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研究了钠、钾助剂对FeMn合成低碳烯烃催化剂结构及性能的影响.低温N2吸附、X射线光电子能谱(XPS)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、CO/CO2程序升温脱附(CO/CO2-TPD)、M?ssbauer谱和CO+H2反应的研究结果表明,增加Mn助剂含量促进了活性相的分散和低碳烯烃的生成,而过多锰助剂在催化剂表面的富集则降低了费托合成反应的CO转化率;钾助剂和钠助剂的加入均抑制了催化剂的还原并且促进了CO2和CO的吸附.比较还原后(H2/CO摩尔比为20)和反应后(H2/CO摩尔比为3.5)催化剂的体相结构可以发现,在FeMn、FeMnNa和FeMnK催化剂中,由于钾助剂的碱性和CO吸附能力较强,因此体相中FeCx的含量相对较高;而活性测试结果表明,FeMnNa催化剂拥有最好的CO转化率(96.2%)和低碳烯烃选择性(30.5%,摩尔分数).
The effects of sodium and potassium promoters on the structure and properties of FeMn catalysts for the synthesis of light olefins were investigated. The effects of N2 adsorption, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) The results of CO / CO2 temperature-programmed desorption (CO / CO2-TPD), Mössbauer spectroscopy and CO + H2 reaction show that increasing Mn promoter content promotes the dispersion of active phase and the formation of light olefins. The enrichment of Mn promoter on the catalyst surface reduced the CO conversion in the Fischer-Tropsch synthesis reaction. The addition of potassium promoter and sodium promoter inhibited the reduction of the catalyst and promoted the adsorption of CO 2 and CO. / CO molar ratio of 20) and the reaction (H2 / CO molar ratio of 3.5) catalyst phase structure can be found in the FeMn, FeMnNa and FeMnK catalyst, due to strong alkaline potassium adsorption and CO adsorption capacity, Therefore, the content of FeCx in the bulk phase is relatively high. The activity test results show that the FeMnNa catalyst has the best CO conversion (96.2%) and the selectivity to light olefins (30.5%, mole fraction).