Selection of highly active and stable Co supported SiC catalyst for Fischer-Tropsch synthesis: Effect of the preparation method

Abstract

Co3O4 supported on SiC (Co3O4/SiC) composites were prepared by incipient wetness impregnation (IWI), sol-gel (SG) and precipitation (PCT) methods, respectively. Their physicochemical properties were investigated by XRD, low-temperature N2 adsorption, TEM, XPS, H2-TPR and H2-TPD, and the catalytic activity and selectivity of these composites after reduction (Co/SiC) were tested for Fischer-Tropsch synthesis (FTS). The results exhibit that the methane selectivities on all Co/SiC catalysts are lower than 9% and the preparation methods remarkably affect their catalytic performance. Among the three catalysts prepared by different methods, the catalyst obtained by the SG method shows the highest catalytic activity and C5+ selectivity for FTS, and their catalytic activities obey the order of SG > IWI > PCT. The excellent catalytic performance of Co3O4/SiC (SG) was analyzed and attributed to the appropriate Co3O4 grain size and cobalt-support interaction and the high reducibility and dispersion of Co oxide, which result in the suitable Co grain size and large concentration of surface Co active sites. Furthermore, the Co/SiC catalyst prepared by the SG method presents a highest stability after being used for 110 h when the FTS was conducted at 220 °C in a fixed-bed reactor that uses H2/CO syngas as a feed at 2 M ratio and 2 MPa total pressure. This study is of great guiding significance for synthesizing highly active and stable catalysts for FTS.