Concise design and synthesis of pyridine-fused heterocycles via 6π-Azaelectrocyclization process of iminoalkyne derivatives

A concise and regioselective approach to the synthesis of pyridine-fused heterocycles and benzoxazepine derivatives was developed. Propargyl imines derived from aromatic aldehydes and propargyl amine underwent 6π-electrocyclization reactions at high temperatures in high yields to form pyridine-fused heterocycles. Application of the same methodology to aromatic imines having a hydroxyl group in the ortho position resulted in the formation of (benz)oxazepine derivatives. The formation mechanism of the products was discussed.     

新型氧化铝空心球的制备及表征

以胶体碳球为模板, 廉价的硝酸铝为铝源, 成功制备出了新型的大小可控的氧化铝空心球. 通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、能量扩散X射线(EDX)、X射线粉末衍射(XRD)等手段对合成产品进行了表征, 并考察了不同合成条件对空心球形貌的影响. 实验结果表明, 合成的氧化铝空心球大小均一, 粒径及壁厚均可调节. 在该实验条件下, 硝酸铝浓度及吸附时间的改变对产品结果没有明显的影响, 而吸附温度的改变引起了产品表面光滑度及壁厚的改变.     

Study on the capacity of mesoporous alumina with different pore sizes absorb silane inhibitors

By modifying and optimizing the procedures, which were well described and understood for the synthesis of macroporous alumina, mesoporous alumina–based film has been successfully prepared, In this paper, the orderly mesoporous Al₂O₃ thin film was prepared by electrochemical workstation, and via supported N‐octyltriethoxysilane (NOS) coupling agent, corrosion inhibitors be loaded into the different pore sizes of mesoporous alumina films. The physicochemical properties of this thin inhibitors carrier film were characterized. Corrosion resistance of mesoporous alumina and honeycomb ceramic macroporous alumina were compared; the conclusion shows that mesoporous alumina film can be used as good corrosion inhibitors carrier and bring out a high‐efficiency inhibition result. Simultaneously, by compared with corrosion inhibition of different pore sizes (20‐50 nm) mesoporous alumina who absorbed NOS, and a general relationship between the different mesoporous alumina pore sizes and the adsorption capacity of NOS was obtained.     

多孔管状氧化铝及其负载溴化铝的制备，表征及催化性能

应用棉花为模板,氯化铝为铝源,通过溶胶凝胶法制备了管状γ-氧化铝。通过化学剪裁制备了γ-氧化铝负载的溴化铝催化剂。采用高倍扫描电子显微镜,氮气吸附脱附和X射线衍射分析等技术对其形态,结构以及组成进行表征。实验表明,γ-氧化铝很好地复制棉花的多孔结构,经过化学剪裁,可以得到形态,结构和组分不同的γ-氧化铝负载的溴化铝催化...     

Preparation of stable MCM-48 tubular membranes

Stable mesoporous membranes with a cubic structure, based on the MCM-48 material, were successfully prepared on alumina supports by hydrothermal synthesis, starting from sols having both CTABr and TPAOH structure directing agents. The inclusion of a zeolite (MFI-type) precursor during membrane synthesis led to partial zeolite incorporation into the porous structure, giving rise to a hydrothermally stable membrane. The mean pore diameter of the membrane was 2.5 nm, and permeation experiments confirmed that transport across the membrane was governed by Knudsen diffusion and that there were no pinholes.     

MFI/MFI核壳分子筛合成的影响因素及结晶动力学

以低硅铝比ZSM-5 为核, 采用二次生长法水热合成了MFI/MFI核壳分子筛. 发现对核相分子筛进行预处理是合成的关键步骤. 通过控制壳相合成过程(如合成温度、合成时间和核相分子筛加入量)可有效控制核壳分子筛的壳层生长. 以异丙苯(IPB)及1,3,5-三异丙苯(1,3,5-TIPB)裂解为探针反应, 发现与核相分子筛相比, 核壳分子筛的IPB裂解反应活性相当. 而1,3,5-TIPB裂解活性下降68%, 与外表面Al含量下降程度相近, 表明MFI/MFI核壳分子筛较好地保留了分子筛的核相反应活性. 结晶动力学计算结果表明, MFI/MFI核壳分子筛的成核活化能为51.5 kJ·mol-1, 生长活化能为26.5 kJ·mol-1.     

Synthesis of copper sulphide and copper nanoparticles with microemulsion method

The present work is focused on the synthesis of nanocopper and nanocopper sulphide metallic particles. The precise control of size and shape is best achievable with microemulsion technique, with in situ synthesis in microemulsion. The effect of most crucial operating parameter, water-to-surfactant molar ratio (w), on the product specification including size as well as size distribution and morphology were investigated. The variation of size was observed with variation in w for copper sulphide and copper. Product specifications were analyzed using transmission electron microscope imaging, dynamic light scattering with particle size analyzer and absorption spectra using UV-visible spectrophotometer. It was observed that bigger particles were achieved at higher water-to-surfactant ratio. From systematic study of effect of w on the size and size distribution of copper nanoparticles, the optimum value was chosen for preparation of in situ catalyst. As copper on alumina catalyst has wide catalytic applications of commercial importance, alumina was selected as support. A novel deposition method is developed successfully to deposit the copper nanoparticles from microemulsion on the support. Thus prepared catalyst was analyzed with UV-visible spectrophotometer and found to contain characteristic peak of copper at 655 nm, indicating proper copper deposition on support. XRD analysis of copper on alumina catalyst confirmed presence of metallic copper.     

Grazing incidence x-ray diffraction analysis of zeolite NaA membranes on porous alumina tubes.

Zeolite NaA-type membranes hydrothermally synthesized on porous alumina tubes, for dehydration process, were characterized by grazing incidence 2 theta scan X-ray diffraction analysis (GIXRD). The fine structure of the membrane was studied fractionally for surface layer and for materials embedded in the porous alumina tube. The thickness of the surface layer on the porous alumina tube in the membranes used in this study was approximately 2-3 microm as determined from transmission electron microscopy with focused ion beam thin-layer specimen preparation technique (FIB-TEM). To discuss the effects of the membrane surface morphology on the GIXRD measurements, CaA-type membrane prepared by ion exchange from the NaA-type membrane and surface-damaged NaA-type membrane prepared by water leaching were also studied. For the original NaA-type membrane, 2 theta scan GIXRD patterns could be clearly measured at X-ray incidence angles (alpha) ranging from 0.1 to 2.0 deg in increments of 0.1 deg. The surface layers of the 2 - 3 microm on the porous alumina tube correspond to the alpha values up to ca. 0.2 deg. For the CaA-type and the surface-damaged NaA-type membranes, however, diffraction patterns from the surface layer could not be successfully detected and the others were somewhat broad. For all the three samples, diffraction intensities of both zeolite and alumina increased with depth (X-ray incidence angle, alpha) in the porous alumina tube region. The depth profile analysis of the membranes based on the GIXRD first revealed that amount of zeolite crystal embedded in the porous alumina tube is much larger than that in the surface layer. Thus, the 2 theta scan GIXRD is a useful method to study zeolite crystal growth mechanism around (both inside and outside) the porous alumina support during hydrothermal synthesis and to study water permeation behavior in the dehydration process.     

Synthesis and characterization of sol–gel alumina nanofibers

Abstract Alumina nanofibers of high aspect ratio with surface area of >300 m² g⁻¹ has been prepared successfully in bulk quantities by the sol–gel method. The synthesis parameters including the binary water–alcohol solvent system to aluminium isopropoxide ratio, pH, type of solvent and aging temperature affect the uniformity and formation of nanofibers. It is proposed that alumina nanofibers were formed by the curling of the nanosheets upon condensation after the hydrolysis. The phase evolution of alumina nanofibers from pseudoboehmite to α phase has been shown by XRD and FTIR. ²⁷Al NMR investigations show that the Al atoms are six and four coordinated. The morphology of the alumina nanofibers does not change much as the calcination temperature was increased. In addition, the average pore size increases and the BET surface area decreases as a function of calcination temperature. The thermal behavior of alumina nanofibers was investigated by TGA. Graphical Abstract      

An easy access to diversely fused dioxa-2-aza-tricyclo[n.3.1.0]tetra/pentadecanes under solvent-free condition

Efficient syntheses of phenyl/N-heterocycle fused 6,13-dioxa-2-aza-tricyclo[8.3.1.0^2,8]tetradecanes have been accomplished from 8-hydroxy quinoline derivatives under solvent-free condition, using basic alumina as the solid support. The methodology was successfully extended for the synthesis of corresponding pentadecane derivatives under similar reaction conditions. In terms of its general applicability, product yield, reaction time and effortless separation techniques, the methodology is more valuable compared to the solution phase protocols.     

Efficient synthesis of 1,4-disubstituted triazolyl N-carboxamides via a simple and convenient MCR using basic alumina as solid support

A microwave assisted green protocol for the synthesis of 1,4-disubstituted triazolyl N-carboxamides was explored using basic alumina as solid support. The method allows domino Ullmann-type reaction, Click reaction and formation of ester or amide linkages in a single reaction vessel using Cu(phen)(PPh₃)Br and CMPA as catalyst and basic alumina as solid support in high yield. The protocol did not require addition of any external ligands or base. The method was also found to be equally good for the synthesis of bis triazole adducts.     

Preparation of an A-type zeolite film on the surface of an alumina ceramic filter

An A-type zeolite film was prepared on the outer surface of an alumina ceramic filter by repeated hydrothermal syntheses using the same sample (referred to as repeated batch synthesis). The thickness of the film was found to increase to 35 μm by precipitating the crushed zeolite crystal on the ceramic filter and to 50 μm by precipitating the crushed alumina before repeated batch synthesis. The structure and atomic composition of the zeolite film obtained were found to the same as those of the corresponding original zeolite using several spectrometric methods: X-ray diffraction (XRD), ²⁹Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and electron-probe microanalysis (EPMA). The morphology and thickness of the zeolite film were dependent on the reaction time and temperature, and especially on the types of silica and alumina sources. The preferred silica and alumina sources were Na₂SiO₃ and Al(OH)₃, respectively; these are different from the usual sources for the synthesis of powdery A-type zeolites.     

Tailoring thermal development of gamma alumina sorbents material using combustion synthesis: the effect of amino acids (G,A, N) and equivalence ratio

Using a combustion synthesis, the range of achievable textures is broader than using conventional synthesis methods and can be controlled more successfully. As a tool allowing the achievement and control of desired textures, here we bring about wet chemistry synthesis using aluminium nitrate nonahydrate (ANN) precursor systematically combined with different fuels (amino acids). The amino acids; glycine (G), alanine (A) and asparagine (N) have been specifically selected in order to show the role of gradual increase in their: (1) molar mass, (2) enthalpy of combustion, (3) amine groups content and (4) ratio to ANN. Detailed (micro) structural and thermal characterisations confirm that the nanocrystalline character and thermomechanical stability were not diminished in the course of this synthesis. The conditions leading to development of different morphologies from gels to powders were found to be heavily under the influence of fuel/oxygen ratio, i.e. of the smouldering versus flaming mechanism of the combustion. Higher content of nitrates (predominately from amino-rich amino acids) strongly promoted auto-combustion behaviour. As-derived alumina precursors have been thermally treated at various temperatures (quenched and soaked), to monitor γ- and α-alumina crystallisation, with respect to the development of morphology. Different texture types have been observed, such as porous wormhole, porous and porous expanded flakes. Higher fuel levels promote specific surface increase. This combustion synthesis allows facile tailoring of nanocrystalline γ-alumina with different morphological features, whereas samples having optimal parameters were suitable for catalyst support application on behalf of rapid sorption performance.

     

Textured macro- and mesoporous alumina samples designed in the presence of different surfactant types

This work presents a method that enables the synthesis of porous alumina in the presence of different types of surfactant. The method is based on a sol–gel transition, using surfactants and droplets of a nonpolar phase as templates. The main purpose was to establish a relationship between the templates and the resulting pore structure. The results show that depending on the type of surfactant used (ionic or nonionic), materials presenting variations in the pore family distribution, X-ray powder diffraction patterns and sample morphology were formed. During the synthesis of these alumina samples, the drying step caused loss of the porous structures, so the shrinkage due to different types of surfactants was evaluated.     

具有三维贯通多级孔道结构大孔氧化铝的制备与表征

采用铝溶胶晶种引入、结合相分离的方法制备了具有三维贯通多级孔道结构的大孔氧化铝材料。采用扫描电镜（SEM）、X射线衍射（XRD）、N₂吸附-脱附、压汞、核磁共振波谱（NMR）等测试方法对所得材料进行了表征。结果表明,该氧化铝材料具有200-600 nm的均匀分布且贯通的连续大孔孔道,经550℃焙烧即可得到结晶态γ-氧化铝。大孔氧化铝比表面积达到366 m²/g,具有以5 nm及400 nm为中心的较为集中的介孔-大孔多级孔道分布。焙烧后的样品中,铝具有四、六两种配位状态。制备过程中,聚环氧乙烷（PEO）作为诱导剂引发固-液两相分离,形成具有三维贯通多级孔道结构大孔氧化铝,而凝胶中引入铝溶胶时,AlOOH晶粒与铝交联水合物均相伴生,在凝胶过程诱导铝交联水合物转变为AlOOH,最终使大孔氧化铝在较低的焙烧温度即可转化为γ-氧化铝。     

预吸附微波合成纳米NaY沸石晶种制备NaY型分子筛膜

在常压回流的微波加热体系中成功地合成出纳米尺寸的NaY分子筛,XRD和SEM等表征结果表明,分子筛具有40nm左右的平均晶粒尺寸.以其为晶种,预吸附在多孔氧化铝载体上,结合原位水热法进行二次晶化,制备出较为致密的NaY分子筛膜,该膜主要以孪生聚晶的形式存在.CO₂/N₂气体分离测试结果显示,随着温度的升高,分子筛膜的气体分离能力呈上升趋势,在140℃时真实选择分离系数达到最大值4.0.     

Synthesis of large-pore micelle-templated silico-aluminas at different alumina contents

The EPR spectra of radical surfactant probes embedded in cetyltrimethylammonium bromide (CTAB) and trimethylbenzene (TMB) stable water emulsions (TMB/CTAB = 13) were analyzed to provide information on the kinetics of formation of micelle-templated silicoaluminas (MTSA) at 343 K, obtained by means of silica and alumina, solved in alkaline solutions, at different Si/Al ratios. Textural (surface area, pore volume, pore size, surfactant content) and structural characterization of both as-synthesized and calcined MTSA were performed by means of nitrogen sorption isotherms, TEM, and chemical analysis. This analysis showed that TMB worked as a swelling agent of the CTAB micelles, providing large-pore homogeneous and stable MTSA at TMB/CTAB = 13 for Si/Al from infinity to 10. A demixing of the emulsion occurs at Si/Al < 10: at Si/Al = 7, a double wide-and-narrow pore structure was formed; then, at Si/Al = 5, an amorphous material was obtained. At Si/Al > or = 10, the computer-aided analysis of the EPR spectra as a function of the synthesis time indicated the distribution of the probes in two different environments: "micellar" probes inserted in the surfactant aggregates, whose mobility decreases over the synthesis time, thus reporting on the progressive modification of the surfactant aggregates structure and the solid condensation, and "interacting" probes due to probe-surfactant heads electrostatically interacting with the charged surface sites induced by alumina incorporation in the silica network. This last fraction increases its relative amount over the synthesis time, informing about the condensation and structuration of the MTSA. Without alumina, the "interacting" component is absent in the EPR spectra because TMB preferentially interacts with the surfactant headgroups by cation-pi interactions, thus preventing the interactions of these headgroups with silanols. When alumina is added, the negatively charged silicoaluminate at the surface promotes the interaction of the ammonium headgroups with the surface, and some Na+ cations also interact with TMB by cation-pi interaction and contribute to decreasing the interaction of the headgroups with TMB. Therefore, increasing alumina contents promote electrostatic interactions between the positively charged surfactant heads and the negatively charged silicoaluminate groups. The strong interaction of the surfactants with the silicoaluminate surface allows the formation of a monolayerlike structure of surfactant, which is not observed in the absence of alumina. The synthesis is slowed by increasing alumina contents due to a destructuration effect of alumina in the MTSA formation.     

化学修饰氧化铝负载钴基催化剂吸附与反应行为的研究

提出了一种改进催化剂活性和C₅⁺烃选择性的方法,利用原位红外光谱、TPSR和费-托合成反应考察了催化剂的还原、分散、吸附与反应行为的关系.研究表明,载体处理的差异决定了CO在催化剂表面上的吸附形态,钴负载在氨修饰氧化铝上有利于桥式CO吸附,而醋酸改性氧化铝则增进了金属钴与载体之间的相互作用,催化剂以线形吸收态为主.CO加氢反应表明,氨修饰氧化铝负载钴催化剂能促进活性和C+5烃选择性的提高,而醋酸修饰氧化铝可抑止钴催化剂的活性和碳链增长.     

Microporous Crystalline γ‐Al2O3 Replicated from Microporous Covalent Triazine Framework and Its Application as Support for Catalytic Hydrolysis of Ammonia Borane

Significant progress has been made on the synthesis and application of mesoporous γ‐alumina. To date, little attention has been paid to the synthesis of microporous crystalline alumina. Here, fabrication of microporous crystalline γ‐alumina using a microporous covalent triazine framework (CTF‐1) as a template is described. Microporous crystalline γ‐alumina with a micro‐meso binary pore system was replicated by infiltration of aluminum nitrate into the micropores of the CTF‐1 template through a NH₃/water‐vapor‐induced internal hydrolysis method, followed by thermal treatment, and subsequent removal of the CTF‐1 template with a 30 % H₂O₂ aqueous solution. The obtained crystalline γ‐alumina material exhibits a large surface area (349 m² g⁻¹) with micropore distribution centered at about 1.27 nm. Ru supported on microporous γ‐Al₂O₃ can be employed as catalyst for hydrolytic dehydrogenation of ammonia borane, and it exhibits high catalytic activity and good durability. This finding provides a new benchmark for preparing well‐defined crystalline microporous alumina materials by a template method, which can be applied in a wide range of fields.     

Effect of a novel green modification of alumina nanoparticles on the curing kinetics and electrical insulation properties of epoxy composites

A novel green surface modification was successfully implemented on alumina nanoparticles using chitosan (CS) to prevent nanoparticles' aggregation. To evaluate the surface changes of nanoparticles, FTIR, TGA, TEM, and SEM analyses were used. The cure kinetics of the uncured samples was analyzed by DSC. Different methods such as KAS, Friedman, Starink, and FWO were applied to measure the activation energy. The activation energy of epoxy reinforced with chitosan-functionalized alumina (epoxy/[CS-EPO-alumina]) was less than that of epoxy reinforced with alumina (epoxy/alumina), which was a confirmation of the positive effect of CS on curing reaction kinetics. Using the Malek method, the Sestak-Berggren autocatalytic equation was chosen to investigate the cure kinetics of the epoxy. It was found that the Sestak-Berggren equation is well matched with the experimental data and the model was suitable to predict the epoxy curing reaction reliably. Moreover, the glass transition temperatures of all samples were approximately the same. The effect of surface modification of alumina on the electrical insulating behavior of epoxy was also studied. It was found that CS functionalized alumina (CS-EPO-alumina) increased volume resistivity of epoxy at a temperature range of 30 to 80°C more than that of alumina. Electric stability and breakdown strength of epoxy/alumina and epoxy/(CS-EPO-alumina) also enhanced, where epoxy/(CS-EPO-alumina) experienced a further increase compared to epoxy.