One-step synthesis of hierarchical aluminosilicate aggregates using bifunctional alkanolamine as single template

Highly active, hierarchical zeolite ZSM-5 aggregates have been prepared in a one-step synthesis using alkanolamine as single template. The effects of SiO₂/Al₂O₃, pH and H₂O/SiO₂ on the aggregate morphology of the ZSM-5 nanocrystals were investigated. The obtained aggregate zeolites characterized by SEM, TEM and BET possessed significant textual porosity (up to 0.22 cm³/g), which could be tuned by the number of substituents in the alkanolamine molecules and the amount of aluminum in the synthetic mixtures. These zeolite aggregates showed high activities for Friedel–Crafts alkylations and may curtail the filtration difficulties during the synthesis and applications to some extent.     

Template method for the synthesis of a heterogeneous fenton catalyst based on the hierarchical zeolite FeZSM-5

Zeolite h-FeZSM-5 with a hierarchical micro/macropore system has been synthesized in the presence of a template based on the close-packed polystyrene (PS) spheres, and the conventional zeolite FeZSM-5 has been obtained in the absence of a PS template. The zeolites have been characterized by X-ray diffraction, scanning and high-resolution transmission electron microscopy, and N₂ sorption. The macropore walls of the hierarchical zeolite consist of ZSM-5 nanocrystals and amorphous globules of silica. Compared to the conventional zeolite, the hierarchical one has a high BET and external surface areas of 245 and 472 m²/g, respectively, and a high pore volume of 0.6 cm³/g. The catalytic properties of the Fe-containing zeolites were studied in the H₂O₂ decomposition reaction in the absence and in the presence of EDTA ligands and in the oxidation of low- and high-molecular-weight organic compounds by hydrogen peroxide at 25°C. Hierarchical zeolite h-FeZSM-5 is highly efficient in the oxidation of large molecules.     

Gemini quaternary ammonium salt cationic surfactant‐assisted hydrothermal synthesis: An effective way to tune the textural properties of zeolite and the acidity of Beta molecular sieves

Novel hierarchical Beta zeolites have been successfully synthesized via a one‐pot dual‐templates strategy utilizing gemini organic surfactant and tetraethylammonium hydroxide (TEAOH)through hydrothermal process. The influence of several parameters on the formation of hierarchical Beta zeolite, the change in acidity and a possible growth scheme were systematically investigated. The physicochemical properties of these catalysts were characterized by PXRD, BET, SEM, HRTEM SAED, TG and NH₃‐TPD techniques, and the performance as acid catalysts was verified using the transformation of EtOH as a model reaction. On one hand, WAXRD data indicated that decreasing the temperature of synthesis and increasing amounts of C_12‐6‐12 in the process of synthesis resulted in lower crystallinity of Beta zeolites due to the BEA nuclei formation and crystal growth constrained by C_12‐6‐12. On the other hand, SAXRD and HRTEM data evidenced that C_12‐6‐12 initially generated a pseudo‐ordered mesoporous phase which was then partially occupied by the zeolite. After a period of ~96 h for crystallization, the hierarchy zeolite possessing 765.7 m²·g^‐1 of Brunauer‐Emmett‐Tellerarea, and average mesopore size distribution of 3.51 nm can be synthesized, and its microporous structure has a good crystallinity and lower amounts of acid sites than that of the microporous Beta one. Furthermore, the as‐obtained hierarchical zeolite displayed lower deactivation rate mainly due to the less coke formation on the surface of catalyst. It is expected to develop more considerable potential application value for the hierarchical Beta zeolite structure in the near future.     

Preparation and characterization of aqueous stable electro-spun nanofibers using polyvinyl alcohol/polyvinyl pyrrolidone/zeolite

Cross-linked polyvinyl alcohol/polyvinyl pyrrolidone/zeolite fibers were prepared in the presence of potassium peroxodisulphate (K₂S₂O₈) under the curing process by the electrospinning technique. The narrowest nanofibers of PVA/PVP (50:50) were prepared under optimum experimental conditions of 2.5 × 10^?4 mol of K₂S₂O₈, an applied voltage of 22 KV, the distance of 15 cm and the feed rate of 0.2 mL/h. The progress of the cross-linking was examined by immersion of the prepared nanofibers in water and following the swelling degrees. By raising the K₂S₂O₈ amount and curing time, the cross-linking density was increased. X-ray diffraction (XRD) demonstrated that the crystallinity of the nanofibers was decreased by the increase of K₂S₂O₈ and the lowest crystallinity was observed for PVA/PVP (70:30). The contact angle of nanofibers was decreased from 72° to 34 by increasing PVP ratio from 30 to 70. The morphology of the nanofibers before and after immersion in the simulated body fluid (SBF) was studied using electron scanning microscopy (SEM) and PVA/PVP (70:30) showed the highest changes in the morphology while the lowest one was observed for PVA/PVP (50:50). Moreover, the cross-linked PVA/ PVP with the ratio of 50:50 had the narrowest diameter of 200 ± 100 nm, and by addition of about 0.5% zeolite, it was even reduced more to 150 ± 50 nm. The cross-linked nanofibers (50:50) with 0.5 wt% and 1.5 wt% zeolite nanoparticles showed the tensile modules of 416.26 and 703.52 MPa, respectively, while in the absence of zeolite, it was209.25 MPa. Fibroblast L929 cells were cultured on the cross-linked PVA/PVP/zeolite (50:50:0.5) nanofiber, and the cell proliferation and growth was evaluated by MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. Fibroblasts grew on the surface of scaffold showed good morphology and proliferation after seven days and the absorption amount was increased from 0.075 to 0.78     

One-pot non-template synthesis of hierarchical ZSM-5 from kaolin source

Hierarchical ZSM-5 was synthesized without organic template and seed-assisted from the abundant natural source, kaolin, via the facile 1-step hydrothermal process. The hierarchical structure was able to be well-controlled solely on the Na₂O/Al₂O₃ ratio of the precursor. This method is not only simple but greener from the scientific point of view. As revealed, kaolin layered structure that dispersed in the highly alkaline NaOH medium prompts the formation of zeolite as the molecular organization is induced. The excess of NaOH acts as desilication agent after the formation of zeolite as proven by the ²⁹Si MAS NMR data.     

EU-1分子筛的合成及其在正己烷异构化反应中的催化性能

在不同硅铝比(n_SiO2/n_Al2O3)的合成凝胶(含纯硅凝胶)中引入晶种,合成了纯相的EU-1分子筛。研究了铝源、模板剂和晶种添加量对EU-1分子筛的结晶度、形貌尺寸等的影响;重点研究了不同硅铝比对样品结晶度、晶粒尺寸、酸性、比表面积和孔容等的影响。将合成结果绘制成了纯相EU-1分子筛的合成条件三元图,从三元图可看出,晶种法可显著扩大纯相EU-1分子筛的合成区域。将Pt/H-EU-1用于正己烷异构化反应,结果表明,该催化剂具有优异的正己烷异构化活性及稳定性,对异构烷烃有较高的选择性。     

晶种导向干凝胶法制备成型ZSM-5分子筛

在干凝胶法制备ZSM-5 分子筛的体系中添加晶种导向剂, 控制分子筛的生长, 制备了纳米沸石组装的无粘结剂成型多级孔ZSM-5 分子筛, 一步完成纳米分子筛的制备及组装成型, 即克服了传统纳米粒子难以过滤分离的问题, 同时组装所形成的多级孔有助于改善分子在催化剂内的扩散, 从而提高催化反应效率. 以硅胶、薄水铝石为原料, 四丙基氢氧化铵(TPAOH)和ZSM-5 晶种导向胶作为粘结剂, 通过混捏、挤条得到直径2 mm的条状前驱物, 随后通过干凝胶转换法制备成型分子筛. 所用晶种导向剂组成为0.35TPAOH:1SiO₂:20H₂O:4C₂H₅OH. 通过X射线衍射(XRD), 热重(TG)分析和傅里叶变换红外(FTIR)光谱等方法对分子筛晶化过程进行了表征, 结果表明晶种导向剂加入量对分子筛生长速度及多级孔结构均有影响. 当所加晶种导向剂中TPAOH与SiO₂的摩尔比为0.025时, 经过3 h晶化, 分子筛相对结晶度达到100%. 扫描电镜(SEM)结果表明, 合成的分子筛尺寸约为200 nm, 组装形成的多级孔分子筛的介孔体积为0.28 cm³·g^-1. 通过NH₃ 程序升温脱附(NH₃-TPD)考察了所得成型分子筛的酸性, 发现该分子筛酸性与市售的粉末H-ZSM-5分子筛类似.     

EU-1分子筛的合成及其在正己烷异构化反应中的催化性能

在不同硅铝比(nSiO₂/nAl₂O₃)的合成凝胶(含纯硅凝胶)中引入晶种,合成了纯相的EU-1分子筛。研究了铝源、模板剂和晶种添加量对EU-1分子筛的结晶度、形貌尺寸等的影响;重点研究了不同硅铝比对样品结晶度、晶粒尺寸、酸性、比表面积和孔容等的影响。将合成结果绘制成了纯相EU-1分子筛的合成条件三元图,从三元图可看出,晶种法可显著扩大纯相EU-1分子筛的合成区域。将Pt/H-EU-1用于正己烷异构化反应,结果表明,该催化剂具有优异的正己烷异构化活性及稳定性,对异构烷烃有较高的选择性。     

Spectroscopic and Discharge Studies on Graphene Oxide Doped PVA/PVP Blend Nanocomposite Polymer Films

Graphene oxide (GO) nanoparticles were synthesized by modified Hummers method. The synthesized GO nanoparticles were incorporated in polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend polymers for the preparation of nanocomposite polymer films by solution cast technique. Different characterizations such as XRD, UV–Vis and FTIR were carried-out on to the prepared nanocomposite polymer films. The thermal analysis of the films was studied by DSC. The morphology of PVA/PVP:GO polymer films confirms GO was exfoliated within the PVA/PVP matrix and also reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. From the conductivity studies the highest conductivity of PVA/PVP: GO (0.45: 0.3) was found to be 8.05 × 10^–4 S/cm at room temperature. Solid state battery has been fabricated with the configuration of Mg⁺/(PVA/PVP:GO)/(I₂ + C + electrolyte) and its cell parameters were calculated for a constant load of 100 kΩ.     

The success of dual‐functional templating for synthesizing hierarchical analcime zeolite

Novel and innovative hierarchical analcime zeolites were prepared by adding a gemini surfactant which acted as a dual‐functional template. Through a one‐step hydrothermal process, a hierarchical analcime zeolite with abundant intracrystalline mesopores was synthesized. Powder X‐ray diffraction and N₂ adsorption–desorption data show that the mesoporous composites possess both a quite a number of mesopores and analcime structure. The results suggest that the dual‐functional template can be effective in the synthesis of hierarchical analcime zeolites.     

Facile synthesis of Li3V2(Po4)3/C nano-flakes with high-rate performance as cathode material for Li-ion battery

The flake-like Li₃V₂(PO₄)₃/C has been successfully synthesized by rheological phase method using polyvinyl alcohol (PVA) as template; the Li₃V₂(PO₄)₃/C without PVA assistance has been prepared for comparison. X-ray diffraction analysis shows that the two samples are well crystallized, and no impurity phases are detected. The scanning electron microscopy results reveal that there is a significant difference in morphologies between PVA-assisted sample and sample without PVA; the former shows a flake-like morphology, while the latter presents regular granular shape with some agglomeration. Transmission electron microscopy images reveal that Li₃V₂(PO₄)₃ particles are coated with a uniform surface carbon layer. The lattice fringes with a spacing of 0.428 nm can be clearly seen from the high-resolution transmission electron microscopy image. The PVA-assisted sample shows a discharge capacity of 120, 110, and 96 mAh g^?1 at 1 C, 20 C, and 50 C, respectively; however, the sample without PVA exhibits a lower discharge capacity. Based on the analysis of electrochemical impedance spectroscopy, the lithium ion diffusion coefficients of Li₃V₂(PO₄)₃/C and PVA-assisted Li₃V₂(PO₄)₃/C are 4.19?×?10^?9 and 4.99?×?10^?8 cm² s^?1, respectively. In summary, it is demonstrated that using PVA as a template can obtain flake-like morphology and significantly improve the comprehensive electrochemical performances of Li₃V₂(PO₄)₃/C cathode material.     

The synthesis of mesoporous zeolite beta aggregates without the use of second template and additive

Zeolite Beta Aggregates have been synthesized by the self-assembly of Beta nanoparticles without the use of second template or additive, where the large zeolitic aggregates avoided the filtration difficulties and the presence of mesopore reduced the diffusion limitation. The samples were characterized by XRD, N₂-sorption, SEM, TEM, thermogravimetric analysis, IR spectroscopy and temperature programmed desorption of ammonia. The results showed that the SiO₂/Al₂O₃ ratio played a key role on the particle size, mesopore volume and particle–particle aggregation process of zeolite Beta. The sample with SiO₂/Al₂O₃ ratio below 60 had improved textual and acidic properties and exhibited the best catalytic activity to the alkylation of phenol with tert-butanol.     

Fluorine‐Doped Porous Single‐Crystal Rutile TiO2 Nanorods for Enhancing Photoelectrochemical Water Splitting

Fluorine‐doped hierarchical porous single‐crystal rutile TiO₂ nanorods have been synthesized through a silica template method, in which F^? ions acts as both n‐type dopants and capping agents to make the isotropic growth of the nanorods. The combination of high crystallinity, abundant surface reactive sites, large porosity, and improved electronic conductivity leads to an excellent photoelectrochemical activity. The photoanode made of F‐doped porous single crystals displays a remarkably enhanced solar‐to‐hydrogen conversion efficiency (≈0.35 % at ?0.33 V vs. Ag/AgCl) under 100 mW cm^?2 of AM=1.5 solar simulator illumination that is ten times of the pristine solid TiO₂ single crystals.     

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al₂O₃) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al₂O₃ nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al₂O₃ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al₂O₃ nanosheets possess high surface areas up to 425 and 371 m² g⁻¹, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al₂O₃ multilayered nanosheets exhibit Mo adsorption capacities of 33.1–40.8 mg g⁻¹. The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.     

催化剂量甘油对THF-FER沸石结晶过程的加速作用

The hydrothermal crystallization of THF-FER zeolite was investigated in the reactant system of Na2O-SiO2-Al2O3-H2O with tetrahydrofuran （THF） as the template in the presence of various catalytic amount of glycerol [CH2（OH）CH（OH）CH2（OH）, Glyc] in the temperature range of 413--473 K. Powder X-ray diffraction （XRD） was used to observe the crystallization process, and scanning electron microscope （SEM）, ^13C cross polarization （CP） and ^27Al magic angle spinning nuclear magnetic resonance （MAS NMR）, X-ray fluorescence scattering spectroscopy （XRF）, thermal analysis and nitrogen sorption were used to characterize the zeolite synthesized in the reactant system with Glyc. The catalytic amount of Glyc could promote the crystallization of FER zeolite, to result in lowering the reaction temperature, shortening the period of the zeolite crystallization and effectively restraining cocrystallization of MOR zeolite as an impure phase especially at low reaction temperature, and possess a significant effect on the morphology and the crystal size of TI-IF-FER zeolite.     

晶种协同廉价有机模板导向合成高纯度MCM-49沸石

采用廉价低毒性的环己胺（CHA）作为有机模板剂,并合理添加少量MCM-49沸石晶种,在静态水热条件下成功合成了高纯度MCM-49沸石.研究了起始凝胶组成（如Al₂O₃/SiO₂,H₂O/SiO₂,CHA/SiO₂,晶种/SiO₂,Na₂O/SiO₂）、晶化温度和时间等因素对合成MCM-49沸石的影响.通过XRD、SEM、N₂吸附、固体²⁷Al和²⁹Si MAS NMR等手段表征产物,结果表明合成的MCM-49沸石具有良好的结晶度、均匀的晶体尺寸、高比表面积和纯的四配位Al³⁺物种.热重差热分析（TG-DTA）和固体¹³C MAS NMR表征结果证实CHA是作为模板剂填充在沸石产物的孔道内.这种合成MCM-49的方法具有廉价和低毒性的特点,对其产业应用有潜在的重要价值.     

微米级MEL分子筛聚集体的制备

使用四丁基氢氧化铵-正硅酸四乙酯-水（TBAOH-TEOS-H₂O）简单体系一步水热制备了具有多级孔道的微米级MEL结构分子筛聚集体. 得到的silicalite-2 微米球直径大于10 μm且具有高达460 m²·g^-1的比表面积和0.74 cm³·g^-1的孔体积. 微米球的生成一定程度上解决了催化应用过程中催化剂的分离和回收问题. 同时,水热晶化过程中由纳米粒子自组装而成的晶间介孔缩短了反应物分子的扩散路径,保持了分子筛纳米晶粒的优势. 此外,钛活性位的引入并未明显影响MEL微米球的形貌和结构,含钛的MEL微米球TS（钛硅分子筛）-2在苯酚羟基化反应中具有与纳米尺寸TS-1（100-200 nm）相当的催化活性,且TS-2 可以通过简单过滤得到,简化了纳米级TS-1的分离和回收过程.     

含氟体系中高性能T型分子筛膜的合成

含氟体系中,在负载晶种的大孔莫来石支撑体表面快速合成了高性能且取向生长的T型分子筛膜。采用XRD、SEM和MAS NMR等手段对分子筛膜层和粉末进行表征。讨论了添加物、氟硅比、合成温度和合成时间等条件对膜生长与分离性能的影响,并阐述了含氟体系中T型分子筛膜快速晶化的机理。碱金属氟盐的加入促进了T型分子筛晶体层的晶化速率,并对晶体层形貌产生了一定的影响。膜应用于75℃、水/异丙醇(10∶90,w/w)体系的平均渗透通量和分离因子分别为(4.91±0.18)kg·m-2·h-1和7 060±1 130。     

异相晶种诱导快速合成低硅菱沸石分子筛

在不含有机模板剂体系(OSDAs)中,利用异相晶种(T型分子筛)诱导快速合成出纯相的低硅菱沸石分子筛。采用XRD、SEM、TEM、27Al MAS NMR和紫外拉曼等手段表征分子筛的结构属性和形貌特点。详细研究了菱沸石分子筛的晶化过程以及晶种添加量、nAl2O3/nSi O2、nH2O/nSiO2和碱度对菱沸石分子筛晶化的影响,并探讨T型分子筛晶种诱导合成菱沸石分子筛的晶化机理。原位合成体系中仅形成L型分子筛晶相,而一定量T型分子筛异相晶种的加入诱导溶胶快速制备出纯相的菱沸石分子筛。T型分子筛晶体在一定的水热条件下不断溶解而释放的六元环(6R)和四元环(4R)迅速形成菱沸石分子筛特征笼(CHA笼),抑制了L型分子筛特征单元和特征笼(不含四元环的CAN笼)的形成。     

Direct Synthesis of Nanosheet-Stacked Hierarchical “Honey Stick-like” MFI Zeolites by an Aromatic Heterocyclic Dual-Functional Organic Structure-Directing Agent

Soft template designing is the most promising strategy for the synthesis of zeolite nanosheets. MFI nanosheets directed by soft templates (containing long-chain alkyl groups or aromatic groups as hydrophobic component) can be found frequently; however, so far, MFI nanosheets synthesized by soft templates with aromatic heterocycle groups (e. g., s-triazine groups) are rare. Herein, a nanosheet-stacked hierarchical MFI zeolite (NSHM) has been synthesized by using a triply branched s-triazine-based surfactant as a bifunctional organic structure-directing agent. On the basis of a geometrical match relationship, a formation model has been proposed. Synthesized NSHM had abundant mesopores stacked by nanosheets and exhibited a high surface area (430 m² ⋅ g⁻¹). The 1 wt% Pd/NSHM attained a significant increase in yield of cyclohexanol/cyclohexanone mixture (from 66 to 85 %) in the oxidation of cyclohexane compared with Silicalite-1 and SBA-15 as supports.