Iron-Manganese-Based Catalysts, Catalyst Precursors, and Catalytic Methods

Abstract

A catalyst precursor comprising an iron substance, an alkali metal or a salt thereof, and a complexing agent; a catalyst obtainable from said precursor; and a method for hydrogenating carbon dioxide and / or carbon monoxide to produce olefins or fuels such as jet engine fuel using said catalyst precursor or said catalyst.

Description

Technical Field

[0001] This disclosure describes hydrogenation catalysts, their precursors, and their use in processes suitable for converting carbon dioxide and / or carbon monoxide into hydrocarbons. In particular, the catalysts and processes described herein produce C 5+ hydrocarbons, particularly C 5+ α-olefins. Background Art

[0002] Olefins are widely used in the chemical industry as building blocks for manufacturing a wide range of products and as a major component of fuels. α-Olefins have a double bond at the terminal or α-position, which enhances the reactivity at this position and makes them useful for producing detergents, lubricants, plasticizers, pharmaceuticals, fine chemicals, and polymers.

[0003] The catalytic preparation of hydrocarbons from synthesis gas is well-known and is generally referred to as Fischer-Tropsch synthesis. However, Fischer-Tropsch synthesis tends to promote the formation of saturated alkanes.

[0004] In addition, it is well-known that there is a need to reduce greenhouse gas (GHG) emissions in the transportation industry. Due to improved fuel efficiency, hydrogen fuel cells, and electric vehicles, the UK reduced its GHG emissions from road transport by 8.6% between 2002 and 2012. However, emissions from the second largest transportation segment - aviation - increased by approximately 6%.

[0005] Producing fuels from CO2 or CO can address the aforementioned energy needs while meeting environmental standards. However, state-of-the-art CO2-to-fuel conversion mainly produces C1 products (synthesis gas, formic acid, methanol), and less frequently produces C2 to C4 products such as mixed alcohols and olefins. These processes can produce long-chain hydrocarbon mixtures after methanol-to-olefins (MTO) or FT synthesis. However, obtaining fuels such as jet engine fuel directly via such routes is particularly challenging because they cannot produce the desired composition (i.e., containing C 5+ hydrocarbons) to meet strict, well-established standards.

[0006] There is a need for new, high-performance catalysts and processes suitable for converting carbon dioxide and / or carbon monoxide into hydrocarbons. In particular, there is a need for inexpensive and abundant catalysts and methods using such catalysts that increase the conversion rate of carbon dioxide and / or carbon monoxide, and / or increase the yield of valuable hydrocarbons such as C 5+ hydrocarbons (including C 5+ (α) - olefins). Summary of the Invention

[0007] In a first aspect, the present invention relates to a catalyst precursor comprising an iron substance, an alkali metal or its salt, and a complexing agent.

[0008] In a second aspect, the present invention relates to a method for preparing a catalyst precursor, which comprises:

[0009] (a) combining (i) an iron substance, (ii) an alkali metal or its salt, (iii) a complexing agent, and (iv) a solvent;

[0010] (b) stirring the mixture of step (a) to provide a homogeneous mixture;

[0011] (c) heating the mixture of step (b) to partially remove the solvent, thereby providing a slurry or paste;

[0012] In a third aspect, the present invention relates to a catalyst precursor obtainable by the method of the second aspect.

[0013] In a fourth aspect, the present invention relates to a catalyst obtainable by activating a catalyst precursor according to the first aspect.

[0014] In a fifth aspect, the present invention relates to a method for preparing a catalyst, which comprises:

[0015] (a) providing a catalyst precursor according to the first or third aspect of the present invention;

[0016] (b) optionally calcining the catalyst precursor; and

[0017] (c) activating the precursor.

[0018] In a sixth aspect, the present invention relates to a catalyst obtainable by the method of the fifth aspect.

[0019] In a seventh aspect, the present invention relates to a method for the hydrogenation of carbon dioxide, the method comprising: contacting a feedstock comprising hydrogen and carbon dioxide with a catalyst precursor according to the first aspect or a catalyst according to the fourth or sixth aspect at elevated temperature and pressure.

[0020] In an eighth aspect, the present invention relates to a method for the hydrogenation of carbon monoxide, the method comprising: contacting a feedstock comprising hydrogen and carbon monoxide with a catalyst precursor according to the first aspect or a catalyst according to the fourth or sixth aspect at elevated temperature and pressure.

[0021] In a ninth aspect, the present invention relates to a method for producing olefins, the method comprising: contacting a feedstock comprising hydrogen and carbon dioxide and / or carbon monoxide with a catalyst precursor according to the first aspect or a catalyst according to the fourth or sixth aspect at elevated temperature and pressure.

[0022] In a tenth aspect, the present invention relates to a method for producing fuel, the method comprising: contacting a feedstock comprising hydrogen and carbon dioxide and / or carbon monoxide with a catalyst precursor according to the first aspect or a catalyst according to the fourth or sixth aspect at elevated temperature and pressure.

[0023] In an eleventh aspect, the present invention relates to a heterogeneous mixture comprising a catalyst precursor according to the first aspect or a catalyst according to the fourth or sixth aspect and a gas containing hydrogen and carbon monoxide, and / or hydrogen and carbon dioxide.

[0024] Preferred, suitable and optional features of any particular aspect of the present invention are also preferred, suitable and optional features of any other aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an apparatus for evaluating catalyst performance is shown.

[0026] Figure 2 The molar ratio of olefins to alkanes in the liquid products produced after CO2 hydrogenation via Fe-Mn-K (100:10:5) [Catalyst 3], Fe-Mn-K (100:10:8) [Catalyst 5], Fe-Mn-K (100:20:5) [Catalyst 6] is shown.

[0027] Figures 3 to 7 XRD spectra of various CO2 hydrogenation catalysts are shown.

[0028] Figure 8 The GC-MS spectrum of the product curve after CO hydrogenation via a Fe-Co-Mn-Na (100:5:20:2) catalyst at 300 °C when the syngas feedstock is 1:1 (H2:CO) is shown.

[0029] Figure 9 The CO2 hydrogenation performance of the Fe-Mn-K catalyst is shown: (a) the conversion of CO2 and H2 over reaction time; (b) the selectivity of hydrocarbon products over reaction time.

[0030] Figure 10 The GC-MS spectrum of the fuel from CO2 hydrogenation via the Fe-Mn-K catalyst is shown.

[0031] Figure 11 XRD spectra of the Fe-Mn-K catalyst precursor, the activated catalyst and the used catalyst are shown.

[0032] Figure 12The XPS spectra of the Fe-Mn-K catalyst precursor are shown. 12a) XPS measurement spectra of the Fe-Mn-K catalyst; 12b) High-resolution XPS spectra of Fe 2p.

[0033] Figure 13 SEM images of a) the Fe-Mn-K catalyst precursor and b) the used catalyst are shown.

[0034] Figure 14 HRTEM images of the Fe-Mn-K catalyst precursor (14a, 14b, 14c) and the used catalyst (14d, 14e, 14f) are shown. Detailed Description

[0035] Definitions

[0036] As used herein, the term "catalyst precursor" refers to a material used to prepare a catalytically active substance. Generally, the precursor is prepared by calcining its components. Generally, the catalyst precursor needs to be converted into a catalytically active substance, for example, by oxidation, reduction, and / or heat treatment, or a combination thereof. Suitably, it is activated via reduction. The catalyst precursor can be converted into a catalytically active substance (i.e., "activated") in situ (i.e., under reaction conditions), or the catalyst precursor can also be converted into a catalytically active substance before being added to the reaction.

[0037] As used herein, the term "liquid" refers to a material that is liquid at standard ambient temperature and pressure (SATP) (i.e., at a temperature of 298.15 K (25 °C) and at a pressure of 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm)).

[0038] As used herein, the term "hydrocarbon" refers to an organic compound composed of carbon and hydrogen.

[0039] To avoid doubt, hydrocarbons include straight-chain and branched, saturated and unsaturated aliphatic hydrocarbon compounds, including alkanes, alkenes, and alkynes; and saturated and unsaturated cyclic aliphatic hydrocarbon compounds, including cycloalkanes, cycloalkenes, and cycloalkynes; and hydrocarbon polymers, such as polyolefins.

[0040] Hydrocarbons also include aromatic hydrocarbons, i.e., hydrocarbons containing one or more aromatic rings. The aromatic ring can be monocyclic or polycyclic.

[0041] The term "hydrocarbon" (such compounds consisting only of carbon and hydrogen) of course also includes aliphatic hydrocarbons substituted with one or more aromatic hydrocarbons and aromatic hydrocarbons substituted with one or more aliphatic hydrocarbons, as well as straight-chain or branched aliphatic hydrocarbons substituted with one or more cyclic aliphatic hydrocarbons and cyclic aliphatic hydrocarbons substituted with one or more straight-chain or branched aliphatic hydrocarbons.

[0042] "C n-m hydrocarbon" or "Cn to C m The term “hydrocarbon” or “Cn to Cm hydrocarbon” (where n and m are integers) refers to a hydrocarbon as defined above having from n to m carbon atoms. For example, a C 5-16 hydrocarbon is a hydrocarbon as defined above having from 5 to 16 carbon atoms, a C 5+ hydrocarbon is a hydrocarbon as defined above having 5 or more carbon atoms, and so on.

[0043] As used herein, the term “alkane” refers to a linear or branched saturated hydrocarbon compound. Examples of alkanes are, for example, butane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane. An alkane such as dimethylbutane can be one or more of the possible isomers of the compound. Thus, dimethylbutane includes 2,3-dimethylbutane and 2,2-dimethylbutane. This also applies to all hydrocarbon compounds mentioned herein, including cycloalkanes, alkenes, and cycloalkenes.

[0044] As used herein, the term “cycloalkane” refers to a saturated cyclic aliphatic hydrocarbon compound. Examples of cycloalkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, methylcyclopentane, cycloheptane, methylcyclohexane, dimethylcyclopentane, and cyclooctane. Examples of C5-8 cycloalkanes include cyclopentane, cyclohexane, methylcyclopentane, cycloheptane, methylcyclohexane, dimethylcyclopentane, and cyclooctane. The terms “cycloalkane” and “cycloalkane” can be used interchangeably.

[0045] As used herein, the term “alkene” refers to a linear or branched hydrocarbon compound containing one or more carbon-carbon double bonds. Examples of alkenes are butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, and tetradecene. Alkenes typically contain one or two double bonds. The terms “alkene” and “olefin” can be used interchangeably. One or more double bonds can be at any position in the hydrocarbon chain. Alkenes can be cis or trans alkenes (or defined using the E- and Z-nomenclature). An alkene containing a terminal double bond can be referred to as a “chain-1-ene” (e.g., hex-1-ene), a “terminal alkene” (or “terminal olefin”), or an “alpha-alkene” (or “alpha-olefin”). As used herein, the term “alkene” generally also includes cycloalkenes.

[0046] As used herein, the term “cycloalkene” refers to a partially unsaturated cyclic hydrocarbon compound. Examples of cycloalkenes include cyclobutene, cyclopentene, cyclohexene, cyclohex-1,3-diene, methylcyclopentene, cycloheptene, methylcyclohexene, dimethylcyclopentene, and cyclooctene. Cycloalkenes can contain one or two double bonds.

[0047] As used herein, the term "aromatic hydrocarbon" or "aromatic hydrocarbon compound" refers to a hydrocarbon compound containing one or more aromatic rings. The aromatic ring can be monocyclic or polycyclic. Generally, aromatic compounds contain benzene rings. Aromatic compounds can be, for example, C6-14 aromatic compounds, C6-12 aromatic compounds, or C6-10 aromatic compounds. Examples of C6-14 aromatic compounds are benzene, toluene, xylene, ethylbenzene, methylethylbenzene, diethylbenzene, naphthalene, methylnaphthalene, ethylnaphthalene, and anthracene.

[0048] As used herein, "metal substance" is any compound containing a metal. Thus, metal substances include elemental metals, metal oxides, and other compounds containing metals, namely salts, alloys, hydroxides, carbides, borides, silicides, and hydrides of metals. When referring to specific examples of metal substances, the term includes all compounds containing that metal. For example, iron substances include, for example, elemental iron, iron oxides, iron salts, iron alloys, iron hydroxides, iron carbides, iron borides, iron silicides, and iron hydrides.

[0049] As used herein, the term "heterogeneous mixture" refers to a physical combination of at least two different substances, where the two different substances are not in the same phase. For example, one substance can be a solid and one substance can be a liquid or a gas.

[0050] Catalyst precursor

[0051] In one aspect, the present invention relates to a catalyst precursor comprising at least one iron substance, an alkali metal or a salt thereof, and a complexing agent.

[0052] In one embodiment, the present invention relates to a catalyst precursor comprising iron or a salt thereof, an oxide thereof, or a hydroxide thereof, an alkali metal or a salt thereof, and a complexing agent.

[0053] In one embodiment, the complexing agent is suitable for complexing metal cations (especially iron cations). Thus, suitable complexing agents contain one or more functional groups selected from carboxylic acid, hydroxyl, amide, or amino groups. Suitably, the complexing agent contains two or more functional groups selected from carboxylic acid, hydroxyl, amide, or amino groups. Suitably, the complexing agent is an organic compound.

[0054] In one embodiment, the complexing agent or organic compound is selected from hydroxycarboxylic acids, aminocarboxylic acids, polycarboxylic acids, or salts thereof. Suitably, the complexing agent or organic compound is selected from hydroxycarboxylic acids and polycarboxylic acids, or salts thereof. Alternatively, the complexing agent or organic compound is selected from hydroxycarboxylic acids and aminocarboxylic acids, or salts thereof.

[0055] In one embodiment, the complexing agent or organic compound is a bidentate or polydentate hydroxycarboxylic acid or a salt thereof.

[0056] In one embodiment, the complexing agent or organic compound is selected from glycolic acid, lactic acid, hydroxypropionic acid (hydracylic acid), hydroxybutyric acid, hydroxypentanoic acid, malic acid, mandelic acid, citric acid, saccharic acid, tartronic acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, glycine, hippuric acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitroilotiracetic acid, nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), alanine, valine, leucine and isoleucine, and salts thereof.

[0057] In one embodiment, the complexing agent or organic compound is selected from glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxypentanoic acid, malic acid, mandelic acid, citric acid, saccharic acid, tartronic acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, hippuric acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or salts thereof.

[0058] In one embodiment, the complexing agent or organic compound is selected from hydroxybutyric acid, hydroxypentanoic acid, malic acid, mandelic acid, citric acid, saccharic acid, tartronic acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, hippuric acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or salts thereof.

[0059] In one embodiment, the complexing agent or organic compound is selected from hydroxybutyric acid, hydroxypentanoic acid, malic acid, mandelic acid, citric acid, saccharic acid, tartronic acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or salts thereof.

[0060] In one embodiment, the complexing agent or organic compound is selected from citric acid, saccharic acid, tartaric acid, oxalic acid, salicylic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or salts thereof.

[0061] In one embodiment, the complexing agent or organic compound is selected from citric acid, saccharic acid, tartaric acid, oxalic acid, salicylic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or a salt thereof.

[0062] In one embodiment, the complexing agent or organic compound is selected from citric acid, tartaric acid, oxalic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or a salt thereof. Suitably, the complexing agent is citric acid.

[0063] In one embodiment, the molar ratio of the complexing agent to the metal is from about 0.4:1 to about 4:1. Suitably, the molar ratio of the complexing agent to the metal is from about 0.5:1 to about 2:1.

[0064] In one embodiment, the molar ratio of the complexing agent to the metal is from about 0.8:1 to about 4:1. Suitably, the molar ratio of the complexing agent to the metal is from about 1:1 to about 3:1.

[0065] In one embodiment, the molar ratio of the complexing agent to the metal is from about 0.5:1 to about 5:1. Suitably, the molar ratio of the complexing agent to the metal is from about 0.8:1 to about 2:1.

[0066] In one embodiment, the molar ratio of the complexing agent to iron is from about 0.5:1 to about 5:1. Suitably, the molar ratio of the complexing agent to iron is from about 0.8:1 to about 2:1.

[0067] In one embodiment, the iron species is selected from elemental iron, iron salts, iron oxides, iron alloys, iron hydroxides, iron carbides, iron borides, iron silicides, and iron hydrides. Suitably, the iron species is selected from elemental iron, iron salts, iron alloys, iron hydroxides, and iron silicides. More suitably, the iron species is selected from elemental iron, iron salts, and iron hydroxides.

[0068] In one embodiment, the iron species is an iron salt. In one embodiment, the iron salt is iron nitrate, iron sulfate, an iron halide (suitably iron chloride), or an iron organic acid salt. Suitably, the iron salt is iron(III) nitrate or iron(II) nitrate.

[0069] In another embodiment, the iron species is iron powder. Those skilled in the art will understand that iron powder is elemental iron in a commercially available form.

[0070] In another embodiment, the iron species is an iron oxide, suitably Fe3O4.

[0071] In one embodiment, the catalyst precursor comprises from about 5 wt% to about 90 wt% Fe. Suitably, the catalyst precursor comprises from about 10 wt% to about 90 wt% Fe. Suitably, from about 15 wt% to about 90 wt% Fe, more suitably from about 20 wt% to about 90 wt% Fe, more suitably from about 25 wt% to about 90 wt% Fe, more suitably from about 30 wt% to about 90 wt% Fe, more suitably from about 40 wt% to about 90 wt% Fe, more suitably from about 50 wt% to about 90 wt% Fe.

[0072] In one embodiment, the catalyst precursor comprises from about 5 wt% to about 80 wt% Fe. Suitably, the catalyst precursor comprises from about 10 wt% to about 80 wt% Fe. Suitably, from about 15 wt% to about 80 wt% Fe, more suitably from about 20 wt% to about 80 wt% Fe, more suitably from about 25 wt% to about 80 wt% Fe, more suitably from about 30 wt% to about 80 wt% Fe, more suitably from about 40 wt% to about 80 wt% Fe, more suitably from about 50 wt% to about 80 wt% Fe.

[0073] In another embodiment, the catalyst precursor comprises from about 10 wt% to about 90 wt% Fe. Suitably, the catalyst precursor comprises from about 10 wt% to about 80 wt% Fe. Suitably, from about 10 wt% to about 70 wt% Fe, more suitably from about 10 wt% to about 65 wt% Fe.

[0074] In another embodiment, the catalyst precursor comprises from about 10 wt% to about 80 wt% Fe. Suitably, the catalyst precursor comprises from about 10 wt% to about 70 wt% Fe. Suitably, from about 10 wt% to about 60 wt% Fe, more suitably from about 10 wt% to about 50 wt% Fe.

[0075] In one embodiment, the alkali metal is selected from potassium, sodium, lithium or cesium. Thus, the catalyst precursor may comprise potassium, sodium, lithium or cesium, or a salt thereof. Suitably, the alkali metal is present as a salt. Suitably, the alkali metal is an alkali metal carbonate, such as potassium carbonate, sodium carbonate, cesium carbonate, lithium carbonate.

[0076] In one embodiment, the catalyst precursor comprises from about 0.5 wt% to about 30 wt% alkali metal. Suitably, the catalyst precursor comprises from about 0.5 wt% to about 25 wt% alkali metal. Suitably, from about 0.5 wt% to about 20 wt% alkali metal, more suitably from about 0.5 wt% to about 15 wt% alkali metal, more suitably from about 0.5 wt% to about 10 wt% alkali metal, more suitably from about 0.5 wt% to about 5 wt% alkali metal.

[0077] In one embodiment, the catalyst precursor comprises from about 1 wt% to about 30 wt% of an alkali metal. Suitably, the catalyst precursor comprises from about 1 wt% to about 25 wt% of an alkali metal. Suitably, from about 1 wt% to about 20 wt% of an alkali metal, more suitably from about 1 wt% to about 15 wt% of an alkali metal, more suitably from about 1 wt% to about 10 wt% of an alkali metal, more suitably from about 1 wt% to about 5 wt% of an alkali metal.

[0078] In one embodiment, the catalyst precursor may comprise additional metal species. Suitably, these additional metals will be used as promoters in the catalytically active material. In one embodiment, the additional metal species is a transition metal species. Suitably, the additional metal species is a transition metal, or a salt, an oxide or a hydroxide thereof.

[0079] Suitably, the catalyst precursor further comprises cobalt, chromium, copper, iridium, manganese, molybdenum, palladium, platinum, rhenium, rhodium, ruthenium, strontium, tungsten, vanadium, zinc, or a salt, an oxide or a hydroxide thereof.

[0080] In another embodiment, the catalyst precursor further comprises cobalt, copper, manganese, zinc, or a salt, an oxide or a hydroxide thereof.

[0081] In one embodiment, the catalyst precursor comprises manganese oxide.

[0082] In one embodiment, the catalyst precursor comprises manganese nitrate.

[0083] In one embodiment, the catalyst precursor comprises from about 1 wt% to about 50 wt% of additional metal species. Suitably, the catalyst precursor comprises from about 1 wt% to about 40 wt% of additional metal species.

[0084] In another embodiment, the catalyst precursor comprises from about 5 wt% to about 30 wt% of additional metal species, more suitably from about 5 wt% to about 20 wt% of additional metal species, more suitably from about 5 wt% to about 15 wt% of additional metal species, more suitably from about 5 wt% to about 15 wt% of additional metal species.

[0085] In one embodiment, the catalyst precursor comprises from about 1 wt% to about 30 wt% of additional metal species. Suitably, the catalyst precursor comprises from about 1 wt% to about 25 wt% of additional metal species. Suitably, from about 1 wt% to about 20 wt% of additional metal species, more suitably from about 1 wt% to about 15 wt% of additional metal species, more suitably from about 1 wt% to about 10 wt% of additional metal species, more suitably from about 1 wt% to about 5 wt% of additional metal species.

[0086] In one embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; at least one additional transition metal selected from Mn, Zn, Cu and Co, or a salt, oxide or hydroxide thereof; an alkali metal or a salt thereof; and a complexing agent.

[0087] In one embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; at least one additional transition metal selected from Mn, Zn, Cu and Co, or a salt, oxide or hydroxide thereof; an alkali metal or a salt thereof; and an organic compound.

[0088] In another embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; at least one additional transition metal or salt, oxide or hydroxide selected from Mn and Co; an alkali metal or a salt thereof; and a complexing agent.

[0089] In another embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; at least one additional transition metal or salt, oxide or hydroxide selected from Mn and Co; an alkali metal or a salt thereof; and an organic compound.

[0090] In another embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; an additional transition metal or salt, oxide or hydroxide selected from Mn and Co; an alkali metal or a salt thereof; and a complexing agent.

[0091] In another embodiment, the catalyst precursor comprises iron or a salt, oxide or hydroxide thereof; an additional transition metal or salt, oxide or hydroxide selected from Mn and Co; an alkali metal or a salt thereof; and an organic compound.

[0092] In another embodiment, the catalyst precursor comprises an iron salt, a manganese salt, an alkali metal or a salt thereof, and a complexing agent.

[0093] In another embodiment, the catalyst precursor comprises an iron salt, a manganese salt, an alkali metal or a salt thereof, and an organic compound.

[0094] In another embodiment, the catalyst precursor comprises iron powder, a manganese salt, a cobalt salt, an alkali metal or a salt thereof, and a complexing agent.

[0095] In another embodiment, the catalyst precursor comprises iron powder, a manganese salt, a cobalt salt, an alkali metal or a salt thereof, and an organic compound. In another embodiment, the catalyst precursor comprises iron nitrate, manganese nitrate, an alkali metal or a salt thereof, and a complexing agent.

[0096] In another embodiment, the catalyst precursor comprises iron nitrate, manganese nitrate, an alkali metal or a salt thereof, and an organic compound.

[0097] Suitably, the alkali metal is potassium. Thus, in one embodiment, the catalyst precursor comprises iron or a salt or an oxide thereof; at least one additional transition metal selected from Mn, Zn, Cu, and Co, or a salt or an oxide thereof; potassium or a salt thereof; and a complexing agent.

[0098] In another embodiment, the catalyst precursor comprises iron or a salt, an oxide, or a hydroxide thereof; at least one additional transition metal or a salt, an oxide, or a hydroxide thereof selected from Mn and Co; potassium or a salt thereof; and a complexing agent.

[0099] In another embodiment, the catalyst precursor comprises iron or a salt, an oxide, or a hydroxide thereof; at least one additional transition metal or a salt, an oxide, or a hydroxide thereof selected from Mn and Co; potassium or a salt thereof; and an organic compound.

[0100] Suitably, the complexing agent or the organic compound is as defined in one of the foregoing embodiments. Suitably, the cobalt salt is cobalt nitrate. Suitably, the manganese salt is manganese nitrate.

[0101] In one embodiment, the catalyst precursor comprises iron(II or III) nitrate, manganese(II) nitrate, potassium carbonate, and citric acid. In another embodiment, the catalyst precursor consists essentially of iron(II or III) nitrate, manganese(II) nitrate, potassium carbonate, and citric acid.

[0102] In another embodiment, the catalyst precursor comprises iron powder, manganese(II) nitrate, cobalt nitrate, sodium carbonate, and citric acid. In another embodiment, the catalyst precursor consists essentially of iron powder, manganese(II) nitrate, cobalt nitrate, sodium carbonate, and citric acid.

[0103] In one embodiment, the catalyst precursor comprises (i) Fe or a salt thereof, (ii) Mn or a salt thereof, (iii) K or a salt thereof, and (iv) citric acid or a salt thereof.

[0104] In one embodiment, the catalyst precursor comprises (i) Fe or a salt thereof, (ii) Mn or a salt thereof, (iii) Co or a salt thereof, (iii) K or a salt thereof, and (iv) citric acid or a salt thereof.

[0105] Suitably, the molar ratio of Fe:Mn is from about 100:1 to about 4:1, more suitably from about 15:1 to about 5:1.

[0106] Suitably, the molar ratio of Fe:K is from about 100:1 to about 2:1; more suitably, the molar ratio of Fe:K is from about 20:1 to about 4:1, more suitably from about 10:1 to about 2:1.

[0107] Suitably, the molar ratio of (Fe + Mn + K)∶citric acid is from about 5∶1 to 0.5∶1, suitably from about 2∶1 to about 1∶1.

[0108] Suitably, the molar ratio of Fe∶Co is from about 40∶1 to about 10∶1, more suitably from about 30∶1 to about 10∶1, more suitably about 20∶1.

[0109] Method for preparing a catalyst precursor

[0110] In a second aspect, the present invention relates to a method for preparing a catalyst precursor, which comprises:

[0111] (a) combining (i) at least one iron substance, (ii) an alkali metal or its salt, (iii) a complexing agent, and (iv) a solvent;

[0112] (b) stirring the mixture of step (a) to provide a homogeneous mixture;

[0113] (c) heating the mixture of step (b) to partially remove the solvent, thereby providing a slurry or paste.

[0114] In this aspect, the iron substance, the alkali metal or its salt, and the complexing agent may be defined as in any of the foregoing embodiments.

[0115] In one embodiment, the solvent comprises water. Suitably, the solvent is water.

[0116] Step (a) may further comprise adding one or more additional metal substances, suitably additional transition metal substances. In one embodiment, an additional transition metal selected from Mn, Zn, Co, and Cu, or its salt, its oxide, or its hydroxide is incorporated in step (a).

[0117] In step (b), the mixture may be stirred by any means known in the art such as stirring, shaking, vortexing, and sonication.

[0118] In step (c), the mixture is suitably heated to a temperature of about 30°C to 120°C, more suitably about 30°C to about 80°C, more suitably about 50°C.

[0119] The method may further comprise an additional step (d): wherein the slurry or paste of step (c) is calcined to provide a powder. Suitably, the calcination is carried out at a temperature of about 300°C to about 500°C, more suitably about 350°C. Suitably, the calcination is carried out in air, suitably in static air. Generally, the calcination will cause the combustion of the organic components of the precursor.

[0120] The method may further comprise step (e): wherein the calcined powder is, for example, ground or milled to reduce the particle size.

[0121] In another aspect, the present invention relates to a method for preparing a catalyst precursor, the method comprising:

[0122] (a) combining (i) iron powder, (ii) an alkali metal or its salt, and (iii) a complexing agent; and

[0123] (b) stirring the mixture of step (a) to provide a homogeneous mixture.

[0124] In one embodiment, step (a) may further include adding one or more additional metal substances. In one embodiment, at least one additional transition metal selected from Mn, Zn, Co, and Cu, or its salt, its oxide, or its hydroxide is incorporated in step (a). Suitably, Mn or its salt, its oxide, or its hydroxide and Co or its salt, its oxide, or its hydroxide are further incorporated in step (a).

[0125] In step (b), the stirring can be carried out by any means known in the art, such as stirring, shaking, milling, and grinding.

[0126] In one embodiment, the method for preparing a catalyst precursor comprises:

[0127] (a) combining: (i) iron powder; (ii) potassium, sodium, or lithium, or its salt; (iii) citric acid; and (iv) at least one additional transition metal selected from Mn and Co, or its salt, its oxide, or its hydroxide; and

[0128] (b) stirring the mixture of step (a) to provide a homogeneous mixture.

[0129] Catalyst and method for preparing the same

[0130] In another aspect, the present invention relates to a catalyst obtainable by activating a catalyst precursor obtainable according to the method described herein, or a catalyst obtainable by activating a catalyst precursor described herein.

[0131] Suitably, the catalyst is suitable for the hydrogenation of carbon dioxide and / or carbon monoxide.

[0132] In one embodiment, the catalyst comprises iron carbide, suitably Fe5C2.

[0133] In one embodiment, the catalyst comprises iron carbide; at least one additional transition metal selected from Mn, Zn, Cu, and Co, or its salt, its oxide, or its hydroxide; and an alkali metal or its salt.

[0134] In one embodiment, the catalyst comprises iron carbide; at least one additional transition metal or salt, oxide or hydroxide selected from Mn and Co; and an alkali metal or a salt thereof.

[0135] In another embodiment, the catalyst precursor comprises iron carbide; manganese or an oxide thereof; and an alkali metal.

[0136] In another embodiment, the catalyst comprises iron carbide; manganese or an oxide thereof; cobalt or an oxide thereof; and an alkali metal.

[0137] Suitably, the alkali metal is potassium.

[0138] In another embodiment, the catalyst comprises iron carbide; at least one additional transition metal or an oxide thereof selected from Mn and Co; and potassium.

[0139] Suitably, the iron carbide is Fe5C2.

[0140] Suitably, the molar ratio of Fe:Mn is from about 100:1 to about 4:1, more suitably from about 15:1 to about 5:1.

[0141] Suitably, the molar ratio of Fe:K is from about 100:1 to about 2:1; more suitably, the molar ratio of Fe:K is from about 20:1 to about 4:1, more suitably from about 10:1 to about 2:1.

[0142] Suitably, the molar ratio of Fe:Co is from about 40:1 to about 10:1, more suitably from about 30:1 to about 10:1, more suitably about 20:1.

[0143] In another aspect, the present invention relates to a method for preparing a catalyst, the method comprising:

[0144] (a) providing a catalyst precursor as defined in any of the above embodiments;

[0145] (b) optionally calcining the catalyst precursor; and

[0146] (c) activating the precursor.

[0147] In one embodiment, the catalyst is suitable for the hydrogenation of carbon dioxide and / or carbon monoxide.

[0148] Suitably, the calcination is carried out at a temperature of from about 100 °C to about 500 °C, or from about 250 °C to about 500 °C, more suitably from about 300 °C to about 350 °C. Suitably, the calcination is carried out in air, suitably in static air. Generally, the calcination will result in the decomposition or partial combustion of the organic components of the precursor.

[0149] Step (b) may also include grinding or milling the calcined powder to reduce the particle size.

[0150] The calcined material of step (b) or the precursor of step (a) can be activated, for example, by reduction. Suitably, the material to be activated is exposed to a mixture of CO and hydrogen at a temperature of about 250 °C to about 500 °C, more suitably about 300 °C to about 350 °C.

[0151] Method for the hydrogenation of CO2 or CO

[0152] In one aspect, the present invention relates to a method for the hydrogenation of carbon dioxide, the method comprising: contacting a feedstock comprising hydrogen and carbon dioxide with a catalyst precursor or a catalyst as defined herein at elevated temperature and pressure.

[0153] In another aspect, the present invention relates to a method for the hydrogenation of carbon monoxide, the method comprising: contacting a feedstock comprising hydrogen and carbon monoxide with a catalyst precursor or a catalyst as defined herein at elevated temperature and pressure.

[0154] In another aspect, the present invention relates to a method for producing olefins, the method comprising: contacting a feedstock comprising (i) hydrogen and (ii) carbon dioxide and / or carbon monoxide with a catalyst precursor or a catalyst as defined herein at elevated temperature and pressure.

[0155] Suitably, the olefin is a C5+ olefin, or an α-olefin, or a linear olefin. More suitably, the olefin is a C5+ α-olefin. Suitably, the olefin is a linear α-olefin. More suitably, the olefin is a C5+ linear α-olefin.

[0156] Suitably, the olefin is a C 5-16 olefin. More suitably, the olefin is a C 5-16 α-olefin. More suitably, the olefin is a C 5-16 linear α-olefin.

[0157] In another aspect, the present invention relates to a method for producing hydrocarbons, the method comprising: contacting a feedstock comprising (i) hydrogen and (ii) carbon dioxide and / or carbon monoxide with a catalyst precursor or a catalyst as defined herein at elevated temperature and pressure.

[0158] Suitably, the hydrocarbon is a C5+ hydrocarbon, more suitably a C8 to C 18 hydrocarbon, more suitably a C8 to C 16 hydrocarbon. In one embodiment, the hydrocarbon is a C8 to C 18 alkane, more suitably a C8 to C 16 alkane. In one embodiment, the hydrocarbon is a hydrocarbon in the jet engine fuel range.

[0159] In another aspect, the present invention relates to a method for producing fuel, the method comprising contacting a feedstock comprising (i) hydrogen and (ii) carbon dioxide and / or carbon monoxide with a catalyst precursor or catalyst as defined herein at elevated temperature and pressure.

[0160] Suitably, the fuel is selected from gasoline, diesel and aviation / jet engine fuel.

[0161] In the case of carbon monoxide or carbon dioxide hydrogenation or olefin production, the catalyst or catalyst precursor is charged to the reaction zone. The catalyst is activated ex-situ (e.g. by heating, or if desired, by oxidation and subsequent reduction with syngas or hydrogen). The catalyst precursor can be activated in-situ, for example, under the reaction conditions.

[0162] The catalyst can be used in a fixed bed, moving bed, ebullated bed, fluidized bed or slurry bed reactor. Suitably, the catalyst is used in a fixed bed reactor.

[0163] In one embodiment, when CO hydrogenation is desired, a feedstock comprising a mixture of hydrogen and carbon monoxide having a suitable H2:CO molar ratio is contacted with a catalyst bed and reacted under reaction conditions. Generally, the molar ratio of H2:CO ranges from about 0.4:1 to about 6:1, suitably from about 0.5:1 to about 3:1, more suitably from about 1:1 to about 2:1.

[0164] In another embodiment, when CO2 hydrogenation is desired, a feedstock comprising a mixture of hydrogen and carbon dioxide having a suitable H2:CO2 molar ratio is contacted with a catalyst bed and reacted under reaction conditions. Generally, the molar ratio of H2:CO2 ranges from about 0.4:1 to about 8:1, suitably from about 0.4:1 to about 6:1, suitably from about 0.5:1 to about 5:1, more suitably from about 1:1 to about 4:1. Suitably, the molar ratio of H2:CO2 ranges from about 0.5:1 to about 4:1, more suitably from about 1:1 to about 3:1.

[0165] The reaction temperature is elevated. As used herein, elevated temperature is a temperature elevated relative to standard ambient temperature (i.e. a temperature of 298.15 K (25 °C)). In one embodiment, the feedstock is contacted with the catalyst precursor or catalyst at a temperature of about 180 °C to about 500 °C, suitably about 250 °C to about 500 °C, more suitably about 280 °C to about 350 °C, or about 300 °C to about 350 °C.

[0166] The reaction pressure is increased. As used herein, an increased pressure is a pressure increased relative to standard ambient pressure (i.e., a pressure of 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm)). In one embodiment, the feedstock is contacted with the catalyst precursor or the catalyst at a pressure of about 500 kPa to about 10 MPa, suitably about 500 kPa to about 5 MPa, suitably about 500 kPa to about 2 MPa, suitably about 1 MPa.

[0167] The present invention will now be further described by the following numbered paragraphs:

[0168] 1. A catalyst precursor comprising an iron substance (suitably iron or its salts, its oxides or its hydroxides), an alkali metal or its salts, and a complexing agent.

[0169] 2. The catalyst precursor according to paragraph 1, wherein the complexing agent comprises one or more functional groups selected from carboxylic acid, hydroxyl, amide or amino groups.

[0170] 3. The catalyst precursor according to paragraph 1, wherein the complexing agent comprises one or more functional groups selected from carboxylic acid, hydroxyl, and amide groups.

[0171] 4. The catalyst precursor according to paragraph 1, wherein the complexing agent is selected from hydroxycarboxylic acids, aminocarboxylic acids and polycarboxylic acids, or their salts.

[0172] 5. The catalyst precursor according to paragraph 1, wherein the complexing agent is selected from glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxypentanoic acid, malic acid, mandelic acid, citric acid, saccharic acid, tartronic acid, tartaric acid, oxalic acid, malonic acid, maleic acid, tannic acid, succinic acid, salicylic acid, glutaric acid, adipic acid, glycine, hippuric acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), alanine, valine, leucine and isoleucine, and their salts.

[0173] 6. The catalyst precursor according to paragraph 1, wherein the complexing agent is selected from citric acid, tartaric acid, oxalic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), or their salts.

[0174] 7. The catalyst precursor according to any one of the preceding paragraphs, wherein the complexing agent is citric acid and / or its salts.

[0175] 8. The catalyst precursor according to any one of the preceding paragraphs, wherein the alkali metal is selected from potassium, sodium, lithium and cesium.

[0176] 9. The catalyst precursor according to any one of the preceding paragraphs, wherein the alkali metal is selected from potassium, sodium and cesium.

[0177] 10. The catalyst precursor according to any one of the preceding paragraphs, wherein the alkali metal is potassium.

[0178] 11. The catalyst precursor according to any one of the preceding paragraphs, wherein the iron substance is iron nitrate, suitably iron(II) nitrate or iron(III) nitrate.

[0179] 12. The catalyst precursor according to any one of paragraphs 1 to 10, wherein the iron substance is selected from elemental iron, iron oxide, iron salt or iron hydroxide, suitably, wherein the iron substance is iron powder.

[0180] 13. The catalyst precursor according to any one of the preceding paragraphs, comprising an additional metal substance.

[0181] 14. The catalyst precursor according to paragraph 13, wherein the additional metal substance is present in an amount of about 1 wt% to about 20 wt%.

[0182] 15. The catalyst precursor according to any one of the preceding paragraphs, further comprising one or more transition metals selected from Mn, Zn, Co and Cu, or salts, oxides or hydroxides thereof.

[0183] 16. The catalyst precursor according to paragraph 15, wherein the transition metal is selected from Mn and Co, or salts, oxides or hydroxides thereof.

[0184] 17. The catalyst precursor according to any one of the preceding paragraphs, comprising (i) Fe or a salt thereof, (ii) Mn or a salt thereof, (iii) K or a salt thereof, and (iv) citric acid or a salt thereof.

[0185] 18. The catalyst precursor according to paragraph 17, further comprising (v) Co or a salt thereof.

[0186] 19. The catalyst precursor according to any one of paragraphs 1 to 11 and 13 to 17, comprising iron(III) nitrate, manganese(II) nitrate, potassium carbonate and citric acid.

[0187] 20. The catalyst precursor according to any one of paragraphs 1 to 10 and 12 to 18, comprising iron powder, manganese(II) nitrate, cobalt nitrate, sodium carbonate and citric acid.

[0188] 21. The catalyst precursor according to any one of the preceding paragraphs, wherein the molar ratio of Fe:alkali metal is from about 100:1 to about 4:1, suitably from about 20:1 to about 4:1, more suitably about 10:1.

[0189] 22. A catalyst precursor according to any one of the preceding paragraphs, wherein the molar ratio of the complexing agent to Fe is from about 1:1 to about 3:1.

[0190] 23. A catalyst precursor according to any one of paragraphs 15 to 20, wherein the molar ratio of Fe:Mn is from about 100:1 to about 4:1, suitably about 10:1.

[0191] 24. A catalyst precursor according to any one of paragraphs 15 to 20, wherein the molar ratio of (Fe + Mn + K):citric acid is from about 5:1 to about 0.5:1, suitably from about 2:1 to about 1:1.

[0192] 25. A catalyst precursor according to any one of paragraphs 15, 16, 18 and 20, wherein the molar ratio of Fe:Co is from about 40:1 to about 10:1, more suitably from about 30:1 to about 10:1, more suitably about 20:1.

[0193] 26. A method for preparing a catalyst precursor, comprising:

[0194] (a) combining (i) an iron substance (suitably iron or its salt, its oxide or its hydroxide), (ii) an alkali metal or its salt, (iii) a complexing agent, and (iv) a solvent;

[0195] (b) stirring the mixture of step (a) to provide a homogeneous mixture;

[0196] (c) heating the mixture of step (b) to partially remove the solvent, thereby providing a slurry or paste.

[0197] 27. The method according to paragraph 26, wherein step (a) further comprises incorporating one or more transition metals selected from Mn, Zn, Co and Cu, or their salts, their oxides or their hydroxides.

[0198] 28. The method according to any one of paragraphs 26 to 27, wherein step (a) comprises combining (i) Fe or its salt, (ii) Mn or its salt, (iii) K or its salt, and (iv) citric acid or its salt.

[0199] 29. The method according to any one of paragraphs 26 to 28, wherein the iron substance in step (a) is iron(III) nitrate.

[0200] 30. The method according to any one of paragraphs 26 to 29, wherein step (a) comprises combining iron(III) nitrate, manganese(II) nitrate, potassium carbonate and citric acid.

[0201] 31. A method according to any one of paragraphs 26 to 30, wherein step (a) comprises combining iron(III) nitrate, manganese(II) nitrate, potassium carbonate, and citric acid with water.

[0202] 32. A method according to paragraph 28, wherein the weight ratio of (i) to (iv) in step (a) to the solvent is from about 3:1 to about 1:3, suitably about 2:1.

[0203] 33. A method according to any one of paragraphs 26 to 32, further comprising (d): calcining the paste or slurry of step (c) to provide a powder.

[0204] 34. A method according to paragraph 33, wherein the calcination is carried out at a temperature of from about 100 °C to about 500 °C, suitably from about 250 °C to about 500 °C, suitably from about 300 °C to about 350 °C.

[0205] 35. A method according to any one of paragraphs 33 and 34, wherein the calcination is carried out in air or an inert atmosphere, suitably in static air.

[0206] 36. A method according to any one of paragraphs 33 to 35, further comprising (e): grinding the powder of step (d).

[0207] 37. A method for preparing a catalyst precursor, comprising:

[0208] (a) combining (i) iron powder, (ii) an alkali metal or its salt, and (iii) a complexing agent; and

[0209] (b) stirring the mixture of step (a) to provide a homogeneous mixture.

[0210] 38. A method according to paragraph 37, wherein step (a) further comprises adding one or more additional metal substances.

[0211] 39. A method according to any one of paragraphs 37 and 38, wherein step (a) further comprises incorporating Mn or its salt, its oxide or its hydroxide and Co or its salt, its oxide or its hydroxide.

[0212] 40. A method according to claim 37, comprising:

[0213] (a) combining: (i) iron powder; (ii) potassium, sodium or lithium, or their salts; (iii) citric acid; and (iv) at least one additional transition metal selected from Mn and Co, or their salts, their oxides or their hydroxides; and

[0214] (b) stirring the mixture of step (a) to provide a homogeneous mixture.

[0215] 41. A method according to any one of paragraphs 27 to 36 and paragraphs 38 to 40, wherein the molar ratio of Fe:Mn in step (a) is from about 100:1 to about 4:1, suitably about 10:1.

[0216] 42. A method according to any one of paragraphs 26 to 41, wherein the molar ratio of Fe:alkali metal in step (a) is from about 100:1 to about 4:1, suitably from about 20:1 to about 4:1.

[0217] 43. A method according to any one of paragraphs 28, 30 to 32, wherein the molar ratio of Fe:K in step (a) is about 10:1.

[0218] 44. A method according to paragraph 28, wherein the molar ratio of (Fe + Mn + K):citric acid in step (a) is from about 5:1 to 0.5:1, suitably from about 2:1 to about 1:1.

[0219] 45. A method according to any one of paragraphs 26 to 44, wherein the molar ratio of the complexing agent to Fe is from about 1:1 to about 3:1.

[0220] 46. A method according to any one of paragraphs 26 to 36, wherein step (c) comprises heating the mixture to about 30°C to 80°C, suitably about 50°C.

[0221] 47. A method according to any one of paragraphs 26 and 37, wherein the complexing agent is as described in any one of paragraphs 2 to 7.

[0222] 48. A method according to any one of paragraphs 26 and 37, wherein the alkali metal is as described in any one of paragraphs 8 to 10.

[0223] 49. A method according to paragraph 40, wherein step (a) comprises combining iron powder, manganese(II) nitrate, cobalt nitrate, sodium carbonate and citric acid.

[0224] 50. A catalyst obtainable by activating a catalyst precursor as defined in paragraphs 1 to 25, or obtainable by activating a catalyst precursor obtainable by a method according to any one of paragraphs 26 to 49.

[0225] 51. A method for preparing a catalyst, comprising:

[0226] (a) providing a catalyst precursor as defined in any one of paragraphs 1 to 25;

[0227] (b) optionally calcining the catalyst precursor; and

[0228] (c) activating the precursor.

[0229] 52. The method according to paragraph 51, wherein the calcination is carried out at a temperature of about 100 °C to about 500 °C, about 250 °C to about 500 °C, suitably about 300 °C to about 350 °C.

[0230] 53. The method according to any one of paragraphs 51 and 52, wherein the calcination is carried out in air or an inert atmosphere, suitably in static air.

[0231] 54. The method according to any one of paragraphs 51 to 53, wherein step (c) comprises reducing the precursor, suitably by exposure to CO and hydrogen.

[0232] 55. The method according to any one of paragraphs 51 to 54, further comprising (d): grinding or granulating the product of step (c).

[0233] 56. A catalyst obtainable by the method according to any one of paragraphs 51 to 55.

[0234] 57. A method for the hydrogenation of carbon dioxide, comprising: contacting a feedstock comprising hydrogen and carbon dioxide with a catalyst precursor according to paragraphs 1 to 25 or a catalyst according to any one of paragraphs 50 and 56 at elevated temperature and pressure.

[0235] 58. The method according to paragraph 57, wherein the catalyst precursor is the catalyst precursor according to paragraphs 11, 17 and 19.

[0236] 59. The method according to any one of paragraphs 57 and 58, wherein the molar ratio of hydrogen to carbon dioxide in the feedstock is from 0.4:1 to 6:1, suitably about 1:1 to about 3:1.

[0237] 60. A method for the hydrogenation of carbon monoxide, comprising: contacting a feedstock comprising hydrogen and carbon monoxide with a catalyst precursor according to paragraphs 1 to 25 or a catalyst according to any one of paragraphs 50 and 56 at elevated temperature and pressure.

[0238] 61. The method according to paragraph 60, wherein the catalyst precursor is the catalyst precursor according to paragraphs 12, 15 to 18 and 20.

[0239] 62. The method according to any one of paragraphs 60 and 61, wherein the molar ratio of hydrogen to carbon monoxide in the feedstock is from 0.4:1 to 6:1, suitably about 1:1 to about 2:1.

[0240] 63. A method for producing olefins, comprising: contacting a feedstock comprising hydrogen and carbon monoxide, or hydrogen and carbon dioxide, with a catalyst precursor according to paragraphs 1 to 25 or a catalyst according to any one of paragraphs 50 and 56 at elevated temperature and pressure.

[0241] 64. The method according to paragraph 63, wherein the molar ratio of H2:CO2 or H2:CO in the feedstock is from 0.4:1 to 6:1.

[0242] 65. The method according to any one of paragraphs 63 and 64, wherein the olefin is a C 5+ olefin, suitably a C 5+ α-olefin.

[0243] 66. The method according to paragraph 65, wherein the C 5+ olefin is a C 5-16 olefin or a C 5-16 α-olefin.

[0244] 67. The method according to any one of paragraphs 57 to 66, wherein the feedstock is contacted with the catalyst precursor or the catalyst at a temperature of about 100 °C to about 500 °C, suitably about 250 °C to about 500 °C, suitably about 300 °C to about 350 °C.

[0245] 68. The method according to any one of paragraphs 57 to 67, wherein the feedstock is contacted with the catalyst precursor or the catalyst at a pressure of about 500 KPa to about 2 Mpa, suitably about 1 Mpa.

[0246] 69. The method according to any one of paragraphs 57 to 68, wherein the feedstock is contacted with the catalyst precursor or the catalyst at a GHSV (gas hourly space velocity) of about 100 hours -1 to about 20,000 hours -1 , suitably about 1000 hours -1 to about 5000 hours -1 .

[0247] 70. A heterogeneous mixture comprising a catalyst precursor according to any one of paragraphs 1 to 25 or a catalyst according to any one of paragraphs 50 and 56, and a gas containing hydrogen and carbon monoxide, or hydrogen and carbon dioxide.

[0248] Embodiment

[0249] 1. CO2 hydrogenation

[0250] All catalyst component materials were obtained from the commercial sources shown below and used without further modification.

[0251] A general method for preparing a catalyst uses the organic combustion method. Usually, an iron salt, an alkali metal salt, and a complexing agent are mixed in a desired ratio and stirred in water to provide a homogeneous aqueous solution. The solution is heated at about 50 °C for 1 to 2 hours to obtain a slurry. Then the slurry is calcined in a furnace at about 350 °C in static air for 4 hours to provide a catalyst precursor.

[0252] For example, the preparation of an Fe-Mn-K catalyst involves mixing citric acid monohydrate with iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate, where the molar ratio of citric acid:(Fe + Mn + K) is about 2, and the weight ratio of (Fe precursor and Mn precursor and K precursor + citric acid) / water is about 2:1. The mixture is stirred to form a homogeneous aqueous solution and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste is calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0253] The carbon dioxide hydrogenation experiment was carried out in a fixed-bed reactor ( Figure 1 ). Usually, 1.0 g of the catalyst precursor was mixed with 4.0 g of silicon carbide and loaded into the reactor. Before the reaction, the catalyst precursor was reduced in syngas (H2:CO = 2:1) at atmospheric pressure, where the GHSV (gas hourly space velocity) was 1000 mL / g h, at 320 °C for 24 hours, with a heating rate of 2 °C / min, to provide an activated catalyst.

[0254] After reduction, the temperature was lowered to about 50 °C, and a mixture of H2 / CO2 (3:1) and N2 (as an internal standard) was used as the feed gas. The gas flow rate was set at 40 mL / min (GSVH = 2400 mL / g catalyst). N2 was added as an inert gas to the syngas feed for conversion calculation. Since the mass flow rate of N2 did not change before and after the reaction, the CO2 and H2 conversion rates, CO and C n H m selectivity can be calculated as described below.

[0255] The reactor was heated at a rate of 2 °C / min until the reaction temperature (about 300 °C to 320 °C). The reaction pressure was controlled at 10 bar (1 Mpa) by a back pressure regulator.

[0256] The gas products were analyzed on a Perkin Elmer Clams GC, and the collected liquid products were analyzed by GC-MS.

[0257] The conversion rates of CO2 and H2 and the product selectivities were calculated by the following equations:

[0258]

[0259]

[0260]

[0261]

[0262]

[0263] Table 1 provides examples of Fe-Mn-K catalysts with different Fe∶Mn∶K ratios prepared as described above using citric acid as a complexing agent. After a reaction time of 20 hours as described above, the conversions of H2 and CO2 and the product selectivities for different catalysts are shown in Table 1.

[0264] Table 1

[0265]

[0266] Table 2 and Figure 2 provides the molar ratio of olefins to paraffins of the C2 to C4 hydrocarbons produced.

[0267] Table 2

[0268]

[0269] Table 2 and Figure 2 shows that in the liquid product, the catalyst shows higher selectivity for olefins relative to paraffins. The GC-MS spectrum of the liquid product shows that the products are concentrated in C6 to C 16 hydrocarbons, and the main peak is attributed to linear α-olefins.

[0270] The XRD patterns of each catalyst were recorded on a Bruker D8 ECO X-ray diffractometer using graphite-monochromated Cu Kα radiation (λ = 0.15418 nm, in the 2θ range from 20° to 80°, at a scanning rate of 0.02° / s). Most of the peaks can be attributed to Fe3O4.

[0271] Based on the peak at 2θ = 35.9°, the crystallite size was calculated using the Debye-Scherrer formula:

[0272]

[0273] where β is the full width at half maximum (FWHM) value of the XRD diffraction line, the wavelength λ = 0.15418 nm, and θ is half of the diffraction angle 2θ. The catalyst shows a small crystallite size of about 10 nm (Table 3), which is consistent with the broad peaks in the XRD spectrum ( Figure 3 ).

[0274] Table 3

[0275]

[0276] To study the effects of various promoters on CO2 hydrogenation, iron-based catalysts were prepared with potassium and various promoters. The catalysts were prepared using an organic combustion method similar to the above-mentioned organic combustion method with citric acid as a complexing agent. The catalyst precursors of the catalysts studied in Table 4 were prepared as follows:

[0277] Example 4: Citric acid monohydrate and iron(III) nitrate nonahydrate in a molar ratio of 2:1 were dissolved in water to form a homogeneous aqueous solution (the weight ratio of (iron(III) nitrate nonahydrate + citric acid monohydrate) to water was about 2:1), and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0278] Example 5: Citric acid monohydrate, iron(III) nitrate nonahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:K was 100:10, the molar ratio of citric acid:(Fe + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + potassium carbonate + citric acid) / water was about 2:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0279] Example 6: Citric acid monohydrate, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of citric acid:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + citric acid) / water was about 2:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0280] Example 7: Citric acid monohydrate, iron(III) nitrate nonahydrate, zinc(II) nitrate hexahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Zn:K was 100:10:10, the molar ratio of citric acid:(Fe + Zn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + zinc(II) nitrate hexahydrate + potassium carbonate + citric acid) / water was about 2:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0281] Example 8: Citric acid monohydrate, iron(III) nitrate nonahydrate, copper(II) nitrate trihydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Cu∶K was 100∶10∶10, the molar ratio of citric acid∶(Fe + Cu + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + copper(II) nitrate trihydrate + potassium carbonate + citric acid) / water was about 2∶1. The mixture was stirred and heated at 50 °C for 1 hour to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a catalyst powder.

[0282] The catalytic performance was evaluated in the CO2 hydrogenation as described above with a reaction time of 20 hours.

[0283] Table 4 shows the effect of including a transition metal (TM) promoter in the catalyst. Catalysts were prepared using citric acid as a complexing agent, with a K∶Fe and TM∶Fe molar ratio of 1∶10 where applicable. In Table 4, the column headings for hydrocarbons have the following meanings: C 2-4 =: C2 to C4 olefins, C 2-4 0: C2 to C4 alkanes; C 5+ : liquid products; C 5-16 =: C5 to C 16 olefins.

[0284] Table 4

[0285]

[0286] Table 5 provides the molar ratio of olefins to alkanes of the produced C2 to C4 hydrocarbons.

[0287] Table 5

[0288]

[0289] The XRD pattern of each catalyst was recorded on a Bruker D8 ECO X-ray diffractometer using graphite-monochromated Cu Kα radiation (λ = 0.15418 nm, in the 2θ range from 10° to 90°, at a scanning rate of 0.02° / s) Figure 4 ), and the crystallite size was calculated using the Debye-Scherrer formula as described above. The catalysts showed different crystallite sizes (Table 6).

[0290] Table 6

[0291]

[0292] To study the influence of various alkali metals on the hydrogenation of CO2, iron-based catalysts were prepared with a manganese promoter and alkali metals varied between Na, K, and Cs. The catalysts were prepared using an organic combustion method similar to the above-mentioned organic combustion method. The catalyst precursors of the catalysts studied in Table 7 were prepared as follows:

[0293] Example 9: Citric acid monohydrate, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶Na was 100∶10∶10, the molar ratio of citric acid∶(Fe + Mn + Na) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + sodium carbonate + citric acid) / water was about 2∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0294] Example 10: Citric acid monohydrate, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of citric acid∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + citric acid) / water was about 2∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a catalyst powder.

[0295] Example 11: Citric acid monohydrate, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and cesium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶Cs was 100∶10∶10, the molar ratio of citric acid∶(Fe + Mn + Cs) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + cesium carbonate + citric acid) / water was about 2∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0296] The catalytic performance was evaluated in the CO2 hydrogenation as described above with a reaction time of 20 hours.

[0297] Table 7 shows the effect of including an alkali metal (AM) in the catalyst. The catalysts were prepared using citric acid as a complexing agent, and the catalysts had a molar ratio of AM∶Fe and Mn∶Fe of 1∶10. In Table 7, the column headings for hydrocarbons have the following meanings: C 2-4=: C2 to C4 olefins, C 2-4 0: C2 to C4 alkanes; C 5+ : Liquid product; C 5-16 =: C5 to C 16 olefins.

[0298] Table 7

[0299]

[0300] Table 8 provides the olefin:alkane molar ratio of the C2 to C4 hydrocarbons produced.

[0301] Table 8

[0302]

[0303] The XRD patterns of each catalyst were recorded on a Bruker D8 ECO X-ray diffractometer using graphite-monochromated Cu Kα radiation (λ = 0.15418 nm, in the 2θ range from 10° to 90°, at a scanning rate of 0.02° / s) Figure 5 ), and the crystallite size was calculated using the Debye-Scherrer formula as described above. The catalysts showed different crystallite sizes (Table 9).

[0304] Table 9

[0305]

[0306] To study the effect of the complexing agents used in the preparation of the catalysts on the catalyst performance, a series of iron-based catalysts were prepared using various complexing agents. The catalysts contained potassium and manganese in a molar ratio of 1:10 relative to Fe. The catalysts were prepared using an organic combustion method similar to the above-described organic combustion method. The catalyst precursors of the catalysts studied in Table 10 were prepared as follows:

[0307] Example 12 (reference): Iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate) / water was approximately 2:1. The mixture was stirred and heated at 50 °C for 1 h to 2 h to obtain an anhydrous mixture. The mixture was calcined in static air at 350 °C (furnace temperature) for 4 h to produce a powder.

[0308] Example 13: Urea, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution in which the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of urea∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + urea) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a urea-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0309] Example 14: Tannic acid, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution in which the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of tannic acid∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + tannic acid) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a tannic acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0310] Example 15: Ethylenediaminetetraacetic acid (EDTA), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution in which the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of EDTA∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + EDTA) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain an EDTA-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0311] Example 16: Citric acid, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution in which the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of citric acid∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + citric acid) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a catalyst powder.

[0312] Example 17: Glycine, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of glycine∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + glycine) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a glycine-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0313] Example 18: Oxalic acid, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of oxalic acid∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + oxalic acid) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain an oxalic acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0314] Example 19: Nitrilotriacetic acid (NTA), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of NTA∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + NTA) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain an NTA-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0315] Example 20: Diethylenetriaminepentaacetic acid (DTPA), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe∶Mn∶K was 100∶10∶10, the molar ratio of DTPA∶(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + DTPA) / water was about 1∶1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a DTPA-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0316] Example 21: Tartaric acid, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of tartaric acid:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + tartaric acid) / water was about 1:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a tartaric acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0317] Example 22: Hydroxyethyl ethylenediaminetriacetic acid (HEDTA), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of HEDTA:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + HEDTA) / water was about 1:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a HEDTA-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0318] Example 23: Salicylic acid, iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of salicylic acid:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + salicylic acid) / water was about 1:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a salicylic acid-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0319] Example 24: Sugar (commercial granulated sugar), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous solution, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of sugar:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + sugar) / water was about 1:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a sugar-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0320] Example 25: Flour (commercial white wheat flour (plain flour or self-raising flour)), iron(III) nitrate nonahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were dissolved in water to form a homogeneous aqueous slurry, where the molar ratio of Fe:Mn:K was 100:10:10, the molar ratio of flour:(Fe + Mn + K) was about 2, and the weight ratio of (iron(III) nitrate nonahydrate + manganese(II) nitrate tetrahydrate + potassium carbonate + flour) / water was about 1:1. The mixture was stirred and heated at 50 °C for 1 to 2 hours to obtain a flour-based slurry. The paste was calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0321] The catalyst performance was evaluated in the CO2 hydrogenation as described above with a reaction time of 20 hours.

[0322] Table 10 shows the effect of the complexing agent used in the preparation of the catalyst on the performance. In Table 10, the column headings for hydrocarbons have the following meanings: C 2-4 =: C2 to C4 olefins, C 2-4 0: C2 to C4 alkanes; C 5+ : liquid products; C 5-16 =: C5 to C 16 olefins.

[0323] Table 10

[0324]

[0325] Table 11 provides the molar ratio of olefins to alkanes of the produced C2 to C4 hydrocarbons.

[0326] Table 11

[0327]

[0328] The XRD patterns of each catalyst were recorded on a Bruker D8 ECO X-ray diffractometer using graphite-monochromated Cu Kα radiation (λ = 0.15418 nm, in the 2θ range from 10° to 90°, at a scanning rate of 0.02° / s) Figure 6 and 7 ), and the crystallite size was calculated using the Debye-Scherrer formula as described above. The catalysts showed different crystallite sizes (Table 12).

[0329] Table 12

[0330]

[0331] Iron-based catalysts prepared with complexing agents and addition of Na, K, and / or Cs improve the selectivity for olefin production in the CO2 hydrogenation reaction. Further addition of Mn, Zn, and / or Cu promoters also shows high selectivity for olefins relative to alkanes. Different organic compounds are used as complexing agents during catalyst preparation. Catalysts prepared with citric acid, EDTA, oxalic acid, NTA, DTPA, tartaric acid, and HEDTA show the highest selectivity for olefins. The catalysts can also be used for the production of fuels (gasoline, diesel, aviation fuel / jet engine fuel) via hydrogenation of CO2 and / or CO.

[0332] 2. CO hydrogenation

[0333] All catalyst component materials are obtained from the commercial sources shown below and used without further modification.

[0334] Generally, iron powder is used as the iron source to prepare the catalyst. Iron powder, cobalt nitrate, manganese nitrate, and alkali metal salts (such as potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate) are mixed together, the mixture is ground evenly, the complexing agent (citric acid) is added (appropriately at a weight ratio of about 1:1 to iron) to the mixture, and the mixture is ground evenly again. The obtained mixture is dried at 80 °C for 24 hours. The dried mixture (uncalcined) is ground into powder to provide the catalyst precursor.

[0335] Before the reaction, the catalyst precursor is reduced in syngas (H2:CO = 2:1 or 1:1) at atmospheric pressure, where the GHSV (gas hourly space velocity) is 1000 mL / g h, at 320 °C for 32 hours, with a heating rate of 5 °C / min to provide the activated catalyst.

[0336] After reduction, the temperature is lowered to less than 50 °C, and a mixture of H2 / CO (1:1) and N2 (as an internal standard) is used as the feed gas. The gas flow rate is set at 40 mL / min (GSVH = 2400 mL / g catalyst). N2 is added as an inert gas to the syngas feed for conversion calculation. Since the mass flow rate of N2 does not change before and after the reaction, the conversions of CO and H2, and the selectivities of CO2 and C n H m selectivity can be calculated as described below.

[0337] The reactor ( Figure 1 ) is heated at a rate of 2 °C / min until the reaction temperature (about 280 °C to 320 °C). The reaction pressure is controlled at 10 bar (1 Mpa) by a back pressure regulator.

[0338] The gas products are analyzed on a Perkin Elmer Clarus GC, and the collected liquid products are analyzed by GC-MS.

[0339] The conversion rates of CO and H2 and the product selectivity are calculated by the following equations:

[0340]

[0341]

[0342]

[0343]

[0344] Table 13 studied the effect of adding an additional transition metal cobalt to the Fe-Mn-Na catalyst. After the reaction as described above, the reaction time, H2 and CO conversion rates, and product selectivity for different catalysts are shown in Table 13.

[0345] The catalyst precursors of the catalysts studied in Table 13 were prepared as follows:

[0346] Examples 26 to 30: Iron powder, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Mn:Na of 100:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into powder.

[0347] Examples 31 to 35: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 10:2:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into powder.

[0348] Examples 36 to 44: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into powder.

[0349] Examples 45 to 50: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:8:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0350] Examples 51 to 55: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:10:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0351] Table 13

[0352]

[0353] Table 14 provides the molar ratio of olefins to paraffins of the produced C2 to C4 hydrocarbons.

[0354] Table 14

[0355]

[0356] Table 15 studied the effects of various alkali metals on CO hydrogenation. Iron-based catalysts were prepared with manganese and cobalt promoters and an alkali metal varied between Na, K, and Li. The catalysts were prepared using a method similar to the above method. The catalyst precursors of the catalysts studied in Table 15 were prepared as follows:

[0357] Examples 56 to 65: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and lithium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Li of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 1:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0358] Examples 66 to 70: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 1:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0359] Examples 71 to 76: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and potassium carbonate were mixed together in a molar ratio of Fe:Co:Mn:K of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 1:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0360] Table 15

[0361]

[0362] Table 16 provides the molar ratio of olefins to alkanes of the produced C2 to C4 hydrocarbons.

[0363] Table 16

[0364]

[0365] Table 17 investigated the effect of manganese loading on CO hydrogenation. Iron-based catalysts were prepared with manganese and cobalt promoters and sodium. The catalysts were prepared using a method similar to the above method. In particular, the precursors of the catalysts in Table 17 were prepared as follows:

[0366] Examples 76 to 80: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 1:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into a powder.

[0367] Examples 81 to 88: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:5:20:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 1:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into catalyst powder.

[0368] Table 17

[0369]

[0370] Table 18 provides the molar ratio of olefins to paraffins of the produced C2 to C4 hydrocarbons.

[0371] Table 18

[0372]

[0373] Table 19 investigated the effect of feedstock composition on CO hydrogenation. Iron-based catalysts were prepared with manganese and cobalt promoters and sodium. Catalysts were prepared using a method similar to the above method. Reactions were carried out using syngas with different ratios of H2:CO.

[0374] The precursors of the catalysts in Table 19 were prepared as follows:

[0375] Examples 89 to 110: Iron powder, cobalt(II) nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and sodium carbonate were mixed together in a molar ratio of Fe:Co:Mn:Na of 100:5:10:2. The mixture was ground evenly. Citric acid was added to the mixture, and the mixture was ground evenly again, where the weight ratio of citric acid to iron powder was 4:1. The obtained mixture was dried at 80 °C for 24 hours. The dried mixture (uncalcined) was ground into powder.

[0376] Table 19

[0377]

[0378] Table 20 provides the molar ratio of olefins to paraffins of the produced C2 to C4 hydrocarbons.

[0379] Table 20

[0380]

[0381] Tables 21 and 22 investigated CO hydrogenation using an Fe-Co-Mn-Na catalyst (100:5:20:2) under various conditions. The GC-MS spectrum of the product curve of Example 111 is shown in Figure 8 in.

[0382] Table 21

[0383]

[0384] Table 22

[0385]

[0386] Iron powder is used as an iron source together with a complexing agent for the preparation of a catalyst. The preparation does not require calcination, thus saving energy and reducing emissions. The prepared catalyst exhibits high CO conversion, low CH4 selectivity, high olefin selectivity and stability. The addition of alkali metals and optionally transition metals (such as Co, Mn) improves the olefin selectivity in the gas and liquid products. In the case of a relatively high H2:CO molar ratio in the feedstock, the catalyst can also be used for the production of fuels (gasoline, diesel, aviation fuel / jet fuel).

[0387] The catalyst prepared for CO2 hydrogenation can also be used for CO hydrogenation and vice versa.

[0388] 3. Jet fuel production from CO2 hydrogenation

[0389] Jet fuel or aviation fuel is used in gas turbine engines to power aircraft. The main components of jet fuel are linear and branched alkanes and cycloalkanes, having a typical carbon chain length distribution of C8 to C 18 and preferably having a carbon chain length distribution of C8 to C 16 .

[0390] The catalysts disclosed herein are used to produce jet fuel range hydrocarbons in the CO2 hydrogenation product.

[0391] Catalyst preparation

[0392] The catalyst is prepared by the organic combustion method. The Fe-Mn-K catalyst precursor is prepared by mixing citric acid monohydrate (99%, Sigma-Aldrich) with iron(III) nitrate nonahydrate (98%, Sigma-Aldrich), manganese(II) nitrate tetrahydrate (97%, Sigma-Aldrich) and potassium nitrate (99%, Sigma-Aldrich). The molar ratio of citric acid:(Fe + Mn + K) is 2, and the weight ratio of (Fe precursor and Mn precursor and K precursor + citric acid):water is 2:1. The mixture is stirred to form a homogeneous aqueous solution and heated at 50 °C for 1 to 2 hours to obtain a citric acid-based slurry. The paste is calcined in static air at 350 °C (furnace temperature) for 4 hours to produce a powder.

[0393] Catalysts with different transition metal (Mn, Cu, Zn) promoters were also prepared using the same method. The catalysts Fe-Cu-K and Fe-Zn-K were prepared using transition metal precursors of copper(II) nitrate trihydrate (99% to 104%, Sigma-Aldrich) and zinc nitrate hexahydrate (98%, Sigma-Aldrich), respectively.

[0394] Catalysts of Fe-Mn-Li, Fe-Mn-Na, and Fe-Mn-Cs with different alkali metal promoters were prepared using precursors of lithium carbonate (99%, Sigma-Aldrich), sodium carbonate (99.6%, Acros Organics), and cesium carbonate (99%, Sigma-Aldrich), respectively.

[0395] In each case, the molar ratio of Fe∶transition metal∶alkali metal was 10∶1∶1.

[0396] The Fe-Mn-K catalyst was also prepared using organic compounds other than citric acid. The organic compounds used were urea (Bio-Reagent, Sigma-Aldrich), tannic acid (ACS reagent, Sigma-Aldrich), ethylenediaminetetraacetic acid (EDTA, 99.5%, Fisher Scientific), oxalic acid (99.0%, Sigma-Aldrich), nitrilotriacetic acid (NTA, 99%, Sigma-Aldrich), diethylenetriaminepentaacetic acid (DTPA, 98%, Sigma-Aldrich), tartaric acid (99.5%, Sigma-Aldrich), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA, 98%, Sigma-Aldrich), and salicylic acid (99.0%, Sigma-Aldrich). Unless otherwise stated, the catalyst was prepared using citric acid as the organic compound.

[0397] Catalyst performance evaluation

[0398] As described above, the CO2 hydrogenation experiment was carried out in a fixed-bed reactor. Before the reaction, the catalyst precursor was in-situ reduced with syngas (H2∶CO = 2∶1) at atmospheric pressure, where the GHSV (gas hourly space velocity) was 1000 mL g -1 hour -1 , for 24 hours at 320 °C. After the reactor temperature was cooled to below 50 °C, a mixture of a gas with an H2 / CO2 ratio of 3 and N2 (as an internal standard gas) was introduced into the reactor, and the gas flow rate was 40 mL min -1(GSVH = 2400 mL g -1 h -1 ). Heat the reactor at a heating rate of 2 °C / min until the reaction temperature (300 °C). The reaction pressure is fixed at 10 bar (1 Mpa) by a backpressure regulator.

[0399] Analyze the effluent gas products on an online gas chromatograph (Perkin Elmer Clarus 580 GC) equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD), and analyze the collected liquid products by a gas chromatography - mass spectrometer (SHIMADZU GCMS - QP2010SE).

[0400] Calculate the CO2 and H2 conversion rates and product selectivities as described above.

[0401] Characterization methods

[0402] Perform powder X - ray diffraction (XRD) analysis of the catalyst on a Bruker D8 Advance diffractometer using a Cu Kα (0.15418 nm) X - ray source (25 kV, 40 mA). Record the diffraction pattern in the 2θ angle range from 10° to 80° with a step size of 0.016°. Determine the microcrystalline size using the Scherrer equation.

[0403] Perform X - ray photoelectron spectroscopy (XPS) of the sample using a Thermo Fisher Scientific Nexsa spectrometer. Analyze the sample over an area of approximately 400 mm using a microfocused monochromatic Al X - ray source (72 W). Record the data for the full - spectrum scan at a pass energy of 150 eV and the high - resolution scan at a pass energy of 40 eV, with step sizes of 1 eV and 0.1 eV respectively. Achieve charge neutralization using a combination of low - energy electrons and argon ions. Analyze the resulting spectra using Casa XPS peak - fitting software and correct the sample charge using the C1s signal at 284.8 eV as a reference.

[0404] Characterize the morphology of the catalyst by scanning electron microscopy (SEM) on a scanning electron microscope (SEM, JEOL 840F).

[0405] Obtain high - resolution transmission electron microscopy (HRTEM) images in a probe - corrected JEOL ARM200F operated at 200 kV using a Gatan GIF Quantum 965ER spectrometer.

[0406] Catalytic performance of the Fe - Mn - K (10∶1∶1) catalyst for CO2 hydrogenation.

[0407] In the case of the Fe-Mn-K(10∶1∶1) catalyst prepared with citric acid as described above, the conversions of CO2 and H2 in terms of product selectivity are shown in Figure 9 as follows. Figure 9 It shows that the conversions of CO2 and H2 increase rapidly with reaction time within the first 5 hours and reach about 40%; from the start of the reaction until the reaction time of 20 hours, the methane selectivity decreases from 30% to 10%. In contrast, the selectivity of the liquid product (C 5+ ) remains stable at about 60% and shows a slight increase with reaction time.

[0408] The GC-MS spectra of the liquid products collected from CO2 hydrogenation are shown in Figure 10 as follows. Figure 10 It shows that the Fe-Mn-K catalyst has high selectivity for hydrocarbons in the jet engine fuel range in the liquid products, and the selectivity of the total hydrocarbons in the jet engine fuel range reaches 47.8%.

[0409] Catalyst Characterization

[0410] The powder X-ray diffraction (XRD) spectra of the above catalyst precursor, activated catalyst, and used catalyst are shown in Figure 11 as follows.

[0411] The surface elemental composition and oxidation state of the metals were analyzed in the range of 0 eV to 1350 eV using XPS. The measured spectra ( Figure 12 a) show that the sample contains Fe, Mn, K, and O. Figure 12 Figure b shows the XPS spectra in the Fe 2p range, which can be fitted with two spin-orbit doublets of the Fe 2p 3 / 2 and Fe2p 1 / 2 peaks and shakeup satellite peaks attributed to Fe 3+ , and these peaks are consistent with the reported Fe3O4. The molar ratio of Fe 2+ ∶Fe 3+ is 1∶2.34, which is very close to the stoichiometry of Fe3O4.

[0412] The scanning electron microscopy (SEM) images of the catalyst and used catalyst are shown in Figure 13 as follows. The catalyst precursor shows clearly stacked regular particles ( Figure 13 (a)), and the morphology of the catalyst changes significantly after use ( Figure 13 (b)), indicating that the surface of the catalyst changes before and after the reaction.

[0413] The high-resolution transmission electron microscopy (HRTEM) of the catalyst precursor and used catalyst are shown in Figure 14 as follows.Figure 14 a shows the particle size of the catalyst precursor (about 15 nm), and there is no obvious change in the particle size after the reaction ( Figure 14 d). The lattice spacings of 0.25 nm and 0.3 nm correspond to the (311) and (220) planes of Fe3O4 on the catalyst precursor, respectively. Figure 14 b and Figure 14 c). In addition to the Fe3O4 phase ( Figure 14 e), the Fe5C2 phase was also observed on the used catalyst ( Figure 14 f).

[0414] Effect of transition metals on the product curve

[0415] The catalysts Fe-Zn-K and Fe-Cu-K were prepared in the same way as the catalyst Fe-Mn-K. For different catalysts, the catalytic performance of CO2 hydrogenation is shown in Table 23. The molar ratio of K and Mn (Zn or Cu) to Fe is 1:10, and the data were obtained at a reaction time of 20 h.

[0416] Table 23

[0417]

[0418] C 2-4 =: C2 - C4 olefins, C 2-4 0: C2 - C4 alkanes; C 5+ : liquid products; C 8-16 : hydrocarbons in the jet engine fuel range.

[0419] Effect of alkali metals on the product curve

[0420] Different alkali metals were also used as promoters for the CO2 hydrogenation catalyst, and the catalytic performance is listed in Table 24. The molar ratio of alkali metal and Mn to Fe is 1:10, and the data were obtained at a reaction time of 20 h.

[0421] Table 24

[0422]

[0423] As can be seen from Table 24, Na, K, and Cs show both high activity for CO2 hydrogenation and high selectivity for the jet engine fuel range. Compared with the catalysts Fe-Mn-Na and Fe-Mn-Cs, the Fe-Mn-K catalyst shows slightly better performance in terms of CO2 conversion and target product selectivity.

[0424] Effect of organic compounds on the product curve

[0425] A series of Fe-Mn-K (molar ratio 10:1:1) catalysts prepared from different organic compounds were applied in catalyst preparation, and their catalytic performances in CO2 hydrogenation are shown in Table 25.

[0426] Table 25

[0427]

[0428] Obviously, compared with the catalysts prepared without organic compounds, all Fe-Mn-K catalysts prepared with organic compounds showed both higher CO2 conversion and higher selectivity for hydrocarbons in the jet engine fuel range. The catalysts prepared with EDTA, citric acid, oxalic acid, NTA, DTPA, tartaric acid, HEDTA and salicylic acid showed better catalytic performances.

[0429] All references cited herein (including publications, patent applications, and patents) are hereby incorporated by reference in their entirety, to the same extent as if each reference had been individually and specifically indicated to be incorporated by reference and were set forth in full herein (to the maximum extent permitted by law).

[0430] All headings and subheadings used herein are for convenience only and should not be construed as limiting the invention in any way.

[0431] The use of any and all examples or exemplary language (such as "for example") provided herein is intended only to better illustrate the invention and does not limit the scope of the invention, unless otherwise specified. No language in this specification should be construed as indicating that any non-illustrative element is essential to the practice of the invention.

[0432] The citation and incorporation of patent documents herein are for convenience only and do not reflect any opinion on the validity, patentability, and / or enforceability of such patent documents.

[0433] The present invention includes all modifications and equivalent schemes of the subject matter described in the appended paragraphs permitted by applicable law.

Claims

1. A method for producing C 5+ olefins, the method comprising contacting a feedstock comprising hydrogen and carbon dioxide with a CO2 hydrogenation catalyst precursor, wherein, The method for preparing the CO2 hydrogenation catalyst precursor includes: (a) combining (i) an iron substance; (ii) at least one transition metal selected from manganese and cobalt, or its salt, its oxide or its hydroxide; (iii) an alkali metal or its salt, (iv) a complexing agent, and (v) a solvent; (b) stirring the mixture of step (a) to provide a homogeneous mixture; (c) heating the mixture of step (b) to partially remove the solvent, thereby providing a slurry or paste; (d) calcining the slurry or paste of step (c) to provide a powder, wherein the catalyst precursor comprises 50 wt% to 90 wt% of iron, wherein, before contacting the feedstock with the CO2 hydrogenation catalyst precursor, the CO2 hydrogenation catalyst precursor is activated, and the activation includes reducing the precursor.

2. The method for producing C 5+ olefins according to claim 1, wherein the complexing agent is selected from citric acid, tartaric acid, oxalic acid, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), and HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid), or a salt thereof.

3. The method for producing C 5+ olefins according to claim 1, wherein the complexing agent is citric acid.

4. The method for producing C 5+ olefins according to claim 1, wherein the alkali metal or its salt comprises potassium or its salt.

5. The method for producing C 5+ olefins according to claim 1, wherein the iron substance is an iron salt.

6. The method for producing C 5+ olefins according to claim 1, wherein step (a) comprises combining (i) Fe or its salt, (ii) Mn or its salt, (iii) potassium or its salt, and (iv) citric acid or its salt.

7. The method for producing C 5+ olefins according to claim 1, wherein step (a) comprises combining (i) Fe or its salt, (ii) Mn or its salt and Co or its salt, (iii) potassium or its salt, and (iv) a complexing agent.

8. The method for producing C 5+ olefins according to claim 1, wherein in step (c), the mixture is heated to a temperature of 30 °C to 120 °C.

9. The method for producing C 5+ olefins according to claim 1, wherein the calcination is carried out at a temperature of 300 °C to 500 °C.

10. The method for producing C 5+A process for olefins, wherein the molar ratio of Fe:Mn in step (a) is from 100:1 to 4:

1.

11. The process for producing C 5+ A process for olefins, wherein the molar ratio of Fe:K in step (a) is from 20:1 to 4:

1.

12. The process for producing C 5+ A process for olefins, wherein the molar ratio of Fe:alkali metal in step (a) is from 100:1 to 4:

1.

13. The process for producing C 5+ A process for olefins, wherein the molar ratio of Fe:alkali metal in step (a) is from 20:1 to 4:

1.

14. The process for producing C 5+ A process for olefins, wherein the feedstock is contacted with the catalyst precursor at a temperature of 300 °C to 350 °C.

15. The process for producing C 5+ A process for olefins, wherein the feedstock is contacted with the catalyst precursor at a pressure of 500 KPa to 10 MPa.

16. The process for producing C 5+ A process for olefins, wherein the feedstock further comprises carbon monoxide.

17. The process according to any one of claims 1 to 16, wherein The reduction is carried out by exposing the precursor to CO and hydrogen.

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