Photooxidation of ethylene over Cu-modified and unmodified silica

Abstract

Silica catalyzes photooxidation of ethylene to carbon dioxide and modification of copper on silica results in the lower reaction rate and partial production of ethylene oxide. The reaction does not proceed by the light irradiation through a color filter (λ>280 nm). ESR measurement indicates that radical oxygen species assignable T-shape Si − O3− can be produced on silica by UV irradiation at 77 K. The same species are also found on silica modified with copper by UV irradiation while the quantity is smaller. When silica and silica modified with copper are UV-irradiated in presence of oxygen and ethylene at 77 K, formation of methyl radicals is confirmed only on silica while ethyl radicals are observed with both samples. We suggest that copper stabilizes C2 species and prevents cleavage of C − C bonding.