Composite spinel catalysts, their preparation, and their application in reverse water-gas shift reaction.

Abstract

This invention belongs to the field of catalyst development technology, and relates to the preparation of a composite spinel catalyst and its application in the reverse water-gas shift reaction. This invention employs a multi-step calcination method to prepare a composite spinel material rich in oxygen vacancies, which exhibits good activity in the reverse water-gas shift reaction. During spinel synthesis, the doping of coordination compounds through multi-step calcination increases the oxygen vacancies and dispersion of the catalyst, and the preservation of the spinel structure contributes to its high stability. Because the metal in the spinel is in a high valence state, it is more easily desorbed to generate CO, thus inhibiting further hydrogenation to methane, resulting in good CO selectivity. The increase in oxygen vacancies promotes CO2 activation, significantly increasing the catalytic activity. This invention develops a method for preparing a composite spinel catalyst and demonstrates excellent catalytic activity in the reverse water-gas shift reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst development technology, and in particular to the preparation of a composite spinel and its application in a reverse water-gas shift reaction, which belongs to the related technologies of comprehensive utilization of carbon dioxide. Technical Background

[0002] Over the past century, global industrialization has led to a dramatic increase in atmospheric carbon dioxide concentration, resulting in a series of climate changes. However, CO2, as a major greenhouse gas, is also an economical and abundant carbon source. Chemically converting CO2 into value-added chemicals and fuels not only reduces CO2 emissions but also brings considerable economic benefits. The reverse water-gas shift (RWGS) reaction is widely considered a promising method, with the reaction product CO serving as a feedstock for methanol synthesis and the Fischer-Tropsch process. However, during the RWGS reaction at atmospheric pressure, CH4 is readily generated as a byproduct. In C1 chemistry, CO is more valuable than CH4. Therefore, designing well-designed nanostructured catalysts with excellent CO selectivity is crucial for the RWGS reaction. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a composite spinel catalyst. The composite spinel catalyst prepared using this invention exhibits good carbon monoxide selectivity and catalytic activity under the reaction conditions of a reverse water-gas shift reaction. During the spinel synthesis process, the doping of coordination compounds involves multi-step calcination, which increases the oxygen vacancies and dispersion of the catalyst, and maintains its high stability due to the preservation of the spinel structure.

[0004] To achieve the above objectives, the present invention adopts the following solution:

[0005] This invention provides a method for preparing a composite spinel catalyst, the method comprising the following steps:

[0006] (1) Dissolve two metal precursors and coordination substances in a solvent, add flocculant and stir until a gel is formed, and dry in an oven to prepare a catalyst precursor.

[0007] The metal is any two of Co, Cu, Fe, Mn, Ni, Zn, and Al, and the molar ratio of the two metals in the two metal precursors is 1-5, preferably 2-4;

[0008] (2) The catalyst precursor prepared above is first calcined in an inert atmosphere, and then calcined again in a specific atmosphere to obtain a composite spinel material rich in oxygen vacancies; Based on the above technical solution, in step (1), the metal precursor is one or more of the following: chloride, nitrate, sulfate, formate, acetate, and citrate of metals Co, Cu, Fe, Mn, Ni, Zn, and Al, preferably one or more of the following: chloride, nitrate, and acetate; the coordinating substance is one or more of the following: melamine, dimethylimidazole, benzimidazole, D-glucose, triethylamine, pyrrolidine, and glutamic acid, preferably one or more of the following: melamine, dimethylimidazole, and triethylamine;

[0009] The solvent is one or more of tetrahydrofuran, petroleum ether, water, methanol, and ethanol, preferably one or more of tetrahydrofuran, methanol, and ethanol;

[0010] The flocculant is one or more of polyacrylamide, 1,2-epoxypropane, diethylene glycol monoethyl ether, and N,N-dimethylformamide, preferably one or more of 1,2-epoxypropane and diethylene glycol monoethyl ether.

[0011] The mass ratio of the two metals is 1-5, preferably 2-4; the mass ratio of the total of the two metals: coordination substance: solvent: flocculant is 1-5: 1-5: 1-20: 1-10, preferably 1-2: 2-5: 5-10: 5-10;

[0012] The drying temperature is 40–150℃, preferably 60–120℃; the drying time is 0.5–6.0h, preferably 1.0–3.0h.

[0013] Based on the above technical solutions, in step (2), the inert atmosphere is one or more of nitrogen, argon, and helium, and the specific atmosphere is one or more of air, oxygen, carbon monoxide, and carbon dioxide.

[0014] Calcination gas flow rate: 10–500 mL / min -1 ·gcat -1 The preferred concentration is 20–250 mL / min. -1 ·gcat -1 The roasting temperature is 300–1200℃, preferably 500–1000℃; the constant temperature roasting time is 0.2–10.0h, preferably 1.0–8.0h;

[0015] Based on the above technical solution, the catalyst is a composite spinel. The elemental content of the catalyst is determined by inductively coupled plasma (ICP), the oxygen vacancies are semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s), and the dispersion is determined by H2 pulsed chemisorption. During its synthesis, the doping of coordination compounds and multi-step calcination increase the oxygen vacancies and dispersion of the catalyst, and its high stability is achieved by maintaining the spinel structure.

[0016] Another aspect of the present invention provides the application of the above-mentioned composite spinel catalyst in the reverse water-gas shift reaction.

[0017] Based on the above technical solutions, in the aforementioned applications, the reaction temperature is 200–700℃ (preferably 300–600℃), the reaction pressure is 0.1–1.0 MPa (preferably 0.1–0.5 MPa), and the gas hourly space velocity (based on catalyst mass) is 5000–48000 mL·gcat. -1 ·h -1 (Preferred concentration: 20000–30000 mL·gcat) -1 ·h -1 The reaction feed gas is a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.0 to 4.0 (preferably 1.0 to 2.0). The reactor adopts a fixed bed, and the feeding method is continuous feeding. The product first passes through a cold tank to remove the generated water, and the tail gas is analyzed by gas chromatography.

[0018] This invention employs a multi-step calcination method to prepare a composite spinel material rich in oxygen vacancies, which exhibits excellent activity in the reverse water-gas shift reaction. During spinel synthesis, the doping of coordination compounds and the multi-step calcination process increase the oxygen vacancies and dispersion of the catalyst, while maintaining the spinel structure, resulting in high stability. The high valence of the metal in the spinel facilitates desorption to form CO, inhibiting further hydrogenation to methane, thus giving the catalyst excellent CO selectivity. The increased oxygen vacancies promote CO2 activation, significantly enhancing catalytic activity. This invention develops a method for preparing a composite spinel catalyst and demonstrates excellent catalytic activity in the reverse water-gas shift reaction. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments, but this does not limit the scope of the invention in any way.

[0020] Example 1

[0021] 1.5 g aluminum nitrate, 0.48 g copper chloride, and 1.0 g dimethylimidazole were dissolved in 10 g methanol, followed by the addition of 5 g 1,2-propylene oxide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 1.5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 900 °C in an argon atmosphere for 2.5 h (gas flow rate 180 mL·min). -1 Then it was calcined in air at 800°C for 5.5 hours (gas flow rate 200 mL / min). -1 Composite spinel catalyst 1 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be approximated to lattice oxygen (O) on the surface. L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.45. TEM characterization revealed egg-yolk-shaped (circular, dark in the center, light on the outer edge) composite spinel CuAl2O4 lattice striations, while XRD characterization showed characteristic peaks of CuAl2O4.

[0022] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 450℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 6000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0023] Example 2

[0024] 1.5 g cobalt sulfate, 0.48 g ferric nitrate, and 1.0 g triethylamine were dissolved in 10 g ethanol, followed by the addition of 5 g N,N-dimethylformamide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 1.5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 2.5 h (gas flow rate 150 mL·min). -1 Subsequently, it was calcined in oxygen at 700°C for 8 hours (gas flow rate 100 mL / min). -1 Composite spinel catalyst 2 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), OA / (O A +O L = 0.43. TEM characterization revealed uniformly distributed egg-yolk-shaped composite spinel FeCo2O4 lattice striations, while XRD characterization showed characteristic peaks of FeCo2O4.

[0025] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 0.1 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.0. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0026] Example 3

[0027] 1.5 g aluminum citrate, 0.48 g copper nitrate, and 1.0 g D-glucose were dissolved in 10 g methanol, followed by the addition of 5 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 600 °C under a nitrogen atmosphere for 2 h (gas flow rate 100 mL·min). -1 Subsequently, it was calcined in carbon monoxide at 400°C for 5 hours (gas flow rate 200 mL·min). -1 Composite spinel catalyst 3 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.46. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, and light at the outer edge) composite spinel CuAl2O4 lattice striations, while XRD characterization showed characteristic peaks of CuAl2O4.

[0028] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 0.1 MPa, and gas hourly space velocity (based on catalyst mass) 20000 mL·gcat. -1 ·h -1The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0029] Example 4

[0030] 1.5 g aluminum acetate, 0.50 g manganese nitrate, and 1.0 g dimethylimidazole were dissolved in 10 g methanol, followed by the addition of 5 g 1,2-propylene oxide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in a helium atmosphere for 4 h (gas flow rate 1500 mL·min). -1 Subsequently, it was calcined in carbon dioxide at 500°C for 8 hours (gas flow rate 150 mL·min). -1 Composite spinel catalyst 4 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.47. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light at the outer edge) composite spinel MnAl2O4 lattice striations, while XRD characterization showed characteristic peaks of MnAl2O4.

[0031] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 600℃, reaction pressure 0.3 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2.0. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0032] Example 5

[0033] 1.6 g aluminum chloride, 0.53 g nickel nitrate, and 1.0 g benzimidazole were dissolved in 10 g tetrahydrofuran, followed by the addition of 5 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 2 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 600 °C in an argon atmosphere for 4 h (gas flow rate 80 mL·min). -1Then it was calcined in air at 900°C for 5 hours (gas flow rate 200 mL / min). -1 A composite spinel catalyst 5 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be approximated to lattice oxygen (O) on the surface. L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.48. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, and light at the outer edge) composite spinel NiAl2O4 lattice striations, while XRD characterization showed characteristic peaks of NiAl2O4.

[0034] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0035] Example 6

[0036] 1.7 g zinc nitrate, 0.48 g aluminum nitrate, and 1.0 g glutamic acid were dissolved in 10 g water, followed by the addition of 5 g N,N-dimethylformamide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 1.5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C under a nitrogen atmosphere for 2 h (gas flow rate 160 mL·min). -1 Subsequently, it was calcined in carbon monoxide at 800°C for 5 hours (gas flow rate 160 mL·min). -1 Composite spinel catalyst 6 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.45. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light at the outer edge) composite spinel ZnAl2O4 lattice striations, while XRD characterization showed characteristic peaks of ZnAl2O4.

[0037] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 480℃, reaction pressure 0.1 MPa, and gas hourly space velocity (based on catalyst mass) 6000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2.0. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0038] Example 7

[0039] 1.72 g zinc nitrate, 0.50 g aluminum nitrate, and 1.2 g dimethylimidazole were dissolved in 10 g ethanol, followed by the addition of 5.0 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 1 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C under a nitrogen atmosphere for 4 h (gas flow rate 170 mL·min). -1 Subsequently, it was calcined in oxygen at 700°C for 5 hours (gas flow rate 210 mL / min). -1 Composite spinel catalyst 7 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be approximated to lattice oxygen (O) on the surface. L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.42. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, and light at the outer edge) composite spinel ZnAl2O4 lattice striations, while XRD characterization showed characteristic peaks of ZnAl2O4.

[0040] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 600℃, reaction pressure 0.3 MPa, and gas hourly space velocity (based on catalyst mass) 30000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2.0. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0041] Example 8

[0042] 1.59 g zinc nitrate, 0.43 g aluminum nitrate, and 2.0 g triethylamine were dissolved in 10 g methanol, followed by the addition of 5 g N,N-dimethylformamide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 3.5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in an argon atmosphere for 2.5 h (gas flow rate 200 mL·min). -1 Then it was calcined in air at 750°C for 5.5 hours (gas flow rate 180 mL / min). -1 A composite spinel catalyst 8 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be approximated to the surface lattice oxygen (O2). L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.43. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light at the outer edge) composite spinel ZnAl2O4 lattice striations, while XRD characterization showed characteristic peaks of ZnAl2O4.

[0043] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 550℃, reaction pressure 0.1 MPa, and gas hourly space velocity (based on catalyst mass) 20000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0044] Example 9

[0045] 1.5 g zinc nitrate, 1.2 g aluminum nitrate, and 2.5 g glutamic acid were dissolved in 10 g petroleum ether, followed by the addition of 5 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 100 °C for 3.5 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 3.5 h (gas flow rate 200 mL·min). -1 Then it was calcined in air at 700°C for 3.5 hours (gas flow rate 200 mL / min). -1 Composite spinel catalyst 9 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), OA / (O A +O L = 0.46. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light on the outer edge) composite spinel ZnAl2O4 lattice striations, while XRD characterization showed characteristic peaks of ZnAl2O4.

[0046] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 650℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 40000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0047] Example 10

[0048] 1.9 g cobalt nitrate, 1.5 g aluminum nitrate, and 1.0 g pyrrolidine were dissolved in 15 g tetrahydrofuran, followed by the addition of 6 g 1,2-epoxypropane and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 2 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 3 h (gas flow rate 180 mL·min). -1 Then it was calcined in air at 700°C for 3 hours (gas flow rate 200 mL / min). -1 A composite spinel catalyst 10 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPSO1s). XPS O1s can be approximated to lattice oxygen (O2) on the surface. L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.48. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light on the outer edge) composite spinel CoAl2O4 lattice striations, while XRD characterization showed characteristic peaks of CoAl2O4.

[0049] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 0.5 MPa, and gas hourly space velocity (based on catalyst mass) 35000 mL·gcat. -1 ·h -1The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0050] Example 11

[0051] 1.5 g ferric nitrate, 0.48 g aluminum nitrate, and 1.0 g glutamic acid were dissolved in 8 g water, followed by the addition of 8 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 2 h (gas flow rate 200 mL·min). -1 Then it was calcined in air at 700°C for 5 hours (gas flow rate 200 mL / min). -1 Composite spinel catalyst 11 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be approximated to the surface lattice oxygen (O2). L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.47. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, light at the outer edge) composite spinel FeAl2O4 lattice striations, while XRD characterization showed characteristic FeAl2O4 peaks.

[0052] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 550℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 25000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0053] Example 12

[0054] 1.9 g copper nitrate, 0.8 g aluminum nitrate, and 1.5 g D-glucose were dissolved in 12 g ethanol, followed by the addition of 4 g 1,2-propylene oxide and stirring until a translucent solid was obtained. The solid was then dried in an oven at 120 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in an argon atmosphere for 4 h (gas flow rate 180 mL·min). -1Then it was calcined in air at 600°C for 8 hours (gas flow rate 170 mL / min). -1 Composite spinel catalyst 12 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPSO1s). XPS O1s can be fitted to the surface lattice oxygen (O2). L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.46. TEM characterization revealed uniformly distributed egg-yolk-shaped (circular, dark in the center, and light at the outer edge) composite spinel CuAl2O4 lattice striations, while XRD characterization showed characteristic peaks of CuAl2O4.

[0055] Evaluation experiments on the reverse water-gas shift reaction were conducted using the prepared composite spinel catalyst. Specific evaluation conditions were as follows: reaction temperature 550℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 15,000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0056] Comparative Example 1

[0057] 1.5 g of copper chloride and 0.48 g of aluminum nitrate were dissolved in 10 g of methanol, followed by the addition of 5 g of 1,2-propylene oxide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 1.5 h to obtain the catalyst precursor. The prepared catalyst precursor was then calcined in air at 800 °C for 5.5 h (gas flow rate 200 mL / min). -1 Spinel catalysts were prepared for comparison 1. Oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to lattice oxygen (O) on the surface. L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.33. TEM characterization revealed spinel CuAl2O4 lattice fringes, while XRD characterization revealed characteristic peaks of CuAl2O4.

[0058] The prepared catalyst was used to conduct an evaluation experiment on the reverse water-gas shift reaction. Specific evaluation conditions were as follows: reaction temperature 450℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0059] Comparative Example 2

[0060] 1.9 g zinc nitrate, 1.5 g aluminum nitrate, and 1.0 g pyrrolidine were dissolved in 15 g tetrahydrofuran, followed by the addition of 6 g 1,2-epoxypropane and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 2 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined in air at 700 °C for 3 h (gas flow rate 200 mL·min). -1 Catalyst Comparative Example 2 was prepared. Oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.24. TEM characterization revealed spinel ZnAl2O4 lattice fringes, while XRD characterization revealed characteristic peaks of ZnAl2O4.

[0061] The prepared catalyst was used to conduct an evaluation experiment on the reverse water-gas shift reaction. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 0.5 MPa, and gas hourly space velocity (based on catalyst mass) 35000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0062] Comparative Example 3

[0063] 1.9 g zinc nitrate, 0.8 g aluminum nitrate, and 20 g D-glucose were dissolved in 12 g ethanol, followed by the addition of 30 g 1,2-propylene oxide and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 120 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 400 °C in an argon atmosphere for 4 h (gas flow rate 180 mL·min). -1 Then it was calcined in air at 600°C for 8 hours (gas flow rate 170 mL / min). -1 Catalyst Comparative Example 3 was prepared. Oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L = 0.15. TEM characterization revealed spinel ZnAl2O4 lattice fringes, while XRD characterization revealed characteristic peaks of ZnAl2O4.

[0064] The prepared catalyst was used to conduct an evaluation experiment on the reverse water-gas shift reaction. Specific evaluation conditions were as follows: reaction temperature 550℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 15,000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.5. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0065] Comparative Example 4

[0066] 1.5 g ferric nitrate, 0.48 g aluminum nitrate, and 0.2 g glutamic acid were dissolved in 8 g water, followed by the addition of 0.2 g diethylene glycol monoethyl ether and stirring until a semi-transparent solid was obtained. The solid was then dried in an oven at 80 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 2 h (gas flow rate 200 mL·min). -1 Then it was calcined in air at 700°C for 5 hours (gas flow rate 200 mL / min). -1 Catalyst Comparative Example 4 was prepared. The oxygen vacancies in the catalyst were semi-quantitatively determined by X-ray photoelectron spectroscopy (XPS O1s). XPS O1s can be fitted to the surface lattice oxygen (O) L ) and surface-adsorbed oxygen (O A ), O A / (O A +O L= 0.20. TEM characterization revealed spinel FeAl2O4 lattice fringes, and XRD characterization revealed characteristic peaks of FeAl2O4.

[0067] The prepared catalyst was used to conduct an evaluation experiment on the reverse water-gas shift reaction. Specific evaluation conditions were as follows: reaction temperature 550℃, reaction pressure 0.2 MPa, and gas hourly space velocity (based on catalyst mass) 25000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0068] Table 1 Performance of different composite spinel catalysts in the reverse water-gas shift reaction

[0069]

[0070]

[0071] The data evaluation results from Examples 1-12 and Comparative Examples 1-3 under various reaction conditions reveal that the composite spinel catalyst with added coordinating agents and subjected to multi-step calcination exhibits better CO2 conversion and CO selectivity, and demonstrates excellent reverse water gas conversion performance. When no coordinating agents are added (Comparative Example 1), the catalyst O A / (O A +O L The oxygen vacancy content decreases, leading to reduced catalytic activity. When multi-step calcination is not performed (Comparative Example 2) or the calcination temperature is too low (Comparative Example 3), the oxygen vacancy content in the catalyst decreases, resulting in reduced reverse water-gas shift activity. When the molar ratio of metal:coordinating agent:solvent:flocculant is not satisfied (5:1:1:1-1:5:20:10), excessive (Comparative Example 3) or insufficient (Comparative Example 4) coordinating agent or flocculant prevents spinel from crystallizing properly, thus reducing the catalyst's CO selectivity. Therefore, the composite spinel catalyst with added coordinating agent and multi-step calcination is rich in more oxygen vacancy sites, thus exhibiting good reverse water-gas shift activity.

[0072] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. The application of a composite spinel catalyst in a reverse water-gas shift reaction, characterized in that, The preparation method of the composite spinel catalyst includes the following steps: (1) Dissolve two metal precursors and coordination substances in a solvent, add flocculant and stir until a gel is formed, dry and prepare catalyst precursor; The metal is any two of Co, Cu, Fe, Mn, Ni, Zn, and Al; the molar ratio of the two metals in the two metal precursors is 1-5; the mass ratio of the total of the two metals: coordination substance: solvent: flocculant is 1-5: 1-5: 1-20: 1-10. (2) The catalyst precursor prepared above is first calcined in an inert atmosphere, and then calcined again in a specific atmosphere to obtain a composite spinel material rich in oxygen vacancies; in step (2), the inert atmosphere is one or more of nitrogen, argon, and helium, and the specific atmosphere is one or more of air, oxygen, carbon monoxide, and carbon dioxide; in step (2), the flow rate of the calcining gas is 10~500 mL / min. -1 gcat -1 The roasting temperature is 300~1200 °C; the constant temperature roasting time is 0.2~10.0 h. In the aforementioned application, the reaction temperature in the reverse water-gas shift reaction is 200~700 °C, the reaction pressure is 0.1~1.0 MPa, and the gas space velocity (gas hourly velocity) is 5000~48000 mL gcat (based on catalyst mass). -1 h -1 The molar ratio of H2 to CO2 in the feed gas is 1.0~4.0; the feed gas is a gas containing both H2 and CO2. The flocculant is one or more of the following: polyacrylamide, 1,2-epoxypropylene, diethylene glycol monoethyl ether, and N,N-dimethylformamide. The coordinating substance is one or more of melamine, dimethylimidazole, benzimidazole, D-glucose, triethylamine, pyrrolidine, and glutamic acid.

2. The application according to claim 1, characterized in that, In step (1), the molar ratio of the two metals in the two metal precursors is 2-4; the mass ratio of the total of the two metals: coordination substance: solvent: flocculant is 1-2: 2-5: 5-10: 5-10; In step (2), the calcination gas flow rate is 20~250 mL / min. -1 gcat -1 The roasting temperature is 500~1000 °C; the constant temperature roasting time is 1.0~8.0 h. In the aforementioned application, the reaction temperature in the reverse water-gas shift reaction is 300~600 °C, the reaction pressure is 0.1~0.5 MPa, and the gas space velocity (gas hourly velocity) is 20000~30000 mL gcat (based on catalyst mass). -1 h -1 The molar ratio of H2 to CO2 in the feed gas is 1.0~2.0; the feed gas is a mixture of CO2 and H2. The flocculant is one or two of 1,2-epoxypropane and diethylene glycol monoethyl ether; The coordinating agent is one or more of melamine, dimethylimidazole, and triethylamine.

3. The application according to claim 1, characterized in that, In step (1), the metal precursor is one or more of the chlorides, nitrates, sulfates, formates, acetates, and citrates of two metals, namely Co, Cu, Fe, Mn, Ni, Zn, and Al; the solvent is one or more of tetrahydrofuran, petroleum ether, water, methanol, and ethanol. The drying temperature is 40~150 °C; the drying time is 0.5~6.0 h.

4. The application according to claim 1, characterized in that, In step (1), the metal precursor is one or more of the chlorides, nitrates, and acetates of two metals selected from Co, Cu, Fe, Mn, Ni, Zn, and Al; the solvent is one or more of tetrahydrofuran, methanol, and ethanol. The drying temperature is 60~120 °C; the drying time is 1.0~3.0 h.

5. The application according to claim 1, characterized in that, The reactor uses a fixed bed and a continuous feeding method. The product first passes through a 0-5℃ cold tank to remove the generated water, and the tail gas is analyzed by gas chromatography.

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