An EXAFS investigation of Cu-ZnO methanol synthesis catalysts

Abstract

Cu K-edge EXAFS of calcined and reduced Cu-ZnO methanol synthesis catalysts (with a maximum copper content of 33 at wt. %) have been studied. The calcined catalysts contain two species, Cu²⁺ in a CuO-like phase and Cu²⁺ occupying substitutional sites in the ZnO lattice. The reduced catalysts contain three species, Cu⁰, Cu¹⁺ in a Cu₂O-like phase, and Cu¹⁺ in an interstitial site in the ZnO lattice. In carrying out the EXAFS analysis of these multiphasic catalysts, we have employed an additive relation for the EXAFS function and made use of residual spectra for identifying unknown species.