The use of palladium nanoparticles supported on MCM-41 mesoporous molecular sieves in Heck reaction: A comparison of basic and neutral supports
Abstract
Bifunctional supported catalysts were prepared by grafting of chemically reduced palladium nanoparticles onto basic MCM-41 type solid supports. The supports were obtained by ion-exchange with Cs+ or K+ ions from both in-synthesis and post-synthesis Al-doped mesoporous molecular sieves MCM-41 (i.e. (Al)MCM-41 and Al-grafted MCM-41).
For a comparison, Pd@Cs+-exchanged zeolite Y and the non-basic Pd@MCM-41 catalyst were also prepared. All supported catalysts were tested in Heck reaction of butyl acrylate and bromobenzene to give n-butyl cinnamate.
Catalysts Pd@Cs+-(Al)MCM-41 and Pd@Cs+-Al-grafted MCM-41 proved to be superior to the analogous catalysts reported in the literature in terms of turnover number and turnover frequency. Most active, however, were catalytic systems obtained from combination of the simple, non-basic Pd@MCM-41 with an external base, which gave the coupling product in 33% after 20 h at 160 degrees C in N,N-dimethylacetamide in the presence of sodium acetate and at 1 mol.% palladium loading.