Factors affecting the conversion and selectivity of ethylbenzene dehydrogenation over commercial catalysts

The dehydrogenation of ethylbenzene (EB) over a potassium-promoted iron oxide catalyst was investigated at temperatures ranging from 590 to 639°C under atmospheric pressure. Fresh and used commercial catalysts from Tabriz Petrochemical Company were studied. The used catalyst had been continuously operated for two years under severe conditions (LHSV = 1 h-1, T = 610°C, mass ratio of steam to ethylbenzene = 1.2, P = 1.2 atm). The catalyst activity tests were performed in a lab-scale continuous fixed bed reactor, maintained at fixed temperature using an electrically heated furnace. For fresh catalyst the yield of styrene increased with a decrease in LHSV and reached its highest value (79.2%) at 0.48 h-1 and T=627°C. The yield of styrene increased with increasing reaction temperature, but the selectivity to styrene slightly decreased with an increase in reaction temperature from 591 to 639 C. The selectivity to styrene increased a little with an increase in the H2O/ethylbenzene ratio. By comparing the results for the fresh and used catalysts at the same experimental conditions, it was found that the selectivity of styrene for the used catalyst is higher than that for the fresh catalyst. It was also found that the main cause of the catalyst deactivation is the coke deposition which was lead to 22% reduction in the catalyst activity after only 12 h.

کلیدواژه ها:

styrene ، dehydrogenation ، catalyst ، iron oxide ، conversion