摘要
基于巨正则蒙特卡洛和分子动力学,对NH_3-SCR反应体系中吸附质分子(NO与NH_3)在不同拓扑结构沸石分子筛(LTL、FER、LEV、BEA、MOR、FAU、CHA和MFI)上的吸附和扩散特性进行系统研究。结果表明,对于全硅分子筛而言,其分子筛的拓扑结构影响NO与NH_3在分子筛上的吸附,综合吸附量及吸附作用能发现,MFI和LEV分子筛对NO具有较优的吸附特性;MFI和BEA分子筛对NH_3具有较优的吸附特性。研究了Si与Al物质的量比对BEA分子筛吸附性能影响,结果表明,随着Si与Al物质的量比降低,分子筛自由体积逐渐增加,进而有助于分子筛催化剂对NO和NH_3的吸附。采用分子动力学模拟计算NO与NH_3在不同构型全硅分子筛上的扩散系数,发现具有三维直通道且孔径较大的分子筛催化剂有利于NO和NH_3在其孔道内部的扩散,MFI虽然具备三维孔道结构,但由于存在Z型交叉通道,一定程度阻碍了反应物分子的扩散。
The adsorption and diffusion of NO and NH3 as the reactant of NH3-SCR reaction system over various kinds of zeolite Catalysts （ LTL, FER, LEV, BEA, MOR, FAU, CHA, MFI） were investigated by employing molecule simulation methods of Monte Carlo and Molecular Dynamics. The results indicated that the zeolitic topology greatly influenced the adsorption of NO and NH3 molecules according to the sim- ulation results of adsorption amount and adsorption energy. Accordingly, it was found that MFI and LEV were efficient for NO adsorption, and MFI and BEA were efficient for NH3 adsorption. The effects of Si/A1 molar ratio on the adsorption of NO and NH3 over BEA zeolite were also studied. The study showed that the free volume of zeolite catalysts gradually increased along with the decrease of Si/Al molar ratios, which facilitated the adsorption of NO and NH3. The molecular dynamics was further employed for the cal-culations of diffusion coefficient of NO It was found that 3 dimensional straigh and NH3 on all-silicon zeolites with different topological structure. t channel and large pore size contributed to better diffusions of NO and NH3 molecules. Although MFI zeolite also possessed three dimensional pore structures, it hindered the diffusion of reactant molecules to some extent due to the presence of Z type cross channel.
出处
《工业催化》
CAS
2016年第10期33-40,共8页
Industrial Catalysis
基金
国家自然科学基金(214777007
21407007)资助项目
江苏省自然科学基金(BK20140268)
北京化工大学“优势学科新增长点”学科提升计划项目(YS1401)
北京化工大学学科建设项目(XK1504)
国家高科技研究发展计划(863计划)(2013AA065901)资助项目
关键词
催化化学
NO与NH3
分子筛
巨正则蒙特卡洛
分子动力学
吸附
扩散
catalytic chemistry
NO and NH3
zeolite
Grand Canonical Monte Carlo （ GCMC ）
moleculardynamics（MD）
adsorption
diffusion
作者简介
李懿，1990年生，女，陕西省宝鸡市人，硕士研究生，研究方向为含氮废气催化脱除。
通讯联系人：张润铎，教授，博士研究生导师，教育部新世纪优秀人才，化工学院副院长，主要研究领域为：（1）新颖环境友好材料的制备及特色微区结构的控制与调变；（2）新型废气净化催化剂结构与高净化效能间的匹配创研；（3）尾气催化剂活性结构的研究及反应机理的深入探索。
