Study on Fe-Al2O3 interaction over precipitated iron catalyst for Fischer-Tropsch synthesis

摘要

Two model spherical iron catalysts(100Fe/0Al2O3 and 100Fe/15Al2O3)with free Cu and K promoters were prepared by the combination of co-precipitation and spray drying method for the application of slurry Fischer-Tropsch synthesis(FTS).The effect of Fe-Al2O3 interaction on the reduction/carburization behavior in H2/CO/syngas,surface basicity and the change of phase structure were comparatively studied by means of H2 or CO temperature-programmed reduction(TPR),CO2 temperature-programmed desorption(TPD)and Mossbauer effect spectroscopy(MES).The results showed that the catalyst incorporated with Al2O3 exhibits a strong Fe-Al2O3 interaction,which obviously weakens the surface basicity,stabilizes the FeO phase and inhibits the reduction of iron catalyst in H2 or syngas.Furthermore,Fe-Al2O3 interaction also restrains the carburization of iron catalyst in CO or syngas.In slurry FTS process,it was found that the strong Fe-Al2O3 interaction decreases the FTS activity and suppresses the water gas shift(WGS)reaction,but can stabilize the active sites of iron catalyst and improve its run stability.Due to the strong Fe-Al2O3 interaction,the weak surface basicity on the catalyst incorporated with Al2O3 greatly decreases the selectivity of heavy hydrocarbon products.