Palladium-catalyzed selective oxidation of ethane to acetate acid

The selective oxidation of ethane to acetate acid represents a promising route for ethane conversion, which is currently challenged by the high C-H bonding energy in ethane molecules and the incidental side reactions under employed conditions. We demonstrate herein that a simple PdCl₂ catalyst can efficiently catalyze the selective oxidation of ethane to acetate acid in the reaction system of C₂H₆-O₂-CO-H₂O. The impacts of reaction parameters on ethane oxidation are systematically investigated. Kinetic and spectroscopic analyses reveal the reaction pathway starting from a water-gas-shift reaction, followed by <i>in-situ</i> hydroxyl radical and H₂O₂ formation for efficient ethane oxidation. In the refined reaction system with the addition of sulfuric acid, high ethane conversion of 15.7% and high acetate acid selectivity of 92.1% can be achieved at the same time, offering a state-of-the-art acetate acid space-time-yield of 372.7 mol_CH3COOH mol_Pd ^-1 h^-1 with great potential for practical applications. Finally, the reaction pathway and mechanism of ethane oxidation are interpreted by theoretical calculations to shed light on the rational design of reaction systems for natural gas upgrading.