CO₂ hydrogenation to hydrocarbons over alumina-supported iron catalyst: Effect of support pore size

The effect of support pore size of FeK/Al₂O₃ catalysts on the catalytic performance in CO₂ hydrogenation reaction was investigated. A total of 8 iron-based catalysts supported on alumina with different pore size were prepared by incipient wetness impregnation where the amount of Fe and K were fixed at 15 and 10 wt%, respectively. N₂ adsorption/desorption, XRD, TPR and PZC were used to characterize the supports and catalysts. The results show that the support pore size impacts the size of Fe₂O₃ particles formed in the catalyst; increasing pore size of Al₂O₃ supports led to increased size of Fe₂O₃ particles formed in the pores. Catalyst pore sizes of 7-10 nm and the corresponding Fe₂O₃ particle sizes of 5-8 nm were the most active for CO₂ hydrogenation to hydrocarbons. Outside this range, larger pore size further decrease the iron dispersion and reduce the number of active sites; smaller pore size is not favorable on account of the too small Fe₂O₃ particle sizes and lower reducibility of the small particle.