FTIR study of 12C 16O and 13C 18O coadsorption on Cu–ZSM-5

Abstract

Adsorption of 12C 16O– 13C 18O isotopic mixtures was used to establish polycarbonyl structures formed with Cu + ions in Cu–ZSM-5. The principal Cu +( 12C 16O) 2 dicarbonyls are characterized by ν s at 2178 cm −1 and ν as at 2151 cm −1. In excellent agreement with theory, Cu +( 12C 16O)( 13C 18O) mixed-ligand species were found to absorb at 2168 and 2065 cm −1. Another kind of dicarbonyls, characterized by ν s at 2183 cm −1, was also unambiguously detected. Tricarbonyls are characterized by two IR modes, at 2191 and 2166 cm −1. Different bands of Cu +( 12C 16O) x ( 13C 18O) y ( x + y = 3) species were established. The use of isotopic mixtures also helped in the assignment of a shoulder at 2194 cm −1 to Cu 2+–CO adducts.