Fischer-Tropsch synthesis performance of cobalt-based catalysts supported on bimodal porous SiO2 with high specific surface area
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摘要: 载体的结构可以显著影响钴基费托合成催化剂的活性和产物选择性。大孔结构载体可以改善反应物和产物的传质情况,提升CO转化活性和C5+ 产物选择性;高比表面积载体有利于使负载的金属分散,提高催化剂的金属利用效率和稳定性。然而,要获得同时具备高比表面积和大孔结构特征的载体相对困难。本研究采用结构导向水解法,合成了一种比表面积达1103.2 m2/g的介孔(2.9 nm)-大孔(63.8 nm)双孔二氧化硅(BP-SiO2)载体,研究了其负载钴催化剂的费托合成反应性能。结果表明,相对规整介孔SBA-15分子筛负载的钴催化剂Co/SBA-15,210 ℃反应时,催化剂Co/BP-SiO2的CO转化率提高33.3%,CH4选择性降低30.1%,C5+ 选择性增加到80.0%,稳定性显著增强。Abstract: The structure of the supports can significantly affect the Fischer-Tropsch catalyst activity and selectivity. The porous structure can improve the mass transfer of reactants, enhance the CO conversion activity and C5+ product selectivity; the high specific surface area is beneficial to disperse the loaded metal, improve the catalyst metal utilization efficiency and catalyst stability. However, it is relatively difficult for supports to obtain high specific surface area and macropore structure characteristics simultaneously. A mesoporous (2.9 nm) -macroporous (63.8 nm) bi-porous silica (BP-SiO2) support with a high specific surface area of 1103.2 m2/g was synthesized by the structure-directed hydrolysis method, and its catalytic performance for Fischer-Tropsch synthesis was investigated. The results showed that compared to the Co/SBA-15 catalyst with equivalent mesopore diameter, the catalyst Co/BP-SiO2 showed CO conversion rate nearly increased by 33.3%, CH4 selectivity reduced by 30.1%, improved C5+ selectivity and stability.
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Key words:
- Fischer-Tropsch synthesis /
- bimodal pore /
- cobalt based catalyst
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表 1 催化剂及载体的物性参数、催化剂的Co粒径参数
Table 1 Textural properties of various catalysts and support, cobalt particle size of the catalysts
Sample SBET/
(m2·g−1)Average pore
size a /nmBJH pore
size /nmPore volume /
(cm3·g−1)Co particle size /nm XRD b TEM c H2-TPD d SBA-15 702.3 8.7 8.5 1.53 − − − Co/SBA-15 682.0 7.9 7.2 1.35 7.2 7.8 6.1 BP-SiO2 1103.2 11.4 2.9,63.8 3.15 − − − Co/BP-SiO2 723.6 8.9 2.7,40.2 1.61 5.8 6.0 5.3 a: Average pore size = 4 (pore volume/SBET), b: Particle size of Co3O4 was calculated by the Scherrer equation, Co metal particle size was calculated using the formulas DCo = 0.75 × DCo3O4, c: Average diameter of CoxOy crystallites obtained by TEM measurement, d: Co metal particle size was calculated by H2-TPD, Reduction at a temperature of 450 ℃ for 8 h, H2 chemisorption performance at 100 ℃ 表 2 固定床反应器上催化剂的费-托合成反应性能
Table 2 Evaluation of the Fischer-Tropsch reaction performance of the catalyst in a fixed-bed reactor a
Catalyst t/℃ CO initial
conversion /%CO steady
state conversion /%Activity lossb /% Product selectivity/mol% C1 C2 − C4 C5+ Co/BP-SiO2 210 37.7 33.8 10.3 10.6 9.4 80.0 230 59.1 54.9 7.1 14.7 11.2 74.1 Co/SBA-15 210 32.1 25.3 21.2 13.8 13.7 72.5 230 51.0 46.3 9.2 18.2 15.4 66.4 a: Reduction conditions: in pure hydrogen at 450 ℃, 0.1 MPa for 8 h; reaction conditions: H2/CO = 2, 210 and 230 ℃, 1.0 MPa, 4 L/(g·h), b: Activity loss= (CO initial conversion−CO steady state conversion)/CO initial conversion × 100% -
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