NaY沸石分子吸附涂层对典型空间污染物的吸附机制研究

Adsorption Mechanism of NaY Zeolite Molecular Adsorber Coating on Typical Space Contaminations

在轨高真空环境下,航天器所用非金属材料会释放出碳氢类、硅氧烷等有机分子污染物,沉积在航天器光学系统等敏感表面,影响航天器性能和使用寿命。沸石分子吸附涂层可以实时吸附空间污染物,但对其吸附作用机制还缺乏深入研究。为深入分析空间污染物分子在沸石内部的吸附机制,本工作采用巨正则蒙特卡洛方法模拟计算了NaY沸石对三种典型空间污染物(甲苯(C_(7)H_(8))、邻苯二甲酸二甲酯(C_(10)H_(10)O_(4))和八甲基环四硅氧烷(C_(8)H_(24)O_(4)Si_(4)))的吸附行为(吸附等温线、吸附热曲线和粒子密度分布图)。模拟和实验数据的对比分析验证了计算模型和方法的合理性。在超高真空条件下,NaY沸石对空间污染物表现出较高的吸附量,但其饱和吸附量随着分子尺寸的增加而降低(C_(7)H_(8)>C_(10)H_(10)O_(4)>C_(8)H_(24)O_(4)Si_(4)),其中八甲基环四硅氧烷分子的饱和吸附量仅为8个分子,远低于甲苯的36个分子。污染物分子在沸石内部的密度分布图显示,三种污染物均优先吸附于NaY沸石的“超笼”位点。本研究系统分析了NaY沸石对典型污染物的吸附机制,为高吸附性能的沸石分子筛吸附涂层的研发提供了理论指导。

In a high vacuum environment,some organic molecular pollutants such as hydrocarbon and siloxane are released by spacecraft materials and deposited on the surface of the sensitive parts of spacecraft devices,which has become an important adverse factor restricting the development of long-life and high-performance spacecraft.Zeolite molecular adsorber coating can effectively collect spatial contaminations in real time,but the adsorption mechanism is not clear.To deeply analyze the adsorption mechanism of zeolite on the spatial contaminations,the adsorption behaviors of NaY zeolite including adsorption isotherms,adsorption heat curves and density distributions on three typical contaminations,toluene(C_(7)H_(8)),dimethyl phthalate(C_(10)H_(10)O_(4)),octamethyl cyclotetrasiloxane(C_(8)H_(24)O_(4)Si_(4)),were calculated by the Grand Canonical Monte Carlo method in this work.The NaY zeolites and pollutant models were successfully constructed,and the rationality of the models was verified by comparing simulated data with experimental ones.These results indicated that all three classic molecules can be adsorbed by NaY zeolite in the ultra-high vacuum condition.The saturated adsorption capacity decreases in the order of C_(7)H_(8)>C_(10)H_(10)O_(4)>C_(8)H_(24)O_(4)Si_(4),which is significantly related to the molecule sizes and structures of contaminations.The saturated adsorption amount of C8H24O4Si4 is relatively low(8 per cell)when that of C7H8 is 36 per cell.In addition,the density distributions indicates that different contaminations are preferentially adsorbed inside the super-cage of NaY zeolite.Overall,this work analyzes the adsorption mechanism of NaY zeolite on typical contaminations,and can provide basic insights for the development of zeolite molecular adsorber coating with high adsorption capacity.