Glycerol Valorization: Dehydration to Acrolein Over Silica-Supported Niobia Catalysts

The catalytic dehydration of glycerol to acrolein is investigated over silica-supported niobia catalysts in a continuous fixed-bed gas-phase reactor. Various supported niobia catalysts are prepared and characterized using surface analysis and spectroscopic methods (XRD, UV–Vis, XPS, N₂ adsorption), as well as with ammonia adsorption microcalorimetry. Good results are obtained with initial glycerol conversions of over 70% and with 50–70% selectivity to acrolein. We investigate the influence of changing the catalyst acid strength by varying the niobia content and catalyst calcination temperature. Glycerol conversion and acrolein selectivity depend on the surface acid strength. Catalyst deactivation by coking is also observed, but simple oxidative treatment in air restores the activity of the catalysts completely.     

Aramid–multiwalled carbon nanotube nanocomposites: effect of compatibilization through oligomer wrapping of the nanotubes

Aramid–multiwalled carbon nanotube (MWCNT) nanocomposites with different CNT loadings were prepared by the solution‐blending technique. Aramid oligomeric chains having reactive amine end‐groups were covalently grafted and wrapped over the surface of acid‐functionalized MWCNTs. The presence of functional groups and surface modification of MWCNTs were studied using Raman, Fourier transform infrared and X‐ray photoelectron spectroscopic and transmission/scanning electron microscopic techniques. Addition of these MWCNTs resulted in a homogeneous dispersion throughout the aramid matrix. Dynamic mechanical thermal analysis showed an increase in the storage modulus and the glass transition temperature involved with α‐relaxations on CNT loading. The coefficient of thermal expansion (CTE) of aramid was reduced on loading with such CNTs. Strong interfacial interactions of the matrix with the surface‐modified CNTs reduced the stress‐transfer problem in the composite material and resulted in higher modulus of 4.26 GPa and a glass transition temperature of 338.5 °C, whereas the CTE was reduced to 101.8 ppm °C^?1 on addition of only 2.5 wt% CNTs in the aramid matrix. © 2016 Society of Chemical Industry     

The effect of sintering atmospheres on the properties of CSBT-0.15 ferroelectric ceramics

Ca_0.15Sr_1.85Bi₄Ti₅O₁₈ (CSBT-0.15) ferroelectric ceramics were developed by the conventional solid-state reaction method under various sintering atmospheres. The influences of these sintering atmospheres on grain orientation, grain size, oxygen vacancies, ferroelectric properties and leakage mechanisms were systematically investigated. It was found that the samples sintered under N₂ showed higher a-axis orientation and smaller grain sizes than those sintered under O₂ and air. From XPS analysis, it can be observed that the amount of Ti³⁺ in the ceramics sintered under N₂ is relatively high, which indicates a high number of oxygen vacancies in these samples. The samples sintered under N₂, air and O₂ all delivered well-saturated hysteresis loops with a remnant polarization (2Pr) of 13.8?μC/cm², 12.4?μC/cm² and 7.2?μC/cm² and corresponding coercive fields (2Ec) of 100?kV/cm, 86?kV/cm and 80?kV/cm, respectively. At 70?kV/cm, the leakage current densities of the samples sintered under N₂, air and O₂ are 4.2?×?10^?6 A/cm², 1.9?×?10^?6 A/cm² and 1.0?×?10^?6 A/cm², respectively. The leakage conduction mechanism transformed from Ohmic conduction in a relatively low applied electric field range (0–15?kV/cm) to space-charge-limited conduction (SCLC) in higher electric field ranges.     

烧结理论进展—1.烧结单元模型建立方法之比较

本系列文章系统介绍了重力烧结初始阶段计算机模拟的最近进展。本文为此系列文章的第一部分,综述了烧结单元模型的建立方法及颈长方程的求解过程。烧结单元颈长方程是压坯烧结模拟的基础,本文讨论了烧结单元模型研究中的不足之处,提出了进一步完善的方法。     

弯管一次合成设备

研制了用于弯管一次合成的设备.该设备由三部分组成:主体部分、控制部分和监视部分.主体部分包括电动机、减速箱、安装盒和机架;控制部分包括温度检测仪、调速器和计算机;监视部分包括电视和摄像头.使用该设备可实现弯管一次合成过程的全自动控制,并合成出φ325 mm的陶瓷复合弯管.     

煤系高岭土合成堇青石工艺研究

研究了化学组成、烧成温度和添加剂对以煤系高岭土为主要原料,偏SiO2配方设计合成堇青石的堇青石含量、烧结性能、热膨胀系数及显微结构的影响.结果表明:在1340℃下堇青石合成效果最好,堇青石含量达90%以上.在此基础上引入了四种添加剂来促进烧结和降低热膨胀系数,其中引入BaCO3的效果最好,可得到堇青石含量为95%、热膨胀系数为1.84×10-6/℃的合成堇青石原料.     

Cs exchanged phosphotungstic acid as an efficient catalyst for liquid-phase Beckmann rearrangement of oximes

Cs exchanged phosphotungstic acid is a highly efficient and environmentally benign solid acid catalyst for the liquid-phase Beckmann rearrangement of ketoximes to the corresponding amides. The catalysts Cs_xH_3−xPW₁₂O₄₀ (x = 1.5, 2, 2.5 and 3) were prepared by a titration method. The characterization results indicated that the primary Keggin structure remained intact after exchanging the protons with Cs ions. Moreover, the Cs exchanged catalysts were insoluble and exhibited larger BET surface area than the parent acid. The catalysts exhibited high reactivity and selectivity for the formation of -caprolactam, the precursor of Nylon 6, from cyclohexanone oxime. The catalyst can be recovered after reaction without any structural transformation.     

Fractional IWSOA-LB: Fractional Improved Whale Social Optimization Based VM Migration Strategy for Load Balancing in Cloud Computing

International Journal of Wireless Information Networks - Data centres have seen significant growth recently as a result of the phenomenal rise of cloud computing. These data centres typically use...