CO₂ hydrogenation into hydrocarbons over CFA-HZSM-5 hybrid catalysts

The increase of the concentration of greenhouse gases in the atmosphere, especially CO₂, produced mainly by the burning of fossil fuels is one of the principal causes of global warming. The transformation of CO₂ into tangible products such as fuels and/or raw materials for the petrochemical industry (methanol, hydrocarbons) is one of the possible routes. The synthesis of hydrocarbons by hydrogenation of CO₂ can be done in a single step using oxide/zeolite catalysts. The objective of our study was to evaluate the effect of the addition of zeolite and the proximity between the two oxide-zeolite sites where the oxide layer is iron-based and wherein the zeolite is represented by the HZSM-5. For this, a series of hybrid catalysts was prepared by CuO-Fe₂O₃-Al₂O₃/HZSM-5 mechanical mixing. The catalytic conversion of CO₂ has been carried out in a fixed-bed reactor under the following operating conditions: T = 350 C, P = 30 bar, H₂/CO₂ = 3. The results show that the addition of the zeolite by intimately mixing it does not improve the catalytic properties and that the yield of hydrocarbons is best obtained with the CuO-Fe₂O₃-Al₂O₃ oxide catalyst according to the Fisher-Tropsch process (FT). However, the increase in near-zeolite oxide inhibits the formation of hydrocarbons and promotes the formation of carbon monoxide. (authors)