分子筛的结构表征及对痕量氙的动态吸附性能

高效吸附剂是大气放射性氙取样分析系统的核心组成部分之一，为提高探测灵敏度，需获得对大气中痕量氙具有更高吸附性能的吸附剂。研究了10种分子筛对痕量氙的动态吸附性能，利用氮气静态吸附对分子筛的孔结构进行表征，分析了孔结构特征与分子筛动态吸附性能的关系。选择吸附量较高的分子筛，进一步研究了原料气流量、吸附压力和氙浓度对动态吸附性能的影响。结果表明：5A分子筛具有较适合的孔径，对氙的动态吸附性能优于13X分子筛；ZSM-5分子筛可能因晶穴内极性较强和具有较适合的孔径，对氙的吸附能力最强；痕量氙在ZSM-5分子筛上的动态吸附系数随吸附压力的增加而线性增大，随流量增大先下降而后趋于稳定，氙浓度在7.6×10^-9~3.0×10^-8 mol/L范围内对其无明显影响。

Dynamic Adsorption Properties of Trace Xenon on Molecular Sieves and Their Structure Characterization

High performance adsorbents are one of the core components of an atmospheric radioxenon sampling and analysis system. In order to improve the detection sensitivity, it is necessary to obtain adsorbents with higher adsorption capacity for the trace xenon in the atmosphere. The dynamic adsorption properties of the trace xenon on 10 kinds of molecular sieves were investigated. The pore structure of molecular sieves was characterized by static nitrogen adsorption. The relationship between the pore structure and the dynamic adsorption properties of the molecular sieves was analyzed. The effect of flow rate of feed gas, pressure and xenon concentration on dynamic adsorption properties of molecular sieves with higher adsorption capacity was studied. The results show that the dynamic adsorption property of 5 A molecular sieve is better than that of 13 X molecular sieve because it has the suitable pore size. ZSM-5 molecular sieve has the highest adsorption capacity for xenon because of suitable pore size and a strong polarity in the crystal hole. The dynamic adsorption coefficient of the trace xenon on ZSM-5 molecular sieve increases linearly with the increase of adsorption pressure, and the value will tend to be stable after decrease as the flow rate increases. When the xenon concentration is between 7.6×10-9-3.0×10-8 mol/L, the dynamic adsorption coefficient nearly keeps constant.