Insights into promotional effects for ethylbenzene dehydrogenation to styrene with steam over Fe-K, Fe-K-Ce and Fe-K-Ce-Mo mixed oxide catalysts

Abstract

In ethylbenzene dehydrogenation industrial applications, Fe-K based especially Fe-K-Ce and Fe-K-Ce-Mo based mixed oxides are the most widely used catalysts. But the corresponding reaction mechanism for promoters are still unclear. Herein, the model Fe-K, Fe-K-Ce, Fe-K-Ce-Mo catalysts were prepared by wet granulation method and the insights into promotional effects were clarified by using various characterizations and in situ DRIFTs studies. Our results suggest that Ce addition improved catalytic activity and Mo modification increased styrene selectivity. The Fe-K-Ce showed outstanding redox ability profited from abundant active oxygen species and reducible species. The Fe-K-Ce-Mo achieved optimal activity and selectivity because of the moderate redox behavior. The ethylbenzene adsorption at low temperature form coke deposits and enhanced oxidizing ability of modified catalysts facilitate CO2 producing thus improve catalyst coke resistance. Besides, the activation induction periods of modified catalysts were shortened based on accelerated formation of main active phase and redox equilibrium. Moreover, the steam significantly promoted styrene species generation and further shorten activation induction periods, which was involved in real reactions instead of just eliminating coke.