CATALYST AND METHOD FOR PREPARATION THEREOF

Abstract

A method of forming a catalyst precursor is provided, the method comprising: (a) forming a precipitate from a slurry comprising (i) a mixture of an iron precursor, at least one promoter precursor, and a solvent, and (ii) a solution of an alkali base, and (b) calcining the precipitate to form the catalyst precursor. Also provided are catalyst precursors, methods of forming the catalyst, and catalysts.

Description

[Technical field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims priority to Singapore Application No. 10202201204X, filed with the Intellectual Property Office of Singapore on February 8, 2022, the contents of which are incorporated herein by reference.

[0002] The present invention generally relates to a method for forming a catalyst precursor. The present invention further relates to a method for forming a catalyst. The present invention further relates to a catalyst. The present invention further relates to a method for producing CO using the catalyst described herein. x (wherein x is 1 or 2) and H 2 and a process for converting the same into hydrocarbons. [Background technology]

[0003] The Fischer-Tropsch synthesis (FTS) reaction uses coal, biomass, plastic waste, and CO 2 This synthesis process can be used to convert carbon monoxide / carbon dioxide and hydrogen into liquid hydrocarbons. Due to the usefulness of this process for decarbonization and renewable production of useful fuels, FTS has been extensively studied by researchers around the world for nearly a century. However, the development of effective and selective catalysts remains a challenging task.

[0004] Catalysts prepared for the FTS process generally contain Hagg carbides (Fe 5 C 2 ) has been recognized and has traditionally been considered the most useful active phase for the FTS process. 2 The C phase shows higher activity at lower temperatures, allowing the FTS process to be run at milder conditions and reducing energy usage in industrial processes. 2Since C is a rather unstable phase of iron carbide, its synthesis is not straightforward. Conventional methods for synthesizing iron-based catalysts for FTS generally use Fe 5 C 2 or a mixture of iron carbides as the catalytically active phase. 2 A few conventional methods are known in the art for synthesizing C. However, these methods require complex and tedious preparative procedures and have limited scalability.

[0005] ε-Fe 2 One conventional method for synthesizing C involves alkali leaching and quenching in a single roller melt-spinning method to prepare RQ-Fe alloys. The RQ-Fe alloys are 2 It needs to be further leached, collected as a powder using a magnet, washed multiple times with distilled water, ethanol, and PEG200, then stored and carbonized with syngas to yield C. This process is quite complicated and lengthy, which makes the effective preparation of the catalyst impossible.

[0006] Nanocrystalline ε-Fe for better stability and selectivity of FTS 2 Another conventional method of embedding C into hollow carbon spheres (HCS) is known. This method requires first preparing HCS structures by applying the Stober method to silica spheres, followed by doping and aging for 24 hours, followed by static hydrothermal synthesis and washing. After completing the above steps, extensive impregnation is required to prepare the catalyst samples, which includes rotary evaporation, vacuum drying, and pyrolysis. This method is also complicated and time-consuming, which makes it impossible to effectively prepare the catalyst.

[0007] ε-Fe for improved stability at high temperatures 2 Another conventional method is known to trap C in graphene layers. This method is less complicated than the above two methods, but still requires pyrolysis with urea and glucose. Urea is toxic and harmful to humans, so additional health hazards are introduced during the synthesis process.

[0008] Another conventional method for synthesizing iron-based catalysts has been to promote the system using metals from groups 11 and 13. Among them, indium is C 2 ~C 4 The olefin selectivity is significantly better than that of gallium. However, the nature of the active phase (theoretically assumed to be iron carbide) is unclear. 2 It is unclear whether C or any other iron carbides are formed by this method. Summary of the Invention [Problem to be solved by the invention]

[0009] Thus, there is a need for catalyst precursors, catalysts, and methods of preparing the same that ameliorate or address one or more of the deficiencies discussed above. [Means for solving the problem]

[0010] In one aspect, there is provided a method of forming a catalyst precursor, comprising the steps of: (a) forming a precipitate from a slurry comprising (i) a mixture of an iron precursor, at least one promoter precursor, and a solvent, and (ii) a solution of an alkali base; (b) calcining the precipitate to form a catalyst precursor A method is provided, comprising:

[0011] In another embodiment, a catalyst precursor is provided that includes iron oxide, at least one promoter, and a salt.

[0012] In another aspect, a method of forming a catalyst is provided that includes carbonizing a catalyst precursor as described herein.

[0013] In another embodiment, ε-Fe 2 A catalyst is provided that includes C, an alkali metal element, and at least one additional metal.

[0014] In another embodiment, the catalysts described herein are used to produce CO x (wherein x is 1 or 2) and H 2 and a process for converting the same to hydrocarbons is provided.

[0015] The accompanying drawings illustrate disclosed embodiments and serve to explain the principles of the disclosed embodiments, but it is to be understood that the drawings are designed for purposes of illustration only and not as a definition of the limits of the invention. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 shows an X-ray diffraction pattern of a catalyst precursor according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 shows an X-ray diffraction pattern of a reduced catalyst precursor according to one embodiment of the present disclosure. [Diagram 3] FIG. 2 shows an X-ray diffraction pattern of a catalyst according to one embodiment of the present disclosure. [Figure 4] FIG. 2 shows an X-ray diffraction pattern of a promoter-free catalyst precursor. [Diagram 5] FIG. 2 shows an X-ray diffraction pattern of a promoter-free reduced catalyst precursor. [Figure 6] FIG. 2 shows an X-ray diffraction pattern of a catalyst formed from a promoter-free catalyst precursor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] definition As used herein, the following words and terms shall have the meanings set forth below.

[0018] The word "substantially" does not exclude "completely", for example a composition that is "substantially free" of Y may be completely free of Y. Where appropriate, the word "substantially" may be omitted from the definition of the invention.

[0019] Unless otherwise specified, the terms "comprising" and "comprises," as well as grammatical variations thereof, are intended to express "open" or "inclusive" language, such that not only the recited elements are included, but also permit the inclusion of additional, unrecited elements.

[0020] The term "about," as used herein, typically means + / - 5% of the stated value, more typically + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0021] Throughout this disclosure, certain embodiments may be disclosed in a range format. Descriptions in range format should be understood to be merely for convenience and brevity, and should not be construed as inflexible limitations on the disclosed range. Thus, the description of a range should be considered to have explicitly disclosed all possible subranges as well as individual numerical values ​​within that range. For example, the description of a range such as 1-6 should be considered to have explicitly disclosed subranges such as 1-3, 1-4, 1-5, 2-4, 2-6, 3-6, and individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0022] Certain embodiments may be described broadly and generically herein. Each of the narrower species and subgroups falling within the scope of the generic disclosure also form part of the disclosure. This includes the generic description of embodiments with a provisos or negative limitation that removes any subject matter from the generic term, regardless of whether the removed material is explicitly recited herein.

[0023] Detailed Disclosure of the Embodiments Exemplary, non-limiting embodiments of methods for forming a catalyst precursor are disclosed below.

[0024] The method comprises: (a) forming a precipitate from a slurry comprising (i) a mixture of an iron precursor, at least one promoter precursor, and a solvent, and (ii) a solution of an alkali base; (b) calcining the precipitate to form a catalyst precursor Includes.

[0025] The forming step (a) comprises: (a1) combining an iron precursor, at least one promoter precursor, and a solvent to form a mixture; (a2) adding a solution of an alkali base to the mixture of step (a1) to form a slurry. may include:

[0026] The catalyst precursor formed by this method may be reduced and activated in situ (such as by carbonization) to give the active ε-Fe 2 Phase C is formed.

[0027] Advantageously, the catalyst precursor is prepared from a promoter precursor, which allows the process to proceed under mild conditions with very simple operations. Thus, the process of the present invention does not require the use of harmful organic chemicals such as urea. The process of the present invention also does not require harsh synthesis steps such as repeated leaching or pyrolysis.

[0028] In the forming step (a), the iron precursor may be an iron salt. The iron precursor may be selected from the group consisting of iron (III) nitrate, iron (III) chloride, iron (III) sulfate, iron (II) nitrate, iron (II) chloride, iron (II) sulfate, and combinations thereof. The iron precursor may be iron (III) nitrate.

[0029] In the forming step (a), the at least one promoter precursor may be a salt of a metal selected from the group consisting of cobalt, nickel, gallium, germanium, indium, tin, zinc, cadmium, antimony, titanium, manganese, and combinations and hydrates thereof. In one example, the at least one promoter precursor may include a cobalt salt. When a cobalt salt is included, the catalyst precursor formed by the present method has a higher CO 2 In another example, the at least one promoter precursor may include a gallium salt. Non-limiting examples of salts include nitrates, chlorides, sulfates, and combinations thereof. The salt may be a nitrate.

[0030] In the forming step (a), the mixture may include at least two promoter precursors. The at least two promoter precursors may be independently selected from the list of metals and salts above, and in one example, the at least two promoter precursors may include cobalt (III) nitrate and gallium (III) nitrate, or hydrates thereof. The at least two promoter precursors may be provided in a molar ratio of about 16:1 to about 20:1, about 16:1 to about 18:1, or about 18:1 to about 20:1. In an example where the at least two promoter precursors include (or are) cobalt (III) nitrate and gallium (III) nitrate, the molar ratio between the cobalt (III) nitrate and the gallium (III) nitrate, or between the hydrates thereof, may be about 16:1 to about 20:1, or about 18:1.

[0031] In the forming step (a), the mixture may additionally comprise an additive. Thus, the method comprises: (a3) adding an additive to the mixture after said mixing step (a1) but before said adding step (a2). It may further include.

[0032] The additive can improve the thermal conductivity of the catalyst precursor. The additive can be silicon carbide or graphite.

[0033] In the forming step (a), the solvent may be water.

[0034] In the mixture of forming step (a), the iron precursor may have a concentration in the range of about 0.2 M to about 1.2 M, about 0.2 M to about 0.6 M, about 0.2 M to about 0.4 M, about 0.4 M to about 1.2 M, about 0.6 M to about 1.2 M, or about 0.4 M to about 0.6 M. The concentration of the iron precursor may be about 0.5 M.

[0035] In the mixture of the forming step (a), the at least one accelerator precursor may have a concentration in the range of about 0.05M to about 0.6M, about 0.2M to about 0.6M, about 0.4M to about 0.6M, about 0.05M to about 0.4M, or about 0.05M to about 0.2M. The concentration of the at least one accelerator precursor may be about 0.2M. When at least two accelerator precursors are present, the at least two accelerator precursors may have a combined concentration in the range of about 0.05M to about 0.6M, about 0.2M to about 0.6M, about 0.4M to about 0.6M, about 0.05M to about 0.4M, or about 0.05M to about 0.2M. The combined concentration of the at least two accelerator precursors may be about 0.2M.

[0036] In the mixture of forming step (a), the additive, if present, may have a concentration in the range of about 5 mM to about 7 mM, about 5 mM to about 6 mM, or about 6 mM to about 7 mM. The concentration of the additive may be about 6 mM.

[0037] In forming step (a), the solution of alkali base may comprise an alkali base and a solvent.

[0038] In the alkaline base solution, non-limiting examples of alkaline bases include potassium hydroxide, sodium hydroxide, cesium hydroxide, rubidium hydroxide, lithium hydroxide, and combinations thereof.

[0039] In the solution of the alkali base, the alkali base may have a concentration in the range of about 0.4 M to about 0.6 M, about 0.4 M to about 0.5 M, or about 0.5 M to about 0.6 M. The concentration of the base may be about 0.5 M.

[0040] In the alkali base solution, the solvent may be water.

[0041] In the formation step (a), the alkali base solution and the mixture may have a weight ratio in the range of about 1:0.1 to about 1:10, about 1:0.1 to about 1:3, about 1:0.1 to about 1:1, about 1:1 to about 1:10, about 1:3 to about 1:10, or about 1:1 to about 1:3. The weight ratio between the alkali base solution and the mixture in step (a) may be about 1:2.

[0042] The forming step (a) may include heating the slurry and drying to form the precipitate. Heating the slurry may be performed with constant mixing, such as stirring.

[0043] In the forming step (a), the slurry may be heated to a temperature within the range of about 60°C to about 90°C, about 70°C to about 90°C, about 80°C to about 90°C, about 60°C to about 80°C, or about 60°C to about 70°C.

[0044] In the forming step (a), the slurry may be heated for a duration in the range of about 6 hours to about 10 hours, about 6 hours to about 8 hours, or about 8 hours to about 10 hours. The slurry may alternatively or additionally be heated to dryness.

[0045] The precipitate of forming step (a) may be subjected to a filtering step prior to the calcining step (d). (a4) filtering the precipitate prior to the calcination step (b). It may further include.

[0046] In the calcination step (b), the precipitate may be calcined at a calcination temperature in the range of about 200° C. to about 500° C., about 300° C. to about 500° C., about 400° C. to about 500° C., about 200° C. to about 400° C., or about 200° C. to about 300° C. The calcination temperature may be about 450° C.

[0047] In the baking step (b), the baking temperature may be reached by heating at a ramp rate in the range of about 1° C. / min to about 10° C. / min, about 4° C. / min to about 10° C. / min, 7° C. / min to about 10° C. / min, 1° C. / min to about 7° C. / min, or about 1° C. / min to about 4° C. / min. The ramp rate may be about 3° C. / min.

[0048] In the calcination step (b), the precipitate may be calcined for a duration within the range of about 3 hours to about 8 hours, about 5 hours to about 8 hours, or about 3 hours to about 5 hours. The precipitate may be calcined for a duration of about 4 hours.

[0049] In the calcination step (b), the precipitate may be calcined in static air. After the calcination step, the iron precursor may be converted to iron oxide in the catalyst precursor. The metal of the promoter precursor may be converted to a metal oxide in the catalyst precursor. The alkali base may be converted to a salt in the catalyst precursor. The additive may retain its original chemical formula in the catalyst precursor.

[0050] Exemplary, non-limiting embodiments of catalyst precursors are disclosed below.

[0051] The catalyst precursor comprises iron oxide, at least one promoter, and a salt.

[0052] The catalyst precursor may also be referred to as a calcined catalyst. The catalyst precursor may be reduced and activated in situ (such as by carbonization) to give the active ε-Fe 2 Phase C is formed.

[0053] In the catalyst precursor, iron oxide is hematite (Fe 2 O 3 ), Fe 3 O4 , or a combination thereof.

[0054] In the catalyst precursor, the at least one promoter may be a metal oxide of a metal selected from the group consisting of cobalt, nickel, gallium, germanium, indium, tin, zinc, cadmium, antimony, titanium, manganese, and combinations thereof. When the metals are combinations of the above, the metal oxide may be considered a bimetallic oxide, trimetallic oxide, etc. In one example, the at least one promoter precursor may include cobalt oxide. Cobalt oxide is represented by the formula: 2 O 3 , Co 3 O 4 , or a combination thereof. 3 O 4 When included in the catalyst precursor, the catalyst precursor advantageously produces a higher CO 2 In another example, the at least one promoter precursor may have a conversion of Ga 2 O 3 Gallium oxide such as

[0055] In the catalyst precursor, the iron oxide and the at least one promoter may have a molar ratio within the range of about 1:0.01 to about 1:0.28, about 1:0.1 to about 1:0.28, about 1:0.2 to about 1:0.28, about 1:0.01 to about 1:0.2, or about 1:0.01 to about 1:0.1.

[0056] The catalyst precursor may include at least two promoters. The at least two promoters may be independently selected from the list of metal oxides above. In one example, the at least two promoters are Co. 3 O 4 and Ga 2 O 3 The at least two promoters may be provided in a molar ratio ranging from about 16:1 to about 20:1, from about 16:1 to about 18:1, or from about 18:1 to about 20:1. 3 O 4 and Ga 2 O 3In the example containing (or having two promoters), Co 3 O 4 and Ga 2 O 3 The molar ratio between may be from about 16:1 to about 20:1, or about 18:1.

[0057] When the catalyst precursor includes at least two promoters, the combination of the iron oxide and the at least two promoters may have a molar ratio within the range of about 1:0.01 to about 1:0.28, about 1:0.1 to about 1:0.28, about 1:0.2 to about 1:0.28, about 1:0.01 to about 1:0.2, or about 1:0.01 to about 1:0.1.

[0058] The catalyst precursor may further include an additive, which may improve the thermal conductivity of the catalyst precursor. The additive may be silicon carbide or graphite.

[0059] In the catalyst precursor, the iron oxide and the additive (if present) may have a molar ratio in the range of about 60:1 to about 100:1, about 60:1 to about 80:1, or about 80:1 to about 100:1. The concentration between the iron oxide and the additive may be about 80:1.

[0060] In the catalyst precursor, the salt may include an alkali metal cation selected from potassium, sodium, cesium, rubidium, lithium, and combinations thereof. The salt may include an anion selected from nitrate, chloride, sulfate, hydroxide, and combinations thereof. The salt may be potassium nitrate.

[0061] In the catalyst precursor, the iron oxide and the salt may have a molar ratio in the range of about 1:0.2 to about 1:0.5, about 1:0.3 to about 1:0.5, about 1:0.4 to about 1:0.5, about 1:0.2 to about 1:0.4, about 1:0.2 to about 1:0.3, or about 1:0.3 to about 1:0.4. The molar ratio between the iron oxide and the salt may be about 1:0.35.

[0062] The catalyst precursor may be prepared by the methods described herein.

[0063] Exemplary, non-limiting embodiments of methods for forming a catalyst are disclosed below.

[0064] The method includes carbonizing the catalyst precursor described herein.

[0065] In the carbonization step, the catalyst precursor is also reduced, and thus the carbonization step can be considered as a single step in which both reduction and carbonization take place.

[0066] Thus, the method of forming the catalyst includes: (a) forming a precipitate from a slurry comprising (i) a mixture of an iron precursor, at least one promoter precursor, and a solvent, and (ii) a solution of an alkali base; (b) calcining the precipitate to form a catalyst precursor; and (c) carbonizing the catalyst precursor from step (b) to form the catalyst. may include:

[0067] In one example, a method of forming a catalyst includes: (a) combining an iron precursor, at least one promoter precursor, and a solvent to form a mixture; (b) adding a solution of an alkali base to the mixture of step (a) to form a slurry; (c) forming a precipitate from the slurry of step (b); (d) calcining the precipitate of step (c) to form a catalyst precursor; and (e) carbonizing the catalyst precursor from step (d) to form the catalyst. may include:

[0068] The catalyst formed by the present method may be referred to as the active phase. The catalyst formed by the present method may include a common metal phase (including alloys). Thus, the carbonization process may be referred to as the reduction and activation of the catalyst precursor, after which the active phase is formed.

[0069] Advantageously, the carbonization process can be carried out using CO and H 2 This step can therefore be carried out using a combination of CO and H 2 This can be done in situ before the catalyst is applied to the Fischer-Tropsch reaction in which it is used. No additional activation step is required.

[0070] More advantageously, the carbonization step comprises the step of carbonizing the carbonized material with at least about 50% by volume of H 2 or at least about 60% by volume H 2 The process may be carried out under various conditions, such as by using a gas mixture containing H 2 When the gas mixture has a high volume percentage of active ε-Fe 2 The C phase can be formed more efficiently.

[0071] Even more advantageously, the catalyst formed by the present method can be stable at a temperature of at least about 200° C. This is due to at least one promoter that promotes an open structure of the iron, while the alkali base contains an alkali metal cation that promotes the dissociation of CO during the carbonization step to provide a carbon source for the catalyst. 5 C 2 At least one promoter may be intercalated into the iron structure of the catalyst, which would otherwise not form a catalyst at elevated temperatures as defined above. 5 C 2 The iron carbides may be converted to conventional iron carbides such as

[0072] The method may further include the step of diluting the catalyst precursor described herein with a catalyst support prior to the carbonization step.

[0073] Non-limiting examples of catalyst supports include silicon carbide, silica, carbon, alumina, and combinations thereof.

[0074] The catalyst support may be silicon carbide having a size within the range of about 0.1 μm to 500 μm.

[0075] In the dilution step, the catalyst precursor and catalyst support described herein may be mixed in a volume ratio ranging from about 2:1 to about 1:2, from about 2:1 to about 1:1, or from about 1:1 to about 1:2. The volume ratio between the catalyst precursor and the catalyst support may be about 1:1.

[0076] The method may further comprise the step of reducing the catalyst precursor prior to the carbonization step.

[0077] The reduction step may be carried out by placing the catalyst precursor described herein in a reducing atmosphere. 2 The reducing atmosphere may be CO or H 2 It may further contain S. The reducing atmosphere may have a gauge pressure within a range of about 0 MPa to about 3 MPa, about 1 MPa to about 3 MPa, about 2 MPa to about 3 MPa, about 0 MPa to about 2 MPa, about 0 MPa to about 1 MPa, or about 0.1 MPa to about 0.15 MPa. The gauge pressure of the reducing atmosphere may be about 0.1 MPa.

[0078] The reduction step may be carried out at a reduction temperature above 300° C. The reduction temperature may be within the range of about 400° C. to about 600° C., about 500° C. to about 600° C., or about 400° C. to about 500° C. The reduction temperature may be about 400° C.

[0079] The reduction temperature may be reached by heating at a ramp rate in the range of about 1° C. / min to about 10° C. / min, about 4° C. / min to about 10° C. / min, about 7° C. / min to about 10° C. / min, about 1° C. / min to about 7° C. / min, or about 1° C. / min to about 4° C. / min. The ramp rate may be about 3° C. / min.

[0080] The reduction step may be carried out for a duration within the range of about 2 hours to about 24 hours, about 12 hours to about 24 hours, or about 2 hours to about 12 hours. The duration may be about 10 hours.

[0081] In the present method, the carbonization step may be carried out by placing the catalyst precursor in a carbon-containing reducing atmosphere. The carbon-containing reducing atmosphere may be CO, CO 2 , C 1 ~C 4 The carbon-containing reducing atmosphere may comprise H 2 O 3 in a volume ratio ranging from about 1:0.01 to about 1:99.9, from about 1:1 to about 1:99.9, or from about 1:0.01 to about 1:1. 2 and CO. 2 and CO may be about 2:1 by volume.

[0082] The carbon-containing reducing atmosphere may have a gauge pressure in the range of about 0 MPa to about 10 MPa, about 0 MPa to about 1 MPa, or about 1 MPa to about 10 MPa. The gauge pressure of the carbon-containing reducing atmosphere may be about 1 MPa.

[0083] In the present method, the carbonization step may be carried out at a carbonization temperature within the range of about 100° C. to about 400° C., about 200° C. to about 400° C., about 300° C. to about 400° C., about 100° C. to about 300° C., or about 100° C. to about 200° C. The carbonization temperature may be about 300° C.

[0084] The carbonization temperature may be reached by heating at a ramp rate in the range of about 1° C. / min to about 10° C. / min, about 4° C. / min to about 10° C. / min, about 7° C. / min to about 10° C. / min, about 1° C. / min to about 7° C. / min, or about 1° C. / min to about 4° C. / min. The ramp rate may be about 2° C. / min.

[0085] In the present method, the carbonization step may be carried out for a duration within the range of about 2 hours to about 50 hours, about 25 hours to about 50 hours, or about 2 hours to about 25 hours. The duration may be about 24 hours.

[0086] In the present process, the dilution step (if present), the reduction step (if present), and the carbonization step may be carried out in a reaction tube, a continuous flow system, a slurry bed reactor, or a fluidized bed reactor, which allows for the introduction of gas and heating of the catalyst.

[0087] The catalyst formed by this method is ε-Fe 2 It may also be C.

[0088] Exemplary, non-limiting embodiments of the catalyst are disclosed below.

[0089] The catalyst is ε-Fe 2 C, an alkali metal element, and at least one additional metal.

[0090] The catalyst may also be referred to as the active phase. The catalyst may include a common metal phase (including alloys). The catalyst may include ε-Fe 2 It may further contain iron that is not in the form of C (such as iron oxide).

[0091] Advantageously, the catalyst can be stable at a temperature of at least about 200° C. due to at least one additional metal that promotes an open structure of the iron, while the alkali metal element promotes the dissociation of CO during the carbonization process to provide a carbon source for the catalyst. 5 C 2 It has a more open structure and a higher percentage of carbon atoms in it than conventional iron carbides such as those described above. Additional metals can be intercalated into the iron structure of the catalyst, which would otherwise not be able to form Fe at high temperatures as defined above. 5 C 2 The iron carbides may be converted to conventional iron carbides such as

[0092] In the catalyst, the additional metal may be selected from the group consisting of cobalt, nickel, gallium, germanium, indium, tin, zinc, cadmium, antimony, titanium, manganese, and combinations thereof. In one example, the additional metal may be cobalt. Advantageously, the catalyst has a higher CO 2 In another example, the additional metal may be gallium.

[0093] In the catalyst, ε-Fe 2The C and the additional metal may have a molar ratio within the range of about 1:0.01 to about 1:0.28, about 1:0.1 to about 1:0.28, about 1:0.2 to about 1:0.28, about 1:0.01 to about 1:0.2, or about 1:0.01 to about 1:0.1.

[0094] The catalyst may include at least two additional metals. The at least two metals may be independently selected from the list of metals above, and in one example, the at least two metals may include cobalt and gallium. The at least two metals may be provided in a molar ratio within the range of about 16:1 to about 20:1, about 16:1 to about 18:1, or about 18:1 to about 20:1. In examples where the at least two metals include (or are) cobalt and gallium, the molar ratio between cobalt and gallium may be about 16:1 to about 20:1, or about 18:1.

[0095] When the catalyst contains at least two metals, ε-Fe 2 The combination of C and the at least two metals may have a molar ratio within the range of about 1:0.01 to about 1:0.28, about 1:0.1 to about 1:0.28, about 1:0.2 to about 1:0.28, about 1:0.01 to about 1:0.2, or about 1:0.01 to about 1:0.1.

[0096] The catalyst may further include an additive, which may improve the thermal conductivity of the catalyst precursor. The additive may be silicon carbide or graphite.

[0097] In the catalyst, ε-Fe 2 C and the additive (if present) may have a molar ratio within the range of about 60:1 to about 100:1, about 60:1 to about 80:1, or about 80:1 to about 100:1. 2 The molar ratio between C and the additive may be about 80:1.

[0098] In the catalyst, the alkali metal element may be sodium, potassium, cesium, rubidium, lithium, or a combination thereof.

[0099] In the catalyst, the total amount of iron and the alkali metal element may have a molar ratio in the range of about 1:0.2 to about 1:0.5, about 1:0.3 to about 1:0.5, about 1:0.4 to about 1:0.5, about 1:0.2 to about 1:0.4, about 1:0.2 to about 1:0.3, or about 1:0.3 to about 1:0.4. The molar ratio between the total amount of iron and the alkali metal element may be about 1:0.35.

[0100] The catalyst may further comprise a catalyst support.

[0101] Non-limiting examples of catalyst supports include silicon carbide, silica, carbon, alumina, and combinations thereof.

[0102] The catalyst support may be silicon carbide having a size within the range of about 0.1 μm to 500 μm.

[0103] When present, the catalyst support may have a volume ratio of about 50% based on the total volume of the catalyst.

[0104] The catalyst is K a Fe b Co c -Ga d -(SiC) e may have the formula: a is a number in the range of 0.01 to 0.5, b is 1, c is a number in the range of 0 to 0.5, d is a number in the range of 0 to 0.3; e is a number in the range of 0 to 0.1, However, c+d is greater than 0, The catalyst is globally neutral in charge.

[0105] The catalyst may be prepared by the methods described herein.

[0106] CO x and H 2 Exemplary, non-limiting embodiments of the process for converting toluene and toluene to hydrocarbons are disclosed below.

[0107] The method utilizes a catalyst as described herein, wherein x is 1 or 2.

[0108] The process may be carried out in a reactor tube, a continuous flow system, a slurry bed reactor, or a fluidized bed reactor, which allows for the introduction of gases and heating of the catalyst.

[0109] H 2 and CO x may have a volume ratio in the range of about 1:2 to about 5:1, about 2:1 to about 5:1, or about 1:2 to about 2:1. 2 and CO x The volume ratio between may be about 3:1.

[0110] H 2 and CO x may have a combined gauge pressure in the range of about 0 MPa to about 10 MPa, about 3 MPa to about 10 MPa, or about 0 MPa or about 3 MPa. The combined gauge pressure may be about 3 MPa.

[0111] H 2 and CO x is 20000cm 3 ·g·cat -1 h -1 The catalyst described herein may be passed through at the following flow rates: The flow rate is about 1500 cm 3 ·g·cat -1 h -1 ~About 2500cm 3 ·g·cat -1 h -1 , about 1500cm 3 ·g·cat -1 h -1 ~about 2000cm 3 ·g·cat -1 h -1 , or about 2000 cm 3 ·g·cat -1 h -1 ~About 2500cm 3 ·g·cat -1 h -1 The flow rate may be in the range of about 2000 cm 3·g·cat -1 h -1 may be also possible.

[0112] The method may be carried out at a reaction temperature in the range of about 180° C. to about 400° C., about 280° C. to about 400° C., or about 180° C. to about 280° C. The reaction temperature may be about 280° C. EXAMPLES

[0113] Non-limiting examples of the present invention will now be described in further detail by reference to specific examples, which are not to be construed as limiting the scope of the invention in any way.

[0114] Example 1 - Preparation of catalyst In general, the gallium-promoted iron-based catalyst according to the present disclosure was prepared by co-precipitation technique. Specifically, the following components were combined in a beaker and dissolved in 100 ml water (purchased from Sigma Aldrich, Singapore): 20 g iron (III) nitrate nonahydrate (purchased from Sigma Aldrich, Singapore), 7.02 g cobalt (III) nitrate hexahydrate (purchased from Sigma Aldrich, Singapore), 0.492 g gallium (III) nitrate nonahydrate (purchased from Sigma Aldrich, Singapore), and 0.025 g silicon carbide (purchased from Sigma Aldrich, Singapore). The formed solution was thoroughly stirred and then precipitated with 1.39 g potassium hydroxide (purchased from Sigma Aldrich, Singapore) dissolved in 50 ml water. The resulting precipitated slurry was gently heated and stirred overnight to dry. The resulting precipitate was then removed from the beaker by filtration and calcined in static air at 450° C. for 4 hours (ramp rate: 3° C. / min) to form a catalyst precursor.

[0115] After calcination, the catalyst precursor was subjected to an in situ pretreatment process consisting of reduction and activation. Reduction and activation were carried out in situ before the Fischer-Tropsch synthesis (FTS) test. The reduction was carried out by H 2 The activation was carried out at ambient pressure and 400°C for 10 hours (ramp rate: 3°C / min).2 The experiment was carried out at 1 MPa and 300°C for 24 hours (ramp rate: 2°C / min) using a 100 MPa / CO2 reactor.

[0116] Example 2 - Catalyst characterization To identify the crystalline phases present in the catalyst at various stages of the formation process, X-ray diffraction (XRD) characterization was performed on a Bruker D8 Advance X-ray diffractometer on the catalyst precursor, reduced catalyst precursor, and pretreated (or activated) catalyst precursor (which is the catalyst) samples.

[0117] As described in Example 1, the reduction and activation steps were carried out in situ in the reaction tube before the start of the FTS test. The reduction was carried out using H 2 The activation was carried out at ambient pressure and 400°C for 10 hours (ramp rate: 3°C / min). 2 The experiment was carried out at 1 MPa and 300°C for 24 hours (ramp rate: 2°C / min) using a 100 MPa / CO2 reactor.

[0118] Referring to FIG. 1, the catalyst precursor was identified by XRD as hematite (Fe 2 O 3 ), cobalt(II,III) oxide (Co 3 O 4 ), gallium oxide (Ga 2 O 3 ), and potassium nitrate (KNO 3 ) combination of crystal structures.

[0119] After undergoing the reduction step, the oxides in the catalyst precursor were reduced to alloy phases. Referring to Figure 2, XRD characterization showed peaks of alloys formed from the metals present (Fe, Co, Ga, and Si). As expected by the inventors, no carbide phases were present before activation with syngas.

[0120] Referring to FIG. 3, after activation with syngas, the overall composition of the catalyst precursor changed to Fe 2 C and small amounts of Fe 5 C 2(Hagg carbide), as well as pure iron, indicating that the formation of the iron carbide phase is a direct result of the carburization process that the catalyst precursor underwent during activation.

[0121] Comparative Example 1 - Preparation and Characterization of Catalysts Containing No Gallium Dopant For comparative purposes, a catalyst sample was also prepared without the gallium dopant (gallium(III) nitrate nonahydrate) used as described in Example 1. The remaining preparation and characterization processes were the same as those described in Examples 1 and 2.

[0122] 4-6, the XRD results of the catalyst without gallium dopant reflected the crystal structure of hematite and cobalt oxide similarly before reduction and pretreatment. However, after pretreatment (or activation), only Hagg carbide was present, and Fe 2 C was not present. Therefore, the gallium dopant was Fe 2 It was clear that the carbide phase was essential for the formation of the carbide phase.

[0123] Example 3 - Fischer-Tropsch Synthesis (FTS) Catalysis Test Catalysis tests were carried out by performing Fischer-Tropsch synthesis (FTS) in an Imtech customized fixed-bed reactor system equipped with a 14 mm diameter RA330 alloy reactor tube. 1.0 g of each catalyst was diluted with SiC with a volume of 500 μm in a 1:1 volume ratio and then loaded into the reactor.

[0124] Subsequent reduction and activation was carried out in situ prior to FTS testing as described in Example 1. Briefly, reduction was carried out using H 2 The activation was carried out at ambient pressure and 400 °C for 10 h (ramp rate: 3 °C / min). 2 The experiment was carried out at 1 MPa and 300°C for 24 hours (ramp rate: 2°C / min) using a 100 MPa / CO2 reactor.

[0125] After reduction and activation were complete, the reactor was cooled to ambient temperature and pressurized to 3 MPa. The reactor was then heated to 280° C. and CO 2 and H 2 (H 2 / CO 2 =3) at gas hourly space velocity (GHSV) of 2000 cm 3 gcat -1 h -1 We conducted FTS testing for use in the following.

[0126] The composition of the outlet gas was analyzed using an online gas chromatography (GC: Agilent, 8890). The data obtained from the GC were used to calculate key parameters, including CO 2 The catalyst performance was evaluated in terms of conversion and selectivity to hydrocarbons over the range of hydrocarbons as shown in Table 1 below.

[0127] [Table 1]

[0128] Catalyst testing shows excellent CO 2 As evidenced by the conversion and C5+ yield, the catalyst of the present invention (doped with gallium) was shown to exhibit significant improvement over the catalyst without the gallium dopant. 2 The C phase (which was absent in catalysts without gallium dopant, as shown by XRD characterization) was more commonly observed in the Fe 5 C 2 This is consistent with the findings of other reported studies that the Cr-Al phase has higher catalytic activity than the Cr-Al phase. [Industrial Applicability]

[0129] The catalyst of the present disclosure is CO or CO 2 The present invention may be used in a variety of applications, such as the conversion of natural gas into fuels or chemicals.

[0130] Various other modifications and adaptations of the present invention will be apparent to those skilled in the art after reading the foregoing disclosure, which do not depart from the spirit and scope of the present invention, and all such modifications and adaptations are intended to fall within the scope of the appended claims.

Claims

1. 1. A method of forming a catalyst precursor, comprising: (a) forming a precipitate from a slurry comprising (i) a mixture of an iron precursor, at least one promoter precursor, and a solvent, and (ii) a solution of an alkali base; and (b) calcining the precipitate to form a catalyst precursor A method comprising:

2. The forming step (a) (a1) combining an iron precursor, at least one promoter precursor, and a solvent to form a mixture; (a2) adding a solution of an alkali base to the mixture of step (a1) to form a slurry. The method of claim 1 , comprising:

3. 2. The method of claim 1, wherein the iron precursor is selected from the group consisting of iron (III) nitrate, iron (III) chloride, iron (III) sulfate, iron (II) nitrate, iron (II) chloride, iron (II) sulfate, and combinations thereof.

4. The method of claim 1 , wherein the at least one promoter precursor comprises a gallium salt.

5. 3. The method of claim 2, wherein the mixing step (a1) comprises mixing an iron precursor, at least two promoter precursors, and a solvent to form a mixture.

6. (a3) adding an additive to the mixture after said mixing step (a1) but before said adding step (a2). The method of claim 2 further comprising:

7. The alkali base solution and the mixture have a weight ratio in the range of 1:0.1 to 1:10; The method of claim 1.

8. 3. The method of claim 2, wherein in the adding step (a2), the solution of alkali base has a concentration in the range of 0.4M to 0.6M.

9. 10. The method of claim 1, wherein the forming step (a) comprises heating and drying the slurry to form the precipitate.

10. (a4) filtering the precipitate before the calcination step (b). The method of claim 1 further comprising:

11. 10. The method of claim 1, wherein the calcining step (b) comprises calcining the precipitate at a temperature in the range of 200°C to 500°C.

12. A catalyst precursor comprising iron oxide, at least one promoter, and a salt.

13. The catalyst precursor of claim 12 , wherein the at least one promoter comprises cobalt oxide.

14. The catalyst precursor of claim 12, wherein the catalyst precursor comprises at least two promoters.

15. The catalyst precursor of claim 12 further comprising an additive.

16. 13. The catalyst precursor of claim 12, wherein the salt comprises an alkali metal cation selected from potassium, sodium, cesium, rubidium, lithium, and combinations thereof.

17. 13. A method of forming a catalyst comprising carbonizing the catalyst precursor of claim 12.

18. 20. The method of claim 17, further comprising the step of diluting the catalyst precursor with a catalyst support prior to the carbonizing step.

19. 20. The method of claim 17, further comprising the step of reducing the catalyst precursor prior to the carbonizing step.

20. ε-Fe ２ A catalyst comprising C, an alkali metal element, and at least one additional metal.

21. The catalyst of claim 20 is used to produce CO ｘ (wherein x is 1 or 2) and H ２ and a method for converting them into hydrocarbons.

Images