Ordered mesoporous alumina-supported metal oxides as Fenton-like catalysts towards the treatment of phenolic wastewaters

N. INCHAURRONDO; C. DI LUCA; P.HAURE; R. PARRA

Madrid

Simposio; 3rd International Symposium on Catalysis for Clean Energy and Sustainable Chemistry; 2016

Instituto de Catálisis y Petroleoquímica ICP-CSIC

Advanced Oxidation Processes (AOP?s) are aqueous phase oxidation methods based on the intermediacy of hydroxyl radicals, leading to the abatement of organic pollutants at mild reaction conditions. Among different AOP?s technologies, one interesting alternative is the Catalytic Wet Hydrogen Peroxide Oxidation (CWHPO). The so-called heterogeneous Fenton-like systems use a solid catalyst in the presence of hydrogen peroxide as oxidizing agent. These solid catalysts consist in transition metal species (primarily iron, but not exclusively) immobilized over different porous supports. Among them, alumina based systems are useful as catalysts or co-catalysts due to a favorable combination of textural properties, acid?base characteristics and on the degree of hydration and hydroxylation of the surface [1,2]. The sol-gel processes are widely used as bottom-up methods for the development of nanocatalysts based in metal oxides via a soft-chemistry route. From this basis, the Evaporation-Induced Self-Assembly (EISA) allows the development of mesoporous alumina with fine-tuned structural properties (high surface area and narrow pore size distribution) and high surface acidity [3]. This one-pot strategy consists in the incorporation of molecular metal precursors into a solution of a non-ionic surfactant (as structure-directing agent) by using a strict adjustment of molar ratios between the reactants. Among non-conventional methods of catalysts preparation, direct incorporation of active components during the synthesis of a porous matrix could provide a useful strategy to improve both active sites dispersion and metal-support interactions. In recent studies, it was demonstrated that direct inclusion of iron during the synthesis of SBA-15 via co-condensation route resulted in an enhancement of catalyst stability when compared with samples prepared by conventional impregnation [4]. Whereas the incorporation of different metal species during the synthesis of mesoporous silica is well documented, SiO2 based systems do not provide active sites mainly due to its low pHPZC [1,2]. As counterpart, only few works consider the inclusion of metal oxides into mesoporous alumina networks mainly due to a major difficulty in controlling the rates of hydrolysis-condensation of the Al precursors [2].In this context, the goal of the present work is to study the addition of Fe, Cu, Ce species during the synthesis of mesoporous alumina through a sol?gel process via EISA methodology and to investigate the catalytic feasibility of these materials in the CWHPO of model organic pollutants such as phenol.