MODIFICATION OF SELECTIVITY IN THE HYDROGENATION OF CROTONALDEHYDE USING CU/AL2O3 CATALYSTS MODIFIED WITH SULFUR-COMPOUNDS - EFFECT OF SULFUR SOURCE

The hydrogenation of the alpha,beta-unsaturated aldehyde crotonaldehyde has been studied over 5% Cu/Al2O3 and sulphur-modified 5% Cu/Al2O3 catalysts. The range of sulphur compounds included thiophene, thiophane, DMSO, DMS, SO2, and CS2. Following modification, an increase in the selectivity to the unsaturated alcohol, crotyl alcohol, was observed, and although the magnitude of this effect depended on the sulphur compound, the selectivity enhancement is concluded to be a general effect for supported copper catalysts modified by sulphur compounds. The enhancement in selectivity to crotyl alcohol decreases in the following order: thiophene > DMSO approximately thiophane approximately DMS > SO2 approximately CS2 for catalysts examined at constant temperature and crotonaldehyde conversion. The catalytic observations are combined with the results of FTIR spectroscopic characterisation of modified and unmodified Cu/Al2O3 using carbon monoxide as a probe molecule. The origin of the effect is discussed in terms of the formation of modified Cu0 and Cu+ surface sites. (C) 1994 Academic Press, Inc.