Selective Hydrogenation of Cinnamaldehyde over (111) Preferentially Oriented Pt Particles Supported on Expanded Graphite

(111) preferentially oriented Pt nanoparticles supported on expanded graphite were prepared by impregnation of the support with an aqueous solution of H₂PtCl₆. The catalyst was characterized by a number of techniques and tested in the liquid-phase hydrogenation of cinnamaldehyde. The preferential surface orientation of the metal particles favours a very high selectivity towards the hydrogenation of the carbonyl bond of cinnamaldehyde to yield cinnamyl alcohol. The performance of this catalytic system is comparable to that obtained with similar catalysts prepared by more complex methods. Furthermore, expanded graphite provides a good alternative as support to other graphitic materials such as carbon nanotubes and carbon nanofibres.     

Turbulence decay behind expanded metal screens

An experiment study of the turbulent flow behind expanded metal screens has been carried out in a low‐turbulence wind tunnel using an X‐probe hot‐wire anemometer system. The expanded metal screens turn flow due to a complex array of vaned elements. The flow turning was found to vary accordingly with the dimensions of the strands that make up the screen. The turbulence generated by the screens decays at a rate proportional to the downstream distance to the power ‐ 5/7, consistent with studies in the literature of conventional screens types, and was found to scale with the thickness of the screen strands. The mean velocity, pressure drop and turbulence characteristics of expanded metal screens are presented.     

Recycled Polyolefin-Based Plastic Wastes for Sound Absorption

Recycling of high-volume polyolefin-based packaging wastes in India is challenging, as they have low recycle value, high levels of contamination, and lack of direct processing methods. This work discusses a two-stage mechanical processing method for recycling the polyolefin-based plastic wastes that are not conventionally recycled. With the objective of improving specific properties like sound absorption and noise reduction, inhomogeneities were introduced in the recycled product. This was achieved by mixing polyolefin-based packaging wastes with other waste materials such as plastic-coated aluminium foils, expanded polystyrene, and coir pith in varying quantities. More than 30 times volume reduction was achieved by a two-stage compression molding process. The sound absorption properties of the recycled materials are found to be comparable to expanded polystyrene and glass wool when small quantities (2–3 wt%) of materials like expanded polystyrene waste and coir pith were added. Impact strength of the recycled material decreased with increasing amounts of secondary additives like metal foils. Flexural strength of the recycled material was found to be maximum at about 30 wt% of metal foils. The end product could find applications in the construction industry due to the sound-absorption properties and the mechanical strength.     

板网波纹填料的研究

本文根据传质理论,综合了丝网填料与板波填料的优点,研制出一种“板网波纹填料”,这种填料由金属薄板经冲切拉伸成金属板网,然后压制成波纹填料。我们观察了液体在板网表面的成膜情况,测定了其流体力学与传质性能。结果表明,板网填料具有重量轻、压降低、效率高的优点。用其代替丝网填料时,投资可降低25％。     

Cumulative damage of reinforced concrete subjected to repeated impact

This study was performed to develop methods of measuring the cumulative damage of steel reinforced concrete slabs subjected to repeated impact. Cumulative damage was monitored by measuring the crater depth and the reduction in ultrasonic pulse velocity across the impact region. Crater depth generally increased with increasing number of impacts and therefore was determined to be a reasonable indicator of cumulative damage. The percent reduction in velocity generally increased with increasing number of impacts up to about 40 percent or more of the total number of impacts to failure. Beyond that, interpretation of the ultrasonic results with respect to the failure mechanism appears necessary. The addition of steel fibers to the bar grid reinforcement resulted in substantial increases (about 2 to 7 times or more) in the total number of impacts to failure as compared to specimens with only bar grid or expanded metal placed at the midpoint of the slab thickness.     

扩张阳极改性膜电槽技术应用

采用扩张阳极改性膜电槽新技术将废、旧金属阳极片改制成扩张阳极片,缩小阴阳间距,使极距和电流分布更均匀、更合理,降低溶液电压降;再配套吸附技术,平均可降低30-Ⅲ型单槽电压0．2V以上,而且将隔膜电解槽改制成扩张阳极电解槽后,与原阳极片的互换性大,投资小,见效快,节电效果明显：     

聚合金属酞菁的合成及研究进展

介绍了聚合金属酞菁的特性,因其具有大的共轭结构和较高的化学稳定性,和芳香环既有电子给体的特性、电子受体的特性,因此表现出良好的电催化氧还原活性;聚合金属酞菁作为催化剂,能使氧化反应在低温下高效进行,作为敏化剂,能有效提高光电转换效率.阐述了国内外聚合金属酞菁的研究方法和应用前景,提出了自由设计聚合金属酞菁分子结构,拓展...     

Dry Reforming of Hydrocarbon Feedstocks

Developments in catalyst technology for the dry reforming of hydrocarbon feedstocks are reviewed for methane, higher hydrocarbons and alcohols. Thermodynamics, mechanisms and the kinetics of dry reforming are also reviewed. The literature on Ni catalysts, bi-metallic Ni catalysts and the role of promoters on Ni catalysts is critically evaluated. The use of noble and transitional metal catalysts for dry reforming is discussed. The application of solid oxide and metal carbide catalysts to dry reforming is also evaluated. Finally, various mechanisms for catalyst deactivation are assessed. This review also examines the various process related issues associated with dry reforming such as its application and heat optimization. Novel approaches such as supercritical dry reforming and microwave assisted dry reforming are briefly expanded upon.     

Reaction of hydrous inorganic metal salts in CO2 expanded ethanol: Fabrication of nanostructured materials via supercritical technology

The fabrication of nanostructured materials from hydrous inorganic metal salt processed in supercritical CO₂ (scCO₂) expanded liquids has advantages to obtain good results. However, the behavior of the inorganic salts and the detailed reaction mechanism are still unknown up to now. In this work, the actual behavior of hydrous inorganic metal salts in CO₂ expanded ethanol at the temperature of 50-200 °C, including the phase behavior, deposition mechanism, reaction rate and the effect of templates on the deposition were systematically investigated by using XRD, FTIR, CHN-analysis, TGA, ICP-AES. A series of experimental parameters such as CO₂ flow rate, expand procedure, reaction temperature and time have been discussed, as well as the roles of CO₂ and H₂O (often originated from salts and/or solvent but always neglected) were studied in this contribution. Significantly, a coordination-decomposition (C-D) was proved to be the converting mechanism for the precipitation of the hydrous inorganic metal salts, rather than the fuzzy decomposition.     

Structural diversity in expanded porphyrins

Inspired by the chemistry of porphyrins, in the last decade, a new research area where porphyrin analogues such as expanded, isomeric, and contracted porphyrins have been synthesized, and their chemistry has been exploited extensively. Expanded porphyrins are macrocyclic compounds where pyrrole or heterocyclic rings are connected to each other through meso carbon bridges. Depending on the number of pyrrole rings in conjugation or the number of double bonds linking the four pyrrole rings expanded porphyrins containing up to 64 pi electrons are reported in the literature. The interest in these systems lies in their potential applications as anion binding agents, as photosensitizers for photodynamic therapy (PDT), in antisensing applications, as MRI contrasting agents, and more recently, as material for nonlinear optical application. Expanded porphyrins containing more than four pyrrole or heterocyclic rings, such as sapphyrin (five pyrrole), rubyrin (six pyrrole), heptaphyrin (seven pyrrole), and octaphyrin (eight pyrrole), are reported in the literature. Furthermore, substituents on expanded porphyrins can be attached either at the meso carbons or at beta-pyrrole positions. beta-substituted expanded porphyrins generally adopt normal structure where all the pyrrole nitrogens point inward in the cavity 1, while the meso-substituted expanded porphyrins exhibit normal 2, inverted 3, fused 4, confused 5, and figure eight 6 conformations. The conformation of expanded porphyrin is dependent on the nature of the linkage of the heterocyclic rings, the nature and the number of the heteroatoms present in the cavity, and the state of protonation. It is possible to change one conformation to another by varying temperature or by simple chemical modification, such as protonation by acids. An understanding of the structure-function correlation in expanded porphyrins is an important step for designing these molecules for their potential applications. In this context, even though several meso aryl expanded porphyrins are reported in literature, there is no comprehensive understanding of structural diversity exhibited by them. In this Account, an attempt has been made to provide a systematic understanding of the conditions and circumstances that lead to various conformations and structures. Specifically, the structural diversities exhibited by five pyrrolic macrocycles to ten pyrrolic macrocycles are covered in this Account. In pentapyrrolic systems, sapphyrins, N-fused, and N-confused pentaphyrins are described. It has been shown that the positions of the heteroatom affect the conformation and in turn the aromaticity. In hexapyrrolic systems, rubyrins and hexaphyrins are covered. The conformation of core-modified rubyrins was found to be dependent on the number and nature of the heteroatom present inside the core. Further, in the hexapyrrolic systems, an increase in the number of meso carbons from four (rubyrin) to six (hexaphyrin) increases the conformational flexibility, where different types of conformations are observed upon going from free base to protonated form. Heptapyrrolic and octapyrrolic expanded porphyrins also exhibit rich structural diversity. Octaphyrins are known to exhibit figure eight conformation, where the macrocycle experiences a twist at the meso carbon, losing aromatic character. By suitable chemical modification, it is possible to avoid the twist, and planar 34 pi core-modified octaphyrins have been reported that show aromatic character and obey the (4 n + 2) Hückel rule. The structural diversity exhibited by nine pyrrolic macrocycles (nonaphyrins) and ten pyrrolic macrocycles (decaphyrins) are also described.     

金属阳极电解槽改制的可行性分析

普通金属阳极电解槽槽电压高、电耗大。金属阳极改制为扩张阳极降低生产成本，适用于运行时间长的氯碱企业的技术改造。     

Removal of cadmium from dilute aqueous solutions with a rotating cylinder electrode of expanded metal

The removal of cadmium from dilute solutions using a continuous undivided electrochemical reactor with a rotating cylinder cathode of expanded metal is analysed. The effects of cathodic applied potential, size and orientation of expanded metal meshes and inlet cadmium concentration were ascertained. The results show that cadmium can be removed from dilute solutions (inlet concentration range 5–50 mg dm⁻³) with a high fractional conversion of between 35 and 40% depending on the operating conditions. Thus a minimal residual cadmium concentration of 3 mg dm⁻³ was achieved. The specific energy consumption increases from 0.6 to 2 kWh mol⁻¹ as the cadmium concentration decreases. Copyright © 2003 Society of Chemical Industry     

A parameter characterizing the geometry of expanded metal. II. Natural convection mass transfer at expanded metal electrodes

Free convective mass transfer rates at vertical electrodes of expanded metal were measured by the electrochemical method. Electrode height and electrolyte concentration were varied and the dependence of the expanded metal on the geometry and on the mesh orientation with respect to the vertical direction was investigated. A single equation was developed to correlate all the results. Besides the generalized dimensionless groups for natural convection the correlation includes a parameter characterizing the geometry of the expanded metal. The correlation also represents free convective mass transfer results obtained by other investigators with vertical mesh electrodes.Nomenclature a width of narrow space - A mean mesh aperture - c ₀ bulk concentration - d cavity diameter - d _p particle diameter - D diffusivity - g acceleration due to gravity - Gr Grashof number =gh³/v² - h electrode height - H cavity depth - k mass transfer coefficient - LD long dimension of expanded metal - R _h hydraulic radius - Sc Schmidt number=/D - SD small dimension of expanded metal - Sh Sherwood number=kh/D - void fraction - kinematic viscosity - density - electrode area per unit volume - electrode area per unit net area     

Reduced texaphyrin: A ratiometric optical sensor for heavy metals in aqueous solution

We report here a water-soluble metal cation sensor system based on the as-prepared or reduced form of an expanded porphyrin, texaphyrin. Upon metal complexation, a change in the redox state of the ligand occurs that is accompanied by a color change from red to green. Although long employed for synthesis in organic media, we have now found that this complexation-driven redox behavior may be used to achieve the naked eye detectable colorimetric sensing of several number of less-common metal ions in aqueous media. Exposure to In(III), Hg(II), Cd(II), Mn(II), Bi(III), Co(II), and Pb(II) cations leads to a colorimetric response within 10 min. This process is selective for Hg(II) under conditions of competitive analysis. Furthermore, among the subset of response-producing cations, In(III) proved unique in giving rise to a ratiometric change in the ligand-based fluorescence features, including an overall increase in intensity. The cation selectivity observed in aqueous media stands in contrast to what is seen in organic solvents, where a wide range of texaphyrin metal complexes may be prepared. The formation of metal cation complexes under the present aqueous conditions was confirmed by reversed phase high-performance liquid chromatography, ultra-violet-visible absorption and fluorescence spectroscopies, and high-resolution mass spectrometry.     

聚磷酸铵为主的膨胀型阻燃剂的协效研究进展

综述了近年来以聚磷酸铵（APP）为主的膨胀型阻燃剂用协效剂的开发和应用研究进展。介绍了膨胀型阻燃剂及其协效剂在高分子材料中的应用。重点论述了分子筛类的硅铝酸盐、金属氧化物及其盐类、金属氢氧化物、膨胀石墨等协效剂与膨胀型阻燃剂的协同阻燃机理。协效剂的加入能明显提高膨胀型阻燃剂的阻燃效率,减少了阻燃剂对基体性能造成的不利影响。同时,各类协效剂的成功开发为APP的表面改性和微胶囊化研究提供了有力的指导。     

Mass transfer in liquid films during absorption part I. Comparison of mass transfer models with experiments

Experimental values of the liquid-side mass transfer coefficient k_L for absorption of gases of low solubility in a liquid film flowing down a smooth and a rough wetted wall and down an expanded metal sheet are compared with selected mass transfer models. It is shown that the set of published k_L values available is insufficient to evaluate the most suitable model with which to describe the mass transfer mechanism. One of the distinguishing features of the various mass transfer models is the value of exponent m in the dependence of k_L on molecular diffusivity, k_L D^m. The range of published experimental values is 0.5 < m < 0.7; nevertheless, these results are insufficient for this purpose as well. It is shown that experimental determination of exponent m in the range of high Schmidt numbers could give new information about the phenomena very near the gas—liquid interface which is of importance when discussing the mass transfer mechanism in a liquid film during absorption. In discussing different models in this work special attention is given to the recently published film-penetration model proposed to evaluate k_L for absorption into a liquid film on an expanded metal sheet.     

ICP-MS法测定香精中重金属的不确定度研究

建立利用微波消解-ICP-MS检测香精中重金属的方法,并根据JJF1059-1999《测量不确定度评价与表示》对该方法进行不确定度分析。以重金属锑为例建立数学模型,包括对称重、标准溶液配制、实验人员、环境等因素引入的不确定度进行分析。其中在方法的不确定度评定过程中,应主要考虑不确定度贡献较大的分量,从而简化实验操作步骤,提高工作效率。在置信区间为95%时,k=2,得出不确定度结果为UC=56.10μg/kg,测量结果报告表示为：c=（492.13±56.10）μg/kg。     

Hydrodynamic modelling of the liquid-solid behaviour of the circulating particulate bed electrode

Experimental and modelling investigations of the hydrodynamics of the internal flow structure in the circulating particulate bed electrode (CPBE) are reported. The CPBE, a hybrid between an expanded packed bed and an entrained/fluidized bed, is particularly well suited for many electrochemical applications such as metal recovery and pollution treatments for metal containing effluents. This study deals with the fundamental hydrodynamics and particle dynamics of the CPBE. A mathematical model of the CPBE has been developed which successfully describes the motion of the particles and the fluid in the bed. It is shown that many of the flow characteristics of the circulating bed can be predicted using fundamental data. The validity of the proposed model was demonstrated by comparing predictions to experimental observations of several bed characteristics under various operating conditions.     

Electrochemical water disinfection Part I: Hypochlorite production from very dilute chloride solutions

Electrolytic production of hypochlorite in very dilute chloride solutions is investigated using platinum and iridium oxide coated titanium expanded metal electrodes as anodes. The dependence of the hypochlorite production rate on temperature, chloride concentration and current density was determined. It was found that the hypochlorite production rate is consistently higher on iridium oxide coated titanium compared to platinum coated titanium electrodes.