高交换度BaX分子筛的制备及其吸附分离对二甲苯性能的研究

13X型分子筛经过钾离子交换后,再进行钡离子交换,多次交换后得到不同钡交换度的BaX分子筛。采用X射线衍射分析(XRD)、X射线荧光光谱分析(XRF)、比表面积物理吸附分析(BET)以及热失重/差热分析(TG/DTA)对样品进行表征,考察了不同钡交换度对分子筛吸附分离对二甲苯性能的影响。结果表明:钡离子交换后,分子筛孔道中的有效空间有所减少,平均孔径有所下降,但分子筛的晶型结构未受到明显影响;随着钡离子交换度的逐渐增大,BaX分子筛吸附分离对二甲苯的能力不断增强;钡离子交换度达到98.5%时,邻、间、对二甲苯的饱和吸附量分别为:254.1 mg/g、218.4 mg/g、376.9 mg/g,对/邻二甲苯分离系数、对/间二甲苯分离系数分别达到最大,为β(PX/OX)=1.48、β(PX/MX)=1.72。

Preparation of BaX Zeolite with High Exchange Degree and the Study on Its Adsorptive Separation Ability for p-Xylene

The BaX zeolite samples with different Ba^2＋exchange degree were prepared first by K＋and then by Ba^2＋ion exchange for multiple times. The samples were characterized by XRD, XRF, BET and TG/DTA to investigate the influence of Ba^2＋ion-exchange degree of BaX zeolite on its adsorptive separation ability for p-xylene. The results showed that the average pore diameter and effective pore volume of 13 X molecular sieves decreased after Ba^2＋ion-exchange, while the crystal structure of 13 X zeolite was hardly influenced. With the increase of the degree of Ba^2＋ion-exchange, the adsorptive separation ability for p-xylene improved gradually. When the Ba^2＋ion-exchange degree reached 98.5%, the saturated adsorption capacity of the zeolite for o-xylene, m-xylene, p-xylene were 254.1 mg/g, 218.4 mg/g, 376.9 mg/g, and the separation coefficients of p-xylene to o-xylene and p-xylene to m-xylene reached the maximum values being β（PX/OX）=1.48 andβ（PX/MX）=1.72, respectively.