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以MEL型沸石分子筛分离回收有机物稀溶液为背景,从实验和模拟角度研究了乙醇/水体系在silicalite-2材料上的吸附行为。基于文献报道的晶体参数,采用密度泛函理论确定了silcalite-2构型以及含有硅羟基的silicalite-2构型,使用GCMC方法计算了乙醇和水在上述吸附剂上单组份吸附等温线,研究了硅羟基对吸附行为的影响,并应用理想溶液吸附理论(IAST)方法预测了silicalite-2吸附分离乙醇/水体系的分离因子。吸附等温线的实验和模拟结果显示,水吸附符合V型吸附等温线特征,乙醇吸附符合I型吸附等温线特征,硅羟基能够增强水在silicalite-2材料上的吸附能力。对于二元体系分离,随着进料浓度与操作压差的增加,分离因子减小。硅羟基的存在会降低乙醇/水的分离因子,模拟结果与silicalite-2材料渗透汽化分离乙醇/水体系的实验报道一致。
The adsorption behavior of ethanol / water system on silicalite-2 material was studied experimentally and simulatively on the background of MEL rare-earth zeolite separation and recovery of dilute organic solution. Based on the crystal parameters reported in the literature, the silcalite-2 configuration and the silicalite-2 configuration with silanol groups were confirmed by density functional theory. The single-component adsorption isotherms of ethanol and water on the adsorbents were calculated by GCMC. The effect of silanol groups on the adsorption behavior was studied. The separation factor of silicalite-2 adsorbed ethanol / water system was predicted by ideal solution adsorption theory (IAST). The experimental and simulation results of adsorption isotherms show that the adsorption of water conforms to the characteristics of V-type adsorption isotherms and the adsorption of ethanol conforms to the characteristics of type I adsorption isotherms. Silanol groups can enhance the adsorption capacity of water on silicalite-2 materials. For binary system separation, the separation factor decreases as the feed concentration and operating differential pressure increase. The existence of silanols will reduce the ethanol / water separation factor, and the simulation results are consistent with the experimental reports of pervaporation separation of ethanol / water system by silicalite-2.