The catalytic oxidation of hydroquinone: influence of surface properties of polymeric catalysts with aminoguanidyl ligand on catalytic properties

The heterogenized catalysts were prepared by aminolysis of nitrile groups in acrylonitrile, vinyl acetate and divinylbenzene terpolymer using aminoguanidine bicarbonate and by a subsequent complexation reaction with copper(II) nitrate. To study the catalytic activity of these catalysts, the model oxidation reaction of hydroquinone to p-benzoquinone by hydrogen peroxide was carried out. Under optimal conditions only the main product, i.e. p-benzoquinone (yield 95%) was obtained after 60 min. The existence of free, i.e. uncomplexed groups in active center environment is necessary to use the Cu(II)–resin complexes as oxidation catalysts. The optimal ratio of uncomplexed aminoguanidyl groups to carboxyl group concentration was about 0.6 for the Cu(II) ion loading in the range of 0.26–0.41 mmol/g and 0.7 for the Cu(II) loading in the range of 0.16–0.26 mmol/g.