微波场中NaA分子筛膜合成规律的研究

采用微波加热技术,常压回流条件下,在多孔氧化铝载体上制备出连续NaA分子筛膜,详细考察了放置方式、碱度、钠离子浓度以及合成次数对膜形成的影响.XRD和SEM表征结果显示,竖立放置和平置在顶部有利于提高膜的连续程度;高的碱度和高的钠离子浓度都不利于形成连续膜,反而溶解膜层;凝胶体系更易抑制转晶;在较短的合成时间里,多次合成有利于形成连续致密膜.     

高性能NaA分子筛-聚酰亚胺复合分离膜的制备及表征

采用微波加热法在a-Al2O3载体表面合成了NaA分子筛膜,通过对其浸渍镀膜及亚胺化处理制备出致密NaA分子筛-聚酰亚胺(PI)复合分离膜.采用XRD、FT-IR、SEM分析手段和气体渗透实验对NaA分子筛-Pl复合膜进行了表征.考察了NaA分子筛膜与NaA分子筛-PI复合膜的形貌、结构和渗透性能差异.XRD结果表明,...     

添加聚合物中间层对NaA分子筛膜的合成与性能的影响

采用浸涂法涂敷晶种,并通过二次生长法在α-Al₂O₂中空纤维外壁制备了NaA分子筛膜,考察了添加聚乙烯吡咯烷酮（PVP）中间层对成膜和膜分离性能的影响.采用扫描电镜（SEM）对膜的表面形貌进行表征,通过75℃渗透汽化分离质量分数为90%的乙醇/水溶液表征膜层的分离性能.研究发现,采用浸涂法涂敷晶种,无PVP中间层制备的膜层对乙醇/水溶液的分离因子仅为3 000左右,而添加了PVP中间层制备的膜层的分离因子可超过10 000.考察了PVP添加量对膜通量的影响.研究发现,添加了PVP中间层制备的膜（其分离因子>10 000）的通量比无PVP中间层的膜（浸涂-滚擦法涂敷晶种,分离因子>10 000）的通量[7.83 kg/（m²·h）]低,且随着制备中间层的PVP溶液浓度的升高,膜的通量相应降低,当PVP质量百分浓度分别为1%,3%和5%时,膜的通量分别为7.35,5.82和5.51 kg/（m²·h）.     

陶瓷中空纤维内表面动态水热合成NaA分子筛膜及其表征

采用动态水热法在氧化铝陶瓷中空纤维内表面原位合成了NaA分子筛膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)表征了分子筛膜的物相及微观形貌,通过渗透汽化测试考察了膜的乙醇/水分离性能,研究了合成工艺参数对成膜过程及膜质量的影响。结果表明,动态下合成的分子筛膜,晶体交联紧致,膜层薄且连续性好,厚度约4μm;提高动态速度有利于降低载体内外合成液的温差和浓度差,缩短晶化时间。在温度343K下,分离质量分数90%的乙醇/水体系,膜的渗透通量和分离因子可达1.03kg/(m2·h)和3 781,对乙醇/水表现出良好的分离效果和可重复性。     

继代晶种法合成NaA分子筛膜

开发继代晶种法合成低成本、易重复的NaA分子筛膜:采用前一代分子筛膜晶化后剩余的母液为晶种液,将其涂敷于载体表面,干燥后置于合成液中,并在微波加热条件下合成NaA分子筛膜.考察了初代母液合成时间对NaA分子筛膜的性能影响,渗透汽化性能测试结果显示:初代母液的合成时间和分子筛膜的晶化时间均为12.5 min时合成的NaA分子筛膜表现出最优的渗透汽化性能,渗透汽化温度为70℃时,其渗透通量达到1.25 kg/(m~2·h),分离系数达到10 000以上.采用优化的合成条件,用继代晶种法连续合成出五代NaA分子筛膜,其渗透汽化测试得到的乙醇脱水性能基本相同,表明继代晶种法可以重复合成性能优良的NaA分子筛膜.     

高岭土合成4A分子筛及其表征

采用ＴＧ－ＤＴＡ、ＸＲＤ、ＳＥＭ等现代测试技术以及测定钙离子交换量的方法研究了焙烧高岭土与碱液作用制备４Ａ分子筛的反应过程,给出了采用高岭土制备４Ａ分子筛扔最佳条件,并提出了以焙烧高岭土合成的４Ａ分子筛其形成机理应以异相成核为主,焙烧高岭土的碱液溶解为融洽上合成过程的控制步骤的新观点。     

煤系高岭土制备碱性分子筛材料

本研究以煤系高岭土为原料、NaOH溶液为浸取液,先于800℃煅烧2h得到偏高岭土,再在全密封反应釜中通过偏高岭土和NaOH溶液(固液比1∶20)之间的水热反应制备碱性分子筛(Na8(AlSiO4)6(OH)2.2H2O)。并采用X-射线衍射仪(XRD)、傅立叶转换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)和N2吸附脱附等测试手段对Na8(AlSiO4)6(OH)2.2H2O分子筛进行表征。结果表明,煤系高岭土经800℃煅烧后颗粒形貌不改变,平均尺寸2μm左右,碱浸取后变成分子筛微球;NaOH溶液的最佳浓度是4mol/l;Na8(AlSiO4)6(OH)2.2H2O分子筛具有狭缝状孔道,孔的形状和尺寸均匀,是一类典型的微孔-介孔分子筛材料。     

不同预植晶种法制备NaA分子筛膜及其表征

采用多种预植晶种法在管状ɑ-Al2O3外表面水热晶化制备NaA分子筛膜.使用XRD、SEM对合成的膜层进行形貌表征,并用渗透气化技术考察膜的醇水分离性能.结果表明,采取搽涂-浸渍法在支撑体表面预植晶种,并进行2次4h水热晶化成膜制备的膜性能最好,在343K进料液中乙醇质量分数为90%时分离因子与渗透通量分别为6824和1.40kg/(m2·h).并考察操作温度以及料液水含量对膜渗透汽化分离性能的影响.随料液中水含量的增加,分离因子先升高后下降,渗透通量呈增大趋势;随着操作温度升高,分离因子逐渐降低而渗透通量随之增加.     

流动体系中NaA分子筛膜的制备及渗透汽化分离性能研究

以液体硅酸钠、铝酸钠和氢氧化钠为原料,在一种流动体系中制备了工业应用规格的NaA分子筛膜,用XRD和SEM对分子筛膜的晶相结构和表面形貌进行了表征,所制备的NaA分子筛膜具有优良的渗透汽化分离性能.这种流动体系中制备分子筛膜的新方法从根本上避免分子筛合成过程中的浓度梯度问题,有利于制备均匀、连续、致密、分离性能优异的分子筛膜,特别适合于制备工业应用规模的分子筛膜.     

NaA分子筛合成残余物掺杂制备SiC膜支撑体

选用平均粒径100μm碳化硅为主要原料粉体,NaA分子筛合成废液中提取的粉体(主要成分为NaA分子筛和微量硅铝钠化合物)为烧结助剂,采用挤出法进行生坯成型,最后通过原位烧结技术制备高温气体净化用的管式碳化硅膜支撑体(外径60 mm,内径40 mm,长1 500 mm).研究结果表明,烧结助剂的最佳含量为质量分数3%,随着烧成温度的升高,碳化硅膜支撑体孔隙率逐渐减小,平均孔径也随之增加.当烧成温度达到1 150℃时,膜支撑体平均孔径为30.92μm,气体通量为99.32 m~3/(m~2·h·kPa),抗弯强度达到29.50 MPa,同时也表现出优异的抗热震性能和耐酸腐蚀性能,为高温气体净化碳化硅膜的低成本、绿色化制备以及应用研究提供了理论依据.     

Emulsion-based synthesis of NaA zeolite nanocrystals and its integration towards NaA membranes

NaA zeolite nanoparticles (seed crystals) of size 50–65 nm were synthesized using water-in-oil (w/o) type emulsions at a considerably low temperature of 65 ± 1°C in a short duration of 2 h. The emulsions were stabilized using non-ionic surfactants e.g. sorbitan monooleate (Span 80), sorbitan monolaurate (Span 20), polyoxyethylene(5)nonylphenylether with ethoxy numbers of 5 (Igepal CO-520) and polyoxyethylene sorbitan monooleate (Tween 80) of hydrophilic-lipophilic balance (HLB) values of 4.3, 8.6, 10 and 15 respectively. Among the surfactants, the intermediate HLB values of 8.6 (Span 20) and 10 (Igepal CO-520) were effective in synthesizing highly dispersible NaA nanoparticles of size 50–65 nm. The membrane prepared hydrothermally in multi-steps at 65 ± 1°C, using the Span 20-derived seed crystals deposited on porous support, showed the formation of high quality interlocked NaA coating. Single gas nitrogen (N₂) permeation of the membrane exhibited a permeance value of 1.01 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹ at ambient temperature (30°C).     

Hydrothermal synthesis of NaA zeolite membrane together with microwave heating and conventional heating

Uniform and dense NaA zeolite membrane was prepared by hydrothermal synthesis method together with microwave heating and conventional heating. The properties of the as-synthesized zeolite membrane were investigated by XRD, SEM and pervaporation evaluation for dehydration of 95 wt.% isopropanol/water mixture at 343 K, respectively. After microwave heating, the α-Al₂O₃ support surface was covered with homogeneous zeolite nuclei, which facilitated to form uniform, pure and dense NaA zeolite membrane in the following conventional heating process. High quality NaA zeolite membrane, i.e., with a separation factor (water/isopropanol) of 10,000 and a flux of 1.44 Kg/(m² h), could be hydrothermal synthesized together with microwave heating and conventional heating.     

Synthesis and characterization of 13X zeolite from low-grade natural kaolin

In this study, 13X zeolite was successfully synthesized from low-grade natural kaolin via alkali fusion followed by hydrothermal treatment, without extra Si source or dealumination. Fusion with NaOH, followed by hydrothermal reaction, kaolinite, illite and trace of quartz in kaolin sample were converted into zeolite. The effects of various factors during the synthesis process such as NaOH addition amount, crystallization time and temperature on the crystalline products were studied. The optimum synthesis conditions to get purity 13X zeolite were found to be alkali fusion of kaolin with the weight ration of NaOH/kaolin = 2.0 at 200 °C for 4 h, and crystallized at 90 °C for 8 h after homogenization by agitated at 50 °C for 2 h. The product was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and N₂ adsorption–desorption. The BET surface area of the product was found to be 326 m² g⁻¹. It can be concluded that the study provides the basic data and the process for extensive and efficient utilization of low-grade natural kaolin.