铁系催化剂上乙苯与CO_2氧化脱氢反应

Oxidative Dehydrogenation of Ethylbenzene with CO_2 over Iron Oxide-Based Catalysts

采用浸渍法和溶胶-凝胶法制备了三种含Mg,Fe和Al量相同的Fe2O3-MgO/γ-Al2O3,Fe2O3/MgAl2O4和MgFe0.1Al1.9O4催化剂,在580°C考察了它们催化乙苯与CO2氧化脱氢反应性能,并采用X射线衍射,表面元素分析,H2-程序升温还原和CO2-程序升温脱附等技术对催化剂体相及表面性质进行了表征.结果表明,催化剂制备方法影响Fe物种的存在形态,进而影响催化剂的稳定性和活性.采用浸渍法制备的Fe2O3/MgAl2O4催化剂含有高度分散的Fe2O3活性物种,该物种具有较好的初活性,但是稳定性较差;而采用溶胶-凝胶法制备的MgFe0.1Al1.9O4催化剂中,Fe物种主要以同晶取代的形式存在于尖晶石骨架中,因而具有较高的乙苯与CO2氧化脱氢催化活性和稳定性.

Three catalysts, Fe2O3-MgO/γ-Al2O3, Fe2O3/MgAl2O4, and MgFe0.1Al1.9O4, with the same content of Mg, Fe, and Al were prepared by the impregnation method and sol-gel method, respectively, and the catalytic performance was tested for the dehydrogenation of ethylbenzene with CO2 at 580 °C. The structural and surface properties of the catalysts were characterized by X-ray diffraction, energy dispersive X-ray analysis, temperature-programmed reduction, and CO2 temperature-programmed desorption. The results showed that the preparation methods of the catalysts affected the dispersion state of Fe and therefore influenced the activity and stability of the catalysts. Highly dispersed Fe203 formed on Fe2O3/MgAl2O4 prepared by impregnation exhibited highest initial activity, but it deactivated rapidly during the time on stream of 20 h. The active species of Fe^3＋ existing in spinel framework of MgFe0.1Al1.9O4 prepared by the sol-gel method showed both high activity and good stability for ethylbenzene dehydrogenation with CO2.