Dechlorination of tetrachloro-o-benzoquinone by ozonation catalyzed by cesium loaded metal oxides

Ozone initiated oxidation of tetrachloro-o-benzoquinone (3,4,5,6-Tetrachlorocyclohexa-3,5-diene-1,2-dione, TCCD) in aqueous system catalyzed by different loadings of cesium oxide supported on metal oxides namely; Al2O3, SiO2 and TiO2 was investigated. Catalyst materials were characterized using different surface techniques including Raman, FT-IR, BET, SEM, TEM, ICP, TPD and XRD. XRD showed that cesium is in three different phases on the surface of the catalysts; and SEM and SEM-EDX indicated that cesium is well dispersed on the surface of the supports. Catalyst testing was done employing varying ozone molar ratios from 1 to 3 in the oxygen stream in a semi-batch reactor. 2,3-Dichloro-4,5-dioxohex-2-enedioic acid (DCA) was an intermediate and 2,3-dioxosuccinic acid (DSA) and oxalic acid (OA) were the main oxidation by-products. The oxidation products were characterized and confirmed by IR, H-1 NMR and Mass spectral data. The product distribution was dependent on the acidity of the supports. Among all the catalysts while 5% Cs/TiO2 showed good activity, 1% Cs/SiO2 showed relatively poor catalytic activity. (C) 2013 Elsevier B.V. All rights reserved.