含氟体系下亲水性ZSM-5沸石分子筛膜的制备及其性能

用变温热浸渍法在廉价大孔α-Al₂O₃的载体管上涂覆大小晶种引入平整均匀的晶种层, 随后在无有机模板剂的含氟体系下通过二次水热生长法制备了亲水性ZSM-5沸石分子筛膜。实验考察了小晶种液浓度对形成晶种层及ZSM-5沸石分子筛膜形貌和性能的影响。并将制备的ZSM-5沸石分子筛膜分别用于渗透汽化异丙醇脱水和乙酸脱水体系中。结果显示, 小晶种液浓度为0.2wt%时, 制备的ZSM-5沸石分子筛膜在75℃下对10wt%水/异丙醇和10wt% 水/乙酸混合物体系均具有优良的分离性能, 其渗透通量分别为3.64 kg/(m²·h)和0.61 kg/(m²·h), 分离因子分别达3204和1321。     

自具微孔聚合物在渗透汽化膜分离中的应用进展

介绍了自具微孔聚合物(PIMs)及其改性膜材料在渗透汽化膜分离领域中的应用研究进展,评述了在优先脱有机物、优先脱水以及有机混合物分离3个领域中所应用的PIMs膜的分子结构设计、改性方法以及分离效果.PIMs是一种依靠自身分子扭曲而具有大量微孔的新型聚合物,具有憎水性以及均一的孔结构,对于不同体系中的目标分离物均有较好的...     

EC-HBPE渗透汽化膜的性能

以三羟甲基丙烷为核、二羟甲基丙酸为单体,采用准一步法合成了1~5代脂肪族超支化聚酯(HBPE)。将该聚酯与乙基纤维素(EC)共混制备了EC-HBPE均质膜,以苯/环己烷体系为对象,对该共混膜的溶胀行为和渗透汽化性能进行了考察。结果表明,适量3、4、5代HBPE的加入可以在不降低膜分离因子的同时,大幅度提高膜的通量。在苯含量较低(<10%)的料液中,EC-HBPE的吸附选择性略高于EC,而EC-HBPE液的平衡吸附量明显高于EC。     

热浸渍晶种法制备高重复性NaA分子筛膜

利用热浸渍法和打磨法引入晶种合成NaA分子筛膜,将合成的NaA分子筛膜应用于乙醇/水混合体系,研究进料温度、进料侧压力及进料流量等对其分离性能的影响。结果表明,进料温度升高,渗透通量和分离因数呈增大趋势;进料侧压力增大,渗透通量增加,分离因数减小;进料流量增大,渗透通量明显增大,分离因数未发生明显变化。进料温度为75℃、进料侧压力为100kPa、相对真空度接近-0.1MPa、进料流量为16L/h时,所得NaA分子筛膜的渗透通量和分离因数分别为1.08kg.m-2.h-1和3 338,此时用于乙醇/水混合体系分离效果最佳。NaA分子筛膜的重复性高达80%。     

硅橡胶膜生物反应器乙醇连续发酵传质动力学实验研究

利用新型的硅橡胶平板复合膜构造乙醇连续发酵膜生物反应器,研究了连续发酵-渗透蒸发操作稳态过程的膜传质动力学问题,实验分析了发酵液循环流量、发酵温度、膜表面液体流动模式对膜性能的影响。在长达500h的连续发酵过程中,膜的分离性能维持相对稳定,没有出现膜污染现象。硅橡胶膜对发酵液中的乙醇的原位分离有效地减轻了代谢产物对细胞抑制作用,在发酵过程的前后阶段,膜的总传质系数从5.21×10-7m/s提高到7.94×10-7m/s。膜对实际发酵液的分离性能表现比对乙醇-水模型溶液的高。     

膜生物反应器苹果原汁发酵研究（Ⅱ） —产物特性和膜器放大

在前期工作的基础上,采用扩大膜面积的新型硅橡胶膜生物反应器进行了苹果原汁发酵的进一步深入研究。整个系统运行稳定,硅橡胶复合膜分离性能良好。膜下游通过两级冷凝,得到了酒度适宜的苹果白兰地,酒味浓烈,果香优雅;膜上渗余液营养丰富,含有大量的有机酸,可用于生产苹果酸性饮料。     

新型PVA/PA复合膜的运行工艺对渗透汽化性能的影响

研究了聚乙烯醇（PVA）/聚酰胺（PA）复合膜渗透汽化（PV）分离异丙醇（IPA）/水混合物时运行工艺的影响,模拟了渗透通量（J）预测方程。结果表明,PVA/PA复合膜在料液中w（IPA）%在0～95%范围内或在25℃～100℃的操作温度范围获得的渗透液中IPA含量[w′（IPA）]都小于1%,J随料液中w（IPA）%的下降或操作温度的提高而增加。分离性能预测方程的拟合结果与试验数据有良好一致性。在室温条件下,经过90 d的间歇运行或经过120 d的长期贮存后,PVA/PA复合膜的分离性能稳定,在IPA/水混合物的共沸温度80.4℃运行时的J为73.1 g/m^2·h,渗透液中的水含量[w′（H2O）]都大于99.5%,展示了其在食品、生物、制药和化学等工业中将具有良好的应用前景。     

Enhanced ethanol pervaporative selectivity of polydimethylsiloxane membranes by incorporating with graphene oxide@silica core-shell structure

A graphene oxide@silica core-shell structure (GO@silica) was prepared and embedded into the polydimethylsiloxane (PDMS) to fabricate mixed matrix membranes (MMMs). Meanwhile, (3,3,3-trifluoropropyl)triethoxysilane (TFTS) was employed to improve the compatibility between PDMS and GO@silica and create a hydrophobic membrane surface for improving the ethanol pervaporative performance. The scanning electron microscope (SEM) result showed that the resultant PDMS/GO@silica MMMs were smooth and defect-free. Meanwhile, the increase in hydrophobicity, swelling degree, and PV performance was achieved because of the incorporation of the modified GO@silica. The maximal separation factor of 11.43 coupled with a high permeation flux of 223 g·m⁻²·h⁻¹ was observed when separating a 10 wt. % ethanol/water mixture at 30°C. Moreover, the MMMs displayed a stable PV performance during a 168-h continuous operation.     

Thermodynamic efficiency of membrane-assisted distillation processes

Membrane processes are considered as comparably mild separation processes offering the potential for significant energy savings compared with azeotropic distillation processes. Despite higher investment and material costs, they are of particular interest for improving the energy efficiency in the chemical industry. However, energy savings of more than 20%–30% are rarely reported and even a general superiority can be disputed. To further elucidate this controversial, the current study pursues a quantitative assessment of the thermodynamic efficiency of pervaporation and vapor permeation processes with stand-alone distillation and hybrid membrane-assisted distillation processes for the separation of azeotropic mixtures. The results confirm the case-dependent potential of distillation processes to outperform membrane-assisted separations in terms of energy efficiency, considering proper heat integration. Although energy efficiency is becoming significantly important, it should be considered in the context of economic performance to determine an optimal trade-off and to select the best process alternative during conceptual process design.     

Preparation and characterization of PVA-g-GO/PVA/PAN composite membrane for pervaporation desalination

Graphene oxide (GO) has extensive applications in membrane-based separations, but its dispersion in the membrane has always been a problem due to the presence of π–π interactions in GO nanosheets. In this study, a grafting reaction was designed by using poly (vinyl alcohol) (PVA) for GO grafting modification and poly (vinyl alcohol)-g-graphene oxide (PVA-g-GO) nanocomposites were synthesized. The grafting material to GO was the same as the basic separation polymer material. PVA-g-GO showed better dispersibility and hydrophilicity than GO, and a series of composite membranes were prepared using a polyacrylonitrile (PAN) ultrafiltration (UF) membrane as a substrate. PVA-g-GO nanocomposites and membranes were characterized by using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), etc. The addition of PVA-g-GO improved both the separation performance and anti-swelling property of the composite membrane, and the PVA-g-GO/PVA/PAN composite membrane loaded with 2 wt.% PVA-g-GO obtained a high flux of 4.46 kg/m² · h and a high rejection of 99.99% when dehydrating 3.5 wt.% NaCl solution at 30°C by pervaporation.