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

Abstract

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 ZnZrOx/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 ZnZrOx and the reaction conditions, which facilitates the elimination of coke deposition. Hydrothermal treatment brings more Zn─O─Zr active sites and oxygen vacancies (Ov) on ZnZrOx, 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.