Extended X-ray absorption fine structure study of the reaction between silica-supported copper(II) oxide catalysts and acetic acid

Abstract

Structural changes of two kinds of silica-supported copper(II) oxide catalysts caused by reaction with acetic acid vapour have been studied by means of XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure). The structure of the catalyst derived from copper(II) acetate changes from a low-dimensional CuO chain to the mixture of the binuclear copper(II) species similar to its starting compound and metallic copper, whereas acetic acid vapour cleaves CuO parallelogram units in the catalyst derived from tetra-ammine copper(II), then gives monomeric copper(II) species as the main product. The formation of distinct copper species is ascribed to the different copper(II) oxide species in each sample. Reaction mechanisms are discussed on the basis of the structures of the catalysts.