共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
用水热法在氧化铝陶瓷膜管上原位合成丝光沸石膜 总被引:2,自引:0,他引:2
The mordenite membrane was prepared on a α-Al 2O 3 tube by in situ hydrothermal synthesis. The crystallization was carried out at 443 K for 2~4 days. Silica sol and sodium aluminate were used as the sources of silica and alumina, respectively, and tetraethylammonium bromide (TEABr) as the template. The molar composition of the parent solution was 11 4Na 2O∶1 0Al 2O 3∶40SiO 2∶2500H 2O∶1 5TEABr. SEM and XRD were used to characterize the powder product and the composite membrane. The synthesized mordenite membrane proved to be in a full coverage and an excellent intergrowth. The mordenite crystals were about 20~30 μm and the thickness of the mordenite membrane was 30~40 μm. Based on the SEM pictures of the membrane in the early stage of hydrothermal synthesis, a growth model for the mordenite membrane was assumed. At first a gel layer was formed on the surface of the alumina tube. Nucleation took place in the gel layer but not at the interface of the gel layer and bulk solution. The gel layer provided the nutrients for the growth of zeolite crystals. After the gel layer was consumed completely, the zeolite crystals or membrane were exposed to the bulk solution. The membrane separation test on the mordenite membrane showed that the permeances of pure H 2 and N 2 at 298 K were 6 92×10 -7 and 1 81×10 -7 mol/(m 2·s·Pa), respectively. The ideal selectivity of H 2/N 2 was 3 82, which is higher than that of Knudsen mechanism. It suggested that the mordenite membrane had the ability of molecular sieving. 相似文献
4.
Sadao Araki Norito Mohri Yuichi Yoshimitsu Yoshikazu Miyake 《Journal of membrane science》2007,290(1-2):138-145
Cylindrical silica membranes with dead-end structure were prepared by an extended counter-diffusion chemical vapor deposition (CVD) method, in which a tetramethylorthosilicate (TMOS) silica source was fed from the outside of a cylindrical membrane support with γ-alumina interlayer (the membrane side), and oxygen gas was fed from the inside (the support side). Extended counter-diffusion CVD is a method of depositing silica films under highly pressurized conditions applied to the membrane side where TMOS is supplied. Two silica membranes were deposited for 10 h at 573 K under differential pressures of 0.1 MPa and 0.0 MPa applied between the cylindrical membranes. The hydrogen permeances for these silica membranes were unaffected (5 × 10−8 mol m−2 s−1 Pa−1 at 573 K), although the methane and carbon dioxide permeances were greatly reduced for dense silica films prepared by high-pressure CVD (HPCVD). Therefore, the selectivity of hydrogen over methane and carbon dioxide was 24,000, and 1200, respectively. It is suggested from energy dispersive X-ray microanalysis (EDX) observations in scanning electron microscopy (SEM) and scanning probe microscopy (SPM) results that this high selectivity was due to the reduced number of defects and/or pinholes formed in the dense silica membranes by HPCVD. 相似文献
5.
High-performance silicalite-1 membranes were synthesized on silica tubes by in-situ hydrothermal synthesis. By using the "solution-filling (SF)" method, the average flux of membranes with the SF method was improved by about 25% compared to that of the membranes without using the SF method; the flux and the separation factor of the membranes prepared with the SF method for an ethanol/water mixture at 60 ℃ were 0.99 kg/(m2·h) and 73, respectively. It was found that the membranes synthesized on silica tubes ex... 相似文献
6.
Pei Chen Xinbing Chen Xiangshu Chen Hidetoshi Kita 《Journal of membrane science》2009,330(1-2):369-378
The preparation of the supported titanium silicalite-1 (TS-1) zeolite membrane with inexpensive tetrapropylammonium bromide (TPABr)/weak base synthesis system was studied by three methods, and the catalytic activity of the obtained TS-1 zeolite membrane was evaluated with the oxidation of 2-propanol (IPA) under pervaporation condition. It was found that TS-1 zeolite membrane could be successfully prepared with “seeding” or “seeding in situ” method, but could not be achieved with “in situ” method. Adding a little amount of promoter ions of PO43− into the synthesis gel was of benefit to the catalytic activity of the prepared TS-1 zeolite membrane, but had no obvious effect on the membrane layer formation on the mullite porous support. For “seeding” method, the membrane prepared with the synthesis gel having molar composition of SiO2:0.1TPABr:0.9Et2NH:0.03TiO2:80H2O:0.06H3PO4 at 150 °C for 48 h showed the highest oxidation conversion of IPA of 72% accompanied by a flux of 0.35 kg/m2 h. Further more, much higher IPA oxidation conversion of 76% accompanied by a flux of 0.65 kg/m2 h was obtained for the TS-1 zeolite membrane prepared with the same synthesis gel by “seeding in situ” method at 150 °C for 72 h. 相似文献
7.
ZanLIU ZhiLinCHENG 《中国化学快报》2005,16(3):413-415
A defect-free SAPO-44 zeolite membrane firmly anchored the porous α-Al2O3 plate substrate was successfully synthesized. The separating results showed that the H2/N2 and H2/CO permselectivities were higher than those of the corresponding Knudsen diffusion and the substrate, attaining 5.78 and 7.15 respectively. 相似文献
8.
9.
Sergül Acikalin Gülmüs Levent Yilmaz 《Journal of Polymer Science.Polymer Physics》2007,45(22):3025-3033
Permeabilities of N2, Ar, O2, CO2, and H2 gases in PEMA (Polyethylmethacrylate) membranes have been measured above and below glass transition in the temperature range of 25–70 °C. The permeabilities of the gases were observed increasing with temperature. Arrhenius plot of permeability versus temperature data showed that there is a slope discontinuity at near to Tg of PEMA. In addition, the effects of membrane preparation parameters by solvent casting method (percentage of polymer in solvent, annealing temperature, annealing time, evaporation temperature, and evaporation time) have been investigated by using homogenous dense membranes of PEMA. It is observed that membrane preparation parameters strongly affect the membrane performance and the reproducibility of the permeability measurements. On the other hand, the effect of polymer structure on membrane performance has been investigated. Comparison of the permeabilities of N2, Ar, O2, CO2, and H2 gases in PEMA and PMMA membranes shows that PMMA membranes have smaller permeabilities and higher selectivities than PEMA membranes because of their higher glass transition temperature, Tg. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3025–3033, 2007 相似文献
10.
J.-M. Duval B. Folkers M.H.V. Mulder G. Desgrandchamps C.A. Smolders 《Journal of membrane science》1993,80(1):189-198
The effect of the introduction of specific adsorbents on the gas separation properties of polymeric membranes has been studied. For this purpose both carbon molecular sieves and zeolites are considered. The results show that zeolites such as silicate-1, 13X and KY improve to a large extent the separation properties of poorly selective rubbery polymers towards a mixture of carbon dioxide/methane. Some of the filled rubbery polymers achieve intrinsic separation properties comparable to cellulose acetate, polysulfone or polyethersulfone. However, zeolite 5A leads to a decrease in permeability and an unchanged selectivity. This is due to the impermeable character of these particles, i.e. carbon dioxide molecules cannot diffuse through the porous structure under the conditions applied. Using silicate-1 also results in an improvement of the oxygen/nitrogen separation properties which is mainly due to a kinetic effect. Carbon molecular sieves do not improve the separation performances or only to a very small extent. This is caused by a mainly dead-end (not interconnected) porous structure which is inherent to their manufacturing process. 相似文献
11.
The temperature dependences of nucleation of zeolite ZSM-5 and silicalite-I pass through extrema in the range from 110 °C to 120 °C. Despite having the same crystalline structures, zeolite ZSM-5 has a maximum and silicalite-1 has a minimum of nucleation in the temperature range mentioned. A method for preparation of single crystals of silicalite-1 up to 150 m in size has been developed. The comparison of the curves of the temperature dependences of nucleation for zeolites Na-X, Na-A, and ZSM-5 shows that the positions of the maxima on these curves are determined by the type of the crystal structure of zeolite.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1091–1095, May, 1996. 相似文献
12.
13.
14.
15.
ZhiLinCHENG ZiShengCHAO HuiLinWAN 《中国化学快报》2003,14(8):874-876
A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 rim. The gas H2/N2 mixture separating results indicated that the mixture selectivity increased with increasing of synthesis times. In addition, selectivity of the three-step synthesis was higher than the value(3.74) expected from Kundsen diffusion. 相似文献
16.
莫来石管上丝光沸石膜的合成与渗透汽化性能 总被引:1,自引:0,他引:1
采用不添加有机模板剂、配比为n_(Na_2O):n_(Al_2O_3):n_(SiO_3):n_(H_2O)=0.25:0.015~0.1:1:15~60溶胶,在涂有晶种的多孔莫来石管上水热合成出了丝光沸石膜。制备的膜经XRD和SEM表征。考察了合成时间、硅铝比、水硅比和硅源等因素对膜生长及其性能的影响。合成时间的延长有利于丝光沸石c轴方向的优先生长,然而优先取向生长膜层并未提高膜在水/乙醇分离体系中的渗透通量和选择性。优化条件下合成的膜具有较高的渗透汽化性能,在348 K、水/乙醇(10/90,W/W)混合溶液中的渗透通量和分离因子分别为0.70 kg·m~(-2)·h~(-1)。和860。基于XRD和SEM表征结果,高的渗透汽化性能可归结于在莫来石支撑层与较为疏松的表面晶体层之间形成的致密中间层。 相似文献
17.
Silicalite修饰的HY型分子筛及其对纤维素水解的催化性能 《燃料化学学报》2018,46(12):1447-1453
采用silicalite-1对HY型分子筛进行修饰,得到具有核壳结构的复合分子筛HY/silicalite-1。通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N2的吸附-脱附及吡啶吸附红外(Py-FTIR)等手段对不同晶化时间合成的HY/silicalite-1复合分子筛进行了表征,研究了复合分子筛对纤维素水解的催化性能。结果表明,晶化时间直接影响复合分子筛的晶体生长规律和两组分的相对含量,最佳晶化时间为16-24 h,所得到的复合分子筛外貌呈核壳结构,silicalite-1附晶生长在HY型分子筛的表面;随着晶化时间的延长,复合分子筛的表面由胶浊状变为光滑,最终变为鳞片状;其B酸量先减少后增加,而L酸量则先增加后减少。其中,晶化时间为24 h的HY/silicalite-1复合分子筛B酸量最大,L酸量最小,对纤维素水解反应具有良好的催化性能,葡萄糖收率由HY型分子筛催化获得的28.0%大幅提高至45.8%。 相似文献
18.
小晶粒丝光沸石膜的制备与表征 总被引:6,自引:0,他引:6
以四乙基溴化铵为模板剂,硅溶胶和铝酸钠分别为硅源和铝源,用水热合成法在氧化铝载体上合成出丝光沸石膜.用扫描电镜、X射线衍射和核磁共振等手段对所制得的沸石膜进行了表征,证明其交联良好、覆盖完全、附着强度高.通过采用晶化母液老化的方法,可使丝光沸石晶体的大小从20~30μm减小到4~5μm.小晶粒丝光沸石膜的渗透分离性能与大晶粒丝光沸石膜相比有较大的提高,其H2/N2的理想分离系数从3.82提高到9.80.丝光沸石膜在醇/水混合体系中能选择性地透过水,对水/甲醇、水/乙醇、水/正丙醇和水/异丙醇体系的最大分离系数分别为2600(水的摩尔分数xw=50%,T=323K),5500(xw=50%,T=343K),6000(xw=15%,T=343K)和6800(xw=50%,T=343K). 相似文献
19.
20.
Preparation and characterization of silicalite-1 membranes prepared by secondary growth of seeds with different crystal sizes 总被引:3,自引:0,他引:3
Y. Hasegawa T. Ikeda T. Nagase Y. Kiyozumi T. Hanaoka F. Mizukami 《Journal of membrane science》2006,280(1-2):397-405
MFI-type zeolite particles of 0.1–1 μm in diameter were prepared by adjusting tetra-n-propylammonium hydroxide (TPAOH) and water contents in synthesis mixtures. Using those particles as seeds, MFI-type zeolite membranes were prepared on the surface of a porous mullite tube by secondary growth. The membranes were formed as polycrystalline zeolite layers on and inside the porous support, and the membranes were composed of the [h 0 h]-oriented crystallites. The membrane consisting of a-oriented crystallites could be also prepared. However, the a-oriented zeolite layers were not active on the permeation properties of butanes. Rather the size and loaded amount of the seed particles influenced on the permeation properties through the membranes. As a result, the n-C4H10/i-C4H10 permselectivity could be increased to 220 by adjusting the size and the loaded amount of particles. These results suggest that the number of loaded particles affects on the permeation properties through the membranes. 相似文献