Nickel-based catalyst for efficient methanation reaction as well as preparation method and application of nickel-based catalyst

Abstract

The invention aims to provide a nickel-based catalyst for efficient methanation reaction as well as a preparation method and application thereof, and belongs to the technical field of catalysts, the nickel-based catalyst is prepared and synthesized by using a simple and rapid ultrasonic-assisted coprecipitation method, regulating alkaline sites through an alkaline earth metal aid MgO and introducing a rare earth aid Sm2O3 for modification, and the nickel-based catalyst is named as Ni / MgO-Sm2O3-CeO2 / Al2O3. The catalyst is applied to methanation reaction under the condition that coke oven gas supplements carbon dioxide, and shows good catalytic performance. The catalyst is simple and convenient in preparation method, short in synthesis period, excellent in catalyst performance and suitable for methanation industrial-grade application under the condition that coke oven gas supplements carbon dioxide feeding.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a nickel-based catalyst for efficient methanation reactions, its preparation method, and its application. Background Technology

[0002] CO and CO2 gas methanation technologies have important applications in energy production, environmental protection, and chemical manufacturing. Continuous development and optimization of these technologies help improve energy efficiency, reduce greenhouse gas emissions, and promote sustainable development. Both CO and CO2 methanation reactions are gas molecular weight reduction reactions and are strongly exothermic. Low temperature and high pressure conditions are favorable for the reactions, but currently, problems exist such as slow reaction rates at excessively low temperatures and high production costs at excessively high pressures. Therefore, developing catalysts for efficient methanation under low temperature and low pressure conditions is crucial for this reaction process. Furthermore, the reaction process involving mixed CO and CO2 gas components is even more challenging, as the two reactions mutually inhibit each other, hindering the reaction process. Therefore, solving the problem of efficient methanation under mixed gas component feed conditions is also a major research challenge.

[0003] The methanation reaction of CO and CO2 mainly involves the reaction of CO, CO2, and H2 in ratios of 1:3 and 1:4, respectively, to produce CH4 and H2O. Currently, the catalysts required for this reaction can be divided into noble metal catalysts and non-noble metal catalysts. Noble metal catalysts, such as Pd, Pt, Rh, and Ir-based catalysts, have their active components dispersed as nano-sized noble metal particles on a support. This gives them advantages such as high activity and selectivity at low temperatures, as well as strong resistance to poisoning, carbon deposition, and sintering, making them suitable for various complex reaction environments. However, the scarcity of noble metal resources and high cost limit the use and development of this type of catalyst. Current research on non-noble metal catalysts, such as Ni, Co, and Fe-based catalysts, not only offers relatively high catalytic performance but also boasts abundant metal resources and low cost and stability. However, non-noble metal catalysts exhibit poor low-temperature activity and weak resistance to carbon deposition and sintering, leading to reduced catalyst stability and shortened lifespan. The main research issue at present is how to improve and optimize non-precious metal catalysts to enhance their low-temperature methanation performance, while improving their resistance to carbon deposition and sintering, thereby extending their service life. Summary of the Invention

[0004] The purpose of this invention is to provide a nickel-based catalyst for efficient methanation reaction under coke oven gas supplemented with carbon dioxide, its preparation method and application. Compared with traditional nickel-based catalysts, this invention, with the co-modification of alkaline earth metals and rare earth metals, uses a simple and rapid preparation method and achieves the industrialization goal of high conversion rate, high selectivity and high stability under coke oven gas supplemented with carbon dioxide and low temperature and low pressure conditions.

[0005] The present invention adopts the following technical solution: A highly efficient nickel-based catalyst for methanation reaction, denoted as Ni / MgO-Sm2O3-CeO2 / Al2O3, wherein the catalyst uses metallic Ni as the active component supported on an Al2O3 support, and MgO, Sm2O3, and CeO2 are used as metal oxide promoters for doping; the catalyst exhibits an amorphous structural morphology.

[0006] Furthermore, in the nickel-based catalyst, the mass percentage of Ni is 38-42%; the doping amount of MgO is 6-8%; the doping amount of Sm2O3 is 6-8%; the doping amount of CeO2 is 14-16%; and the doping amount of Al2O3 is 30-32%.

[0007] A method for preparing a highly efficient nickel-based catalyst for methanation reactions includes the following steps: S1. Weigh out Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, Sm(NO3)3·6H2O, Ce(NO3)3·6H2O and Al(NO3)3·9H2O respectively according to the proportions, and dissolve them together in 1000mL of deionized water to prepare a nitrate metal solution. S2. Dissolve Na2CO3 in deionized water, and slowly add the metal nitrate solution dropwise to the Na2CO3 solution while stirring continuously to obtain a mixed solution; S3. Adjust the pH of the mixed solution with 1.5 mol / L NaOH solution until the metal is completely precipitated to obtain a mixture; S4. The resulting mixture is stirred, sonicated, washed, and dried, and then calcined in a muffle furnace to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3 catalyst precursor. S5. After reducing the catalyst precursor in a hydrogen atmosphere, a Ni / MgO-Sm2O3-CeO2 / Al2O3 catalyst is obtained.

[0008] Furthermore, the molar amount of Na2CO3 in S2 is 1.875 mol, and the amount of deionized water used is 2500 mL.

[0009] Furthermore, the pH value adjustment range described in S3 is 10.5-11.5.

[0010] Furthermore, the stirring time in S4 is 30-60 min; the ultrasonic time is 30-60 min; the drying temperature is 80-120℃; and the drying time is 12-24 h.

[0011] Furthermore, the calcination temperature in the muffle furnace described in S4 is 500℃, and the calcination time is 2-4 hours.

[0012] Furthermore, the reduction temperature described in S5 is 550℃, and the reduction time is 2-3 hours.

[0013] The nickel-based catalyst is used in a highly efficient methanation reaction under conditions of coke oven gas supplemented with carbon dioxide feed.

[0014] This invention uses Al2O3 as a metal oxide support and MgO, Sm2O3, and CeO2 as metal oxide promoters to form a Ni / MgO-Sm2O3-CeO2 / Al2O3 supported catalyst. It utilizes the excellent dispersibility and large specific surface area of ​​the Al2O3 support; the alkaline earth metal properties of MgO provide more basic sites for the catalyst; and the rare earth metal Sm2O3 enters the CeO2 lattice to expose more oxygen vacancies, thereby greatly improving the catalyst performance.

[0015] The raw materials for the nickel-based catalyst of this invention are various non-precious metal nitrate hydrates, which are inexpensive and readily available. The preparation method is simple and feasible, and it is easy to achieve industrialization goals.

[0016] The nickel-based catalyst described in this invention operates under favorable catalytic conditions (low temperature 275°C, low pressure 15 bar), achieving highly efficient methane conversion with supplemental carbon dioxide feed from coke oven gas. CO conversion can reach 100%, CO2 conversion can reach 80%, and the space-time yield of CH4 can reach 461 mmol g. -1 h -1 The CH4 selectivity can reach about 90%, and the CH4 content in the exported product gas can reach 83.56%, which has broad prospects for industrial application.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The catalyst described in this invention solves the problems of poor activity, low selectivity, and poor stability of traditional nickel-based catalysts under low temperature and low pressure conditions. It has excellent low temperature and low pressure performance and is suitable for the hydrogenation reaction of CO and CO2. The preparation method is simple and easy to scale up for industrial production.

[0018] 2. The catalyst described in this invention solves the problems of poor activity and easy deactivation of traditional nickel-based catalysts under mixed gas reaction conditions. Under reaction conditions of 275℃ and 15 bar, it achieves excellent performance with coke oven gas supplemented with carbon dioxide mixed components as feed, achieving a CO conversion rate of up to 100%, a CO2 conversion rate of up to 80%, and a CH4 space-time yield of up to 461 mmol g. -1 h -1 The CH4 selectivity can reach about 90%, the CH4 content in the exported product gas can reach 83.56%, and it can operate stably for more than 200 hours without being deactivated. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the nickel-based catalyst described in Example 1 of this invention.

[0020] Figure 2 This is a TEM image of the nickel-based catalyst described in Example 1 of the present invention.

[0021] Figure 3 The graphs show the CO and CO2 methane conversion activity test results of the catalysts described in Example 1 and Comparative Examples 1-4 of this invention.

[0022] Figure 4 The figures show the stability test results of CO and CO2 methane conversion of the catalysts described in Example 1 and Comparative Examples 1-4 of this invention.

[0023] Figure 5 This is a performance test diagram of Embodiment 1 of the present invention applied to the condition of supplementing carbon dioxide feed into coke oven gas. Detailed Implementation

[0024] The following embodiments are merely preferred technical solutions of the present invention and are not intended to limit the present invention in any way. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0025] Example 1 A method for preparing a Ni / MgO-Sm2O3-CeO2 / Al2O3 supported catalyst includes the following steps: S1: Weigh a certain amount of Ni(NO3)2·6H2O (0.511 mol), Mg(NO3)2·6H2O (0.128 mol), Sm(NO3)3·6H2O (0.016 mol), Ce(NO3)3·6H2O (0.065 mol) and Al(NO3)3·9H2O (0.225 mol) reagents and dissolve them in 1000 mL of deionized water to prepare a nitrate solution; S2: Weigh 1.875 mol Na2CO3 reagent and dissolve it in 2500 mL of deionized water to prepare a precipitant solution; S3: Slowly add the metal nitrate solution dropwise to the above Na2CO3 solution while stirring continuously, and then adjust the pH value with 1.5 mol / L NaOH solution until the metal is completely precipitated; S4: The resulting mixture was stirred (stirring time was 40 min), sonicated (sonication time was 40 min), washed, and dried (drying temperature was 100℃, drying time was 15 h), and then calcined in a muffle furnace at 500 ℃ to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3. S5: Reduction was carried out at 550 °C in a hydrogen atmosphere for 2 hours to obtain a nickel-based catalyst, denoted as Ni / MgO-Sm2O3-CeO2 / Al2O3.

[0026] The XRD pattern of the nickel-based catalyst is shown below. Figure 1 As shown, by Figure 1 It can be seen that the XRD patterns of the reduced catalyst all show characteristic diffraction peaks belonging to metallic Ni at 2θ = 44.5° (111), 51.8° (200), and 76.4° (220), indicating that NiO was reduced to metallic Ni during the reduction process.

[0027] TEM image of the nickel-based catalyst is shown below. Figure 2 As shown, by Figure 2 It can be seen that the Ni nanoparticles in the catalyst maintain a small particle size (4.99 ± 0.09 nm), and the lattice stripes belonging to the Ni (111) crystal plane can also be clearly observed, indicating that the reduced Ni nanoparticles are uniformly dispersed in the catalyst system.

[0028] Comparative Example 1 The only difference between this comparative example and Example 1 is that Sm2O3 is not added; all other conditions and parameters are exactly the same as in Example 1.

[0029] Comparative Example 2 The only difference between this comparative example and Example 1 is that Sm2O3 is replaced with another rare earth additive, La2O3. All other conditions and parameters are exactly the same as in Example 1.

[0030] Comparative Example 3 The only difference between this comparative example and Example 1 is that Sm2O3 is replaced with another rare earth additive, Pr2O3. All other conditions and parameters are exactly the same as in Example 1.

[0031] Comparative Example 4 The difference between this comparative example and Example 1 is that the catalyst used is an industrial methanation catalyst.

[0032] Performance testing: The CO and CO2 performance of the catalysts described in Example 1 and Comparative Examples 1-4 were tested under the following conditions: 100 mg catalyst; gas feed ratio of CO / H2 = 1 / 3, CO2 / H2 = 1 / 4; gas feed space velocity of 40,000 ml / h. -1 g -1 The reaction temperature was 225-300℃, and the reaction pressure was 15 bar. Test results are as follows: Figure 3 , Figure 4 As shown.

[0033] As can be seen from the attached figures, the catalyst described in Example 1 achieved excellent performance in the conversion of CO and CO2 to methane under reaction conditions of 275°C and 15 bar. The conversion rate of CO can reach 100%, and the selectivity of CH4 can reach over 97%; the conversion rate of CO2 can reach 95%, and the selectivity of CH4 can reach over 99%, and it can operate stably for over 100 hours without deactivation.

[0034] As can be seen from the comparison between Example 1 and Comparative Examples 1-4, the introduction of rare earth additives significantly improves the low-temperature and low-pressure methanation performance of the catalyst, and the introduction of Sm2O3 has the most significant performance improvement.

[0035] The performance of the catalyst described in Example 1 was tested under coke oven gas supplemented with carbon dioxide feed conditions. The reaction conditions were: 100 mg catalyst; gas feed ratios of 5.94% CO, 11.86% CO2, 56.54% H2, 21.93% CH4, 3.85% N2 and 6.56% CO, 2.03% CO2, 62.32% H2, 24.23% CH4, 4.56% N2 (CO2 supplementation was 10% of the total feed); gas feed space velocity was 40,000 ml / h. -1 g -1 The reaction temperature was 275℃, and the reaction pressure was 15 bar. The test results are as follows: Figure 5 As shown.

[0036] As can be seen from the accompanying drawings, the catalyst described in this invention achieves excellent performance under reaction conditions of 275℃ and 15 bar, with a CO conversion rate of up to 100%, a CO2 conversion rate of approximately 80%, and a CH4 space-time yield of 461 mmol g. -1 h -1 The CH4 selectivity can reach about 90%, the CH4 content in the exported product gas can reach 83.56%, and it can operate stably for more than 200 hours without being deactivated.

[0037] As shown in Example 1, the nickel-based catalyst of the present invention has excellent low-temperature and low-pressure methanation performance under coke oven gas supplemented with carbon dioxide. Moreover, the preparation method is simple and quick, low in cost, and easy to carry out large-scale industrial production. It can be applied to industrial-grade methanation production processes and has good industrial application prospects.

[0038] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A nickel-based catalyst for highly efficient methanation reactions, characterized in that: The catalyst is Ni / MgO-Sm2O3-CeO2 / Al2O3, in which metallic Ni is supported on an Al2O3 support, and MgO, Sm2O3 and CeO2 are doped as metal oxide promoters; the catalyst exhibits an amorphous structural morphology.

2. The nickel-based catalyst for a highly efficient methanation reaction according to claim 1, characterized in that: In the nickel-based catalyst, the mass percentage of Ni is 38-42%; the doping amount of MgO is 6-8%; the doping amount of Sm2O3 is 6-8%; the doping amount of CeO2 is 14-16%; and the doping amount of Al2O3 is 30-32%.

3. A method for preparing a nickel-based catalyst for a highly efficient methanation reaction as described in claim 1, characterized in that: Includes the following steps: S1. Weigh out Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, Sm(NO3)3·6H2O, Ce(NO3)3·6H2O and Al(NO3)3·9H2O respectively according to the proportions, and dissolve them together in 1000mL of deionized water to prepare a nitrate metal solution. S2. Dissolve Na2CO3 in deionized water, and slowly add the metal nitrate solution dropwise to the Na2CO3 solution while stirring continuously to obtain a mixed solution; S3. Adjust the pH of the mixed solution with 1.5 mol / L NaOH solution until the metal is completely precipitated to obtain a mixture; S4. The resulting mixture is stirred, sonicated, washed, and dried, and then calcined in a muffle furnace to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3 catalyst precursor. S5. After reducing the catalyst precursor in a hydrogen atmosphere, a Ni / MgO-Sm2O3-CeO2 / Al2O3 catalyst is obtained.

4. The method for preparing a highly efficient nickel-based catalyst for methanation reaction according to claim 3, characterized in that: The molar amount of Na2CO3 in S2 is 1.875 mol, and the amount of deionized water used is 2500 mL.

5. The method for preparing a highly efficient nickel-based catalyst for methanation reaction according to claim 3, characterized in that: The pH adjustment range described in S3 is 10.5-11.

5.

6. The method for preparing a highly efficient nickel-based catalyst for methanation reaction according to claim 3, characterized in that: The stirring time in S4 is 30-60 min; the ultrasonic time is 30-60 min; the drying temperature is 80-120℃; and the drying time is 12-24 h.

7. The method for preparing a highly efficient nickel-based catalyst for methanation reaction according to claim 3, characterized in that: The roasting temperature in the muffle furnace described in S4 is 500℃, and the roasting time is 2-4h.

8. The method for preparing a highly efficient nickel-based catalyst for methanation reaction according to claim 3, characterized in that: The reduction temperature described in S5 is 550℃, and the reduction time is 2-3 hours.

9. A nickel-based catalyst as described in claim 1 applied to a high-efficiency methanation reaction under coke oven gas supplemented with carbon dioxide feed.

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