Influence of the zeolite surface properties and potassium modification on the Zn-catalyzed CO2-assisted oxidative dehydrogenation of ethane

Zeolites with incorporated Zn species are gaining relevance for catalyzing the dehydrogenation of short-chain alkanes. However, the presence of zinc also leads to the C-C cleavage in the alkane, lowering the selectivity to the olefin. We disclose herein the importance of controlling the zeolite particle size and the promoting role of K2O addition to improve the alkene selectivity and catalyst stability during Zn-catalyzed CO2-assisted oxidative dehydrogenation of ethane. In particular, the nano-sized SSZ-13 catalysts outperform the micro-sized SSZ-13 catalysts in terms of C2H6 conversion due to the critical role of zeolite crystal surface properties that improves the dispersion of the Zn phase. The modification of Zn with K2O neutralizes the acidity of the catalysts, suppressing the formation of undesired paths and leading to higher C2H4 selectivity and improved stability. Detailed characterizations and density functional theory show that K2O-neighbored (Zn-O-Zn)2+ lowers the activation barrier for the surface removal of H-based adsorbates. Overall, these findings demonstrate the roles of fine-tuning acid-base properties on the zeolite surface to control the catalytic performance during the CO2-assisted conversion of light alkanes.