Nickel-based catalyst doped with rare earth elements and preparation method

Abstract

The invention belongs to the technical field of catalysts for biomass gasifiers, and particularly relates to a nickel-based catalyst doped with rare earth elements and a preparation method of the nickel-based catalyst doped with the rare earth elements. Al2O3: 65%-70%; 3%-5% of MgO; 2%-4% of SiO2; and 2%-5% of rare earth elements. The catalyst has the advantages that the specific surface area is increased, the adaptive temperature range is widened, and the catalyst has high catalytic activity, excellent thermal stability, good anti-coking performance and long service life and is particularly suitable for tar cracking reaction of a biomass gasifier under the high-temperature condition. The porous graded pore structure design and the nano-particle dispersion technology reduce the adsorption and deposition of macromolecular hydrocarbons on the surface of the catalyst, and significantly reduce the risk of carbon deposition.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts for biomass gasifiers, and particularly relates to a rare earth element-doped nickel-based catalyst and a preparation method thereof. Background Art

[0002] Nickel-based catalysts have been widely used in fields such as petroleum refining, biomass conversion, and tar cracking due to their good catalytic activity and relatively low cost. However, traditional nickel-based catalysts are prone to problems such as sintering and carbon deposition (coking) under high-temperature conditions, resulting in a rapid decline in their activity and a short service life. These problems are particularly prominent in high-temperature reaction processes such as tar cracking in biomass gasifiers. To solve this problem, researchers have tried to improve the performance of nickel-based catalysts through various methods, such as adding promoters and optimizing the catalyst structure.

[0003] In recent years, rare earth elements have been widely used in the modification research of catalysts due to their unique molecular structure and excellent catalytic performance. However, the existing rare earth element-doped nickel-based catalysts on the market still need to be further improved in terms of anti-coking performance, thermal stability, and catalytic efficiency. Therefore, developing a rare earth element-doped nickel-based catalyst with high activity, long life, and excellent anti-coking performance has important practical significance and market prospects. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the purpose of the present invention is to provide a rare earth element-doped nickel-based catalyst and a preparation method thereof. This catalyst has high catalytic activity, excellent thermal stability, good anti-coking performance, promotes the tar cracking reaction under high-temperature conditions in biomass gasifiers, and reduces the occurrence of coking phenomena.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0006] A rare earth element-doped nickel-based catalyst, comprising by weight percentage:

[0007] Ni: 20% - 25%; Al2O3: 65% - 70%; MgO: 3% - 5%; SiO2: 2% - 4%; rare earth elements: 2% - 5%.

[0008] Among the rare earth elements, Ce: 60% - 95%, and the rest are La, Nd, Y or Zr.

[0009] Among the rare earth elements, La: 3% - 15%, Zr: 0.5% - 5%, and the total amount of La and Zr does not exceed 15% of the total amount of rare earth elements.

[0010] Among the rare earth elements, when La and Zr are added simultaneously, the mass ratio of La:Zr is (2:1) - (5:1).

[0011] The weight content of rare earth is 4% - 5%; among rare earth elements, the weight ratio of Nd:Y:Ce is 5:3:12.

[0012] The nickel-based catalyst has a porous hierarchical pore structure, including micropores and mesopores, and nickel and rare earth active components are uniformly distributed on the surface of the carrier; the specific surface area of the porous hierarchical pore structure is 150 - 250 m 2 / g, and the pore volume is 0.4 - 0.6 cm 3 / g.

[0013] The types and contents of rare earth elements selected in the catalyst can endow the catalyst with higher redox ability, significantly improve the adsorption and activation ability of the catalyst for hydrocarbon substances, and exhibit excellent catalytic performance under high-temperature conditions:

[0014] Ce: As the main rare earth element, with variable valence states (Ce 3+ / Ce 4+ ), it can enhance the redox ability of the catalyst, promote the cracking of long-chain hydrocarbons in tar, and at the same time inhibit carbon deposition formation.

[0015] La: It can adjust the surface acidity of the carrier, improve the thermal stability, and prevent nickel particles from sintering at high temperatures.

[0016] Zr: By forming a stable Zr-O-Al structure, it enhances the mechanical strength of the carrier and delays the collapse of the pore structure.

[0017] Nd: It can form a stable complex with the carrier Al2O3, inhibit the high-temperature sintering of the active component (Ni), enhance the adsorption ability for oxygen-containing intermediates, improve the tar cracking efficiency, and reduce carbon deposition generation.

[0018] Y: It forms a solid solution with the carrier Al2O3, improves the high-temperature deformation resistance of the carrier. Promote the uniform dispersion of Ni nanoparticles on the surface of the carrier and enhance the catalytic activity.

[0019] A preparation method of a nickel-based catalyst doped with rare earth elements includes the following steps:

[0020] 1) Prepare the carrier precursor: Mix Al2O3, MgO, and SiO2, then add a binder and a dispersant and stir to mix, then add deionized water, with a solid-liquid ratio of 1:3, place it in a ball mill for ball milling, and obtain the carrier precursor after drying and sieving; the addition amount of the binder is 2% - 3% of the total mass, and the addition amount of the dispersant is 2% of the total mass;

[0021] 2) Loading of active components: Mix nickel nitrate solution and cerium nitrate solution according to the Ni to Ce ratio content, add the carrier precursor, stir, and then perform spray drying; the feeding rate of spray drying is 10 - 15 mL / min, the inlet temperature is 220 ± 10 °C, and the outlet temperature is 100 ± 10 °C to obtain a microspherical loaded precursor with a particle size of 20 - 30 μm;

[0022] 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere, the calcination temperature is 600 - 800 °C, and the calcination time is 3 - 5 h;

[0023] This calcination temperature can promote the interaction between components and the carrier for the nickel-based catalyst, contribute to the formation of a metal oxide or composite oxide structure with high stability, and at the same time improve the high-temperature thermal stability of the catalyst under long-term conditions. A too low or too high calcination temperature will affect the activity and stability of the catalyst, reduce the specific surface area, cause the loss of active components, reduce the dispersion degree, and increase the risk of carbon deposition. Therefore, selecting a temperature range of 600 - 800 °C can maximize the performance of the nickel-based catalyst.

[0024] 4) Reduction activation: The calcined sample is subjected to reduction treatment in a hydrogen atmosphere, the reduction temperature is 400 - 600 °C, and the reduction time is 2 - 4 h;

[0025] 5) Purge and passivate for 3 - 5 h under an inert atmosphere, and then cool naturally to obtain the final nickel-based catalyst doped with rare earth elements.

[0026] In step 3), when La, Zr or Nd, Y is selected to be added in the rare earth elements, the calcination temperature is 700 °C - 750 °C.

[0027] The binder described above is polyvinyl alcohol or carboxymethyl cellulose; the dispersant is polyethylene glycol.

[0028] In step 1), the ball milling time is 4 - 6 h, the slurry is dried at 90 - 100 °C for 9 - 12 hours to form a shape, and then sieved to obtain a carrier precursor powder with a mesh size of 150 - 200.

[0029] In step 2), the stirring rate is 300 rpm / h, and the stirring time is 4 - 6 h to ensure uniform adsorption of active components.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The catalyst of the present invention increases the specific surface area, broadens the applicable temperature range, has high catalytic activity, excellent thermal stability, good anti-coking performance and a long service life, and is particularly suitable for the tar cracking reaction under the high-temperature conditions of a biomass gasifier. The catalyst of the present invention has the following advantages:

[0032] 1. High catalytic activity: By doping rare earth elements, the redox ability of the catalyst is improved, significantly enhancing the adsorption and activation ability of the catalyst for hydrocarbons, and showing excellent catalytic performance under high-temperature conditions.

[0033] 2. Excellent thermal stability: Introducing rare earth elements can effectively inhibit the sintering and growth of nickel particles, significantly improving the thermal stability of the catalyst under high-temperature conditions.

[0034] 3. Good anti-coking performance: The porous hierarchical pore structure design and nanoparticle dispersion technology reduce the adsorption and deposition of large-molecule hydrocarbons on the catalyst surface, significantly reducing the risk of carbon deposition (coking).

[0035] 4. Long service life: Due to its excellent thermal stability and anti-coking performance, this catalyst has a long service life in industrial applications, reducing the replacement frequency and operating costs. Brief Description of the Drawings

[0036] Figure 1 is the SEM morphology diagram of the nickel-based catalyst doped with rare earth elements.

[0037] Figure 2 is the catalytic activity curve diagram of the nickel-based catalyst doped with rare earth elements at different temperatures. Detailed Embodiments

[0038] The present invention will be described in detail below in conjunction with the drawings of the specification, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] See Figure 1 , the nickel-based catalyst doped with rare earth elements, by weight percentage includes:

[0041] Ni: 20%; Ce: 2%; Al2O3: 70%; MgO: 4%; SiO2: 4%.

[0042] The preparation method of the nickel-based catalyst doped with rare earth elements includes the following steps:

[0043] 1) Prepare the carrier precursor: Mix Al2O3, MgO, and SiO2 according to the above weight percentages, then add polyvinyl alcohol and polyethylene glycol, stir, ball mill, and dry to obtain a carrier precursor powder of 150 - 200 mesh; wherein, the addition amount of polyvinyl alcohol is 2.5% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2, and the addition amount of polyethylene glycol is 2% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2.

[0044] 2) Active component loading: Mix the nickel nitrate solution and the cerium nitrate solution according to the Ni to Ce ratio content, add the carrier precursor, with a stirring rate of 300 rpm / h for 4 h to ensure uniform adsorption of the active components. After uniformity, perform spray drying with a feed rate of 10 - 13 mL / min, an inlet temperature of 220 °C, and an outlet temperature of 100 °C to obtain microspherical loaded precursor particles with a particle size of 20 - 25 μm.

[0045] 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere at a calcination temperature of 600 °C for 3.5 h, with a specific surface area of 180 m 2 / g.

[0046] 4) Reduction activation: The calcined sample is subjected to reduction treatment in a hydrogen atmosphere at a reduction temperature of 500 °C for 3 h.

[0047] 5) Purge and passivate in a nitrogen atmosphere for 3 h and then cool naturally. After cooling, screen through 100 meshes to remove agglomerated particles to obtain the final nickel-based catalyst doped with rare earth elements. The nickel-based catalyst has a specific surface area of 180 m 2 / g and a pore volume of 0.5 cm 3 / g.

[0048] Finally, a nickel-based catalyst doped with Ce is obtained. After testing, the conversion rate of this catalyst for tar cracking reaches over 90% at 900 °C, and its anti-coking performance is significantly better than that of traditional nickel-based catalysts.

[0049] Example 2:

[0050] The nickel-based catalyst doped with rare earth elements includes, by weight percentage:

[0051] Ni: 25%; Ce: 5%; Al2O3: 65%; MgO: 3%; SiO2: 2%.

[0052] Preparation of the nickel-based catalyst doped with rare earth elements:

[0053] 1) Preparation of the carrier precursor: Mix Al2O3, MgO, and SiO2 according to the above weight percentages, and then add polyvinyl alcohol and polyethylene glycol. After stirring, ball milling, and drying, obtain carrier precursor powder with 150 - 200 meshes and a particle size of about 75 μm. Among them, the addition amount of polyvinyl alcohol is 3% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2, and the addition amount of polyethylene glycol is 2% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2.

[0054] 2) Active component loading: Mix the nickel nitrate solution and the cerium nitrate solution according to the Ni to Ce ratio content, add the carrier precursor, with a stirring rate of 300 rpm / h for 5 hours to ensure uniform adsorption of the active components. After uniformity, perform spray drying with a feed rate of 12 - 14 mL / min, an inlet temperature of 220 °C, and an outlet temperature of 100 °C to obtain microspherical loaded precursor particles with a particle size of 20 - 25 μm.

[0055] 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere at a calcination temperature of 650 °C for 4 h, with a specific surface area of 190 m 2 / g;

[0056] 4) Reduction activation: The calcined sample is subjected to reduction treatment in a hydrogen atmosphere at a reduction temperature of 500 °C for 3 h;

[0057] 5) Purge and passivate in a nitrogen atmosphere for 3 hours and then cool naturally. After cooling, screen through a 100 - mesh sieve to remove agglomerated particles to obtain the final nickel - based catalyst doped with rare earth elements. The specific surface area of the nickel - based catalyst is 190 m 2 / g, and the pore volume is 0.5 cm 3 / g.

[0058] Operate according to the steps of the preparation method, and finally obtain a nickel - based catalyst doped with cerium (Ce). See Figure 2 , after testing, after continuous operation at 900 °C for 50 hours, the catalyst activity only decreases by 10%, showing excellent thermal stability and anti - coking performance.

[0059] Example 3

[0060] The nickel - based catalyst doped with rare earth elements includes, by weight percentage:

[0061] Ni: 25%; Ce: 4%; Al2O3: 65%; MgO: 3%; SiO2: 3%.

[0062] Prepare the nickel - based catalyst doped with rare earth elements according to the preparation method of Example 2, and finally obtain a nickel - based catalyst doped with cerium (Ce). After testing, after operating at 800 °C for 50 hours, there is no obvious carbon deposition on the catalyst surface, and the anti - coking performance is excellent.

[0063] Example 4:

[0064] See Figure 1 , on the basis of Example 2, optimize the rare earth elements. The rare earth elements are selected as a mixture of Ce, La, and Zr, and the mass ratio of the three is Ce:La:Zr = 85%:10%:5%. Test its carbon deposition amount at 900 °C through TPO analysis. The results show that the carbon deposition amount is 30% lower than that of single Ce doping, and the tar conversion rate reaches 93%.

[0065] Preparation method of a nickel-based catalyst doped with the above rare earth elements, comprising the following steps:

[0066] 1) Preparation of a carrier precursor: Mix Al2O3, MgO, and SiO2 according to the above weight percentages, then add polyvinyl alcohol and polyethylene glycol, stir, ball mill, and dry to obtain a carrier precursor powder with a mesh size of 150 - 200 and a particle size of approximately 75 μm. Among them, the addition amount of polyvinyl alcohol is 3% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2, and the addition amount of polyethylene glycol is 2% of the total mass of Ni, Ce, Al2O3, MgO, and SiO2.

[0067] 2) Loading of active components: Mix a nickel nitrate solution, a cerium nitrate solution, a lanthanum nitrate solution, and a zirconium oxynitrate solution according to the proportional content, add the carrier precursor, stir at a rate of 300 rpm / h for 5 hours to ensure uniform adsorption of the active components. After uniformity, perform spray drying with a feed rate of 10 - 15 mL / min, an inlet temperature of 220 °C, and an outlet temperature of 100 °C to obtain a microspherical loaded precursor with a particle size of 22 μm.

[0068] 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere at a calcination temperature of 750 °C for 4 hours, and the specific surface area is 180 m 2 / g.

[0069] 4) Reduction activation: Perform reduction treatment on the calcined sample in a hydrogen atmosphere at a reduction temperature of 550 °C for 4 hours;

[0070] 5) Purge and passivate for 3 hours in an inert gas (nitrogen) environment and then cool naturally. After cooling, screen through 100 meshes to remove agglomerated particles to obtain the final nickel-based catalyst doped with rare earth elements. The specific surface area of the nickel-based catalyst is 190 m 2 / g, and the pore volume is 0.55 cm 3 / g.

[0071] Example 5:

[0072] Based on Example 2, select a mixture of Ce, La, and Zr as the rare earth elements, with a La:Zr mass ratio of 3:1 (Ce:La:Zr = 92%:6%:2%), and prepare a nickel-based catalyst according to the preparation method of Example 4. The compressive strength of the catalyst is increased by 20%, and the activity only decreases by 8% after continuous operation for 100 hours.

[0073] Example 6:

[0074] On the basis of Example 3, a mixture of Ce and Y is selected as the rare earth elements, and the mass percentages of Nd, Y, and Ce are doped in accordance with 25%:15%:60%. Through actual operation, it is found that the tar conversion rate is further improved, reaching as high as 97%, and the carbon deposition amount is reduced. The catalyst is stable and balanced in terms of activity, structural stability, and anti-carbon deposition performance.

[0075] A preparation method of a nickel-based catalyst doped with the above rare earth elements includes the following steps:

[0076] 1) Prepare a carrier precursor: Mix Al2O3, MgO, and SiO2 according to the above weight percentages, then add polyvinyl alcohol and polyethylene glycol, stir and ball mill for 6 hours, dry at 95°C for 12 hours, and then screen to obtain a carrier precursor powder with a mesh size of 150-200 and a particle size of about 75 μm.

[0077] 2) Load the active components: Mix nickel nitrate solution with neodymium nitrate solution, yttrium nitrate solution, and cerium nitrate solution according to a mass ratio of 25:1:0.6:2.4. Add the carrier precursor, with a stirring rate of 300 rpm / h and a time of 6 hours to ensure uniform adsorption of the active components. After uniformity, perform spray drying, with a feed rate of 10-15 mL / min, an inlet temperature of 220°C, and an outlet temperature of 100°C, to obtain a microspherical loaded precursor with a particle size of 22 μm.

[0078] 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere, with a calcination temperature of 750°C and a calcination time of 4 h.

[0079] 4) Reduction activation: The calcined sample is subjected to reduction treatment in a hydrogen atmosphere, with a reduction temperature of 500°C and a reduction time of 3 h.

[0080] 5) Purge and passivate in an inert gas (nitrogen) environment for 3 hours and then cool naturally. After cooling, the final nickel-based catalyst doped with rare earth elements is obtained. The specific surface area of the nickel-based catalyst is 220 m 2 / g, and the pore volume is 0.6 cm 3 / g.

[0081] See Figure 2 , after testing, after continuous operation at 900°C for 50 hours, the catalyst activity only decreases by 10%, showing excellent thermal stability and anti-coking performance.

[0082] Through reasonable component ratios and advanced structural designs, the present invention significantly improves the catalytic activity, thermal stability, and anti-coking performance of the catalyst. The catalyst has broad application prospects in the in-situ high-temperature cracking reaction of tar in biomass gasifiers, and can effectively improve the efficiency and economy of industrial processes. The reaction temperature is 700°C - 1000°C, and after the catalyst operates continuously for 50 hours, the activity decrease does not exceed 10%, and the tar removal rate is as high as over 99%.

Claims

1. A nickel-based catalyst doped with rare earth elements, characterized in that, Comprising by weight percentage: Ni: 20% - 25%; Al2O3: 65% - 70%; MgO: 3% - 5%; SiO2: 2% - 4%; rare earth elements: 2% - 5%.

2. The nickel-based catalyst doped with rare earth elements according to claim 1, wherein Among the said rare earth elements, Ce: 60% - 95%, and the rest are La, Nd, Y or Zr.

3. The nickel-based catalyst doped with rare earth elements according to claim 2, characterized in that, Among the said rare earth elements, La: 3% - 15%, Zr: 0.5% - 5%, and the total amount of La and Zr does not exceed 15% of the total amount of rare earth elements; When La and Zr are added simultaneously, the mass ratio of La:Zr is (2:1) - (5:1).

4. The nickel-based catalyst doped with rare earth elements according to claim 2, characterized in that, The weight content of the said rare earth is 4% - 5%; among the rare earth elements, by weight ratio, Nd:Y:Ce is 5:3:

12.

5. A nickel-based catalyst doped with rare earth elements according to claim 1, characterized in that, The described nickel-based catalyst has a porous hierarchical pore structure, including micropores and mesopores, and nickel and rare earth active components are uniformly distributed on the surface of the carrier; the specific surface area of the porous hierarchical pore structure is 150-250 m 2 / g, and the pore volume is 0.4-0.6 cm 3 / g.

6. The preparation method of a nickel-based catalyst doped with rare earth elements according to claim 1 or 2, characterized in that, Including the following steps: 1) Preparation of the carrier precursor: Mix Al2O3, MgO, and SiO2, then add a binder and a dispersant and stir to mix, then add deionized water with a solid-liquid ratio of 1:3, place it in a ball mill for ball milling, and obtain the carrier precursor after drying and sieving; the addition amount of the said binder is 2% - 3% of the total mass, and the addition amount of the dispersant is 2% of the total mass; 2) Loading of the active component: Mix the nickel nitrate solution and the cerium nitrate solution according to the proportion content of Ni and Ce, add the carrier precursor, stir, and then carry out spray drying; the feeding rate of spray drying is 10 - 15 mL / min, the inlet temperature is 220 ± 10 °C, the outlet temperature is 100 ± 10 °C, and obtain a microspherical loaded precursor with a particle size of 20 - 30 μm; 3) Calcination treatment: The sample after spray drying is calcined in an air atmosphere, the calcination temperature is 600 - 800 °C, and the calcination time is 3 - 5 h; 4) Reduction activation: The sample after calcination is subjected to reduction treatment in a hydrogen atmosphere, the reduction temperature is 400 - 600 °C, and the reduction time is 2 - 4 h; 5) Purge and passivate for 3 - 5 h in an inert atmosphere, and cool naturally to obtain the final nickel-based catalyst doped with rare earth elements.

7. The preparation method of a nickel-based catalyst doped with rare earth elements according to claim 6, characterized in that, In step 3), when La, Zr or Nd, Y is selected to be added among the rare earth elements, the calcination temperature is 700 °C - 750 °C.

8. The preparation method of a nickel-based catalyst doped with rare earth elements according to claim 6, characterized in that, The said binder is polyvinyl alcohol or carboxymethyl cellulose; the dispersant is polyethylene glycol.

9. The preparation method of a nickel-based catalyst doped with rare earth elements according to claim 6, characterized in that, In step 1), the ball milling time is 4 - 6 h, the slurry is dried at 90 - 100 °C for 9 - 12 hours to form a shape, and sieved to obtain a carrier precursor powder of 150 - 200 mesh.

10. The preparation method of a nickel-based catalyst doped with rare earth elements according to claim 6, characterized in that, In step 2), the stirring rate is 300 rpm / h, and the stirring time is 4 - 6 h to ensure uniform adsorption of the active component.

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