Catalytic wet peroxide oxidation of phenol over Cu–Ni–Al hydrotalcite

Liquid phase catalytic oxidation of phenol was carried out over Cu-Ni-Al hydrotalcite at ambient temperature and pressure using hydrogen peroxide as oxidant. The results showed that the hydrotalcite catalyst had high catalytic activity, where phenol could be completely oxidized by H(2)O(2) into oxalic acid, formic acid and CO(2) within 2 h at 30 degrees C. The catalytic oxidation process was zero-order kinetics with an activation energy of 61.5 kJ mol(-1). A feasible reaction system could be proposed as follows: 0.8g L(-1) of catalyst, n (H(2)O(2))/n (phenol) = 15, temperature of 40 degrees C, 2.66 mM of phenol and time of 2 h. Furthermore, it was found that the presence of inorganic chlorides promoted markedly the oxidation rate of phenol, probably due to the formation of intermediate products containing chlorine such as quinones and/or radicals. (C) 2011 Elsevier B.V. All rights reserved.