Hydrogenation of Propene on Cobalt Fischer–Tropsch Catalysts

Abstract

Hydrogenation of propene to propane has been studied as a model reaction for secondary hydrogenation of olefins in the Fischer–Tropsch (FT) synthesis. The study has involved promoted and unpromoted cobalt FT catalysts supported on different types of supports. The hydrogenation of propene was carried out at 120°C, 1.8 bar and H2/C3H6=6. Co and Co–Re supported on alumina with different surface areas gave catalysts with different dispersion of cobalt. The cobalt dispersion for the alumina supported catalysts increased with increasing surface area. The rate of propene hydrogenation (based on exposed Co) also increased with increasing surface area of the alumina support. The rate for CoRe supported on TiO2 corresponded to the alumina support with equal (low) surface area, but the SiO2 supported catalyst did not. CO hydrogenation on the same alumina supported catalysts at FT conditions (210°C, 20bar and H2/CO=2.1) has shown that the C5+ selectivity increases with decreasing surface area of the alumina support. The increased C5+ selectivity fits very well with the decreased importance of olefin hydrogenation on catalysts with low surface area. The olefins will to a larger extent readsorb and participate in further chain growth rather than being hydrogenated to paraffins.