Mechanistic Aspects of Ethylbenzene Dehydrogenation with CO₂ over K₂O/B₂O₃ -TiO₂ - ZrO₂ Bi-Functional Catalysts

Abstract

TiO 2 -ZrO 2 bi-functional catalysts were prepared by co-precipitation method using aqueous NH 3 solution as a hydrolyzing agent. Either K 2 O promoter or B 2 O 3 promoter has been deposited 60% TiO 2 - ZrO 2 by wet-impregnation techniques. The catalytic activity of both K 2 O promoted and B 2 O 3 promoted TiO 2 -ZrO 2 acid base bi-functional catalysts has been studied for the oxidative dehydrogenation of ethylbenzene in the presence of CO 2 . The higher conversion of ethylbenzene and higher selectivity of styrene has been obtained on the K 2 O promoted TiO 2 -ZrO 2 catalysts. On the other hand, B 2 O 3 promoted TiO 2 - ZrO 2 catalysts exhibited lower catalytic activity than those of K 2 O promoted TiO 2 - ZrO 2 catalysts. In the mechanistic point of view both K 2 O promoted TiO 2 -ZrO 2 catalysts and B 2 O 3 promoted TiO 2 - ZrO 2 catalysts following the different pathways. This synergistic promotional effects of K 2 O and CO 2 enhanced the selectivity of styrene (98 - 99%) by sustaining the higher conversions of ethylbenzene (60 -65%).