b轴定向Silicalite-1沸石膜的合成

采用原位水热合成法.分别采用四丙基氢氧化铵(TPAOH)和四丙基溴化铵(TPABr)为模板剂,在不锈钢片上合成出了6轴定向的siIicalite-1沸石膜.采用x射线衍射(XRD)和扫描电镜(SEM)对膜的定向性和晶体形貌进行表征.通过XRD和SEM图可以看出,合成出的沸石膜为连续的,且定向性较好.比较采用两种模板剂所合成出的沸石膜可以看出,采用四丙基氢氧化铵(TPAOH)合成出的沸石膜比采用四丙基溴化铵(TPABr)合成出的沸石膜定向性好,成膜速度较快,但晶体尺寸较小.     

饱和ATP为原料合成多级孔ZSM-5沸石分子筛的制备与表征

研究以饱和ATP吸附材料为合成沸石分子筛的硅源,采用双模板法,用四丙基氢氧化铵(TPAOH)为微孔模板剂和十六烷基三甲基溴化烷(CTAB)为介孔模板剂直接合成多级孔ZSM-5沸石分子筛,通过XRD、SE M、比表面积及孔径分析仪进行N_2吸附-脱附等手段对多级孔ZSM-5沸石分子筛表征测试分析。结果表明:饱和ATP吸附材料在180℃下,水热提纯12 h获得硅源,再加入TPAOH和CTAB进行初始凝胶反应,后移入水热反应釜中,控温180℃,水热晶化反应15 h,即得多级孔ZSM-5沸石分子筛。     

ZSM-5分子筛膜的一次水热法合成及工艺探索

以四丙基氢氧化铵(TPAOH)为模板剂在自制的硅酸盐陶瓷支撑体上利用原位水热法一次合成了ZSM-5分子筛膜.讨论了影响合成分子筛膜的因素(碱度、晶化时间以及模板剂的用量),确定了最佳合成配比和晶化时间.利用X射线粉末衍射(XRD)和扫描电镜(SEM)对合成的粉末及膜进行了晶相分析和膜表面形貌表征,用N2对经过多次焙烧后的分子筛膜进行了渗透性能恻试.     

具有特殊形貌ZSM5分子筛的控制合成

采用水热合成的方法,以硅溶胶为硅源,分别以四丙基溴化铵(TPABr)和四丙基氢氧化铵(TPAOH)为模板剂,得到了不同尺寸和形貌的ZSM-5分子筛,采用X射线衍射(XRD)和扫描电镜(SEM)对分子筛样品进行了表征。结果表明:以TPABr为模板剂时,通过改变水含量,可制备出较高结晶度具有成束的棒状、花瓣形的片状和微米尺度的球状ZSM-5分子筛;以TPAOH为模板剂时,随乙醇用量增加,合成的分子筛结晶度逐渐提高,晶粒尺寸和形貌变化大,当乙醇与SiO2物质的量比为1.9时得到结晶度高、形貌均一、尺寸1~2μm、六角板状的ZSM-5分子筛。     

用不含有机模板剂的晶化液在多孔α-Al2O3管上合成ZSM-5沸石膜

采用不含有机模板剂的晶化液在平均孔径为2μm的多孔α-Al2O3管上合成了ZSM-5沸石膜.纳米ZSM-5沸石晶种的摩尔组成为9TPAOH25TEOS0.25 Al2O3480H2O.多孔α-Al2O3载体管外表面用这些粒度为100nm左右的晶种悬浮液浸涂、干燥后,依据纳米ZSM-5沸石晶种的DTA/TG进行煅烧,在不含有机模板剂的摩尔组成为67Na2OAl2O3240SiO26000H2O晶化液中合成了ZSM-5膜.XRD确定膜晶体为ZSM-5沸石,SEM表明沸石膜无缺陷,膜厚度约为8μm.制备的ZSM-5沸石膜H2的渗透率为1.50×10-6mol.m2·S-1.Pa-1,理想分离因数αH2/N2为3.85左右.     

用不含有机模板剂的晶化液在多孔α-Al2O3管上合成ZSM-5沸石膜

采用不含有机模板剂的晶化液在平均孔径为2μm的多孔α-Al₂O₃管上合成了ZSM-5 沸石膜.纳米ZSM-5沸石晶种的摩尔组成为9TPAOH:25TEOS:0.25 Al₂O₃:480H₂O.多孔α-Al₂O₃载体管外表面用这些粒度为100nm左右的晶种悬浮液浸涂、干燥后,依据纳米ZSM-5 沸石晶种的DTA/TG进行煅烧,在不含有机模板剂的摩尔组成为67Na₂O:Al₂O₃:240SiO₂: 6000H₂O晶化液中合成了ZSM-5膜.XRD确定膜晶体为ZSM-5沸石,SEM表明沸石膜无缺陷,膜厚度约为8μm.制备的ZSM-5沸石膜H₂的渗透率为1.50×10-6mol·m²·s^-1·Pa^-1,理想分离因数α_H/N2为3.85左右.     

低介电常数纯硅数分子筛薄膜的制备与表征

介绍了一种制备具有低介电常数氧化硅分子筛薄膜的新方法.以正硅酸乙酯为硅源,四丙基氢氧化铵(TPAOH)为模板剂和碱源,采取水热晶化技术,通过原位法在硅晶片表面制备出纯二氧化硅透明分子筛薄膜;采用紫外光解法脱除分子筛薄膜孔道内的模板剂,制备出具有低介电性能的氧化硅分子筛薄膜.使用FT-IR,XRD和SEM对样品进行了结构表征,并采用阻抗分析仪测量了薄膜的介电常数,采用纳米硬度计测量薄膜的弹性模量和硬度.     

中孔FAU型沸石的合成及孔结构表征

本研究采用有机硅烷偶联剂二甲基十八烷基[3-(三甲氧基硅基)丙基]氯化铵(TPOAC)作为中孔模板剂, 在水热条件下合成了具有FAU结构的中孔X和Y型沸石, 并用X射线衍射、扫描电镜、透射电镜、氮气吸附/脱附和热重分析技术对合成样品进行了结构表征。结果表明, 在该沸石合成体系中TPOAC的加入使沸石晶粒纳米化, 同时可在沸石晶粒内部创造丰富的直径为5~6 nm的中孔, 并且改变了沸石晶体的外观形貌。从而获得了不仅保持沸石固有微孔、同时具有晶内中孔和晶间中孔的介孔FAU沸石。     

晶种导向蒸汽辅助晶化法全硅BETA沸石的合成研究

全硅BETA沸石在卷烟烟气减害和石油化工领域有较好的应用前景。利用单模板剂合成方法——晶种导向蒸汽辅助晶化法(SAC)合成了全硅的BETA沸石。利用X射线衍射(XRD)、扫描电镜(SEM)、红外(FT-IR)和氮吸附对样品进行了分析。结果表明, 晶种量、模板剂四乙基氢氧化铵(TEAOH)和碱度对全硅BETA沸石的合成有着重要的影响。同时还发现, 利用SAC法合成的全硅BETA沸石晶体中, 四方晶系(A晶型)占有58%~68%, 并且原料的配比不影响A晶型的丰富程度。全硅BETA沸石具有一定疏水性, 有望用于有机物/水分离体系。     

添加有机胺对钛硅沸石的合成和催化性能的影响

在用合成TS-2后的过滤液（简称母液）添加其它有机胺作模板剂合成钛硅沸石的研究中,发现添加四乙基氢氧化铵（TEAOH）溶液有促进TS-2沸石晶粒显著长大和骨架钛含量提高的作用;加乙二胺使合成的TS-2中混有少量的TS-1杂晶;加入正二丙胺合成的沸石已完全转晶为TS-1,而且其晶体形貌也有显著的改变．这种添加效应进而影响钛硅沸石作为苯酚羟基化的氧化催化剂和作为氧化苯乙烯重排反应的弱酸催化剂的催化性能．     

Preparation and characterization of titanium-containing MFI from highly siliceous ZSM-5: effect of precursors synthesized with different templates

Titanium-containing MFI zeolites (Ti-ZSM-5) have been prepared by gas–solid reaction between highly siliceous ZSM-5 precursors synthesized with different organic molecules, and TiCl₄ vapor at elevated temperature. XRD, FT-IR, UV-Vis, ²⁹Si and ²⁷Al solid NMR techniques are used to characterize precursors and Ti-ZSM-5 zeolites. Highly siliceous ZSM-5 synthesized with different templates possesses different amount of internal silanol groups clustered as silanol nests in framework. When the precursor is contacted with TiCl₄ vapor at elevated temperature, titanium atoms are incorporated into the tetrahedral sites by the reaction between TiCl₄ and silanol nests, not by the isomorphous substitution of titanium for framework aluminium or/and silicon. Highly siliceous ZSM-5 precursor synthesized with NBA, TEABr or HDA template possesses relatively large amount of internal silanol groups, and then obtains high concentrations of framework titanium after contacted with TiCl₄ vapor, compared to those synthesized with TPAOH or TPABr template. In addition, Ti-ZSM-5 with precursors obtained by using NBA, TEABr or HDA template can occupy higher catalytic activity in the epoxidation of propylene with diluted hydrogen peroxide.     

Synthesis of MFI-type zeolite membranes on porous α-alumina supports by wet gel crystallization in the vapor phase

A new method has been developed for synthesis of MFI-type zeolite membranes on porous -alumina supports. Using this method, a thin layer of wet-gel precursor precoated from a synthesis sol containing SiO₂, tetrapropylammonium hydroxide (TPAOH), NaOH, and H₂O was converted to an MFI zeolite film by vapor-phase treatment at elevated temperatures. MFI zeolite films were formed on the -alumina substrates, respectively, in the vapor phases of TPAOH solution and an ethylenediamine(EDA)/triethylamine (TEA)/water mixture, but an amorphous material was obtained in the vapor phase of pure water. Scanning electron microscopy and helium permeation examinations before calcination showed that the MFI membrane obtained in the vapor phase of the TPAOH solution was of higher quality than that synthesized in the vapor phase of the EDA/TEA/water mixture in terms of zeolite film integrity and compactness. It was also found that the existence of the template TPA⁺ in the parental synthesis sol was critical to the formation of MFI zeolite under the investigated conditions. When precursor layers coated from a template-free colloidal silica system were used, the vapor-phase treatment resulted in formation of Na-P1 and ANA zeolite films, respectively, in the vapors of TPAOH solution and the EDA/TEA/water mixture. The method developed in this work has the advantages of improved controllability, minimal waste generation, and reduced chemical consumption that are desirable for large-scale production of zeolite membranes.     

An efficient synthesis of nanocrystalline MFI zeolite using different silica sources: A green approach

Nanocrystalline MFI zeolite was synthesized with a very broad range of silica to alumina ratios using an autoclave for periods of 7 h at 473 K under autogeneous pressure without seeding gel, promoter, organic solvent or sulfuric acid. The procedure has been successfully employed for the synthesis of MFI samples using fumed silica, colloidal silica, aerosil and tetraethylorthosilicate as silica sources. The synthesized samples were characterized by different techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy. Their average crystallite size ranges from about 26 to 55 nm and they exhibit high crystallinity.     

Highly selective zeolite membranes as explosive preconcentrators

Highly selective thin zeolite MFI membranes are synthesized on porous stainless steel and α-alumina supports using a seeded growth method. An ultraviolet (UV) light treatment is employed as a low temperature alternative to remove the organic structure-directing agent (SDA) to avoid membrane cracking. The feasibility of the use of the MFI membranes as an explosive preconcentrator is examined by measuring the permeation of nitrogen (N(2), an air surrogate) and 1,3,5-trimethylbenzene (TMB) (a 2,4,6-trinitrotoluene (TNT) surrogate) in a mixture of N(2) and TMB. High N(2)/TMB selectivity (>10?000) and reasonable N(2) flux (13.5 mmol/m(2)·s) are observed. On the basis of the flux, a hollow fiber array based preconcentrator is proposed and estimated to provide 1000× concentration within about 1 min using a hollow fiber with a 50 μm internal radius. This high performance explosive preconcentrator may open a new venue for the detection of subppb or lower level of explosives simply in conjunction with conventional explosives detectors.     

Synthesis and characterization of silicalite powders and membranes with micro–meso bimodal pores

Silicalite sols containing silicalite agglomerates of 150–380 nm in size were synthesized by hydrothermal synthesis for 0.5–3 days. Silicalite powders and supported silicalite membranes containing micro-meso bimodal pores were prepared by the sol–gel method using these silicalite sols. The silicalite powders contain intracrystalline zeolitic pores (0.54 nm) and intercrystalline mesopores of about 3–4 nm in diameter. For the silicalite powders the mesopore size decreases and mesopore surface area increases with increasing silicalite agglomerate size as a result of a change of the shape of silicalite agglomerates from round to more faceted one. Continuous silicalite thin films of thicknesses ranging from 3 μm to 12 μm were made on α-alumina by the sol–gel dip-coating method. The supported silicalite membranes also contain both zeolitic pores and mesoporous intercrystalline pores. The single gas He permeance of the 3 μm thick α-alumina supported silicalite membrane was found to be from 2.7 × 10⁻⁶ to 3.3 × 10⁻⁶ mol/m² s Pa. These bimodal pore zeolite powders offer the potential as catalysts and sorbents with improved efficiency. The bimodal pore zeolite membrane can be used as support for zeolite and other membranes and as compact packed-bed reactor for chemical reaction.     

新型两亲性嵌段共聚物导向合成有序大孔径介孔材料的研究进展

自从1992年首次报道介孔氧化硅分子筛M41S系列以来, 人们采用各种商业化表面活性剂为模板, 合成了多种骨架组成、丰富的有序介观结构、不同孔径尺寸的介孔材料, 并将其应用在能源、环境、催化等诸多领域。然而, 由于常规商业化模板剂的分子量大小有限, 合成的介孔材料具有较小的孔径(< 8.0 nm), 从而极大地限制了其面对大尺寸客体分子的相关应用。此外, 利用常规模板剂难以合成出具有晶化墙壁的介孔金属氧化物材料。近年来, 大分子量两亲性嵌段共聚物相继被报道用来合成新型介孔材料, 本文将综述基于这种嵌段共聚物为模板剂合成各种具有大孔径和晶化墙壁介孔材料的研究进展。     

Nanocrystalline zeolite beta: The effect of template agent on crystal size

Zeolite beta was hydrothermally synthesized using the method reported by Camblor et al. [M.A. Camblor, A. Corma, A. Misud, J. Perez-Pariente, S. Valencia, Stud. Surface Sci. Microporous Mater. 105 (1997) 341]. The influence of template agent, aluminum content and gel dilution on the crystalline size of zeolite beta was carefully studied. When the crystalline size reduces from 500 to 30 nm, the pore volume particularly the mesopore volume of zeolite beta significantly increased. The experimental results also evidenced that more template agent employed in the initial gel resulted in smaller crystalline sizes of zeolite beta whereas the water content has little effect on the crystalline size. This is the first work that demonstrates the important role of the template content in the initial gel in the determination of the crystalline size of nanosized zeolite beta.     

Catalytic decomposition of 1,2-dichlorobenzene using Pt-loaded nanoporous zeolite MFI catalyst

Nanoporous zeolite MFI was prepared by using HClO4 as a promoter. A significant proportion of the synthesized zeolite MFI nanoparticles exhibited nanoporous characteristics. Although the synthesis of the zeolite MFI was completed within 6 h, the crystallinity of all the zeolite MFI was shown to be high. The synthesis time of approximately 6 h used in this study was much shorter than the conventional hydrothermal method. The feasibility of the new nanoporous zeolite MFI towards the gas phase catalytic oxidation of a model for dioxin, 1,2-dichlorobenzene, was tested by comparing the catalytic activity of Pt/nanoporous zeolite MFI with that of a Pt/gamma-Al2O3 catalyst. The catalytic activity of the Pt/nanoporous zeolite MFI was higher than that of the Pt/gamma-Al2O3 catalyst. The internal surface area and acidity appears to be a major factor for the decomposition of 1,2-dichlorobenzene.     

Hierarchical nanofabrication of microporous crystals with ordered mesoporosity

Shaped zeolite nanocrystals and larger zeolite particles with three-dimensionally ordered mesoporous (3DOm) features hold exciting technological implications for manufacturing thin, oriented molecular sieve films and realizing new selective, molecularly accessible and robust catalysts. A recognized means for controlled synthesis of such nanoparticulate and imprinted materials revolves around templating approaches, yet identification of an appropriately versatile template has remained elusive. Because of their highly interconnected pore space, ordered mesoporous carbon replicas serve as conceptually attractive materials for carrying out confined synthesis of zeolite crystals. Here, we demonstrate how a wide range of crystal morphologies can be realized through such confined growth within 3DOm carbon, synthesized by replication of colloidal crystals composed of size-tunable (about 10-40 nm) silica nanoparticles. Confined crystal growth within these templates leads to size-tunable, uniformly shaped silicalite-1 nanocrystals as well as 3DOm-imprinted single-crystal zeolite particles. In addition, novel crystal morphologies, consisting of faceted crystal outgrowths from primary crystalline particles have been discovered, providing new insight into constricted crystal growth mechanisms underlying confined synthesis.