Effect of process conditions on the product distribution of Fischer-Tropsch synthesis over an industrial cobalt-based catalyst using a fixed-bed reactor

[Display omitted] •Process conditions have complex and abnormal influences on chain growth.•Several accordant and opposite factors contribute to the abnormal observations.•The extent of α-olefin readsorption could influence the product selectivity. A systematic study of the effects of process variables on Fischer-Tropsch synthesis product selectivity over an industrial cobalt catalyst was carried out at a broad range of industrial conditions (T = 170−215 °C, P = 1.0–5.6 MPa, H2/CO = 2.0–3.0, WHSV = 2.0–23.4 N L/g/h) using a fixed-bed reactor. Lower temperature and higher pressure were beneficial for suppressing methane formation. However, a volcano-shape of temperature versus C19+ selectivity was observed. Correlations between pressure and C19+ selectivity were closely related to the temperature. Lower space velocity and inlet H2/CO ratio had mild but positive effects on the product distribution. The unique C19+ selectivity variations with temperature and pressure indicate a complicated chain growth process that stems from different aspects of the catalyst (i.e., chain propagation, chain termination and α-olefin readsorption) with process conditions. A mechanism involving several accordant and opposite effecting factors is considered for reasonably explaining the abnormal observations and providing a few reasonable interpretations of the contradictions among the related literatures.