Production of isoparaffinic gasoline from CO2/CO over ZnO-ZrO2/nano-sized HZSM-5 tandem catalyst

The performance (conversion, yield, and product selectivity) of ZnO-ZrO₂/nano-sized HZSM-5 tandem catalysts in the direct hydrogenation of CO₂/CO (CO_x) mixtures to C₅₊ hydrocarbons (gasoline) was investigated at 50 bar and 420 ºC. A 1/1 mass ratio between the acid and metallic catalysts in the tandem configuration proved effective for maximizing synergy between the stages of methanol synthesis and its conversion, significantly shifting the thermodynamic equilibrium of methanol synthesis. The tandem catalyst configuration within a single particle (bifunctional catalyst), which is of interest for scale-up, faces challenges compared to physical mixing of the catalysts. These include deterioration of catalytic properties during pelletization, partially blocking the zeolite micropores and acid sites. However, the shorter distance between the metallic and acid sites in the bifunctional catalyst enhances synergy between the reaction stages, compensating for these issues. As a result, with the bifunctional catalyst it is achieved high CO_x and CO₂ conversions (27.9 % and 32.6 %, respectively) and a high gasoline yield (21.3 %). The isoparaffinic composition (70 %) of the produced gasoline, with a negligible aromatic content, makes it suitable for applications requiring low environmental impact and promising for integration into refinery gasoline pools.