(621bw) A Study on the Deactivation of Titania Based Cobalt Catalyst in Fischer-Tropsch Synthesis

Authors: 
Muleja, A., University of South Africa
Glasser, D., University of South Africa
Hildebrandt, D., University of South Africa
Yao, Y., University of South Africa
Liu, X., University of South Africa

Fischer-Tropsch Synthesis (FTS) is a process used for the production of synthetic fuels and other waxy products from feedstocks such as natural gas, coal and biomass, using a metal catalyst. The catalyst is crucial in FT processes and once the catalyst is deactivated there is a strong possibility that the activity and selectivity to the FT products will be affected. Most papers have reported the overall catalytic activity before, during and after deactivation. Only limited results have been published on the formation rate and selectivity to olefins and paraffins separately during catalyst deactivation. With the aim of understanding the effect of catalyst deactivation on the formation rate and selectivity of olefin and paraffin products separately during FTS, a group of experiments have been conducted using Co/TiO2 catalyst in a fixed bed reactor. A catalyst deactivation, “CO conversion dropped from 46% to 12%”, was observed during the time on stream (TOS) from 110 hours to 1100 hours. By comparing the product formation rates before, during and after deactivation, it was shown that the olefin formation rate was fairly constant while the paraffin formation rate dropped. This indicates the deactivation is mainly caused by the change in the paraffin formation rate. Currently, none of the published kinetic models can explain the phenomenon that the decay of the reaction rates of olefin and paraffin were not the same during the catalyst deactivation. More results, such as reactant reaction rate, product selectivity, Olefin/Paraffin ratios have been analysed, calculated and compared during the catalyst deactivation. The results could make a valuable contribution to the understanding of the mechanism of the product formation during FTS.