Selective hydrogenation of α,β-unsaturated ketones to α,β-unsaturated alcohols on gold-supported catalysts

The liquid-phase reduction of α,β-unsaturated ketones [trans,4-phenyl,3-buten,2-one (benzalacetone C6H5CHCHCOCH3), 4-methyl,3-penten,2-one (CH3)2CCHCOCH3, and 3-penten,2-one CH3CHCHCOCH3] to the corresponding α,β-unsaturated alcohols has been investigated on gold-supported catalysts. Au/Fe2O3 and Au/Al2O3 have been prepared by coprecipitation and deposition-precipitation. The catalytic behavior of a Au/Fe2O3 “reference” catalyst supplied by the World Gold Council has been also investigated. In the hydrogenation of benzalacetone and 4-methyl,3-penten,2-one on the “homemade” Au/Fe2O3 catalysts the unsaturated alcohol is the main reaction product. Chemoselectivity higher than 60% was achieved. On Au/Al2O3, the selectivity is 10%. It is noteworthy that within the gold supported on iron oxide samples, the reference catalyst shows the lowest selectivity toward the formation of the unsaturated alcohol. In the hydrogenation of 3-penten,-2-one on the homemade Au/Fe2O3, the saturated ketone is the main reaction product and the selectivity toward the formation of the unsaturated alcohol is 15% at conversion >90%. It is likely that the absence of bulky substituents on the conjugated CC double bond favors its adsorption on the catalytic sites, leading to the formation of the saturated carbonyl compounds as the main reaction product. A detailed characterization of the investigated catalysts by TEM and XRD is also reported.