We investigated the catalytic oxidation and adsorption of benzene, toluene, and o-xylene (BTX) by using the palladium (Pd)-based catalyst and its pretreated (pre-oxidized and pre-reduced) catalysts. The physico-chemical properties of the catalysts were characterized and confirmed by using several reliable methods such as the Brunauer Emmett Teller (BET) surface area analysis, gravimetric adsorption analysis, light-off curves analysis, and X-ray photoelectron spectroscopy (XPS). The adsorption and catalytic activities of the catalysts were found to be closely connected with the pretreatment methods and temperatures. Especially, the hydrogen treated catalysts with a largely metallic form enhanced the adsorption ability and catalytic activity of toluene compared to that of the parent and air treated catalysts. In addition, the adsorption equilibrium isotherms of BTX on pre-reduced catalyst at three different temperatures were analyzed successfully with the two sites localized Langmuir (L2m) isotherm equation. Moreover, the strong correlations between the catalytic behavior and the adsorption properties of BTX were explained in terms of adsorption affinity, isosteric heat of adsorption, and adsorption energy distributions. (c) 2008 Elsevier B.V. All rights reserved.