The selective formation of unsaturated alcohols by hydrogenation of alpha,beta-unsaturated aldehydes in supercritical carbon dioxide using unpromotedPt/Al2O3 catalyst

When alpha,beta-unsaturated aldehydes are reduced by hydrogen in supercriti cal carbon dioxide using an unmodified Pt/Al2O3 catalyst, unsaturated alcoh ols are highly selectively produced, in contrast to previous results with o rganic solvents in which such a selective hydrogenation is difficult to ach ieve with monometallic Pt catalysts. The selectivity of unsaturated alcohol s depends mainly on pressure of carbon dioxide while the conversion depends on both carbon dioxide and hydrogen pressures. The selectivity increases w ith increasing pressure and then does not change so much at higher pressure s.