The role of catalyst environment on CO2 hydrogenation in a fixed-bed reactor

Abstract

To reduce the negative impact that water formation has on the catalyst environment during CO2 hydrogenation reactions in a fixed-bed reactor, a start-up solvent, (mineral oil) was added to the reactor as a pretreatment. A Macrolite®-supported iron-based catalyst was used as the model catalyst to determine the impact of pretreatment with mineral oil on product selectivity, CO2 conversion, and catalyst stability over a range of reaction temperatures (280°C, 300°C, and 320°C). At the lower reaction temperatures (280°C, 300°C), CO2 conversion and C2-C5+ yield was increased by as much as 17% and 25% respectively by addition of start-up solvent. The characterization of the catalyst showed the formation of an iron manganese oxide phase, in the absence of the start-up solvent. Modeling and kinetic analysis of the data suggested that the start-up solvent decreased oxidation of the catalyst phase by reducing water adsorption, thereby increasing the Fischer-Tropsch reaction rate. This led to an increase in hydrocarbon yield in the presence of mineral oil.