共查询到19条相似文献,搜索用时 62 毫秒
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引 言沸石分子筛具有均匀的分子尺寸微孔结构和良好的热稳定性、机械强度、催化作用 ,是当前无机膜材料研究的热点之一 .沸石分子筛膜合成方法主要有原位水热合成法和汽相合成法 ,应用这些方法已成功合成出A型[1] 、Y型[2 ] 、P型[3 ] 、MFI等[4 ] 等沸石分子筛膜 .A型沸石分子筛由于具有0 .3~ 0 .5nm的有效孔径和三维孔道结构 ,亲水性强 ,有可能在小分子气体如低碳烃类分离及有机物脱水等方面得到应用 .Jansen等[5] 认为晶体粒径愈大 ,产生堆积孔径愈大 ,所合成的沸石分子筛膜存在缺陷可能性愈大 .但从文献报道看 ,沸石分… 相似文献
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介绍了分子筛渗透汽化脱水装置的优点,总结1000 t/a分子筛渗透汽化乙醇脱水装置的运行情况,包括成品水分,渗透液乙醇含量的情况。根据实际运行情况核算装置运行成本,并与萃取精馏工艺运行成本作比较。分析了再沸器气化无法除去弱碱、弱碱盐、弱酸、可挥发性酸及弱酸弱碱盐的原因,及这些杂质对p H值和电导率的影响。提出了除去不同杂质的解决方案。 相似文献
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针对乙醇和叔丁醇反应制备乙基叔丁基醚(ETBE)时产物水的阻碍效应所造成的ETBE收率不高的问题,提出以中空纤维NaA分子筛膜为核心元件,构建渗透汽化膜反应器(PVMR),使反应生成的水能够通过渗透汽化作用高效地在线脱除.通过与普通反应器的对比实验发现,料液初始醇比的升高可以抑制副反应的进行,提高ETBE的最终收率,但... 相似文献
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利用二次生长法在不锈钢片式支撑体上合成出Na A分子筛膜。采用XRD、FE-SEM和渗透汽化分离技术对所合成的膜进行了系统表征。研究结果表明所合成的膜具有(200)面取向性,并且合成时间和合成次数对膜的取向性以及分离性能有重要影响。在2次3.5h的合成条件下,所制备的膜具有较优的取向性和分离性能,其XRD图谱上NaA分子筛(200)面与(220)面的峰强比值达到22,远高于无取向NaA分子筛膜的峰强比值。该膜在343 K下分离含水量5 wt.%的乙醇溶液时,其水/乙醇分离因子和渗透通量分别为1290和1.12kg·h-1·m-2。 相似文献
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《分离科学与技术》2012,47(1):136-141
NaA zeolite membranes have been used for dehydration of organic solvents in laboratory and commercial scales. There are many synthesis methods and conditions for manufacturing the membranes. The use of lactescent and clear gel solutions are two of the most important choices for high quality hydrothermal synthesis of NaA zeolite membrane in gas separation or dehydration of organic solvents. In this article, effect of hydrothermal synthesis time was investigated using the clear gel solution (Al2O3:5SiO2:50Na2O:1000H2O). Phase transformation from NaA to NaX was recognized as the most possible event when the clear gel solution was used. XRD spectra, SEM images, and GC analyses were used for evaluation of zeolite crystal phase, the membrane layer quality, and the contents of organic substances (ethanol or 2-propanol) in feed and permeate streams in pervaporation tests, respectively. From synthesis of zeolite membrane at different times, it was revealed that for achieving the pure NaA zeolite phase the synthesis time should not exceed 3 h at 100°C. 相似文献
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《分离科学与技术》2012,47(11-12):2035-2048
Abstract Aromatic polyetherimide membranes were prepared by the phase inversion method and tested for the pervaporation separation of water from isopropanol with emphasis on the breaking of azeotropic composition and the dehydration of high concentrations of isopropanol. It was found that the membrane selectivity was enhanced by partial evaporation of the solvent in the cast polymer films prior to the gelation step during membrane formation. The membrane performance was shown to be dependent on the feed concentration and the operating temperature. At a feed temperature of 25°C and a permeate pressure of 133 Pa, separation factors of 173 and 384 were achieved for the dehydration of isopropanol solutions at 0.68 (azeotropic composition) and 0.96 mole fractions isopropanol, respectively, with reasonably high permeation rates. The utility of the membranes for the proposed separation was demonstrated; however, these membranes were not prepared under optimized conditions and thus a continuous study is required to rationalize the effects of membrane preparation parameters on membrane performance. 相似文献
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《分离科学与技术》2012,47(15):3071-3091
Abstract NH4Y zeolite‐filled chitosan membranes were developed for the separation of water‐isopropanol mixture using pervaporation process. The NH4Y zeolite‐filled chitosan membranes were prepared using a solution technique with the variation of NH4Y zeolite loading (0, 0.1, 0.2, 0.3, 0.4, 0.5 wt.%). The membranes morphologies were studied using Scanning Electron Microscopy (SEM) and the membranes mechanical strength were tested using the parameter of tensile strength and percent strain at maximum. The effects of NH4Y zeolite loading on the liquid sorption characteristics and pervaporation performance were also evaluated. The diffusion coefficient of water and isopropanol for the chitosan membranes at different NH4Y zeolite loading is estimated. The presence of NH4Y zeolite in the chitosan membranes caused non‐homogeneous dispersion of NH4Y zeolite crystals and membrane swelling due to its hydrophilic properties. However, the presence of NH4Y zeolite was able to improve both tensile strength and percent strain at maximum of chitosan membranes. The presence of NH4Y zeolite also increased the total permeation flux and separation factor simultaneously. The Pervaporation Separation Index shows that 0.2 wt.% of NH4Y zeolite‐filled membrane gave the optimum performance in the pervaporation process. The diffusion coefficient estimated proves that the membranes were highly water selective. 相似文献
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偏二甲肼传统的工业生产方法危险且能耗极大,渗透蒸发是一种新型的膜分离技术和清洁生产技术,受其膜材料的限制未能广泛应用,随着新型膜材料的出现打破这一瓶颈.在分析新型沸石膜用于醇/水等有机混合物脱水的应用研究基础上,讨论了将沸石膜应用于偏二甲肼脱水的可行性及待进一步研究的主要问题. 相似文献
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《分离科学与技术》2012,47(4):523-536
The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10?12 kmol · m/m2 · s · kPa in PDMS to 5.1 × 10?12 kmol · m/m2 · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10?12 kmol · m/m2 · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane. 相似文献
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采用二次生长法,在无有机模板剂的条件下于a-Al2O3载体上制备丝光沸石膜. 所制丝光沸石膜用于四氢呋喃(THF)水溶液脱水浓缩,考察了操作温度、THF浓度对其渗透汽化性能的影响. 结果表明,在操作温度为60℃、THF浓度为90%(w)时,丝光沸石膜的渗透通量和分离因数分别为0.35 kg/(m2×h)和9233,渗透液水含量达99.907%(w). THF浓度在75%~97%范围内,渗透液的水含量均在99.6%以上. 对THF浓度为97.066%(w)的模拟制药废液脱水37 h后,THF浓度达99.640%. 相似文献
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