DECOMPOSITION OF P-CHLOROPHENOL BY WET OXIDATION IN THE PRESENCE OF SUPPORTED NOBLE-METALS CATALYSTS

Decomposition of p-chlorophenol (P-CP) was carried out at 150 degrees C under an oxygen pressure of 0.3 MPa in aqueous solutions, and the effect of noble metals supported on alumina or titania was studied. The decomposition of P-CP was accelerated by the addition of all the catalysts except silver. The activites of the catalysts were in the order of Pt much greater than Pd>Ru>Rh>Ag. In the case of 5% platinum supported on alumina, the conversion of p-CP and reduction in TOC after 30 min were 90% and 89%, respectively, indicating that p-CP was mainly decomposed to give carbon dioxide and water. The effects of the platinum supported on various titania on the decomposition of p-CP and on the reduction in TOC were studied. The rate of the reduction was found to be higher on the catalyst with anatase-type titania than that with rutile-type one. We also found that the catalytic activity was increased with decreasing sizes of titania. By-products formed during oxidation of p-CP were mainly organic acids, such as maleic acid, malonic acid, acetic acid, and chloroacetic acid. Most of these intermediate products were further decomposed ata-considerably high rate. The decomposition of P-CP was supposed to proceed via free radical reaction, as well as hydrolysis and decarboxylation.