Effect of carbon support on Fischer-Tropsch synthesis activity and product distribution over Co-based catalysts

摘要

The ordered mesoporous carbon (CMK-3) was prepared using SBA-15 as template and sucrose as carbon source. Co catalysts supported on CNTs, CMK-3 and AC were prepared by incipient wetness. Their physical properties, morphologies and Fischer-Tropsch synthesis (FTS) activities were assessed. It was found that Co3O4 particles mainly dispersed inside the tubes (or pores) of Co/CNTs and Co/CMK-3 but outside the pores of Co/AC Co3O4 particle size depended closely on the support structure. After H2 reduction, the three catalysts had a similar cobalt particle size. The cobalt particle size of Co/CNTs was maintained well due to the special confinement effect of CNTs. CNTs were more stable at high temperature in H2 atmosphere than CMK-3 and AC and the reduction degree of Co/CNTs was higher than the other two catalysts. The good crystallized graphitic structure facilitated the electron transfer between the cobalt and CO molecules on Co/CNTs. So Co/CNTs had a better FTS performance than Co/CMK-3 and Co/AC catalysts. Carbon support structure influenced the C_(5+) selectivity, C_(5+) hydrocarbon distribution and CO turnover frequency. Furthermore, a positive relationship existed between C2-C4 olefin/paraffin ratio and C_(5+) selectivity. High olefin content and low space velocity benefit the heavy hydrocarbon production.