晶种数量对MOR分子筛上烷基转移反应的影响及反应机理研究

以丝光沸石(MOR)分子筛为催化剂,甲苯与三甲苯烷基转移反应为探针反应,系统考察了晶种数量变化对分子筛物化性能和催化性能的影响。研究表明,合成过程中晶种添加量的不同会显著影响催化剂的酸性、比表面积和孔体积,进而影响其催化剂活性和稳定性。当晶种添加量为8%时,MOR分子筛具有最多的B酸含量、最大的比表面积和孔体积,同时对应的催化剂活性和稳定性也最好。本研究还对甲苯和三甲苯烷基转移反应机理进行了深入研究,结果表明,发生在MOR分子筛上的烷基转移反应通过双分子中间体机理进行,并应用实验手段捕捉到了中间体的存在,证实了双分子中间体机理的合理性,同时推导出可能的反应机理路线图。     

能量色散X射线荧光光谱法分析金元时代的钧窑瓷器

应用能量色散X射线荧光光谱法测定了16个金元时期钧窑瓷器胎、釉样品的化学组成。由结果可知:金元钧瓷胎具有低硅高铝的北方瓷器特点,釉则多为钙碱釉。金元时期样品与北宋时期钧窑瓷器胎釉化学组成比较,金元时期钧窑样品的化学组成变化较大,从因子分析散点图可见,北宋钧官窑样品化学组成变化不大;金元钧窑与北宋钧民窑样品制作工艺上存在继承和发展的关系,但金元时期对原料选择和配方的控制已不如北宋时期严格,反映出金元时期的钧窑已处于衰落阶段。     

Effect of reaction medium on the radical polymerization and copolymerization of potassium and sodium p-styrenesulphonate

The kinetics of the homogeneous free radical polymerization of potassium p-styrenesulphonate and sodium p-styrenesulphonate (SSS) in water-salt, water-dioxane, water-dimethyl sulphoxide (DMSO), DMSO—dioxane mixtures and copolymerization of SSS with acrylamide in water-salt and water-DMSO mixtures have been investigated. The overall rate of the process, the kinetic orders with respect to monomer and initiator, overall activation energy and also the properties of the resulting polymers (molecular weight, copolymer composition and compositional inhomogeneity) depend on the nature of the reaction medium. It is mainly connected with the influence of ionic strength (due to varying ionogenic monomer concentration, addition of salts and also the change of the conversion degree) and with the influence of the polarity of solvent on the rate constants for propagation and termination. The chemical and physical characteristic of the reaction mainly influence parameters of the electrostatic interactions in the system “macroradical-counterions-anions of monomer”. This leads to conformational variation of polymer chains and influences the reactivities of growing macroradicals and ionogenic monomers in polymerization and copolymerization. Data on conductivity and viscometric measurements confirmed the dependence of the conformation of polymer and copolymer macromolecules upon the composition of the medium.     

Excited state properties of novel p- and n-type organic semiconductors with an anthracene unit

Photoinduced dynamics of novel p- and n-type organic semiconductors with an anthracene unit are theoretically investigated with quantum chemistry methods. The calculated vertical absorption and fluorescence frequencies of them are consistent with the experimental data. The changing tendencies of the dihedral angles between anthracene unit and trifluoromethylphenyl (or thiophene) in the photoinduced dynamics processes (vertical absorption and vertical fluorescence) are examined from the geometries of optimized ground and excited states. To study the influence of the individual units of the derivatives to the excited state properties of the derivatives, the energies and densities of frontier orbital HOMOs and LUMOs of the individual unit and the derivatives are studied in the processes of vertical absorption and fluorescence. The excited state properties of the two derivatives in the processes of vertical absorption and fluorescence are studied with 2D and 3D real space analysis methods, which are employed to study the electron–hole coherence and the excitation delocalization (with transition density matrix method), and charge and energy transfer (with transition and charge difference density method). Overall, the computed results remain in good agreement with the relevant experimental data, and the theoretical results promote deeper understanding to the optical and electronic properties of the semiconductor in the process of photoinduced dynamics.     

Control of structure and photophysical properties by protonation and subsequent intramolecular hydrogen bonding

Protonation and subsequent intramolecular hydrogen bonding as methods to control chain structure and tune luminescence in heteroatomic conjugated polymers were reported experimentally [A. P. Monkman et al., J. Am. Chem. Soc. 124, 6049 (2002)]. In this paper, the structure and photophysical properties of the model teraryl compound of phenylene-pyridylene copolymer before and after protonation are theoretically studied with quantum chemistry methods. From the optimized ground states, intramolecular hydrogen bonding to the adjacent oxygen atom in the alkoxy substituent planarizes the backbone of the molecules, and the optimized detailed results of compound 9 before and after protonation, such as the dihedral angles between the central benzene and the two pyridyl rings, the bond lengths, and the bond angles, are consistent with the experimental results. From the results of the calculated excited states, the protonation and subsequent intramolecular hydrogen bonding result in the redshifts of the absorption, the increase of the ionization energy, the increase of the electron affinity, the decrease of the energy difference of the highest occupied molecular orbital and lowest unoccupied molecular orbital, the decrease of the binding gap, and the delocalization of the electron-hole coherence. The photophysical properties of compound 9 before and after protonation are further studied with a three-dimensional real-space analysis method of transition and charge difference densities (study transition dipole moment and charge transfer in the absorption and fluorescence processes) and two-dimensional real-space analysis method of transition density matrices (study the electron-hole coherence and the excitation delocalization). The calculated results show theoretically an insight understanding on the influence of the protonation and subsequent intramolecular hydrogen bonding to chain structure and photophysical properties.     

化工单元操作中理论板与传质单元数之间关系的探究

填料塔与板式塔是化工单元操作过程中的常见设备,而填料塔中填料层高度的计算与板式塔中理论板数的确定是关键,教材中有关填料层高度的计算采用的是传质单元数法,而板式塔中理论板的确定采用是Mc Cable-Thiele方法来确定的,有关传质单元数与理论板它们之间的关系介绍的较少。本文采用吸收因子法详细介绍了理论板数与传质单元数的求法,并由此建立了它们之间的定量关系,可用于二类塔的比较,对于填料塔的分析与设计具有一定的指导作用,有助于对吸收与精馏单元操作过程的学习与理解。     

Numerical study of the kinetics of unimolecular heterogeneous reactions onto planar surfaces

In this paper we investigate two-dimensional in space mathematical models of the kinetics of unimolecular heterogeneous reactions proceeding onto planar surfaces. The models are based on Langmuir-type kinetics of the adsorption, desorption, and reaction including the surface diffusion of the adsorbate, surface diffusion of the product before its desorption, and slow desorption of the product from the adsorbent. It is also assumed that the reactant diffuses towards an adsorbent from a bounded vessel and the product diffuses from the adsorbent into the same vessel. Diffusivity of all species and kinetic coefficients are constants. The numerical simulation was carried out using the finite difference technique for four models: one model neglects the surface diffusion of the adsorbate and product, the second one includes the surface diffusion of the adsorbate and product, the third of them includes the surface diffusion of the adsorbate and neglects diffusion of the product along the surface, and the last one neglects the surface diffusion of the adsorbate and includes diffusion of the product along the adsorbent. By changing input parameters effects of the surface diffusion of the adsorbate and product and the slow desorption of the product are studied numerically.     

Polyolefins: The most promising large-volume materials for the 21st century

Polyolefins (POs) constitute an extremely interesting family of materials. They include large-volume materials such as polyethylene and polypropylene and specialty materials. Outstanding scientific and technology developments have led to the most aggressive, endless, always increasing, successful growth speed of any family of large-volume materials. For those of us who have lived through the entire PO adventure, from its problematic beginnings to the eventual successful developments of the last 25 years, it has been a quite unforeseeable and unexpected story not shared by the majority. The main reason for such behavior and the present situation is the inherent complexity of their catalytic systems, which are difficult to understand and manage, along with all the consequences in terms of the process versatility, the reliability and cost, the lack of product properties, and the possibility of new material creation and commercial availability. After the early commercial disappointments of the 1960s and early 1970s, the deep commitment of the industry in research and development, mostly aimed at an understanding of the catalysis and its improvement and management, created the basis for and led to the generation of new, elegant, and versatile processes and, most importantly, to the generation of new products and properties. It activated that dynamic and aggressive growth that, since the late 1970s, has characterized the entire PO market and still, at the beginning of the third millennium, is not showing any sign of decline. An attempt to provide a rational explanation for such a unique case of technological and commercial success in the history of materials has led us to the following conclusions. First, dramatic improvements in the polymer properties and the generation of new materials have been the key reasons for their commercial success and continuous market expansion. Second, the tremendous and dynamic development of new, elegant, and versatile technologies has been and is the fundamental prerequisite for the generation of that rich world of new properties and materials. Third, the strategic management of the technological background and potential for the creation of new properties and new applications has been and is the basis for the fast and successful market expansion. The key technological driving force has been the understanding and management of the catalytic system. The early generations of chromium-based and Ziegler–Natta catalysts, after a difficult beginning, have progressively accelerated in their development toward new revolutionary generations with outstanding potential in terms of the creation of new polymer properties. The most recent families of single-site catalysts, together with the still largely unexploited potential of the previous Ziegler–Natta, chromium, and vanadium catalysts, are showing the ability to guarantee the continued support and fueling of the expansion for several further decades. The development philosophy will always be more tuned toward the creation of low-cost, low-environmental-impact polymers and processes, with a minimum amount of constraints. Today, at the beginning of the new century, we see the PO future as still very bright because of the huge, unexploited potential of already existing and emerging technologies. The PO adventure continues and is still exciting like it was 50 years ago. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 396–415, 2004     

双定性双定量相似度法评价银杏达莫注射液的高效液相色谱指纹图谱

建立了色谱指纹图谱的双定性双定量相似度评价法,并应用于银杏达莫注射液的高效液相色谱（HPLC）指纹图谱的评价。采用反相HPLC,以芦丁为参照物峰,确定了41个共有峰,建立了银杏达莫注射液的对照指纹图谱。以双定性相似度S和S′、双定量相似度C和P评价银杏达莫注射液的HPLC指纹图谱,分别考察在大峰缺失和小峰缺失两种情况下,4个相似度指标的变化特征。S能反映化学成分的分布比例,受大峰影响严重,无法反映小峰的丢失; S′对所有指纹峰等权,反映小峰缺失灵敏,二者构成双定性相似度。C能反映样品共有峰的总体含量,但受大峰影响严重,无法反映小峰的缺失; P对所有峰积分值等权,能较好地反映小峰的变动,二者构成双定量相似度。因此,由S与S′、C与P构成的双定性双定量相似度法能同时监测大峰和小峰的变动与缺失,能准确地解决色谱指纹图谱的宏观定性和定量评价问题。同时还提出了方向余弦作为对照指纹图谱的特征指纹的概念和分解相似度的概念,以此考察了各指纹峰对相似度贡献的大小及其在不同程度缺失时4种相似度的变化情况。所建立的HPLC对照指纹图谱可用于银杏达莫注射液的质量控制。     

Effect of the solvent nature on the rheological properties of concentrated solutions of various polymers

The paper compares the viscous, high-elastic and viscoelastic properties of solutions in various solvents of four polymers (polyisobutylene, polystyrene, polymethyl methacrylate and acetyl cellulose) differing in chain rigidity and the intensity of molecular interaction, over a wide range of compositions for the linear region of the mechanical behaviour of these systems. For solutions of polyisobutylene and polystyrene, the effect of the nature of the solvent on the viscosity is determined by the inherent viscosity of the solvent and by the fact that solutions under isothermal conditions are not in corresponding states with respect to their glass transition temperatures. The high-elasticity modulus of polyisobutylene and polystyrene solutions is independent of the nature of the solvent and of temperature. This indicates that the fluctuating network of entanglements is insensitive to the nature of the solvent and that the free volume plays the determining role in the behaviour of these solutions. Solutions of acetyl cellulose and polymethyl methacrylate are characterized by a very strong dependence of the viscosity on the nature of the solvent (which cannot be explained by notions valid for solutions of the first two polymers) and also by a change in the high-elasticity modulus with variation in the nature of the solvent and temperature. This proves that the properties of solutions of polar polymers are determined both by the free volume and the density of the fluctuating network, which changes with the solvent and temperature. The shape of the relaxation spectra of solutions of various polydisperse polymers in solvents of different natures is the same, while the specific properties of the solutions are associated with the position of the spectra on the time scale, which determines the fundamental constants of the solutions, viz. the zero shear viscosity and the initial high-elasticity modulus.     

Adsorption of cyanine dyes on gold nanoparticles and formation of J-aggregates in the nanoparticle assembly

This paper describes the results of an investigation of the interparticle interactions and reactivities in the assembly of gold nanoparticles mediated by cyanine dyes. The combination of the positively charged indolenine cyanine dyes and the negatively charged gold nanoparticles is shown to form a J-aggregate bridged assembly of nanoparticles, in addition to hydrophobic interparticle and electrostatic dye-particle interactions. Such interparticle interactions and reactivities are studied by probing the absorption of J-aggregates and fluorescence from the dyes and the surface plasmon resonance absorption from the nanoparticles. The J-aggregation of the dyes adsorbed on the nanoparticles is shown to play an important role in the assembly of nanoparticles. The spectral evolution of the J-band of the dyes and the surface plasmon resonance band of the nanoparticles was found to be sensitive to the nature of the charge and the structure of the dyes. The fluorescence quenching for the dyes was shown to be quantitatively related to the surface coverage of the dyes on the nanocrystal surfaces. These findings have provided important information for assessing a two-step process involving a rapid adsorption of the dyes on the nanoparticles and a subsequent assembly of the nanoparticles involving a combination of interparticle J-aggregation and hydrophobic interactions of the adsorbed dyes. The results are discussed in terms of the structural effects of the dyes, and the interparticle molecular interactions and reactivities, which provide important physical and chemical insights into the design of dye-nanoparticle structured functional nanomaterials.     

聚酯-聚酯多嵌段共聚物序列结构研究

利用对苯二甲酸乙二酯-己内酯多嵌段共聚物质子谱中各官能团的特征共振吸收峰计算证明两种吸收强度关系式反映了软链段和硬链段中相应官能团的数量关系,从而进一步肯定了所提出的链化学结构,在此基础上又直接利用各种官能团对其质子谱中特征吸收峰的强度贡献,计算得到多嵌段共聚物中软硬链段数,软硬链段平均长度,分子量和硬链段重量百分数的表示式。本文最后一部分用三素组的几率计算方法对多嵌段共聚物的质子谱和~(13)C谱分析讨论,所得有关链结构的数量关系是合理的,进一步证实了质子谱的直接计算法。     

Relevance of analytical pyrolysis studies to biomass conversion

The principles and methods of soft ionization mass spectrometry in combination with pyrolysis of macromolecules are outlined. Essential features of the newly developed techniques are the extension of the recorded mass range and the almost exclusive formation of molecular ions of the pyrolyzates. Using field ionization and field desorption mass spectrometry at low and high mass resolution, with electrical and photographic detection, pyrolysis products of biomass were analyzed for the first time. The results of flash pyrolysis by Curie-point heating and thermally programmed degradation of biopolymers are compared.The main topic is the evaluation of the methodology for time- and temperature-resolved pyrolysis. The thermograms and pyrolysis mass spectra obtained enable the study of pyrolysis reactions and the chemical fingerprinting of complex biological matter. The kinetics for the devolatilization of individual chemical species or classes of compounds can be monitored. Curie-point pyrolysis of biopolymers such as kappa-carrageenan and time-programmed degradation of cellulose and lignin are reported. Furthermore, preliminary investigations of pine wood and coal illustrate the potential of the introduced methods.     

Study of complex mixtures of natural substances by the defocusing and dadi methods. VI. Components of the secretion of the pre-anal gland of some poisonous snakes

By mass-spectrometric methods, cholesterol and docosanoic, heneicosanoic, cicosanoic, octadecanoic, cis-octadec-9-enoic, heptadecanoic, hexadecanoic, and pentadecanoic acids have been identified in the odoriferous secretion of the pre-anal glands of the females and males of the common adder and the saw-scaled viper and in those of females of the common mamushi. It has been established that the chemical compositions of the secretions of these glands of the females of the adder, the viper, and the mamushi and of the males of the adder and of the viper are not identical.     

疏水星形PCL与PCL-b-PEG两亲共聚物的自组装研究

用疏水星形聚合物模拟疏水性药物,研究其与两亲聚合物的自组装,探讨两亲性聚合物包载疏水性药物的机理.用开环聚合合成了5种两亲聚己内酯-聚乙二醇两嵌段共聚物(PCL-b-PEG)和4种疏水星型聚己内酯(star-branched polycaprolactone,SPCL),使用相分离法使PCL-b-PEG与SPCL进行自组装.浊度、SEM、动态光散射(dynamic light scattering,DLS)和FTIR结果表明,PCL-b-PEG与SPCL能够进行自组装,而且PCL-b-PEG中PEG长度和PCL含量对自组装有影响;PCL-b-PEG/SPCL形成的自组装体的粒径与SPCL的臂长、臂数和加入量有关.     

均聚物结晶与熔融化的稳态和亚稳态转变统计理论

基于多重微晶网络结构模型和分子分凝机制建立了高分子晶体的微晶核-和微晶粒-高分子链组模型,推导出了平衡态下高分子预结晶动力学方程,计算出了平衡态下不同尺寸微晶核-和微晶粒-高分子链组的几率分布函数.建立了非稳态下不同尺寸的微晶核-高分子链组的成核演化方程和微晶粒-高分子链组的增长演化方程,求解一般状态下的两个演化方程后,得到了不同时间和不同尺寸的微晶核-和微晶粒-高分子链组的一般密度分布函数.最后根据成核自由能和增长自由能对晶核和晶粒的尺寸大小的依赖性,提出了微晶核-高分子链组和微晶粒-高分子链组存在稳定性的热力学条件和动力学条件,成功地表征为三个特征区(稳态、亚稳态和非稳态).     

Electrical processes upon the evaporation and condensation of water and ice

A mathematical model of electrical processes that take place upon the evaporation of water and sublimation of ice, as well as the condensation growth of water and ice phases from vapor, is proposed. The transfer of the main charge carriers, such as (i) protons and hydroxide ions (in ice, water, and vapor and (ii) orientational defects (in ice and water) is taken into account. Upon the evaporation of water and the sublimation of ice, the first carriers are accumulated before the phase front and cause positive charges in the surface of the water and ice, while the second carriers are depleted (their concentration becomes lower than the thermodynamic value) and impart a negative charge to water and ice. The contribution of protons and hydroxide ions dominates at a low rate of evaporation. In the condensation of vapor and relevant growth of water and ice phases, the polarity of surface charge is opposite to that observed upon evaporation. The values of interfacial current and signs of phase charges upon sublimation, evaporation, and condensation that are predicted in the model comply with experimental data.     

Methodology and procedure of the stoichiographic analysis of solid inorganic substances and materials

The technical and experimental aspects of creating the conditions of differential dissolution in a flow stoichiographic system are discussed; the scheme of the experimental apparatus, stoichiograph, is presented. The construction, operation conditions of the main units of the stoichiograph, and sample treatment issues are considered. The principles of the creation and optimization of the conditions of the dynamic differential dissolution for the analysis of compounds and materials of the known and unknown phase composition are discussed: the composition of solvents and temperature, and the principles of their variation in time, including those in the processes of stoichiographic titration.     

生血宁片中Fe元素的形态分析方法研究

为对生血宁片中Fe元素的形态进行分析,采用了溶剂法、树脂法制备相应供试品溶液,通过微波消解与ICP-MS法测定了生血宁片中Fe元素的含量,并进行了形态研究。结果表明,生血宁片中Fe元素主要以稳定态形式存在,既以有机态又以无机态形式存在,且主要以Fe2+的稳定结合态的形式存在。通过离子树脂筛选出不同价态的铁元素,为价态的分离提供一新方法,且进一步证明了Fe元素的起效形式,同时为中药材或中成药的质量控制及药理研究提供理论参考。