MECHANISM OF THE WACKER OXIDATION OF ALKENES OVER CU-PD-EXCHANGED Y-ZEOLITES

The catalytic potential of CuPd zeolites with faujasite topology in th e Wacker oxidation of 1-alkenes with dioxygen is reported and compared with that of a homogeneous PdCl2-CuCl2 salt solution. The influence o f water, oxygen, and alkene partial pressure on the rate of oxidation and the use of different alkenes and perdeuterated ethene as substrate allowed to establish similarities between the heterogeneous and homog enous system as well as specific zeolite effects. In situ IR and ESR s pectroscopy of a working catalyst allowed to propose an active site co nsisting of a trinuclear Cu-O-Pd-O-Cu cationic complex and a catalytic cycle for the Wacker oxidation in which the reoxidation of Cu+ by dio xygen or of Pd-0 by zeolite Cu2+ is rate determining. Diagnostic probi ng of the phenomena with CO in IR and ESR confirmed this picture.