A catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-gas shift reaction and its preparation method.

Abstract

This invention discloses a catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-gas shift reaction and its preparation method. The catalyst is supported by cerium oxide in the form of nanorods, and the active component is nickel-indium metal nanoparticles located on the support. The catalyst is obtained through the preparation of the support, the preparation of the metal oxide supported on the support, and the preparation of the final catalyst by high-temperature reduction. The entire preparation process is simple and controllable. After the indium is introduced, a nickel-indium alloy is formed after reduction. Due to the intermetallic effect, the indium atoms separate the nickel atoms, which leads to a change in the adsorption strength of the reaction intermediates, thereby weakening the adsorption strength of carbon monoxide and enabling the carbon monoxide to be desorbed quickly, avoiding the over-hydrogenation of carbon monoxide. The preparation method of this invention is simple and low-cost. The catalyst achieves the preparation of highly selective carbon monoxide under low-temperature conditions, effectively reducing the energy consumption of the reverse water-gas shift reaction and improving the efficiency of the reverse water-gas shift reaction.

Description

Technical Field

[0001] This invention belongs to the field of reverse water-gas shift synthesis of carbon monoxide, and relates to a catalyst for low-temperature reverse water-gas shift reaction synthesis of carbon monoxide and its preparation method. Background Technology

[0002] As global warming intensifies, mitigating the greenhouse effect to promote sustainable development has become increasingly important. Therefore, the chemical conversion of CO2 with hydrogen has enormous application potential as an effective carbon reduction technology. Since existing chemical industries primarily use syngas (CO and H2) as raw materials for fuels and most chemicals, the reverse steam shift reaction is considered a bridge between CO2 and CO, enabling them to enter the carbon cycle economy. The specific reaction process is as follows.

[0003] CO2+H2=CO+H2O ΔH=+42.1kJ / mol

[0004] CO2+4H2=CH4+2H2O ΔH=-165.0kJ / mol

[0005] While the reverse water-gas shift reaction is thermodynamically considered favorable at high temperatures, high temperatures often lead to catalyst sintering and deactivation, and the energy consumed at high temperatures is enormous, making the high-temperature route less economical. At relatively low temperatures, the main product is methane, significantly reducing the selectivity for the target product, carbon monoxide. Therefore, researching efficient and stable catalysts at low temperatures is essential.

[0006] Nickel-based catalysts have been extensively studied due to their low cost and excellent low-temperature carbon dioxide conversion efficiency. However, they also exhibit relatively poor stability and low selectivity for carbon monoxide. Previous reports indicate that the low selectivity of nickel-based catalysts for carbon monoxide is primarily due to strong adsorption of activated carbon monoxide, preventing its timely desorption and subsequent hydrogenation to produce methane. This excessive hydrogenation of carbon monoxide directly reduces its selectivity, posing a significant challenge for the efficient catalytic conversion of carbon dioxide to carbon monoxide at low temperatures.

[0007] To address the above problems, this invention is proposed. Summary of the Invention

[0008] This invention aims to provide a catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-gas shift reaction and its preparation method. The support is cerium oxide in the form of nanorods, and the active component is nickel-indium metal nanoparticles located on the support. The catalyst is obtained through the preparation of the support, the preparation of the metal oxide supported on the support, and the preparation of the final catalyst by high-temperature reduction. The entire preparation process is simple and controllable. After the indium is introduced, it is reduced to form a nickel-indium alloy. Due to the intermetallic effect, the indium atoms separate the nickel atoms, which leads to a change in the adsorption strength of the reaction intermediates, thereby weakening the adsorption strength of carbon monoxide. This allows carbon monoxide to be desorbed quickly, avoiding excessive hydrogenation of carbon monoxide, thus greatly improving the selectivity of carbon monoxide and exhibiting superior catalytic activity in the low-temperature reverse water-gas shift reaction for the synthesis of carbon monoxide.

[0009] The technical solution of the present invention is as follows:

[0010] A catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-vapor shift reaction is disclosed. The support is cerium oxide in the form of nanorods. The active component includes nickel-indium metal nanoparticles located on the support. Based on the total mass of the catalyst, the loading of nickel is 0.1-50%, and the loading of indium is 0-50%.

[0011] As a limitation of the present invention, the length of the carrier nanorod is 20-200 nm; the size of the active component nickel-indium metal nanoparticles is 5-20 nm.

[0012] This invention also provides a method for preparing a catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-gas shift reaction, comprising the following steps in sequence:

[0013] (1) Preparation of the carrier

[0014] (1A) Prepare a mixed aqueous solution of cerium nitrate hexahydrate and indium nitrate hexahydrate respectively, and mix them with sodium hydroxide solution. Stir until homogeneous, and transfer the homogeneous solution to a crystallization reactor. Crystallize at 80-160℃ for 12-48h.

[0015] (1B) The crystallized product was centrifuged and washed with deionized water until neutral. It was dried at 60-120°C for 6-24 hours. After drying, it was ground and placed in a muffle furnace for calcination. The solid powder collected after calcination was cerium oxide nanorods loaded with indium oxide.

[0016] (2) Preparation of nickel oxide supported on a carrier

[0017] Prepare an aqueous solution of nickel nitrate hexahydrate, then add the aqueous solution of nickel nitrate hexahydrate dropwise onto the support, dry at 60-120℃ for 6-48 h, and calcine after drying to obtain a catalyst co-supported with indium oxide and nickel oxide on cerium oxide;

[0018] (3) High-temperature reduction to prepare the final catalyst

[0019] The product obtained in step (2) was reduced and activated under a hydrogen atmosphere to obtain a cerium oxide-supported nickel-indium alloy nanoparticle catalyst.

[0020] As a limitation of the preparation method of the present invention, in step (1A), the cerium ion aqueous solution is prepared from cerium nitrate hexahydrate, the indium ion aqueous solution is prepared from indium nitrate hexahydrate, and the molar ratio of cerium nitrate hexahydrate, indium nitrate hexahydrate and sodium hydroxide is 1:(0~1):96.

[0021] As a second limitation of the preparation method of the present invention, in step (1B), the calcination temperature is 400-700°C and the calcination time is 2-8 hours.

[0022] The calcination process of this invention is carried out in an air atmosphere, and an oxidation reaction occurs. This temperature affects the crystal structure of the cerium oxide nanorods and the concentration of oxygen vacancies on the catalyst surface.

[0023] As a third limitation of the preparation method of the present invention, in step (2), the concentration of the nickel nitrate hexahydrate aqueous solution is 1 to 6 mol / L.

[0024] In this step, the concentration of the nickel nitrate hexahydrate aqueous solution affects the stacking state of nickel ions. Too high a concentration will cause the nickel oxide particles to agglomerate after calcination, while too low a concentration will affect the density of active sites.

[0025] As a fourth limitation of the preparation method of the present invention, in step (2), the calcination temperature is 400-700℃ and the calcination time is 2-8h.

[0026] The calcination process of this invention is carried out in an air atmosphere, where an oxidation reaction occurs. This temperature affects the particle size of nickel oxide and indium oxide nanoparticles.

[0027] The preparation method of the present invention has another limitation: in step (3), the reduction and activation temperature is 300-700℃ and the time is 0.5-2h.

[0028] The preparation method described above in this invention is a whole in which each step is closely related and influences the others, ultimately determining the morphology, structure, and catalytic performance of the prepared catalyst product.

[0029] The beneficial effects achieved by the present invention after adopting the above technical solution are as follows:

[0030] 1. The carrier of this invention is cerium oxide in the form of nanorods. Cerium oxide has good oxygen vacancies. The presence of oxygen vacancies can better adsorb and activate carbon dioxide molecules, while inhibiting the sintering and coking of nickel-based catalysts. Cerium oxide in the form of nanorods exposes different types of crystal faces. The dominant crystal face exposed by cerium oxide nanoparticles is (111), while the nanorod-shaped cerium oxide mainly exposes the (110) crystal face. Compared with ordinary cerium oxide nanoparticles, the nanorod-shaped cerium oxide (110) crystal face can generate more oxygen vacancies. This is because the oxygen vacancy formation energy of the (110) face is lower, which is more conducive to the formation of oxygen vacancies. This leads to different oxygen vacancy concentrations generated by different crystal faces. The increase of oxygen vacancies can promote the adsorption of carbon dioxide, which is more conducive to the capture of raw materials in the low-temperature reverse water vapor shift reaction.

[0031] 2. After the indium element is introduced into the catalyst of the present invention, a nickel-indium alloy is formed through reduction. Due to the intermetallic effect, the indium atoms separate the nickel atoms, which leads to a change in the adsorption strength of the reaction intermediates, thereby weakening the adsorption strength of carbon monoxide. This allows carbon monoxide to be desorbed quickly, avoiding excessive hydrogenation of carbon monoxide and thus greatly improving the selectivity of carbon monoxide.

[0032] 3. The catalyst of the present invention exhibits very high low-temperature stability when catalyzing the synthesis of carbon monoxide in a low-temperature reverse water-gas shift reaction. After 72 hours of reaction, the CO2 conversion rate does not decrease significantly, and the CO selectivity is as high as 99.5% or more.

[0033] 4. The preparation method of this invention is simple and low in cost. The catalyst enables the preparation of carbon monoxide with high selectivity under low temperature conditions, effectively reducing the energy consumption of the reverse water-gas shift reaction and improving the efficiency of the reverse water-gas shift reaction.

[0034] This invention is applicable to the preparation of catalysts for the synthesis of carbon monoxide via low-temperature reverse water-gas shift reaction.

[0035] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0036] Instruction manual illustrations

[0037] Figure 1 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 XRD pattern of the product after calcination during the preparation of / CeO2 catalyst;

[0038] Figure 2Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 XRD pattern of the product after hydrogen reduction during the preparation of / CeO2 catalyst;

[0039] Figure 3 The Ni-In catalyst prepared in Example 3 0.15 High-resolution TEM image of / CeO2;

[0040] Figure 4 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 Raman spectrum of the product after calcination during the preparation of / CeO2 catalyst;

[0041] Figure 5 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / Ce-XPS image of CeO2 catalyst after hydrogen reduction during preparation;

[0042] Figure 6 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / O-XPS image of the products after hydrogen reduction during the preparation of CeO2 catalyst;

[0043] Figure 7 Examples 1-4 show the prepared Ni-In... 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / In-XPS image of the products after hydrogen reduction during the preparation of CeO2 catalyst;

[0044] Figure 8NiO / CeO2 and NiO-In prepared for Comparative Example 1 and Example 3, respectively. 0.15 / CeO2 catalyst preparation process: CO2 desorption of calcined product CO2 during temperature programmed rise (see attached diagram);

[0045] Figure 9 Comparative Examples 1 and 3 respectively show the prepared Ni / CeO2 and Ni-In. 0.15 / CeO2 catalyst reduction of CO product after temperature programmed desorption during preparation (see attached diagram);

[0046] Figure 10 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / CeO2 catalyst at a space velocity of 24000 mL / g cat • Curve of CO2 conversion rate versus temperature under the condition of h and CO2:H2 = 1:4;

[0047] Figure 11 Comparative Example 1 and Examples 1-4 show the prepared Ni / CeO2 and Ni-In, respectively. 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / CeO2 catalyst at a space velocity of 24000 mL / g cat • The curve showing the change in CO selectivity of the reaction product as a function of temperature under the conditions of h and CO2:H2 = 1:4;

[0048] Figure 12 Comparative Example 1 and Examples 1-4 show the prepared Ni / CeO2 and Ni-In, respectively. 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 / CeO2 catalyst at a space velocity of 24000 mL / g cat • The curve of CO yield as a function of temperature under the conditions of h and CO2:H2 = 1:4;

[0049] Figure 13 The Ni / CeO2 catalyst of Comparative Example 1 and the Ni-In catalyst of Example 3 0.15 / CeO2 catalyst under reaction conditions of 400℃ and 24000 mL / g cat·h, CO2:H2=1:4 conditions, CO2 conversion rate and product selectivity as a function of reaction time. Detailed Implementation

[0050] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all experimental and detection methods used in the following embodiments are existing experimental and detection methods.

[0051] (I) Catalyst Preparation

[0052] The following specific embodiments prepared a nickel metal catalyst supported on a cerium oxide support, wherein the cerium oxide support was in the form of nanorods, and indium may or may not have been introduced into the cerium oxide support. The prepared catalyst was dried, calcined, pressed into tablets, sieved, and packed into a fixed bed. All chemical reagents used in this invention were of analytical grade.

[0053] Comparative Example 1: Preparation of Ni / CeO2 catalyst

[0054] (1) Weigh 19.2g of sodium hydroxide and dissolve it in 60mL of water; then weigh 2.3g of cerium nitrate hexahydrate and dissolve it in 5mL of water, and rinse the centrifuge tube with 5mL of water; mix the cerium nitrate hexahydrate aqueous solution with the sodium hydroxide solution, then add 10mL of water, transfer the mixed solution to a hydrothermal crystallization kettle, and stir for 30min; then place it in a 100℃ oven for hydrothermal crystallization for 24h; dilute the solution to neutral with deionized water, centrifuge and dry at 60℃ for 10h, grind after drying and place it in a muffle furnace at 600℃ for calcination for 4h, and cool to obtain a light yellow cerium oxide nanorod carrier;

[0055] (2) Weigh 1.04 g of nickel nitrate hexahydrate and prepare a 1.5 mL solution. Weigh 1.8 g of cerium oxide support. Add the prepared nickel nitrate hexahydrate solution dropwise to the cerium oxide support until it is mixed evenly. After standing at room temperature for 6 h, transfer it to an oven at 120 °C and dry for 24 h. Then calcine it in a muffle furnace at 600 °C for 4 h. Finally, place the calcined catalyst in a reaction apparatus, introduce hydrogen gas, and reduce it at 600 °C for 1 h to obtain cerium oxide-supported Ni / CeO2, wherein the final loading of Ni is 10 wt%.

[0056] Example 1: Ni-In 0.05 Preparation of / CeO2 catalyst

[0057] The preparation method of the catalyst in Example 1 is similar to that of the catalyst in Comparative Example 1, except that indium is introduced in step (1). Specifically, 1.653 g of cerium nitrate hexahydrate and 0.06 g of indium nitrate hexahydrate are added simultaneously in this step. Each is dissolved in 5 mL of water to prepare a solution. The two solutions are then mixed and then mixed with sodium hydroxide solution to prepare the indium-introduced cerium oxide support (denoted as In). 0.05 Ni-In is prepared by loading nickel onto the CeO2 support in step (2). 0.05 The catalyst is a CeO2 catalyst, in which Ni is loaded at 10 wt% in the final catalyst and indium is loaded at a Ce:In atomic ratio of 95:5.

[0058] Example 2: Ni-In 0.10 Preparation of / CeO2 catalyst

[0059] The preparation method of the catalyst in Example 2 is similar to that of the catalyst in Comparative Example 1, except that indium is introduced in step (1). Specifically, 1.563 g of cerium nitrate hexahydrate and 0.12 g of indium nitrate hexahydrate are added simultaneously in this step. Each of these two substances is dissolved in 5 mL of water to prepare a solution. Then, the two solutions are mixed and then mixed with sodium hydroxide solution to prepare the indium-introduced cerium oxide support (denoted as In). 0.10 Ni-In is prepared by loading nickel onto the CeO2 support in step (2). 0.10 / CeO2 catalyst, wherein the Ni loading in the final catalyst is 10wt%, and the indium loading is Ce:In atomic ratio of 90:10.

[0060] Example 3: Ni-In 0.15 Preparation of / CeO2 catalyst

[0061] The preparation method of the catalyst in Example 3 is similar to that of the catalyst in Comparative Example 1, except that indium is introduced in step (1). Specifically, 1.476 g of cerium nitrate hexahydrate and 0.18 g of indium nitrate hexahydrate are added simultaneously in this step. Each of these two substances is dissolved in 5 mL of water to prepare a solution. Then, the two solutions are mixed and then mixed with sodium hydroxide solution to prepare the indium-introduced cerium oxide support (denoted as In). 0.15 Ni-In is prepared by loading nickel onto the CeO2 support in step (2). 0.15 The catalyst is a CeO2 catalyst, in which Ni is loaded at 10 wt% in the final catalyst and indium is loaded at a Ce:In atomic ratio of 85:15.

[0062] Example 4: Ni-In 0.30Preparation of / CeO2 catalyst

[0063] The preparation method of the catalyst in Example 4 is similar to that of the catalyst in Comparative Example 1, except that indium is introduced in step (1). Specifically, 1.216 g of cerium nitrate hexahydrate and 0.36 g of indium nitrate hexahydrate are added simultaneously in this step. Each of these two substances is dissolved in 5 mL of water to prepare a solution. Then, the two solutions are mixed and then mixed with sodium hydroxide solution to prepare the indium-introduced cerium oxide support (In). 0.30 Ni-In is prepared by loading nickel onto the CeO2 support in step (2). 0.30 The catalyst is a CeO2 catalyst, in which Ni is loaded at 10 wt% in the final catalyst and indium is loaded at a Ce:In atomic ratio of 70:30.

[0064] (II) Catalyst Characterization

[0065] Figure 1 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 XRD pattern of the product after calcination (second calcination) during the preparation of the / CeO2 catalyst. From Figure 1 The characteristic peaks of the cerium oxide support can be clearly observed. After calcination, nickel exists in the form of nickel oxide and indium exists in the form of indium oxide. This indicates that most of the indium is loaded as an oxide on the surface of the cerium oxide support and does not enter the cerium oxide lattice.

[0066] Figure 2 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The XRD pattern of the product after hydrogen reduction during the preparation of the / CeO2 catalyst shows that all catalysts have obvious cerium oxide characteristic peaks after reduction. In the catalyst of Comparative Example 1, nickel exists in the metallic state, while in the catalysts prepared in Examples 1-4, nickel and indium form an alloy after indium is introduced, indicating that nickel and indium migrate to form a nickel-indium alloy after hydrogen reduction.

[0067] Figure 3 The Ni-In catalyst prepared in Example 3 0.15High-resolution TEM images of / CeO2 clearly show that the carrier is a nanorod structure with a length of 20–200 nm. Simultaneously, the high-resolution TEM images also reveal a nickel-indium alloy phase with alloy particle sizes of 5–20 nm, which is consistent with… Figure 2 The XRD results are consistent.

[0068] Figure 4 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 Raman spectra of the product after calcination (second calcination) during the preparation of the / CeO2 catalyst. From Figure 4 As can be seen, cerium oxide is present at 550-600 cm⁻¹. -1 and 450cm -1 Each has one peak, which are attributed to oxygen vacancies and cerium oxide F, respectively. 2g The peak at 450 cm⁻¹ after the introduction of indium into the catalyst. -1 The peak position did not shift significantly, indicating that indium did not enter the cerium oxide lattice, which is consistent with... Figure 1 The XRD results were consistent. 550-600cm -1 The relatively increased proportion of peaks indicates that the introduction of indium has led to a certain increase in oxygen vacancies on the support.

[0069] Figure 5 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The Ce-XPS image of the product after hydrogen reduction during the preparation of the / CeO2 catalyst shows that the CeO2 catalyst exhibits significant oxidation after the introduction of indium. 3+ The amount of Ce increased to a certain extent, indicating that the oxygen vacancy concentration in the carrier increased. However, after excessive introduction of indium, Ce... 3+ The reduced proportion may be due to a decrease in the cerium content in the carrier.

[0070] Figure 6 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 O-XPS images of the products after hydrogen reduction during the preparation of the / CeO2 catalyst, from... Figure 6As can be seen, O v The amount of indium increases with the introduction of indium, which further confirms that the introduction of indium can increase the oxygen vacancy concentration of the support.

[0071] Figure 7 The Ni-In samples prepared in Examples 1-4 respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The In-XPS diagram of the product after hydrogen reduction during the preparation of the / CeO2 catalyst shows that most of the reduced In exists in a metallic state, which is a prerequisite for it to form an alloy with nickel.

[0072] Figure 8 NiO / CeO2 and NiO-In prepared for Comparative Example 1 and Example 3, respectively. 0.15 The CO2 adsorption process of the / CeO2 catalyst after calcination (second calcination) is shown in the figure. As can be seen from the figure, the adsorption capacity of the catalyst for CO2 is enhanced after the introduction of indium. The main reason is that the introduction of indium increases the oxygen vacancies on the catalyst surface, thereby promoting the adsorption of CO2.

[0073] Figure 9 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Example 3, respectively 0.05 The / CeO2 catalyst undergoes a temperature-programmed desorption process during the reduction of CO from the product (see attached diagram). Figure 9 It is evident that the adsorption capacity of CO decreases after indium is introduced and forms a nickel-indium alloy with nickel. This may help CO products to desorb quickly from the catalyst surface, thereby improving the selectivity of CO.

[0074] (III) Catalyst Evaluation

[0075] The catalyst powder prepared above was compressed into tablets, sieved to obtain catalyst particles of 20-40 mesh, and mixed evenly with 20-40 mesh quartz sand. The particles were then packed into a quartz tube-type fixed-bed reactor with an inner diameter of Φ6 mm and a length of 40 cm. The reactor was then pretreated at 600℃ for 1 h in an H2 / N2 mixed gas, and the temperature was lowered to the reaction temperature under a nitrogen atmosphere. Subsequently, carbon dioxide, hydrogen, and nitrogen (gas volume ratio of 1:4:2) were introduced into the reactor at a flow rate of 40 mL / min for reaction, with nitrogen serving as both the carrier gas and internal standard. The gaseous products after reaction were condensed, separated, dried, and analyzed by gas chromatography-8860.

[0076] The reaction data and analysis results are as follows.

[0077] Figure 10Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The graph shows the CO2 conversion rate of the / CeO2 catalyst as a function of temperature. It can be seen that the catalyst in Comparative Example 1 has a relatively high CO2 conversion rate, possibly due to the very high CO2 conversion capacity of nickel metal. The introduction of indium significantly reduces the CO2 conversion rate, possibly because strong CO2 adsorption makes further hydrogenation difficult, or because the alloying of nickel and indium reduces the CO2 hydrogenation performance. However, the CO2 conversion rate of Comparative Example 1 decreases with increasing reaction temperature, while the CO2 conversion rate of the catalyst after indium introduction gradually increases. This may be due to a change in the reaction pathway; Comparative Example 1 mainly involves methanation, while the examples mainly involve reverse water-gas shift reaction.

[0078] Figure 11 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The graph shows the CO selectivity of the reaction products with the / CeO2 catalyst as a function of temperature, from... Figure 11 It is evident that the CO content of the catalyst in Comparative Example 1 is very low at temperatures below 450°C, while the main product in the examples is CO. This indicates that the introduction of indium alters the reaction pathway.

[0079] Figure 12 Ni / CeO2 and Ni-In prepared for Comparative Example 1 and Examples 1-4, respectively 0.05 / CeO2、Ni-In 0.10 / CeO2、Ni-In 0.15 / CeO2、Ni-In 0.30 The graph shows the CO yield as a function of temperature in the reaction with the / CeO2 catalyst. Figure 12 As can be seen, the CO yield of Comparative Example 1 is very low at temperatures below 450°C, while the CO yields of Examples 1-4 are close to the equilibrium yield at low temperatures, especially the Ni / CeIn yield of Example 3. 0.15 The catalyst has a very high CO yield.

[0080] Figure 13 The Ni / CeO2 catalyst of Comparative Example 1 and the Ni-In catalyst of Example 3 0.15 The graph shows the change in CO2 conversion rate and product selectivity of the / CeO2 catalyst over reaction time. Figure 13As can be seen, at 400℃, the Ni / CeO2 catalyst of Comparative Example 1 exhibits high CO2 hydrogenation performance, with an initial conversion rate reaching 78% and a methane selectivity approaching 99.9%, indicating that the Ni / CeO2 catalyst of Comparative Example 1 primarily undergoes methanation; while the Ni-In catalyst of Example 3... 0.15 The / CeO2 catalyst exhibits very high CO selectivity, exceeding 99.5%, indicating that it primarily undergoes a reverse water-gas shift reaction, with an initial CO2 conversion rate exceeding 38%, approaching the equilibrium conversion rate of the reverse water-gas shift reaction. As is well known, the methanation pathway involves stepwise hydrogenation of adsorbed intermediates. In the reverse water-gas shift reaction pathway, intermediates can rapidly decompose to produce CO, which then diffuses quickly. Compared to the methanation pathway, the reverse water-gas shift pathway has the advantage of lower intermediate adsorption intensity.

[0081] In addition, the Ni-In prepared in Example 3 0.15 The / CeO2 catalyst exhibits very high low-temperature stability. After 72 hours of reaction, the CO2 conversion rate did not decrease significantly, and the CO selectivity remained above 99.5%, indicating that the catalyst has low-temperature and high-efficiency reverse water-gas shift performance.

[0082] Examples 5-7

[0083] In this embodiment, a catalyst for the synthesis of carbon monoxide via a low-temperature reverse water vapor shift reaction was prepared. The preparation process was similar to that in Example 2, except that the technical parameters in the preparation process were different, as shown in the table below.

[0084]

[0085]

[0086] Comparative Example 2:

[0087] In this embodiment, a non-rod-shaped cerium oxide nano-support was prepared. The specific process is as follows:

[0088] (1) Weigh 6.7 g of cerium nitrate hexahydrate and 8 g of citric acid, mix and dissolve in 17 mL of water, stir at 60 °C until clear, then transfer to a water bath at 90 °C to evaporate the water until a gel is formed, then transfer to an oven at 120 °C to dry for 24 h until a solid foam is formed, grind and place in a muffle furnace at 600 °C for 4 h, then cool to obtain a yellow cerium oxide support.

[0089] (2) Weigh 1.483 g of nickel nitrate hexahydrate and 0.18 g of indium nitrate hexahydrate and prepare a 1.5 mL solution. Weigh 2.7 g of cerium oxide support and add the prepared mixed solution dropwise to the cerium oxide support until it is mixed evenly. After standing at room temperature for 6 h, transfer it to an oven at 120 °C and dry for 24 h. Then calcine it in a muffle furnace at 600 °C for 4 h to obtain cerium oxide supported NiO (NiO-In2O3 / CeO2). Based on the total mass of the catalyst, the final loading of Ni is 10 wt% and Ce / In = 0.85:0.15.

[0090] (3) The catalyst prepared in step (2) is pressed into tablets, sieved to 20-40 mesh, and packed into a fixed-bed reactor. It is then pretreated in an H2 / N2 mixture at 600℃ for 1 h, and the temperature is lowered to the reaction temperature under a nitrogen atmosphere. Then, carbon dioxide, hydrogen, and nitrogen (gas volume ratio of 1:4:2) are introduced into the reactor at a flow rate of 40 mL / min for reaction. Nitrogen is used as the carrier gas and internal standard gas. The gaseous products after reaction are condensed, separated, dried, and then analyzed by gas chromatography-8860.

[0091] The results showed that the CO2 conversion rate of the non-rod-shaped nano-cerium oxide supported Ni-In alloy catalyst was only about 32%, while the CO selectivity reached about 98.5%.

[0092] As can be seen from Comparative Example 2, the cerium oxide support prepared by the above method has no morphology and mainly exposes the (111) crystal plane. Compared with the rod-shaped nano-morphology cerium oxide support of the present invention, although the supporting materials are the same and both are nano-sized, the nanorods expose the (110) crystal plane, which leads to the formation of more oxygen vacancies, thereby promoting the adsorption of CO2 in the reaction raw material gas and thus promoting the improvement of reaction performance.

[0093] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A catalyst for the synthesis of carbon monoxide via a low-temperature reverse water-gas shift reaction, characterized in that, The catalyst support is cerium oxide in the form of nanorods. The active component includes nickel-indium alloy nanoparticles located on the support. Based on the total mass of the catalyst, the nickel loading is 0.1% to 50%, the indium loading is 0% to 50%, and the indium loading is not zero. The sum of the masses of all components in the catalyst is 100%. The term "low temperature" refers to a temperature below 450°C. The catalyst is prepared in the following order: (1) Preparation of the carrier (1A) Prepare mixed aqueous solutions of cerium nitrate hexahydrate and indium nitrate hexahydrate separately, and mix them with sodium hydroxide solution. Stir until homogeneous, and transfer the homogeneous solution to a crystallization reactor. Crystallize at 80 ~ 160 ℃ for 12 ~ 48 h. The molar ratio of cerium nitrate hexahydrate, indium nitrate hexahydrate and sodium hydroxide is 1:(0 ~ 1):96, and the amount of indium nitrate hexahydrate is not 0. (1B) The crystallized product was centrifuged and washed with deionized water until neutral. It was dried at 60 ~ 120 °C for 6 ~ 24 h. After drying, it was ground and placed in a muffle furnace for calcination. After calcination, the solid powder was collected to obtain cerium oxide nanorods loaded with indium oxide. (2) Preparation of nickel oxide supported on a support Prepare an aqueous solution of nickel nitrate hexahydrate, then dropwise add the aqueous solution of nickel nitrate hexahydrate onto cerium oxide nanorods loaded with indium oxide, dry at 60 ~ 120 °C for 6 ~ 48 h, and calcine after drying to obtain indium oxide-nickel oxide co-loaded on cerium oxide; (3) High-temperature reduction to prepare the final catalyst The product obtained in step (2) was reduced and activated at 300 ~ 700 °C for 0.5 ~ 2 h under a hydrogen atmosphere to obtain the catalyst, namely the cerium oxide supported nickel-indium alloy nanoparticle catalyst.

2. The catalyst for synthesizing carbon monoxide via a low-temperature reverse water-gas shift reaction according to claim 1, characterized in that, The length of the cerium oxide nanorods is 20 to 200 nm; the size of the nickel-indium alloy nanoparticles is 5 to 20 nm.

3. The catalyst for synthesizing carbon monoxide via a low-temperature reverse water-gas shift reaction according to claim 1, characterized in that: In step (1B), the roasting temperature is 400 ~ 700 ℃ and the roasting time is 2 ~ 8 h.

4. The catalyst for synthesizing carbon monoxide via a low-temperature reverse water-gas shift reaction according to claim 1, characterized in that: In step (2), the concentration of the nickel nitrate hexahydrate aqueous solution is 1 ~ 6 mol / L.

5. The catalyst for synthesizing carbon monoxide via a low-temperature reverse water-gas shift reaction according to claim 1, characterized in that: In step (2), the roasting temperature is 400 ~ 700℃ and the roasting time is 2 ~ 8 h.

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