Studies on MCM-48 supported cobalt catalyst for Fischer–Tropsch synthesis

MCM-48 molecule sieve was used as a support of cobalt catalyst for Fischer–Tropsch synthesis (FTS). Co/MCM-48 catalysts were prepared using incipient witness impregnation method with cobalt loadings of 5, 10 and 15 wt.%, respectively. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD) followed by pulse oxygen titration and transmission electron microscopy (TEM). The catalytic properties for FTS were tested in a fixed bed reactor. TPR and oxygen titration indicated different extent of overall reduction of Co cobalt species in different cobalt content catalysts. With increasing Co loading, CO conversion and C5+ selectivity first increased remarkably and then remained nearly invariable. Lower reducibility of smaller cobalt particles on 5Co/MCM-48 is likely to be one of the reasons responsible for the lower CO conversion and highest methane selectivity. Co loading exceeding 10 wt.% had no significant effect on FTS properties of the catalysts.

MCM-48 molecule sieve was used as a support of cobalt catalyst for Fischer–Tropsch synthesis (FTS). Co/MCM-48 catalysts were prepared with cobalt loadings of 5, 10 and 15 wt.%, respectively, and catalytic properties for FTS were tested. The figure shows the cobalt crystallite size distributions for the catalysts obtained by TEM method. The Co3O4 crystallites size of 5Co/MCM-48, 10Co/MCM-48 and 15Co/MCM-48 below 5 nm is about 92, 83 and 79%, respectively. Small Co crystallites below 5 nm appear to reoxidize and deactivate rapidly in presence of water and other reaction products. The reducibility of the Co crystallites on the catalysts determined their FTS activity and hydrocarbon selectivity.Figure optionsDownload as PowerPoint slide