In situ DRIFTS study on the methanol oxidation by lattice oxygen over Cu/ZnO catalyst

Previous research shows that lattice oxygen of Cu catalyst participates in the methanol conversion. In this study, Cu/ZnO catalyst was pretreated to become fully oxidized, partially reduced, or completely reduced. In situ diffuse-reflectance infrared Fourier-transformed spectroscopy (DRIFTS) was used to analyze the methanol (MeOH) adsorption at 393 K and a following stepwise temperature-programmed desorption (sTPD). In addition to methoxy and formates appeared after MeOH adsorption, Cu/ZnO catalyst had formaldehyde but no CO2 while the Cu was completely reduced. When the Cu was in the oxidized or partially reduced states, CO2 formed and more formate appeared. Lattice oxygen participated in the MeOH conversion, and the reactivity was higher in the partially reduced Cu/ZnO than in the oxidized Cu/ZnO. This suggests that reduced Cu catalyzes the reaction between MeOH adspecies and lattice oxygen.

A sequential dehydrogenation to FAL, formyl, and CO occurs during methanol conversion on the completely reduced Cu/ZnO. Active oxygen related to Cu can react readily with adspecies on the surface leading to CO2 evolution.Figure optionsDownload high-quality image (171 K)Download as PowerPoint slideHighlights
► The state of Cu in Cu/ZnO was controlled by pretreating at different temperatures.
► In situ DRIFTS reveals the adspecies after methanol adsorption on Cu/ZnO catalyst.
► Lattice oxygen reacts with MeOH to CO2, and reduced Cu catalyzes this reaction.