Nano-size particles of palladium intermetallic compounds as catalysts for oxidative acetoxylation

Fine particles of palladium containing intermetallic compounds (IMCs) were prepared on the surface of silica gel and their catalytic properties for the oxidative acetoxylation of toluene and 1,3-butadiene (BD) were investigated. Intermetallic compounds were prepared on silica by the successive impregnation using aqueous solutions of palladium dichloride and a compound of the second metal. Through the reduction in hydrogen at proper temperatures, particles of Pd5Ge, Pd2Ge, PdZn, Pd5Ga2, PdTe, PdIn, Pd3Bi, Pd3Pb, PdCd and Pd3Tl were formed with crystallite diameters below 7 nm. PdFe particles were obtained by chemical vapor deposition (CVD) of ferrocene on Pd/SiO2 and the subsequent hydrogen treatment. The catalytic properties of these supported intermetallic compounds were examined for the oxidative acetoxylation reactions. In the case of toluene acetoxylation, the high yield of benzyl acetate (BA) was obtained on Pd3Bi/SiO2, Pd3Pb/SiO2, PdCd/SiO2 and Pd3Tl/SiO2, while Pd/SiO2 predominantly catalyzed the total oxidation into carbon dioxide. In the case of 1,3-butadiene acetoxylation, Pd3Tl/SiO2 gave a high yield of 1,4-diacetoxy-2-butene. (C) 2003 Elsevier B.V. All rights reserved.