Preparation method of non-noble metal catalyst and application thereof in reverse water gas shift reaction

Abstract

The application relates to the technical field of catalysts and discloses a preparation method of a non-noble metal catalyst and application of the non-noble metal catalyst in reverse water gas shift reaction, which comprises the following steps: S1, preparation of SiO2-Me; S2, preparation of ZSM-5-OH molecular sieve by reacting SiO2-Me, an aluminum source and a template agent; S3, impregnation treatment of the ZSM-5-OH molecular sieve in a metal salt solution containing Ni and M to obtain a NiM / ZSM-5-OH molecular sieve; and S4, reduction of the NiM / ZSM-5-OH molecular sieve after calcination to serve as a crystal seed; the aluminum source, the template agent and SiO2-Me are added into water to form a silica-alumina gel, the crystal seed is added to react, and then the H type hydroxyl-rich NiM@ZSM-5-OH molecular sieve is obtained after ammonia exchange and calcination. The second metal additive is introduced and the micro-environment of the molecular sieve channel is adjusted, so that the hydrogen overflow effect is strengthened, and the CO selectivity and the catalytic reaction activity are improved.

Description

Technical Field

[0001] This invention relates to the technical field of catalysts, and in particular to a method for preparing non-precious metal catalysts and their application in countercurrent gasification. Background Technology

[0002] The reverse water gas shift (RWGS, CO2 + H2 → CO + H2O) reaction can convert inert CO2 into highly reactive CO. It is a key step in the hydrogenation of carbon dioxide to produce methanol, low-carbon olefins, aromatics, and gasoline, as well as other high-value-added chemicals and fuels. It can be used to formulate syngas feedstocks with different CO / H2 ratios to meet the production needs of various products, which is of great significance for realizing the resource utilization of CO2.

[0003] The RWGS reaction is a typical endothermic process (ΔH). 298K = 42.1 kJ / mol), high temperatures favor the reaction. Currently, research on this reaction mainly focuses on noble metal catalysts (such as Rh and Pt), whose excellent H2 dissociation ability, unique d-orbital electronic properties, and moderate adsorption strength for reaction intermediates demonstrate superior activity and selectivity. However, the scarcity and high price of noble metal resources limit their economic feasibility for large-scale industrial applications.

[0004] Non-precious metal catalysts, represented by Ni, are widely studied due to their low cost and high conversion rate. However, the strong CO bond dissociation ability and high hydrogenation activity of metallic Ni are more favorable for CO2 or CO methanation reactions, resulting in low CO selectivity in the products. For example, Wang et al. found that Ni / CeO2 catalysts prepared by different methods all exhibited high CO2 conversion rates, but severe methanation and low CO selectivity (Influence of preparation method on performance of Ni-CeO2 catalysts for reverse water-gas shift reaction. Journal of Rare Earths 2013, 31, 559). Patent CN112604699A discloses a Ni2P / CeO2 catalyst and its preparation method for improving the selectivity of reverse water-gas shift reaction, specifically disclosing a CeO2-supported Ni-based catalyst. This catalyst achieves a CO selectivity of 80% only above 500℃. Therefore, how to improve the CO selectivity of Ni-based catalysts has always been an important research topic in the field, and designing and preparing Ni catalysts with both high activity and high selectivity under the reaction conditions remains very difficult. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a non-precious metal catalyst and its application in the reverse water gas reaction. A hydroxyl-rich NiM@ZSM-5-OH molecular sieve (M being a second metal promoter) is prepared by modifying organic groups. By modulating the microenvironment of the molecular sieve pores, the hydrogen overflow effect is enhanced, thereby improving the catalyst's reaction activity at lower temperatures (≤500℃) while achieving high CO selectivity.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a non-noble metal catalyst, comprising the following steps: S1: Preparation of methyl-modified SiO2 to obtain SiO2-Me; S2: After mixing SiO2-Me, aluminum source and template agent, ZSM-5-OH molecular sieve is obtained by crystallization reaction and aerobic calcination. S3: Impregnate ZSM-5-OH molecular sieve in a metal salt solution containing Ni and M to obtain NiM / ZSM-5-OH molecular sieve, wherein M is at least one of Cu, Fe, and Ga; S4: NiM / ZSM-5-OH molecular sieve was calcined and reduced to obtain seed crystals; aluminum source, template agent and SiO2-Me were added to water to form a silica-alumina gel, seed crystals were added, and then crystallization reaction and aerobic calcination were carried out to obtain Na-type hydroxyl-rich NiM@ZSM-5-OH molecular sieve; after ammonia exchange and aerobic calcination, H-type hydroxyl-rich NiM@ZSM-5-OH molecular sieve was obtained.

[0007] In this invention, the catalyst is a zeolite-encapsulated, hydroxyl-rich ZSM-5-OH molecular sieve loaded with non-precious metals Ni and M. By leveraging the synergistic effect between the Ni and M bimetallic species, the catalyst's ability to bind with CO is weakened, inhibiting continuous hydrogenation and thus reducing the methanation side reaction, effectively improving CO selectivity. Ni, as the main metal active site, activates hydrogen and CO2, while the M promoter mainly regulates the electronic valence state of Ni to promote CO desorption. However, using only non-precious metals Ni and M as the catalyst for the reverse water-gas reaction not only inhibits the side reaction of deep hydrogenation of CO to methane but also suppresses the main reaction activity of hydrogenation of CO2 to CO. Therefore, by modifying the molecular sieve microenvironment, the hydroxyl content in the molecular sieve framework is increased, enhancing the hydrogen spillover effect and thereby improving the reactivity of active H species. This compensates for the decrease in CO2 hydrogenation activity caused by the metal promoter and improves the reaction activity at lower temperatures (≤500℃). Furthermore, the pore confinement effect of the zeolite encapsulation structure effectively inhibits the migration and agglomeration of metal nanoparticles, exhibiting excellent stability in high-temperature reactions.

[0008] Therefore, the catalyst in this invention not only has high CO selectivity, but also high CO2 reactivity under mild conditions.

[0009] Preferably, in step S1, the preparation of methyl-modified SiO2 includes the following steps: adding ethanol, ammonia, silicon source and methyldiethoxysilane to water to carry out alkylation reaction, and distilling off the solvent to obtain SiO2-Me.

[0010] Preferably, the mass ratio of the silicon source to methyldiethoxysilane is 1:0.06~0.18; the mass ratio of the silicon source, ammonia, ethanol and water is 1:0.25~0.5:6.6~11:11.2~13.8; the silicon source is tetraethyl silicate (TEOS); and the mass concentration of the ammonia is 25~30wt%.

[0011] Preferably, the alkylation reaction is carried out by stirring at room temperature for 10-15 hours.

[0012] Preferably, in step S2, the molar ratio of SiO2-Me to the aluminum source is 1:0.02~0.05; the molar ratio of SiO2-Me to the template agent is 1:0.1~0.3; the aluminum source is aluminum isopropoxide; and the template agent is tetrapropylammonium hydroxide.

[0013] Preferably, in step S2, the temperature of the crystallization reaction is 160~200℃ and the time is 48~72h; the temperature of the aerobic calcination is 500~600℃ and the holding time is 3~6h.

[0014] Preferably, in step S3, M is Cu, Fe, or Ga; and the molar ratio of Ni to M in the Ni- and M-containing metal salt solution is 1:0.1~0.5.

[0015] Ni and M can exhibit excellent catalytic effects within a limited ratio range, but when the M content is too high, it will cover the active sites of Ni metal and inhibit its activity.

[0016] Preferably, in step S3, the metal salt is a metal nitrate; and the impregnation treatment is an equal-volume impregnation.

[0017] Preferably, in step S3, the Ni loading in the NiM / ZSM-5-OH molecular sieve is 0.35~0.6% and the M loading is 0.03~0.35%.

[0018] Preferably, in step S4, the calcination reduction is performed by calcining in air at 400-500°C for 1-3 hours, followed by reduction in H2 atmosphere at 600-700°C for 1-3 hours.

[0019] Preferably, in step S4, the molar ratio of SiO2-Me to the aluminum source is 1:0.02~0.05; the molar ratio of SiO2-Me, template agent, and water is 1:0.1~0.3:30~50; the mass ratio of SiO2-Me to seed crystal is 1:0.3~0.5; the aluminum source is sodium aluminate; and the template agent is tetrapropylammonium hydroxide.

[0020] Preferably, in step S4, the temperature of the crystallization reaction is 160~200℃ and the time is 48~72h.

[0021] Preferably, in step S4, the temperature of the aerobic roasting is 500~600℃, and the temperature is maintained for 3~6 hours.

[0022] Preferably, in step S4, the ammonia exchange is performed using an ammonium salt solution for ion exchange; the ammonium salt solution is an ammonium chloride solution; the ion exchange is performed by heating to 80~90℃, stirring for 1~2 hours, and repeating the ion exchange three or more times.

[0023] Secondly, the present invention also provides an application of a non-precious metal catalyst in the reverse water gas reaction.

[0024] Preferably, the application includes: contacting the feed gas with a non-precious metal catalyst to carry out a counter-current water gas reaction, wherein the feed gas is a mixture of CO2 and H2 with a molar ratio of 1:1~3, the reaction temperature is 350~500℃, and the pressure is 0.1~2MPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses NiM@ZSM-5 molecular sieve rich in hydroxyl groups to promote the hydrogen overflow effect of molecular sieve channel microenvironment to improve reaction activity, and uses metal auxiliary agent M to regulate CO desorption to improve CO selectivity, forming a reverse water gas catalyst with both high activity and high stability. (2) Under the same reverse water gas reaction conditions, the catalyst in this invention can have higher catalytic stability and longer catalytic reaction life, reducing the consumption of catalyst regeneration. Attached Figure Description

[0026] Figure 1 The image shows the XRD pattern of the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve in Example 1.

[0027] Figure 2 This is a SEM image of the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve from Example 2.

[0028] Figure 3 This is a TEM image of the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve from Example 3.

[0029] Figure 4 The CO2 conversion rate-time curves are shown for the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve in Example 1 and the H-type NiCu / ZSM-5 molecular sieve in Comparative Example 2. Detailed Implementation

[0030] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Example 1

[0032] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.25:0.06:6.6:12.1, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.05:0.1. The mixture was then transferred to a hydrothermal reactor and crystallized at 180℃ for 72h. The resulting reaction product was calcined in air at 550℃ for 4h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.1 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing equal volume impregnation treatment to obtain a supported NiCu / ZSM-5-OH (Ni: 0.35wt%, Cu: 0.038wt%) molecular sieve; S4: The NiCu / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.05:0.1:30, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.4. The mixture was transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve (Ni: 0.1wt%, Cu: 0.01wt%).

[0033] Example 2

[0034] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.33:0.12:8.8:13.0, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.02:0.2. The mixture was then transferred to a hydrothermal reactor and crystallized at 200℃ for 48h. The resulting reaction product was calcined in air at 550℃ for 4h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.5 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing an equal volume impregnation treatment to obtain a supported NiCu / ZSM-5-OH (Ni: 0.6wt%, Cu: 0.3wt%) molecular sieve; S4: The NiCu / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.02:0.3:50, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.5. The mixture was transferred to a hydrothermal reactor and crystallized at 200℃ for 48 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve (Ni: 0.2wt%, Cu: 0.1wt%).

[0035] Example 3

[0036] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.5:0.18:11:13.8, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.25:0.3. The mixture was then transferred to a hydrothermal reactor and crystallized at 160℃ for 84h. The resulting reaction product was calcined in air at 550℃ for 4h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.2 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing an equal volume impregnation treatment to obtain a supported NiCu / ZSM-5-OH (Ni: 0.5wt%, Cu: 0.1wt%) molecular sieve; S4: The NiCu / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.04:0.2:40, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.3. The mixture was transferred to a hydrothermal reactor and crystallized at 160℃ for 84 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve (Ni: 0.11wt%, Cu: 0.02wt%).

[0037] Example 4

[0038] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.25:0.06:6.6:12.1, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.05:0.2. The mixture was then transferred to a hydrothermal reactor and crystallized at 180℃ for 72h. The resulting reaction product was calcined in air at 550℃ for 4h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Fe(NO3)3 in a molar ratio of 1:0.1 to obtain a metal salt solution containing Ni and Fe; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing equal volume impregnation treatment to obtain a supported NiFe / ZSM-5-OH (Ni: 0.6wt%, Fe: 0.06wt%) molecular sieve; S4: The NiFe / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.05:0.2:40, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.3. The mixture was transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiFe / ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiFe / ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiFe / ZSM-5-OH molecular sieve (Ni: 0.14wt%, Fe: 0.013wt%).

[0039] Example 5

[0040] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.25:0.06:6.6:12.1, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.02:0.2. The mixture was then transferred to a hydrothermal reactor and crystallized at 180℃ for 72h. The resulting reaction product was calcined in air at 550℃ for 4h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Ga(NO3)3 at a molar ratio of 1:0.2 to obtain a metal salt solution containing Ni and Ga; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing equal volume impregnation treatment to obtain a supported NiGa / ZSM-5-OH (Ni: 0.6wt%, Ga: 0.14wt%) molecular sieve; S4: NiGa / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel according to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.02:0.2:40. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.5. The mixture was then transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiGa / ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiGa / ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiGa / ZSM-5-OH molecular sieve (Ni: 0.2wt%, Ga: 0.05wt%).

[0041] Comparative Example 1 The difference from Example 1 is that the catalyst is H-type NiCu@ZSM-5 molecular sieve, that is, it has not been modified with hydroxyl groups.

[0042] S1: A silicon source (tetraethyl silicate), an aluminum source (aluminum isopropoxide), and a tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed in a molar ratio of silicon source, aluminum source, and tetrapropylammonium hydroxide of 1:0.05:0.1. The mixture was then transferred to a hydrothermal reactor and crystallized at 180 °C for 72 h. The resulting reaction product was calcined in air at 550 °C for 4 h to obtain ZSM-5 molecular sieve. S2: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.1 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5 molecular sieve in the metal salt solution and perform ultrasonication while performing equal volume impregnation treatment to obtain a supported NiCu / ZSM-5 (Ni: 0.35wt%, Cu: 0.038wt%) molecular sieve; S3: The NiCu / ZSM-5 molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.05:0.1:30, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.4. The mixture was transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type NiCu@ZSM-5 molecular sieve. S4: The Na-type NiCu@ZSM-5 molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type NiCu@ZSM-5 molecular sieve (Ni: 0.1wt%, Cu: 0.01wt%).

[0043] Comparative Example 2 The difference from Example 1 is that the catalyst is NiCu / ZSM-5 molecular sieve, that is, a conventional supported metal-molecular sieve catalyst is used and the ZSM-5 molecular sieve is not modified with hydroxyl groups.

[0044] S1: A silicon source (tetraethyl silicate), an aluminum source (aluminum isopropoxide), and a tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed in a molar ratio of silicon source, aluminum source, and tetrapropylammonium hydroxide of 1:0.05:0.1. The mixture was then transferred to a hydrothermal reactor and crystallized at 180 °C for 72 h. The resulting reaction product was calcined in air at 550 °C for 4 h to obtain ZSM-5 molecular sieve. S2: Ni(NO3)2 and Cu(NO3)2 were prepared into a solution at a molar ratio of 1:0.1 to obtain a metal salt solution containing Ni and Cu; ZSM-5 molecular sieve was immersed in the metal salt solution and subjected to ultrasonic treatment while undergoing equal volume impregnation; after calcination in air at 400℃ for 2 hours and reduction in hydrogen at 600℃ for 2 hours, a supported NiCu / ZSM-5 (Ni: 0.1wt%, Cu: 0.01wt%) molecular sieve was obtained.

[0045] Comparative Example 3 The difference from Example 1 is that the silicon-to-aluminum ratio of the ZSM-5 molecular sieve in the catalyst (H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve) is 200.

[0046] S1: Following the mass ratio of silicon source: ammonia: methyldiethoxysilane: ethanol: water of 1:0.25:0.06:6.6:12.1, silicon source (tetraethyl silicate), ammonia (28-30wt%), methyldiethoxysilane and ethanol were added to water for alkylation reaction. The reaction was stirred at room temperature for 12 h, and then water and ethanol solvent were removed by distillation at 100℃ to obtain methyl-modified SiO2 (SiO2-Me). S2: SiO2-Me, aluminum source (aluminum isopropoxide), and tetrapropylammonium hydroxide aqueous solution (40wt%) were mixed evenly at room temperature according to the molar ratio of SiO2-Me, aluminum source, and tetrapropylammonium hydroxide of 1:0.005:0.1. The mixture was then ground evenly at room temperature and transferred to a hydrothermal reactor for crystallization at 180 °C for 72 h. The resulting reaction product was calcined in air at 550 °C for 4 h to obtain hydroxyl-rich ZSM-5 molecular sieve (ZSM-5-OH molecular sieve). S3: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.1 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing equal volume impregnation treatment to obtain a supported NiCu / ZSM-5-OH (Ni: 0.35wt%, Cu: 0.038wt%) molecular sieve; S4: The NiCu / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water at a molar ratio of 1:0.005:0.1:30 to form a uniform silica-alumina gel. Seed crystals were then added at a mass ratio of 1:0.4 (SiO2-Me:seed crystals). The mixture was then transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve (Ni: 0.1wt%, Cu: 0.01wt%).

[0047] Comparative Example 4 The difference from Example 1 is that the molar ratio of Ni(NO3)2 to Cu(NO3)2 is 1:0.8.

[0048] Steps S1 and S2 are the same as in Example 1.

[0049] S3: Prepare a solution of Ni(NO3)2 and Cu(NO3)2 in a molar ratio of 1:0.8 to obtain a metal salt solution containing Ni and Cu; immerse ZSM-5-OH molecular sieve in the metal salt solution and perform ultrasonication while performing an equal volume impregnation treatment to obtain a supported NiCu / ZSM-5-OH (Ni: 0.35wt%, Cu: 0.3wt%) molecular sieve; S4: The NiCu / ZSM-5-OH molecular sieve was first calcined in air at 400℃ for 2 hours, and then reduced in hydrogen at 600℃ for 2 hours to obtain seed crystals. According to the molar ratio of SiO2:Al:tetrapropylammonium hydroxide:water of 1:0.05:0.1:30, SiO2-Me, aluminum source (NaAlO2), and tetrapropylammonium hydroxide were added to water to form a uniform silica-alumina gel. Then, seed crystals were added according to the mass ratio of SiO2-Me:seed crystals of 1:0.4. The mixture was transferred to a hydrothermal reactor and crystallized at 180℃ for 72 hours. The resulting reaction product was calcined in air at 550℃ for 4 hours to obtain Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve. S5: The Na-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve was subjected to ion exchange with an ammonium salt solution (ammonium chloride solution), heated to 80℃ and stirred for 2h; the ion exchange was repeated three times, and the resulting reaction product was calcined in air at 550℃ for 4h to obtain the H-type hydroxyl-rich NiCu@ZSM-5-OH molecular sieve (Ni: 0.1wt%, Cu: 0.087wt%).

[0050] The catalysts in Examples 1-5 and Comparative Examples 1-4 were subjected to countercurrent water-gas reactions in a fixed bed. The feed gas was a mixture of CO2 and H2. The molar ratio of the mixture, reaction temperature, and pressure were set as shown in Table 1. The equilibrium CO2 conversion rates in the countercurrent water-gas reactions were 29.4% (350℃), 35.7% (400℃), 42.2% (450℃), and 48.4% (500℃).

[0051] Table 1. Catalytic performance of the catalysts in Examples 1-5 and Comparative Examples 1-4 in the countercurrent water gas reaction.

[0052] like Figure 1 The image shows the XRD pattern of the NiCu@ZSM-5-OH molecular sieve in Example 1. No Ni and Cu-related metal diffraction peaks were observed, indicating that the metal particles are well dispersed in the molecular sieve. Figure 2 As shown in the scanning electron microscope image of the NiCu@ZSM-5-OH molecular sieve in Example 2, the morphology is regular and the crystallinity is good. Figure 3 As shown in the transmission electron microscope (TEM) of the NiCu@ZSM-5-OH molecular sieve slices in Example 3, NiCu nano-metal alloys are clearly visible. Figure 4 As shown, the catalyst in Example 1 showed no significant deactivation after 200 hours of continuous and stable operation, while the supported catalyst in Comparative Example 2 gradually began to deactivate after about 150 hours of operation.

[0053] As shown in Table 1, it can be seen from Comparative Example 1 and Example 1 that the CO2 conversion rate is significantly lower when ordinary ZSM-5 molecular sieve is used as a support compared to hydroxyl-rich ZSM-5-OH molecular sieve. The reason for this is that hydroxyl-rich molecular sieves possess more active hydrogen species H* acceptor sites and a more continuous hydrogen diffusion network, thereby significantly reducing the hydrogen overflow energy barrier, extending the diffusion distance, and increasing the concentration of mobile active hydrogen, thus effectively improving the CO2 hydrogenation conversion activity.

[0054] Furthermore, as can be seen from Comparative Examples 2 and 1, compared to zeolite-encapsulated metal catalysts, supported metal catalysts exhibit significantly more unstable performance, with a rapid decline in CO2 conversion rate. The reasons for this are as follows: supported metal particles, exposed on the outer surface of the support, are prone to migration, agglomeration, and sintering under high temperature and hydrogen-rich atmospheres, leading to a rapid reduction in the number of active metal sites. Simultaneously, the interfacial interaction between the metal and the support is weak, resulting in insufficient hydrogen spillover and difficulty in effectively transferring active hydrogen to CO2 activation sites, causing a continuous decline in CO2 conversion efficiency. In addition, carbon deposits generated during the reaction are more likely to cover the exposed metal surface, further clogging the active centers. The zeolite encapsulation structure, on the other hand, can spatially confine and suppress metal sintering and carbon deposition, thereby maintaining more stable catalytic performance.

[0055] A comparison of Comparative Example 3 and Example 1 shows that when the silica-to-alumina ratio of the molecular sieve is too high, the framework aluminum content is low, and the CO2 conversion rate decreases significantly. Conversely, an increased framework aluminum content leads to more bridging hydroxyl groups (Brønsted acid sites, Al-OH-Si), forming a denser and more continuous hydrogen network. This significantly reduces the active hydrogen migration barrier and enhances metal-support interactions and interfacial hydrogen transfer efficiency, thereby strengthening the hydrogen spillover effect. Therefore, a suitable silica-to-alumina ratio in the molecular sieve is equally important for improving CO2 hydrogenation activity.

[0056] As can be seen from the comparison between Comparative Example 4 and Example 1, when the ratio of metal additive M to Ni is too high, it will cover the active sites of Ni metal and inhibit its activity, thereby reducing the activity of CO2 hydrogenation and the CO2 conversion rate, but the selectivity of CO generation will not be significantly affected.

[0057] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a non-precious metal catalyst, characterized in that, Includes the following steps: S1: A mixture of silicon source, methyldiethoxysilane, ammonia, ethanol and water is prepared, with the mass ratio of silicon source to methyldiethoxysilane being 1:0.06~0.

18. An alkylation reaction is then carried out to obtain SiO2-Me. S2: After mixing SiO2-Me, aluminum source, and template agent, the molar ratio of SiO2-Me to aluminum source is 1:0.02~0.

05. After crystallization reaction and aerobic calcination, ZSM-5-OH molecular sieve is obtained. S3: The ZSM-5-OH molecular sieve is impregnated in a metal salt solution containing Ni and M, wherein the molar ratio of Ni to M in the metal salt solution is 1:0.1~0.5, to obtain NiM / ZSM-5-OH molecular sieve, wherein M is at least one of Cu, Fe and Ga; S4: NiM / ZSM-5-OH molecular sieve was calcined and reduced to serve as seed crystals; aluminum source, template agent and SiO2-Me were added to water to form a silica-alumina gel, seed crystals were added, and then crystallization reaction and aerobic calcination were carried out to obtain Na-type hydroxyl-rich NiM@ZSM-5-OH molecular sieve; after ammonia exchange and aerobic calcination, H-type hydroxyl-rich NiM@ZSM-5-OH molecular sieve was obtained.

2. The method for preparing the non-noble metal catalyst according to claim 1, characterized in that, In step S1, the mass ratio of the silicon source, ammonia, ethanol and water is 1:0.25~0.5:6.6~11:11.2~13.8; the silicon source is tetraethyl silicate.

3. The method for preparing the non-precious metal catalyst according to claim 1, characterized in that, In step S2, the molar ratio of SiO2-Me to the template agent is 1:0.1~0.3; the template agent is tetrapropylammonium hydroxide.

4. The method for preparing the non-noble metal catalyst according to claim 1 or 3, characterized in that, In step S2, the temperature of the crystallization reaction is 160~200℃ and the time is 48~72h; the temperature of the aerobic calcination is 500~600℃ and the holding time is 3~6h.

5. The method for preparing the non-precious metal catalyst according to claim 1, characterized in that, In step S3, the Ni loading in the NiM / ZSM-5-OH molecular sieve is 0.35~0.6%.

6. The method for preparing the non-noble metal catalyst according to claim 1, characterized in that, In step S4, the calcination reduction is performed by calcining in air at 400-500°C for 1-3 hours, followed by reduction in H2 atmosphere at 600-700°C for 1-3 hours.

7. The method for preparing the non-noble metal catalyst according to claim 1 or 6, characterized in that, In step S4, the molar ratio of SiO2-Me to aluminum source is 1:0.02~0.05; the molar ratio of SiO2-Me, template agent and water is 1:0.1~0.3:30~50; and the mass ratio of SiO2-Me to seed crystal is 1:0.3~0.

5.

8. The application of a non-precious metal catalyst prepared by any one of claims 1-7 in a counter-current gas reaction.

9. The application according to claim 8, characterized in that, include: The feed gas is contacted with a non-precious metal catalyst to carry out a counter-current water gas reaction. The feed gas is a mixture of CO2 and H2 with a molar ratio of 1:1~3. The reaction temperature is 350~500℃ and the pressure is 0.1~2MPa.

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