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 H2O2 into oxalic acid, formic acid and CO2 within 2 h at 30 °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: 0.8 g L− 1 of catalyst, n (H2O2)/n (phenol) = 15, temperature of 40 °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.

Phenol could be completely oxidized by H2O2 over Cu–Ni–Al hydrotalcite within 2 h at 30 °C, in which phenol was oxidized into p-benzoquinone, then into maleic acid, and finally into oxalic acid, formic acid and CO2.Figure optionsDownload as PowerPoint slideResearch highlights
► The presence of chloride ion promoted markedly the oxidation rate of phenol.
► Phenol was completely oxidized by H2O2 into oxalic acid, formic acid and CO2.
► The HT-like catalyst exhibited high catalytic activity.
► There was an appropriate concentration ratio among catalyst, H2O2 and phenol.