Abstract: The MgFe_0.1Al_1.9O₄ catalyst with spinel structure was prepared by a sol-gel method using citric acid as the gelatinizer and was tested for dehydrogenation of ethylbenzene with CO₂ at 600 ºC. The formation temperature of the spinel phase and the dispersion state of Fe species were characterized by X-ray diffraction, X-ray energy dispersive analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, N₂ adsorption-desorption, and temperature-programmed reduction. The results indicate that the ternary-composite oxide catalyst of Mg-Fe-Al-O with a well-proportioned chemical composition, in which the Fe³⁺ species exist in spinel framework, can be obtained at the temperature higher than 650 ºC. With the increase in the preparation temperature, both the crystallinity and grain size of the catalyst increase and the reduction of Fe species decreases. MgFe_0.1Al_1.9O₄ prepared by calcination at 700 ºC shows high activity and good stability for the ethylbenzene dehydrogenation with CO₂ during 20 h time on stream.

Key words: iron composite oxide, ethylbenzene, carbon dioxide, oxidative dehydrogenation, styrene