Abstract:

In order to improve the pervaporation performance of SA, nano-alumina, nano-zirconia and nano-titania were incorporated into SA solution, respectively. The difference of pervaporatin performance was analyzed, and the membrane that had better separation performance was selected for pervaporation (PV)-assisted esterification of acetic acid and ethanol. The effect of nano-particles content on the separation performance was investigated. The obtained membranes were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal stability, tensile strength and permeate flux of hybrid membranes were enhanced after incorporating nano-particles into SA. When the mass ratio of nanoparticles to SA was 0.3, the methylene iodide contact angle of incorporated TiO₂, ZrO₂ and Al₂O₃ hybrid membranes increased, respectively. Meanwhile, the permeate flux increased at the same time. The hydrophilic property of SA-0.3Al₂O₃ membrane was the best; however, the separation performance of SA-0.3ZrO₂ membrane was better. The permeate flux of SA-0.3ZrO₂ membrane was 336 g·m^-2·h^-1 with water content 99.97% in the permeate side and separation factor 29990 when the amount of water in feed was 10% at 50℃. The conversion of esterification enhanced by pervaporation reached 93.9% in 12 h at 80℃.

Key words: sodium alginate, hybrid membrane, nano-alumina, nano-zirconia, nano-titania, pervaporation, esterification

摘要：

为提高海藻酸钠（SA）膜的渗透汽化分离性能，分别采用纳米氧化铝、纳米氧化锆和纳米氧化钛对SA膜进行改性，对比分析了3种不同杂化膜渗透汽化分离性能的差异，并将分离性能较好的杂化膜应用到乙酸与乙醇酯化反应脱水的体系中。系统考察了无机纳米粒子含量对SA膜渗透汽化分离性能的影响，对杂化膜进行了接触角、傅里叶红外（FTIR）、扫描电子显微镜（SEM）、热重/差示扫描量热（TG/DSC）、X射线衍射（XRD）和拉伸强度等表征与分析。结果表明，无机纳米粒子能提高SA膜的热稳定性、机械强度和渗透通量，当无机纳米粒子与SA质量比为0.3时，掺杂TiO₂、ZrO₂和Al₂O₃的杂化膜二碘甲烷的接触角依次升高，同时渗透通量也依次升高。SA-0.3Al₂O₃杂化膜亲水性较好，然而SA-0.3ZrO₂杂化膜分离性能最优，50℃下分离水含量10%的乙醇-水溶液，膜渗透通量达到336 g·m^-2·h^-1，渗透侧水含量99.97%，分离因子29990。酯化反应脱水实验表明，在80℃时，酯化反应脱水实验乙酸转化率均高于无脱水实验乙酸转化率，平衡转化率不断被打破，反应12 h后，转化率由平衡时的79.3%提高到93.9%。

关键词: 海藻酸钠, 杂化膜, 纳米氧化铝, 纳米氧化锆, 纳米氧化钛, 渗透汽化, 酯化