3D-Printed Boron Nitride Catalytic Monoliths for Oxidative Dehydrogenation of Propane

Abstract

Boron-containing materials are efficient catalysts for the oxidative dehydrogenation of propane to propylene, proceeding via radical intermediates. The radical mechanism is initiated by the solid surface and propagated in the gas phase. It has been hypothesized that the propylene selectivity could be increased by enhancing the gas-phase contributions by favoring the formation of iso- over n-propyl radical intermediates. Indeed, whereas n-propyl radicals can be converted to both propylene and ethylene, iso-propyl radicals yield exclusively propylene. In this contribution, we explore 3D printing to structure the hexagonal boron nitride (hBN) heterogeneous catalyst with high void space. 3D-printed hBN monoliths were found to exhibit a higher olefin selectivity and a higher r propylene/r ethylene ratio as compared to traditional pack beds of hBN pellets. Our kinetic studies indicate the increase of reaction order in propane from 1.5 to 2.3, implying the promotion of gas-phase reaction. This work does not only shows that 3D-structured catalysts lead to higher propylene selectivity, it also confirms the hypothesized reaction mechanism and illustrates the power of molecular insights in selective oxidation chemistry to improve the performance. Graphical abstract: [Figure not available: see fulltext.]