MgFe_(0.1)Al_(1.9)O_4的合成及其催化乙苯与CO_2的氧化脱氢反应

Preparation and Catalytic Properties of MgFe_(0.1)Al_(1.9)O_4 in Oxidative Dehydrogenation of Ethylbenzene with CO_2

以柠檬酸为络合剂,采用溶胶-凝胶法制备了具有尖晶石结构的MgFe0.1Al1.9O4催化剂,并将其用于催化乙苯与CO2氧化脱氢反应.运用X射线衍射、X射线能量色散光谱分析、红外光谱、热重-差热、N2吸附-脱附和H2程序升温还原等技术对催化剂进行了表征.结果表明,在650oC以上焙烧即可制得结构确定、组成均一的Mg-Fe-Al-O复合氧化物催化剂,其中Fe物种主要以同晶取代的形式存在于尖晶石骨架中.随着焙烧温度的升高,尖晶石结晶度提高,Fe物种还原能力下降,催化剂晶粒度增大,比表面积降低.700oC焙烧制备的MgFe0.1Al1.9O4具有较好的催化乙苯与CO2氧化脱氢反应活性和稳定性.

The MgFe0.1Al1.9O4 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 ℃.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 ℃.With the increase in the preparation temperature,both the crystallinity and grain size of the catalyst increase and the reduction of Fe species decreases.MgFe0.1Al1.9O4 prepared by calcination at 700 ℃ shows high activity and good stability for the ethylbenzene dehydrogenation with CO2 during 20 h time on stream.