Ethanol dehydrogenation over copper catalysts on rice husk ash prepared by ion exchange

Abstract

Samples of copper on rice husk ash (Cu/RHA) have been prepared by the ion exchange method, with various copper loadings, and have been calcined at different temperatures. Such samples were tested for dehydrogenation of ethanol to acetaldehyde. The samples were characterized by DSC, XRD, FTIR, TEM, XPS, TPR, BET, and H 2–N 2O titration techniques. FTIR spectra illustrate the formation of chrysocolla in uncalcined and calcined Cu/RHA catalyst precursors. DSC, XRD and XPS analyses illustrate that, in Cu/RHA catalyst precursor after drying at 383 K, copper is present as Cu(OH) 2 species. After calcination at 723 K, copper is present as Cu 2+ ions and as CuO species. After reduction of the calcined Cu/RHA sample at 523–573 K, copper is present as Cu + and/or Cu 0 species along with unreduced Cu 2+ species. TEM images show that copper crystallites are spherical in shape and are evenly distributed. TPR results reveal that various copper loadings in calcined Cu/RHA catalyst precursor exhibit similar metal-support interactions (MSI). Ethanol conversion for dehydrogenation of ethanol is found to be independent of calcination temperature and has little effect on Cu loading. Ethanol is selectively converted to acetaldehyde at the reaction temperature of 483–548 K. The Cu/RHA catalysts exhibit higher catalytic activity and lower deactivation rate than Cu/SiO 2 catalysts. The activity of Cu/RHA catalysts is found to depend on Cu surface area.