High pressure reverse water gas shift reaction with low selectivity to methane

Abstract

A composition of an indium oxide catalyst including an alkali metal dopant and a method for producing an indium oxide catalyst including an alkali metal dopant. The alkali metal dopant can include Li + , Na + , K + , Rb + , Cs + , and Fr + cations. The method for producing an indium oxide catalyst including an alkali metal dopant includes mixing a solution of an indium salt with a base to form precipitated indium hydroxide (100), contacting the precipitated indium hydroxide with a solution including an alkali metal salt to produce an indium hydroxide solution (102), and calcining the indium hydroxide solution to form indium oxide; thereby forming an indium oxide catalyst including an alkali metal dopant (104).

Description

Background Technology

[0001] Carbon dioxide (CO2) can be converted into carbon monoxide (CO) through a process known as reverse water-gas shift reaction (RWGS). CO is a useful feedstock for methanol synthesis, liquid hydrocarbon production, and the production of other specialty chemicals. Typically, RWGS reactions are carried out at low (ambient) pressure and high temperatures. Since methanation (the conversion of carbon oxides and hydrogen into methane) is favorable at high pressures, RWGS reactions are usually conducted at ambient pressure. Furthermore, when using non-precious metal catalysts, the reaction must be carried out at high temperatures (above 500°C). Summary of the Invention

[0002] This overview is provided to introduce some concepts, which will be further described in the detailed description below. This overview is not intended to identify key or essential features of the claimed subject matter, nor is it intended to serve as an aid in limiting the scope of the claimed subject matter.

[0003] In one aspect, the embodiments disclosed herein relate to a composition of an indium oxide catalyst comprising an alkali metal dopant.

[0004] The embodiments disclosed herein also relate to a method for producing an indium oxide catalyst including an alkali metal dopant, comprising the steps of: mixing a solution of an indium salt with an alkali to form a precipitated indium hydroxide, contacting the precipitated indium hydroxide with a solution including an alkali metal salt to produce an indium hydroxide solution, and calcining the indium hydroxide solution to form indium oxide; thereby forming an indium oxide catalyst including an alkali metal dopant.

[0005] Any combination of the various embodiments and implementations disclosed herein can be used in other embodiments consistent with this disclosure. Other aspects and advantages of the claimed subject matter will become apparent from the following description and the appended claims. Attached Figure Description

[0006] Figure 1A Methods according to one or more embodiments of this document are illustrated.

[0007] Figure 1B Alternative methods according to one or more embodiments of this document are shown.

[0008] Figure 2 A process for producing carbon monoxide according to one or more embodiments of this document is shown.

[0009] Figure 3A The RWGS reactions of Examples 1-5 are shown at 400°C, 50 bar, and 15,000 mL / g / h with a 4:1 molar ratio of H2 / CO2 feed gas.

[0010] Figure 3B The RWGS reactions of Comparative Examples 1-5 are shown at 400 °C, 50 bar, and 15,000 mL / g / h with a 4:1 molar ratio of H2 / CO2 feed gas.

[0011] Figure 3C The RWGS reactions of Examples 1-5 under ambient conditions are shown.

[0012] Figure 4A The RWGS reaction under various reaction conditions using Example 3 as the catalyst is shown.

[0013] Figure 4B RWGS reactions under various reaction conditions using Example 1 as a catalyst are shown. Detailed Implementation

[0014] In the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be understood by those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0015] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in this application). The use of ordinal numbers does not imply or create any particular ordering of elements, nor does it limit any element to a single element, unless explicitly disclosed, such as by using the terms “before,” “after,” “single,” and other such terms. Rather, the use of ordinal numbers is for the purpose of distinguishing elements. For example, a first element is different from a second element, and a first element may contain more than one element and is located after (or before) the second element in the element ordering.

[0016] It should be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Thus, for example, referring to “fluid sample” includes referring to one or more such samples.

[0017] Terms such as “approximately,” “substantially,” and “about” indicate that the recorded feature, parameter, or value does not need to be precisely achieved; however, deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limitations, and other factors known to those skilled in the art, may occur in amounts that do not impede the effect that the feature is intended to provide.

[0018] It should be understood that one or more steps shown in the flowchart may be omitted, repeated, and / or performed in a different order than shown. Therefore, the scope of the invention should not be considered limited to the specific arrangement of the steps shown in the flowchart.

[0019] In the following description of the accompanying drawings, any component described with respect to the various embodiments disclosed herein may be equivalent to one or more components with the same name described with respect to any other drawing. For the sake of brevity, the description of these components will not be repeated with respect to each drawing. Thus, each component and each embodiment in each drawing is incorporated by reference and is assumed to be optionally present in each other drawing having one or more components with the same name. Furthermore, any description of a component in the drawings according to the various embodiments disclosed herein should be construed as an optional embodiment that may be implemented in addition to the embodiments described with respect to the corresponding components with the same name in any other drawing, or that the optional embodiment may be implemented in combination with or in lieu of the embodiments described with respect to the corresponding components with the same name in any other drawing.

[0020] The embodiments disclosed herein generally relate to indium oxide (In₂O₃) catalyst compositions containing alkali metal dopants. One or more embodiments also relate to a method for producing an In₂O₃ catalyst composition containing alkali metal dopants. Furthermore, one or more embodiments relate to a method for reacting an In₂O₃ catalyst composition containing alkali metal dopants in an RWGS reaction to form CO.

[0021] Some examples of catalysts for high-pressure RWGS have been previously reported, but these are accompanied by significant methane formation. Even with inhibited methane formation, these catalysts still require relatively high temperatures (above 500°C).

[0022] Therefore, there is a need for an improved In2O3 catalyst that enhances the conversion of CO2 to CO while minimizing selectivity for undesirable byproducts such as methane (CH4) or methanol (CH3OH). As used herein, the term “selectivity” for a catalyst refers to its ability to produce desired or undesirable products, and the term “conversion” refers to the amount of reactants that have been reacted. According to one or more embodiments presented herein, catalyst compositions are produced by doping In2O3 catalysts with alkali metals that maximize CO production in RWGS reactions carried out at high pressures (i.e., above about 30 bar) and low temperatures (i.e., below about 500°C).

[0023] Alkali metal-doped indium oxide catalyst composition

[0024] As described above, one or more embodiments of this disclosure relate to indium oxide (In₂O₃) catalyst compositions containing alkali metal dopants. In one or more embodiments, indium hydroxide [In(OH)₃], In₂O₃, or mixtures thereof can be prepared as a starting point for the production of alkali metal-doped In₂O₃ catalyst compositions. In(OH)₃ and In₂O₃ compounds, or mixtures thereof, are commercially available or can be produced according to the methods provided in later sections.

[0025] Generally, the use of In₂O₃ catalyst in the RWGS reaction offers high selectivity for CH₃OH production and relatively low CO production at lower reaction temperatures and higher reaction pressures. Therefore, when CO is the desired product, higher reaction temperatures and lower reaction pressures are typically required.

[0026] The use of alkali metal-doped In2O3 catalysts according to the embodiments described herein provides improved selectivity for enhanced CO production at low or high pressures (i.e., from ambient pressure to 50 bar) and moderate temperatures (less than about 500 °C) compared to In2O3 catalysts alone.

[0027] The term "dopant" refers to a substance added to a composition to alter or improve the properties of the composition. Specifically, according to the embodiments herein, a dopant refers to an alkali metal added to an In(OH)3 or In2O3 catalyst to produce an alkali metal-doped In2O3 catalyst.

[0028] In one or more embodiments, the alkali metal dopant can be any alkali metal cation selected from Group 1 of the periodic table, including lithium (Li). + ), sodium (Na + ), potassium (K) + ), Rubidium (Rb + ), Cesium (Cs) + ), francium (Fr) + (or a combination thereof)

[0029] In one or more embodiments, an alkali metal dopant may be added to an In2O3 catalyst to produce an alkali metal-doped In2O3 catalyst in an amount of about 0.5 wt% to about 10 wt% based on the total weight of the catalyst, such as a lower limit selected from any one of 0.5, 2 and 5 wt% to an upper limit selected from any one of 7, 9 and 10 wt%, wherein any lower limit may be paired with any upper limit.

[0030] In one or more embodiments, the alkali metal-doped In₂O₃ catalyst may have a particle size ranging from about 10 nm to about 200 nm, such as a lower limit selected from any one of 10, 25, and 50 nm to an upper limit selected from any one of 75, 100, and 200 nm, wherein any lower limit may be paired with any upper limit. The particle size of the alkali metal-doped In₂O₃ catalyst may be isolated or formed from larger aggregates.

[0031] In one or more embodiments, the alkali metal-doped In2O3 catalyst may be amorphous, or have cubic or hexagonal crystal cells or mixtures thereof.

[0032] In one or more embodiments, the alkali metal-doped In₂O₃ catalyst may have a molecular weight of about 7 to about 55 m. 2 / g, such as those selected from 7, 10, 15 and 20m 2 The lower limit of any of / g is selected from 25, 50, and 55m. 2 The surface area within the upper limit of any of / g.

[0033] Method for producing alkali metal-doped catalyst compositions

[0034] As described above, one or more embodiments also relate to a method for producing an In₂O₃ catalyst composition containing an alkali metal dopant. In one or more embodiments, the method for producing an alkali metal-doped In₂O₃ catalyst includes preparing indium hydroxide, impregnating indium hydroxide with a solution of an alkali metal salt, and then calcining to form an In₂O₃ catalyst containing an alkali metal dopant.

[0035] Figure 1A The illustration depicts a method for producing an In₂O₃ catalyst containing an alkali metal dopant according to one or more embodiments. In one or more embodiments, the method for producing the In₂O₃ catalyst containing an alkali metal dopant includes preparing indium hydroxide by mixing a solution of an indium salt with an alkali. Figure 1A In step 100, the solution of the indium salt is mixed with an alkali to form a precipitate of indium hydroxide.

[0036] The mixing of indium salt solution with alkali to form precipitate indium hydroxide can be accomplished by any method known in the art, such as a simple stirring mechanism, such as a stir bar, a high-shear mixer, or a shaker.

[0037] Indium salts can be any soluble indium compound, including, but not limited to, indium nitrate, indium acetate, indium chloride, indium oxalate, or indium sulfate in any hydrated form. Indium precursors can exist as mixtures of one or more indium compounds.

[0038] Solutions of indium salts can have concentrations suitable for achieving the maximum solubility of the salt in the reaction solvent. Those skilled in the art will understand that the solubility of indium salts varies depending on the salt and solvent used. For example, for reactions using indium nitrate in water, concentrations can range from 0.01 M to 4.00 M. However, this concentration range will vary depending on the salt, and therefore is for illustrative purposes only. Thus, a suitable concentration can be used in each reaction to completely saturate the solvent.

[0039] Solutions of indium salts can combine with bases to form precipitated indium hydroxide. Examples of bases include, but are not limited to, ammonium hydroxide, alkali metal hydroxides, or quaternary ammonium hydroxides, or mixtures thereof.

[0040] In one or more embodiments, a base is used to control the pH of the solution to promote the precipitation of indium hydroxide. The pH of the solution can be from about 3 to about 12, such as from the lower limit selected from any one of 3, 4, 6 and 7 to the upper limit selected from any one of 9, 10 and 12.

[0041] When an indium salt solution is combined with a base, indium hydroxide precipitate is formed. For example... Figure 1A As shown, in step 101, indium hydroxide is then separated by filtration, centrifugation or decantation, indium hydroxide is washed with water, and indium hydroxide is dried.

[0042] The drying of indium hydroxide can be carried out at temperatures ranging from about 20°C to about 120°C, such as the lower limit selected from any one of 20, 25 and 50°C to the upper limit selected from any one of 60, 75, 100 and 120°C, wherein any lower limit can be paired with any upper limit.

[0043] The drying of indium hydroxide can be carried out in the range of about 1 hour to about 15 hours, such as the lower limit selected from any one of 1, 5 and 7 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0044] In one embodiment, a method for producing an alkali metal-doped In₂O₃ catalyst includes contacting indium hydroxide with a solution containing an alkali metal salt to form alkali metal-impregnated indium hydroxide, such as... Figure 1A As shown in step 102.

[0045] In one or more embodiments, the alkali metal salt can be an alkali metal nitrate, an alkali metal chloride, an alkali metal sulfate, or an alkali metal carbonate. For example, the alkali metal nitrate can be lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, or a combination thereof. The alkali metal chloride can be lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, or a combination thereof. The alkali metal nitrate can be lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, or a combination thereof. The alkali metal sulfate can be lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, or a combination thereof. The alkali metal carbonate can be lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, or a combination thereof.

[0046] Alkali metal salt solutions can have concentrations ranging from about 0.01 M to about 4 M, such as a lower limit selected from any one of 0.01, 0.1, 0.5, and 1 M to an upper limit selected from any one of 2, 3, and 4 M, wherein any lower limit can be paired with any upper limit. However, this concentration range will vary depending on the salt, and therefore this range is for illustrative purposes only.

[0047] Contacting indium hydroxide with an alkali metal salt solution can be carried out at temperatures ranging from about 20°C to about 120°C, such as the lower limit selected from any one of 20, 25 and 50°C to the upper limit selected from any one of 60, 75, 100 and 120°C, wherein any lower limit can be paired with any upper limit.

[0048] Contacting indium hydroxide with an alkali metal salt solution can be carried out over a duration of about 1 min to about 12 h, such as the lower limit selected from any one of 1, 10, 30 and 60 min to the upper limit selected from any one of 2, 5, 10, 12 and 15 h, wherein any lower limit can be paired with any upper limit.

[0049] Indium hydroxide can be contacted with an alkali metal salt solution by any method known in the art. For example, a simple wet impregnation can be performed. In this case, the alkali metal salt solution can be added to solid powdered indium hydroxide until it fills the pores of the indium hydroxide. Alternatively, solid powdered indium hydroxide can be added to the alkali metal salt solution and then mixed. Mixing can be accomplished by any method known in the art, such as via a simple stirrer like a stirring rod or using a high-shear stirrer. In this case, the alkali metal in the alkali metal solution diffuses into the indium hydroxide structure.

[0050] When indium hydroxide comes into contact with a solution containing an alkali metal salt, it forms alkali metal-impregnated indium hydroxide. For example... Figure 1A As shown, in step 103, the alkali metal impregnated indium hydroxide is then dried.

[0051] The drying of alkali metal-impregnated indium hydroxide can be carried out at temperatures ranging from about 20°C to about 120°C, such as the lower limit selected from any one of 20, 25 and 50°C to the upper limit selected from any one of 60, 75, 100 and 120°C, wherein any lower limit can be paired with any upper limit.

[0052] The drying of alkali metal-impregnated indium hydroxide can be carried out in the range of about 1 hour to about 15 hours, such as the lower limit selected from any one of 1, 5 and 7 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0053] Methods for producing alkali metal-doped In₂O₃ catalysts include calcining alkali metal-impregnated indium hydroxide to form In₂O₃, such as... Figure 1A Step 104 is shown. As used herein, "calcination" refers to a process of heating a substance in an oxygen-containing atmosphere to form an oxide. In this disclosure, alkali metal-impregnated indium hydroxide is calcined to form an alkali metal-doped In₂O₃ catalyst, or indium hydroxide is calcined to form an In₂O₃ catalyst.

[0054] Calcining alkali metal-impregnated indium hydroxide to form alkali metal-doped In2O3 can be carried out at temperatures ranging from about 250 to about 700 °C, such as the lower limit selected from any one of 250, 300 and 400 °C to the upper limit selected from any one of 500, 600 and 700 °C, wherein any lower limit can be paired with any upper limit.

[0055] Calcining alkali metal-impregnated indium hydroxide to form alkali metal-doped In2O3 can be carried out over a duration of about 1 h to about 15 h, such as the lower limit selected from any one of 1, 3, 5 and 6 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0056] The calcination of alkali metal-impregnated indium hydroxide to form an alkali metal-doped In2O3 catalyst can be accomplished by any method known in the art, such as heating indium hydroxide in air or other oxygen-containing atmospheres in a muffle furnace or tube furnace.

[0057] Calcining alkali metal-impregnated indium hydroxide will form alkali metal-doped In2O3.

[0058] In another implementation, as described above Figure 1A In steps 100 and 101, the indium hydroxide produced via precipitation can be calcined to form indium oxide, contacted with an alkali metal salt solution, dried, and optionally calcined again to produce an alkali metal-doped In2O3 catalyst.

[0059] exist Figure 1AIn step 105, indium hydroxide is calcined to form In2O3.

[0060] Calcination of indium hydroxide to form In2O3 can be carried out at temperatures ranging from about 250 to about 700 °C, such as the lower limit selected from any one of 250, 300 and 400 °C to the upper limit selected from any one of 500, 600 and 700 °C, wherein any lower limit can be paired with any upper limit.

[0061] The calcination of indium hydroxide to form In2O3 can be carried out over a duration of about 1 to about 15 hours, such as the lower limit selected from any one of 1, 3, 5 and 6 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0062] Indium hydroxide can be calcined to form In2O3 by any method known in the art, such as heating in air or other oxygen-containing atmosphere in a muffle furnace or tube furnace.

[0063] In one or more embodiments, after In₂O₃ has been formed by calcination of indium hydroxide, a method for producing an alkali metal-doped In₂O₃ catalyst includes contacting In₂O₃ with an alkali metal salt solution to form an alkali metal-doped In₂O₃ catalyst, such as... Figure 1A Step 106 is shown.

[0064] The alkali metal salt solution can be any alkali metal salt solution previously described. The concentration of the alkali metal salt solution can be the concentration of the alkali metal salt solution previously described.

[0065] Contacting In2O3 with an alkali metal salt solution can be carried out at temperatures ranging from about 20°C to about 120°C, such as the lower limit selected from any one of 20, 25 and 50°C to the upper limit selected from any one of 60, 75, 100 and 120°C, wherein any lower limit can be paired with any upper limit.

[0066] Contacting In2O3 with an alkali metal salt solution can be carried out over a duration of about 1 min to about 12 h, such as the lower limit selected from any one of 1, 10, 30 and 60 min to the upper limit selected from any one of 2, 5, 10, 12 and 15 h, wherein any lower limit can be paired with any upper limit.

[0067] Contact between In₂O₃ and the alkali metal salt solution can be achieved by any method known in the art. For example, a simple wet impregnation can be performed. In this case, the alkali metal salt solution can be added to solid powdered indium hydroxide until it fills the pores of the indium hydroxide. Alternatively, solid powdered indium hydroxide can be added to the alkali metal salt solution and then mixed. Mixing can be accomplished by any method known in the art, such as via a simple stirrer like a stirring rod or using a high-shear stirrer. In this case, the alkali metal in the alkali metal solution diffuses into the indium hydroxide structure.

[0068] When In2O3 comes into contact with a solution containing alkali metal salts, it forms an alkali metal-doped In2O3 catalyst.

[0069] Dry alkali metal-doped In2O3 catalysts can be carried out at temperatures ranging from about 20 °C to about 120 °C, such as from a lower limit selected from any one of 20, 25 and 50 °C to an upper limit selected from any one of 60, 75, 100 and 120 °C, wherein any lower limit can be paired with any upper limit.

[0070] Dry alkali metal-doped In2O3 catalysts can be carried out over a range of about 1 h to about 12 h, such as a lower limit selected from any one of 1, 5 and 7 h to an upper limit selected from any one of 10, 12 and 15 h, wherein any lower limit can be paired with any upper limit.

[0071] In yet another embodiment, a method for producing an alkali metal-doped In₂O₃ catalyst includes mixing an indium salt solution with an alkali metal base to form a precipitate of alkali metal-impregnated indium hydroxide. The alkali metal-impregnated indium hydroxide is then separated by filtration or centrifugation, dried, and calcined to produce the alkali metal-doped In₂O₃ catalyst.

[0072] exist Figure 1B In step 110, the indium salt solution is mixed with an alkali metal base to form a precipitate of alkali metal-impregnated indium hydroxide.

[0073] The alkali metal base can be lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, or a combination thereof. In one or more embodiments, the alkali metal base can be a mixture of one or more alkali metal bases and / or non-alkali metal bases. Non-alkali metal bases can include, but are not limited to, those previously described.

[0074] In one or more embodiments, a base is used to control the pH of the solution to promote the precipitation of indium hydroxide. The pH of the solution can be from about 3 to about 12, such as from the lower limit selected from any one of 3, 4, 6 and 7 to the upper limit selected from any one of 9, 10 and 12.

[0075] The mixing of indium salt solutions with alkali metal bases can be accomplished using any method known in the art, such as a simple stirring mechanism, like a stirring rod, a high-shear mixer, or a shaker.

[0076] The indium salt can be any indium salt previously described.

[0077] When an indium salt solution is mixed with an alkali metal base, it will form a precipitate of alkali metal-impregnated indium hydroxide.

[0078] In one or more embodiments, a method for producing an alkali metal-doped In₂O₃ catalyst includes separating and drying the alkali metal-impregnated indium hydroxide by filtration or centrifugation, such as... Figure 1B As shown in step 112.

[0079] The drying of alkali metal-impregnated indium hydroxide can be carried out at temperatures ranging from about 20°C to about 120°C, such as the lower limit selected from any one of 20, 25 and 50°C to the upper limit selected from any one of 60, 75, 100 and 120°C, wherein any lower limit can be paired with any upper limit.

[0080] The drying of alkali metal-impregnated indium hydroxide can be carried out in the range of about 1 hour to about 12 hours, such as the lower limit selected from any one of 1, 5 and 7 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0081] Methods for producing alkali metal-doped In₂O₃ catalysts include calcining alkali metal-impregnated indium hydroxide to form In₂O₃, such as... Figure 1B As shown in step 114.

[0082] Calcining alkali metal-impregnated indium hydroxide to form alkali metal-doped In2O3 can be carried out at temperatures ranging from about 250 to about 700 °C, such as the lower limit selected from any one of 250, 300 and 400 °C to the upper limit selected from any one of 500, 600 and 700 °C, wherein any lower limit can be paired with any upper limit.

[0083] Calcining alkali metal-impregnated indium hydroxide to form alkali metal-doped In2O3 can be carried out over a duration of about 1 to about 12 hours, such as the lower limit selected from any one of 1, 3, 5 and 6 hours to the upper limit selected from any one of 10, 12 and 15 hours, wherein any lower limit can be paired with any upper limit.

[0084] The calcination of alkali metal-impregnated indium hydroxide to form an alkali metal-doped In2O3 catalyst can be accomplished by any method known in the art, such as heating indium hydroxide in air or other oxygen-containing atmospheres in a muffle furnace or tube furnace.

[0085] Calcining alkali metal-impregnated indium hydroxide will form alkali metal-doped In2O3.

[0086] Reverse water gas shift reaction

[0087] Generally speaking, the reverse water gas shift (RWGS) reaction refers to the conversion of CO2 to CO, as shown in the chemical reaction of Equation 1.

[0088] Equation 1

[0089] The equilibrium of the RWGS reaction is highly temperature-dependent. Under high pressure, the secondary reactions that produce byproducts, as shown in Equations 2 and 3, are favorable. Equations 2 and 3 list the methanation reaction, in which carbon oxides and hydrogen are converted into methane and water. Therefore, when CO is the desired product, a higher reaction temperature and a lower reaction pressure are typically required.

[0090] Equation 2

[0091] Equation 3

[0092] The implementation scheme described herein utilizes an alkali metal-doped In2O3 catalyst for RWGS reactions, providing improved selectivity for enhanced CO production at high pressure (i.e., 50 bar) and moderate temperature (<500 °C) compared to In2O3 catalysts alone.

[0093] Figure 2 An exemplary process for producing CO according to one or more embodiments is shown. Figure 2 A reactor 200 configured to perform an RWGS reaction is shown. The reactor in one or more embodiments may be a fixed-bed continuous flow reactor or other suitable reactors known in the art. In one or more embodiments, reactor 200 may advantageously be operated at a pressure greater than or equal to 20 bar and a temperature less than or equal to 600°C. However, those skilled in the art will understand that the reactor can be operated at any temperature and pressure suitable for performing an RWGS reaction.

[0094] Combination Figure 2 A gas feed 202 containing a mixture of at least hydrogen (H2) gas and CO2 gas is fed into reactor 200. In one or more embodiments, the ratio of H2 gas to CO2 gas is in the range of a lower limit of about 2 moles of H2 to 1 mole of CO2 to an upper limit of about 60 moles of H2 to 1 mole of CO2, for example, the H2:CO2 molar ratio may be about 2:1, 4:1, 10:1, 20:1, 40:1 or 60:1.

[0095] exist Figure 2In this reactor 200, catalyst 204 is loaded and contacted with gas feed 202. Catalyst 204 may be an alkali metal-modified In₂O₃ catalyst as described in one or more embodiments. After contacting gas feed 202 with catalyst 204 in reactor 200 at suitable temperature and pressure, the RWGS reaction of Equation 1 occurs. In one or more embodiments, the RWGS reaction in reactor 200 has a selectivity for CO of at least 97.9%. The RWGS reaction in reactor 200 may have a selectivity for CH₄ of less than 0.8% and a selectivity for CH₃OH of less than 1.2%.

[0096] Combination Figure 2 The products of the RWGS reaction according to one or more embodiments are H₂O 206, byproduct 208, and CO₂ 10. In one or more embodiments, according to the reactions of equations 2 and 3, Figure 2 The byproduct 208 includes CH4 and CH3OH.

[0097] CO stream 210 can be sent to CO conversion process 212 for further processing. Figure 2 CO conversion processes may include methanol synthesis, Fischer-Tropsch synthesis, carbonylation, carbonyl alcohol synthesis, dimethyl ether synthesis, hydroformylation, or other processes that can be used to convert CO.

[0098] Example

[0099] The embodiments and comparative examples described in the following sections are provided to further illustrate the invention, but should not be considered as limiting the invention.

[0100] Preparation of alkali metal modified indium oxide catalysts

[0101] Example 1 was prepared by dissolving 6 g of indium nitrate in 100 mL of water. A 30% aqueous solution of ammonium hydroxide was added to the metal solution with stirring until the pH reached 7. The dispersion was stirred for 10 min, and the indium hydroxide was separated by centrifugation. The solid was washed with water and dried at 80 °C for 15 h. The resulting indium hydroxide was then ground in a mortar.

[0102] Example 2 was prepared from 1.17 g of the sample from Example 1, which had been impregnated with a solution containing 0.074 g of NaNO3 and 0.55 mL of water. The mixture was dried at 100 °C for 1.5 h and then calcined at 350 °C for 3 h to form a Na-doped In2O3 catalyst (Na / In2O3) containing 2 wt% Na.

[0103] Example 3 was prepared using the same procedure as Example 2, except that 0.074 g of NaNO3 was replaced with 0.052 g of KNO3 to form a K-doped In2O3 catalyst (K / In2O3) containing 2 wt% K.

[0104] Example 4 was prepared using the same procedure as Example 2, except that 0.074 g of NaNO3 was replaced with 0.035 g of RbNO3 to form an Rb-doped In2O3 catalyst (Rb / In2O3) containing 2 wt% Rb.

[0105] Example 5 was prepared using the same procedure as Example 2, except that 0.074 g of NaNO3 was replaced with 0.029 g of CsNO3 to form a Cs-doped In2O3 catalyst (Cs / In2O3) containing 2 wt% Cs.

[0106] Comparative Example 1 is a 99.9% commercial indium oxide catalyst (In2O3-Comm) obtained from Sigma-Aldrich.

[0107] Comparative Example 2 was prepared by immersing 0.98 g of commercial indium oxide in a solution containing 0.074 g of NaNO3 and 0.77 mL of water. The mixture was dried at 100 °C for 1.5 h and then calcined at 350 °C for 3 h to form a Na-doped In2O3 catalyst (Na / In2O3-Comm) containing 2 wt% Na.

[0108] Comparative Example 3 was prepared by the same method as Comparative Example 2, except that 0.074 g of NaNO3 was replaced with 0.052 g of KNO3 to form a K-doped In2O3 catalyst containing 2 wt% K (K / In2O3-Comm).

[0109] Comparative Example 4 was prepared by the same method as Comparative Example 2, except that 0.074 g of NaNO3 was replaced with 0.035 g of KNO3 to form an Rb-doped In2O3 catalyst (Rb / In2O3-Comm) containing 2 wt% Rb.

[0110] Comparative Example 5 was prepared by the same method as Comparative Example 2, except that 0.074 g of NaNO3 was replaced with 0.029 g of KNO3 to form a Cs-doped In2O3 catalyst (Cs / In2O3-Comm) containing 2 wt% Cs.

[0111] Reverse water-gas shift reaction in Examples 1-5 and Comparative Examples 1-5

[0112] Examples 1-5 and Comparative Examples 1-5 were used as catalysts for the RWGS reaction to produce carbon monoxide (CO). The reaction bed was loaded with a catalyst selected from Examples 1-5 or Comparative Examples 1-5, and the reaction was carried out at 400°C and 50 bar. A gaseous feed containing hydrogen / carbon dioxide (H2 / CO2) at a 4:1 molar ratio was fed into a parallel reactor of the Avantium reactor, the Flowerence®, at a gas hourly space velocity (GHSV) of 15,000 mL / g / h.

[0113] Catalytic experiments were conducted using an Avantium parallel reactor, Flowerence®. The system distributed a single mixed feed gas stream into 16 channels, ensuring a relative standard deviation of 2%. The mixed feed gas consisted of approximately 20 vol% CO2 and 80 vol% H2. Additionally, He was added to the feed at a rate of 2 mL / min as an internal standard. The target flow rate for each channel was set at 15,000 mL / g / h. A quartz reactor with a length of 30 cm and an inner diameter of 2 μm was used for the measurements.

[0114] To ensure an isothermal zone for the catalytic bed, the tube was initially filled with a bed of coarse SiC (particle size 40, 300 pi) at a depth of 9.5 cm. Subsequently, 50 mg of catalyst particles in the range of 150 pm and 250 pm were loaded. As a control, blank tests were performed using a reactor filled only with SiC after every 45 catalytic runs.

[0115] All samples were pretreated in situ at 400 °C under a pure N2 atmosphere for approximately 1 h before the reaction mixture was introduced. The tubes were then pressurized to approximately 50 bar using a membrane-based pressure controller operated by N2 pressure. The resulting products were analyzed using an Agilent 7890B chromatograph equipped with two loops. One loop was connected to a Column 5 Flaysep Q 6 Ft G3591-80013 and a TCD, while the second loop was connected to a Gaspro 30M, 0.32 mm OD column, followed by an FID.

[0116] Figure 3A and 3B Results of the RWGS reaction for Examples 1-5 and Comparative Examples 1-5 at 400°C, 50 bar and H2 / CO2 feed gas at a molar ratio of 4:1 at 15,000 mL / g / h are shown. Figure 3A and Figure 3B The percentage conversion of CO2 and the percentage selectivity for methane (CH4), methanol (CH3OH), and CO are shown for reactions using the catalysts of Examples 1-5 and Comparative Examples 1-5. Figure 3AAs shown, using In₂O₃ as a catalyst (Example 1) resulted in a CO₂ conversion of 40.7% and a CO selectivity of 95.9%, a CH₄ selectivity of 1.8%, and a CH₃OH selectivity of 1.7%. Alkali metal doping in Example 1 resulted in increased CO selectivity and decreased CH₄ and CH₃OH formation, as... Figure 3A The results of Examples 2-5 are shown as indicated. For example, K / In2O3 (Example 3) achieved a CO2 conversion rate of 41.2%, and a selectivity of 99.6% for CO and 0.2% for CH4 and CH3OH. The results of Comparative Examples 1-5 are... Figure 3B As shown in the figure, the reaction using Comparative Example 5 (Rb / In₂O₃-Comm) exhibited the best results among the tested comparative examples, with a CO₂ conversion of 31.7%, a CO selectivity of 99.2%, a CH₄ selectivity of 0.3%, and a CH₃OH selectivity of 0.4%. Overall, the alkali metal-doped In₂O₃ catalyst in the RWGS reaction leads to better performance than the In₂O₃ catalyst alone, such as... Figure 3A and 3B As shown, Figure 3A and 3B The relatively high CO2 conversion and CO selectivity, and the lower selectivity for CH4 and CH3OH, are shown for the synthesized In2O3 catalyst (Comparative Example 1 compared to Examples 2-5) and the commercial In2O3 catalyst (Comparative Example 1 compared to Comparative Examples 2-5). Furthermore, the overall performance of Comparative Examples 1-5 is inferior to that of Examples 1-5. Figure 3A ) and Comparative Examples 1-5 ( Figure 3B (Compared to the relatively high CO2 conversion rate and CO selectivity, and the low selectivity for CH4 and CH3OH.)

[0117] Figure 3C Examples 1-5 illustrate the RWGS reaction under ambient pressure. Since one of the main objectives of the alkali metal-doped In₂O₃ catalysts according to one or more embodiments is to enable RWGS reactions to occur under high pressure, Examples 1-5 have also been used as catalysts for RWGS reactions in these conditions. Figure 3A Carbon monoxide (CO) is produced under the same reactor conditions, the difference being that the pressure is ambient pressure instead of 50 bar. Figure 3A Compared to the results, the temperature of 400℃, the gas feed rate of 15,000 mL / g / h, and the molar ratio remained unchanged.

[0118] exist Figure 3C In this context, when the RWGS reaction is operated under ambient pressure, the CO2 conversion rate for Examples 1-5 ranges from approximately 20% to approximately 40%. In contrast, Figure 3A The figure shows that when the RWGS reaction is run at a pressure of 50 bar, the CO2 conversion rate for each of Examples 1-5 is approximately 40%. Figure 3C The results and Figure 3A The results show that the alkali metal-doped In2O3 catalysts according to one or more embodiments (i.e., Examples 1-5) perform better at a high reactor pressure of 50 bar than at an ambient reactor pressure.

[0119] At 50 bar, the catalyst that performed best in the example reaction, Example 3 (K / In₂O₃), underwent further testing, where the RWGS reaction was carried out under various reaction conditions. For comparison, Example 1 was run under the same various reaction conditions. Examples 1 and 3 were used as catalysts for the RWGS reaction to produce carbon monoxide (CO), where the reaction bed was loaded with the catalyst of Example 1 or Example 3, and the reaction was carried out under various temperature, pressure, and feed gas GHSV conditions listed in Tables 1-1 and 1-2. In all reactions, the gas feed contained hydrogen / carbon dioxide (H₂ / CO₂) at a molar ratio of 4:1. The same reactor type as described in the previous examples was used.

[0120] [Table 1]

[0121]

[0122] [Table 2]

[0123]

[0124] use Figure 4A Example 3 in the text is used as a catalyst and Figure 4B Example 1, as a catalyst, illustrates the results of RWGS reactions under the various reaction conditions listed in Tables 1 and 2. Increasing the feed gas GHSV from 15,000 mL / g / h to 18,000 mL / g / h or decreasing it to 7,500 mL / g / h at constant reaction temperature and pressure affects the catalyst performance (e.g., ...) of Example 3. Figure 4A Reactions 1-3 in the above examples) and the catalyst performance of Example 1 (e.g.) Figure 4B The reactions shown in 7-9 had no significant effect. Increasing the temperature from 400°C to 450°C under constant pressure and a feed gas GHSV of 7,500 mL / g / h resulted in no significant effect on the reaction in Example 3 (as shown in 7-9). Figure 4A Reactions 3-4 in the example) and catalyst Example 1 (as shown in the example) Figure 4BThe reactions shown in 9-10 exhibit a slightly higher selectivity for CH4 and a decreased selectivity for CO. For catalyst Example 3, at constant pressure and constant gaseous GHSV, decreasing the temperature from 400°C to 350°C had no significant effect on the selectivity for CO, CH4, and CH3OH; however, the CO2 conversion rate decreased significantly with decreasing temperature. Figure 4A Reactions 1 and 5 (feed gas GHSV of 15,000 mL / g / h) and reactions 3 and 6 (feed gas GHSV of 7,500 mL / g / h) are shown in the example. Specifically, when the reaction temperature is decreased from 400°C to 350°C at a constant pressure and 15,000 mL / g / h feed gas GHSV, the CO2 conversion rate decreases from about 41% to about 18%, and when the reaction temperature is decreased from 400°C to 350°C at a constant pressure and 15,000 mL / g / h feed gas GHSV, the CO2 conversion rate decreases from about 40% to about 26%. In contrast, for catalyst example 1, at a constant pressure and constant gas GHSV, decreasing the temperature from 400°C to 350°C results in a decrease in the selectivity of CO, CH4, and CH3OH. Furthermore, as Figure 4B As shown in reactions 7 and 11 (feed gas GHSV of 15,000 mL / g / h) and reactions 8 and 12 (feed gas GHSV of 7,500 mL / g / h), the CO2 conversion rate decreases significantly with decreasing temperature. In summary, with indium oxide catalyst ( Figure 4B Compared to Example 1 shown, when using an alkali metal-doped indium oxide catalyst ( Figure 4A In Example 3 shown, changes to reaction conditions, such as temperature and feed gas GHSV, have little effect on the selectivity of CO, CH4, and CH3OH, as well as the conversion rate of CO2. Furthermore, alkali metal-doped indium oxide can operate at temperatures as low as 350°C with negligible selectivity for methane and methanol.

[0125] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily understand that many modifications can be made to the exemplary embodiments without substantially departing from the invention. Furthermore, many modifications can be made by those skilled in the art to adapt particular instruments, situations, or materials to embodiments of this disclosure without departing from its essential scope. Therefore, all such modifications are intended to be included within the scope of this disclosure as defined by the appended claims.

[0126] Furthermore, the compositions described herein may contain no components, or compositions not expressly listed or disclosed herein. Any method may lack any steps not described or disclosed herein. Similarly, the term "comprising" is considered synonymous with the term "including". Whenever a method, composition, element, or group of elements is preceded by the transitional term "comprising", it is understood that we also cover the same group of compositions or elements preceded by the transitional terms "substantially composed of", "composed of", "selected from the group of", or "is", and vice versa.

[0127] Unless otherwise stated, all figures used in this specification and related claims to indicate the amount of an ingredient, properties such as molecular weight, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters specified in the following specification and appended claims are approximate values ​​and may differ depending on the desired properties sought to be obtained from one or more embodiments described herein. At least, not in an attempt to limit the application of the doctrine of equivalents within the scope of the claims, each numerical parameter should be interpreted at least based on the number of significant figures reported and by applying common rounding techniques.

Claims

1. A composition comprising: Indium oxide catalysts, including those with alkali metal dopants.

2. The composition according to claim 1, wherein the alkali metal dopant comprises a component selected from Li + Na + K + 、Rb + Cs + and Fr + The group consists of alkali metal cations.

3. The composition according to any one of claims 1 or 2, wherein the composition comprises 0.5 to 10% by weight of the alkali metal dopant.

4. A method for producing an indium oxide catalyst comprising an alkali metal dopant, comprising: A solution of indium salt is mixed with an alkali to form a precipitate of indium hydroxide; The precipitated indium hydroxide is contacted with a solution comprising an alkali metal salt to produce alkali metal-impregnated indium hydroxide. and Calcination of the alkali metal-impregnated indium hydroxide to form indium oxide; and This forms the indium oxide catalyst, which includes alkali metal dopants.

5. The method of claim 4, wherein the solution of the alkali metal salt comprises a salt selected from Li. + Na + K + 、Rb + Cs + and Fr + The group consists of alkali metal cations.

6. The method according to claim 4 or 5, wherein the solution of the alkali metal salt has a concentration of 0.01 M to 4 M.

7. The method according to any one of claims 4 to 6, wherein the indium salt comprises an indium compound selected from the group consisting of indium nitrate, indium acetate, indium chloride, indium oxalate and indium sulfate in any hydrated form.

8. The method according to any one of claims 4 to 7, wherein the base is selected from the group consisting of ammonium hydroxide, alkali metal hydroxide or quaternary ammonium hydroxide and mixtures thereof.

9. The method according to any one of claims 4 to 8, wherein calcining the alkali metal-impregnated indium hydroxide to form indium oxide further comprises heating the alkali metal-impregnated indium hydroxide in an oxygen-containing atmosphere to form the indium oxide catalyst comprising an alkali metal dopant.

10. The method according to any one of claims 4 to 9, wherein the calcination of the alkali metal-impregnated indium hydroxide to form indium oxide occurs at a temperature in the range of 250°C to 700°C.

11. The method according to any one of claims 4 to 10, wherein calcination of the alkali metal-impregnated indium hydroxide to form indium oxide occurs over a duration ranging from 1 h to 15 h.

12. A method for producing carbon monoxide, comprising: In a reactor, a gas feed is brought into contact with a catalyst, wherein the catalyst comprises: Indium oxide catalysts, including those with alkali metal dopants.

13. The method of claim 12, wherein the catalyst has a selectivity for carbon monoxide of at least 97.9%.

14. The method according to claim 12 or 13, wherein the catalyst has a selectivity for methane of less than 0.8%.

15. The method according to any one of claims 12 to 14, wherein the catalyst has a selectivity for methanol of less than 1.2%.

16. The method according to any one of claims 12 to 15, wherein the method is performed at a temperature of less than or equal to 600°C.

17. The method according to any one of claims 12 to 16, wherein the method is carried out at a pressure of less than or equal to 50 bar.

18. The method according to any one of claims 12 to 17, wherein the gas feed comprises a mixture of at least hydrogen gas and carbon dioxide gas.

19. The method of claim 18, wherein the gas feed comprises a molar ratio of hydrogen to carbon dioxide of 2:1 to 60:1.

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