Preparation method of nickel-based methane carbon dioxide reforming catalyst

Abstract

The invention discloses a preparation method of a nickel-based methane carbon dioxide reforming catalyst, which comprises the following steps: (1) dropwise adding tetraethyl orthosilicate into deionized water to form a uniform mixed solution; (2) adding a complexing agent into the mixed solution, stirring and uniformly mixing in a water bath, adding nickel salt and uniformly mixing; (3) after standing, adding ammonia water, uniformly stirring and mixing in a water bath to form gel, adding deionized water, and centrifugally cleaning for multiple times; and (4) drying the cleaned product, and calcining to obtain the Ni / SiO2 catalyst. The preparation method is simple, and the prepared catalyst has good methane and carbon dioxide reforming activity and stability and also has good carbon deposition resistance.

Description

Technical Field

[0001] This invention relates to the field of catalyst production technology, and in particular to a method for preparing a nickel-based methane carbon dioxide reforming catalyst. Background Technology

[0002] The methane-carbon dioxide reforming reaction (also known as dry reforming, DRM), with its main reaction being CO2 + CH4 → 2CO + 2H2, can directly convert two major greenhouse gases (CH4 and CO2) into high-value-added syngas (CO and H2). This reaction not only provides a new pathway for the comprehensive utilization of natural gas, shale gas, and the conversion of biomass methane, but also demonstrates enormous environmental value and economic potential in reducing greenhouse gas emissions. Therefore, the development of efficient and stable DRM catalysts has been a research hotspot in the fields of energy chemical engineering and catalysis in recent years.

[0003] Among numerous DRM catalysts, nickel (Ni)-based catalysts are considered one of the most promising catalyst systems for industrial applications due to their relatively low cost and high catalytic activity. However, nickel-based catalysts face two key scientific and technological challenges when operating under harsh DRM reaction conditions (typically above 700°C) for extended periods: 1) Carbon deposition deactivation: Reactants CH4 and potential intermediates are prone to deep cracking or CO disproportionation reactions at nickel active sites, generating solid carbon species (such as amorphous carbon, carbon nanotubes, or graphitic carbon). These carbon species can cover active sites, clog catalyst pores, and even lead to catalyst particle breakage and increased reactor pressure drop, severely reducing catalytic activity and shortening catalyst lifetime. 2) Sintering deactivation: At high temperatures, high surface energy metallic nickel nanoparticles tend to aggregate through mechanisms such as surface migration and Ostwald ripening, forming larger particles. Sintering not only reduces the specific surface area and the number of surface active sites of active metals, but is also often accompanied by more severe carbon deposition, because larger nickel particles are more catalytically active for carbon chain growth reactions, thus forming a vicious cycle intensifying carbon deposition and promoting sintering.

[0004] To address the aforementioned issues, existing technologies primarily focus on controlling the size, dispersion, and interaction between nickel species and the support. A common strategy involves using complex preparation processes (such as sol-gel, microemulsion, and deposition-precipitation methods) or introducing structural additives to obtain highly dispersed, small-sized nickel nanoparticles. Theoretical and pilot-scale studies have shown that smaller nickel particle sizes can limit the nucleation and growth of carbon fibers, thereby improving the catalyst's resistance to carbon deposition to some extent. However, this strategy has significant limitations in practice: excessively small nickel nanoparticles (typically <5 nm) are prone to migration and aggregation in high-temperature reaction environments due to their extremely high surface energy and thermodynamic instability, i.e., sintering, which leads to rapid catalyst deactivation. Therefore, in the DRM reaction, balancing the size effect of nickel particles—being small enough to suppress carbon deposition while being stable enough to resist sintering—becomes a challenging trade-off.

[0005] Furthermore, many existing methods, in pursuit of high performance, often involve multi-step synthesis, expensive template agents, or specialized equipment, resulting in complex preparation processes, high costs, and poor reproducibility, making it difficult to meet the economic and reliability requirements of large-scale industrial production. For example, some studies stabilize nickel particles by constructing core-shell structures or strong interactions, but the synthesis steps are cumbersome; other studies improve performance by adding large amounts of noble metal promoters (such as Pt, Pd) or rare earth elements, but this significantly increases catalyst costs. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a nickel-based methane-carbon dioxide reforming catalyst. The preparation method is simple, and the obtained catalyst has good methane-carbon dioxide reforming activity and stability, as well as good resistance to carbon deposition.

[0007] The technical solution adopted by this invention to solve its technical problem is: A method for preparing a nickel-based methane carbon dioxide reforming catalyst includes the following steps: (1) Add tetraethyl orthosilicate dropwise to deionized water to form a homogeneous mixture; (2) Add complexing agent to the mixture, stir and mix in a water bath, then add nickel salt and mix well; (3) After standing, add ammonia water, stir in a water bath to mix and form a gel, add deionized water and centrifuge and wash several times. (4) The cleaned product is dried and then calcined to obtain Ni / SiO2 catalyst.

[0008] This invention utilizes tetraethyl orthosilicate and nickel nitrate for direct in-situ synthesis of a catalyst, significantly enhancing its resistance to carbon deposition. In the Ni / SiO2 catalyst, Ni exists in the form of NiO.

[0009] This invention employs a one-step in-situ synthesis strategy. The core of this strategy lies in the simultaneous introduction of a nickel precursor and a complexing agent during the hydrolysis and condensation of a silicon source (tetraethyl orthosilicate) to form a silica network. Citric acid forms a stable complex with nickel ions, achieving a highly uniform dispersion of nickel species at the molecular level. Subsequently, under the catalysis of ammonia, the system undergoes a sol-gel transition, where the uniformly distributed nickel-complex is in-situ "encapsulated" or "anchored" within the forming SiO2 gel network. After subsequent drying and calcination, a Ni / SiO2 catalyst with strong interactions between the nickel species and the SiO2 support is obtained. This structural feature ensures that after calcination, nickel exists primarily as highly dispersed NiO, effectively inhibiting the migration and agglomeration of metallic nickel particles during subsequent reduction and use. Based on its unique structure, the catalyst prepared by this method possesses both excellent anti-sintering stability and anti-coking ability, successfully solving the traditional trade-off problem of "small size, anti-coking but prone to sintering" in catalyst design.

[0010] Preferably, the complexing agent is citric acid monohydrate.

[0011] Preferably, the nickel salt is Ni(NO)3·6H2O.

[0012] As a preferred option, in step (2), the water bath stirring parameters are: stirring in a water bath at 20-70℃ for 0.5-3 hours.

[0013] As a preferred option, in step (3), ammonia is added after standing for 1-2 hours.

[0014] Preferably, in step (3), the mass concentration of ammonia water is 10%-25%.

[0015] As a preferred option, in step (3), the water bath stirring parameters are: stirring in a water bath at 20-70℃ for 1-3 hours.

[0016] Preferably, in step (4), the drying process is carried out at a temperature of 60-150℃ for 10-15 hours.

[0017] Preferably, in step (4), the calcination is carried out at 300-900℃ for 3-6 hours.

[0018] As a preferred embodiment, the ratio of tetraethyl orthosilicate:deionized water:complexing agent:nickel salt:ammonia is 1 mL:2-20 mL:0.002-0.1 g:0.01-0.30 g:0.5-5 mL. The optimal conditions are: tetraethyl orthosilicate:deionized water:complexing agent:nickel salt:ammonia = 9 mL:100 mL:0.1 g:0.632 g:18 mL.

[0019] The beneficial effects of this invention are: This invention provides a simple and low-cost method for preparing a nickel-based methane carbon dioxide reforming catalyst. By employing a one-step in-situ synthesis strategy, a nickel source and complexing agent (such as citric acid monohydrate) are introduced in the early stages of silica sol formation, allowing nickel species to be highly uniformly embedded into the SiO2 support framework during subsequent gelation and calcination. The prepared Ni / SiO2 catalyst has the following outstanding advantages: (1) The nickel particles have a uniform and moderate size distribution, exhibiting excellent anti-sintering stability during high-temperature reactions; (2) The enhanced metal-support interaction effectively modulates the electronic state of the nickel surface, inhibits the deep cracking of methane and the disproportionation reaction of CO, thereby significantly improving the catalyst’s resistance to carbon deposition. (3) The catalyst can maintain a high and stable CH4 and CO2 conversion rate and has a long lifespan during long-term methane-carbon dioxide reforming reactions. This invention ingeniously overcomes the bottleneck of traditional methods, which make it difficult to simultaneously achieve "anti-carbon deposition" and "anti-sintering" of nickel particle size, through improved preparation methods. Attached Figure Description

[0020] Figure 1 This is a comparison graph of the conversion rate and thermogravimetric results of the catalyst in Example 1 and the catalyst in Comparative Example 1; Figure 2 This is a thermogravimetric analysis (TGA) result of the Ni / SiO2 catalyst in Example 1 after the catalytic reaction. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0022] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available or commonly used in the field. The methods described in the following embodiments are conventional methods in the field, unless otherwise specified.

[0023] Example 1: First, 9 ml of tetraethyl orthosilicate (TEOS) was added dropwise to 100 ml of deionized water to form a homogeneous mixture. Then, 0.1 g of citric acid monohydrate was added as a complexing agent. After stirring in a 40°C water bath for 30 min, 0.632 g of Ni(NO)3·6H2O was added. After 1 h, 18 ml of ammonia (20 wt%) was added to the mixture. The mixture was then stirred in a 40°C water bath for 2 h to form a gel. The gel was then washed three times with deionized water by centrifugation to remove excess ions and unreacted substances. The washed catalyst was then placed in an oven and dried at 110°C for 12 h. Finally, the dried catalyst was placed in a muffle furnace and calcined at 600°C at a rate of 2°C / min for 4 h to obtain the Ni / SiO2 catalyst. The Ni content of the catalyst was 5% by mass.

[0024] Comparative Example 1: Preparation by Impregnation Method First, the SiO2 support was prepared by dropwise adding 9 ml of tetraethyl orthosilicate (TEOS) to 100 ml of deionized water to form a homogeneous mixture. After 1 h, 18 ml of ammonia (20 wt%) was added to the mixture, and the mixture was heated in a 40°C water bath for 2 h to form a gel. The gel was then washed three times with deionized water by centrifugation to remove excess ions and unreacted substances. The washed support was then placed in an oven and dried at 110°C for 12 h. Finally, the dried catalyst was placed in a muffle furnace and calcined at 600°C for 4 h at a rate of 2°C / min to obtain the SiO2 support. Then, 5 mL of water containing 0.632 g of Ni(NO)3·6H2O was dissolved and added dropwise to the SiO2 support using an impregnation method. After standing for 12 h, the mixture was dried at 110°C for 12 h and calcined at 600°C for 4 h to obtain the Ni / SiO2-IM catalyst. The catalyst has a Ni content of 5% by mass, and IM represents the impregnation method.

[0025] Catalyst performance test conditions (1) Weigh 20 mg of catalyst and load it into a quartz tube reactor. Before the reaction, the catalyst is reduced with a 20% H2 / Ar mixture at 700℃ for 40 minutes. Then, the reaction gases (CO2: 15 ml / min, CH4: 15 ml / min, Ar: 15 ml / min) are introduced to start the reaction, and the reaction test temperature is 700℃. The composition of the gas generated in the reaction is detected using a gas chromatograph, and the methane conversion rate of each catalyst is calculated.

[0026] Catalyst performance test results: Depend on Figure 1 It can be seen that the methane and carbon dioxide conversion rates of the Ni / SiO2 catalyst in Example 1 are significantly higher than those of the Ni / SiO2-IM catalyst in Comparative Example 1. The activity of the Ni / SiO2-IM catalyst decreased significantly after 20 hours of reaction, and the reaction terminated due to excessive carbon buildup causing blockage of the reaction tube. Furthermore, the performance of the N / SiO2 catalyst remained relatively stable within 100 hours, indicating that the Ni / SiO2 catalyst possesses higher activity and stability in the methane and carbon dioxide reforming reaction. Figure 2 Thermogravimetric analysis results showed that the Ni- / SiO2 catalyst did not exhibit significant carbon deposition after the reaction. These results indicate that the Ni- / SiO2 catalyst possesses good activity and stability in methane-carbon dioxide reforming, and also demonstrates strong resistance to carbon deposition.

[0027] Example 2: First, 1 ml of tetraethyl orthosilicate (TEOS) was added dropwise to 2 ml of deionized water to form a homogeneous mixture. Then, 0.002 g of citric acid monohydrate was added as a complexing agent. After stirring in a water bath at 20 °C for 3 hours, 0.01 g of Ni(NO)3·6H2O was added. After 1 hour, 0.5 ml of ammonia (25 wt%) was added to the mixture. The mixture was then stirred in a water bath at 20 °C for another 3 hours to form a gel. Afterward, the catalyst was washed three times by centrifugation with deionized water to remove excess ions and unreacted substances. The washed catalyst was then placed in an oven and dried at 60 °C for 15 hours. Finally, the dried catalyst was placed in a muffle furnace and calcined at 300 °C for 6 hours at a rate of 2 °C / min to obtain the Ni / SiO2 catalyst.

[0028] Example 3: First, 1 ml of tetraethyl orthosilicate (TEOS) was added dropwise to 20 ml of deionized water to form a homogeneous mixture. Then, 0.1 g of citric acid monohydrate was added as a complexing agent. After stirring in a 70°C water bath for 30 min, 0.3 g of Ni(NO)3·6H2O was added. After 2 h, 5 ml of ammonia (10 wt%) was added to the mixture. The mixture was then stirred in a 70°C water bath for 1 h to form a gel. The gel was then washed three times with deionized water by centrifugation to remove excess ions and unreacted substances. The washed catalyst was then placed in an oven and dried at 150°C for 10 h. Finally, the dried catalyst was placed in a muffle furnace and calcined at 900°C at a rate of 2°C / min for 3 h to obtain the Ni / SiO2 catalyst.

[0029] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for producing a nickel-based catalyst for methane carbon dioxide reforming, characterized by, Includes the following steps: (1) Add tetraethyl orthosilicate dropwise to deionized water to form a homogeneous mixture; (2) Add complexing agent to the mixture, stir and mix in a water bath, then add nickel salt and mix well; (3) After standing, add ammonia water, stir in a water bath to mix and form a gel, add deionized water and centrifuge and wash several times. (4) The cleaned product is dried and then calcined to obtain Ni / SiO2 catalyst.

2. The preparation method according to claim 1, characterized in that, The complexing agent is citric acid monohydrate.

3. The preparation method according to claim 1, characterized in that, The nickel salt is Ni(NO)3·6H2O.

4. The preparation method according to claim 1, characterized in that, In step (2), the water bath stirring parameters are: 20-70℃ water bath stirring for 0.5-3 hours.

5. The preparation method according to claim 1, characterized in that, In step (3), ammonia water is added after standing for 1-2 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass concentration of ammonia water is 10%-25%.

7. The preparation method according to claim 1, characterized in that, In step (3), the water bath stirring parameters are: 20-70℃ water bath stirring for 1-3 hours.

8. The preparation method according to claim 1, characterized in that, In step (4), the drying process involves drying at 60-150℃ for 10-15 hours.

9. The preparation method according to claim 1, characterized in that, In step (4), calcination is carried out at 300-900℃ for 3-6 hours.

10. The preparation method according to claim 1, characterized in that, Tetraethyl orthosilicate: Deionized water: Complexing agent: Nickel salt: Ammonia = 1 mL: 2-20 mL: 0.002-0.1 g: 0.01-0.30 g: 0.5-5 mL.

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