Liquid phase hydroxylation of benzene over Cu-containing ternary hydrotalcites

Abstract

One step liquid phase hydroxylation of benzene to phenol over ternary hydrotalcites of general formula CuM(II)M(III)–HT, where M(II) = Mg, Co, Ni and Zn and M(III) = Al, Fe and Cr was carried out in the temperature range 30–80 °C using pyridine as solvent and H2O2 as oxidant. Influence of various reaction parameters, such as reaction temperature, substrate:catalyst ratio, substrate weight, volume of the solvent, calcination temperature and reaction time were studied. Among the catalysts screened, CuCoAl–HT and CuNiAl–HT with (Cu + Co(or Ni))/Al = 3.0 and Cu/Co(or Ni) = 3.0 showed maximum activity with nearly 100% selectivity of phenol. The hydroxyl radical generated upon interaction of catalyst with oxidant is believed to be the active species involved in this reaction.