Green synthesis of bio-ethyl acetate over Egyptian natural red clay as a highly active,selective, and eco-friendly catalyst

The present work focused on the utilization of Egyptian red clay (ERC) without any treatment as a highly efficient, selective, and eco-friendly catalyst for synthesis of bio-ethyl acetate in the gas phase. The best conditions used in conventional fixed bed reactor were 130 cm³/min total flow rate of air with 1.6 and 2.1 vol% bio-ethanol and bio-acetic acid, respectively, 1 g clay catalyst calcined at 300 and 225°C reaction temperature. Under these conditions, the conversions to ester achieved were about 80 and 98% after 5 and 30 min, respectively, from the initial admission of the reactants into the reactor. The amount and type of surface acidity were identified by isopropanol reaction and chemisorption of basic probes. The results demonstrated that the majority of intermediate strength of BrØnsted acid sites are the key role for the dehydration reaction toward ester formation. The virgin and annealed clay solids were characterized using X-ray fluorescence (XRF), thermogravimetry (TG) and differential thermal analysis (DTA), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and N₂ sorption.     

微波消解–ICP–OES法测定陶土中铅和镉含量

建立微波消解–ICP–OES法测定陶土中铅和镉含量的方法。采用氢氟酸–硝酸作为消解液,微波消解法处理样品,消解液定容后直接进入耐氢氟酸的进样系统,用ICP–OES法测定陶土中重金属铅和镉的含量。结果表明,Pb和Cd检出限分别为0.027μg/m L和0.011μg/m L,回收率分别为90.5%~98.8%和95.0%~98.4%,测定结果相对标准偏差分别为1.38%和2.17%(n=7)。该方法具有快速、准确、灵敏度高等优点,适用于陶土中铅和镉含量的检测。     

Polypyrrole–montmorillonite nanocomposite as sorbent for solid‐phase microextraction of phenolic compounds in water

A fiber‐coated polypyrrole–montmorillonite nanocomposite was prepared for solid‐phase microextraction. The fiber coating can be prepared easily; it is mechanically stable and exhibits relatively high thermal stability. The prepared fiber was evaluated for the extraction of some phenolic compounds from aqueous sample solutions by gas chromatography–mass spectrometry. The effects of the extraction and desorption parameters including extraction time, extraction temperature, stirring rate, ionic strength, pH and desorption temperature and time have been studied. At optimum conditions, the repeatability for one fiber (n = 5), expressed as % relative standard deviation was between 6.5 and 7.8% for the phenolic compounds. The detection limits for the studied phenolic compounds were between 0.05–1.3 ng/mL. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost, thermal stability of the fibers, and high relative recovery in comparison to conventional methods of analysis.     

化整为零:聚合物/粘土纳米复合材料的微观结构和阻隔性能

在聚合物基体中掺入少量的层状硅酸盐所制备的聚合物／粘土纳米复合材料，其阻隔性能明显地优于纯聚合物及其传统的复合材料。实验及分析结果表明，聚合物／粘土纳米复合材料的微观结构和阻隔性能主要受控于粘土剥离后的径厚比．一简单的重整化群模型被用来评估粘土几何因素（诸如径厚比、取向、剥离程度等）对聚合物／粘土纳米复合材料阻隔性能的影响，所得到的逾渗阈值及最佳粘土含量与实验结果吻合。     

Colloidal forces between bitumen surfaces in aqueous solutions measured with atomic force microscope

Colloidal forces between bitumen surfaces in aqueous solutions were measured with an atomic force microscope (AFM). The results showed a significant impact of solution pH, salinity, calcium and montmorillonite clay addition on both long-range (non-contact) and adhesion (pull-off) forces. Weaker long-range repulsive forces were observed under conditions of lower solution pH, higher salinity and higher calcium concentration. Lower solution pH, salinity and calcium concentration resulted in a stronger adhesion forces. The addition of montmorillonite clays increased long-range repulsive forces and decreased adhesion forces, particularly when co-added with calcium ions. The measured force profiles were fitted with extended DLVO theory to show the repulsive electrostatic double layer and attractive hydrophobic forces being the dominant components in the long-range forces between the bitumen surfaces. At a very short separation distance (less than 4–6 nm), a strong repulsion of steric origin was observed. The findings provide a fundamental understanding of bitumen emulsion stability and a mechanism of bitumen “aeration” in bitumen recovery processes from oil sands.     

Selective Iodination of Benzylic Alcohols with KI/H<Subscript>2</Subscript>SO<Subscript>4</Subscript> Supported on Natural Kaolinitic Clay Under Microwave Irradiation

Summary.  Benzylic alcohols are selectively converted into their corresponding iodides using KI/H₂SO₄ supported on natural kaolinitic clay and microwaves. Received August 20, 2001. Accepted (revised) September 18, 2001     

冻结黏土力学特性分析及改进S-M蠕变模型1)

为合理描述人工冻结法施工的矿井土层力学特性,对某矿井土样的重塑土进行单轴抗压强度实验和单轴压缩蠕变实验,得到重塑冻结黏土在不同温度及载荷加载等级下的应力-应变曲线和蠕变曲线。实验结果表明：冻结温度越低,土样的单轴强度越大;相同冻结温度下,土样的蠕变变形随着应力水平的升高而增大。单轴压缩蠕变的等时应力-应变曲线随时间发展向应变轴靠拢;土样经历初始蠕变和等速蠕变两个阶段,在较高应力水平下有进入加速蠕变的趋势;对S-M模型中各参数的意义进行修正并考虑温度的影响,得到人工冻结黏土改进S-M蠕变显式模型,然后采用粒子群算法对人工冻结黏土S-M蠕变模型参数进行优化。改进S-M蠕变显式模型理论计算值与实验值吻合良好,表明改进S-M蠕变显式模型能较好模拟人工冻结黏土的蠕变特性。改进S-M蠕变显式模型为人工冻土蠕变计算提供一种新方法。     

含铁的柱撑膨润土光催化降解甲基橙

将两种含铁柱撑膨润土(Fe-Al-Bent和Fe-Bent)用作复相光催化剂, 表征结果证实它们具有很高的比表面积, 铁以高催化活性的α-Fe₂O₃存在于复相催化剂中. 以甲基橙为目标降解物, 考察了不同类型的催化剂、催化剂用量以及H₂O₂浓度对其降解的影响, 并与相应的均相Fenton反应进行了比较. 结果表明: 两种复相光催化剂的催化脱色性能和COD_Cr去除率都很高, 明显优于相应的均相Fenton反应, 且复合铁铝柱撑膨润土(Fe-Al-Bent)比单一的铁柱撑膨润土(Fe-Bent)催化性能更好, 此外它们还具有分离简单、重复使用性好等特点.     

Matrimid–polyaniline/clay mixed‐matrix membranes with plasticization resistance for separation of CO2 from natural gas

Mixed‐matrix membranes (MMMs) of Matrimid® and polyaniline/clay (PC) are investigated for CO₂/CH₄ separation and CO₂‐induced plasticization. PC particles are synthesized through in‐situ polymerization of aniline in the presence of organophilic clay and then incorporated into Matrimid by solution casting method. Chemical structure and morphology of PC powder and fabricated membranes are analyzed by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry/thermogravimetric analysis (DSC/TGA) and scanning electron microscopy (SEM). The XRD spectra of PC particles show the exfoliation of silicate layers throughout the polyaniline (PAni) matrix, and SEM images indicate flower‐petal morphology for PC particles. The permeability values of CO₂ and CH₄ increase 30–35% by incorporation of 10 wt% PC without any significant drop in selectivity. PC particles with flower‐petal morphology plays an important role in increasing the gas permeability values of both gases while Matrimid is the only phase that controls CO₂/CH₄ selectivity. The plasticization pressure was increased to 30 bar by incorporation of 10 wt% PC in the Matrimid matrix. CO₂ permeability and p_plast improved 35% and 200%, respectively, resulting in 300% enhancement in the capacity of MMM in the purification of natural gas with a selectivity of about 40. Copyright © 2016 John Wiley & Sons, Ltd.