Highly Efficient Ethylene Glycol Production from Photocatalytic Ethylene Oxidation over Commercial Zinc Oxide Nanopowder

Abstract

Abstract Current industrial synthesis of ethylene glycol (EG) relies on a multistep thermocatalytic process involving ethylene oxide intermediates under elevated temperatures and pressures, which is energy-intensive and prone to overoxidation to CO2. While photocatalysis provides a promising alternative, existing direct conversion methods suffer from low efficiencies and require complex, noble-metal cocatalysts. Here, we demonstrate that unmodified, commercially obtained ZnO nanopowders can catalyze the highly selective, direct photocatalytic oxidation of ethylene to EG. Under 365 nm irradiation, ZnO achieves unprecedented production rates of 4.65 mmol gcat–1 h–1 at 105 °C with ∼70% liquid product selectivity. Mechanistic studies indicate a dual-hydroxylation pathway utilizing reactive oxygen species from O2 activation. Superior to TiO2 and other photocatalysts, the optimal band positions and surface properties of ZnO efficiently activate O2 and suppress overoxidation, offering a highly scalable and cost-effective route for direct alkene oxidation.