The use of palladium nanoparticles supported with MCM-41 and basic (Al)MCM-41 mesoporous sieves in microwave-assisted Heck reaction

A series of supported catalysts has been obtained by grafting of chemically generated palladium nanoparticles onto basic, Cs+ ion-exchanged molecular sieves (Al)MCM-41 and onto the non-basic, parent material MCM-41. Catalytic activity of the catalysts has been investigated in the Heck reaction between bromobenzene and butyl acrylate under microwave irradiation. The activity of the bifunctional catalysts (Pd@Cs+-(Al)MCM-41) and the activity of Pd@MCM-41 combined with sodium acetate as an external base were considerably higher under microwave irradiation than activities observed for the same catalytic systems under the conventional heating. The Pd@MCM-41/NaOAc system showed higher conversions than the bifunctional catalysts presumably due to a different nature and accessible amount of the base. On the other hand, microwave irradiation seems to increase the rate of aggregation of the metallic particles and thus also catalyst deactivation as compared with the usual heating.