Palladium–copper-exchanged Y type zeolites: a true heterogeneous Wacker catalyst

Evidence is presented that faujasite-type zeolites with specific Si : Al framework ratios exchanged with Pd(NH3)42+ and Cu2+, catalyse the oxidation of ethylene into acetaldehyde, in exactly the same way as the homogeneous Wacker system [PdII and CuII in concentrated chloride solution]; the active centre is found to be a partially ammoniated PdII ion, most probably PdII(NH3)2, which itself belongs to an electron transfer chain consisting of the alkene reagent, the faujasite encaged PdII/Pd0 and CuII/CuI redox couples and dioxygen.