Ethylbenzene to styrene in the presence of carbon dioxide over zirconia

ZrO2 itself was found be active for the dehydrogenation of ethylbenzene, es pecially in the presence of CO2, which was aimed to be utilized as an oxida nt. This positive effect of CO2 was highly dependent on the crystalline pha ses of zirconia. The higher the tetragonal phase contained in ZrO2, the hig her the ethylbenzene conversion and styrene selectivity that were obtained. Highly tetragonal ZrO2 was more active in oxidative dehydrogenation than m onoclinic ZrO2. The differences of catalytic activities could be ascribed t o the differences of the surface area and CO2 affinity related with surface basicity.