沸石对气体混合物吸附分离性能的分子模拟研究

Molecular simulation study on the property of absorption separation of zeolites for gas mixtures

采用分子模拟的方法研究了21种具有不同拓扑结构的沸石对二氧化碳/甲烷、二氧化碳/氮气两个混合体系的分离能力。通过研究这些沸石结构和性质得到沸石吸附选择性与材料结构参数之间的关联关系。结果表明:对于所研究的两个混合体系,沸石均优先吸附二氧化碳,即二氧化碳的吸附量远大于甲烷和氮气的吸附量。为了定量描述沸石结构-性质之间的关系,尝试将沸石的吸附选择性与材料常用的结构参数(如两个气体组分无限稀释状态下的吸附热差、孔体积、孔率和比表面积)进行关联,发现沸石材料的选择性与常用的单一的材料结构参数没有好的关联,但沸石的吸附选择性与吸附度关联较好。该结果可应用到沸石的分离以及沸石材料预筛选的评价中。

Molecular simulations were performed to study the seperation ability of twenty-one zeolites with different topological structures for the two mixture systems of carbon dioxide/methane and carbon dioxide/nitrogen.The relationship between the adsorption selectivity and the structural parameters of zeolites can be obtained through the investigations on the structures and properties of these zeolites.The results show that zeolites have adsorption preference for carbon dioxide over methane and nitrogen for the two mixing systems,that is the adsorption capacity of carbon dioxide is greater than those of methane and nitrogen.To quan-titatively describe the structure-selectivity relationship for zeolites,the correlations between the adsorption selectivity and the commonly structural parameters of material such as the difference of isosteric heats of adsorption between the two components, pore volume,porosity,and specific accessible surface area have been studied.The results show that there are not good correlations for the selectivity and the single structural parameter.However,the＆quot;adsorbility＆quot;correlates well with the selectivity of zeolites.The results can be applied to the evaluation of the separation performance of zeolites and the preliminary selection of zeolite materials.