Influence of the formation of short-chain olefins by manganese/cobalt-catalyzed Fischer–Tropsch synthesis on the selectivity and effective reaction rate

The Fischer–Tropsch synthesis (FTS) offers a wide ranging distribution of hydrocarbons. For cobalt catalysts with manganese as a promoter, a high selectivity to olefins is found for the low-temperature FTS. In this work, Mn–Co catalysts on SiO2 as support were tested. For small catalyst particles (≤150 μm), a high selectivity towards C3–C8 olefins with an SC3−C8,ole = 38% was obtained. For larger particles (diameters of up to 1.6 mm), an unexpected higher reaction rate, a higher chain growth probability, and a decrease in olefin selectivity (SC3−C8,ole = 7%) were observed. These effects can be explained by secondary reactions of the olefins combined with the influence of pore diffusion.