Vapor phase hydrogenation of phenol over silica supported Pd and Pd-Yb catalysts

The catalytic activity/selectivity of a 5% w/w Pd/SiO2 catalyst prepared by Pd(NO3)2 impregnation has been compared with that delivered by 5% w/w Pd/SiO2 and Pd-Yb/SiO2 prepared from Pd(C2H3O2)(2) and {(DMF)(10)Yb-2[Pd(CN)(4)](3)}(infinity) precursors, respectively; phenol hydrogenation (T = 423 K) was used as a test reaction. The activated catalysts have been characterized by HRTEM/EDX; differences in activity are related to the TEM derived Pd particle size distribution. Incorporation of Yb resulted in an appreciable enhancement of both phenol conversion and the overall yield of cyclohexanone, an effect that is attributed to electron donation from Yb to the active Pd centers. (C) 2002 Elsevier Science B.V. All rights reserved.