Mass transfer limitations on fixed-bed reactor for Fischer–Tropsch synthesis

Abstract

Mass transfer limitations on fixed-bed for Fischer–Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10 − 4 m s − 1 to 3.39 × 10 − 3 m s − 1 . As a result, the synthesis gas superficial velocity of 3.39 × 10 − 3 m s − 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount ( W cat/ F) were discussed. The large catalyst pellet showed higher C 5+ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α-olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount ( W cat/ F) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g ( W cat/ F = 45 g cat min L − 1 ) was most appropriate for liquid hydrocarbon formation.