Structure and catalytic performance of alumina-supported copper-cobalt catalysts for carbon monoxide hydrogenation

The structure of alumina-supported copper-cobalt catalysts prepared by incipient co-impregnation was studied by using a combination of various characterization techniques including in situ XRD, XPS, TPR, XANES/EXAFS, in situ magnetic method, and TEM. The results suggest a much higher dispersion of copper than cobalt on gamma-Al2O3 and a stronger interaction between cobalt and copper oxide particles, leading to the formation of mixed copper-cobalt oxides in the calcined catalysts. Cobalt reduction was significantly enhanced in the presence of copper. Furthermore, our characterizations indicate the formation of bimetallic Cu-Co particles in the reduced catalysts and enrichment of the surface of bimetallic particles with Cu. The catalytic studies showed dramatic modifications of both the rate and selectivity in the hydrogenation of CO after addition of even small amounts of Cu to supported Co catalysts. The presence of Cu increased the selectivity to alcohols by an order of magnitude and decreased the overall carbon monoxide conversion. Structure-performance correlations suggest that the Cu-Co bimetallic particles may be involved in higher alcohol synthesis. (C) 2011 Elsevier Inc. All rights reserved.