Selective Transformation of CO2 and H2 into Lower Olefins over In2O3‐ZnZrOx/SAPO‐34 Bifunctional Catalysts

Because lower olefins (C₂ ⁼ -C₄ ⁼ ) are important bulk petrochemicals, their direct production from CO₂ hydrogenation is highly attractive. However, the selectivity towards C₂ ⁼ -C₄ ⁼ by the modified Fischer-Tropsch synthesis is restricted to 56.7 % with high undesired methane selectivity. Here, a series of bifunctional catalysts containing In₂ O₃ -ZnZrO_x oxides and various SAPO-34 zeolites with different crystal sizes (0.4-1.5 μm) and pore structures was developed for the production of lower olefins by CO₂ hydrogenation. The C₂ ⁼ -C₄ ⁼ selectivity reached as high as 85 % among all hydrocarbons with very low CH₄ selectivity of only 1 % at a CO₂ conversion of 17 %. This demonstrated that the small crystal size, hierarchical pore structure, and appropriate amount of Brønsted acid sites of SAPO-34 endowed the bifunctional catalysts with high C₂ ⁼ -C₄ ⁼ selectivity. This work shows an efficient way for developing bifunctional catalysts for direct CO₂ hydrogenation to lower olefins.