PALLADIUM-CATALYZED BENZYLIC ACETOXYLATION OF TOLUENE

The acetoxylation of toluene to benzyl acetate was found to be a purely heterogeneous catalyzed reaction which occurred on supported metallic palladium particles or on suspended palladium particles in the absence of a carrier material. An optimized catalytic system prepared in situ was found to be composed of [Pd(OAC)2, Sn(octoate)2, KOAc and Norit PKDA 1-3 charcoal] where the Pd/Sn/K mole ratio was 1/5/10. High toluene conversion (100%) and benzyl acetate selectivity (77%) were obtained after 180 minutes at 100-degrees-C. The addition of Sn2+, K+ and charcoal all led to an increased rate of Pd(OAc)2 decomposition to metallic palladium. The addition of tin(II) lowered the activation energy of the reaction by over 25%. Tin(II) may also serve as a reducing agent in the initial stages of Pd(O) particle formation. The addition of several potential co-catalysts other than tin, some of which possessed accessible redox potentials, had no effect or a negative effect on catalytic activity. The addition of various acetate counter ions had little effect on catalytic activity with the exceptions of K+ and Rb+.