Selective hydrogenation of alkynes is widely used to remove by-products from steam cracking in the petrochemical processes, and also a typical probe reaction for hydrogenation catalysts. Conventionally, Pd-based catalysts were used for the selective hydrogenation of alkyne due to their high activities at moderate temperature and hydrogen pressures. However, concerns on the selectivitis and stabilities losses result from the overhydrogenation and oligomerization side reactions of Pd based catalysts driven the search for more efficient catalysts, especially nonprecious alternatives. pure ceria catalysts exhibited remarkable olefin selectivity of 91% (81%) at a high degree of alkyne conversion (propyne: 96%, ethyne: 86%) and stable behavior, showing great potential for industial application.To understand the role of defects on ceria catalysts for selective hydrogenation reactions, we studied selective hydrogenation of propyne on both CeO2(111) and CeO2-x(111)-H surfaces. While both surfaces could exhibit high selectivity for semi-hydrogenation, the CeO2-x(111)-H surface shows a conversion rate 3 times higher than that on the CeO2(111). Using in-situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory (DFT) calculations, we studied the formation and evolution of hydride (Ce4+H-) species on the above surfaces and during catalytic hydrogenation reaction. We found that surface oxygen vacancy (Ov) sites are required for the formation of hydride species and for the activation of propyne, both of which are required for the onset hydrogenation of propyne. Hydride species on CeO2-x(111)-H could weaken the adsorption of propyne and prevent the poison effect of coke formation. Upon the desorption of hydride species, coke formation occurred on ceria surfaces with &gt;10% oxygen vacancy sites and caused the deactivation of ceria. Our study has thus demonstrated the crucial synergetic roles of surface Ov sites and hydride species on ceria for the selective hydrogenation reaction.

Selective hydrogenation of propyne to propene promoted by synergetic effect of oxygen vacancies and hydride species on ceria

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.