The Influence of Diffusion Limitations on the Fischer – Tropsch Synthesis of Long-Chain Hydrocarbons over a Cobalt-Silica Catalyst

Abstract

The influence of diffusion limitations on the Fischer – Tropsch synthesis of long-chain hydrocarbons over a cobalt-silica catalyst was studied at 1.5 and 2.0 MPa depending on the grain composition (0.4–6.0 mm), gas flow rate (100–1000 h –1 ), and composition of synthesis gas (H 2 /CO = 1, 2, 5). It was shown that the selectivity and the production of C 35+ hydrocarbons (waxes), as well as the probability α of the hydrocarbon chain growth increased under conditions of mass limitation. Variations in the apparent activation energy at 179–225 °C were used to estimate the influence of diffusion limitations depending on the syngas composition. In the high-temperature region, an increase in the hydrogen to carbon monoxide ratio from 1 to 5 resulted in a decrease in the apparent activation energy from 97.1 kJ/mol to 67.0–82.9 kJ/mol.