Tetravalent metal phosphates form highly insoluble inorganic polymers and act as catalysts in some oxidative reactions. In the present work, a-amorphous zirconium, tin, titanium, zirconium tungstate (acidic and basic form), crystalline vanadyl, fibrous crystalline cerium and pellicular zirconium phosphates, were prepared and evaluated as catalysts, for the hydroxylation of phenol and 2-naphthol by hydrogen peroxide, in acetic acid. Oxidation of phenol yielded hydroquinone, catechol, cis,cis-muconic and cis,trans-muconic acids, depending on the catalyst. All oxidations of 2-naphthol produced 4-(2-hydroxy-1-naphthyl)-1,2-naphthoquinone but reaction with crystalline vanadyl phosphate also resulted in the formation of 1,1'-bi(2-naphthol). (C) 2002 Elsevier Science B.V. All rights reserved.