Ethylbenzene dehydrogenation in the presence of carbon dioxide over alumina supported catalysts

The dehydrogenation of ethylbenzene to styrene was performed in the presence of carbon dioxide instead of steam over a series of alumina supported catalysts, which was believed to be an energy-saving and environmentally friendly process. The effects of active components, promoters, textural properties and other preparation parameters on the catalyst behaviors were examined. The results indicated that the conversion of ethylbenzene could be greatly improved by the reaction coupling due to the simultaneous elimination of hydrogen produced from the dehydrogenation, and vanadium supported on alumina with chromium as promoter was suggested to be promising catalysts. With the catalyst VCr/Al2O3, high ethylbenzene conversion (about 50%) and selectivity to styrene (95–99%) at lower temperature (550 °C) was achieved with reasonable stability (>70 h). The main cause of catalyst deactivation is the coke deposition, which may be alleviated in the presence of carbon dioxide. The catalytic activity of V/Al2O3 can be resumed completely after burning the coke by air or diluted air. Moreover, the catalyst characterization showed that high ratio of mesopore in the γ-Al2O3 support could benefit the catalyst activity and stability.