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锂离子交换ZSM–5型分子筛中水分子吸附特性的分子模拟
作者:胡玉坤 丁静 彭晓峰 杨建平 王维龙  
单位:华南理工大学传热强化与过程节能教育部重点实验室 中山大学工学院 清华大学相变与界面传递过程实验室 华南理工大学传热强化与过程节能教育部重点实验室 华南理工大学传热强化与过程节能教育部重点实验室 广州510640 广州510275 北京100084 广州510640 广州510640 
关键词:  分子筛  吸附  锂离子交换  分子模拟 
分类号:O643.36
出版年,卷(期):页码:2007,35(9):1247-1252
DOI:
摘要:

用巨正则系综 Monte Carlo(grand canonical assemblage Monte Carlo, GCMC)模拟方法计算了水在 HZSM–5 型分子筛中的吸附热,计算结果与文献报道的实验结果吻合得较好。模拟了水在经锂离子(Li+)交换后的 ZSM–5 型分子筛上的吸附等温线。在此基础上,进一步预测了水在不同硅铝摩尔(下同)比的 LinZSM–5 型分子筛中的吸附性质。计算结果显示:分子筛骨架上的硅铝比显著影响水的吸附量和等温吸附曲线,随着硅铝比的减小,分子筛中的自由体积减小,对水的吸附量增加。水分子的主要吸附位置是在 Li+ 和铝原子的周围,LinZSM–5 型分子筛中存在着 1 个主要的吸附位点。Li+等金属阳离子的交换能有效降低水的吸附热。在吸附量相同的条件下,水的吸附热随着硅铝比的升高而降低。

The grand canonical assemblage Monte Carlo (GCMC) method was used to calculate the adsorption heat of HZSM–5 zeo- lite. The results are in good agreement with the experimental data reported in the literature. Then the adsorption isotherms of water by Li+ exchanged ZSM–5 zeolite were simulated. Based on these facts, adsorption of water on LinZSM–5 zeolite with various molar ratios n(Si)/n(Al) is predicted. The simulation results indicate that the n(Si)/n(Al) ratio of the zeolite framework greatly affects the water adsorption and adsorption isotherms. The adsorption amount decreases as the n(Si)/n(Al) ratio increases, and the free volume is even greater. The adsorbed water molecules are located around Li cations and Al atoms on the zeolite framework and a main sorption site for water in LinZSM–5 zeolite. The ZSM–5 zeolite modified by Li cations can decrease the isosteric heat effectively. At the same loading, the adsorption heat decreases as the n(Si)/n(Al) ratio increases.

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基金项目:
国家自然科学基金(90610023)资助项目。
作者简介:
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参考文献:

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