超临界二氧化碳介质中的有机反应*

本文主要介绍了超临界近5年来超临界二氧化碳中的有机反应研究的最新进展,包括加氢反应、氧化反应、羰基化反应、碳碳键形成反应、酯化反应和酶催化反应的研究现状;同时,还介绍了超临界二氧化碳作为反应底物用于合成碳酸酯和氨基甲酸酯的研究进展;并对未来的发展进行了展望。     

超临界二氧化碳中过渡金属催化有机反应研究进展

主要综述了近年来超临界二氧化碳作为反应介质过渡金属催化有机反应的最新进展.通过与常规有机溶剂中有机反应的对比,着重介绍了超临界二氧化碳作为反应介质在有机反应中所显示出的优越性,例如调控反应的选择性,提高反应速度和增加催化剂催化效率等.     

孤岛渣油超临界水-合成气中悬浮床加氢裂化反应研究 Ⅰ. 催化剂的影响

利用超临界水-合成气为替代加氢氢源对孤岛渣油悬浮床加氢裂化反应进行了研究，设想利用超临界水中发生的水-气转化反应（CO+H2O→H2+CO2）为渣油加氢反应提供氢源，报道了孤岛渣油超临界水-合成气中悬浮床加氢裂化反应催化剂影响的研究结果。结果表明，催化剂在该反应中具有十分重要的作用，加入催化剂可以明显改善加氢裂化产物的分布和裂化反应产物的性质，降低裂化气体和抑制缩合生焦反应的发生。     

典型醇类物质超临界水氧化反应途径研究

采用自主设计的连续流动气封壁超临界水氧化反应装置,研究了典型醇类物质甲醇、乙醇和异丙醇在超临界水中氧化的反应途径,并归纳了醇类物质超临界水氧化反应的规律及特点。研究结果表明,甲醇超临界水氧化反应的主要中间产物为甲醛,同样条件下转化率较乙醇和异丙醇低;乙醇和异丙醇超临界水氧化反应的主要中间产物为丙酮、乙酸、乙醛和甲醇等。三种醇超临界水氧化过程中均涉及到大量活性自由基的相互作用,表现为脱氢、裂解和聚合等反应形式;产物包括碳链增长、不变、降低三种类型。总体来看,醇类物质超临界水氧化反应的趋势是向碳链降低的方向进行,即通过一系列中间产物最后生成CO2和水。     

超临界(压缩)二氧化碳介质中的选择氧化*

由于超临界二氧化碳（SCCO₂）具有稳定、安全、不燃、清洁无毒、粘度小、扩散快、可压缩的特殊性质,所以使得超临界二氧化碳非常适合作为催化反应的绿色溶剂.除此之外,多种气体在超临界二氧化碳中的溶解度很高,这对于那些受传质阻碍和易引起安全隐患的气相反应来讲,使用SCCO₂作为替代的反应溶剂具有重要的价值。值得指出的是：如果选择超临界二氧化碳作为氧化反应的溶剂,其自身不会发生反应而产生副产物,从而容易得到清洁的产物。本文主要讨论了超临界二氧化碳作为反应介质对醇、烯烃和烷烃等选择氧化反应的影响,通过与传统溶剂比较可以看出超临界二氧化碳作为氧化反应溶剂的优势,对近几年来以分子氧为氧化剂,以超临界二氧化碳为介质的催化选择氧化的反应体系作了综述,并对未来的发展提出了展望。     

煤焦油在超临界水中的改质研究

在自制的间歇式高压反应釜中，对煤焦油在超临界水中的改质反应进行了研究。考察了温度、反应停留时间、水密度等对产物分布及组成的影响。通过与N2气氛下的焦油常压热解、高压热解过程所得结果进行对比，表明煤焦油在超临界水中发生了轻质化反应，获得一定量的轻质化油品；超临界水介质的存在还对产气量和过程结焦产生一定的抑制作用。为获得较高的轻组分收率，最佳的反应条件为：450℃左右，反应停留时间约为20 min，水密度约为0.40 g/cm3在此反应条件下的轻质油收率为51.55 w%，比原料中的增加了约30％。     

典型醇类物质超临界水氧化反应途径研究

采用自主设计的连续流动气封壁超临界水氧化反应装置,研究了典型醇类物质甲醇、乙醇和异丙醇在超临界水中氧化的反应途径,并归纳了醇类物质超临界水氧化反应的规律及特点。研究结果表明,甲醇超临界水氧化反应的主要中间产物为甲醛,同样条件下转化率较乙醇和异丙醇低;乙醇和异丙醇超临界水氧化反应的主要中间产物为丙酮、乙酸、乙醛和甲醇等。三种醇超临界水氧化过程中均涉及到大量活性自由基的相互作用,表现为脱氢、裂解和聚合等反应形式;产物包括碳链增长、不变、降低三种类型。总体来看,醇类物质超临界水氧化反应的趋势是向碳链降低的方向进行,即通过一系列中间产物最后生成CO₂和水。     

超临界流体技术在萃取中的应用简介

超临界流体萃取技术具有许多传统技术所没有的快速、高效、高选择性、低能耗等优点,特别是超临界流体的特性是它可以代替高毒有机溶剂做反应介质,符合绿色化学的要求。本文综述了超临界流体的特性,介绍了超临界流体萃取的原理,归纳了超临界流体萃取的应用现状,并介绍了超临界流体的其他领域应用概况。     

纤维素在超临界水中的反应

纤维素是一种非常有价值的可再生资源,通过其反应可以获得多种有用的物质。对纤维素在超临界水中的反应进行了综述。在没有催化剂的情况下,纤维素在超临界水中水解生成葡萄糖、果糖、低聚物等;对纤维素水解的设备、产物分布以及纤维素水解反应机理进行了阐述。采用Ni,Pt,Ru,KOH等作催化剂,纤维素在超临界水中发生气化反应,生成的气体产物主要为H2,CO2和CH4;介绍了纤维素及其主要水解产物葡萄糖的制氢反应过程。对纤维素超临界水反应技术的发展前景进行了展望.     

超临界二氧化碳介质中钯催化伯胺羰基化反应的研究

以正丁胺为模板 ,比较了超临界二氧化碳介质和常规有机溶剂中钯催化伯胺羰基化反应的规律。研究结果表明 ,在超临界二氧化碳中钯催化伯胺羰基化反应的化学选择性发生了改变 ,而且助溶剂对反应的化学选择性和产率也有较大的影响     

Analytical strategies to determine antibiotic residues in fish

The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised.     

Asymmetric Catalysis: Science and Opportunities (Nobel Lecture)

Asymmetric catalysis, in its infancy in the 1960s, has dramatically changed the procedures of chemical synthesis, and resulted in an impressive progression to a level that technically approximates or sometimes even exceeds that of natural biological processes. The recent exceptional advances in this area attest to a range of conceptual breakthroughs in chemical sciences in general, and to the practical benefits of organic synthesis, not only in laboratories but also in industry. The growth of this core technology has given rise to enormous economic potential in the manufacture of pharmaceuticals, animal health products, agrochemicals, fungicides, pheromones, flavors, and fragrances. Practical asymmetric catalysis is of growing importance to a sustainable modern society, in which environmental protection is of increasing concern. This subject is an essential component of molecular science and technology in the 21st century. Most importantly, recent progress has spurred various interdisciplinary research efforts directed toward the creation of molecularly engineered novel functions. The origin and progress of my research in this field are discussed.     

Sol-gel Transition of Methylcellulose Solution in the Coexistence of Hexadecyltrimethylammonium Bromide and Sodium Chloride

The sol-gel transition of methylcellulose (MC) solution in the presence of NaCl and hexade-cyltrimethylammonium bromide (HTAB), together with MC/NaCl solution in the presence of HTAB and MC/HATB solution in the presence of NaCl, was investigated by the rheolog-ical measurements. It has been found that the sol-gel transition temperature of MC solution decreases linearly with the concentration of NaCl in solution but increases linearly with the concentration of HTAB in solution, respectively. However, the sol-gel transition temperature of MC/NaCl solution in the presence of HTAB keeps the same value, independent of theconcentration of HTAB in solution. On the other hand, the sol-gel transition temperature of MC/HTAB solution decreases linearly with the concentration of NaCl in solution. The experimental results suggest that, for MC/NaCl solution in the presence of HTAB, the salt-induced spherical micelles of HTAB should have formed in bulk solution. For MC solution in the absence of NaCl, no spherical micelles have been formed in bulk solution, though the concentration of HTAB in our experiment is almost one order of magnitude higher than the critical micelle concentration of HTAB in polymer-free solution. In fact, due to adsorption of HTAB on MC chains, the realconcentration of HTAB in bulk solution, is much less than the apparent concentration of HTAB dissolved in MC solution.     

脱发白发与微量元素关系研究

利用火焰原子吸收法测定了中国银行韶关节市分行４５８名职工头发中Ｃｕ，Ｆｅ，Ｚｎ，Ｃａ含量，运用统计学方法求出该人群中正常者与白发，脱发者Ｃｕ，Ｆｅ，ＺｎＣａ的特征含量，通过数据比较可看出，白发者Ｃｕ，Ｆｅ，Ｚｎ，Ｃａ的含量均低于正常组，而脱发者与正常组较接近，经相关性检验，证明了Ｃｕ，Ｆｅ，Ｚｎ，Ｃａ偏低的血发存在的相关性，与脱发没有相关性，经过性别比对，女性发中Ｃｕ，Ｆｅ，Ｚｎ，Ｃａ含量均高于男     

黄鸣龙——我国有机化学的一位先驱

黄鸣龙院士(1898-1979)1919年浙江医药专科学校毕业,1924年德国柏林大学有机药物化学博士;1924-1934年任浙江医专教授、主任,卫生署化学部主任;1934-1940年在欧洲先灵公司等从事研究工作;1940年回国在昆明任中研院化学所研究员,兼任西南联大教授;1945年赴美在哈佛大学,默克公司从事研究工作。1952年绕道欧洲回国,先后在中国人民解放军医学科学院化学系和中国科学院上海有机化学研究所任研究员。1955年当选为中国科学院学部委员(院士)。黄先生一生从事有机化学的教育和研究工作,他在有机化学的“结构与机理”以及“反应和合成”二大方面都作出了在国内外具有深远影响的工作。20世纪40年代黄先生发现了变质山道年4个立体异构体的循环转变,堪称立体化学的经典之作;1948年发表了黄鸣龙还原反应;1952年归国后引领和发展了我国的甾体化学研究,带领了我国甾体药物的生产发展,是我国甾体药物工业的奠基人。黄先生治学严谨,既重视应用研究,又强调基础研究;关注学习新知识、新概念,又更重视实验技术。黄先生教书育人,身体力行,是我国有机化学发展的先驱者和奠基人。     

Radiochemistry teaching and research activities in Brazil

Summary Much concern has been expressed lately about the decline of teaching and research activities in radiochemistry in many countries, as was discussed in an IAEA Technical Meeting in Antalya, Turkey, in 2002, and also at MTAA-11 in Guildford, UK. In the IAEA meeting, a survey was presented about the current situation in different regions of the world (Eastern Europe, East and West Asia, Africa, North America and Latin America) by experts of each region. In the case of Brazil, which has nuclear research reactors and also cyclotrons in operation, the teaching and research activities in radiochemistry are concentrated in the three main institutes of the Brazilian Nuclear Energy Commission, in the University of S?o Paulo and in other universities, in different regions of the country. In the present paper, a closer look is given to the radiochemistry teaching and research activities that are being conducted nowadays in Brazil, comprising: number of radiochemistry courses and students being formed, main research areas being conducted, as well as research and production of radioisotopes for nuclear medicine, using nuclear reactors and cyclotrons.     

The heat of dissolution of uranyl nitrate in aqueous nitrate solutions

Conclusions A model has been suggested to explain the observed relationship between the measured heats of dissolution of uranyl nitrate in aqueous nitrate solutions and the concentration of the salting-out agent. The model describes the change in the structure of water in the solution with change in its concentration. On the one hand, a destruction of the water structure by ions occurs, which is weakened with increase in the distance from the ion, and leads to such irregularity in the distribution of water molecules in the solution that the mean number of molecules of water in unit volume is increased with increase in the distance from the ions. In experiments on the heat of dissolution this increase leads to increased hydration of the uranyl cation and reduction in the endothermicity of the dissolution with increase in the concentration of the solution. On the other hand, an interaction occurs between the ions of the salting-out agent and the water molecules in the solution, leading to the opposite result: There is an increase in the mean number of water molecules of the solution in unit volume in the direction of these ions. In experiments on the heat of dissolution this is revealed in the dehydration of the uranyl cation, and correspondingly in an increase in the endothermicity of the dissolution with increase in the concentration of the solution. The proposed model is in harmony with data on vapor pressure above the solutions (the relationship between the activity coefficient of the water and the concentration of the solution).Translated from Zhurnal Strukturnoi Khimii. Vol. 3, No. 2, pp. 143–150, March–April. 1962     

Effect of a d.c. electric field on the fluorescence spectra of cationic polymethine dyes in a polymer film

We have observed that in an external d.c. electric field, in the differential fluorescence spectra of both symmetric and asymmetric polymethine dyes in a polymer film, the intensity of the emission in the long-wavelength region of the band increases while the intensity in the short-wavelength region decreases. In symmetric polymethines, these effects are opposite to those in the differential absorption spectra, while in asymmetric polymethines they are symbatic. The spectral effects were interpreted by a change in the probability of the vibronic transitions due to redistribution of electron density in the chromophore, in the ground state and the excited state of the dye, in an external electric field. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 343–347, November–December, 2008.     

Histological study of some Echium vulgare, Pulmonaria officinalis and Symphytum officinale populations

Plants living in different ecological habitats can show significant variability in their histological and phytochemical characters. The main histological features of various populations of three medicinal plants from the Boraginaceae family were studied. Stems, petioles and leaves were investigated by light microscopy in vertical and transverse sections. The outline of the epidermal cells, as well as the shape and cell number of trichomes was studied in leaf surface casts. Differences were measured among the populations of Echium vulgare in the width and height of epidermis cells in the stem, petiole and leaf, as well as in the size of palisade cells in the leaves. Among the populations of Pulmonaria officinalis significant differences were found in the length of trichomes and in the slightly or strongly wavy outline of epidermal radial cell walls. Populations of Symphytum officinale showed variance in the height of epidermal cells in leaves and stems, length of palisade cells and number of intercellular spaces in leaves, and the size of the central cavity in the stem. Boraginaceae bristles were found to be longer in plants in windy/shady habitats as opposed to sunny habitats, both in the leaves and stems ofP. officinalis and S. officinale, which might be connected to varying levels of exposure to wind. Longer epidermal cells were detected in the leaves and stems of both E. vulgare and S. officinale plants living in shady habitats, compared with shorter cells in sunny habitats. Leaf mesophyll cells were shorter in shady habitats as opposed to longer cells in sunny habitats, both in E. vulgare and S. officinale. This combination of histological characters may contribute to the plant's adaptation to various amounts of sunshine. The reported data prove the polymorphism of the studied taxa, as well as their ability to adapt to various ecological circumstances.     

Research progress of graphene-based nanomaterials for the environmental remediation

Graphene is a two-dimensional nanomaterial with huge surface area,high carrier mobility and high mechanical strength.Because of its great potential in nanotechnology and environmental protection,it has attracted much attention in environmental and energy fields since its discovery in 2004.Although graphene is a star material,many reviews have introduced its use in terms of energy,the research progress in the field of environment,especially water pollution control,has been rarely reported.Here,we review exhaustively the research progress of graphene-based materials in environmental pollution remediation in the past ten years.Firstly,the advantages and classification of graphene were introduced.Secondly,the research progress and main achievements of graphene and its composites in the fields of photocatalytic degradation,pollutant adsorption and water treatment were emphatically described,and the mechanism of action in the above fields was summarized.Finally,we discuss the problems existing in the preparation and summarize the application of graphene in the environment.