Hydrocarbon Synthesis from Carbon Dioxide and Hydrogen: A Two-Step Process

CO 2 hydrogenation to olefins and ethylene oligomerization were investigated in efforts to improve catalyst composition and reaction conditions needed for scale-up. The hydrogenation of CO 2 to hydrocarbons is investigated over γ-alumina-supported iron-based catalysts modified with manganese and potassium promoters and a silica-stabilized coating under fixed-bed reactor conditions to produce unsaturated hydrocarbons as feedstock chemicals for jet fuel synthesis. The stabilizer is introduced by impregnating the K/Mn/Fe on Al 2 O 3 catalyst with tetraethylorthosilicate (TEOS) to minimize the deactivating effects of water on catalyst activity in CO 2 hydrogenation. The K/Mn/Fe on Al 2 O 3 catalyst modified with the TEOS and reduced in CO produced a lighter end fraction of olefins compared to the catalyst reduced in H 2 . To increase the chain length of the olefins formed in the CO 2 hydrogenation step, investigation of the oligomerization reaction is conducted in a separate experiment, where pure ethylene is used as a model olefin. Ethylene oligomerization over pelletized amorphous silica–alumina (ASA)-supported Ni catalysts demonstrated high conversion and selectivity toward the jet fuel fraction (C 8 –C 16 ) at a very low mass hourly space velocity (MHSV).