Co_9CrO_z/HZSM-5催化剂催化氧化低浓度氯乙烯

Catalytic oxidation of low-concentration vinyl chloride over Co_9CrO_z/HZSM-5 catalysts

采用浸渍法制备了一系列不同负载量的Co_9CrO_z/HZSM-5催化剂,利用XRD,H_2-TPR,NH_3-TPD,TEM,EDX等表征方法对制备的催化剂进行表征,考察了所制备催化剂对低浓度氯乙烯的催化氧化性能。表征结果显示,催化剂表面酸性随着Co_9CrO_z负载量增加而减弱,而Co_9CrO_z/HZSM-5催化剂的氧化性随之先增强后减弱;对低浓度氯乙烯催化氧化活性与Co_9CrO_z和HZSM-5之间存在协同作用有关,HZSM-5表面存在丰富的酸中心,有利于HCl生成,而Co_9CrO_z的氧化中心有利于中间产物深度氧化为CO_2,合适的酸量和较强的氧化性有利于提高催化剂的活性。实验结果表明,30CoCr/HZSM-5催化剂显示出最高的催化活性,随着Co_9CrO_z负载量的增加CO_2选择性随之升高,而HCl选择性随之先增大后减小。

A series of Co9CrOz/HZSM-5 catalysts with different loadings were prepared by wet impregnation method. The prepared catalysts were characterized by XRD,H2-TPR,NH3-TPD, TEM and EDX,and then its performance of catalytic oxidation for low-concentration vinyl chloride were investigated. The characterization results exhibited that with the increase of Co9CrOz loading, the surface acidity became weaker,and the oxidizability of Co9CrOz/HZSM-5 catalysts displayed enhanced firstly and then weakened. The catalytic oxidation activity for low-concentration vinyl chloride was associated with the synergetic effect of Co9CrOz and HZSM-5 catalysts. Moreover,the presence of abundant acid sites on the surface of HZSM-5 could enhance the formation of HCl and the oxidation center of Co9CrOz could promote the further oxidation of intermediates to CO2. In addition,the catalyst activity can be improved by the proper amount of acid and stronger oxidation. The experiment results indicated that the 30CoCr/HZSM-5 catalyst showed the highest activity. As the Co9CrOz loading gradually increased,the CO2 selectivity increased,while the HCl selectivity increased first and then decreased.