Effect of Diffusion Limitations on the Fischer–Tropsch Synthesis of Long-Chain Hydrocarbons on a Cobalt–Alumina Silica Gel Catalyst

Abstract

The effect of diffusion limitations on the Fischer–Tropsch synthesis of long-chain hydrocarbons on a cobalt–alumina–silica gel catalyst are analyzed at pressures of 1.5 and 2.0 MPa, depending on the particle size distribution (0.4–6.0 mm), gas hourly space velocity (100–1000 h⁻¹), and composition of the synthesis gas (H₂ : CO = 1, 2, and 5). It is shown that mass limitations increase the selectivity and productivity of C₃₅₊ hydrocarbons (waxes) and the probability of hydrocarbon chain growth. The effect of intradiffusion limitations is estimated at different compositions of the synthesis gas from changes in the apparent energy of activation in the temperature range of 179–225°С. In the high-temperature region, the apparent energy of activation falls from 97.1 to 67.0–82.9 kJ/mol as the H₂/CO ratio rises from 1 to 5.