锰助剂对F-T合成Co/Al_2O_3催化剂反应性能的影响

Effect of Manganese Promoter on the Performance of Co/Al_2O_3 Catalysts for Fischer-Tropsch Synthesis

采用程序升温和原位红外技术对锰改性Co/Al2O3催化剂进行了表征,并与CO加氢反应活性和选择性进行关联.结果表明,添加适量锰能够增加反应活性,提高C5+烃选择性,抑制甲烷及低碳烃的生成.XRD和FT-IR结果表明锰助剂的添加能够促进活性相的分散,促进桥式CO吸附位数的增加.H2-TPD表明锰的加入可增加低温吸附氢量,但吸附氢量随锰含量的增加而减少.钴基催化剂的费托合成反应性能可以用锰添加导致的CO吸附态物种的变化来解释.

The Mn-modified cobalt catalysts for Fischer-Tropsch(F-T) synthesis were characterized and tested by TPR, H-2-TPD, FT-IR, and CO hydrogenation. It was found that a suitable addition of manganese could improve the catalytic activity and C-5(+) selectivity and suppress the methane and C2-4 hydrocarbons. XRD and FT-IR results showed that the presence of Mn could improve the dispersion of active phases and favor the formation of bridged-type adsorbed CO. A small amount of Mn could increase the uptake of hydrogen, but excess of manganese might decrease the uptake of hydrogen. Such a shift of the reaction performances was related to the change of adsorbed CO species.