Chemoselective hydrogenation of –C=O bond in multiple unsaturated compounds over metals supported on mesoporous materials

Liquid-phase hydrogenation of crotonaldehyde in non-polar and polar solvents was studied onmonometallic Pd, Pt, Ir, Re catalysts using mesoporous Sibunit and Al2O3 as supports. In the presenceof Pd the -C=C- bond of crotonaldehyde was preferably hydrogenated to form butanal, while butanaland crotyl alcohol are formed over Ir catalysts. Crotonaldehyde hydrogenation in 1,4-dioxane did notexhibit further butanal to butanol hydrogenation. Application of Re as a catalyst leads to formation ofcrotyl alcohol, with activity being, however, twofold lower than of Ir catalysts. Pt/C is almost inactive inthe hydrogenation of crotonaldehyde. Formation of crotyl alcohol occurs most efficiently over Ir/Al2O3in aprotic nonpolar solvents (decane), with selectivity to crotyl alcohol increasing with temperatureshowing 30% at 25% conversion under 180 °C and hydrogen pressure 0.84 MPa. Crotonaldehydehydrogenation in a polar protonic solvent (ethanol) results in butanal acetalization.