CO2‐Mediated Oxidative Dehydrogenation of Propane over Zn Modified SSZ‐39 Catalysts

Abstract To reveal the catalytic function of Brønsted acid sites (BAS) and different Zn Lewis acid sites (LAS) over SSZ‐39 and Zn modified SSZ‐39 in the direct dehydrogenation of propane (DHP) and CO 2 ‐mediated oxidative dehydrogenation (CO 2 ‐ODHP) to propylene, a series of Zn‐modified H(Na)SSZ‐39 catalysts with various Zn loadings was prepared and conducted comparative studies between DHP and CO 2 ‐ODHP. Detailed characterization results reveal the Zn‐loading‐dependent formation of Zn sites, primarily including Zn 2+ and [Zn−O−Zn] 2+ , as well as their contributions in generating Lewis acid sites while neutralizing Brønsted acid sites of HSSZ‐39, namely bridged Si(OH)Al groups. In DHP, in comparison to bare HSSZ‐39, Zn/HSSZ‐39 catalysts exhibited a significantly enhanced C 3 H 8 conversion. The presence of CO 2 even further promoted C 3 H 8 conversion in comparison to DHP. Given the above observations, we prepared Zn/NaSSZ‐39, in which the incorporation of Na further enriches the Lewis acid sites while neutralizing Brønsted acid sites of zeolite. Zn/NaSSZ‐39 even outperforms Zn/HSSZ‐39 catalysts with almost doubled C 3 H 6 yield for CO 2 ‐ODHP. The BAS has a poor CO 2 ‐ODHP performance but can enhance the CO 2 conversion towards CO significantly, while the Zn LAS is favorable for the CO 2 ‐ODHP reaction, and plausible reaction paths of CO 2 ‐ODHP on active sites are proposed.