钍含量对Co/HMS催化剂结构和费托合成的影响

详细研究了钍含量对15% Co/HMS催化剂结构、费托合成CO转化率和烃分布的影响, 结果表明: 钍助剂的添加降低了催化剂的钴还原度, 并可使催化剂钴晶粒减小, 且存在钍物种对钴物种的覆盖; 钴晶粒的减小、较高钍含量时催化剂里钍物种对钴物种的覆盖和钴物种还原性能的降低, 使催化剂存在最优的钍含量, 此时催化剂表面暴露的金属钴原子最多, 较好地解释了钍含量达到1.5 wt%时, 催化剂CO转化率最高的实验现象. 烃分布研究表明: 反应温度较低时钍助剂将促进产物链的增长和高碳烃选择性的增加, 但反应温度较高时难以促进产物链的增长.

Fischer-Tropsch Synthesis and Characterization ofCo-Th/HMS Catalysts

Thorium promoted Co/HMS catalysts were prepared by the co-impregnation method, and the influence of thorium content on structure characterization of Co/HMS was investigated by XRD, TPR, H₂-TPD and TG characterization. It was found that cobalt reducibility was decreased due to the addition of thorium promoter, but kept constant with thorium content of 0.5～5 wt%, then the reduction of cobalt species would be more difficult even with more thorium content. Under the conditions of H₂/CO＝2.0, T＝473～493 K, p＝2.0 MPa, GHSV＝500 h^－1, CO conversion had a trend to increase with the increasing thorium relating to the increasing surface metal cobalt, and maximum CO conversion appeared at about 1.5 wt% of the thorium content, then CO conversion decreased gradually with further increasing thorium due to the coverage of cobalt species by thorium species, and the decreasing cobalt reducibility at high thorium content. The addition of thorium promoted the chain propagation at low reaction temperature, but had little effect on methane selectivity and light hydrocarbon.