还原气氛对CoFe/SBA-15催化剂F-T反应性能的影响

考察了不同还原气氛处理CoFe/SBA-15催化剂对F-T反应性能的影响。结果表明,H2气氛下有利于六方钴的生成;催化剂的活性取决于钴含量,随着钴含量的增加,F-T反应中CO转化率增加,C5+选择性增加。随着铁含量的增加,催化剂表现了较高的CO2选择性。CO还原有利于立方钴的生成,导致催化活性相比H2还原的催化剂活性要低。同时CO还原容易产生积炭使催化剂的钴活性位被覆盖,导致甲烷选择性随着钴含量增加而升高。但碳化铁的生成有利于提高20Fe/SBA-15催化剂的活性,有利于低碳烃生成及C2~4烃烯烷比增加。

Effect of reduction on the performance of CoFe/SBA-15 catalysts for Fischer-Tropsch synthesis

CoFe/SBA-15 catalysts for Fischer-Tropsch synthesis were treated in different reduction atmosphere. It was found that the reduction in H₂ favored the formation of hexagonal cobalt, and then their catalytic activities were determined by the reduction of cobalt oxide. The presence of Fe₃O₄ promoted the water gas shift reaction, thus CO₂ selectivity increased with the increase of iron content. Compared with the catalysts reduced in H₂, the pretreatment in CO led to carbon deposition on cobalt active sites and lowered catalytic activities, but it facilitated the reduction of iron catalysts and led to the increase of olefin to paraffin ratio for C_2～4 hydrocarbons. Among them, 20Fe/SBA-15 catalyst showed high activity due to the formation of iron carbides.