Dehydrogenation of ethylbenzene in the presence of CO2 over catalysts prepared from hydrotalcite-like precursors

Dehydrogenation of ethylbenzene to styrene in the presence of CO2 was investigated over a series of catalysts prepared by calcination of hydrotalcite-like compounds. Mg/Fe mixed oxide catalysts prepared in this way have high specific surface areas and are active for the dehydrogenation reaction. Incorporation of Al3+, Ni2+, Co2+, and Zn2+ into the hydrotalcite-like precursors may further enhance the catalytic activity of the calcined catalysts. The Mg/Zn/Al/Fe catalyst affords the highest ethylbenzene conversion of 53.8% and a styrene selectivity of 96.7% at 773 K. The high catalytic activity and stability of the Mg/Zn/Al/Fe catalyst are attributed to the presence of a larger amount of stronger acid sites and a moderate amount of base sites on the catalyst. The temperature-programmed reduction studies show that the reduction of iron oxide species in the catalysts is retarded after incorporation of Zn2+ and Al3+. The higher content of iron oxide species in the catalyst system under reaction conditions favors the redox. cycle in the reaction and also enhances the dehydrogenation activity. (C) 2004 Elsevier B.V. All rights reserved.