Hydrogenation of CO₂ to Propylene and Butene Over ZnZrO_x/SAPO-18

Recycling CO₂ to light olefins (C₂ ${}^{=}$ - C₄ ${}^{=}$ ) is a promising strategy for long-term carbon storage. However, selective hydrogenation to light olefins while suppressing alkane formation remains a challenge. This work presents an optimized ZnZrO_x/SAPO-18 tandem catalyst, which achieves 88.7% light olefins selectivity at 9.5% CO₂ conversion with C₃ ${}^{=}$ +C₄ ${}^{=}$ dominating 68.4% of the hydrocarbons. The catalyst exhibits resistance to over hydrogenation, yielding the (C₂ ${}^{=}$ -C₄ ${}^{=}$ )/(C₂ ⁰-C₄ ⁰) (O/P) ratio of 17.7 and only  1.4% CH₄ selectivity. Furthermore, the catalyst shows good stability over 100 h on stream without obvious deactivation, owing to the synergistic effect between ZnZrO_x and the reaction conditions, which facilitates the elimination of coke deposition. Hydrothermal treatment brings more Zn─O─Zr active sites and oxygen vacancies (O_v) on ZnZrO_x, as well as the modulated Brønsted acid sites (BAS) in SAPO-18 suppresses the over-hydrogenation of olefins, and the AEI-type cage can contain expanded hydrocarbon pool (HCP) intermediates for enhanced C₃ ${}^{=}$ +C₄ ${}^{=}$ formation. This study advances the development of selective CO₂-to-olefin conversion technologies.