Accumulation and distribution of higher hydrocarbons in the pores of a cobalt catalyst during low-temperature Fischer–Tropsch fixed-bed synthesis

Abstract

During low-temperature Fischer–Tropsch synthesis (FTS), the catalyst pores are filled with liquid hydrocarbons. In a fixed-bed reactor, axial concentration gradients are present in the gas phase (CO, H₂, evaporated hydrocarbons (HCs)). This leads to local (axial) changes of the composition of the liquid present in the pores and of the liquid phase trickling down the bed. A model based on the kinetics of the FTS, evaporation of HCs by external mass transfer, and vapor–liquid equilibrium was developed to describe the composition of both the gas and liquid phase at steady-state conditions. The influence of CO conversion and selected reaction parameters was investigated and compared with experiments in a single pellet string reactor.