The effect of zirconium on cobalt catalyst in fischer-tropsch synthesis

A series of 10 wt % Co/SiO2 catalysts with different loading ratios of zirconia (0, 5, 10, 15, 20) has been prepared through an original pseudo sol-gel method. All catalysts were characterized by BET, XRD, SEM, and TPR experiments. The catalytic performance of the catalysts for the so-called fischer- tropsch synthesis was examined under H2/CO=2 at 230digC and 8 bar in a fixed bed microreactor. By increasing zirconia, the Co-SiO2 interaction decreases and is replaced by Co-Zr interaction which favours reduction of the catalyst at lower temperatures. While it leads to a higher degree of reduction and as increase in the metallic cobalt atoms on the surface. The activity of the promoted catalysts increases with the addition of zirconia (max. by a factor 2.5). The C10+ selectivity increased with the addition of zirconia (from 42.3% in unpromoted catalyst to 68.8 % in the 20 % ZrO2 promoted. This can be attributed to the higher amount of the surface Cobalt metal present and to the larger Cobalt particle size