Autoxidation of thiols with cobalt(II)phthalocyanine‐tetra‐sodium sulfonate attached to poly(vinylamine), 6. Immobilized catalysts by crosslinking of poly(vinylamine)

Poly(vinylamine), being both carrier and promotor of the thiol oxidation catalyst cobalt(II)phthalocyanine‐tetra‐sodium sulfonate (CoPc(NaSO 3 ) 4 ), was crosslinked with α,α′‐dichloro‐p‐xylene, thus yielding porous hydrophilic networks. The effects of experimental parameters such as stirring speed, particle size, degree of crosslinking, distribution of catalytic sites (CoPc(NaSO 3 ) 4 ) in the catalyst particles, pH, temperature, and thiol concentration were investigated. Reaction rates observed for the immobilized catalyst system appeared to be 4–30 times lower as compared with the water soluble polymeric catalyst system but still higher than those of the polymer free CoPc(NaSO 3 ) 4 catalyst. At a stirring speed around 3 · 10 3 rpm not the mass transfer from the bulk to the catalyst particles but intra‐particle diffusion limits the reaction rate. Accordingly, an uncrosslinked polymeric catalyst anchored to silica, with catalytic sites situated close to the particle surface, exhibited comparatively high activity, i.e. only four times lower than the soluble polymeric catalyst. In addition, the heterogeneous catalyst systems showed resemblance in kinetic behaviour with the soluble polymeric thiol oxidation catalyst.