Controlled growth for synthesizing a compact mordenite membrane

Controlling the growth of zeolite crystals on a porous alumina support is essential for preparing a compact zeolite membarne. First, mordenite seed crystals applied on a nonporous -alumina disk were grown and morphological change of mordenite crystals were observed in the course of growth. Then, mordenite membranes were synthesized on a porous -alumina tube under the same conditions employed in the study using the alumina disks. We found that seed crystal growth was widely controllable by changing water content in reaction solution, which resulted in better control of the morphology of mordenite crystals for synthesizing a thin compact mordenite membrane. Separation properties for mordenite membranes were studied in water–hydrogen binary system at 473 K with 10 kPa of water partial pressure, where no capillary condensation was expected in non-zeolitic pores. Separation factor for a mordenite membrane with a few defects was poor; however, a defect-free mordenite membrane prepared under a suitable condition highly separated steam from hydrogen.     

The use of post-synthetic treatments to improve the pervaporation performance of mordenite membranes

The pervaporation performance of mordenite membranes prepared by seeded hydrothermal synthesis was improved by a new post-synthetic treatment in which the membranes were hydrothermally treated at 180 °C under moderately alkaline conditions. The effect of the post-synthetic treatment was evidenced by pervaporation measurements, X-ray diffraction, scanning electron microscopy and chemical analysis of the solution after treatment. The post-synthetic treatment was found to be highly effective to improve the performance of mordenite membranes in the pervaporation of water/ethanol mixtures. The dissolution of Si-rich amorphous and zeolitic materials, possibly combined with further crystallization processes during post-synthetic treatment are invoked to explain the results obtained.     

Direct conversion of methane to methanol over Cu exchanged mordenite: Effect of counter ions

Direct conversion of methane(CH4)to methanol(DMTM)is a promising,but very challenging process for the utilization of abundant CH4 as a low carbon resource.In this context,Cu loaded zeolites,mordenite(MOR)in particular,were recognized as the most effective system to perform DMTM.In this work,different Cu salts were used to exchange with MOR,by which the effect of counter ions on the catalytic performance towards DMTM was investigated.The prepared catalysts were characterized and evaluated systematically.It was found that the counter ions affected the speciation of Cu sites,probably due to their capability in extraction of protons from MOR and the influence on the hydrolysis state of the Cu2+in aqueous solution.These behaviors adjusted the association between Cu2+and the exchangeable protons in MOR.As a result,varied DMTM performance was observed.Among the used Cu salts,Cu(CH3COO)2 exchanged MOR showed the highest performance,achieving stable CH3 OH yield of 117±28μmol/g in 5 consecutive cycles,these values are among the highest for Cu loaded MOR zeolites in open publications.     

水热合成法在分子筛中组装功能材料

采用水热合成法将ZnS、MoO₃和邻苯二甲酸铕组装到ZSM-5分子筛孔道之中,制得了具有纳米尺寸的功能材料,通过XRD、IR、发射光谱和探针分子吸附等手段进行了表征.     

高渗透率ZSM-5沸石膜的合成

沸石膜具有规整的孔道结构和统一的孔径 ,而且耐高温、耐化学侵蚀 ,因而在高温气体分离、蒸汽分离和催化 -分离一体化方面具有广阔的应用前景 ,尤其对烃类异构体如正、异丁烷 ,二甲苯异构体的分离显示了良好的分离性能[1] .沸石膜的合成研究已有很多报道[2～ 7] ,在 ZSM-5沸石膜合成中用到的模板剂均为昂贵的 TPABr或 TPAOH,且从渗透分离数据看 ,它们都具有良好的分离选择性 ,但渗透率不高 ,如 H2 的渗透率在1 0 - 7mol/(m2·s·Pa)数量级 ,这就制约了膜的应用 ,因此 ,探讨具有高选择性和大渗透量的沸石膜的合成显得尤为重要 .本文直…     

羟基自由基在沸石分子筛合成中的作用

沸石分子筛由于具有独特的形选催化作用及可调的酸性, 已成为化学工业中最重要的固体催化材料. 沸石分子筛的合成主要基于碱性条件下的水热晶化, OH^?被认为起到催化硅铝物种的解聚及聚合作用. 近年来, 研究者发现了羟基自由基加速分子筛的水热晶化机制. 通过利用紫外光照射或芬顿反应等物理或化学方法向分子筛合成体系引入羟基自由基, 可以实现沸石分子筛的加速晶化及高硅沸石分子筛的合成. 理论计算结果表明, 羟基自由基可以促进Si—O—Si 键的断裂和重新生成, 从而显著加快分子筛成核并促进硅原子进入骨架. 本综述介绍了羟基自由基在沸石分子筛晶化方面的最新研究进展, 探讨了羟基自由基的主要作用和优势, 并对沸石分子筛合成的羟基自由基路线发展前景进行了展望.     

Adsorption characteristics of synthesized mordenite membranes

Nitrogen adsorption at 77 K was measured for a self-supporting mordenite membrane synthesized on and detached from, a polytetrafluoroethylene (PTFE) substrate, and for a simultaneously formed powder. The adsorption by the membrane saturated an amount which was about half that found for adsorption by the powder. To examine this difference in adsorption characteristics, both of powder and membrane were measured for adsorption for water, methanol,n-hexane andtert-butyl alcohol. For methanol,n-hexane andtert-butyl alcohol, the powder and membrane both showed the same adsorption behavior as for nitrogen. When water molecules were adsorbed, however, there was no difference in saturated adsorption amount between powder and membrane, suggesting the presence of deformed pores in the rectangular crystal layer of the mordenite membrane. The deformed pores are assumed to occur as gaps among crystallites which displaced along theab planes of the rectangular crystals, forming the rectangular crystal layer. The channel bonding sites resulting from such displacement were found to serve as pore walls against adsorbable molecules which have a cross-sectional area greater than that of the water molecule. and so to hinder their entrance into the deformed pores. X-ray diffraction analysis revealed that the rectangular crystals have no periodic, continuous structure along thec-axis; they show a slight distortion of the crystallite shift from the plane perpendicular to thec-axis.     

脱铝丝光分子筛应用于MTP反应:Al的落位和晶体形貌的影响

甲醇制烯烃/丙烯工艺(MTO/MTP)是当前煤基碳资源绿色催化转化的重要过程之一.在MTO/MTP工艺中,分子筛通常面临低碳烯烃选择性低、水热稳定性差和寿命短等挑战.开发高选择性和高稳定性的分子筛催化剂对煤基乙烯/丙烯等化学品的工业生产具有重要意义.本文选择了具有12元环孔道的低硅丝光分子筛(Si/Al=6)为母体,对...     

间歇式水热合成制备丝光沸石膜及其异丙醇脱水应用

采用市售廉价大孔α-Al₂O₃管作为基质材料,通过热浸渍法在管外表面涂敷晶种,随后在无模板剂体系下,利用新型的间歇式水热合成法制备丝光沸石膜。对比了传统加热和间歇式加热对丝光沸石膜形貌、结构及渗透蒸发异丙醇脱水分离性能的差异。考察了合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比在间歇式水热合成下对丝光沸石膜的影响。研究结果表明,当合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比分别为0.24、16.7和0.25时,制备的丝光沸石膜渗透蒸发异丙醇脱水分离性能最佳,在75℃下,对异丙醇/水(9:1,w/w)的渗透通量达5.60 kg·m^-2·h^-1,水对异丙醇的分离因数大于10 00...     

间歇式水热合成制备丝光沸石膜及其异丙醇脱水应用

采用市售廉价大孔α-Al₂O₃管作为基质材料,通过热浸渍法在管外表面涂敷晶种,随后在无模板剂体系下,利用新型的间歇式水热合成法制备丝光沸石膜。对比了传统加热和间歇式加热对丝光沸石膜形貌、结构及渗透蒸发异丙醇脱水分离性能的差异。考察了合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比在间歇式水热合成下对丝光沸石膜的影响。研究结果表明,当合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比分别为0.24、16.7和0.25时,制备的丝光沸石膜渗透蒸发异丙醇脱水分离性能最佳,在75℃下,对异丙醇/水(9∶1,w/w)的渗透通量达5.60 kg·m^-2·h^-1,水对异丙醇的分离因数大于10 000。     

A study on the preparation and characteristics of zeolite membrane PLOT column by in-situ synthesis

Summary The preparation of a zeolite membrane PLOT column by in-situ synthesis is described. The advantages of this new column are discussed. Some analytical applications to alkanes, arenes, esters, alkyl halides and ethers on the zeolite membrane PLOT column compared with those on a coated zeolite PLOT column are reported.     

真空原位水热合成法快速合成A型分子筛膜

采用真空原位水热法在管状αAl2O3基膜上快速合成了A型分子筛膜;采用XRD和SEM方法表征了膜的性质;研究了真空度对A型分子筛膜性能的影响。在外加真空作用下,分子筛晶粒可以均匀、快速地迁移到基膜表面形成分子筛膜,从而可以在较短时间里合成均匀、连续的分子筛膜。     

层状磷酸铝化合物Na4[Al4P4O18]·H2O的合成及质子电导性能研究

在无有机模板剂的条件下, 以Na⁺离子为结构导向剂, 通过水热合成法制备了一种与利用1,3-丙二胺合成的Uio-14具有相同层结构的二维磷酸铝化合物Na₄[Al₄P₄O₁₈]·H₂O(1), 通过单晶X射线衍射确定了其拓扑结构. 利用粉末X射线衍射、 扫描电子显微镜、 电感耦合等离子体( ICP)元素分析和热重分析等对其物理化学性质进行了表征. 结果表明, 化合物1属于单斜晶系, 空间群为P2₁/c, 晶胞参数a=1.00887(9) nm, b=0.86747(8) nm, c=0.97580(9) nm, V=0.77387(12) nm³, Z=2, 其阴离子层由铝氧三角双锥(AlO₅)和磷氧四面体(PO₄)构成, 层间通过Na⁺离子平衡电荷; 与Uio-14相比, 化合物1具有更高的热稳定性, 在400 ℃空气条件下煅烧后结构仍然保持完好. 对化合物1的质子电导性能测试结果表明, 相比于传统的分子筛类材料, 化合物1展现出优异的质子电导性能, 在55 ℃下质子电导率可达到1.19×10^-3 S/cm.     

Static and Ultrasonic‐assisted Aging Effects on the Synthesis of Analcime Zeolite

The synthesis of zeolite ANA under static hydrothermal conditions was performed accompanied by an additional static and ultrasonic‐assisted aging of the reaction mixture prior to crystallization. The aging process was compared with stirring‐assisted aging, microwave‐assisted aging and syntheses without any aging. The influence of aging time on the crystallization time of zeolite ANA was investigated. The static and ultrasonic‐assisted aging can shorten the crystallization time of the ANA phase. Moreover, ultrasonic‐assisted aging leads to altered morphologies of the particles. The products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM).     

Zeolite Y from kaolin clay of Kachchh,India: Synthesis,characterization and catalytic application

Kaolin clay obtained from Kachchh, Gujarat was used as alumina and silica source to synthesize zeolite Y by hydrothermal method. The synthesis route comprised of the following steps: sulfuric acid treatment at 110 ​°C (4 ​h) for impurity removal followed by calcination at 600 ​°C for 4 ​h, thermal activation of kaolin into metakaolin by NaOH fusion at 850 ​°C (8 ​h); aging of reaction mixtures at 50 ​°C (24 ​h); crystallization (24 ​h) followed by washing and drying. The synthesized zeolite Y was examined by multiple characterization techniques which revealed a pore volume of 0.22 ​cm³/g with pore size of 2.89 ​nm having essential surface area of 320 ​m²/g, indicating a porous material having majority of micropores and remaining mesopores. The zeolite exhibited good catalytic activity for succinic acid esterification using ethanol to produce monoethyl and diethyl succinate. The conversion of SA (72%) and yield (60%) of valuable diester indicated good conversion rate and selectivity at moderate reaction conditions. Detailed structural comparison with zeolite Y synthesized using standard chemical route is also carried out. This work demonstrated an effective way of preparing environmentally benign porous zeolite Y having high surface area and pore volume that can be useful for catalytic applications.     

以季磷化合物为模板剂合成超大孔分子筛ITQ-33

以四丁基氢氧化磷为模板剂, 在中温水热条件下, 利用浓溶胶法合成了具有一维18元环孔道的含铝硅锗酸盐分子筛ITQ-33. 系统研究了ITQ-33的合成条件, 并利用原位变温X射线衍射(XRD), 扫描电子显微镜(SEM), 固体核磁共振波谱(NMR), 电感耦合等离子体发射光谱(ICP), 氮气吸附-脱附程序升温脱附(TPD), 热重(TG)及元素分析等手段对其结构、 稳定性及催化性能进行了表征. 结果表明, 以季磷化合物为模板剂可以合成含铝的ITQ-33纯相, 产物具有较高的热稳定性, 其骨架结构可以稳定至400℃以上, 煅烧后的ITQ-33具有Lewis酸位点, 在酸催化方面有潜在的应用价值.     

Use of mordenite columns in ion-exclusion chromatography

The separation of nitrite ion by ion-exclusion chromatography has been carried out on a laboratory-made mordenite column. The results show that this cheap solid acid can replace, at least in this analysis, the commercial polysulphonated resins and that the separation between these two anions of environmental concern can be carried out very rapidly on such a column.     

Synthesis and crystal structures of two new zigzag versus helical coordination polymers based on diphenic acid

Two new coordination polymers, [Mn(dpa)(2,2′-bipy)] _n (1) and [Ni(dpa)(2,2′-bipy)] _n (2) (H₂dpa = 3,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = bipyridine), have been synthesized and structurally characterized by elemental analysis, IR, and X-ray diffraction. Single-crystal X-ray analyses revealed that 3,4′-diphenic acid acts as a bridging ligand, exhibiting rich coordination modes to link metal ions: μ ₂–η ¹: η ¹, μ ₁–η ¹: η ¹, and μ ₁ –η ¹: η ⁰. Compound 1 demonstrates a 1-D zigzag chain. Compound 2 is a 1-D helical chain. In 1 and 2, there exist intermolecular π–π stacking interactions and non-covalent interactions responsible for the stabilization of the supramolecular structure. In 1, the Mn(II) chains exhibit a weak antiferromagnetic interaction.     

The Role of Hydrothermal Synthesis in Preparative Chemistry

“Hydrothermal synthesis” usually refers to heterogeneous reactions in aqueous media above 100°C and 1 bar. The previously common distinction between hydrothermal conditions below and pneumatolytic conditions above the critical point is no longer made, since no discontinuities are observed upon exceeding the critical conditions. Under hydrothermal conditions, reactants otherwise difficult to dissolve go into solution as complexes, in whose formation water itself or very soluble “mineralizers” can participate. Thus, one can obtain the conditions of chemical transport reactions,^[1] of which hydrothermal syntheses can be considered a special case. During recent decades in the geological sciences—in which the method is also historically rooted—it has received a strong impulse, whose effect on preparative solid state chemistry is discussed here.     

原位合成分子筛膜毛细管色谱柱的研制

吸附型多孔层毛细管柱既耐高温又对气体及烃类异构体有选择性，同时又具有毛细管色谱快速、高效等优点，是解决难分离组分的重要柱型．常用作气一固吸附色谱固定相的有强极性的硅、中极性的氧化铝、非极性的碳质及特殊吸附作用的分子筛．其中分子筛以其独特的吸附作用，在永久性气体和烃类碳数族组成分析中有重要地位．Pruecell和Soulages[1，2]等制备了涂渍型5A和13X型分子筛的毛细管柱，对低碳烃类化合物显示了良好的分离能力，分析柱温较填充柱降低约100℃．邹乃忠等[3～5]也先后制备了分子筛层的毛细管柱用来作直馏汽油的分析．由于通…