微孔二氧化硅分子筛膜的制备与应用

通过溶胶-凝胶热涂法制备高通量的微孔二氧化硅分子筛膜,并将其应用于渗透蒸发乙酸脱水,评价二氧化硅分子筛膜的分离性能;利用粒度分析仪和SEM对溶胶和膜层进行表征.结果表明,溶胶中二氧化硅颗粒的直径为10～80nm,无定形微孔二氧化硅分子筛膜对该体系显示了优异的分离性能,在353K时渗透蒸发分离水质量分数为5%的乙酸水溶液时,通量为0.65kg/(m2.h),分离系数达到120,经过35h的渗透蒸发实验后分离系数增高到160左右,通量基本不变为0.60kg/(m2.h).     

苯基修饰微孔SiO2膜的氢气分离和水煤气变换反应性能

通过正硅酸乙酯与苯基三乙氧基硅烷共水解缩聚反应制备苯基修饰SiO2膜,研究膜材料的氢气渗透和分离性能,并将其作为膜反应器的关键材料应用于水煤气变换反应.结果表明,氢气在苯基修饰SiO2膜中的渗透率随着温度的升高而增大,遵循活化扩散机理,300℃下H2渗透率达到4.67×10-7 mol/(m2·s·Pa),理想分离系数H2/CO、H2/CO2和H2/SF6分别达到10.54、10.50、21.16.在300℃,反应物H2O/CO摩尔比为2∶1的条件下进行水煤气变换反应,膜反应器的CO的转化率比传统固定床反应的CO的转化率高约12％,其原因是苯基修饰的SiO2膜对H2具有一定的选择性.     

Toroidal microporous silica gel

Microporous amorphous silica gel with a characteristic toroidal form of the elementary particles, has been prepared by thermal dissociation of a solution of silicic acid in a spray dryer. The substance obtained was investigated by electron microscopy, infra-red spectroscopy and thermal analysis. The adsorption properties were studied by lowtemperature adsorption of nitrogen.     

Asymmetric ceramic microporous membranes

Ceramic composite asymmetric microporous membranes were prepared for Micro- and Ultra-Filtration. The characterisation of their microporous separative layers was made by the nitrogen adsorption method, gas permeability measurements and SEM observations. This was connected with the characterisation of the corresponding composite substrates, as regards their morphology, structure and permeability. Certain anomalies, related to the intrinsic gas permeability of those separative layers, were observed in connection with the texture of their surface. These rough surfaces might play an important role in filtration or in gas separation processes. In order to evaluate a surface correction factor further studies are envisaged. Received: 30 March 2000     

十七氟癸基修饰的疏水二氧化硅膜材料的制备及氢气分离性能

通过溶胶-凝胶法,以正硅酸乙酯(TEOS)和十七氟癸基三乙氧基硅烷(PFDTES)为前驱体,在酸性和洁净室条件下制备了十七氟癸基修饰的SiO2膜材料,分别通过动态光散射技术、接触角测量、红外光谱以及热重分析等测试手段对溶胶的粒径分布及膜材料的疏水性能进行了表征,并深入研究了十七氟癸基修饰后膜材料的氢气渗透和分离性能.结果表明,当摩尔比n(PFDTES)/n(TEOS)=0.2时,溶胶的粒径狭窄分布在3.9nm.十七氟癸基已成功修饰到SiO2膜材料中,十七氟癸基的修饰使得膜材料从亲水性变为疏水性,在上述摩尔比例下,膜材料对水的接触角达到112.0°±0.6°.H2的单组分渗透率随温度的升高而增大,300℃时达到10.00×10-7 mol/(m2·s·Pa),H2/CO2的单组分理想分离系数及双组分分离系数分别达到6.10和13.30,均高于其Knudsen扩散分离因子(4.69),H2在膜材料中的输运主要遵循活化扩散机理.     

Reactive synthesis of microporous titanium-aluminide membranes

Titanium-aluminide intermetallic alloys and compounds are traditionally investigated and used as structural materials in high temperature applications. Here we show a novel field where microporous titanium-aluminide membrane with about 20 μm thickness was prepared by a reactive synthesis of a commercial aluminum foil coated with a titanium layer. The porous membrane with the average pore size of about 1.2 μm formed after sintering initially at 550 °C for 4 h and finally at 1300 °C for 30 min, showing a single phase of γ-TiAl. The pore evolution during the synthesis procedure was investigated and analyzed through scanning electron microscopy. The pore formation mechanism is believed to be the Kirkendall effect according to a Ti/Al diffusion couple experiment.     

聚丙烯微孔膜的表面工程

聚丙烯微孔膜的表面工程研究主要涉及:强调膜表面性质的膜过程开发、膜表面修饰与功能化方法的建立和优化、膜表面结构的表征及其与膜分离性能的关联,旨在深化对聚丙烯微孔膜材料表面特性的认识,进而拓展其应用范围.基于聚丙烯微孔膜表面的疏水性,首先简要介绍了气-液两相膜接触器传质行为的理论研究,随后重点总结了聚丙烯微孔膜表面亲水化与抗污染性能研究、表面仿生修饰与生物功能分离膜构建等方面的研究进展.     

A new technology of microporous polymeric membranes

It is demonstrated that microporous membranes can be obtained by perforating polymer films with the aid of a needle cliche perforator.     

Preparation of high silica microporous zeolite SSZ-13 using solid waste silica fume as silica source

Silica fume (SF) is a kind of solid waste that produced in the process of industrial silicon smelting. The disposal of SF for environmental problem is of great urgency. Here, a facile and novel one-step approach of high silica microporous materials SSZ-13 (SF-SSZ-13) were hydrothermally synthesized using silica fume (SF) as silica source. This method requires significantly shorter reaction times (48?h) compared to conventional SSZ-13. The as-synthesized SF-SSZ-13 exhibited high purity structure, popcorn-like morphology, and a large BET surface area of 545.74?m²?g^?1. Additionally, on the basis of controlled growth under different hydrothermal times, the formation mechanism of the SF-SSZ-13 outlined for further extension to other materials. The results on time- and energy-efficient of SF-based preparation of SSZ-13 pave the way for the reducing the cost of production of raw materials and decreasing environment load of solid waste, and also extend the application of silica fume.     

聚烯烃中空纤维微孔膜的研究与进展

介绍了聚烯烃中空纤维微孔膜的发展历史,对聚烯烃中空纤维微孔膜的拉伸致孔机理及其亲水改性研究进行了重点评述,着重讨论了亲水化改性对膜性能的影响,指出聚烯烃中空纤维微孔膜的应用领域和发展前景 。     

Hydrothermal stability of hematite and magnetite

Hydrothermal phase stability studies were carried out in the systems (a) Fe₂O₃-H₂O, (b) Fe₂O₃-H₂O-CO₂, (c) Fe₂O₃-H₂O-CO₂-H₂ and (d) Fe₂O₃-HNO₃. In the pure system Fe₂O₃-H₂O, onlya-Fe₂O₃ and Fe₃O₄ are the stable solids, with the phase boundary nearly pressure independent around 700°C. The introduction of CO₂ into the system catalyses the stability ofα-FeOOH in the system at low temperatures. The presence of H₂ in the system produces traces of Fe₃O₄ at temperatures as low as 230°C and at around 500°C, Fe₃O₄ is the only stable phase. The stabilisation of Fe₃O₄ is suppressed even up to 850°C, when NO ₃ ⁻ ion is present in the fluid phase.     

Sonication-assisted preparation of pristine MWCNT-polysulfone conductive microporous membranes

Conductive microporous membranes were fabricated by the phase inversion technique from pristine multiwalled carbon nanotubes (MWCNT)-polysulfone mixtures. A sonication-assisted method was used to disperse MWCNT in the polysulfone matrix without a covalent modification of the MWCNT or the use of surfactants. Electron Microscopy (SEM) and conduction tests were used to characterize the membranes. SEM pictures indicated that a concentration of 3% of MWCNT allowed a good dispersion of the nanotubes inside the hydrophobic polysulfone matrix. Current-voltage tests showed efficient electron percolation pathways across the membrane as a result of the successful dispersion of pristine MWCNT. These membranes will be applied in separation of charged species where microfiltration together with application of electric fields is needed.     

Hydrothermal synthesis and characterization of a zinc–cobalt phosphate microporous material

A new zinc–cobalt phosphate compound [Zn_(4−x)Co_x(PO₄)₂(HPO₄)][C₃H₄N₂]₃ (x≈0.25) (1) has been hydrothermally synthesized in the presence of imidazole as the template and crystallizes in the triclinic space group P−1 with crystal data a=9.6077(7) Å, b=9.8674(7) Å, c=12.3793(9) Å, α=77.569(4)°, β=78.040(4)°, γ=68.191(4)°, V=1053.52(13) ų, Z=2. Compound 1 exhibits an infinite two-dimensional layered structure, which is built up of {M₈P₆O₂₃} structural unit formed by vertex-sharing MO₄, MO₂N₂, MO₃N, PO₄ and PO₃(OH) (M=Zn, Co) moieties. A study of magnetic measurements indicates compound 1 has the well antiferromagnetic behavior.     

聚氨酯均质微孔膜的制备及结构控制的研究

采用溶液相转换法制备PU均质微孔膜,通过改变PU浓度、添加剂中盐粒大小及含量、凝固浴的组成及含量等制备条件,控制孔径分布、孔径大小和微观形态.通过电子显微镜观察到制备的PU微孔膜表面和底面孔径分布均匀,孔径大小可控,断面为规则的海绵状孔结构.     

KH-570修饰的SiO2膜制备及CH4/CO2的分离

采用KH-570代替部分TEOS为前驱物,共水解缩聚反应制得疏水性SiO2膜,通过IR、DTG、SEM、接触角测试仪等手段对KH-570修饰后的SiO2膜进行表征,并对CH4和CO2渗透和分离进行研究。实验结果表明,修饰后(0.8KH-570)SiO2膜接触角达到94.2°,红外光谱分析表明修饰后SiO2膜疏水性增强;(0.8KH-570)SiO2膜具有完整性及在400℃水热稳定性;压差30kPa,分离因子随涂膜次数增加先增大后减小,涂膜5次达最大值2.13,超越了努森扩散理论分离因子1.66,此时分离效果好;对于涂膜5次的SiO2膜,CH4渗透通量随压差增加呈现非线性微增趋势,CH4/CO2分离因子几乎不变。     

N-异丙基丙烯酰胺接枝聚乙烯微孔膜的结构形态和动电现象

用等离子体接枝法，在聚乙烯（PE）微孔膜上，接枝了具有温敏性的聚N－异丙基丙烯酰胺（PNIPAAm)。X射线电子能谱（XPS）、红外光谱（FT－IR）测试表明，PNIPAAm接枝链同时存在于N－异丙基丙烯酰胺接枝聚乙烯（NIPAAm-g-PE)温敏性接枝膜的微孔外表面及膜孔内部，接枝链在低临界溶解温度（LCST）32℃上下具有不同的形态结构。透过实验表明，接枝膜的水通量在LCST附近发生了5倍以上的急剧变化。流动电位研究表明，温度低于LCST时，接枝膜微孔表面zeta电位和电荷密度为较小的负值；温度高于LCST时，zeta电位和电荷密度仍为负值，但其绝对值急剧增加，并且随温度的升高继续增加。     

Palladium infiltration in high surface area microporous silica nanoparticles

Metallic Pd clusters were embedded into a host matrix of microporous SiO₂ nanoparticles via a solution reduction of Pd(NO₃)₂ by hydrazine hydrate. The infiltration of 33 wt.% Pd leads to a 13% porosity loss of SiO₂ nanoparticles, which demonstrated an initial surface area of 748 m²/g. The presence of Pd in the pores was demonstrated by EDS spectroscopy and by X-ray diffraction. The metallic guest species presumably reside in the accessible micropores with an estimated size about 1.3 nm. Hydrogen uptake was measured for Pd-infiltrated SiO₂ nanoparticles. A possible mechanism for the formation of composite nanoparticles is proposed based on electrostatic interaction between Pd²⁺ and SiO₂ nanoparticles.