Cr2O3气相催化1,1,2-三氯乙烷脱HCl性能

采用沉淀法制备了不同焙烧温度的Cr₂O₃催化剂,用于1,1,2-三氯乙烷(TCE)气相脱氯化氢制备二氯乙烯的反应。 采用X射线衍射(XRD)、氢气程序升温还原(H₂-TPR)、氨气程序升温脱附(NH₃-TPD)、X射线光电子能谱(XPS)表征手段,研究了Cr₂O₃催化剂气相催化裂解TCE脱氯化氢反应及其反应机理。 结果表明,Cr₂O₃催化剂上TCE气相脱氯化氢反应的转化率随着催化剂焙烧温度的升高逐渐降低,然而顺-1,2-二氯乙烯(cis-DCE)的选择性先增大后减小。 400 ℃焙烧的Cr₂O₃催化剂催化性能最好,TCE转化率为70.8%,顺-1,2-二氯乙烯的选择性为90.0%。 然而,催化剂的单位面积反应速率随着焙烧温度升高先提高后下降,400 ℃焙烧催化剂的单位面积反应速率为0.801×10^-2 μmol/(s·m²)。 催化剂的单位面积反应速率和顺-1,2-二氯乙烯(cis-DCE)的选择性与催化剂表面Cr₂O₃物种具有很好的对应关系,表明催化剂表面Cr₂O₃物种有利于脱氯化氢反应。 以酸中心为活性中心计算得到的转换频率(TOF)变化趋势与单位面积反应速率相一致,400 ℃焙烧的催化剂的TOF为2.82×10^-5 s^-1,表明Cr₂O₃催化剂Cr物种合适的平均价态(~3.20)有利于脱氯化氢反应。

Gas Phase Dehydrochlorination of 1,1,2-Trichloroethane over Cr2O3 Catalysts

A series of Cr₂O₃ catalysts was prepared by a precipitation method and tested for the gas phase dehydrochlorination of 1,1,2-trichloroethane(TCE) to synthesize cis-1,2-dichloroethylene(cis-DCE). X-ray diffraction(XRD), hydrogen temperature-programmed reduction(H₂-TPR), ammonia temperature-programmed desorption(NH₃-TPD) and X-ray photoelectron spectroscopy(XPS) were used to study the dehydrochlorination of TCE on Cr₂O₃ catalyst and its reaction mechanism. It is found that the conversion ratio of TCE on the catalysts decreases with the increase of the calcination temperature, while the selectivity to cis-DCE first increases and then decreases. The best performance is obtained on the catalyst calcined at 400 ℃, with a TCE conversion ratio of 70.8% and a cis-DCE selectivity of 90.0%. In addition, the areal specific reaction rate also first increases and then decreases with the increase of the calcination temperature, with the highest value being obtained on the catalysts calcined at 400 ℃(0.801×10^-2 μmol/(s·m²). The catalytic behaviors of the catalysts are well related to their surface Cr₂O₃ species. Turnover frequencies(TOFs) calculated based on the surface acidity and the highest value being obtained on the catalysts calcined at 400 ℃(2.82×10^-5 s^-1) show that the oxidation states of the surface Cr species are important for the reaction and the Cr species with an average valence of 3.2 are appropriate for the reaction.