碱土及锰系复合氧化物担载Fe-K催化剂的费-托合成性能

Catalytic Performance of Fe-K Catalysts Supported on Alkaline Earth orManganese-Containing Composite Oxides in Fischer-Tropsch Synthesis

制备了铝氧化物(Al-O)基体分别与Mn或碱土元素构成的复合氧化物型高温钝化系列载体,担载Fe-K后制成Fe-K_(2)O/MAl_(2)O_(4)(M为Mg、Ca、Sr、Ba、Mn)催化剂,用于费-托合成反应。采用X射线粉末衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)、N_(2)物理吸附、CO_(2)化学吸附-程序升温脱附(CO_(2)-TPD)、场发射电子显微镜等分析方法表征了Fe-K_(2)O/MAl_(2)O_(4)催化剂的物理化学性质。采用固定床加压反应器进行了催化剂的合成气费-托转化催化性能评价。结果表明:不同元素种类(Mg、Ca、Sr、Ba、Mn)造成Fe-K_(2)O/MAl_(2)O_(4)催化剂的CO_(2)-TPD高温脱附峰面积占总脱附峰面积百分比、高温脱附峰温度等出现显著差异。对Fe-K_(2)O/MAl_(2)O_(4)催化剂来说,表面碱性位的碱性越强,则催化剂的活性越高。发现所制备的5种Fe-K_(2)O/MAl_(2)O_(4)催化剂的C_(2)-C_(4)烯/烷比、C-C偶合能力、低碳烯烃烃类选择性均与其CO_(2)-TPD高温脱附峰温度大致呈反向关系,即当CO_(2)-TPD高温脱附峰温度越高时,三者的数值将趋于越低。CO_(2)-TPD高温脱附峰温度位于669~692℃的Fe-K_(2)O/MgAl_(2)O_(4)、Fe-K_(2)O/MnAl_(2)O_(4)催化剂比位于744~749℃的Fe-K_(2)O/CaAl_(2)O_(4)、Fe-K_(2)O/SrAl_(2)O_(4)、Fe-K_(2)O/BaAl_(2)O_(4)催化剂更有利于促使反应生成低碳烯烃。

A series of composite oxide type supports composed of aluminum oxide(Al-O)matrix,manganese or alkaline earth elements were synthesized and then passivated at high temperature.When Fe-K supported,the Fe-K_(2)O/MAl_(2)O_(4)(M=Mg,Ca,Sr,Ba,Mn)catalysts were prepared and employed by Fischer-Tropsch(F-T)reactions.The Fe-K_(2)O/MAl_(2)O_(4)catalysts were characterized by X-rays diffraction(XRD),inductively coupled plasma optical emission spectrometry(ICP-OES),N_(2)physisorption,CO_(2)chemical adsorption-temperature programmed desorption(CO_(2)-TPD),and field emission electron microscopy.The F-T conversion of syngas was evaluated in a fixed bed pressurized reactor to determine the performance of catalysts.Different element(M)types cause significant differences in each percentage of high temperature desorption peak area to total desorption peak area,as well as the temperature of CO_(2)-TPD high temperature desorption peaks.Strong surface basicity favors high catalytic activity.It was determined that the C_(2)-C_(4)olefin to paraffin ratio,C-C coupling ability,and the hydrocarbon selectivity of light olefins of the five Fe-K_(2)O/MAl_(2)O_(4)catalysts were generally contrary to the temperature of CO_(2)-TPD high-temperature desorption peaks,that is to say,the higher the high-temperature desorption peak temperature of CO_(2)-TPD,the lower the values of the three parameters.The catalysts(M=Mg,Mn)with CO_(2)-TPD high temperature desorption peak temperature of 669-692℃are favorable to the production of light olefins than the catalysts(M=Ca,Sr,Ba)with desorption peak temperature of 744-749℃.