Formation of ethylene oxide by photooxidation of ethylene over silica modified with copper

Abstract

Silica and silica modified with copper can catalyze the photooxidation of ethylene with molecular oxygen. Without the modification silica mostly produces carbon dioxide, however, Cu-modified silica yields various oxidative products such as acetaldehyde, ethylene oxide and ethanol. In particular silica containing only 0. 1wt% of copper gives a maximum yield of ethylene oxide, implying that copper is not a major photooxidation site for ethylene oxide. No reaction takes place with the irradiation of light whose wavelength is longer than 280 nm. The UV-visible diffuse reflectance spectra of silica with and without modification of copper suggest that the UV absorption of silica promote the photooxidation of ethylene. Formation of ethylene oxide can proceed even after exhaustion of oxygen in gas phase, indicating that surface oxygen species take important roles in the photooxidation of ethylene to ethylene oxide.