多级孔RuCe/ZSM-5催化氧化氯苯的抗中毒性能研究

Study on poisoning resistance property of chlorobenzene oxidation catalyzed by hierarchical RuCe/ZSM-5

以硅酸四乙酯为硅源,铝酸钠为铝源,海藻酸钠和四丙基氢氧化铵为模板剂,采用原位水热晶化法制备多级孔ZSM-5分子筛,负载Ru和Ce制备出RuCe/ZSM-5催化剂,考察了多级孔结构对RuCe/ZSM-5催化剂催化氧化氯苯性能的影响,并通过XRD、BET、XPS、H2-TPR、GCMS、TGMS等分析手段对催化剂进行了结构表征.结果表明,当分散液物质的量的比为1SiO2∶0.02Al2O3∶0.15TPAOH∶0.04SA∶40H2O,Ru和Ce的负载量分别为0.8%和10%,焙烧温度为350℃时,RuCe/ZSM-5催化剂催化氧化氯苯活性最佳,在氯苯浓度为2600 mg·m^(-3),反应空速为10000 h-1时,T90(氯苯转化率达到90%)为247℃,并且在反应温度为325℃时,氯苯转化率能持续48 h维持100%,而传统微孔RuCe/ZSM-5催化剂T90为302℃.多级孔RuCe/ZSM-5抗中毒性能的提升主要归因于多级孔结构能维持Ce4+的含量,减少氯苯和中间态产物的停留时间,抑制多氯副产物和积碳的形成,同时,反应气氛中的水汽虽与氯苯在催化剂表面上会产生竞争吸附,降低氯苯的转化率,但水汽能进一步提高催化剂的稳定性.

The hierarchical ZSM-5 was prepared by in-situ hydrothermal crystallization method which using tetraethyl silicate as silicon source,sodium aluminate as aluminum source,and sodium alginate and TPAOH as co-template.A series of RuCe/ZSM-5 catalysts were prepared by loading Ru and Ce.The effects of hierarchical structure on the catalytic oxidation of chlorobenzene by RuCe/ZSM-5 catalysts were investigated.The physical and chemical properties,by-products,and surface carbon deposition of catalysts were characterized by XRD,BET,XPS,H2-TPR,GCMS,and TGMS.The results exhibited that when the crystallization recipe was 1SiO2:0.02 Al2O3:0.15TPAOH:0.04 SA:40 H2O,the calcination temperature was 350℃,Ru and Ce capacity were 0.8%and 10%,respectively,the prepared hierarchical RuCe/ZSM-5 catalyst exhibited the optimal catalytic activity.When the concentration of chlorobenzene was 2600 mg·m^(-3)and the reaction space velocity was 10000 h-1,the hierarchical RuCe/ZSM-5 could reach 90%conversion of chlorobenzene at 247℃and maintained superb stability during 48 h reaction at 325℃while the T90 of traditional microporous RuCe/ZSM-5 catalyst was 302℃.The improvement of the catalytic performance and stability of hierarchical RuCe/ZSM-5 was mainly attributed to the hierarchical structure which could increase the content of Ce4+and further improve the redox capacity of the catalyst.Moreover,the hierarchical structure could reduce the residence time of chlorobenzene and intermediate products,thus inhibiting the formation of polychlorinated by-products and carbon deposition.At the same time,although the water vapor in the reaction atmosphere would compete with chlorobenzene to be adsorbed on the surface of the catalyst during the reaction and reduce the conversion rate of,the water vapor could further improve the stability of the catalyst.