing a composition comprising carbon monoxide comprises providing a catalyst composition by performing the above method.

[0605] In one embodiment of the claimed method, the catalyst composition or the precatalyst composition is charged to the reaction zone. The catalyst has been activated ex situ (e.g., by heating, and / or, if desired, by optional oxidation and subsequent reduction, e.g., with hydrogen). Alternatively, if the precatalyst composition is activated in situ (e.g., under reaction conditions), it can be used directly in the reaction.

[0606] The catalyst can be used in a fixed bed, a moving bed or a fluidized bed. The catalyst is preferably used in a fixed bed reactor. In one embodiment, the precatalyst composition or the catalyst composition is filled in a fixed bed reactor, and the feed gas composition is fed through the bed. In some embodiments, the feed gas composition is continuously fed above the precatalyst composition or the catalyst composition.

[0607] In one embodiment, the feed gas composition comprising carbon dioxide and hydrogen with an appropriate H2:CO2 molar ratio is contacted with a catalyst composition or a pre-catalyst composition bed and reacted under reaction conditions. Typically, the molar ratio of H2:CO2 ranges from about 1:1 to about 10:1, preferably from about 1:1 to about 5:1, more preferably from about 1:1 to about 4:1, more preferably from about 1:1 to about 3:1, and preferably from about 1:1 to about 2:1.

[0608] In one embodiment, the feed gas composition is substantially free of oxygen and / or water. In another embodiment, the feed gas composition is free of oxygen and / or water.

[0609] In another embodiment, the molar ratio of H2:CO2 in the feed gas composition is about 1:1, or about 2:1, or about 3:1, or about 4:1.

[0610] The reaction temperature is increased. As used herein, the increased temperature refers to a temperature that is increased relative to standard ambient temperature (i.e., a temperature of 298.15K (25°C)). In one embodiment, the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a temperature of at least 400°C, preferably at least about 450°C, preferably at least about 500°C, preferably at least about 550°C, preferably at least about 600°C, preferably at least about 650°C.

[0611] In another embodiment, the feed gas composition is contacted with the pre-catalyst composition or the catalyst composition at a temperature of about 400°C to about 1000°C, or about 400°C to about 900°C, or about 400°C to about 800°C, or about 400°C to about 700°C, or about 400°C to about 650°C, or about 400°C to about 600°C, or about 400°C to about 550°C.

[0612] In another embodiment, the feed gas composition is contacted with the pre-catalyst composition or the catalyst composition at a temperature of about 450°C to about 1000°C, or about 450°C to about 900°C, or about 450°C to about 800°C, or about 450°C to about 700°C, or about 450°C to about 650°C, or about 450°C to about 600°C.

[0613] In another embodiment, the feed gas composition is contacted with the pre-catalyst composition or the catalyst composition at a temperature of about 500°C to about 1000°C, or about 500°C to about 900°C, or about 500°C to about 800°C, or about 500°C to about 650°C, or about 500°C to about 600°C.

[0614] In another embodiment, the feed gas composition is contacted with the pre-catalyst composition or the catalyst composition at a temperature of about 600°C to about 1000°C, or about 600°C to about 900°C, or about 600°C to about 800°C, or about 600°C to about 700°C, or about 600°C to about 650°C.

[0615] In another embodiment, the feed gas composition contacts the pre-catalyst composition or the catalyst composition at a temperature of about 700°C to about 1000°C, or about 700°C to about 900°C, or about 700°C to about 800°C, or about 700°C to about 750°C.

[0616] The reaction pressure may be lower than atmospheric pressure, atmospheric pressure or elevated pressure. In one embodiment, the reaction pressure may be atmospheric pressure or elevated pressure. As used herein, elevated pressure refers to a pressure elevated relative to standard ambient pressure (i.e., the pressure of 100,000Pa (1 bar, 14.5psi, 0.9869atm)). In one embodiment, the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a pressure of about 100KPa to about 2000KPa, or about 100KPa to about 500KPa, preferably about 100KPa to about 400KPa, preferably about 100KPa to about 300KPa, preferably about 100KPa to about 200KPa, and preferably about 100KPa to about 150KPa.

[0617] In another embodiment, the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a pressure of about 0 KPa to about 2000 KPa, or about 0 KPa to about 500 KPa, preferably about 0 KPa to about 400 KPa, preferably about 0 KPa to about 300 KPa, preferably about 0 KPa to about 200 KPa, and preferably about 0 KPa to about 150 KPa.

[0618] In another embodiment, the feed gas composition is contacted with the pre-catalyst composition or the catalyst composition at a pressure of about 0 KPa to about 100 KPa, or about 0 KPa to about 50 KPa.

[0619] In one embodiment, the feed gas composition is about 1h -1 To about 20,000h -1 , preferably about 1000h -1To about 10000h -1 , preferably about 1000h -1 To about 8000h -1 , preferably about 1000h -1 To about 7000h -1 , preferably about 1000h -1 To about 5000h -1 The catalyst composition is contacted with the precatalyst composition or the catalyst composition at a gas hourly space velocity (GHSV) of

[0620] In one embodiment, the process provides a methane selectivity of about 2% or less, more preferably about 1.8% or less, more preferably about 1.5% or less, more preferably about 1.0% or less, more preferably about 0.6% or less, more preferably about 0.5% or less, more preferably about 0.4% or less, more preferably about 0.3% or less, more preferably about 0.2% or less, more preferably about 0.1% or less, more preferably about 0.05% or less, more preferably about 0.01 vol. % or less.

[0621] Methane selectivity refers to the ratio of methane production to converted CO2. CH4 %) can be calculated according to the following formula:

[0622] S CH4 % = Y CH4 out / (Y CO2in -Y CO2out )

[0623] Among them, Yco2 in refers to the amount of CO2 in the feed gas composition (ml / min), Y CO2 out and Y CH4 out They refer to the amount of CO2 and CH4 in the product stream, respectively.

[0624] In one embodiment, the method provides a carbon dioxide conversion of at least about 40%, at least about 50%, preferably at least about 55%, preferably at least about 60%, preferably at least about 65%.

[0625] In another embodiment, the method provides a carbon dioxide conversion of about 50% to about 65%, preferably about 55% to about 65%, preferably about 60% to about 65%.

[0626] The carbon dioxide conversion rate (Xco2%) can be calculated according to the following formula:

[0627] Xco2%=1-((Y CO2 out ) / (Y CO2in ))

[0628] Among them, Yco2 in refers to the amount of CO2 in the feed gas composition (ml / min), Y CO2 out Refers to the amount of CO2 in the product stream (ml / min).

[0629] In one embodiment, the process provides a carbon monoxide selectivity of at least about 80%, preferably at least about 90%, preferably at least about 95%, preferably at least about 96%, preferably at least about 98%, preferably at least about 99%, preferably at least about 99.5%, preferably at least about 99.9%.

[0630] In one embodiment, the process provides a carbon monoxide selectivity of about 90% to 100%, preferably about 95% to 100%, preferably about 96% to 100%, preferably about 98% to 100%.

[0631] Carbon monoxide selectivity refers to the ratio of carbon monoxide production to converted CO2. The carbon monoxide selectivity (Sco%) can be calculated according to the following formula:

[0632] S CO % = Y CO out / (Y CO2 in -Y CO2 out )

[0633] Among them, Yco2 in refers to the amount of CO2 in the feed gas composition (ml / min), Y CO2 out and Y CO out They refer to the amount of CO2 and CO in the product stream, respectively.

[0634] In one embodiment, the process provides a carbon dioxide conversion of about 50% to about 65%, a carbon monoxide selectivity of about 90% to 100%, and a methane selectivity of about 1.8% or less.

[0635] In one embodiment, the process provides a carbon dioxide conversion of about 55% to about 65%, a carbon monoxide selectivity of about 95% to 100%, and a methane selectivity of about 1.8% or less.

[0636] In another embodiment, the process provides a carbon dioxide conversion of about 55% to about 65%, a carbon monoxide selectivity of about 95% to 100%, and a methane selectivity of about 0.6% or less.

[0637] In another embodiment, the process provides a carbon dioxide conversion of about 55% to about 65%, a carbon monoxide selectivity of about 98% to 100%, and a methane selectivity of about 0.01% or less.

[0638] In another embodiment, the process provides a carbon dioxide conversion of about 60% to about 65%, a carbon monoxide selectivity of about 98% to 100%, and a methane selectivity of about 0.01% or less.

[0639] In another embodiment, the process provides a carbon dioxide conversion of about 60% to about 65%, and a carbon monoxide selectivity of about 98% or more.

[0640] In another embodiment, the process provides a carbon dioxide conversion of about 60% to about 65%, and a carbon monoxide selectivity of about 99% or more.

[0641] In another embodiment, the process provides a carbon dioxide conversion of about 60% to about 65%, a carbon monoxide selectivity of about 99% or more, and a methane selectivity of about 0.6% or less.

[0642] The method of producing a composition comprising carbon monoxide may comprise, as a preliminary step, preparing a pre-catalyst composition or a catalyst composition as described above.

[0643] The present invention will now be further described by the following numbered paragraphs, which are not claims.

[0644] 1. A method for preparing a precatalyst composition, the method comprising:

[0645] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0646] Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof are combined;

[0647] Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate;

[0648] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

[0649] 2. A method for preparing a precatalyst composition according to paragraph 1, comprising:

[0650] (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0651] one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof; and

[0652] (ii) calcining the material of (i) to obtain a precatalyst composition.

[0653] 3. A method for preparing a precatalyst composition according to paragraph 1 or 2, comprising:

[0654] (i)(a) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and

[0655] One or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof; and

[0656] Water binding;

[0657] (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance;

[0658] (ii) calcining the material of (i)(b) to obtain a precatalyst composition.

[0659] 4. The method according to any of the preceding paragraphs, wherein the iron species is an iron salt or a hydrate thereof.

[0660] 5. The method according to any one of the preceding paragraphs, wherein the transition metal species is selected from two or more of the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof and nickel salts or hydrates thereof.

[0661] 6. The method according to any one of the preceding paragraphs, wherein the transition metal species is selected from one or more of the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, and a zinc salt or a hydrate thereof.

[0662] 7. The method according to any one of the preceding paragraphs, wherein the transition metal species is selected from two or more of the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, and a zinc salt or a hydrate thereof.

[0663] 8. A method according to any one of the preceding paragraphs, wherein the transition metal species is selected from one or more of a manganese salt or a hydrate thereof or a zirconium salt or a hydrate thereof; and one or more of a copper salt or a hydrate thereof or a zinc salt or a hydrate thereof.

[0664] 9. The method according to any one of the preceding paragraphs, wherein the transition metal species is selected from:

[0665] (i) a copper salt or a hydrate thereof and a manganese salt or a hydrate thereof; or

[0666] (ii) a zinc salt or a hydrate thereof and a manganese salt or a hydrate thereof; or

[0667] (iii) a copper salt or a hydrate thereof and a zirconium salt or a hydrate thereof; or

[0668] (iv) a zinc salt or a hydrate thereof and a zirconium salt or a hydrate thereof.

[0669] 10. The method according to any of the preceding paragraphs, wherein step (i) further comprises: combining one or more of an alkali metal species, an alkaline earth metal species, and a rare earth metal species.

[0670] 11. The method according to paragraph 10, wherein the alkali metal species, the alkaline earth metal species or the rare earth metal species is added in step (i) in the form of a salt or a hydrate thereof.

[0671] 12. The method according to paragraph 10 or 11, wherein the alkali metal species is selected from one or more of potassium nitrate, potassium carbonate, sodium nitrate, sodium carbonate, lithium carbonate and cesium carbonate or a hydrate thereof.

[0672] 13. The method of any one of paragraphs 10 to 12, wherein the atomic ratio of iron to alkali metal in step (i) is from about 100:1 to about 5:1.

[0673] 14. A method for preparing a precatalyst composition, the method comprising:

[0674] (i) an iron salt or a hydrate thereof; a chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; and

[0675] Optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, and a copper salt or a hydrate thereof are combined;

[0676] Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate;

[0677] (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

[0678] 15. The method according to any one of the preceding paragraphs, wherein in step (i), the iron salt or its hydrate is an iron (II) or iron (III) salt or its hydrate.

[0679] 16. A method according to any one of the preceding paragraphs, wherein the iron salt or its hydrate of step (i) is selected from one or more of the group consisting of FeCl2, Fe(OAc)2, FeSO4, Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrate.

[0680] 17. A method according to any one of the preceding paragraphs, wherein the iron salt or its hydrate in step (i) is one or more of Fe(NO3)2 and Fe(NO3)3 or their hydrates.

[0681] 18. The method according to any one of the preceding paragraphs, wherein the chromium salt or hydrate thereof is a chromium (III) salt or hydrate thereof.

[0682] 19. A method according to any one of the preceding paragraphs, wherein the chromium salt or its hydrate is selected from one or more of the group consisting of Cr(NO3)3, CrCl3, Cr(Ac)3 and Cr(OH)3 or its hydrate.

[0683] 20. A method according to any one of the preceding paragraphs, wherein the chromium salt or a hydrate thereof is Cr(NO3)3 or a hydrate thereof.

[0684] 21. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the chromium salt is such that the atomic ratio of iron to chromium is from about 100:1 to about 5:4.

[0685] 22. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the chromium salt is such that the atomic ratio of iron to chromium is from about 20:1 to about 5:4.

[0686] 23. A method according to any one of the preceding paragraphs, wherein step (i) comprises combining a manganese salt or a hydrate thereof with an iron chromium salt or a hydrate thereof.

[0687] 24. A method according to any one of the preceding paragraphs, wherein step (i) comprises combining a manganese salt or a hydrate thereof and a copper salt or a hydrate thereof with an iron chromium salt or a hydrate thereof.

[0688] 25. A method according to any one of the preceding paragraphs, wherein step (i) comprises: combining an iron (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; an organic compound comprising one or more functional groups selected from carboxyl, hydroxyl, amido and amino groups; a copper (II) salt or a hydrate thereof; and a manganese (II) salt or a hydrate thereof.

[0689] 26. A method according to any one of the preceding paragraphs, wherein step (i) comprises combining a manganese salt or hydrate thereof and a zinc salt or hydrate thereof with an iron chromium salt or hydrate thereof.

[0690] 27. A method according to any one of the preceding paragraphs, wherein the manganese salt or its hydrate is selected from one or more of Mn(NO3)2, MnSO4, MnCl2, Mn(OAc)2 and manganese citrate or its hydrate.

[0691] 28. A method according to any one of the preceding paragraphs, wherein the manganese salt or a hydrate thereof is Mn(NO3)2 or a hydrate thereof.

[0692] 29. The method according to any of the preceding paragraphs, wherein the ratio of the iron salt to the manganese salt is such that the atomic ratio of iron to manganese is from about 250: 1 to about 10: 1. The atomic ratio of iron to manganese is preferably from about 250: 1 to about 50: 1, preferably from about 250: 1 to about 75: 1.

[0693] 30. The method according to any of the preceding paragraphs, wherein step (i) comprises combining a zirconium salt or a hydrate thereof with an iron chromium salt or a hydrate thereof.

[0694] 31. The method according to any one of the preceding paragraphs, wherein the zirconium salt or hydrate thereof is a zirconium (III) or (IV) salt or hydrate thereof, preferably a zirconium (IV) salt or hydrate thereof.

[0695] 32. A method according to any one of the preceding paragraphs, wherein step (i) comprises combining a copper salt or a hydrate thereof with an iron chromium salt or a hydrate thereof.

[0696] 33. The method according to any one of the preceding paragraphs, wherein the copper salt or its hydrate is a copper (I) or (II) salt or its hydrate, preferably a copper (II) salt or its hydrate.

[0697] 34. The method of any of the preceding paragraphs, wherein step (i) comprises combining a zinc salt or a hydrate thereof with an iron chromium salt or a hydrate thereof.

[0698] 35. A method according to any one of the preceding paragraphs, wherein the zinc salt or its hydrate is a zinc (II) salt or its hydrate, preferably selected from Zn(NO3)2, Zn(OAc)2, ZnCl2 and ZnSO4 or its hydrate.

[0699] 36. The method according to any one of the preceding paragraphs, wherein the organic compound comprises two or more functional groups selected from carboxyl, hydroxyl, amido and amino.

[0700] 37. The method according to any one of the preceding paragraphs, wherein the organic compound is C4 to C 12 Carboxylic acid or urea.

[0701] 38. A method according to any of the preceding paragraphs, wherein the organic compound is selected from citric acid, tartaric acid, oxalic acid, urea, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) or a salt thereof.

[0702] 39. The method of any of the preceding paragraphs, wherein the organic compound is citric acid or urea.

[0703] 40. The method according to any of the preceding paragraphs, wherein the molar ratio of organic compound to metal in step (i) is from about 0.4:1 to about 10:1.

[0704] 41. The method according to any of the preceding paragraphs, wherein the molar ratio of organic compound to metal in step (i) is from about 1:1 to about 10:1.

[0705] 42. The method according to any one of paragraphs 1 and 14 to 41, wherein the method comprises step (ii).

[0706] 43. The method according to any one of paragraphs 1 and 14 to 42, wherein in step (ii), the iron salt or its hydrate is an iron (II) or iron (III) salt or its hydrate.

[0707] 44. A method according to any one of paragraphs 1 and 14 to 43, wherein the iron salt or its hydrate of step (ii) is selected from one or more of the group consisting of FeCl2, Fe(OAc)2, FeSO4, Fe(NO3)2, Fe(NO3)3, FeCl3 and Fe2(SO4)3 or its hydrates.

[0708] 45. The method according to any one of paragraphs 1 and 14 to 44, wherein the iron salt or hydrate of step (ii) is selected from one or more of the group consisting of Fe(NO3)2 and Fe(NO3)3 or their hydrates.

[0709] 46. ​​The method of any one of paragraphs 1 and 14 to 45, wherein step (ii) consists essentially of combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution to obtain a precipitate.

[0710] 47. The method according to any one of paragraphs 1 and 14 to 45, wherein step (ii) comprises: combining a zirconium salt or a hydrate thereof, preferably a zirconium (IV) salt or a hydrate thereof, with the iron salt or a hydrate thereof.

[0711] 48. A method according to any one of paragraphs 1 and 14 to 45, wherein step (ii) comprises combining a copper salt or a hydrate thereof, preferably a copper (II) salt or a hydrate thereof, with the iron salt or a hydrate thereof.

[0712] 49. A method according to any of the preceding paragraphs, wherein the zirconium salt or its hydrate is selected from one or more of the group consisting of Zr(NO3)4, ZrO(NO3)2, ZrOCl2, zirconium acetate or its hydrate.

[0713] 50. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 250:1 to about 10:1.

[0714] 51. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the zirconium salt is such that the atomic ratio of iron to zirconium is from about 100:1 to about 50:1.

[0715] 52. A method according to any one of the preceding paragraphs, wherein the copper salt or its hydrate is selected from one or more of the group consisting of Cu(NO3)2, Cu(OAc)2, CuCl2, CuSO4, Cu2CO3(OH)2, CuCl, Cu2SO4 and CuNO3 or its hydrate.

[0716] 53. A method according to any one of the preceding paragraphs, wherein the copper salt or its hydrate is selected from one or more of the group consisting of Cu(NO3)2 and Cu2CO3(OH)2 or its hydrate.

[0717] 54. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 250:1 to about 10:1.

[0718] 55. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the copper salt is such that the atomic ratio of iron to copper is from about 100:1 to about 50:1.

[0719] 56. The method of any of the preceding paragraphs, wherein the ratio of the iron salt to the zinc salt is such that the atomic ratio of iron to copper is from about 100:1 to about 50:1.

[0720] 57. The method according to any one of paragraphs 1 and 14 to 56, wherein the alkaline aqueous solution is selected from aqueous ammonia, aqueous urea solution, aqueous hydroxide solution such as aqueous NaOH or KOH solution, aqueous carbonate solution such as sodium carbonate.

[0721] 58. The method of any one of paragraphs 1 and 14 to 57, wherein the alkaline solution is added in step (ii) until the pH of the combination is about 7 to about 14.

[0722] 59. The process of any one of paragraphs 1 and 14 to 58, wherein step (ii) is performed at a temperature in the range of about 20°C to about 90°C.

[0723] 56. The method of any of paragraphs 1 and 14 to 59, wherein step (iii) comprises combining the product of step (i) and the product of step (ii) by mixing or grinding to form a paste or powder.

[0724] 57. The method according to any of the preceding paragraphs, wherein the calcining is carried out at a temperature between about 400°C and about 1000°C, preferably between about 500°C and about 700°C.

[0725] 58. The method according to any one of the preceding paragraphs, wherein in step (iii), the combination is calcined for about 1 hour to 24 hours, preferably for about 2 hours to about 10 hours.

[0726] 59. The method according to any of the preceding paragraphs, wherein the method further comprises:

[0727] (iv) treating the precatalyst composition of step (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the treated precatalyst composition.

[0728] 60. The method of paragraph 59, wherein the transition metal solution comprising one or more transition metal salts or hydrates thereof is an aqueous solution.

[0729] 61. The method of paragraph 59 or 60, wherein the transition metal solution comprises one or more transition metal salts or hydrates thereof selected from Pd, Pt, Ru, Rh, Au and Cu salts or hydrates thereof.

[0730] 62. The method of any one of paragraphs 59 to 61, wherein the transition metal salt solution comprises a palladium salt or a hydrate thereof.

[0731] 63. The method of any one of paragraphs 59 to 62, wherein the transition metal salt solution consists of one or more palladium salts or hydrates thereof.

[0732] 64. The method of any one of paragraphs 59 to 63, wherein the palladium salt or a hydrate thereof is a palladium (II) salt or a hydrate thereof.

[0733] 65. The method according to paragraph 64, wherein the palladium (II) salt or its hydrate is selected from one or more of the group consisting of PdCl2, Pd (OAc)2 and Pd (NO3)2 or its hydrate.

[0734] 66. The process of any of paragraphs 59 to 65, wherein in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal in the precatalyst composition is from about 250:1 to about 10:1.

[0735] 67. The process of any of paragraphs 59 to 65, wherein in step (iv), the ratio of the transition metal salt is such that the atomic ratio of iron to transition metal in the precatalyst composition is from about 100:1 to about 50:1.

[0736] 68. The method of any one of paragraphs 59 to 67, wherein in step (iv), the transition metal salt is not a Co, Pt, Ni or Ru salt or a hydrate thereof.

[0737] 69. The method according to any one of paragraphs 59 to 68, wherein in step (iv), the calcining is carried out at a temperature between about 100°C and about 1000°C, preferably at a temperature between about 500°C and about 700°C.

[0738] 70. The method according to any one of the preceding paragraphs, wherein the product of step (iii) and / or step (iv) is formed into pre-catalyst units such as granules or tablets.

[0739] 71. A process according to any one of the preceding paragraphs, wherein the product of step (iii) and / or step (iv) is mixed with a lubricant or binder before being formed into a pre-catalyst unit.

[0740] 72. The method according to paragraph 70 or 71, wherein the lubricant or the binder is selected from one or more of the group consisting of sesbania rubber powder, calcium aluminate cement or clay.

[0741] 73. The method according to any one of paragraphs 70 to 72, wherein the lubricant or the binder is added to the product of step (iii) and / or step (iv) in an amount of about 0.1% to about 5% (w / w).

[0742] 74. A precatalyst composition obtained or obtainable according to the method of any one of paragraphs 1 to 73.

[0743] 75. A precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, one or more copper oxides, and elemental palladium or one or more oxides thereof.

[0744] 76. A precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more copper oxides.

[0745] 77. A precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, and one or more zinc oxides.

[0746] 78. A precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more zirconium oxides, and one or more copper oxides.

[0747] 79. A precatalyst composition comprising one or more iron oxides, one or more chromium oxides, one or more manganese oxides, and one or more zinc oxides.

[0748] 80. The precatalyst composition of any of paragraphs 75 to 79, further comprising one or more of an alkali metal, an alkaline earth metal, and a rare earth metal or an oxide thereof.

[0749] 81. The precatalyst composition of any of paragraphs 75 to 80, further comprising a binder or lubricant.

[0750] 82. The precatalyst composition according to paragraph 81, wherein the lubricant or the binder is selected from one or more of the group consisting of sesbania rubber powder, calcium aluminate cement, calcium magnesium oxide (CaMgO2) or clay.

[0751] 83. The precatalyst composition of paragraph 81 or 82, wherein the lubricant or the binder is present in the precatalyst composition in an amount of about 0.1 wt% to about 5 wt%.

[0752] 84. The precatalyst composition of any of paragraphs 75 to 83, wherein the precatalyst composition comprises from about 50 wt% to about 90 wt% of one or more iron oxides.

[0753] 85. The precatalyst composition of any of paragraphs 75 to 84, wherein the precatalyst composition comprises from about 5 wt% to about 25 wt% of one or more chromium oxides.

[0754] 86. The procatalyst composition of any of paragraphs 75 to 85, wherein the procatalyst composition comprises from about 0.5 wt% to about 15 wt% of one or more copper oxides.

[0755] 87. The precatalyst composition of any of paragraphs 75 to 86, wherein the precatalyst composition comprises from about 0.5 wt% to about 10 wt% of one or more zirconium oxides.

[0756] 88. The procatalyst composition of any of paragraphs 75 to 87, wherein the procatalyst composition comprises from about 0.5 wt % to about 15 wt % of one or more zinc oxides.

[0757] 89. The procatalyst composition of any of paragraphs 75 to 88, wherein the procatalyst composition comprises from about 0.01 wt% to about 5 wt% elemental palladium or one or more oxides thereof.

[0758] 90. A precatalyst composition comprising 60 wt % to 90 wt % of one or more iron oxides, 5 wt % to 20 wt % of one or more chromium oxides, 1 wt % to 10 wt % of one or more zirconium oxides, 1 wt % to 15 wt % of one or more copper oxides, and 0.01 wt % to 4 wt % of elemental palladium or one or more oxides thereof.

[0759] 91. A precatalyst composition according to paragraph 90, comprising from about 60 wt % to about 90 wt % of one or more iron oxides, from about 5 wt % to about 20 wt % of one or more chromium oxides, from about 1 wt % to about 10 wt % of one or more manganese oxides, and from about 1 wt % to about 15 wt % of one or more copper oxides.

[0760] 92. The procatalyst composition of any of paragraphs 75 to 88, comprising potassium or an oxide thereof or calcium or an oxide thereof, and one or more carbon species.

[0761] 93. The procatalyst composition of any of paragraphs 75 to 92, suitable for producing a composition comprising carbon monoxide from a feed gas composition comprising carbon dioxide and hydrogen.

[0762] 94. The precatalyst composition of any of paragraphs 75 to 93, wherein the precatalyst composition is suitable for use in a reverse water gas shift reaction.

[0763] 95. A method for preparing a catalyst composition, the method comprising:

[0764] (a) providing a precatalyst composition according to any one of paragraphs 74 or 75 to 94;

[0765] (b) optionally calcining the precatalyst composition; and

[0766] (c) activating the precatalyst composition to obtain a catalyst composition.

[0767] 96. The method of paragraph 95, wherein the calcining is carried out at a temperature between about 100°C and about 1000°C, preferably between about 200°C and about 500°C.

[0768] 97. The method of paragraph 95 or 96, wherein step (c) further comprises: grinding or milling the calcined precatalyst composition to reduce particle size prior to activation.

[0769] 98. The method according to any one of paragraphs 95 to 97, wherein in step (c), the precatalyst composition to be activated is exposed to a gaseous composition comprising hydrogen at a temperature of about 250°C to about 500°C.

[0770] 99. A catalyst composition obtained or obtainable according to the methods of paragraphs 95 to 98.

[0771] 100. A method for producing a composition comprising carbon monoxide, wherein the method comprises contacting a feed gas composition comprising carbon dioxide and hydrogen at a temperature of at least 400°C, preferably at a temperature of about 600°C, with a precatalyst composition according to any one of paragraphs 74 or 75 to 94 or a catalyst composition according to paragraph 99.

[0772] 101. The method of paragraph 100, wherein the molar ratio of H2:CO2 in the feed gas composition is from about 1:1 to about 10:1.

[0773] 102. The method of paragraph 101, wherein the molar ratio of H2:CO2 in the feed gas composition is from about 1:1 to about 4:1.

[0774] 103. The process of any of paragraphs 100 to 102, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a temperature of at least 500°C.

[0775] 104. The process of any of paragraphs 100 to 102, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a temperature of about 400°C to about 1000°C.

[0776] 105. The process of any of paragraphs 100 to 102, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a temperature of about 450°C to about 600°C.

[0777] 106. The process according to any of paragraphs 101 to 105, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a pressure of about 100 KPa to about 500 KPa.

[0778] 107. The method according to any one of paragraphs 101 to 106, wherein the feed gas composition is about 1 hour -1 To about 20,000h -1 , preferably about 1000h -1 To about 5000h -1 The catalyst composition is contacted with the precatalyst composition or the catalyst composition at a gas hourly space velocity (GHSV) of

[0779] 108. The process of any of paragraphs 101 to 107, wherein the process provides a methane selectivity of about 2% or less.

[0780] 109. The process of any of paragraphs 101 to 108, wherein the process provides a methane selectivity of about 0.6% or less.

[0781] 110. The process of any of paragraphs 101 to 109, wherein the process provides a carbon dioxide conversion of at least about 55%.

[0782] 111. The method of any of paragraphs 101 to 110, wherein the method provides a carbon dioxide conversion rate of at least about 60%.

[0783] 112. The process of any of paragraphs 101 to 111, wherein the process provides a carbon monoxide selectivity of at least about 98%.

[0784] Example

[0785] I. Preparation of Precatalyst Composition

[0786] The precatalyst composition is prepared by an organic combustion method, optionally combined with a precipitation method and / or an impregnation method.

[0787] IA Example 1

[0788] For example, in the first step, the following compounds are combined as follows:

[0789]

[0790] Fe(NO3)3.9H2O (Iron(III) nitrate nonahydrate), Cr(NO3)3.4H2O (Chromium(III) nitrate hydrate), ZrO(NO3)2.xH2O (Zirconium(IV) nitrate hydrate), Cu(NO3)2.4H2O (Copper nitrate hydrate) and citric acid were mixed in the above amounts and ground in a pestle and mortar at ambient conditions for 1 hour until a nearly dry paste was formed.

[0791] In the second step, 50.5 g of Fe(NO3)3.9H2O was added to 500 ml of water while stirring at 50° C. to 90° C. for 3 hours. Subsequently, an aqueous ammonia (NH3.H2O) solution (25 wt%) was added dropwise to adjust the pH to 11. A precipitate was formed, and the resulting slurry was aged at 50° C. to 80° C. for 10 hours while constantly stirring until the volume of the solution was reduced to less than about 100 ml and a sludge was produced.

[0792] In the third step, the sludge produced in the second step was gradually added to the paste produced in the first step while constantly mixing at a temperature of about 50°C to 80°C for up to 10 hours to obtain a viscous solid mixture that was solid when cooled to room temperature. The solid was then transferred to a crucible and placed in a muffle furnace (Carbolite laboratory muffle furnace, maximum temperature 1100°C), and the temperature was gradually increased from room temperature to 600°C at a rate of 2°C / min, and after heating at 600°C for 5 hours, it was cooled to room temperature overnight in the muffle furnace. A brown-red powder (precatalyst A) was obtained.

[0793] A portion of the calcined brown-red powder was combined with 1.8 wt% of sesbania rubber powder and milled (using a Xuman mill at 34,000 revolutions per minute) for 2 hours at ambient conditions and then extruded (using a Beiyang Lixing extruder 0041) to obtain a pre-catalyst composition in the form of cylindrical particles.

[0794] IB Example 2

[0795] In the fourth step, precatalyst A (10 g, dry powder) was treated with 5 ml of 0.05% PdCl2 solution (Aladdin Chemical), left in air for 4 hours under ambient conditions, dried at 100°C for 3 hours, and then calcined at 600°C for 2 hours in a muffle furnace (SGM.M10 / 13, Luoyang Sigma Instrument Manufacturing Co., Ltd.), and then cooled. The cooled calcined product was washed with water to remove chloride ions, then dried and calcined at 600°C, and then cooled to room temperature to obtain powdered precatalyst B. The powder was manually pressed into granules using a manual powder tablet press (769YP-15A).

[0796] IC Example 3

[0797] In another example, the first step is to combine the following components:

[0798]

[0799] Similar to the method described in Example 1 above, the components were mixed and ground in a pestle and mortar at ambient conditions for 1 hour until a nearly dry paste was formed.

[0800] A precipitate was prepared from the iron salts and base as described in the second step of Example 1 and the resulting sludge was added to the dry paste of the first step.

[0801] The combination was dried at about 100°C for 4 hours, and then the viscous sludge was transferred to a quartz crucible, heated to 600°C at a rate of 2°C / min, and kept in a muffle furnace (Carbolite laboratory muffle furnace, maximum temperature 1100°C) for 4 hours to obtain a brown-red powder (precatalyst C).

[0802] The catalyst was mixed with sesbania rubber powder (1.2%) and then pressed into granules using a manual powder tablet press (769YP-15A).

[0803] ID Example 4

[0804] In the first step, the same materials as precatalyst C (Example 3) (Fe(NO3)3.9H2O (171.7 g), Cr(NO3)3.xH2O (23.7 g), Mn(NO3)2.4H2O (1.4 g), Cu(NO3)2.xH2O (2.4 g) and citric acid (243 g) were combined and ground in a pestle and mortar under ambient conditions until a nearly dry paste was formed. However, in contrast to the second step used in the above example, the material was not combined with an iron salt precipitate, but the nearly dry paste in the first step was directly transferred to a quartz boat and heated to 600°C in static air in a muffle furnace (Carbolite laboratory muffle furnace, maximum temperature 1100°C) at a heating rate of 2°C / min and maintained at this temperature for 5 hours to obtain a brown-red powder (precatalyst D).

[0805] The powder was granulated using a manual powder tablet press (769YP-15A) to obtain a granular pre-catalyst composition.

[0806] IE Example 5—Precatalyst Compositions 1 to 34

[0807] The precatalyst composition was prepared by the organic combustion method (OCM); unless otherwise stated, citric acid was used as the organic compound. Typically, the Fe-Cr-Cu-Mn precatalyst composition was prepared from citric acid (99%, Acros Organics), iron (III) nitrate nonahydrate (98%, Sigma-Aldrich or Alfa Aesar), chromium (III) nitrate nonahydrate (99%, Sigma-Aldrich), copper (II) nitrate hemi (pentahydrate) (98%, Thermo Fisher Scientific) and manganese (II) nitrate (50% (w / w) aqueous solution, Thermo Fisher Scientific) in a molar ratio of citric acid: (Fe+Cr+Cu+Mn) = 1:1 and a weight ratio of (Fe- and Cr- and Cu- and Mn-precursors + citric acid) / water = 2:1.

[0808] The method consists of the following steps: metal salts, citric acid and water are mixed in a beaker. The initial mixture is stirred overnight to form a uniform aqueous solution and heated at 80°C for 1 to 2 hours to obtain a citric acid-based slurry. The slurry is then dried in a drying oven at 80 to 100°C overnight. The obtained viscous paste is then heated to 700°C at a rate of 5°C / min and maintained for 6 hours to produce a powder.

[0809] The same method was also used to prepare precatalyst compositions containing different transition metal promoters (eg, Zn, Co, Ni, Zr instead of Cu or Mn).

[0810] Fe-Cr-Zn-Mn, Fe-Cr-Co-Mn, Fe-Cr-Ni-Mn and Fe-Cr-Zr-Mn precatalysts were prepared using zinc nitrate hexahydrate (98%, Thermo Fisher Scientific), cobalt (II) nitrate hexahydrate (98%, Sigma-Aldrich), nickel (II) nitrate hexahydrate (98%, Sigma-Aldrich) and zirconium (IV) nitrate hydrate (99%, Sigma-Aldrich) as transition metal precursors instead of copper (II) nitrate hemi (pentahydrate) (98%, Thermo Fisher Scientific), respectively.

[0811] Fe-Cr-Cu-Zn, Fe-Cr-Cu-Co, Fe-Cr-Cu-Ni and Fe-Cr-Cu-Zr precatalysts were prepared using zinc nitrate hexahydrate (98%, Thermo Fisher Scientific), cobalt (II) nitrate hexahydrate (98%, Sigma-Aldrich), nickel (II) nitrate hexahydrate (98%, Sigma-Aldrich) and zirconium (IV) nitrate hydrate (99%, Sigma-Aldrich) as transition metal precursors instead of manganese (II) nitrate (50% (w / w) aqueous solution, Thermo Fisher Scientific), respectively.

[0812] Similarly, Fe-Cr-Cu-Zr-Li, Fe-Cr-Cu-Zr-Na, Fe-Cr-Cu-Zr-K, Fe-Cr-Cu-Zr-Cs, Fe-Cr-Cu-Zr-Mg, Fe-Cr-Cu-Zr-Ca were prepared with Fe-Cr-Cu-Zr (100:10:2.4:1) as the base by adding alkali metals (Li, Na, K, Cs) and alkaline earth metals (Mg, Ca) using lithium carbonate (99%, Sigma-Aldrich), sodium nitrate (97%, Acros Organics), potassium nitrate (99%, Sigma-Aldrich) and cesium nitrate (99.8%, Thermo Fisher Scientific) to the initial mixture, respectively. Generally, the molar ratio of Fe: alkali metal (or alkaline earth metal) used is 20:1.

[0813] Taking Fe-Cr-Zn-Zr-K (100:10:2.4:1:5) as the base, Fe-Cr-Zn-Zr-KY, Fe-Cr-Zn-Zr-K-La, Fe-Cr-Zn-Zr-K-Ce, Fe-Cr-Zn-Zr-K-Pr and Fe-Cr-Zn-Zr-K-Er precatalysts were prepared by adding rare earth metals (Y, La, Ce, Pr, Er) in the form of salts such as yttrium (III) nitrate hexahydrate (99.8%, Aldrich), lanthanum (III) nitrate hexahydrate (99%, Fluka), cerium (III) nitrate hexahydrate (99.8%, Aldrich), praseodymium (III) nitrate hexahydrate (99.9%, Aldrich) and erbium (III) nitrate pentahydrate (99.9%, Aldrich) into the initial mixture, respectively. Typically, the atomic ratio of iron:rare earth metal used is 100:1.

[0814] Fe-Cr-Zn-Zr-K (100:10:2.4:1:5) precatalysts were also prepared using organic compounds other than citric acid, specifically malic acid (99%, Acros Organics), salicylic acid (99.0%, Sigma-Aldrich), tannic acid (ACS Reagents, Sigma-Aldrich), urea (Biological Reagents, Sigma-Aldrich), oxalic acid (99.0%, Sigma-Aldrich), nitrilotriacetic acid (NTA, 99%, Sigma-Aldrich), N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA, 98%, Sigma-Aldrich), diethylenetriaminepentaacetic acid (DTPA, 98%, Sigma-Aldrich), tannic acid (ACS Reagents, Sigma-Aldrich), ethylenediaminetetraacetic acid (EDTA, 99.5%, Thermo Fisher Scientific), ascorbic acid (99%, Alfa Aesar), and lactic acid (≈90% (T), Sigma-Aldrich).

[0815] Otherwise, citric acid is used as the organic compound to prepare the precatalyst composition. The composition of different metals in the precatalyst composition is expressed in atomic molar ratio.

[0816] The above process yielded precatalyst compositions 1 to 34 (see Table A below).

[0817] Table A

[0818]

[0819]

[0820] Pre-catalyst describe 32 Fe-Cr-Zn-Zr-K(100:10:2.4:1:5)+EDTA 33 Fe-Cr-Zn-Zr-K (100:10:2.4:1:5) + ascorbic acid 34 Fe-Cr-Zn-Zr-K(100:10:2.4:1:5)+lactic acid

[0821] II. Reverse Water Gas Shift Reaction Using Catalysts A to D

[0822] Typically, the precatalyst composition is loaded into a stainless steel fixed bed reactor. The precatalyst composition is then pre-reduced using hydrogen while heating. The reactor is then switched and the desired CO2+xH2 reaction gas mixture feed is fed to reach the desired reaction temperature. The pressure is adjusted to the target pressure and the flow rate of the gas mixture is adjusted as required. The outlet gas is analyzed at 100°C using a Lunan GC 6890A equipped with a TCD detector.

[0823] Prior to the reaction, precatalyst compositions A to D were reduced under a 10% H2 flow supported by N2 for 1 hour while being heated to 600°C at a rate of 2°C / min to activate the catalyst composition and provide catalyst compositions A to D, respectively. Each catalyst composition was then reacted with a feed gas composition consisting of 3:1 H2:CO2 at a temperature of about 600°C and ambient pressure.

[0824] The properties of the catalyst composition are shown in Table 1 below.

[0825] Table 1

[0826]

[0827] It can be observed that in the absence of a catalyst, less than 10% of CO2 is converted to CO at 600°C. However, catalyst composition A converts 57% of CO2 to CO and produces trace amounts of methane. When catalyst A is impregnated with palladium (i.e., catalyst composition B), under the same conditions, the CO2 conversion rate rises to 61.4% and no methane is detected.

[0828] When the zirconium component in precatalyst composition A is replaced with a manganese component (ie, precatalyst composition C), it can be seen that the CO2 conversion of the corresponding catalyst composition (catalyst composition C) is increased to 63.5%, the CO selectivity is 99%, and no methane is detected.

[0829] Compared with catalyst composition C, which was prepared by a combination of combustion and precipitation, catalyst composition D was prepared by combustion but without a precipitation step. Catalyst composition D had a CO2 conversion of 56.8% and a CH4 selectivity of 0.6%.

[0830] III. Reverse Water Gas Shift Reaction Using Catalysts 1 to 34

[0831] Typically, the precatalyst composition is loaded into a stainless steel fixed bed reactor with an inner diameter of 1.0 cm, with a typical loading of 1.2 g precatalyst and 4.8 g SiC. In order to activate the precatalyst to form an active catalyst composition in situ, a feed gas mixture with a ratio of H2 to CO2 of 3:1 and containing N2 (as an internal standard gas) is used at a gas hourly space velocity (GHSV) of 2500 mL / (g·h). The reactor is then heated to 600°C at a rate of 5°C / min at atmospheric pressure, unless otherwise stated. The outlet gas is analyzed using an online gas chromatograph (Agilent 8890GC) equipped with a hydrogen flame ionization detector (FID) and a thermal conductivity detector (TCD).

[0832] The data in Table 2 were collected at an operating temperature of 600°C, a GHSV of 2500 ml / (g·h) and a pressure of 0 bar to 0.5 bar. The effects of various metals on the catalytic performance are shown. Various transition metals replaced copper or manganese with the catalyst Fe-Cr-Cu-Mn (100:10:2.4:1) as the base. Catalyst 16 (Fe-Cr-Zn-Zr) showed the best CO2 conversion and the lowest CH4 selectivity.

[0833] Table 2

[0834]

[0835] The effects of alkali and alkaline earth metals on the catalyst performance are shown in Table 3. The data were collected at an operating temperature of 600°C, a GHSV of 2500 ml / (g·h) and a pressure of 0 bar to 0.5 bar. From Table 3, it can be seen that the addition of alkali and alkaline earth metals such as Li, Na, K, Cs and Ca can eliminate any CH4 selectivity.

[0836] The results for Catalyst 14 and Catalyst 15 show the effect of alkaline earth metals on catalyst performance and CH4 selectivity. Adding Ca eliminates CH4 selectivity.

[0837] Table 3

[0838]

[0839]

[0840] The effect of rare earth metals on catalyst performance is shown in Table 4. The data were collected at an operating temperature of 600°C, a GHSV of 2500 ml / (g·h) and a pressure of 0 bar to 0.5 bar. All rare earth metals have very similar performance with no CH4 selectivity.

[0841] Table 4

[0842]

[0843] The effect of the organic compound used to prepare the precatalyst composition on the catalyst performance is shown in Table 5. The data were collected at an operating temperature of 600°C, a GHSV of 2500 ml / (g·h) and a pressure of 0 bar to 0.5 bar. Fe-Cr-Zn-Zr-K catalysts prepared with citric acid, malic acid, salicylic acid, tartaric acid, urea, oxalic acid, NTA, HEDTA, DTPA, tannic acid, EDTA, ascorbic acid and lactic acid showed similar CO2 conversion, 100% CO selectivity, and no CH4 selectivity.

[0844] Table 5

[0845]

[0846]

[0847] The effect of operating pressure on the catalyst performance is shown in Table 6. The data were collected at an operating temperature of 600°C, a GHSV of 2500 ml / (g·h) and a pressure of 0 to 3 barg.

[0848] Table 6

[0849]

[0850] The effect of the reaction bed temperature on the catalyst performance is shown in Table 7. The data were collected in the operating temperature range of 400°C to 800°C (50°C interval), GHSV of 2500 ml / (g·h) and pressure of 0 bar to 0.5 bar.

[0851] Table 7

[0852]

[0853] IV. Catalyst Characteristics

[0854] Powder X-ray diffraction (XRD) analysis of the catalyst was performed using a Cu Kα (0.154056 nm) X-ray source (25 kV, 40 mA) on a Bruker D8 Advance diffractometer. Diffraction patterns were recorded in the 10-80° 2θ angle range using a step size of 0.02°. The crystallite size was determined using the Scherrer formula.

[0855] X-ray photoelectron spectroscopy (XPS) was performed on the samples using a Thermo Fisher Scientific Nexsa spectrometer. The samples were analyzed in an area of ​​about 400 mm using a microfocused monochromatic Al X-ray source (72 W). Data were recorded at a full scan pass of 150 eV and a high resolution scan pass of 40 eV with a step size of 1 eV and 0.1 eV, respectively. Charge neutralization was achieved using a combination of low energy electrons and argon ions. The resulting spectra were analyzed using Casa XPS peak fitting software, and the sample charge was corrected using the C1s signal at 284.8 eV as a reference.

[0856] Transmission electron microscopy (TEM) and energy dispersive X-ray tomography in scanning transmission electron microscopy (STEM / EDX) imaging were performed on a 200 kV analytical TEM (JEOL 2100) equipped with OI Aztec. Prior to analysis, a small amount of powder sample was dry cast onto a holey carbon-coated copper grating.

[0857] Powder X-ray diffraction (XRD) spectra of various precatalyst compositions are shown in Figure 1 .

[0858] The surface element composition and oxidation state of the metal of the catalyst precursor 17 were analyzed by XPS in the region of 0 eV to 1100 eV. Figure 2 a) Indicates that the sample contains Fe, Cr, Zn, Zr, K, C and O. Figure 2 b shows the XPS spectrum of the Fe 2p region, which can be fitted to correspond to the Fe 2p 3 / 2 Peak and Fe 2p 1 / 2 peak (binding energy gap is 13.5 eV, vibrational companion peak is attributed to Fe 3+ ) two spin-orbit doublets, most of the peaks can be attributed to Fe 3+ , a small amount of peaks are attributed to Fe 2+ , which indicates that Fe2O3 contains a small amount of Fe3O4.

[0859] Figure 2 c shows the Cr 2p XPS spectrum, which shows that most of the chromium is Cr2O3 (chromium (III) oxide in the figure). Figure 2 d. Figure 2 e. Figure 2 f shows Zr 3d, Zn 2p and K 2p at 181.9 eV / 183.9 eV, 1021.4 eV / 1044.5 eV and 292.7 eV / 295.4 eV, respectively.

[0860] Figure 2h shows the XPS spectrum of O1s, with the main peak at 529.9 eV, which is obviously due to the presence of metal-O bonds.

[0861] The XPS spectrum of C1s present ( Figure 2 g) shows that CC, C=O and CO have peaks at 284.8 eV, 288.4 eV and 286.4 eV, respectively. Carbon is the carbon residue produced by calcination of citric acid, and the peak of C=O can be attributed to the incompletely decomposed citric acid residue.

[0862] Transmission electron microscopy (TEM) of the precatalyst composition 17 is as follows: Figure 3 The overview images at low and medium magnifications show a variety of particle sizes and shapes. Two size ranges are clearly visible: large particles in the hundreds of nanometers (nm) to micrometers ( Figure 3 a) and smaller particles ranging from 5nm to 20nm ( Figure 3 b).

[0863] Figure 3 c to Figure 3 f shows a high resolution TEM (HRTEM), with the smaller particles mostly attached to the surface of the larger particles, and some evidence of carbonaceous material covering both the large and small particles can also be detected. At higher magnifications, the lattice parameters of the small particles can be resolved, and the FFT shows that there are many different d spacings. D spacings of 0.37nm and 0.47nm are more common. This is due to the combination of Fe2O3 and Fe3O4 in some of the less common images. Some of the larger particles are Fe2O3 (lattice spacings of 0.37 to 112), while the smaller particles at the edges of the larger particles seem to be more characteristic of Fe3O4 (lattice spacings of 0.47 to 111). Figure 3 f shows an image of a region with large Fe2O3 crystals with smaller Fe3O4 crystals at the edges.

[0864] Energy dispersive X-ray tomography (ESX) of the catalyst precursor 17 in a scanning transmission electron microscope (STEM / EDX) is shown in FIG. Figure 4 As shown, EDX of different regions shows the variation of chemical content, some regions have Fe content > 80%, some regions have different iron-oxygen ratios, and some regions contain small amounts of Cr or Zn. The images of different elements show similar shapes, which indicates that these elements are evenly dispersed.

[0865] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety (to the maximum extent permitted by law).

[0866] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0867] The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the present invention and does not limit the scope of the present invention unless otherwise specified. No language in the specification should be construed as indicating that any unspecified element is essential to the implementation of the present invention.

[0868] The citation and incorporation of patent documents herein is for convenience only and does not reflect any opinion regarding the validity, patentability and / or enforceability of these patent documents.

[0869] This invention includes all modifications and equivalents of the subject matter listed in the following paragraphs as permitted by applicable law.

Claims

1. A method for preparing a precatalyst composition, the method comprising: (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; Chromium salt or hydrate thereof; organic compound containing one or more functional groups selected from the group consisting of carboxyl, hydroxyl, amido and amino; and Optionally, one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof are combined; Optionally (ii) combining a solution of an iron salt or a hydrate thereof and an alkaline aqueous solution; and optionally, one or more of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof and a copper salt or a hydrate thereof, to obtain a precipitate; (iii) calcining the product of (i) or the combined product of (i) and (ii) to obtain a precatalyst composition.

2. The method for preparing a precatalyst composition according to claim 1, comprising: (i) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; A chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and one or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof; and (ii) calcining the material of (i) to obtain a precatalyst composition.

3. The method for preparing a precatalyst composition according to claim 1 or 2, comprising: (i)(a) an iron species selected from an iron salt or a hydrate thereof, or an iron oxide or a hydrate thereof; A chromium salt or a hydrate thereof; an organic compound containing one or more functional groups selected from the group consisting of a carboxyl group, a hydroxyl group, an acylamino group and an amino group; and One or more transition metal species selected from the group consisting of manganese salts or hydrates thereof, zirconium salts or hydrates thereof, copper salts or hydrates thereof, zinc salts or hydrates thereof, cobalt salts or hydrates thereof, and nickel salts or hydrates thereof; as well as Water binding; (i)(b) drying the aqueous product of (i)(a) to obtain a dried substance; (ii) calcining the material of (i)(b) to obtain a precatalyst composition.

4. The method according to any one of claims 1 to 3, wherein the transition metal species of step (i) is selected from two or more of the group consisting of a manganese salt or a hydrate thereof, a zirconium salt or a hydrate thereof, a copper salt or a hydrate thereof, and a zinc salt or a hydrate thereof.

5. The method according to any one of claims 1 to 4, wherein the transition metal species is: (a) a copper salt or a hydrate thereof and a manganese salt or a hydrate thereof; or (b) a zinc salt or a hydrate thereof and a manganese salt or a hydrate thereof; or (c) a copper salt or a hydrate thereof and a zirconium salt or a hydrate thereof; or (d) a zinc salt or a hydrate thereof and a zirconium salt or a hydrate thereof.

6. The method according to any one of the preceding claims, wherein step (i) further comprises: One or more of an alkali metal species, an alkaline earth metal species, and a rare earth metal species are combined.

7. The method according to any one of the preceding claims, wherein step (i) further comprises: One or more alkali metal species selected from alkali metal salts or hydrates thereof are combined.

8. The method according to claim 7, wherein the alkali metal salt or a hydrate thereof is selected from potassium nitrate, potassium carbonate, sodium nitrate, sodium carbonate, lithium carbonate and cesium carbonate or a hydrate thereof.

9. The method according to any one of the preceding claims, wherein the iron species is an iron salt or a hydrate thereof.

10. A method according to any one of the preceding claims, wherein the iron salt or hydrate of step (i) is one or more of Fe(NO3)2 and Fe(NO3)3 or hydrates thereof.

11. The method according to any one of the preceding claims, wherein the chromium salt or hydrate thereof is selected from one or more of the group consisting of Cr(NO3)3, CrCl3, Cr(Ac)3 and Cr(OH)3 or hydrates thereof.

12. A method according to any one of the preceding claims, wherein the ratio of the iron salt to the chromium salt is such that the atomic ratio of iron to chromium is from about 20:1 to about 5:

4.

13. The method according to any one of the preceding claims, wherein the organic compound comprises two or more functional groups selected from carboxyl, hydroxyl, amido and amino groups.

14. The method according to any one of the preceding claims, wherein the organic compound is C4 to C 12 Carboxylic acid or urea.

15. The method according to any one of the preceding claims, wherein the organic compound is citric acid.

16. The method according to any one of claims 1 to 3, wherein step (i) consists of the following steps: making an iron (II) or (III) salt or a hydrate thereof; a chromium (III) salt or a hydrate thereof; a C4 to C 12 An organic compound of a carboxylic acid, preferably citric acid, or urea; a zinc(II) salt or a hydrate thereof; a zirconium(IV) salt or a hydrate thereof; a calcium salt or a hydrate thereof or a potassium salt or a hydrate thereof; and optionally water.

17. The method according to any one of the preceding claims, wherein the calcining step is carried out at a temperature between about 400°C and about 1000°C.

18. The method of claim 1, wherein the method comprises: (i) combining an iron salt or a hydrate thereof, a chromium salt or a hydrate thereof, an organic compound selected from citric acid or urea, a manganese salt or a hydrate thereof, and a copper salt or a hydrate thereof; (ii) combining a solution of an iron salt or a hydrate thereof with an alkaline aqueous solution; (iii) calcining the combined product of (i) and (ii) to obtain a precatalyst composition.

19. The method according to any one of claims 1 and 4 to 18, wherein the method further comprises: (iv) treating the precatalyst composition of step (iii) with a transition metal solution comprising one or more transition metal salts or hydrates thereof selected from Pd, Co, Ni, Pt, Ru, Rh, Au and Cu salts or hydrates thereof; and optionally, calcining the treated precatalyst composition.

20. The method of claim 19, wherein the transition metal solution comprises a palladium salt or a hydrate thereof.

21. A precatalyst composition obtained or obtainable according to the process of any one of claims 1 to 20.

22. A method for preparing a catalyst composition, the method comprising: (a) providing a precatalyst composition according to claim 21; (b) optionally calcining the precatalyst composition; as well as (c) activating the precatalyst composition to obtain a catalyst composition.

23. A catalyst composition obtained or obtainable by the process according to claim 22.

24. A method of preparing a composition comprising carbon monoxide, wherein the method comprises: A feed gas composition comprising carbon dioxide and hydrogen is contacted with the precatalyst composition of claim 21 or the catalyst composition of claim 23 at a temperature of at least 400°C.

25. The method of claim 24, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a temperature of about 450°C to about 650°C.

26. The method of claim 24 or 25, wherein the feed gas composition is contacted with the precatalyst composition or the catalyst composition at a pressure of about 100 KPa to about 150 KPa.

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