(93a) Fundamental Understanding of Surface Reactivity of Non-Noble Metal Intermetallic Compound Catalysts to Control C–H and C=C Bond Activation in Alkane Dehydrogenation

Fundamental Understanding of Surface Reactivity of Non-noble Metal Intermetallic Compound Catalysts to Control C–H and C=C Bond Activation in Alkane Dehydrogenation

Yang He, Yuanjun Song, and Siris Laursen

Chemical and Biomolecular Engineering

University of Tennessee, Knoxville

slaursen@utk.edu

ABSTRACT

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. In this study, the dehydrogenation of light alkanes (e.g. ethane and propane) over non-noble transition metal intermetallic compound (IMC) catalysts were investigated 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. A fundamental understanding has been developed on the growth mechanism of TM IMC particles and the most critical parameters that enable control over the bulk stoichiometry and surface composition of TM IMCs. This further makes it possible to investigate the surface chemistry of a suite of well-defined TM IMCs in promoting C–H activation while simultaneously limiting C=C or C–C activation, hydrogenation, and coke formation. A suite of supported Ni+Ga IMC catalysts have been found to exhibit high steady-state selectivity towards ethylene (~94%) and propylene (~93%) with impressive long-term stability (82 hrs) and regenerability in the direct dehydrogenation of ethane and propane. Investigation of reaction mechanism network energetics 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.