Nonoxidative dehydrogenation of ethylbenzene over TiO2$z.sbnd;ZrO2 catalysts II. The effect of pretreatment on surface properties and catalytic activities

Abstract

Catalytic activities for the nonoxidative dehydrogenation of ethylbenzene were determined for TiO₂ZrO₂ catalysts which had been calcined at temperatures between 550 and 1000 °C. The acidic and basic properties and surface areas of these catalysts were also measured. The change of crystal structure with calcination temperatures was studied by XRD analysis. The maximum of catalytic activity was obtained by calcination at about 650 °C with an equal-molar ratio of TiO₂ and ZrO₂. This high activity may be due to the formation of ZrTiO₄ crystal. The activity of the catalyst was poisoned not only by K₂O but also by H₃BO₃. Based on the effects of pretreatment with H₂, O₂, and steam, structures are proposed for the catalytically active sites. It is concluded that the formation of ZrTiO₄ crystal as well as the amounts of acid and base sites are the major factors affecting the catalytic activity.