EFFECT OF PROMOTER ON SELECTIVE HYDROGENATION OF ALPHA,BETA-UNSATURATED ALDEHYDES OVER COBALT BORIDES

The selective hydrogenation of alpha,beta-unsaturated aldehyde was stu died over cobalt borides. The effects of Fe, Cu, Sn, Mo and Th additio ns were examined for the hydrogenation of cinnamaldehyde. Fe and Sn di d not promote the formation of unsaturated alcohol as expected. Molybd enum effectively promoted the overall rate and the yield of unsaturate d alcohol. Thorium not only promoted the activity, but also slightly p romoted the selectivity. The promotional effects of molybdenum and tho rium were attributed to the affinity between carbonyl and promoter ion s. This model is very similar to that proposed for their promotional e ffects on group VIII metals in CO hydrogenation. A lower reactant conc entration, a higher pressure and temperature (in the range of 373-403 K) favored the formation of unsaturated alcohol. A protic solvent such as ethanol or isopropanol is preferable to an aprotic solvent for thi s reaction. The addition of an appropriate amount of water to ethanol increased the rate of reaction by 100%.