Dehydrogenation of ethylbenzene in the presence of CO2 over an alumina-supported iron oxide catalyst

The dehydrogenation of ethylbenzene (EB) in the presence Of CO2 over an alumina-supported iron oxide catalyst was investigated at temperatures ranging from 798 to 873 K under atmospheric pressure. The yield of styrene increased with an increase in W/F and reached its highest value (74%) at a W/F of around 40 g-cat min/mmol-EB, where the selectivity to styrene was 96%. The highest yield of styrene in the dehydrogenation in the presence Of CO2 was higher than the yield of styrene at equilibrium of the simple dehydrogenation in the absence Of CO2, probably because CO2 was involved in the dehydrogenation and/or in the reaction with H-2 produced in the dehydrogenation. The yield of styrene increased with increasing reaction temperature, but the selectivity to styrene slightly decreased with an increase in reaction temperature from 848 to 873 K. The yield of styrene was the highest at CO2/ethylbenzene ratios ranging from 5 to 10. The selectivity to styrene increased a little with an increase in the CO2/ethylbenzene ratio from 15 to 30. The amount of carbonaceous deposits on the catalyst during the dehydrogenation in the presence Of CO2 increased with an increase in the reaction temperature and in the CO2/ethylbenzene ratio. The decrease in the catalyst activity with time on stream was smaller in the dehydrogenation in the presence Of CO2 than in the dehydrogenation in the absence Of CO2. (C) 2002 Elsevier Science B.V. All rights reserved.