锂/铌镁催化剂中碳酸锂的熔点与甲烷氧化偶联反应的活化和失活的关系

研究了铌掺杂的Li/MgO甲烷氧化偶联催化剂的反应性质及铌的助剂作用。铌的引入使得该催化剂上甲烷氧化偶联反应的活化温度降低50℃以上, 使此温度降到了催化剂中碳酸锂的熔点附近。试验观察到部分催化剂上甲烷氧化偶联反应的活性曲线在碳酸锂的熔点附近有一转折, 这一转折现象的出现与否及程度取决于制备条件。在碳酸锂的熔点附近, 含有铌的催化剂得到活化, 观察到无稀释气体时的反应引燃现象, 即温度增加几度活性便达到最大值。当在比碳酸锂熔点稍高的温度下且不稀释时反应, 含铌催化剂活性很高但很快失活, 在稍低于此熔点下则不失活, 但活性较低。这些试验结果表明, 含铌催化剂的活化与失活均与催化剂中的碳酸锂的相变化有关。试验还观察到了在稍高于碳酸锂的熔点下做寿命试验时, 甲烷氧化偶联反应的振荡现象。     

铁丝在氧气中燃烧的实验改进

“铁丝在氧气中燃烧”是初中化学教材中证明氧气化学性质的一个演示实验,该实验证明了氧气比较活泼,在一定条件下可以和金属发生剧烈反应。但是与木炭在氧气中燃烧、硫在氧气中燃烧、蜡烛在氧气中燃烧的演示实验相比,铁丝在氧气中燃烧的实验存在着一些不足的地方,针对这些不足,对铁丝在氧气中燃烧的实验进行了改进。1实验存在的问题按照教材要求,铁丝在氧气中燃烧的实验,须将铁丝绕成螺旋状,并在铁丝的末端绑上一根火柴杆,实验时先将火柴杆点燃,待火柴杆将燃尽时,迅速伸入盛满氧气的集气瓶中。这样的操作存在2个问题:第一,火柴燃烧的程度不…     

提高纤维素酶水解效率和降低水解成本

在我国可大量转化乙醇的是纤维质材料.纤维质材料转化乙醇的关键问题是纤维质转化为糖的过程,提高纤维素酶转化效率的方法有:(1)对纤维质材料进行预处理;(2)研究纤维素酶的最适作用条件;(3)纤维素酶的重复利用;(4)合理的发酵工艺等.本文分析了纤维素的结构以及纤维素酶的作用方式,总结了目前研究较多的几种纤维质材料预处理方法,及其对纤维素酶水解率的影响,并对研究纤维素酶的最适作用条件、纤维素酶的重复利用以及合理的发酵工艺进行了综述和分析.     

银镜的实验室制备

在高中化学“烃的衍生物”,“糖类、油脂、蛋白质”2章的教学中,安排了有关银镜反应的演示实验,其目的是通过实验证明含有醛基的有机物具有还原性。按照教材的方法进行实验操作,往往由于水浴的温度掌握不好,制得银镜的效果不理想。为了快速明显地观察到银镜的产生,采用平板玻璃     

2011年国际化学年《高分子通报》征稿启示

2011年是联合国确定的国际化学年,为纪念化学学科所取得的成就以及对人类文明的贡献,2011年化学年的主题是我们的生活,我们的未来。     

CO催化氧化用纳米材料及其最新研究成果

当前,环境问题和能源危机已经威胁到人类的健康和生存。用于环境治理和化学能源合成新概念的纳米催化材料越来越受到人们的关注。催化作为一个特殊的纳米现象,是纳米材料应用领域的一个重要方向,在环境净化、能量转化和新化学品的生产等方面具有广泛的应用前景。早期的一氧化碳(CO)催化氧化研究主要集中在催化剂的制备方法以及制备条件对催化反应的影响等方面。本文针对CO催化氧化这一基础课题,以影响CO催化氧化的关键因素(如金属颗粒的大小,金属与载体之间的相互作用以及载体本身的作用等)为主线,简要概述了近年来CO催化氧化的催化机理及相关催化剂的最新研究进展。同时,结合我们课题组的一些最新研究结果,进一步指出了纳米材料在CO催化氧化方面还存在的一些值得关注的问题,并对未来CO氧化催化剂的研究做出展望,提出一些可行的研究方向。     

漫话饮用水消毒剂

饮用水消毒剂的种类很多,国内大规模工业化生产主要还是用氯气来消毒。饮用水消毒的目的是杀灭水中可能引起霍乱、伤寒、痢疾等疾病的病菌与病毒。随着科学技术的发展和人们生活水平的提高,饮用水消毒剂也在不断发展,安全、高效、经济的消毒剂将成为主流。下面就目前使用或已开     

序言——《高分子通报》创刊20周年回顾

《高分子通报》是1988年10月创刊的。回顾20年来的发展历程,《高分子通报》是在各级领导的关怀下不断成长的,是在我国高分子科学领域的专家、学者的大力支持下发展的,也是在历届编委、编辑艰苦奋斗,辛勤耕耘下不断提高和前进的。早在1981年冬,昆明功能高分子学术会议中就正式提     

羟基甘氨酸溶液性质研究

采用核磁共振等仪器分析与官能团鉴定相配合的方法，对乙醛酸与铵盐反应形 成的羟基甘氨酸进行了研究。确认了羟基甘氨酸的结构，探讨了羟基甘氨酸的水溶 液中的主要存在形式，得出了与普遍接受的羟基甘氨酸在水溶液中不稳定的观点相 悖的结论。并对羟基甘氨酸的溶液稳定性，氨解，水解进行了研究。本结果为乙醛 酸以及羟基甘氨酸在有机合成上的应用提供了依据。     

在血卟啉衍生物光敏体系中DMPO捕集自由基的ESR研究

光照血卟啉衍生物(HPD)用于肿瘤的诊断和治疗已取得很大的成效,对此药理过程的分子机理的探索也开始引起生物和化学工作者的重视.我们的实验表明,在HPD光敏体系中自由基起着重要作用,特别是羟基自由基可能是HPD光致杀伤肿瘤细胞的主要原因.HPD光敏过程所产生的自由基的寿命极短,用化学方法或用一般ESR直接检测非常困难,但可被     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

物质分配系数的测定实验改进

实验教学目的是从解决实际问题出发,以实验技术训练和实验设计思想培养为目标。介绍了将单一的物质分配系数测定实验改进为综合实验,提高了实验效果及实验资源利用率。     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。