The oxidation of 1,2-dichlorobenzene (o-DCB) has been examined over Co-HMOR, Pd/Co-HMOR, Co-SZ and Pd/Co-SZ under dry and wet conditions. Under dry conditions, Pd/Co-SZ was the most active catalyst. However, in the presence of water Pd/Co-HMOR exhibits a significant activity while Pd/Co-SZ was not affected. Besides, by-product formation such as polychlorinated compounds decreased on both catalyst types under wet conditions. Catalysts were characterized by XRD, BET, TGA, TPR, and NH3-temperature programmed desorption (TPD). The sulfation process greatly increased the surface areas of zirconia catalysts. No significant changes in the H-2-TPR profiles of Co-SZ and Pd/Co-SZ under dry and wet conditions were observed while Co2+ ions at exchange positions of mordenite decreased on used mordenite catalysts. In spite of a higher total acidity (NH3-TPD) of mordenite catalysts compared to sulfated zirconia catalysts, zirconia-sulfated catalysts exhibited higher activity when dry feeds were used. (c) 2007 Elsevier B.V. All rights reserved.