(597f) Efficient Conversion of Ethane and Propane at Room Temperature and Ambient Pressure

The direct conversion of light alkanes into value-added commodities is of great economic importance. At present, high temperatures (200-600 °C) and/or elevated pressures (typically 5-50 bar) are typically needed to facilitate the reaction, which requires large-scale infrastructures to accommodate the tortuous energetic pathways, hindering their implementation on small-scale and distributed productions. In our study, we report an aqueous reaction system capable of selectively converting light alkanes into olefins and oxygenates at room temperature and ambient pressure using Cu as catalyst and oxygen as oxidant. In ethane and propane activation under ambient conditions, we achieve comparable results to those in literatures that are obtained at elevated temperatures. Our system can convert ethane to ethylene and acetic acid with a high selectivity up to 97%, and propane mostly to propene with a selectivity up to 94%. Based on catalytic experiments, spectroscopic insights and density functional theory calculations, we put forward mechanistic understandings in which C-H bond is activated by surface oxide species generated during oxidation process forming alkyl groups as key reaction intermediates. To further promote alkane activations limited by the low solubility of gaseous reactants, we introduce a microfluidic reaction system with a Cu microtube serving as both the catalyst and the microchannel reactor. This innovative setup exhibits a 27-fold increase in reactivity compared to previous batch reactors, while maintaining propylene selectivity above 92%. Additionally, by combining alkane activations with an electrochemical system utilizing Cu plates as both electrodes and catalysts, we achieve consistent production of ethylene and acetic acid from ethane activation over a 10-hour run, with sustained selectivity above 96% and a concentration of acetic acid reaching 19 mM. These findings represent remarkable progress in the electrochemical activation of light alkanes under mild conditions. Our in situ spectroscopic investigations, analysis of partial pressure dependencies, and computational results provide a deeper understanding of the competitive adsorption behavior of oxygen and alkanes on the Cu surface. These strategies hold great promise for pioneering decentralized alkane conversion processes, enabling on-site and long-term utilization of light alkanes at ambient conditions.