Catalytic wet peroxide oxidation of phenol over pillared clays containing iron or copper species

The catalytic wet oxidation of phenol by hydrogen peroxide in the presence of oxygen is catalysed, at room temperature, by copper or iron homogeneous species at pH 5 or 3.5, respectively. In such conditions phenol mild oxidation is mainly observed, the total phenol oxidation to CO₂ (TOC abatement) not exceeding 20 %. In similar experimental conditions, Fe, Al or Cu, Al pillared clays (FAZA or CAZA) are much more active, the phenol or the TOC conversion being directly related to the iron or copper content. Moreover, in the presence of iron containing pillared clay (FAZA), the TOC abatement can reach 80 % at 70 °C, with only a H₂O₂ stoichiometric excess equal to 1.5. The low iron leaching (less than 0.2 % of the total amount of iron in the catalyst) observed after a standard experiment (4 h) shows that the FAZA catalyst is highly stable in water media and could be used several consecutive times. These properties could result in the iron species stabilization in the interlamellar space of the pillared clays both by bonding with the Al pillars (60 % of the iron species) or as oxide clusters dispersed between the clay layers.