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. Prelimina ry kinetic studies were performed at 333 K in autoclave, at pressure of 2 a rm in pure oxygen. Under these conditions, small amounts of benzoic acid we re detected with the monometallic Pd pumice being the most active catalyst. The reaction was also carried out under flowing oxygen at atmospheric pres sure and at 348 K. Under these conditions. the selectivity to benzaldehyde was 100%. The catalytic activity of the catalysts was measured after differ ent oxidation and reduction treatments at high temperature. In addition, tw o mechanical mixtures of pretreated Pd and Ag monometallic samples were tes ted. The structural data. (XRD, XPS, EXAFS) along with the catalytic result s would indicate that Ag-0 and Pd-0 species are the catalytic sites acting with certain synergism. (C) 2001 Elsevier Science B.V. All rights reserved.