Pretreating Co/SiO2 to generate highly active Fischer-Tropsch synthesis catalyst with low CH4 selectivity
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摘要: 采用TEM、HRTEM、XRD、XPS、H2-TPD、TG和TPR研究了三种预处理方法(DR、R、ROR)对Co/SiO2催化剂微观结构和费托合成(FTS)反应性能的影响。结果表明,经过预处理后,Co物种的特定形态发生变化,形成新的Co活性表面物种,Co粒子重新分散,Co物种易于再还原。不同方法预处理的Co/SiO2催化剂表现出不同的催化性能,经还原钝化处理的催化剂具有较高的FTS活性和C5+选择性。
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关键词:
- 预处理方法 /
- Co/SiO2催化剂 /
- 费托合成
Abstract: The effects of pretreatment methods (DR, R, ROR) on the microstructure of Co/SiO2 catalysts and the activity for Fischer-Tropsch synthesis (FTS) were investigated. The pretreated catalysts were characterized by TEM, HRTEM, XRD, XPS, H2-TPD, TG and TPR. The results showed that after the pretreatments, specific morphological of the Co species changed, forming new Co active surface species. The Co particles redispersed and the Co species was facile to be re-reduced. The Co/SiO2 catalysts pretreated by different method showed different catalytic performance. The catalyst treated by the reduction-passivation had higher activity and C5+ selectivity for FTS.-
Key words:
- pretreatment methods /
- Co/SiO2 catalyst /
- Fischer-Tropsch synthesis
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Table 1 Physico-chemical properties of the catalysts
Catalyst SBET/(m2·g−1) TPVa/(cm3·g−1) Pore diameter/nm Crystallite sizeb/nm Dispersionc/% Reductiond/% Co3O4/SiO2 153.6 0.6 16.7 16.3 5.9 78.2 Co/SiO2-DR 157.7 0.8 20.5 11.3 8.5 80.5 Co/SiO2-R 16.5 0.8 19.1 9.1 10.6 85.6 Co/SiO2-ROR 157.0 0.7 16.7 11.9 8.1 82.1 a: total pore volume; b: metallic cobalt crystallite size calculated from the formula: dnm = 96/D(%); c: cobalt metal dispersion from H2-TPD; d: calculated from TG results Table 2 Data from XPS characterization of the catalysts
Catalyst Co 2p3/2/eV Co 2p1/2/eV △E/eV n(Co/Si) ratio (theoretical value) ICo 2p/ISi 2p in the samples Co3O4/SiO2 780.5 795.5 15.0 0.19 0.08 Co/SiO2-DR 780.8 796.1 15.3 0.19 0.10 Co/SiO2-R 780.4 795.5 15.1 0.19 0.13 Co/SiO2-ROR 780.7 795.9 15.2 0.19 0.11 Table 3 Catalytic performance of the catalysts
Catalyst CO conv./% ${\rm{C} }_{5+}$ STY/(g·mL−1·h−1) Hydrocarbon distribution w/% C1 C2−4 ${\rm{C} }_{{5+}}$ C5−11 C12−18 ${\rm{C} }_{{18 +}}$ Co3O4/SiO2 20.6 0.02 22.4 6.5 71.1 15.9 27.5 27.7 Co/SiO2-DR 43.5 0.03 17.7 5.9 76.4 19.5 25.1 31.8 Co/SiO2-R 42.3 0.08 6.0 1.9 92.0 21.0 31.8 39.2 Co/SiO2-ROR 44.1 0.03 14.8 5.1 80.1 21.6 26.5 32.1 Reaction conditions: T = 483 K; p = 2.0 MPa; H2/CO = 2.0; GHSV = 1000 h−1 -
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