Bare La2O3 in non-oxidative propane dehydrogenation: in situ decoration of active sites for enhanced catalyst performance

Abstract

To replace toxic or expensive CrO_x- or Pt-based catalysts currently used in large-scale production of propene through non-oxidative dehydrogenation of propane, ecologically friendly and cost-effective alternatives are needed. In this context, we introduce La₂O₃ as a promising catalyst for this reaction. Our characterization and catalytic experiments as well as density functional theory calculations revealed that coordinatively unsaturated La³⁺ cations (La_cus) possess high activity to the cleavage of the C–H bond in propane. However, they strongly adsorb propene and hydrogen atoms formed from propane, favoring the formation of coke but hindering their recovery by H₂ desorption. La_cus can, however, be decorated with hydrogen species in the presence of gas-phase H₂. These new species show high activity for propane activation but low ability to adsorb propene and open a more energetically favorable pathway for H₂ formation. La₂O₃ does not obviously differ from an industrial analogue of K-CrO_x/Al₂O₃ in terms of propene selectivity up to 60% equilibrium propane conversion at 600 °C using a feed with 40 vol% C₃H₈ and 30 vol% H₂ in N₂. The effect of hydrogen on the PDH performance of La₂O₃ may inspire other researchers involved in the development of alternative catalysts, which are typically tested in the absence of hydrogen.