Nickel-based catalyst, preparation method thereof and application of nickel-based catalyst in carbon dioxide conversion

Abstract

The invention discloses a nickel-based catalyst, a preparation method thereof and application of the nickel-based catalyst in carbon dioxide conversion. The catalyst is prepared by taking nickel oxide or a nickel-nickel oxide coexisting state as an active component and performing mild partial reduction activation at 200-450 DEG C. The nickel oxide and the nickel-nickel oxide coexisting phase have excellent low-temperature activity and stability. The catalyst has outstanding performance in reactions such as preparation of methane by hydrogenation of carbon dioxide, especially can realize high conversion rate (61.3-87.1%) and high methane selectivity (gt, 99.8%) at 200-250 DEG C, has good stability, greatly reduces the activation energy consumption of the catalyst, and has important industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology and carbon dioxide resource utilization, specifically relating to a nickel-based catalyst, its preparation method, and its application in carbon dioxide conversion. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Catalytic conversion of carbon dioxide (CO2) is a key pathway to achieving carbon neutrality and the resource utilization of CO2. It mainly includes reactions such as CO2 hydrogenation to methane (methanation), carbon monoxide (reverse water-gas shift), or methanol production. This is because the CO2 molecule is very stable (C=O bond energy is as high as 750 kJ). mol 1 High reaction temperatures are typically required for effective activation and conversion. However, high temperatures not only increase energy consumption but also easily lead to catalyst sintering and deactivation, and are detrimental to thermodynamic equilibrium. For example, for the strongly exothermic CO2 methanation reaction (CO2 + 4H2 → CH4 + 2H2O, ΔH...),... 298 K = -165.1 kJ mol 1 Low temperatures are more conducive to the forward reaction and improve methane selectivity, while high temperatures promote side reactions such as reverse water-gas shift reaction, reducing the selectivity of the target product. Therefore, developing CO2 conversion catalysts with excellent low-temperature activity can effectively promote the practical application of CO2 catalytic conversion technology.

[0004] Currently, catalysts used for CO2 conversion mainly fall into two categories: noble metal catalysts and nickel-based catalysts. Among them, nickel-based catalysts have attracted much attention due to their low cost and good catalytic activity. However, traditional nickel-based catalysts generally suffer from insufficient activity at low temperatures and are prone to sintering and carbon deposition leading to deactivation under high-temperature reaction conditions. In traditional understanding and existing technology, metallic nickel (Ni...) is generally considered... 0 Ni is the only active site in the CO2 hydrogenation reaction. Therefore, almost all nickel-based catalysts must undergo high-temperature pre-reduction treatment (usually above 500 °C) before being put into use to completely reduce the nickel oxide (NiO) in the catalyst precursor to Ni. 0 This high-temperature reduction step not only increases the complexity of the process and energy consumption, but also results in the formation of fine metallic Ni particles after complete reduction. 0 The particles are prone to agglomeration and sintering due to high temperatures in subsequent reactions, or the active sites are covered by carbon deposits, resulting in rapid deactivation of the catalyst.

[0005] Therefore, there is an urgent need to develop a new type of nickel-based catalyst that can overcome the above limitations, while reducing activation energy consumption and achieving excellent low-temperature activity and long-term stability. Summary of the Invention

[0006] To address the problems of insufficient low-temperature activity and easy sintering and carbon deposition leading to deactivation of traditional nickel-based catalysts under high-temperature reaction conditions, this invention provides a nickel-based catalyst, its preparation method, and its application in carbon dioxide conversion.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A nickel-based catalyst, the catalyst comprising an active component and an auxiliary component comprising nickel oxide and metallic nickel in a coexisting state; the auxiliary component being one or more of the metal oxides Ce, Zr, Y, La, Pr, Nd, Fe, Co, Mn, Cu, Al, and Mg. A method for preparing the above-mentioned nickel-based catalyst comprises the following steps: A metal salt precursor containing nickel and auxiliary elements is dissolved in deionized water to obtain a metal salt solution. Simultaneously, an organic complexing agent is dissolved in deionized water and poured into the metal salt solution while stirring. The resulting solution is heated and maintained for a certain time while stirring to evaporate water until a gel is formed. The resulting gel is dried in an oven at 60–100 °C for 8–24 h, and then calcined to obtain a nickel-based catalyst precursor. The obtained catalyst precursor is placed in a reaction tube and heated to a target temperature under a reducing atmosphere and maintained for a certain time to obtain the nickel-based catalyst.

[0008] Furthermore, the metal precursor mentioned in the step is any one of nitrate, acetate, and chloride.

[0009] Furthermore, the solvent is one or more of water, methanol, ethanol, butanol, and tetrahydrofuran.

[0010] Furthermore, the drying temperature of the oven is 60~100 ℃, and the drying time is 8~24 h.

[0011] Furthermore, the calcination temperature is 400~800 ℃, and the calcination time is 2~6 h.

[0012] Furthermore, the reducing atmosphere is hydrogen, the reducing temperature is 200~450 ℃, and the reducing time is 0.1~4 h.

[0013] Application of the above-described nickel-based catalyst or the nickel-based catalyst prepared by the above-described preparation method in the catalytic conversion of carbon dioxide.

[0014] The above-mentioned nickel-based catalyst was placed in a continuously flowing gas-solid phase reaction quartz tube, and a reaction gas containing carbon dioxide was introduced at a space velocity of 20,000 h⁻¹. -1 The reaction pressure is at atmospheric pressure, and the reaction temperature is 150~400 °C. The gas composition and concentration changes are detected online by a gas chromatograph equipped with TCD and FID.

[0015] The beneficial effects of the technical solution provided by this invention are: (1) The nickel-based catalyst prepared in this invention has a CO2 conversion rate of 61.3-87.1% at 200-250 °C, a methane selectivity of >99.8%, and exhibits excellent stability during long-term operation of 100 h, while traditional metallic Ni 0 The catalyst has almost no catalytic activity at 200~250°C.

[0016] (2) This invention significantly improves the stability and deactivation resistance of the catalyst, NiO or Ni 0 -The coexistence state of NiO is structurally superior to that of pure metallic Ni. 0 Nanoparticles exhibit greater thermal and chemical stability, and the addition of additives enhances the catalyst's adsorption of CO2, thereby further improving catalytic activity and demonstrating superior anti-sintering and anti-carbon deposition properties. This fundamentally extends the catalyst's lifespan and solves the industry problem of traditional nickel-based catalysts being rapidly deactivated due to sintering and carbon deposition.

[0017] (3) This invention abandons the traditional high-temperature (>500 °C) pre-reduction step and adopts mild partial reduction activation at 200~450 °C, which greatly reduces the energy consumption of pretreatment; combined with its excellent low-temperature activity, it achieves the dual goals of "reducing consumption and increasing efficiency"; in addition, the performance can be further optimized by adding specific additives, which provides a new technical paradigm for designing the next generation of low-temperature, high-efficiency and stable CO2 conversion catalysts. Attached Figure Description

[0018] Figure 1 The results are the CO2 methanation catalytic activity test results for Examples 1-6 and Comparative Examples 4-5; Figure 2 The results are the CO2 methanation catalytic activity test results for Examples 7-9 and Comparative Examples 6-7; Figure 3 The results of the 100-h durability test for Example 7 and Comparative Example 7 are shown. Figure 4 The results are the CO2 methanation catalytic activity test results for Examples 10-13 and Comparative Examples 1-3; Figure 5 The XRD results are for Examples 7-8 and Comparative Examples 6-7; Figure 6The XRD results are for comparative examples 1-2. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0020] Example 1 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%), the main steps of which are: 5.68 g of Ni(NO3)2... 6H2O and 6.75 g Ce(NO3)3 6H₂O was dissolved in 25 mL of deionized water. Simultaneously, 20.50 g of citric acid monohydrate was dissolved in 25 mL of deionized water, and this solution was poured into the metal salt solution while stirring, with stirring continuing for 1 h. The mixture was heated at 80 °C to evaporate the water until a gel was formed. The resulting gel was dried in an oven at 85 °C for 8 h, then heated to 150 °C and dried for 4 h. It was then calcined at 300 °C for 2 h, then further heated to 450 °C and calcined for another 2 h. After cooling to the desired temperature, the cerium-nickel composite catalyst precursor with a Ni content of 10% was obtained.

[0021] The obtained catalyst precursor powder was compressed into tablets (40-60 mesh) and placed in a continuous flow gas-solid phase reaction quartz tube. Before testing the catalytic activity, the catalyst precursor was pretreated in a 200 °C H2 gas stream for 1 h, and then a reaction gas with a carbon dioxide and hydrogen molar ratio of 1:4 was introduced at a space velocity of 20,000 h⁻¹. -1 The reaction pressure was at atmospheric pressure, and the reaction temperature was 250 °C. The gas composition and concentration changes were detected online by a gas chromatograph equipped with TCD and FID.

[0022] Example 2 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 250 °C CH2 gas stream.

[0023] Example 3 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 300 °C CH2 gas stream.

[0024] Example 4 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 350 °C CH2 gas stream.

[0025] Example 5 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 400 °C CH2 gas stream.

[0026] Example 6 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 450 °C CH2 gas stream.

[0027] Example 7 A method for preparing a cerium-nickel catalytic material (70% Ni by mass), except for Ce(NO3)3 The masses of 6H2O and citric acid monohydrate were 1.24 g and 4.19 g, respectively. The pretreatment conditions before the test were the same as in Example 1, except that the pretreatment was carried out in H2 gas at 300 °C for 1 h.

[0028] Example 8 A method for preparing a cerium-nickel composite catalytic material (Ni mass fraction 70%) is the same as in Example 7, except that the pretreatment conditions before testing are 350°C H2 gas flow for 1 h.

[0029] Example 9 A method for preparing a cerium-nickel composite catalytic material (Ni mass fraction 70%) is the same as in Example 7, except that the pretreatment conditions before testing are 1 h of pretreatment in H2 gas at 450°C.

[0030] Example 10 A method for preparing a zirconium-nickel catalytic material (Ni mass fraction 20%), except for ZrO(NO3)2 The mass of 2H2O was 4.89g, and the pretreatment conditions before the test were the same as in Example 1, except that the pretreatment was carried out in H2 gas flow at 450 °C for 1 h.

[0031] Example 11 A method for preparing a zirconium-nickel catalytic material (Ni mass fraction 40%), except for ZrO(NO3)2 The mass of 2H2O was 9.78g, and the rest was the same as in Example 10.

[0032] Example 12 A method for preparing a zirconium-nickel catalytic material (Ni mass fraction 60%), except for ZrO(NO3)2 Except for the mass of 2H2O being 14.66g and the reaction temperature being 200 °C, everything else was the same as in Example 10.

[0033] Example 13 A method for preparing a zirconium-nickel catalytic material (80% Ni by mass), except for ZrO(NO3)2 Except for the mass of 2H2O being 19.55g and the reaction temperature being 200 °C, everything else was the same as in Example 10.

[0034] Comparative Example 1 A method for preparing a pure nickel catalytic material, the main steps of which are: 5.68 g of Ni(NO3)2 6H₂O was dissolved in 25 mL of deionized water. Simultaneously, 4.20 g of citric acid monohydrate was dissolved in 25 mL of deionized water, and this solution was poured into the metal salt solution while stirring for 1 h. The mixture was heated at 80 °C to evaporate the water until a gel formed. The resulting gel was dried in an oven at 85 °C for 8 h, then heated to 150 °C and dried for 4 h. It was then calcined at 300 °C for 2 h, then further heated to 450 °C and calcined for another 2 h. After cooling down, the cerium-nickel composite catalyst precursor with a Ni content of 10% was obtained. Before testing the catalytic activity, the catalyst precursor was pretreated in a H₂ gas stream at 230 °C for 1 h to obtain the catalyst. Then, a reaction gas of hydrogen was introduced at a space velocity of 20,000 h⁻¹. -1 The reaction pressure was at atmospheric pressure, and the reaction temperature was 250 °C. The gas composition and concentration changes were detected online by a gas chromatograph equipped with TCD and FID.

[0035] Comparative Example 2 A method for preparing a pure nickel catalyst material, except that the pretreatment conditions before testing are the same as those in Comparative Example 1, which are pretreatment in H2 gas at 300 °C for 1 h.

[0036] Comparative Example 3 A method for preparing a pure nickel catalyst material, except that the pretreatment conditions before testing are the same as those in Comparative Example 1, which are pretreatment in H2 gas at 400 °C for 1 h.

[0037] Comparative Example 4 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a 600 °C CH2 gas stream.

[0038] Comparative Example 5 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 30%) is the same as in Example 1, except that the pretreatment conditions before testing are 1 h of pretreatment in a CN2 gas stream at 200 °C.

[0039] Comparative Example 6 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 70%) is the same as in Example 7, except that the pretreatment conditions before testing are 1 h of pretreatment in a CN2 gas stream at 200 °C.

[0040] Comparative Example 7 A method for preparing a cerium-nickel catalytic material (Ni mass fraction 70%) is the same as in Example 7, except that the pretreatment conditions before testing are 1 h of pretreatment in a 600 °C CH2 gas stream.

[0041] Comparative Example 8 Table 1 shows the CO2 conversion and CH4 selectivity of each catalyst at 200–250 °C in the CO2 methanation reaction.

[0042] Table 1 CO2 conversion and CH4 selectivity on the catalyst Figure 1 The catalytic activity test results for CO2 methanation in Examples 1-6 and Comparative Examples 4-5 are presented. It can be seen that as the reduction temperature increases, the activity of the catalyst with 30% Ni content first increases and then decreases, indicating that over-reduction yields single Ni. 0 The reduction temperature of 450 °C is unfavorable for catalytic activity, yielding Ni. 0 The catalyst exhibits optimal activity when coexisting with NiO. Furthermore, it was found that the catalyst also possesses significant activity even without reduction, when containing only NiO.

[0043] Figure 2 The catalytic activity test results for CO2 methanation in Examples 7-9 and Comparative Examples 6-7 are presented. It can be seen that, similar to the catalyst with 30% Ni content, the activity of the catalyst with 70% Ni content also first increases and then decreases with increasing reduction temperature. At a reduction temperature of 300 °C, Ni... 0 The catalyst exhibits optimal activity when coexisting with NiO. Similarly, it has been further demonstrated that the catalyst also possesses significant activity when containing only NiO. Furthermore, regardless of whether H2 or CO is used, excessive reduction is detrimental to catalytic activity.

[0044] Figure 3 The durability test results of Example 7 and Comparative Example 7 in a CO2 methanation catalytic reaction atmosphere at 280 °C for 100 h are presented. It can be seen that the catalyst activity of Example 7 did not decrease significantly, exhibiting high stability, while the catalyst activity of Comparative Example 7 decreased significantly during the 100 h test, indicating poor catalyst stability. This result proves that Ni 0 The coexistence state of NiO is better than that of pure Ni 0 The state has higher stability.

[0045] Figure 4 The catalytic activity test results for CO2 methanation in Examples 10-13 and Comparative Examples 1-3 are presented. It can be seen that for pure nickel catalysts, the catalytic activity changes with reduction temperature in the same way, i.e., Ni... 0 The coexistence state with NiO has a higher efficiency than over-reduced Ni. 0 Better catalytic activity. Furthermore, this result demonstrates that the addition of additives in the range of 20% to 80% can significantly improve the catalytic activity of the catalyst.

[0046] Figure 5 The XRD results of Examples 7-8 and Comparative Examples 6-7 are presented, which directly demonstrate that increasing the reduction temperature can improve Ni... 0 The ratio. And the optimal catalytic activity state is indeed Ni. 0 The results are from the NiO coexistence state, obtained by reduction with H2 at 300 ℃ for 1 h. In the untreated sample, Ni exists only as NiO, while in the sample excessively reduced with H2 at 600 ℃, Ni exists only as NiO. 0 The state exists.

[0047] Figure 6 The XRD results of Comparative Examples 1-2 are given, which directly prove that Ni can be obtained by reducing pure nickel catalyst with H2 at 230 °C for 1 h. 0 When nickel coexists with NiO, it is reduced to pure Ni by increasing the reduction temperature. 0 This state reduces catalytic activity and CH4 selectivity.

[0048] The above description of the embodiments is merely to aid in understanding the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A nickel-based catalyst characterized in that, The catalyst comprises a coexisting state component of nickel oxide and metallic nickel and a metal oxide additive.

2. The catalyst according to claim 1, characterized in that, The additive is one or more of Ce, Zr, Y, La, Pr, Nd, Fe, Co, Mn, Cu, Al and Mg metal oxides.

3. The nickel-based catalyst of claim 2, wherein, The mass percentage of nickel element is 20-80% and the mass percentage of the additive metal oxide is 80-20% based on the total mass of nickel element and additive metal oxide in the catalyst.

4. A process for the preparation of a nickel-based catalyst according to any one of claims 1 to 3, characterized in that, The preparation method comprises the following steps: (1) mixing a metal salt precursor containing nickel element and additive element with an organic complexing agent to form a solution; (2) gelating, drying and calcining the solution to obtain a nickel-based catalyst precursor; (3) placing the nickel-based catalyst precursor in a reducing atmosphere for partial reduction activation treatment to form the nickel-based catalyst.

5. The preparation method according to claim 4, characterized in that, The metal salt precursor is nitrate, acetate or chloride; and the organic complexing agent is citric acid, oxalic acid or ethylenediaminetetraacetic acid.

6. The preparation method according to claim 4, characterized in that, The reducing atmosphere is hydrogen.

7. The method of claim 4, wherein, The temperature of the partial reduction activation treatment is 200-450 ℃ and the treatment time is 0.1-4 h.

8. Application of the nickel-based catalyst of any one of claims 1-3 or the nickel-based catalyst prepared by the preparation method of any one of claims 4-7 in a carbon dioxide catalytic conversion reaction.

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