By varying the composition of TiO2 and ZrO2, various TiO2,-ZrO2, mixed oxide catalysts were prepared by co-precipitation method using ammonium hydroxide as a hydrolyzing agent. Similarly, TiO2 and ZrO2 isolated oxides were also prepared for the purpose of comparison. 60 mol% TiO2, + 40 mol% ZrO2 mixed oxide catalyst (here after simply termed as TiO2-ZrO2) was impregnated with different amounts of potassium oxide (K2O). These catalysts were characterized by BET surface area, X-ray diffraction (XRD) and temperature programmed desorption of NH3. K2O/TiO2-ZrO2 catalysts exhibited high performance towards the selective conversion of ethylbenzene into styrene in the presence of CO2, wherein K2O improved the conversion of ethylbenzene and selectivity of styrene acting as a basic promoter, similarly CO2 enhanced both conversion and selectivity acting as an oxidant as well as a diluent. The unified promotional effects of K2O and CO2 improved the conversion of ethylbenzene up to 60-65% at 95-99% selectivity levels of styrene. (c) 2006 Elsevier B.V. All rights reserved.