Liquid phase selective oxidation of benzyl alcohol over Pd-Ag catalysts supported on pumice

Selective oxidation of benzyl alcohol to benzaldehyde was carried out over pumice supported bimetallic and monometallic Pd and Ag catalysts. Preliminary kinetic studies were performed at 333K in autoclave, at pressure of 2 atm in pure oxygen. Under these conditions, small amounts of benzoic acid were detected with the monometallic Pd pumice being the most active catalyst. The reaction was also carried out under flowing oxygen at atmospheric pressure and at 348 K. Under these conditions, the selectivity to benzaldehyde was 100%. The catalytic activity of the catalysts was measured after different oxidation and reduction treatments at high temperature. In addition, twomechanical mixtures of pretreated Pd and Ag monometallic samples were tested. The structural data (XRD, XPS, EXAFS) along with the catalytic results would indicate that Ag0 and Pd0 species are the catalytic sites acting with certain synergism.