(667f) Electrochemical and Thermal Conversions of Light Alkanes Under Room Temperature and Ambient Pressure

The direct conversion of light alkanes into value-added commodities such as olefins, alcohols and carboxyl acids is of great economic and industrial importance. High temperatures (200-600 ºC) and/or elevated pressures (usually 5-50 bar) are typically needed to facilitate the reaction, which requires large-scale infrastructures to accommodate the energy requirements efficiently, hindering their implementation on small-scale and distributed productions. Harsh conditions also increases the propensity of the overoxidation of light alkanes to undesired CO₂ due to the higher reactivity of the products resulting from light alkane conversions compared to the initial feed alkanes.

In this work, we report aqueous reaction systems capable of selectively converting light alkanes into corresponding olefins and oxygenates at room temperature and ambient pressure using commercial Cu powder as catalyst and O₂ as oxidant. In ethane activation, we achieved a combined production of ethylene and acetic acid at a rate of 2.27 mmol g_Cu⁻¹h⁻¹, with a combined selectivity up to 97%. Propane is converted to propylene with a selectivity up to 94% with a production rate of 1.83 mmol g_Cu⁻¹ h⁻¹, while methane is converted mainly to carbon dioxide, methanol and acetic acid. 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. The reaction system performance is further improved by reactor engineering, where a Cu tube is used as both a microchannel reactor and the catalytic surface to enhance the mass transport of reactant gas. The propylene production rate increases 27-fold under similar conditions and 120-fold at 40 ºC while maintaining the propylene selectivity over 92%. Our system paves the way for selective C–H bond activation, offering opportunities for functionalizing light alkanes under mild conditions.