Highly selective photocatalytic synthesis of ethylene-derived commodity chemicals on BiOBr nanosheets

Abstract

The synthesis of ethylene-derived commodity chemicals is an important process in industry. However, the current manufacturing process is energy-intensive and contributes a significant amount of greenhouse gas emissions. Photocatalytic conversion of ethylene to target products is a more sustainable and green alternative. In this work, we designed a bromide-mediated photocatalytic approach for highly selective synthesis of ethylene oxide or ethylene glycol from ethylene. The bromine/hypobromous acid (Br2/HOBr) generated in photocatalytic process are effective active species for conversion of gaseous ethylene to liquid intermediates, bromoethanol and dibromoethane. These intermediates were further converted to ethylene oxide or ethylene glycol via a facile alkali treatment in different temperatures, giving rise to a high selectivity of 92% and 100%, respectively. Interestingly, the BiOBr could oxidize its crystal Br− to generate Br2/HOBr efficiently, which is a more favorable process thermodynamically than oxidation of aqueous Br−. Furthermore, long-term stability (> 40 h) of BiOBr is maintained by adding KBr in the reaction system to automatically replenish Br− in BiOBr. This work provides a potential alternative to current industrial method for green synthesis of ethylene-derived commodity chemicals.