Low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst, preparation method and application thereof
By synthesizing Ni/F-SiO2 precursor powder through a gel-assisted one-pot method and impregnating it with rare earth metals in steps to form a LaCe-Ni/F-SiO2 catalyst, the problems of easy sintering and insufficient low-temperature activity of Ni-based catalysts in CO2 methanation reaction were solved, achieving efficient CO2 conversion and CH4 selectivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGXIA HUI AUTONOMOUS REGION METROLOGY QUALITY INSPECTION & TESTING INST
- Filing Date
- 2026-04-02
- Publication Date
- 2026-07-03
AI Technical Summary
Ni-based catalysts are prone to sintering at high temperatures in CO2 methanation reactions, resulting in weak catalytic activity and insufficient catalytic activity at low temperatures, leading to poor CH4 selectivity.
Ni/F-SiO2 precursor powder was synthesized by gel-assisted one-pot method, and LaCe-Ni/F-SiO2 catalyst was formed by stepwise impregnation with lanthanum nitrate hexahydrate and cerium nitrate hexahydrate solution to avoid Ce agglomeration with nickel. By utilizing the electronic coupling and interfacial synergistic effect of La and Ce, the surface chemical state of nickel was adjusted to form a stable La-O-Si interface layer to inhibit the agglomeration of nickel nanoparticles.
It significantly improves CO2 conversion and CH4 selectivity under low temperature conditions, inhibits nickel nanoparticle aggregation, optimizes the chemical environment of the catalyst surface, and achieves higher catalytic activity and stability.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of CO2 methanation catalyst preparation technology, specifically relating to a low-temperature, highly active rare-earth metal modified nickel-based mesoporous catalyst, its preparation method, and its application. Background Technology
[0002] CO2 methanation technology can convert environmentally polluting CO2 into high-value CH4. This reaction has dual significance in environmental remediation and energy supply, making its application value prominent. Compared with the conversion pathway of CO2 into other high-value-added chemicals, CO2 methanation has the advantages of faster reaction rate and milder process conditions, and can be carried out under normal pressure, showing significant industrialization potential. The hydrogenation product CH4, as a core component of natural gas, can be directly used as fuel or chemical feedstock, thereby constructing a closed-loop carbon cycle system.
[0003] Despite its promising prospects, the CO2 methanation reaction still faces many technical bottlenecks, such as catalyst sintering at high temperatures, weak catalytic activity at low temperatures, and insufficient CH4 selectivity. Among various catalysts, Ni-based catalysts are considered an ideal alternative to precious metal catalysts due to their low cost, wide availability, and excellent CH4 selectivity.
[0004] However, Ni-based catalysts have inherent defects: their catalytic activity depends on a high reaction temperature, which is due to their high activation energy; in addition, CO2 methanation is a strongly exothermic reaction, and Ni particles are prone to agglomeration and sintering during the reaction, leading to catalyst deactivation and activity decay. Summary of the Invention
[0005] In view of this, the present invention provides a method for preparing a low-temperature, highly active rare earth metal modified nickel-based mesoporous catalyst that is conducive to CO2 methanation reaction as Ni particles are less prone to agglomeration and sintering.
[0006] A low-temperature, high-activity rare-earth metal-modified nickel-based mesoporous catalyst is also provided.
[0007] It is also necessary to provide an application of a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst in CO2 methanation.
[0008] The technical solution adopted by this invention to solve its technical problem is:
[0009] A method for preparing a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst includes the following steps:
[0010] S1: Nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine were used to synthesize 20wt% Ni / F-SiO2 precursor powder via a gel-assisted one-pot method.
[0011] S2: Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water to obtain lanthanum nitrate aqueous solution and cerium nitrate aqueous solution, respectively. First, the lanthanum nitrate aqueous solution is added dropwise to 20wt% Ni / F-SiO2 precursor powder for impregnation. After impregnation, it is dried to obtain single-modified powder. Then, the cerium nitrate aqueous solution is added dropwise to the single-modified powder for impregnation. After impregnation, it is dried to obtain double-modified powder. This is to allow the La and Ce salt solutions to slowly and uniformly wet the channels and surface of Ni / F-SiO2, and to avoid Ce agglomeration with nickel.
[0012] S3: The double-modified powder is calcined to uniformly load and activate lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, thus obtaining the LaCe-Ni / F-SiO2 catalyst.
[0013] Preferably, the content of La and Ce in the LaCe-Ni / F-SiO2 catalyst is 1-10 wt%.
[0014] Preferably, in step S2, the molar ratio of lanthanum nitrate hexahydrate to cerium nitrate hexahydrate is 1-2:1-2.
[0015] Preferably, in step S2, both the process of adding lanthanum nitrate aqueous solution dropwise to the 20wt% Ni / F-SiO2 precursor powder for impregnation and the process of adding cerium nitrate aqueous solution dropwise to the single-modified powder for impregnation require simultaneous ultrasonication during the addition.
[0016] Preferably, in step S2, the drying after impregnation is vacuum drying for 20-28 hours.
[0017] Preferably, in step S1, the 20wt% Ni / F-SiO2 precursor powder is prepared specifically through the following steps:
[0018] A. Dissolve nickel nitrate hexahydrate in anhydrous ethanol to obtain solution A;
[0019] B. Tetraethyl orthosilicate, tetraethylammonium hydroxide, and triethylamine were added dropwise to solution A, and the mixture was stirred for 5 h to obtain a light green gel B;
[0020] C. After aging gel B at room temperature for 10 h, vacuum dry for 24 h and grind to obtain powder C; to complete the self-assembly and initial solidification of metallic nickel and gel carrier. At the same time, the low temperature of vacuum drying can remove most of the free water and avoid nickel agglomeration.
[0021] D. Powder C is subjected to hydrothermal crystallization to form a mesoporous foam SiO framework in situ, and then calcined at 380℃-400℃ for 8h-12h to obtain 20wt% Ni / F-SiO2 precursor powder.
[0022] Preferably, in step S3, the calcination temperature is 380℃-420℃ and the calcination time is 2.5h-3.5h.
[0023] A low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst is prepared by the method described above. The catalyst comprises an active component, a support, and additives. The active component is Ni, the mesoporous support is a three-dimensional mesoporous silica foam (F-SiO2 support), and the additives are lanthanum and cerium. The specific surface area of the mesoporous support is 326.63 m². 2 / g, pore volume 0.31 cm 3 / g, the precursor of lanthanum additive is lanthanum nitrate hexahydrate, and the precursor of cerium additive is cerium nitrate hexahydrate.
[0024] The catalyst prepared by the low-temperature, high-activity rare-earth metal-modified nickel-based mesoporous catalyst as described above is applied in CO2 methanation under the following conditions: reaction pressure 2.0 MPa, reaction temperature 180℃-350℃, and reaction space velocity 3600 h⁻¹. −1 -10800h −1 The composition of the raw gas is H2:CO2:N2 = 60:15:25.
[0025] Preferably, at a reaction temperature of 200°C, the CO2 conversion rate reaches 69.66% and the CH4 selectivity reaches 99.40%.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0027] The present invention provides a method for preparing a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst. First, nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine are synthesized into a 20wt% Ni / F-SiO2 precursor powder via a gel-assisted one-pot method. Then, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water to obtain lanthanum nitrate aqueous solution and cerium nitrate aqueous solution, respectively. The lanthanum nitrate aqueous solution is first added dropwise to the 20wt% Ni / F-SiO2 precursor powder for impregnation, followed by drying to obtain a single-modified powder. Then, the cerium nitrate aqueous solution is added dropwise to the single-modified powder for impregnation, followed by drying to allow the La and Ce groups to react. Salt solution slowly and uniformly impregnates the pores and surface of Ni / F-SiO2, avoiding the agglomeration of Ce and nickel, to obtain a dual-modified powder. The dual-modified powder is then calcined to uniformly load and activate lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, preventing the activity of La and Ce from being imprisoned, thus obtaining a LaCe-Ni / F-SiO2 catalyst. Therefore, by using gel-assisted impregnation to synergistically introduce La and Ce dual rare earth promoters, the precise enhancement of the metal-support interaction and the significant improvement of catalytic performance are achieved through the electronic coupling and interfacial synergistic effect between the two. This not only effectively inhibits the agglomeration of nickel nanoparticles but also regulates the surface chemical state of nickel. Furthermore, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate can be converted into corresponding oxides or carbonate species under calcination and reaction atmosphere. On the one hand, the stepwise impregnation method of first impregnating with lanthanum and then with cerium allows lanthanum ions to preferentially interact strongly with the hydroxyl groups on the surface of the F-SiO2 support, forming a stable La-O-Si interface layer on the support surface. Moreover, La2O3 has a high melting point and strong thermal stability, which can act as a physical barrier to prevent the high-temperature agglomeration of cerium oxide and Ni particles formed by the subsequent addition of cerium. On the other hand, the carbonate species can be formed in situ by the precursor during the treatment process or further combined with adsorbed CO2 during the reaction. The surface modification of carbonate species can effectively regulate and enhance the alkalinity of the catalyst surface. The alkaline sites on the surface can enhance the adsorption and activation of acidic gas CO2, providing favorable conditions for the CO2 methanation reaction. This dual effect helps to inhibit the agglomeration of Ni particles and optimize the surface chemical environment of the CO2 methanation reaction, so as to exhibit better low-temperature catalytic activity in the CO2 hydrogenation reaction. Attached Figure Description
[0028] Figure 1 Images of the catalysts prepared in Example 1 and Comparative Example 1.
[0029] Figure 2 The nitrogen-adsorption-desorption curve and pore size distribution diagram are for Comparative Example 1.
[0030] Figure 3 The images show H2-TPR and CO2-TPD images of the catalysts prepared in Example 1 and Comparative Example 1.
[0031] In the picture: Figure 1 In the image, (a) is a scanning electron microscope (SEM) image of Comparative Example 1, (b) is a transmission electron microscope (TEM) image of Comparative Example 1, and (c) is a scanning electron microscope (SEM) image of Example 1. Figure 2 (a) shows the nitrogen adsorption-desorption curve of Comparative Example 1; (b) shows the pore size distribution of Comparative Example 1. Figure 3 (a) H2-TPR and (b) CO2-TPD images. Detailed Implementation
[0032] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0033] This application provides a method for preparing a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst, comprising the following steps:
[0034] S1: Nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine are used to synthesize 20wt% Ni / F-SiO2 precursor powder via a gel-assisted one-pot method to form a complete F-SiO2 mesoporous structure and high specific surface area without damaging the original Ni dispersion.
[0035] S2: Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water and added dropwise to 20wt% Ni / F-SiO2 precursor powder for impregnation. This allows the La and Ce salt solutions to slowly and uniformly wet the channels and surface of Ni / F-SiO2, ensuring high dispersion of La and Ce. This avoids excessively high local concentrations, which could lead to the aggregation of metal ions into large particles of hydroxides / oxides, affecting the electronic coupling and interfacial synergistic effect between rare earth metals, thus obtaining a dual-modified powder.
[0036] S3: The double-modified powder is aged overnight and calcined to uniformly disperse lanthanum nitrate hexahydrate and cerium nitrate hexahydrate on the surface of 20wt% Ni / F-SiO2 precursor powder, thereby completing the loading and activation of La and Ce promoters and obtaining LaCe-Ni / F-SiO2 catalyst.
[0037] The present invention provides a method for preparing a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst. First, nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine are synthesized into a 20wt% Ni / F-SiO2 precursor powder via a gel-assisted one-pot method. Then, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water to obtain lanthanum nitrate aqueous solution and cerium nitrate aqueous solution, respectively. The lanthanum nitrate aqueous solution is first added dropwise to the 20wt% Ni / F-SiO2 precursor powder for impregnation, followed by drying to obtain a single-modified powder. Then, the cerium nitrate aqueous solution is added dropwise to the single-modified powder for impregnation, followed by drying to allow the La and Ce groups to react. Salt solution slowly and uniformly impregnates the pores and surface of Ni / F-SiO2, avoiding the agglomeration of Ce and nickel, to obtain a dual-modified powder. The dual-modified powder is then calcined to uniformly load and activate lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, preventing the activity of La and Ce from being imprisoned, thus obtaining a LaCe-Ni / F-SiO2 catalyst. Therefore, by using gel-assisted impregnation to synergistically introduce La and Ce dual rare earth promoters, the precise enhancement of the metal-support interaction and the significant improvement of catalytic performance are achieved through the electronic coupling and interfacial synergistic effect between the two. This not only effectively inhibits the agglomeration of nickel nanoparticles but also regulates the surface chemical state of nickel. Furthermore, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate can be converted into corresponding oxides or carbonate species under calcination and reaction atmosphere. On the one hand, the stepwise impregnation method of first impregnating with lanthanum and then with cerium allows lanthanum ions to preferentially interact strongly with the hydroxyl groups on the surface of the F-SiO2 support, forming a stable La-O-Si interface layer on the support surface. Moreover, La2O3 has a high melting point and strong thermal stability, which can act as a physical barrier to prevent the high-temperature agglomeration of cerium oxide and Ni particles formed by the subsequent addition of cerium. On the other hand, the carbonate species can be formed in situ by the precursor during the treatment process or further combined with adsorbed CO2 during the reaction. The surface modification of carbonate species can effectively regulate and enhance the alkalinity of the catalyst surface. The alkaline sites on the surface can enhance the adsorption and activation of acidic gas CO2, providing favorable conditions for the CO2 methanation reaction. This dual effect helps to inhibit the agglomeration of Ni particles and optimize the surface chemical environment of the CO2 methanation reaction, so as to exhibit better low-temperature catalytic activity in the CO2 hydrogenation reaction.
[0038] Meanwhile, this invention first generates 20wt% Ni / F-SiO2 precursor powder, and then adds the required doped lanthanum nitrate hexahydrate and cerium nitrate hexahydrate. This avoids the damage to the pores and interference with the formation of the F-SiO2 mesoporous structure when they are added together in the one-pot gel synthesis, which would lead to a decrease in specific surface area and a poorer Ni dispersion. It also prevents lanthanum nitrate hexahydrate and cerium nitrate hexahydrate from being fixed inside the catalyst and unable to play an effective role.
[0039] Furthermore, the La and Ce content in the LaCe-Ni / F-SiO2 catalyst is 1-10 wt%, where the above content refers to the total mass percentage of La and Ce.
[0040] Furthermore, in S2, the molar ratio of lanthanum nitrate hexahydrate to cerium nitrate hexahydrate is 1-2:1-2.
[0041] Furthermore, in S2, during the process of adding lanthanum nitrate aqueous solution dropwise to 20wt% Ni / F-SiO2 precursor powder for impregnation, and during the process of adding cerium nitrate aqueous solution dropwise to the single-modified powder for impregnation, ultrasonication is required simultaneously with the addition.
[0042] Furthermore, the La and Ce content in the LaCe-Ni / F-SiO2 catalyst is 5wt%, wherein the mass ratio of LaCe:Ni:F-SiO2 is 5:20:75.
[0043] Furthermore, in S2, the molar ratio of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate is 1:1.
[0044] Furthermore, in step S2, the drying after impregnation is vacuum drying for 20-28 hours.
[0045] Furthermore, in S1, the 20wt% Ni / F-SiO2 precursor powder is specifically prepared through the following steps:
[0046] A. Dissolve nickel nitrate hexahydrate in anhydrous ethanol to obtain solution A;
[0047] B. Tetraethyl orthosilicate, tetraethylammonium hydroxide, and triethylamine are added dropwise to solution A and stirred for 5 h to obtain a light green gel B. Among them, tetraethyl orthosilicate serves as the sole silicon source, providing the basic structural unit of the SiO2 framework; tetraethylammonium hydroxide serves as a template agent, guiding the formation of specific channels; and triethylamine serves as a co-solvent, improving the compatibility of each component and making the gel more uniform. It also acts as an auxiliary template, affecting the pore size and pore structure.
[0048] C. After aging gel B at room temperature for 10 h, vacuum dry for 24 h and grind to obtain powder C; to complete the self-assembly and initial solidification of metallic nickel and gel carrier. At the same time, the low temperature of vacuum drying can remove most of the free water and avoid nickel agglomeration.
[0049] D. Powder C is hydrothermally crystallized to form a mesoporous foam SiO framework in situ, and then calcined at 380℃-400℃ for 8h-12h to remove the organic template at high temperature, thereby fixing and activating the Ni species to obtain 20wt% Ni / F-SiO2 precursor powder.
[0050] Furthermore, in step S3, the calcination temperature is 380℃-420℃, and the calcination time is 2.5h-3.5h.
[0051] A low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst is prepared by the method described above. The catalyst comprises an active component, a support, and additives. The active component is Ni, the mesoporous support is a three-dimensional mesoporous foam silica material, and the additives are lanthanum and cerium. The specific surface area of the mesoporous support is 326.63 m². 2 / g, pore volume 0.31 cm 3 / g, the precursor of lanthanum additive is lanthanum nitrate hexahydrate, and the precursor of cerium additive is cerium nitrate hexahydrate.
[0052] The catalyst prepared by the low-temperature, high-activity rare-earth metal-modified nickel-based mesoporous catalyst as described above is applied in CO2 methanation under the following conditions: reaction pressure 2.0 MPa, reaction temperature 180℃-350℃, and reaction space velocity 3600 h⁻¹. −1 -10800h −1 The composition of the raw gas is H2:CO2:N2 = 60:15:25.
[0053] Furthermore, at a reaction temperature of 200°C, the CO2 conversion rate reaches 69.66%, and the CH4 selectivity reaches 99.40%.
[0054] This application illustrates the present invention through the following embodiments and comparative examples. (Please carefully review the following embodiments and comparative examples.)
[0055] Example 1:
[0056] Preparation steps of 5 wt% La1Ce1-Ni / F-SiO2 catalyst:
[0057] S1: A 20wt% Ni / F-SiO2 precursor powder was synthesized from nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine via a gel-assisted one-pot method; the specific preparation method is as follows:
[0058] A. 3.49 g of nickel nitrate hexahydrate was dissolved in 20 mL of anhydrous ethanol to obtain solution A;
[0059] B. Under stirring at room temperature, 5.21 g of tetraethyl orthosilicate, 7.36 g of tetraethylammonium hydroxide, 4.97 g of triethylamine and water were added dropwise, and the mixture was stirred for 5 h to obtain a light green gel B;
[0060] C. After aging gel B at room temperature for 10 h, it was vacuum dried at 60 °C for 24 h and then ground to obtain powder C;
[0061] D. Powder C was hydrothermally crystallized at 180℃ for 6 h, and then calcined at 400℃ for 10 h to obtain 20wt% Ni / F-SiO2 precursor powder;
[0062] S2: 0.0332 g of lanthanum nitrate hexahydrate was dissolved in 5 mL of deionized water to obtain an aqueous solution of lanthanum nitrate. The aqueous solution of lanthanum nitrate was added dropwise to 20 wt% Ni / F-SiO2 precursor powder while sonicating. The impregnated solution was vacuum dried at 60 °C for 24 h to obtain a single-modified powder.
[0063] 0.0331 g of cerium nitrate hexahydrate was dissolved in 5 mL of deionized water to obtain an aqueous solution of cerium nitrate. The aqueous solution of cerium nitrate was added dropwise to the single-modified powder while sonicating. The impregnated solution was vacuum dried at 60 °C for 24 h to obtain a double-modified powder.
[0064] S3: The double-modified powder was calcined at 400℃ for 3h to obtain a 5%La1Ce1-Ni / F-SiO2 catalyst.
[0065] Evaluation of CO2 hydrogenation performance of 5% La1Ce1-Ni / F-SiO2 catalyst:
[0066] The prepared 5% La1Ce1-Ni / F-SiO2 was pressed into tablets and sieved to obtain particles with a size of 20–40 mesh. 0.2 g of the above catalyst was loaded into a fixed-bed reactor and reduced in high-purity H2 under programmed temperature conditions of 400 °C, 0.1 MPa, and 3600 mL·g⁻¹. cat -1 ·h -1 2 h. After reduction, the temperature was lowered and the reaction was switched to feed gas (H2:CO2:N2 = 60:15:25) for 2 hours. The reaction conditions were 200°C, 2.0 MPa, and 3600 mL·g. cat -1 ·h -1 The reaction results are shown in Table 1.
[0067] Example 2:
[0068] The only difference from Example 1 is the amount of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate added. The amounts added are 0.0061 g of lanthanum nitrate hexahydrate and 0.0060 g of cerium nitrate hexahydrate. Everything else is the same as in Example 1, resulting in a 1% La1Ce1-Ni / F-SiO2 catalyst.
[0069] The CO2 hydrogenation performance evaluation of the 1% La1Ce1-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0070] Example 3:
[0071] The only difference from Example 1 is the amount of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate added. The amounts added are 0.0183 g of lanthanum nitrate hexahydrate and 0.0180 g of cerium nitrate hexahydrate. Everything else is the same as in Example 1, resulting in a 3 wt% La1Ce1-Ni / F-SiO2 catalyst.
[0072] The CO2 hydrogenation performance evaluation of the 3 wt% La1Ce1-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0073] Example 4:
[0074] The only difference from Example 1 is the amount of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate added. The amounts added are 0.0613 g of lanthanum nitrate hexahydrate and 0.0602 g of cerium nitrate hexahydrate. Everything else is the same as in Example 1, resulting in a 10wt% La1Ce1-Ni / F-SiO2 catalyst.
[0075] The CO2 hydrogenation performance evaluation of the 10 wt% La1Ce1-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0076] Example 5:
[0077] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0078] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 180°C, 2.0 MPa, and 3600 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0079] Example 6:
[0080] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0081] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 250 °C, 2.0 MPa, and 3600 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0082] Example 7:
[0083] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0084] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 300°C, 2.0 MPa, and 3600 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0085] Example 8:
[0086] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0087] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 350 °C, 2.0 MPa, and 3600 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0088] Example 9:
[0089] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0090] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 200 °C, 2.0 MPa, and 7200 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0091] Example 10:
[0092] The preparation method of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst is the same as that in Example 1.
[0093] In the evaluation of the CO2 hydrogenation performance of the 5 wt% La1Ce1-Ni / F-SiO2 catalyst, the reaction conditions were 200 °C, 2.0 MPa, and 10800 mL·g. cat -1 ·h -1 Everything else was the same as in Example 1. The reaction results are shown in Table 1.
[0094] Example 11:
[0095] The only difference from Example 1 is the amount of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate added. The amounts added are 0.0244 g of lanthanum nitrate hexahydrate and 0.0060 g of cerium nitrate hexahydrate. Everything else is the same as in Example 1, resulting in a 5 wt% La2Ce1-Ni / F-SiO2 catalyst.
[0096] The CO2 hydrogenation performance evaluation of the 5 wt% La2Ce1-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0097] Example 12:
[0098] The only difference from Example 1 is the amount of lanthanum nitrate hexahydrate and cerium nitrate hexahydrate added. The amounts added are 0.0061 g of lanthanum nitrate hexahydrate and 0.02240 g of cerium nitrate hexahydrate. Everything else is the same as in Example 1, resulting in a 5wt% La1Ce2-Ni / F-SiO2 catalyst.
[0099] The CO2 hydrogenation performance evaluation of the 5 wt% La1Ce2-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0100] Comparative Example 1:
[0101] A. 3.49 g of nickel nitrate hexahydrate was dissolved in 20 mL of anhydrous ethanol to obtain solution A;
[0102] B. Under stirring at room temperature, 5.21 g of tetraethyl orthosilicate, 7.36 g of tetraethylammonium hydroxide, and 4.97 g of triethylamine were added dropwise, and the mixture was stirred for 5 h to obtain a light green gel B.
[0103] C. After aging gel B at room temperature for 10 h, vacuum drying for 24 h, and grinding to obtain powder C;
[0104] D. Powder C was hydrothermally crystallized at 180℃ for 6 h, and then calcined at 400℃ for 10 h to obtain a 20wt% Ni / F-SiO2 catalyst;
[0105] The CO2 hydrogenation performance evaluation of the 20wt% Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0106] Comparative Example 2:
[0107] The only difference from Example 1 is step S2; everything else is the same as in Example 1. In S2: 0.0664 g of lanthanum nitrate hexahydrate is dissolved in 5 mL of deionized water to obtain an aqueous solution of lanthanum nitrate. The aqueous solution of lanthanum nitrate is added dropwise to 20 wt% Ni / F-SiO2 precursor powder while being sonicated. The impregnated solution is then vacuum dried at 60°C for 24 h to obtain a single-modified powder.
[0108] S3: The modified powder was calcined at 400℃ for 3h to obtain a 5% La-Ni / F-SiO2 catalyst.
[0109] The CO2 hydrogenation performance evaluation of the 5% La-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0110] Comparative Example 3
[0111] The only difference from Example 1 is step S2; everything else is the same as in Example 1. In S2: 0.0662 g of cerium nitrate hexahydrate is dissolved in 5 mL of deionized water to obtain an aqueous solution of cerium nitrate. The aqueous solution of cerium nitrate is added dropwise to 20 wt% Ni / F-SiO2 precursor powder while being sonicated. The impregnated solution is then vacuum dried at 60°C for 24 h to obtain a single-modified powder.
[0112] S3: The modified powder was calcined at 400℃ for 3 hours to obtain a 5% Ce-Ni / F-SiO2 catalyst.
[0113] The CO2 hydrogenation performance evaluation of the 5%Ce-Ni / F-SiO2 catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0114] Comparative Example 4:
[0115] The only difference from Example 1 is step S2; everything else is the same as in Example 1.
[0116] S2: 0.0332 g of lanthanum nitrate hexahydrate was dissolved in 5 mL of deionized water to obtain an aqueous solution of lanthanum nitrate. The aqueous solution of lanthanum nitrate was added dropwise to 20 wt% Ni / F-SiO2 precursor powder while sonicating. The impregnated solution was vacuum dried at 60 °C for 24 h to obtain a single-modified powder.
[0117] 0.0331 g of cerium nitrate hexahydrate was dissolved in 5 mL of deionized water to obtain an aqueous solution of cerium nitrate. The aqueous solution of cerium nitrate was added dropwise to the single-modified powder while sonicating. The mixture was impregnated to obtain a double-modified solution. The double-modified solution was heated for 24 h and dried to obtain the double-modified powder.
[0118] A 5 wt% La1Ce1-Ni / F-SiO2-HD catalyst was prepared.
[0119] The CO2 hydrogenation performance evaluation of the 5 wt% La1Ce1-Ni / F-SiO2-HD catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0120] Comparative Example 5:
[0121] The only difference from Example 1 is step S2; everything else is the same as in Example 1.
[0122] S2: 0.0332 g of lanthanum nitrate hexahydrate and 0.0331 g of cerium nitrate hexahydrate were dissolved in 5 mL of deionized water to obtain a mixed solution. The mixed solution was added dropwise to 20 wt% Ni / F-SiO2 precursor powder for impregnation while sonicating. The impregnated solution was vacuum dried at 60 °C for 24 h to obtain the double-modified powder.
[0123] A 5 wt% La1Ce1-Ni / F-SiO2-One-pot catalyst was prepared.
[0124] The CO2 hydrogenation performance evaluation of the 5 wt% La1Ce1-Ni / F-SiO2-One-pot catalyst was the same as in Example 1. The reaction results are shown in Table 1.
[0125] Table 1
[0126]
[0127] As shown in Table 1 above, Examples 1-4 represent LaCe-Ni / F-SiO2 catalysts with different La and Ce doping amounts. Examples 1 and 5-8 represent the carbon dioxide methanation reaction of 5wt% La1Ce1-Ni / F-SiO2 at different temperatures. Examples 1, 9, and 10 represent the carbon dioxide methanation reaction of 5wt% La1Ce1-Ni / F-SiO2 at different space velocities. Examples 1 and 11-12 represent the carbon dioxide methanation reaction with the same total La and Ce content, differing only in the La and Ce ratios. Examples 1-4 show that 5wt% La1Ce1-Ni / F-SiO2 exhibits the best catalytic performance, achieving a CO2 conversion rate of 69.46% and a CH4 selectivity of 99.40% at a low temperature of 200℃. Compared to Ni / F-SiO2 prepared by the medium-volume impregnation method in Comparative Example 1, the CO2 conversion rate is more than twice higher. As can be seen from Examples 1 and 5-10, the 5wt% La1Ce1-Ni / F-SiO2 catalyst prepared in this invention exhibits good performance at 180℃ for 10800 h. -1 The reaction can still be catalyzed. To ensure conversion efficiency and energy conservation, the preferred reaction temperature is 200℃ and the reaction space velocity is 3600 h⁻¹. -1 As can be seen from Examples 1 and 11-12, when the total proportion of rare earth elements is the same, the proportion of each rare earth element has a significant impact on CO2 conversion rate and CH4 selectivity.
[0128] Examples 1-4 and Comparative Examples 1, 2, and 3 fully demonstrate that a single rare earth metal enhances the electronic regulation and metal-support interaction of nickel-based catalysts. However, this does not mean that the addition of multiple different types of rare earth metals can achieve the expected effect. The desired effect can only be achieved by considering the selected synthesis method, doping amount, ratio between different rare earth metals, and electronic coupling.
[0129] A comparison of Example 1 with Comparative Examples 1, 5, and 6 shows that the CO2 conversion rate of this invention is significantly improved compared to undoped or single-doped samples. This indicates that the synergistic introduction of La and Ce dual rare earth additives, through electronic coupling and interfacial synergistic effects between the two, achieves precise enhancement of the metal-support interaction and a significant improvement in catalytic performance. Furthermore, the anchoring effect of the F-SiO2 framework and the synergistic effect of the rare earth metals (La and Ce) create favorable conditions for the CO2 methanation reaction, facilitating CO2 methanation.
[0130] As can be seen from Examples 1 and Comparative Examples 4 and 5, the method of adding rare earth elements (how to add them) and the treatment method (how to dry them after impregnation) have a significant impact on CO2 conversion rate and CH4 selectivity. This invention adopts a stepwise impregnation method of first adding lanthanum and then adding cerium, which allows lanthanum ions to preferentially interact strongly with the hydroxyl groups on the surface of the F-SiO2 support, forming a stable La-O-Si interface layer on the support surface; moreover, La2O3 has a high melting point and strong thermal stability, which can act as a physical barrier to prevent the subsequent high-temperature agglomeration of CeO2 and Ni particles.
[0131] The 5wt% La1Ce1-Ni / F-SiO2 of Example 1 and the 20wt% Ni / F-SiO2 of Comparative Example 1 were examined by scanning electron microscopy and transmission electron microscopy, and the scanning electron microscopy images are shown below. Figure 1 As shown.
[0132] The 20wt% Ni / F-SiO2 of Comparative Example 1 was analyzed by nitrogen physical adsorption and pore size measurement, and the nitrogen adsorption-desorption curve and pore size distribution were obtained, as shown in the figure. Figure 2 As shown.
[0133] The 5wt% La1Ce1-Ni / F-SiO2 and 20wt% Ni / F-SiO2 prepared in Example 1 and Comparative Example 1 were subjected to a reduction reaction in a reducing atmosphere (H2), and the results were detected as follows. Figure 3 The H2-TPR image shown in (a) was obtained by detecting the desorption of CO2 molecules adsorbed on the catalyst surface using programmed temperature rise. Figure 3 (b) shows the CO2-TPD image.
[0134] Depend on Figure 1As can be seen, the scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the 20 wt% Ni / F-SiO2 catalyst in Comparative Example 1 demonstrate that it possesses a foam structure. The SEM images of the 20 wt% Ni / F-SiO2 catalyst and the 5% La1Ce1-Ni / F-SiO2 catalyst in Comparative Example 1 are shown below. Figure 1 a and c indicate that the introduction of rare earth metals can effectively disperse Ni species and inhibit the aggregation of Ni nanoparticles.
[0135] Figure 2 Example a shows 20wt% Ni / F-SiO2 from Comparative Example 1. According to IUPAC classification, the 20wt% Ni / F-SiO2 from Comparative Example 1 exhibits a Type IV isotherm, indicating that it possesses a three-dimensional mesoporous structure. Combined with... Figure 2 The pore size distribution diagram in b further verifies that the 20wt% Ni / F-SiO2 in Comparative Example 1 is mainly mesoporous with a relatively concentrated pore size distribution.
[0136] Figure 3 The results of temperature-programmed reduction (H2-TPR) and temperature-programmed desorption (CO2-TPD) of two catalysts, 20wt%Ni / F-SiO2 and 5wt%La1Ce1-Ni / F-SiO2, were presented to analyze their reduction performance and CO2 adsorption capacity. The results show that the La and Ce modified 5%La1Ce1-Ni / F-SiO2 catalyst, compared to 20wt%Ni / F-SiO2, enhances the interaction between Ni species and the F-SiO2 support, and introduces more medium-to-strong basic sites, significantly improving its CO2 adsorption and activation capacity. This dual modification effect synergistically optimizes the catalyst's reduction performance and CO2 adsorption capacity, laying the foundation for its superior low-temperature catalytic activity and stability in CO2 hydrogenation reactions. The introduction of La and Ce enhances the metal-support interaction through the electronic effect of the Ni-LaCe interface, while the surface alkaline environment is modified by the carbonation of La. This dual effect helps to suppress Ni particle agglomeration and optimize the surface chemical environment for the CO2 methanation reaction.
[0137] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.
Claims
1. A method for preparing a low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst, characterized in that, Includes the following steps: S1: Nickel nitrate hexahydrate, tetraethylammonium hydroxide, and triethylamine were used to synthesize 20wt% Ni / F-SiO2 precursor powder via a gel-assisted one-pot method. S2: Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dissolved in deionized water to obtain lanthanum nitrate aqueous solution and cerium nitrate aqueous solution, respectively. First, the lanthanum nitrate aqueous solution is added dropwise to 20wt% Ni / F-SiO2 precursor powder for impregnation. After impregnation, it is dried to obtain single-modified powder. Then, the cerium nitrate aqueous solution is added dropwise to the single-modified powder for impregnation. After impregnation, it is dried to obtain double-modified powder. This is to allow the La and Ce salt solutions to slowly and uniformly wet the channels and surface of Ni / F-SiO2, and to avoid Ce agglomeration with nickel. S3: The double-modified powder is calcined to uniformly load and activate lanthanum nitrate hexahydrate and cerium nitrate hexahydrate, thus obtaining the LaCe-Ni / F-SiO2 catalyst.
2. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 1, characterized in that, The La and Ce contents in the LaCe-Ni / F-SiO2 catalyst are 1-10 wt%.
3. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 2, characterized in that, In S2, the molar ratio of lanthanum nitrate hexahydrate to cerium nitrate hexahydrate is 1-2:1-2.
4. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 3, characterized in that, In step S2, both the process of adding lanthanum nitrate aqueous solution dropwise to the 20wt% Ni / F-SiO2 precursor powder for impregnation and the process of adding cerium nitrate aqueous solution dropwise to the single-modified powder for impregnation require simultaneous ultrasonication during the addition.
5. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 3, characterized in that, In step S2, the drying process after impregnation is vacuum drying, which lasts for 20-28 hours.
6. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 3, characterized in that, In step S1, the 20wt% Ni / F-SiO2 precursor powder is prepared specifically through the following steps: A. Dissolve nickel nitrate hexahydrate in anhydrous ethanol to obtain solution A; B. Tetraethyl orthosilicate, tetraethylammonium hydroxide, and triethylamine were added dropwise to solution A, and the mixture was stirred for 5 h to obtain a light green gel B; C. After aging gel B at room temperature for 10 h, vacuum dry for 24 h and grind to obtain powder C; to complete the self-assembly and initial solidification of metallic nickel and gel carrier. At the same time, the low temperature of vacuum drying can remove most of the free water and avoid nickel agglomeration. D. Powder C is subjected to hydrothermal crystallization to form a mesoporous foam SiO framework in situ, and then calcined at 380℃-400℃ for 8h-12h to obtain 20wt% Ni / F-SiO2 precursor powder.
7. The preparation method of the low-temperature high-activity rare earth metal modified nickel-based mesoporous catalyst as described in claim 4, characterized in that, In step S3, the calcination temperature is 380℃-420℃, and the calcination time is 2.5h-3.5h.
8. A low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst, characterized in that, The catalyst is prepared by the method for preparing a low-temperature, highly active rare-earth metal modified nickel-based mesoporous catalyst according to any one of claims 1-7. The catalyst comprises an active component, a support, and an additive. The active component is Ni, the mesoporous support is a three-dimensional mesoporous foam silica material, and the additives are lanthanum and cerium. The specific surface area of the mesoporous support is 326.63 m². 2 / g, pore volume 0.31 cm 3 / g, the precursor of lanthanum additive is lanthanum nitrate hexahydrate, and the precursor of cerium additive is cerium nitrate hexahydrate.
9. The application of the catalyst prepared by the method for preparing the low-temperature, highly active rare-earth metal modified nickel-based mesoporous catalyst according to any one of claims 1-7 in the CO2 methanation, characterized in that, Reaction pressure 2.0 MPa, reaction temperature 180℃-350℃, reaction space velocity 3600 h⁻¹ −1 -10800h −1 The composition of the raw gas is H2:CO2:N2 = 60:15:
25.
10. The application of the low-temperature, highly active rare-earth metal-modified nickel-based mesoporous catalyst as described in any one of claims 9, characterized in that, At a reaction temperature of 200°C, the CO2 conversion rate reached 69.66%, and the CH4 selectivity reached 99.40%.