Application of supported nickel-gallium catalyst in reverse water-gas shift reaction

Abstract

The invention relates to the field of catalysts, and relates to an application of a supported nickel-gallium catalyst in a reverse water-gas shift reaction, the supported nickel-gallium catalyst is applied to a fixed bed reactor, the supported nickel-gallium catalyst is firstly subjected to reduction treatment, and then the reverse water-gas shift reaction is performed. The supported nickel-gallium catalyst comprises a metal active component and a carrier, and the catalytic performance of the catalyst on a reverse water-gas shift reaction can be adjusted by adjusting the Ni / Ga ratio, the total loading amount of Ni and Ga and the reduction temperature. The NiGa / SiO2 catalyst is in a low temperature range (lt; the catalyst has very high selectivity and carbon dioxide conversion rate for a reverse water-gas shift reaction, and has very high stability. The catalyst overcomes the problem of excessive proportion of a methane product in a nickel-based catalytic system, so that the proportion of a carbon monoxide product is greatly increased.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly to the application of a supported nickel-gallium catalyst in the reverse water-gas shift reaction. Background Art

[0002] The use of fossil fuels has greatly promoted the development of human society. However, the excessive exploitation and utilization of fossil fuels have rapidly consumed non-renewable resources and led to the large-scale emission of industrial waste gases such as CO2, causing problems such as global warming and bringing great pressure to the ecological environment. Recycling CO2 and converting it into fuels or high-value chemicals is one of the important ways to alleviate the above problems. Among the numerous CO2 treatment methods, treating CO2 through the reverse water-gas shift reaction (CO2 + H2 = CO + H2O) is one of the promising research directions. This process can not only consume CO2, but also be used to adjust the carbon-hydrogen ratio in syngas, and its product CO is easier to be hydrogenated into high-value chemicals (such as being converted into light olefins through Fischer-Tropsch synthesis). In addition, it also has broad application prospects in the field of space exploration.

[0003] The current obstacles to the industrial application of the reverse water-gas shift reaction are the deactivation behaviors such as catalyst agglomeration and carbon deposition caused by high-temperature conditions, and the high energy consumption problem necessary to maintain high temperature. The need to maintain high temperature is because the C=O bond energy is relatively large, and high temperature is required to break through the reaction energy barrier. And thermodynamically, high temperature is beneficial to inhibiting the formation of by-product CH4. Therefore, developing catalysts with high conversion rate, high selectivity and high stability at relatively low temperatures (<500 °C) is the key research direction.

[0004] Transition metals in Groups VIII, IB and IIB (such as Cu, Ni, Pd, Ru and Rh, etc.) have strong bond-breaking ability for the C=O bond and are commonly used in CO2 hydrogenation reactions. Among them, Group IIB metals (such as Cu, Ag and Au, etc.) are beneficial to the formation of CO and less likely to form CH4. Cu-based catalysts almost only produce CO, but their thermal stability is poor. Although Ni-based catalysts have higher thermal stability and catalytic activity compared with Cu-based catalysts, their selectivity for the product CO is poor. Therefore, adjusting the product distribution of Ni-based catalysts in the CO2 hydrogenation reaction to make it a stable and highly active reverse water-gas shift reaction catalyst has strong application value.

[0005] Chinese Patent CN115178276A discloses a Ni / M-S catalyst for the reverse water-gas shift reaction, where M is an oxide and S is the promoter sulfur. This catalyst achieves a CO selectivity close to 100% and a CO2 conversion rate of 25.2% at 500°C. In addition, Dai et al. (Chinese Chemical Letters, 2022, 33, 2590-2594) prepared NiCe-HMS and Ni-HMS confined structure catalysts by a one-pot method. Highly dispersed Ni nanoparticles were formed on their surfaces, suppressing the formation of CH4, and thus showing a CO selectivity of 99.3% at 750°C. Chinese Patent CN113649014A discloses a Ni / ZnO catalyst for the reverse water-gas shift reaction. This catalyst contains a Ni-Zn alloy phase, enabling the catalyst to exhibit a CO2 conversion rate of 21% and a CO selectivity of ≥98% in the CO2 hydrogenation reaction at 400°C. However, the CO2 conversion rate of the Ni-based catalysts reported above is still far from the thermodynamic equilibrium value, and there is still much room for performance improvement. Therefore, it is of great significance to further develop nickel-based catalysts with high activity and stability for the reverse water-gas shift reaction.

[0006] To solve the above problems, the present invention is proposed. Summary of the Invention

[0007] The object of the present invention is to overcome the deficiencies of the prior art and provide an application of a supported nickel-gallium catalyst in the reverse water-gas shift reaction, which has a high CO2 conversion rate, a high CO selectivity, and high stability.

[0008] To achieve the object of the present invention, the specific technical solution of the present invention is as follows:

[0009] The present invention provides an application of a supported nickel-gallium catalyst in the reverse water-gas shift reaction. The supported nickel-gallium catalyst is applied to a fixed-bed reactor. First, the supported nickel-gallium catalyst is subjected to a reduction treatment, and then the reverse water-gas shift reaction is carried out. The conditions of the reverse water-gas shift reaction include: the raw material gas is a mixture of N2, CO2, and H2 with a molar ratio of (5:2:2) to (5:2:8), and the reaction space velocity is 36000-360000 mL·h -1 ·g cat -1, the reduction temperature is 300 - 450 °C, and the reaction pressure is 1 atm; the supported nickel-gallium catalyst comprises a metal active component and a support. The metal active component is Ni and Ga with a molar ratio of 1 - 4:1, and the support is SiO₂. Based on the total mass of the catalyst, the total loading of Ni and Ga elements is 10 - 60 wt%. The catalytic performance for the reverse water-gas shift reaction can be adjusted by regulating the molar ratio of Ni and Ga, the total loading of Ni and Ga, and the reduction temperature. In this catalyst, the SiO₂ support effectively enhances the dispersion of the active component, and the interaction between Ni and Ga forms a Ni-Ga alloy phase, which changes the electronic structure of the metal, weakens the hydrogenation ability for CO₂, thus achieving a significant increase in CO selectivity and obtaining excellent stability.

[0010] Preferably, the preparation method of the supported nickel-gallium catalyst comprises the following steps:

[0011] S1: Mix water and ethanol containing the support thoroughly to obtain a mixed solution A;

[0012] S2: Add precursors of nickel and gallium to the mixed solution A and mix thoroughly to obtain a mixed solution B;

[0013] S3: Introduce a liquid C containing a precipitant into the mixed solution B and mix thoroughly to obtain a mixture;

[0014] S4: Separate the mixture, dry the obtained precipitate, and perform high-temperature treatment to obtain the supported nickel-gallium catalyst for the reverse water-gas shift reaction.

[0015] Preferably, the support in step S1 is SiO₂, the volume ratio of water to ethanol is 1:1 - 3:1, and the mixing method is to ultrasonically treat for 10 - 20 min first and then stir.

[0016] Preferably, the precursors of nickel and gallium in step S2 are one of their nitrates or chlorides, and the mixing method is to stir for 1 - 3 h.

[0017] Preferably, the precipitant in step S3 is one of sodium carbonate, ammonium carbonate, sodium hydroxide, or urea. The dosage of the precipitant is 4 times the amount required to precipitate all metals. The liquid C is slowly added (5 mL·min -1 ) to the mixed solution B through a peristaltic pump, and the mixing method is to stir for 6 - 24 h, and the mixing temperature is 20 - 30 °C.

[0018] Preferably, the separation method in step S4 is suction filtration or centrifugation, the drying temperature is 60 - 120 °C, and the drying time is 10 - 15 h. The gas atmosphere for high-temperature treatment is H₂, and the flow rate is 10 - 100 mL·min -1 , and more preferably 10 - 40 mL·min -1, the treatment temperature is 400 - 800 °C, more preferably 400 - 500 °C, and the treatment time is 2 - 6 h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The supported nickel-gallium catalyst of the present invention is applied to the reverse water-gas shift reaction and has extremely high stability ( Figure 5 ), and within 250 h (400 °C, 1 atm, reaction space velocity 36000 mL·h -1 ·g cat -1 ), the CO2 conversion rate always remains above 35%, the CO selectivity ≥ 95% and shows a slightly increasing trend.

[0021] 2. The present invention determines the preparation conditions of the supported nickel-gallium catalyst that are most conducive to improving the CO yield. It mainly lies in the determination of the preferred Ni / Ga ratio, the preferred total loading of Ni and Ga, and the preferred reduction temperature: Comparing the CO2 hydrogenation performance of NiGa / SiO2 catalysts with different Ni / Ga ratios ( Figure 2 ), it can be seen that when there is no Ga doping, almost only CH4 is produced in the Ni / SiO2 system, but the doping of Ga can greatly improve the selectivity of CO, and the selectivity gradually increases with the decrease of the Ni / Ga ratio until the CO selectivity reaches ≥ 99%. Among them, the CO yield of 2Ni1Ga / SiO2 is the highest, so the preferred molar ratio of Ni and Ga is 2:1. From Figure 3 it can be seen that although the increase of the total loading of Ni + Ga has no significant effect on the CO2 catalytic performance, it generally shows a volcano-shaped trend, and the performance is optimal when Ni + Ga = 40 wt%, so the preferred total loading of Ni and Ga is 40 wt%. The influence of the reduction temperature also shows a volcano-shaped trend ( Figure 4 ), and the performance of reduction at 450 °C is the best, so the preferred reduction temperature is 450 °C.

[0022] 3. The supported nickel-gallium catalyst provided by the present invention has high catalytic activity for the reverse water-gas shift reaction in the low-temperature range (<500 °C), especially significantly improving the CO2 conversion rate and CO selectivity. The preferred catalyst among them has a CO2 conversion rate of 36.5% and a CO selectivity ≥ 95.2% under the conditions of 400 °C and 1 atm (mass space velocity 36000 mL·h -1 ·g cat -1 ).

[0023] 4. The metal components of the supported nickel-gallium catalyst in the present invention are only nickel and gallium, without precious metal components, and have high economic value and market prospects, and are suitable for industrial applications.

[0024] 5. The support of the supported nickel-gallium catalyst in the present invention can be a commercial SiO2 support without the need for separate preparation, which reduces the difficulty and cost of catalyst preparation and improves the reproducibility of preparation. In addition, SiO2 can also be synthesized independently by a method to endow it with a specific morphology and structure, thereby further regulating the catalyst performance and having strong adjustability.

[0025] 6. The supported nickel-gallium catalyst provided by the present invention greatly changes the product distribution of the nickel-based catalyst for the CO2 hydrogenation reaction. At low temperature (400 °C), it maintains a high CO2 conversion rate (36.5%) and a high CO selectivity (≥95.2%), reducing the costs of separating by-product CH4 and maintaining high temperature, which is beneficial to reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the in-situ XRD spectrum of the 2Ni1Ga / SiO2 catalyst (Ni + Ga = 40 wt%, the catalyst reduction temperature is 450 °C, Ni PDF#04-0850, NiO PDF#47-1049, Ga2O3 PDF#06-0503, the signal is collected under the reaction conditions of 400 °C);

[0027] Figure 2 is the catalytic performance diagram of the NiGa / SiO2 catalyst with different Ni / Ga ratios for the CO2 hydrogenation reaction (Ni + Ga = 40 wt%, the catalyst reduction temperature is 450 °C, P = 1 atm, the raw material gas is a mixture of N2, CO2, and H2 with a molar ratio of 5:2:8, and the space velocity is 36000 mL·h -1 ·g cat -1 )

[0028] Figure 3 is the catalytic performance diagram of the 2Ni1Ga / SiO2 catalyst with different Ni + Ga loadings for the CO2 hydrogenation reaction (the catalyst reduction temperature is 450 °C, P = 1 atm, the raw material gas is a mixture of N2, CO2, and H2 with a molar ratio of 5:2:8, and the space velocity is 36000 mL·h -1 ·g cat -1 )

[0029] Figure 4 is the catalytic performance diagram of the 2Ni1Ga / SiO2 catalyst with different reduction temperatures for the CO2 hydrogenation reaction (Ni + Ga = 40 wt%, P = 1 atm, the raw material gas is a mixture of N2, CO2, and H2 with a molar ratio of 5:2:8, and the space velocity is 36000 mL·h -1 ·g cat-1 )

[0030] Figure 5 Figure for the stability test of the 2Ni1Ga / SiO2 catalyst for the CO2 hydrogenation reaction (Ni + Ga = 40 wt%, catalyst reduction temperature is 450 °C, P = 1 atm, stability test temperature is 400 °C, the raw material gas is a mixture of N2, CO2, and H2 with a molar ratio of 5:2:8, and the space velocity is 36000 mL·h -1 ·g cat -1 ) Detailed implementation manners

[0031] The present invention will be described below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto. For the experimental methods without specific conditions noted in the embodiments, they are generally carried out according to conventional conditions and the conditions described in the manuals, or according to the conditions recommended by the manufacturers. For the general equipment, materials, reagents, etc., unless otherwise specified, they can be obtained from commercial channels. The raw materials required in the following examples and comparative examples are all commercially available.

[0032] Examples 1-4 are the preparation methods of NiGa / SiO2 catalysts with different Ni / Ga ratios:

[0033] Example 1

[0034] Prepare 4Ni1Ga / SiO2 catalyst. Add 3.0 g of SiO2 support into a mixed liquid of 150 mL of deionized water and 100 mL of ethanol, stir evenly and then perform ultrasonic treatment for 10 min, and then continue to stir to obtain solution A. Weigh 7.72 g of Ni(NO3)2·6H2O and 2.65 g of Ga(NO3)2·8H2O according to the molar ratio of Ni to Ga of 4:1, where the total mass of Ni element and Ga element is 40 wt% of the catalyst. Add it to the liquid containing SiO2 under stirring conditions, and then continue to stir in a 30 °C water bath for 1 h to obtain a mixed solution B. Weigh 4 times the amount of Na2CO3 (15.47 g) required to precipitate all the precursors, dissolve it in 100 mL of deionized water and stir evenly. Then use a peristaltic pump to add the Na2CO3 solution to the mixed solution B containing SiO2 at a rate of 5 mL·min -1 and stir and react in a 30 °C water bath for 12 h. Separate by suction filtration and wash with water until the filtrate is neutral. Dry the filter cake at 80 °C for 12 h. In an H2 (20 mL·min -1 ) atmosphere, at a rate of 5 °C·min -1It was heated to 500 °C at a rate of [heating rate] and heat-treated at high temperature for 240 min to obtain a 4Ni1Ga / SiO2 sample. The sample was tableted, and 0.1 g of the 40-60 mesh sample was filled into a fixed-bed reactor. In the raw material gas (20 mL·min -1 ) atmosphere composed of N2, CO2, and H2 with a molar ratio of 5:2:8, it was heated to 450 °C at a rate of 5 °C·min -1 and in-situ reduced for 120 min, and then the reaction performance test could be carried out.

[0035] Example 2

[0036] Prepare a 3Ni1Ga / SiO2 catalyst. The preparation process was the same as that of Example 1, only the dosages of some drugs were different, that is, the dosage of Ni(NO3)2·6H2O was 7.17 g, the dosage of Ga(NO3)2·8H2O was 3.29 g, and the dosage of Na2CO3 was 15.68 g, thus obtaining a 3Ni1Ga / SiO2 sample.

[0037] Example 3

[0038] Prepare a 2Ni1Ga / SiO2 catalyst. The preparation process was the same as that of Example 1, only the dosages of some drugs were different, that is, the dosage of Ni(NO3)2·6H2O was 6.28 g, the dosage of Ga(NO3)2·8H2O was 4.32 g, and the dosage of Na2CO3 was 16.02 g, thus obtaining a 2Ni1Ga / SiO2 sample.

[0039] Example 4

[0040] Prepare a 1Ni1Ga / SiO2 catalyst. The preparation process was the same as that of Example 1, only the dosages of some drugs were different, that is, the dosage of Ni(NO3)2·6H2O was 4.57 g, the dosage of Ga(NO3)2·8H2O was 6.29 g, and the dosage of Na2CO3 was 16.67 g, thus obtaining a 1Ni1Ga / SiO2 sample.

[0041] Examples 5-9 are the preparation methods of 2Ni1Ga / SiO2 catalysts with different total loadings of Ni and Ga:

[0042] Example 5

[0043] Note: The heating rate placeholder in the translation of needs to be filled with the actual heating rate value in the original text.Prepare a 2Ni1Ga / SiO2 catalyst with Ni + Ga = 10 wt%. Add 3.0 g of SiO2 support into a mixed liquid of 150 mL of deionized water and 100 mL of ethanol. After stirring evenly, perform ultrasonic treatment for 10 min, and then continue stirring. According to Ni + Ga = 10 wt%, weigh 1.05 g of Ni(NO3)2·6H2O and 0.72 g of Ga(NO3)2·8H2O, and add them into the liquid containing SiO2 under stirring conditions. Then continue stirring for 1 h under a water bath condition of 30 °C. Weigh 4 times the amount of Na2CO3 (2.67 g) required to precipitate all the precursors, dissolve it in 100 mL of deionized water and stir evenly. Then use a peristaltic pump to add the Na2CO3 solution into the liquid containing SiO2 at a speed of 5 mL·min -1 and stir and react in a water bath at 30 °C for 12 h. Separate by suction filtration and wash with water until the filtrate is neutral. Dry the filter cake at 80 °C for 12 h. In an atmosphere of H2 (20 mL·min -1 ), heat up to 500 °C at a speed of 5 °C·min -1 and perform high-temperature treatment for 240 min to obtain a 2Ni1Ga / SiO2 sample. Press the sample into tablets, select 0.1 g of the 40 - 60 mesh sample and fill it into a fixed-bed reactor. In an atmosphere of a raw material gas (20 mL·min -1 ) composed of N2, CO2, and H2 with a molar ratio of 5:2:8, heat up to 450 °C at a speed of 5 °C·min -1 and perform in-situ reduction treatment for 120 min, and then the reaction performance can be tested.

[0044] Example 6

[0045] Prepare a 2Ni1Ga / SiO2 catalyst with Ni + Ga = 20 wt%. The preparation process is the same as that in Example 5, only the dosages of some drugs are different, that is, the dosage of Ni(NO3)2·6H2O is 2.35 g, the dosage of Ga(NO3)2·8H2O is 1.62 g, and the dosage of Na2CO3 is 6.01 g, so as to obtain a 2Ni1Ga / SiO2 sample.

[0046] Example 7

[0047] Prepare a 2Ni1Ga / SiO2 catalyst with Ni + Ga = 30 wt%. The preparation process is the same as that in Example 5, only the dosages of some drugs are different, that is, the dosage of Ni(NO3)2·6H2O is 4.04 g, the dosage of Ga(NO3)2·8H2O is 2.78 g, and the dosage of Na2CO3 is 10.30 g, so as to obtain a 2Ni1Ga / SiO2 sample.

[0048] Example 8

[0049] Prepare a 2Ni1Ga / SiO2 catalyst with Ni + Ga = 50 wt%. The preparation process is the same as that of Example 5, only the dosages of some chemicals are different. Specifically, the dosage of Ni(NO3)2·6H2O is 9.42 g, the dosage of Ga(NO3)2·8H2O is 6.48 g, and the dosage of Na2CO3 is 24.03 g, thus obtaining a 2Ni1Ga / SiO2 sample.

[0050] Example 9

[0051] Prepare a 2Ni1Ga / SiO2 catalyst with Ni + Ga = 60 wt%. The preparation process is the same as that of Example 5, only the dosages of some chemicals are different. Specifically, the dosage of Ni(NO3)2·6H2O is 14.13 g, the dosage of Ga(NO3)2·8H2O is 9.72 g, and the dosage of Na2CO3 is 36.05 g, thus obtaining a 2Ni1Ga / SiO2 sample.

[0052] Examples 10 - 11 are preparation methods of 2Ni1Ga / SiO2 catalysts with different reduction temperatures:

[0053] Example 10

[0054] Prepare a 2Ni1Ga / SiO2 catalyst reduced at 400 °C. Add 3.0 g of SiO2 support to a mixed liquid of 150 mL of deionized water and 100 mL of ethanol, stir evenly, ultrasonically treat for 10 min, and then continue stirring. According to Ni + Ga = 40 wt%, weigh 6.28 g of Ni(NO3)2·6H2O and 4.32 g of Ga(NO3)2·8H2O, add them to the liquid containing SiO2 under stirring conditions, and then continue stirring for 1 h under a 30 °C water bath condition. Weigh 4 times the amount of Na2CO3 (16.02 g) required to precipitate all precursors, dissolve it in 100 mL of deionized water and stir evenly. Then use a peristaltic pump to add the Na2CO3 solution to the liquid containing SiO2 at a speed of 5 mL·min -1 and stir and react in a 30 °C water bath for 12 h. Separate by suction filtration, wash with water until the filtrate is neutral, dry the filter cake at 80 °C for 12 h. In an H2 (20 mL·min -1 ) atmosphere, heat up to 500 °C at a speed of 5 °C·min -1 and perform high-temperature treatment for 240 min to obtain a 2Ni1Ga / SiO2 sample. Press the sample into tablets, select 0.1 g of 40 - 60 mesh sample and fill it into a fixed-bed reactor. In an H2 (20 mL·min -1 ) atmosphere, heat up to 400 °C at a speed of 5 °C·min -1 and perform in-situ reduction treatment for 120 min, and then the reaction performance can be tested.

[0055] Example 11

[0056] Prepare the 2Ni1Ga / SiO2 catalyst reduced at 500 °C. The preparation process is the same as that of Example 10, except for the reduction temperature. In this example, the reduction treatment is carried out at 500 °C, so as to obtain the 2Ni1Ga / SiO2 catalyst reduced at 500 °C.

[0057] Comparative Example 1

[0058] Prepare the Ni / SiO2 catalyst without Ga element. Add 3.0 g of SiO2 support into the mixed liquid of 150 mL of deionized water and 100 mL of ethanol, stir evenly and then perform ultrasonic treatment for 10 min, and then continue to stir. Weigh 10.00 g of Ni(NO3)2·6H2O, where Ni accounts for 40 wt% of the total mass of Ni / SiO2, add it to the liquid containing SiO2 under stirring conditions, and then continue to stir for 1 h under the condition of 30 °C water bath. Weigh 4 times the amount of Na2CO3 (14.59 g) required to precipitate all the precursors, dissolve it in 100 mL of deionized water and stir evenly. Then use a peristaltic pump to add the Na2CO3 solution to the liquid containing SiO2 at a speed of 5 mL·min -1 and stir and react for 12 h in a 30 °C water bath. Separate by suction filtration and wash with water until the filtrate is neutral, and dry the filter cake at 80 °C for 12 h. In the atmosphere of H2 (20 mL·min -1 ), heat up to 500 °C at a speed of 5 °C·min -1 and perform high-temperature treatment for 240 min to obtain the Ni / SiO2 sample. Press the sample into tablets, select 0.1 g of the 40-60 mesh sample and fill it into a fixed-bed reactor. In the raw material gas (20 mL·min -1 ) composed of N2, CO2, and H2 with a molar ratio of 5:2:8, heat up to 450 °C at a speed of 5 °C·min -1 and perform in-situ reduction treatment for 120 min, and then the reaction performance can be tested.

[0059] The in-situ XRD pattern of the 2Ni1Ga / SiO2 catalyst prepared in Example 3 is as Figure 1 shown, and this pattern is collected under the reaction condition of 400 °C. No characteristic diffraction peak of Ga2O3 is found in the figure, indicating that Ga2O3 exists in an amorphous form or is highly dispersed so that it is below the detection limit. The Ni characteristic diffraction peaks at 44.5° and 51.9° in the standard card (Ni PDF#04-0850) have obvious shifts to small angles (shifted to 43.9° and 51.3° respectively), indicating the expansion of the Ni lattice spacing and the formation of the Ni-Ga alloy phase. Figure 1The peak intensity ratio (2.75) at 43.9° and 51.3° is much greater than the peak intensity ratio (2.38) in the Ni standard card. Therefore, there must be a signal of a certain species hidden in the peak at 43.9°. Referring to the ICDD / JCPDS standard card, the strongest characteristic peak of Ni5Ga3 (PDF#43-1376) falls at 43.3°. That is, the mixed peak here contains the diffraction peak signal of the Ni5Ga3 species, further confirming the formation of the Ni-Ga alloy and the lattice expansion caused by the alloy (the small-angle shift of the characteristic peak). In addition, the size of the Ni nanoparticles obtained by the Scherrer formula is 3.8 nm, proving that the active components exist in a highly dispersed form of small particles.

[0060] The catalysts obtained in Examples 1-11 and Comparative Example 1 were used for the CO2 hydrogenation reaction, and their catalytic activities were compared. The test method for catalytic performance is as follows:

[0061] S1 Load the catalyst. Press and screen the catalyst, take 0.1 g of the 40-60 mesh catalyst, and load it into a fixed-bed reactor.

[0062] S2 Reduce and activate the catalyst. The reducing gas is H2, and the flow rate is 20 mL·min -1 , and heat it to the target temperature at a heating rate of 5 °C·min -1 . The reduction time is 120 min.

[0063] S3 Catalyst performance test. The reaction raw material is a mixed gas of N2, CO2, and H2 with a molar ratio of 5:2:8, and the total flow rate of the mixed gas is 60 mL·min -1 , and the reaction space velocity is 36000 mL·h -1 ·g cat -1 . The reaction temperature is 400 °C, the pressure is 1 atm, and the duration is 250 h.

[0064] The gas composition at the reaction outlet is detected and analyzed in real time by a gas chromatograph (Fuli Instrument GC 9790Plus). The chromatograph is equipped with three chromatographic column channels, namely a Porapak-N packed column (1.5 m × 3.2 mm), a molecular sieve 13X packed column (3.0 m × 3.2 mm), and a Wondercap WAX capillary chromatographic column (25 m × 0.32 mm). The column oven temperature is 70 °C, and the carrier gas Ar flow rate is 100 mL·min -1 , and the reference gas Ar flow rate is 20 mL·min -1 . Two detectors are configured, a gas chromatograph hydrogen flame ionization detector (FID) and a thermal conductivity detector (TCD). Using N2 as the internal standard, the separation and quantitative analysis of H2, N2, CO, CH4, and CO2 are achieved.

[0065] CO2 conversion rate Selectivity (S j ) and CO2 reaction rate are calculated by the following formula:

[0066]

[0067] wherein, in and out in the subscript represent the inlet gas and the outlet gas of the reactor respectively; j refers to CH4 or CO; F is the gas flow rate, such as represents the inlet gas flow rate of CO2; n Ni represents the number of moles of Ni. All reaction evaluation processes and data results can be repeated, and the carbon balance error is maintained within 5%.

[0068] The test results are shown in Figures 2 - 5 .

[0069] By comparing the CO2 hydrogenation performance of the catalysts in Comparative Examples 1-4 and Comparative Example 1, a performance comparison chart of NiGa / SiO2 catalysts with different Ni / Ga ratios is obtained, as shown in Figure 2 . When there is no Ga doping, almost only CH4 is produced in the Ni / SiO2 system, but Ga doping greatly improves the CO selectivity of the NiGa / SiO2 series catalysts, and the selectivity gradually increases with the decrease of the molar ratio of Ni and Ga. Among them, 2Ni1Ga / SiO2 has the highest CO yield, so the preferred molar ratio of Ni and Ga is 2:1.

[0070] By comparing the CO2 hydrogenation performance of the catalysts in Comparative Example 3 and Examples 5-9, a performance comparison chart of 2Ni1Ga / SiO2 catalysts with different Ni+Ga loadings is obtained, as shown in Figure 3 . The increase of the total Ni+Ga loading shows a volcano-shaped trend on the CO2 catalytic performance, and the performance is optimal when Ni+Ga = 40wt%, so the preferred total Ni and Ga loading is 40wt%.

[0071] By comparing the CO2 hydrogenation performance of the catalysts in Comparative Example 3 and Examples 10-11, a performance comparison chart of 2Ni1Ga / SiO2 catalysts with different reduction temperatures is obtained, as shown in Figure 4 . The influence of the reduction temperature shows a volcano-shaped trend, and the performance is the best when reduced at 450°C, so the preferred reduction temperature is 450°C.

[0072] The stability test of the 2Ni1Ga / SiO2 catalyst prepared in Example 3 is shown in Figure 5As shown. During the reaction time of 250 h, the catalytic activity of this catalyst remained at a high level. The conversion rate of CO2 was always maintained above 35% without an obvious decrease, and the selectivity of CO was always maintained at about 95% with a slightly increasing trend, indicating its strong stability.

[0073] In summary, the catalyst with the highest CO yield is 2Ni1Ga / SiO2 (loading amount: Ni + Ga = 40 wt%, reduction temperature: 450 °C). The CO2 conversion rate of this catalyst is 36.5% at 400 °C (space velocity: 36000 mL·h -1 ·g cat -1 ), and the CO selectivity is as high as 95.2%. For the catalyst Ni / SiO2 without Ga doping, the CO selectivity is only 2.7%. At the same time, this catalyst maintained high performance during the 250-h stability test with almost no performance degradation, showing extremely strong stability.

[0074] In the present invention, the raw materials and equipment used, unless otherwise specified, are common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0075] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. Application of a supported nickel-gallium catalyst in reverse water-gas shift reaction, characterized in that: The supported nickel-gallium catalyst is applied to a fixed bed reactor, the supported nickel-gallium catalyst is first reduced, and then a reverse water-gas shift reaction is performed; the conditions of the reverse water-gas shift reaction include: the raw gas is a mixture of N2, CO2, and H2 in a molar ratio of (5:2:2) to (5:2:8), and the reaction space velocity is 36000 to 360000 mL·h -1 ·g cat -1 , the reduction temperature is 300-450°C, and the reaction pressure is 1atm; the supported nickel-gallium catalyst includes a metal active component and a carrier, the metal active component is Ni and Ga in a molar ratio of 1-4:1, the carrier is SiO2, and based on the total mass of the catalyst, the mass content of the two elements Ni and Ga is 10-60wt%.

2. The use according to claim 1, characterized in that: The method for preparing the supported nickel-gallium catalyst comprises the following steps: S1: fully mixing water containing a carrier and ethanol to obtain a mixed solution A; S2: adding nickel and gallium precursors to the mixed solution A and mixing them thoroughly to obtain a mixed solution B; S3: introducing the liquid C containing the precipitant into the mixed liquid B and mixing them thoroughly to obtain a mixture; S4: separating the mixture, drying the obtained precipitate, and subjecting the precipitate to high temperature treatment to obtain a supported nickel-gallium catalyst for reverse water-gas shift reaction.

3. The use according to claim 2, characterized in that: The carrier in step S1 is SiO2.

4. The use according to claim 2, characterized in that: The precursor of nickel and gallium in step S2 is one of their nitrates or chlorides.

5. The use according to claim 2, characterized in that: The precipitant in step S3 is one of sodium carbonate, ammonium carbonate, sodium hydroxide or urea.

6. The use according to claim 2, characterized in that: The mixing temperature in step S3 is 20 to 30° C., and the mixing time is 6 to 24 hours.

7. The use according to claim 2, characterized in that: The separation method in step S4 is suction filtration or centrifugation.

8. The use according to claim 2, characterized in that: The drying temperature in step S4 is 60-120° C., and the drying time is 10-15 hours.

9. The use according to claim 2, characterized in that: The gas atmosphere for the high temperature treatment in step S4 is H2, the treatment temperature is 400-800°C, and the treatment time is 2-6h.

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