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

Abstract

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, 1H 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.