Dehydrogenation of ethylbenzene and ethylcyclohexane over mixed binary oxide catalysts containing titania

Abstract

The binary oxides, combining TiO 2 with the other first period transition metal oxides, were prepared by the coprecipitation method. The acidity, basicity, surface area, and the X-ray diffraction pattern of these binary oxides were measured. The activity of dehydrogenation of ethylbenzene (EB) and ethylcyclohexane (ECHA) was examined by using a pulse reactor and a continuous dilute flow reactor. A good correlation between the activity and the surface acid-base property was found and an acid-base bifunctional mechanism was proposed. It was postulated that EB and ECHA were initially activated by the acid sites of the binary oxides and then underwent the dehydrogenation reaction by the basic sites. The activity of EB dehydrogenation and the activity of ECHA dehydrogenation were compared. The rela tively stronger acid sites, instead of the moderate ones which were suitable for EB dehydrogenation, were needed for ECHA dehydrogenation. The effects of the prereduction of the binary oxides were also studied. The acid-base dehydrogenation activity were decreased by prereduction. However, the decreased activity of acid-base dehydrogenation of ECHA could be compensated by metal dehydrogenation mechanism which was considered to be rather effective for saturated rings.