Alkane dehydrogenation on defective BN quasi-molecular nanoflakes: DFT studies

Abstract

Lower alkanes are feedstocks readily available but relatively inert. The con- version of low cost alkanes to industrially relevant alkenes is usually carried out on metal-based heterogeneous catalysts. Considering both the cost and the potential harmfulness of the metal involved in the dehydrogenation cat- alysts (typically, platinum or chromium), the study of metal-free processes represents an important challenge for the industrial chemistry in order to address more sustainable protocols and different routes either to activate or transform alkanes. Framed in this context, it was investigated, using a den- sity functional theory approach, the potential dehydrogenation activity of de- fective and partially hydrogenated boron nitride quasi-molecular nanoflakes, on ethane, chloroethane and phenylethane. Concerted and not concerted reactions were considered, resulting the former always favored with respect to the latter and being the mechanisms and the corresponding energy char- acterizing the different substrates, in any case, quite similar. Along the dehydrogenation, given a certain hydrocarbon adsorption constellation, the defective nitrogen sites were generally more active than the boron ones, being the energy barriers, in any case, smaller or at least comparable with those al- ready observed for the metal catalyzed dehydrogenation processes. After the dehydrogenation processes, the hydrogenated boron nitride quasi-molecular nanoflakes resulted highly stabilized, suggesting that specific strategies are needed to employ these materials as catalysts.