AUTOXIDATION OF MERCAPTANS PROMOTED BY A BIFUNCTIONAL CATALYST PREPARED BY POLYMER ATTACHMENT OF COBALT-PHTHALOCYANINE

An effective catalyst for the autoxidation of mercaptans should possess oxidation sites and basic sites in cooperative interaction. Such a bifunctional catalyst was prepared using poly(vinylamine), that acts both as supplier of basic sites and as a carrier for the oxidation catalyst cobalt(II)-4,4′,4″,4′- tetracarboxyphthalocyanine. Polymer attachment of the cobalt-phthalocyanine was achieved by complexation through polymeric amine groups (catalyst I), as well as by formation of a peptide linkage between the phthalocyanine ring system and the polymeric carrier (catalyst II). Both methods of coupling provided bifunctional catalysts, not requiring additional base, with extremely high activities. The presence of low amounts of alkaline base did not influence the initial activity appreciably, but it had a positive influence on the stability of the catalysts by allowing in situ neutralization of acidic by-products. However, addition of higher amounts of alkaline base resulted in a loss of activity ascribed to a reduction of the local substrate concentration. In the case of catalyst I this loss of activity is more pronounced, due to rupture of the polymer/cobalt-phthalocyanine complex. It was demonstrated that the polymeric catalysts can also be applied in toluene, provided that small amounts of water are present. Most probably, water plays an important role in the proton transfer, which is an essential feature of the autoxidation process. © 1978.