Enhancement of NaA zeolite membrane properties through organic cation addition

Thin NaA zeolite membranes, with uniform and small crystals, were prepared on the tubular -Al₂O₃ support by adding a small amount of tetramethylammonium hydroxide (TMAOH) in the clear synthesis solution. The as-synthesized NaA zeolite membranes were characterized by XRD and SEM. The permeation properties of the membranes were evaluated by pervaporation and gas permeation. The effects of TMAOH amount on membrane formation and permeation properties were investigated. By addition of suitable amount of TMAOH in the clear synthesis solution, the crystals size of NaA zeolite could be remarkably reduced from about 10 μm to 3–4 μm, and the membrane thickness correspondingly reduced from about 16 μm to 5 μm. The thinner membrane prepared by adding TMAOH in the clear synthesis solution, with uniform and small crystal, displayed higher perm-selective properties than that without adding TMAOH. For the as-synthesized NaA zeolite membrane prepared with adding suitable amount of TMAOH (x = 1), the separation factor (water/isopropanol) was 4700 and the flux was 1.67 kg/(m² h), which were higher than that without adding TMAOH of 339 and 1.08 kg/(m² h), respectively. The ideal separation factor of H₂/N₂ was 6.60, higher than that without adding TMAOH of 3.41.     

Environment-friendly synthesis of nitrogen-containing heterocyclic compounds

A novel environment-friendly vapour phase synthesis of different classes of nitrogen-containing heterocyclic compounds was developed using non-hazardous, commercially available and low cost feeds. 2-Methyl-8-ethylquinoline (MEQUI) was obtained from 2-ethylaniline (2-ETAN) and ethylene glycol (EG) or chloroethanol (CE), operating at high temperature in the presence of acid-treated K10 montmorillonite or ZnCl₂/K10 montmorillonite. At lower temperatures and using copper chromite catalysts, 7-ethylindole (7-ETI) or 5-ethylindole (5-ETI) were obtained from 2-ETAN or 4-ethylaniline (4-ETAN), respectively, and EG; excess of alkylaniline was required to avoid the formation of polyalkylated by-products. Mixing SiO₂ with the best copper chromite, made it possible to operate with higher LHSV values, thus improving the yield in alkylindoles. Finally, N-(2-ethylphenyl)pyrrole (EPP) and N-(2-ethylphenyl)pyrrolidine (EPD) were synthesised using a commercial copper chromite catalyst and feeding 2-ETAN and 2,3-dihydrofuran (DHF), EPP being favoured by high temperatures and absence of water in the feed. The possible reaction pathway for each synthesis is proposed, to evidence the key features of the best catalysts identified.     

Photoluminescence study of annealed nickel- and nitrogen-containing synthetic diamond

The results of a photoluminescence (PL) study of synthetic diamonds showing different degrees of nickel–nitrogen complex transformation are presented. A number of new, previously undocumented PL systems with zero-phonon lines (ZPLs) at 2.071, 1.991, 1.940, 1.648 and 1.413 eV have been found. Most of the PL systems observed are transient, only the S2, S3, 1.563 and 1.648 eV systems are present in the PL spectra of crystals annealed at 2200°C and 2500°C. The photoluminescence excitation (PLE) spectra for the 2.071, 1.991, 1.704, 1.660, 1.563 and 1.648 eV systems have been measured. It has been established that vibronic bands with ZPLs at 2.427 and 1.991 eV seen in the absorption spectra of annealed diamonds are related to the 1.660 and 1.991 eV PL systems, respectively. It has been revealed that the well-known 1.4 eV system is present in the PL spectra of diamonds annealed at temperatures of 2200°C and higher.     

Enhancement of the electrophotographic properties of DLC coated OPC drums by oxygen addition

Diamond-like carbon films with high transmittance over 90% and hardness substantially higher than that of a organic photoconductor (OPC) were deposited on OPC layers using a d.c.-remote plasma enhancement chemical vapor deposition (RPECVD) system with a magnetic field imposed around the cathode. All the electrophotographic properties except residual potential were enhanced by DLC coating. The hardness and resistivity of the DLC film were also improved by adding oxygen to CH₄ gas. However, the residual potential value can be reduced to 11.0 V which is acceptable even for high sensitivity laser printing, by using a CH₄–20at.% O₂ gas mixture in the RPECVD for DLC coating.     

硫黄用量对TPI和IR胶料性能的影响对比

研究硫黄用量对反式1,4-聚异戊二烯(TPI)和IR胶料性能的影响.试验结果表明,与IR相比,在硫黄用量相同的条件下,TPI胶料的MH较大,焦烧时间较短,炭黑分散性稍差,硫化胶的硬度和定伸应力较大,拉伸强度和拉断伸长率较小,耐磨性能较高;硫黄用量对TPI硫化胶耐疲劳性能的影响较大.     

CdTe量子点荧光猝灭法测定四环素

以巯基乙酸为稳定剂水热法制备Cd Te量子点,考察不同条件下四环素对Cd Te量子点的荧光猝灭作用,建立一种荧光测定四环素含量的新方法。该方法的线性范围为1.0²0.0μg/m L,工作曲线为ΔF=2.308 2+9.679 3c(μg/m L),相关系数r为0.999 5,检出限(3SD/斜率)为0.025μg/m L。该方法应用于实际样品中四环素含量的测定,相对标准偏差<2.3%,回收率在97.5%20.0μg/m L,工作曲线为ΔF=2.308 2+9.679 3c(μg/m L),相关系数r为0.999 5,检出限(3SD/斜率)为0.025μg/m L。该方法应用于实际样品中四环素含量的测定,相对标准偏差<2.3%,回收率在97.5%¹03.3%。     

含氮化合物在甲苯氧化中的应用进展

介绍了卟啉配合物、酞菁配合物、N-羟基邻苯二甲酰亚胺(NHPI)等含氮化合物在甲苯催化氧化中的研究应用现状。从反应条件、催化活性、使用性能等方面归纳分析了各类含氮化合物在甲苯氧化催化体系中的优缺点。指出今后可以从开发高效可循环的NHPI复合催化体系和探索粗甲苯氧化催化体系两方面深入开展含氮化合物催化氧化甲苯的研究。     

Enhancement of mechanical and thermal properties of polycaprolactone/chitosan blend by calcium carbonate nanoparticles

This study investigates the effects of calcium carbonate (CaCO(3)) nanoparticles on the mechanical and thermal properties and surface morphology of polycaprolactone (PCL)/chitosan nanocomposites. The nanocomposites of PCL/chitosan/CaCO(3) were prepared using a melt blending technique. Transmission electron microscopy (TEM) results indicate the average size of nanoparticles to be approximately 62 nm. Tensile measurement results show an increase in the tensile modulus with CaCO(3) nanoparticle loading. Tensile strength and elongation at break show gradual improvement with the addition of up to 1 wt% of nano-sized CaCO(3). Decreasing performance of these properties is observed for loading of more than 1 wt% of nano-sized CaCO(3). The thermal stability was best enhanced at 1 wt% of CaCO(3) nanoparticle loading. The fractured surface morphology of the PCL/chitosan blend becomes more stretched and homogeneous in PCL/chitosan/CaCO(3) nanocomposite. TEM micrograph displays good dispersion of CaCO(3) at lower nanoparticle loading within the matrix.     

Improvement of the mechanical properties of chitosan films by the addition of poly(ethylene oxide)

The mechanical properties of films prepared from mixed acetic acid aqueous solutions of chitosan (M_w = 400,000; M_w/M_n = 3.8) and poly(ethylene oxide) (PEO) (viscosity average molecular weight of 200,000 or 600,000) were determined. A chitosan:PEO weight ratio of 10:2 improved the mechanical properties compared with pure chitosan films. The improvement of the mechanical properties correlated with a small reduction of the correlation length measured by small‐angle neutron scattering (SANS).     

Enhancement of physical properties of electroactive polyimide nanocomposites by addition of graphene nanosheets

Electroactive polyimide (EPI) nanocomposites with amino‐capped aniline trimer and 4′‐(4,4′‐isopropylidene‐diphenoxy)bis(phthalic anhydride) as monomers, and functionalized with carboxyl‐graphene nanosheets, were prepared by thermal imidization. The as‐prepared electroactive polyimide/graphene nanocomposite (EPGN) materials were then characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. In situ monitoring of the redox behavior of the as‐prepared EPGN materials was performed by cyclic voltammetry studies. The effects of material composition on the mechanical, thermal, thermal transport, dielectric and molecular barrier properties of EPGN membranes were investigated by dynamic mechanical analysis, TGA, DSC, the transient plane source technique, LCR meter and gas permeability analyzer, respectively. It should be noted that all the properties of the EPGN membranes were found to improve substantially over those of non‐electroactive polyimide and EPI. For example, upon loading of 1 wt% graphene, EPGN membranes were found to have an increase of over 20%, 5%, 65% and 20% in mechanical strength, thermal stability, thermal conductivity and dielectric constant, respectively, and a reduction of over 20% in gas permeability. © 2013 Society of Chemical Industry     

Transformation of nitrogen-containing compounds in atmospheric residue by hydrotreating

Atmospheric residue from Saudi Arabia light crude oil was subjected to the hydrotreating process in a continuous fixed-bed reactor with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) catalysts. The detailed molecular composition of the polar heteroatom species in the feedstock and products was determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with other analytical methods. The ESI FT-ICR MS analysis indicates that the N₁ class species have the highest relative abundance. In the hydrotreating process, small neutral N₁ class species with high aromaticity and short side chains showed the highest relative abundance and were defined as easily removable compounds. High aromaticity and small molecule basic N1 compounds exhibited higher catalytic activity towards hydrogenation. The N₁S₁ class species were converted to the N₁ class species, or even hydrocarbons, by the preferential removal of the sulfur atoms. Most of the N₁O₁ class species were difficult to remove, because of their stable chemical structure.     

Effect of the structure of nitrogen-containing compounds on their defoaming and demulsifying abilities

A study is undertaken to explore the effect of the structure of nitrogen-containing organic compounds-inhibitors of hydrogen sulfide corrosion in the gas industry-on their defoaming and demulsifying abilities. It is concluded that, in the totality of its properties, the requirements of the gas industry are best met by tertiary aliphatic diamine of the C_{12, 14} fraction.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 1, 2005, pp. 83–87.Original Russian Text Copyright © 2005 by Muraveva, Melnikov.     

Solid catalysts for wet oxidation of nitrogen-containing organic compounds

Several solid catalysts (Co₃O₄/γ-Al₂O₃, Fe₂O₃/γ-Al₂O₃, Mn₂O₃/γ-Al₂O₃, Zn–Fe–Mn–Al–O, Pt/γ-Al₂O₃, Ru/CeO₂, Ru/C) have been prepared and used to remove N-containing organic contaminants while processing toxic and hazardous industrial waste waters using wet oxidation by air (WAO). The autoclave tests of catalysts were done to reveal the main advantages of catalysts in water presence at high pressures and temperatures. Catalyst activity was determined with regard to oxygen interaction with model mixtures (water–organic contaminant: acetonitrile, carbamide, dimethyl formamide, or multi-component mixture of aliphatic alcohols). Activity tests were done in a static reactor under ideal mixing regime. Reagents and products were monitored using gas chromatograph Cvet-560, Millichrom-1 HPLC, and routine chemical analysis. Optimum process conditions for the best catalyst (Ru/graphite-like carbon) are as follows: partial oxygen pressure – 1.0 MPa, temperature – 473–513 K. At 0.5–5.0 MPa total pressure and 433–523 K catalysts show high water-resistance and high activity level (residual content of toxic compounds is less than 1%, and no NO_x and NH₃ are detected). There are no legal restrictions on catalysts operation, since they are harmless to environment.     

电化学还原处理含氮化合物研究现状与展望

根据电极材料的不同,分别就硝酸盐、氮氧化物、硝基苯的电还原技术发展进行了论述,并介绍了电化学还原技术中的几种反应器。指出电极材料是影响电化学还原效果的关键因素,开发改性多金属电极和复合薄膜电极已成为电化学还原含氮化合物研究一种趋势。未来的研究重点主要在成本低、对还原产物具有选择性的电极开发,基于三维电极材料的电化学过滤反应器设计,及电极材料的耐久使用和保养再生方面。     

Determination and mutagenic activity of nitrogen-containing thiophenic compounds in coal-derived products

Polycyclic aromatic compounds containing both nitrogen and sulphur heteroatoms in aromatic rings were determined in a coal-derived liquid and a coal tar by capillary column gas chromatography and gas chromatography-mass spectrometry. G.c. with a flame photometric detector was used to analyse the nitrogen-containing polycyclic aromatic compound fraction obtained by adsorption chromatography on neutral alumina. The four possible isomers of the azadibenzothiophenes, and various other azathiophenic compounds, were positively identified by comparison with retention data of newly synthesized standard compounds. The aminodibenzothiophenes were the major nitrogen/sulphur-containing heterocycles in the coal liquid, while the azathiophenic compounds were the major ones in the coal tar. The differences between the two coal-derived products were related to the reaction conditions during their production. The four isomers of the azadibenzothiophenes were assayed for mutagenicity using the Ames test and compared with the mutagenicities previously reported for the aminodibenzothiophenes. It was found that the azadibenzothiophenes were not mutagenic, as opposed to the aminodibenzothiophenes.     

Porous structure and sorption properties of nitrogen-containing activated carbon

Nitrogen-containing activated carbon (NAC) derived from ammonium humates was produced and its porous structure (specific surface, pore volume) investigated. The NAC is mesoporous activated carbon with surface area of 557 m²/g and containing 2.4 wt.% of nitrogen. Sorption characteristics (sorption activity of iodine, methylene blue, benzene and metal ions Cu²⁺ and Pb²⁺) of NAC are compared with activated charcoal and BAU-A.     

Effects of the addition of ultrasound‐pulsed gelatin to chitosan on physicochemical and antioxidant properties of casting films

This study investigated the performance of chitosan based films with added, high‐intensity ultrasound‐pulsed, gelatins (42, 52, 71 and 84 W cm^?2). The mechanical, structural, chemical and antioxidant properties were investigated, to evaluate the potential of ultrasound as a technique to improve film properties. The tensile strength and elastic modulus of films containing ultrasound‐pulsed gelatins showed a significant increase, while the elongation parameter showed a significant decrease. Micrographs showed that all films presented agglomerations. The infrared spectra of the films displayed characteristic shifts in the chitosan and gelatin spectra, which may be the result of hydrogen bridge interactions and electrostatic interactions between the two polymers. The antioxidant capacity was analyzed through the ferric reducing antioxidant power (FRAP) assay and the 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS) assay of films and showed that gelatins treated with higher acoustic intensity had improved antioxidant capacity. High‐intensity ultrasound‐treated gelatin enhanced the strength, elasticity and antioxidant properties of the chitosan based films. © 2020 Society of Chemical Industry     

Improvement in the properties of low carbon MgO-C refractories through the addition of graphite-SiC micro-composite

Graphite–SiC micro-composites have been prepared in–house by carbothermal reduction process. Controlling the process parameters including the weight ratio of SiO₂ to graphite as well as carbothermal reduction temperature during the micro-composite preparation favors the homogeneous formation of SiC with preferred morphologies like ribbons and whiskers/fibers. The micro-composite modified low carbon MgO-C refractories have exhibited significantly improved bulk properties over the standard composition. To understand the beneficial role of SiC reinforcement on hot strength performance under air oxidizing conditions, we propose a scaling parameter known as strength factor (fs) based on the ratio of hot strength (HMOR) to cold strength (CCS). Correlating the strength factor data (fs) with oxidative damage provides new insights into the reinforcing effects of distinct SiC morphologies in this new class of micro-composite fortified refractory systems over the standard compositions.     

Enhancement in pyroelectric properties of PZT‐PVA polymer nanocomposites with addition of PAA

Composites comprising of pyroelectric ceramics and electro‐active polymers have gained importance currently as materials for thermal sensing applications, as their unique features and relevant properties can be tailored easily. In this work nanoparticles of PZT have been embedded into PVA/PAA copolymer matrix to form 0 to 3 nanocomposites. Films of the composites are prepared following solvent cast method after dispersing ceramic nanopowder homogeneously in the copolymer matrix with different wt % of the PZT powder. Relevant properties such as dielectric constant and loss factor, pyroelectric coefficients, thermal conductivity, and specific heat capacity as well as Shore hardness have been measured. The material figures of merit for pyroelectric detection have also been determined and reported. It is found that pyroelectric sensing properties of a film of the composite with 20 wt % PZT are comparable to those of commercially used β‐PVDF film for the same application, but with a lower figure of merit. However, it provides greater mouldability and simpler processibility for the fabrication of bulk sensors and actuators. So this composite can be considered as a potential material for the design and fabrication of mouldable pyroelectric detectors and actuators. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41142.