An effective and recyclable catalyst for hydrogenation of alpha,beta-unsaturated aldehydes into saturated aldehydes in supercritical carbon dioxide

A carbon supported palladium catalyst (Pd/C) is successfully used in selective hydrogenation of alpha,beta-unsaturated aldehydes in scCO(2) and under solventless reaction conditions. The reactions take place very rapidly in scCO(2) and the average turnover frequency values for cinnamaldehyde and crotonaldehyde at 100% conversion maximally reached 3.1 and 11.6 s(-1), respectively. The catalyst can be recycled several times without loss of activity and selectivity. The products (liquid), solvent (scCO(2)) and catalyst (solid) can be easily separated by a simple phase separation process. The present reaction is an ideal green chemical process in the view of industrial applications.