Effect of CeO2 loading on catalytic performance of Co/SiO2 for F-T synthesis reaction

A series of Co-CeO2/SiO2 catalyst samples with different CeO2 contents were prepared and characterized, and their catalytic performance for F-T synthe sis reaction was measured. It was found that the addition of ceria not only enhanced the catalytic activity and the selectivity for C5+ hydrocarbons, but also favored the formation of middle distillates. The reaction temperat ure, calcination temperature and CeO2 loading have considerable effects on the catalytic performance of the catalyst. The optimized catalyst samples, with w(Co) = 10% and n (Ce)/n (Co) = 0.2 similar to 0.3, gave 83% similar t o 86% of C5+ yield under the reaction conditions of GHSV = 500 h(-1), T = 4 83 K and p = 1.2 MPa. In order to explain the experimental results, it is p resumed that there are three different kinds of CO species, i.e. weakly, mo derately and strongly chemisorbed CO, on the cobalt-based catalysts. The st rongly chemisorbed CO species easily leads to the formation of CO2 and coke deposit. The moderately chemisorbed CO species are active for F-T synthesi s reaction. The CeO2 promoter can play the role to hinder the fort-nation o f strongly chemisorbed CO species and favor the formation of moderately che misorbed CO species.