【作者】 周志辉；

【导师】 王金渠；

【作者基本信息】 大连理工大学 ， 化学工艺， 2008， 博士

【摘要】 渗透蒸发是用于液体混合物分离的一种新型膜分离技术,与传统的分离技术相比,渗透蒸发具有分离效率高、能耗低、操作方便等优点。目前使用的渗透蒸发膜大多数为有机高分子膜,因其具有化学和热稳定性差、容易产生浓差极化、分离因数低等致命缺点,限制了其应用范围。沸石膜具有化学稳定性、热稳定性、机械稳定性、孔径均一和物料传输快等优点,近年来已经广泛应用在渗透蒸发操作过程中。NaA沸石膜由于具有高度亲水性,和介于水分子与大部分有机物分子之间的孔径,使其成为渗透蒸发有机溶剂脱水操作过程最理想的沸石膜,同时NaA沸石由于孔口直径小,成为分离小分子气体的理想材料。因此开展NaA沸石膜渗透蒸发脱水和NaA沸石复合膜气体分离方面的研究具有重要的意义。本文利用热浸渍引入晶种法,在载体外表面水热合成NaA沸石膜;利用浸渍提拉法在α-Al₂O₃载体上制备NaA沸石/炭复合膜,研究了复合膜的气体渗透规律;然后将制备的NaA沸石膜应用在乙醇脱水操作过程中,并利用分子探针法,研究了膜法乙醇脱水的渗透特性,再将制备的NaA沸石膜应用在氯代甲烷脱水、糠醛脱水和乙二醇二甲醚脱水体系中。实验主要结论如下:（1）、利用热浸渍引入晶种法,制备NaA沸石膜,发现NaA沸石膜在亲水性α-Al₂O₃载体的生长速度上比在疏水性炭载体和不锈钢载体上快2倍;利用浸渍提拉方法,制备沸石/炭复合膜,NaA沸石/炭复合膜在室温下的CO₂气体渗透通量为3.39×10^-7mol·m^-2·s^-1·pa^-1,比在同样条件下合成的炭膜高出两个数量级,且CO₂/N₂和CO₂/CH₄的分离因数分别为6.02和28.4,通过气体吸附实验,发现NaA分子筛加入到炭材料中,提高了炭材料对于CO₂/N₂的吸附选择性,并且根据Beta沸石/炭复合膜的气体渗透规律,发现了复合膜的渗透通量与沸石填充量成正比。（2）、将NaA沸石膜应用到乙醇脱水操作体系中,研究了进料流速、进料温度、进料乙醇含量和渗透侧压力等因素对膜法乙醇脱水性能的影响,通过优化实验条件,NaA沸石膜对于水/乙醇体系的渗透通量和分离因数分别为0.88 kg·m^-2·h^-1和15600;并利用分子探针法研究了NaA沸石膜渗透蒸发乙醇脱水渗透规律,发现对于乙醇脱水分离因数超过10000的NaA沸石膜存在晶间孔,并确定晶间孔的尺寸在0.82nm到1.02nm之间,进而进一步证实了NaA沸石膜乙醇脱水分离机理为吸附扩散分离机理。（3）、利用NaA分子筛膜渗透蒸发（蒸汽渗透）脱除氯代甲烷中微量水,系统地考查了进料温度、压差以及进料流量对膜法脱水性能的影响。结果表明:（a）利用吹扫气法,对于水/一氯甲烷操作体系,其分离因数高达74800,产品水含量由进料侧的2580 PPm,降低到50 PPm;（b）利用抽真空法,对于水/一氯甲烷操作体系,其分离因数高达32500,产品的水含量由进料侧的2580 PPm,降低到36 PPm;（c）对于二氯甲烷脱水体系,水/二氯甲烷分离因数和渗透通量分别为39900和0.172 kg·m^-2·h^-1;（d）对于氯仿脱水体系,操作温度为50℃时,水/氯仿分离因数和渗透通量分别为57300和0.564 kg·m^-2·h^-1;（e）对于四氯化碳脱水体系,操作温度为60℃,水/四氯化碳分离因数和渗透通量分别为68200和0.612 kg·m^-2·h^-1。（4）、利用NaA分子筛膜渗透蒸发法制备高纯糠醛和乙二醇二甲醚,系统地考查了进料流速、操作温度和进料糠醛含量对糠醛脱水性能的影响,通过优化操作条件,经过NaA分子筛膜处理后的产品糠醛含量从进料的89.6wt.%提高到99.52wt.%;对于应用渗透蒸发制备高纯乙二醇二甲醚操作过程,实验发现产品中乙二醇二甲醚含量从进料的81.5wt.%提高到99.8wt.%。更多还原

【Abstract】 Pervaporation（vapor permeation） is a new-type technique used for separation of liquid mixture,which is high-efficient,energy-saving,environmental and economical compared with other separation techniques.At present the majority of pervaporation membranes are organic polymer membranes,but those application fields are confined because of some fatal shortcomings such as poor chemical and thermal stability,concentration polarization,low separation factor etc.Zeolite membranes have been widely applied in pervaporation in recent years because of those excellent chemical stability,thermal stability,mechanical stability,uniform molecular-sized pores and fast transferring for materials.NaA zeolite membranes,with the molar ratio Si/Al nearly equal to 1,three-dimensional open-framework and high hydrophilicity, have been found many potential applications on dehydration of organic by pervaporation （vapor permeation）,and have become ideal materials for separation of small molecular gas mixture due to their uniform molecular-sized pores.So it is of paramount importance to study dehydration of organic by pervaporation using zeolite NaA membranes and gas separation using zeolite/carbon composite membranes.In this work,NaA zeolite membranes were hydrothermally synthesized on the outer surface of substrates by hot dip-coating method;the zeolite/carbon composite membranes were prepared on the alumina substrates and their permeability was also investigated;the NaA zeolite membranes were applied in the pervaperation dehydration of ethanol,where the molecular probe was used to study the permeability mechanism of dehydration of ethanol. The as-synthesized membranes were also applied in the dehydration of chlorinated methane, furfural and glycol dimethyl ether.The main results achieved were as follows:（1）.NaA zeolite membranes were hydrothermally prepared on the outer surface of substrates by hot dip-coating method.It was showed that the growth rate of NaA zeolite on the alumina supports was two times larger than that on the hydrophobic carbon supports and stainless steel supports.Zeolite/carbon composite membranes were prepared by dip-coating method.The permeance of carbon dioxide on the as-synthesized NaA zeolite/carbon composite was 3.39×10^-7 mol·m^-2·s^-1·Pa^-1,which was two orders of magnitude higher than that on the carbon membranes.The separation factor of CO₂/N₂ and CO₂/CH₄ was 6.02 and 28.4 respectively.Gas adsorption experiments indicated when NaA zeolite had been added into the carbon materials,the selective adsorption of CO₂/N₂ to carbon materials was improved. Moreover,it was showed that permeance of composite membranes was directly proportional to the content of zeolite according to gas permeability of zeolite/carbon composite membrane.（2）.The as-synthesized membranes were applied in the process of ethanol dehydration, and the effects of several factors,such as feed flow,feed temperature,ethanol content of feed and pressure of permeate side were investigated.The flux and separation factor on the dehydration of ethanol were 0.88 kg·m^-2·h^-1 and 15600.The permeability of dehydration of ethanol using NaA zeolite membranes was investigated by molecular-probe method.The results showed that there was grain boundary in the as-synthesized NaA zeolite membranes, whose separation factor exceeded 10000,and the size of the grain boundary was confirmed ranging from 0.82 nm to 1.02 nm,and thus the mechanism of dehydration separation of ethanol complied with adsorption-diffusion separation mechanism.（3）.The trace water in the chloromethanes was removed with pervaperation（vapor permeation） on NaA zeolite membranes,the effect of feed temperature,feed flow and pressure difference of feed on the performance of dehydration was systematically investigated. The results indicated that:（a） the water content of product decreased from 2580 PPm to 50 PPm by sweep gas method in the water/chloromethane system and the separation factor of water/chloromethane was 74800;（b） the water content of product decreased from 2580 PPm to 36 PPm by vacuum method in the water/chloromethane system and the separation factor of water/chloromethane was 32500;（c） the separation factor and the flux of the dehydration of dichloromethane were 39900 and 0.172 kg·m^-2·h^-1,respectively;（d） the separation factor and the flux of the dehydration of trichloromethane at 50℃were 57300 and 0.564 kg·m^-2·h^-1, respectively;（e） the separation factor and the flux of the dehydration of carbon tetrachloride at 60℃were 68200 and 0.612 kg·m^-2·h^-1,respectively.（4）.NaA zeolite membranes were successfully utilized in the preparation of the high-purity furfural and glycol dimethyl ether by pervaperation.The effect of feed flow, operation temperature and feed content on the dehydration of furfural was investigated.The furfural content of product increased from 89.6 wt.%to 99.52 wt.%under optimized conditions;the content of glycol dimethyl ether in the product increased from 81.5 wt.%to 99.8 wt.%under optimized conditions.更多还原