Dehydrogenation of ethylbenzene to styrene with CO 2 over iron oxide-based catalysts

Abstract

This paper describes dehydrogenation reaction of ethylbenzene to styrene with CO 2 over iron oxide-based catalysts. Three catalysts of Fe 2O 3–MgO/γ-Al 2O 3, Fe 2O 3/MgAl 2O 4 and MgFe 0.1Al 1.9O 4 with the same molar ratio of Mg/Fe/Al were prepared by impregnation and sol–gel methods. At 580 °C, the ethylbenzene conversion over MgFe 0.1Al 1.9O 4 kept a value of 40% during the time on stream of 20 h, whereas that over Fe 2O 3/MgAl 2O 4 decreased rapidly from initial 50.0% to 27.4%. The properties of the catalysts were characterized by several techniques such as N 2 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 NH 3 and CO 2. It was found that the iron species of these catalysts are different. In MgFe 0.1Al 1.9O 4, all Fe 3+ species are incorporated in the spinel lattice. MgFe 0.1Al 1.9O 4 shows high catalytic activity and stability in ethylbenzene dehydrogenation reaction with CO 2. Moreover, the weak surface acidity of MgFe 0.1Al 1.9O 4 prevents from the carbon formation during the reaction.