斜发沸石的水热合成和离子交换性能及其在CH4/N2分离中的应用

摘要

以氢氧化铝为铝源,硅溶胶为硅源,通过水热法合成斜发沸石,采用XRD、TEM、BET、FT-IR、TG、29Si NMR等手段考察了OH-/Si的摩尔比、晶化时间和晶化温度等合成参数对其结构和CH4/N2分离性能的影响.基于晶化动力学曲线,由阿伦尼乌斯方程导出诱导期和生长阶段的表观活化能值,分别为91.5和7.2 k J/mol.通过水溶液离子交换工艺分别获得Ca型或K型斜发沸石,并初步探讨了离子交换前后斜发沸石对CH4/N2的分离性能.结果表明,斜发沸石对CH4/N2的平衡选择性依赖于交换阳离子电荷类型,数量及其在骨架中的分布,其中K型斜发沸石分离效果较好,有望用于煤层气回收.%Clinoptilolite was synthesized via hydrothermal method using aluminum hydroxide as aluminum source and silica sol (Ludox) as silicon source.The influences of synthesized parameters (i.e.,molar ratio of n(OH-)(Si),crystallization time and crystallization temperature,etc.) on the structure of prepared clinoptilolite and its CH4/N2 separation performance were investigated by various characterization techniques,including XRD,TEM,BET,FT-IR,TG,29Si-NMR.Particularly,the kinetic behaviors of crystallization rate were evaluated,and the apparent activation energies for induction and growth period according to Arrhenius equation are 91.5 and 7.2 kJ/mol,respectively.Meanwhile,Ca2+ and K+ clinoptilolites were prepared through water solution ion exchange method.Moreover,the CH4/N2 separation performance was also evaluated for clinoptilolites with/without ion exchange.Experimental results suggest that equilibrium selectivity of CH4/N2 is strongly depended on the type of exchanged cationic charge,its quantity and distribution in the skeleton.K-clinoptilolite exhibited a good separation performance,and could be a promising absorbent for coal bed methane recovery.