Fischer-Tropsch Synthesis over Ordered Mesoporous Carbon Supported Cobalt Catalysts: The Role of Amount of Carbon Precursor in Catalytic Performance

摘要

Ordered mesoporous carbon supported cobalt-based catalysts (Co/MC) were synthesized via incipient wetness impregnation with different amounts of furfuryl alcohol (FA) as carbon precursor. The characterizations of obtained Co/MC were subjected to N2 adsorption, XRD, XPS, TEM, H2-TPR, H2-TPD and H2-TPSR. The results indicate that the reducibility and dispersion of Co active species vary significantly due to the difference of FA amount. By simply tuning the FA content from 25 to 100 wt%, the reduction temperature of deriving metallic Co shifts gradually to lower. The catalytic performance of Co/MC was evaluated for Fischer-Tropsch (FT) synthesis. The observed FT activity exhibits a volcano-type curve with the amount of FA due to the effect of both reducibility and dispersion of active species. As the precursor concentration overweighs 50 wt%, the ability of CO to dissociate over the active surface and the selectivity to the C_(5+) products level off after experiencing an initial increase. Substantially, the catalysts with higher concentration of FA render the larger crystallites having an average size of more than 6 nm, which facilitates the CO hydrogenation by way of carbon chain propagation. It seems that the sample with FA content of 50 wt% is optimum in terms of FT activity and C_(5+) selectivity.