STUDIES OF HIGH-SURFACE-AREA PT MOO3 AND PT/WO3 CATALYSTS FOR SELECTIVE HYDROGENATION REACTIONS - II - REACTIONS OF ACROLEIN AND ALLYL ALCOHOL/

The vapor-phase hydrogenation of acrolein, as a model molecule represe nting the alpha,beta-unsaturated aldehydes, was studied over Pt powder and Pt dispersed on SiO2, Al2O3 and ultrafine MoO3 and WO3 particles. The hydrogenation and isomerization of allyl alcohol were also invest igated to obtain additional information about the effects of the suppo rts and the network of these reactions. In the hydrogenation of acrole in, allyl alcohol was significantly produced only over Pt/MoO3 and Pt/ WO3 catalysts previously reduced in the temperature range 673-773 K. T his supports the proposal that adlineation sites created at the Pt-MoO 3 and Pt-WO3 interfaces following a reduction at high temperature are responsible for the activation of carbonyl bonds. Also these adlineati on sites, which contain electron-deficient cations resulting from a pa rtial reduction of the oxide support, favor the isomerization of allyl alcohol to propanal at the expense of its hydrogenation to propanol. By contrast, for prereduction temperatures below ca. 573 K, the cataly tic behavior of Pt/MoO3 and Pt/WO3 in the two reaction tests was not d istinctly different from that of conventional Pt catalysts, which sugg ests that the molybdenum and tungsten hydrogen bronze supports do not markedly influence the catalytic properties of Pt catalysts. (C) 1997 Elsevier Science B.V.