Crotonaldehyde hydrogenation on Ir supported catalysts

Iridium supported catalysts prepared by the sol-gel and impregnation method s have been studied in the vapour-phase hydrogenation of crotonaldehyde. Th e influence of different preparation variables on the surface and catalytic properties was analysed. It was found that the porosity of the support has an effect on the selectivity to the unsaturated alcohol and the presence o f partially reducible supports such as ZrO2 and TiO2 increases the selectiv ity to crotyl alcohol. This increase may be attributed to an enhancement of the polarisation of the C=O bond as a result of surface decoration of the metal component. The presence of chlorine ions in the metal-support interfa cial region also allows, in a certain extension, a polarisation of the carb onyl bond. The effect of the reaction temperature has also been studied. It was found that a decrease in the reaction temperature led to a decrease in the crotonaldehyde conversion and in an improvement on the selectivity of the allylic alcohol. (C) 2000 Elsevier Science B.V. All rights reserved.