Production and functionalization of unsaturated hydrocarbons (olefins and aromatics) are foundational processes in the chemical industry. However, the unusual balance of reactivity between the product and reactant leads to considerable challenges in controlling catalyst selectivity while still achieving appreciable conversion. Non-noble metal intermetallic compounds (IMCs) composed of atomically ordered mixtures of transition metals (TM) and post-transition metal or semimetal elements provide a large compositional space that can be utilized to tune the surface chemistry towards C–H and C–C bonds of various saturations that is of significant interest to the greater heterogeneous catalysis community. In this study, propane dehydrogenation over non-noble metal intermetallic compound (IMC) catalysts to understand how the innate surface chemistry of a suit of IMCs promotes C–H activation while simultaneously limits C=C or C–C activation, hydrogenation, and coke formation. The most selective catalyst that also showed appreciable activity consisted of a Ni+Ga composition with tailored IMC surface composition. The catalyst presented appreciable stability towards olefin production with only moderate deactivation detected after extended operation (total olefin selectivity began at ~95% and fell to only 93% after an 82+ h run) at 600C. The catalyst also exhibited the ability to be regenerated easily in situ with only redox treatments. A various of spectroscopies including HS-LEIS, in-situ DRIFTS, and EELS were employed to unravel how the surface composition change affects the catalytic activity and selectivity. Synthesis methods were designed such that a single IMC phase was promoted regardless of the actual loading of Ni and Ga. This feature allowed control of the IMC surface composition and insights into the tunability of the surface and catalytic chemistry of the materials. Investigation of reaction mechanism network and electronic structure of the catalyst using quantum chemical modeling techniques showed that surface reactivity could be systematically tuned by manipulating the surface composition of the IMC with predicted activity agreeing well with our experimental observations.

Effect of surface composition change of non-noble metal intermetallic compounds on the activation of C-H and C=C bonds in the dehydrogenation of light hydrocarbons

2019 Spring National Meeting

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