CO₂ Hydrogenation to Hydrocarbons over Iron-based Catalyst: Effects of Physicochemical Properties of Al₂O₃ Supports

The effects of surface hydroxyl groups and SiO 2 content of alumina supports for FeK/Al 2 O 3 catalysts on their activity and product selectivity for CO 2 hydrogenation to hydrocarbons reaction were investigated. A series of iron-based catalysts supported on six commercial Al 2 O 3 supports were prepared and tested for hydrocarbons production in a fixed-bed reactor. Surface acidic–basic hydroxyls distribution of the supports were evaluated by Fourier transform infrared (FT-IR) and point of zero charge (PZC) measurement. It was found that the PZC of Al 2 O 3 supports strongly affects the dispersion as well as particle size of the Fe-based catalysts. Increasing PZC value of Al 2 O 3, the iron dispersion increased and particle size decreased. The highest CO 2 conversion (54.4%) and C 5 + hydrocarbons selectivity (31.1%) were achieved when the PZC was 8.0. CO 2 conversion and the long-chain products selectivity decreased when PZC declined. Moreover, SiO 2 -doping of alumina strongly affected the surface acidic–basic hydroxyls distribution of the supports, while a desired SiO 2 content improved the catalyst activity by adjusting CO adsorption and the reduction behavior of the iron-based catalysts.