A sustainable mesoporous palladium-alumina catalyst for efficient hydrogen release from N-heterocyclic liquid organic hydrogen carriers

Abstract

Liquid organic hydrogen carriers (LOHC) are interesting hydrogen vectors which can exploit existing infrastructure. Specifically, N-heterocyclic compounds are attractive due to lower dehydrogenation enthalpy than homocyclic ones and demand a viable palladium catalyst to guarantee high dehydrogenation activity at low temperatures and stability in recycle runs. Here, we employ one-pot solvent deficient precipitation yielding a mesoporous palladium-alumina. The prepared catalyst system offers higher hydrogen release capability by 20% than conventional palladium/γ-Al2O3 in the dehydrogenation of four different N-heterocyclic compounds at or below 250 °C. Futhermore, it shows negligible activity loss up to five consecutive runs for perhydro 2-(n-methylbenzyl)pyridine and perhydro 2-methylindole. Such dehydrogenation performance is caused by the solvent deficient environment that restricts palladium mobility by contiguous alumina particles and produces well-dispersed palladium phase with a higher density of (111) plane. Therefore, the reported synthesis method may contribute to the production of innovative dehydrogenation catalysts for LOHC compounds.