Dehydrogenation of ethylbenzene to styrene with CO2 over iron oxide-based catalysts

This paper describes dehydrogenation reaction of ethylbenzene to styrene with CO2 over iron oxide-based catalysts. Three catalysts of Fe2O3–MgO/γ-Al2O3, Fe2O3/MgAl2O4 and MgFe0.1Al1.9O4 with the same molar ratio of Mg/Fe/Al were prepared by impregnation and sol–gel methods. At 580 °C, the ethylbenzene conversion over MgFe0.1Al1.9O4 kept a value of 40% during the time on stream of 20 h, whereas that over Fe2O3/MgAl2O4 decreased rapidly from initial 50.0% to 27.4%. The properties of the catalysts were characterized by several techniques such as N2 adsorption/desorption, X-ray diffraction, thermogravimetry, energy dispersive X-ray spectroscopy, Fourier transform-infrared spectroscopy, 57Fe Mössbauer spectroscopy, temperature-programmed reduction, and temperature-programmed desorption of NH3 and CO2. It was found that the iron species of these catalysts are different. In MgFe0.1Al1.9O4, all Fe3+ species are incorporated in the spinel lattice. MgFe0.1Al1.9O4 shows high catalytic activity and stability in ethylbenzene dehydrogenation reaction with CO2. Moreover, the weak surface acidity of MgFe0.1Al1.9O4 prevents from the carbon formation during the reaction.