Enhancing the catalytic performance of Pt/ZnO in the selective hydrogenation of cinnamaldehyde by Cr addition to the support

An enhancement of the catalytic performance of platinum in the liquid phase hydrogenation of cinnamaldehyde has been achieved by modifying a ZnO support by addition of Cr(III) cations. The addition of chromium improves the structural properties of the support (larger surface area) and increases its reducibility, and resulted in a better Pt dispersion. The presence of chromium in the support enhanced the overall catalytic activity, and improved the high selectivity towards the unsaturated alcohol. The increase of the reduction temperature from 473 K to 623 K produces an impressive decrease in the turnover frequency for Pt/ZnO, whereas this value remains practically unmodified for Pt/Cr-Zn. The higher reduction temperature reduces the overall activity in both catalysts, but improves selectivity towards the unsaturated alcohol. The present 5 wt% Pt/Cr-ZnO catalyst showed the best results (in terms of selectivity) published until now without use of reaction promoters. The improved performance of this catalyst is ascribed to an adequate metal-support interaction and to the higher reducibility of the support that opens the possibility of alloy formation. (C) 2008 Elsevier Inc. All rights reserved.