A novel catalyst for DME synthesis from CO hydrogenation 1. Activity, structure and surface properties

The effect of manganese on the dispersion, reduction behavior and active states: of surfaces of gamma -Al2O3 supported copper catalysts was investigated by X-ray powder diffraction (XRD), temperature-programmed reduction (TPR) and XPS technologies. The relationship between the area of metallic copper and the activity of dimethyl ether (DME) synthesis from CO/H-2 was also investigated. The catalytic activity over Cu-MnOx/gamma -Al2O3 catalyst for CO hydrogenation is higher than that of Cu/gamma -Al2O3. The adding of manganese increases the dispersion of the supported copper oxide. For the CuO/gamma -Al2O3 catalyst, there are two reducible copper oxide species; alpha- and beta -peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO-MnOx/gamma -Al2O3 catalyst, four reduction peaks are observed. The alpha -peak is attributed to the reduction of high dispersed copper oxide species; beta -peak is ascribed to the reduction of bulk CuO; gamma -peak is ascribed to the high-dispersed CuO interacting with Mn; and delta -peak is attributed to the reduction of the manganese oxide interacting with copper oxide. XPS results showed that Cu+ mostly existed on the working surface of the Cu-Mn/gamma -Al2O3 catalysts. Cu promoted the catalytic activity with positive charge, which was formed by means of long path exchange function between Cu-O-Mn. These results indicate that there are synergistic interactions between the copper and manganese oxide, which are responsible for the high activity of CO hydrogenation. (C) 2001 Elsevier Science B.V. All rights reserved.