A comparison of Al-Fe and Zr-Fe pillared clays for catalytic wet peroxide oxidation

Catalysts based on pillared clays with Al, Zr and Al-Fe and Zr-Fe have been synthesized from a commercial bentonite and tested for catalytic wet peroxide oxidation (CWPO) using phenol as target compound at 298 K. The Al-Fe pillared clay showed a higher activity than the Zr-Fe one for phenol oxidation, although the second was more active for H2O2 decomposition. Fairly different values of apparent activation energy were obtained for this last reaction with these two types of catalysts, suggesting that the prevailing pathway in H2O2 decomposition is different. The higher activity of the Al-Fe pillared clay for CWPO suggests that this catalyst favours the generation of OH radicals, whereas with the Zr-Fe one H2O2 decomposes predominantly to O2 which has a low oxidation capacity at the mild operating conditions commonly used in Fenton oxidation.