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。     

Contributions to the Chemistry of the Binary Compounds of the Transition Elements

Phase and structural relationships of the sulfur, selenium, and tellurium compounds of the 4d and 5d transition elements of groups IV to VII of the periodic system are discussed. Homologous elements behave very similarly with respect to the chalcogens, and this is particularly the case for niobium and tantalum, and for molybdenum and tungsten. However, zirconium, niobium, and molybdenum have a greater tendency towards formation of chalcogen-poor phases than their homologues hafnium, tantalum, and tungsten. Subchalcogenides are known only for zirconium and niobium. The number of phases and the tendency towards formation of solid solutions are considerably smaller among the tellurides than among the sulfides and selenides. The crystal structures of the telluride phases also differ from those of the sulfide and selenide phases of analogous composition. In addition, a review of the phase and structural relationships of the arsenic and antimony compounds of the 4d and 5d transition elements of groups V to VII is given.     

Charge number effect on the miscibility of inorganic salt and surfactant in adsorbed film and micelle: inorganic salt-octyl methyl sulfoxide mixtures

Adsorption and micelle formation of a surfactant in the presence of inorganic salts with different charge numbers of cations were investigated from the viewpoint of mixed adsorption and micelle formation of salt and surfactant. Surface tension of aqueous solutions of the mixtures of octyl methyl sulfoxide (OMS) with calcium chloride and lanthanum chloride was measured as a function of the total molality of the mixture and the mole fraction of OMS in the mixture at 298.15 K under atmospheric pressure. Composition of the adsorbed film and micelle was numerically evaluated from the dependence of the total molality at a given surface tension and the mixture CMC on the bulk composition to draw phase diagrams of adsorption and micelle formation. Judging from the phase diagrams together with the ones of the sodium chloride system, miscibility of inorganic salt and OMS in the adsorbed film and micelle increases with an increase in the charge number of inorganic cation, which is attributable to the attractive interaction between inorganic cation and the polar head group of OMS molecule in the adsorbed film and micelle.     

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。     

Virtual screening of organic molecule databases. Design of focused libraries of potential ligands of NMDA and AMPA receptors

A system of virtual screening of organic molecule databases is designed, which permits preprocessing of databases, molecular docking to a three-dimensional model of receptor, and post-processing of the results obtained. Using this screening system, it is possible to reproduce positions of the known ligands in the glutamate sites of the NMDA and AMPA receptors and in the glycine site of the NMDA receptor, to substantially enrich the database with potentially active compounds, and to distinguish between the agonistic and antagonistic character of the action of these compounds in the case of docking to the open and closed forms of the binding sites. Based on the results of screening of a database of low-molecular-weight organic compounds (total of 135,000 structures) using models of the open and closed forms of the glutamate and glycine sites of the NMDA receptor and of the glutamate site of the AMPA receptor, focused libraries of potential agonists and antagonists of these sites were designed.     

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.     

Phenolic potential of Tannat, Cabernet-Sauvignon and Merlot grapes and their correspondence with wine composition

The phenolic potential of Tannat, Cabernet-Sauvignon and Merlot grapes was evaluated in 2001 and 2002 and its correspondence with the colour and composition of the respective wines was established. Three vineyards of each variety, situated in the south of Uruguay were considered. Two samples of each vineyard were taken at the moment of the harvest. Phenolic richness, extractable anthocyanins contents and total potential in anthocyanins of the grapes were estimated. Two fermentations on skins were carried out for each vineyard using 50 kg of grape in each one. The anthocyanic and total polyphenols contents of the musts were analysed every 24 h, and skins extractions were carried out in parallel in the laboratory. The duration of the maceration for each variety was decided in function of the analytical results in the grapes, musts and skins extractions. Wines were analysed 2 months after the alcoholic fermentation, determining its phenolic composition and colour. Tannat grapes presented anthocyanic and total polyphenols contents significantly higher in both years. Therefore, wines from this variety presented colour intensity and phenolic contents statistically higher than Cabernet-Sauvignon and Merlot. The correlations between the phenolic contents of the grapes, skins, musts and wines were very significant. Colour intensity and phenolic contents of the wines were highly correlated with the total polyphenols of the grapes and with anthocyanins of the grapes, skins, musts and wines. The estimate of the phenolic potential of the grapes and the extractability of the pigments allows to manage more adequately the fermentation on skins and is an interesting tool to predict the colour and the composition of the wines.     

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.     

Measurement of protein-DNA interaction parameters by electrophoresis mobility shift assay

Native gel electrophoresis (mobility shift) assays may be used to obtain quantitative information about the site distribution, equilibria and kinetics of protein-DNA interactions. These applications depend on the ability of the electrophoretic system to resolve the reaction components, and on their stabilities during the separation process. Factors which affect the lifetimes and mobilities of protein-DNA complexes during electrophoresis include reaction and electrophoresis buffer composition, pH, and ionic strength; the presence of low molecular weight effectors and enzymatic substrates; the nature and concentration of the gel matrix; the temperature; the molecular weights of protein and DNA; the stoichiometric ratios of their complexes; and the possibility of conformational and configurational isomerization of reaction components. We discuss how these factors influence the acquisition of quantitative data from electrophoretic patterns and band intensities, and present formulas for the estimation of equilibrium constants and rate constants for prototypical DNA-protein interactions.     

视网膜脱离后PVR的形成与氧自由基和锌、铜关系的研究

为探讨氧自由基和锌、铜在视网膜脱离后增殖性玻璃体视网膜病变 (PVR)中的作用 ,收集了 48例视网膜脱离患者视网膜下液 (SRF) ,利用紫外分光光度计测定了SRF中LPO的含量和SOD的活性 ,用原子吸收光谱法测定了Zn、Cu的含量。结果表明 ,随着PVR程度及玻璃体浑浊的加重、病程的延长 ,LPO含量增加 ,SOD活性明显下降 ,P <0 0 5 ,差异有统计学意义。提示SRF中LPO、Zn、Cu含量及SOD活性的改变与视网膜脱离后PVR的发生、发展有密切关系。     

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。     

Physico-chemical factors governing partition behaviour of solutes and particles in aqueous polymeric biphasic systems. III. Features of solutes and biological particles detected by the partition technique

The partition behaviour of human serum albumin and oxyhaemoglobin and several amino acids and small peptides was studied in the aqueous Ficoll-dextran biphasic system as a function of the ionic composition and pH. The partition coefficients of the solutes were expressed in terms of the equivalent number of CH2 groups, nCH2, and the equivalent number of carboxyl groups, m. The physical meaning of these two parameters and of the relationships found between them and pH for the proteins examined are discussed. A correlation was established between the difference in the relative hydrophobicities of the individual phases of various water-organic solvent systems and the interfacial tension, gamma 12, of the systems. It is argued that a relation of a similar type exists for the aqueous polymeric biphasic systems. The possibility of estimating the relative intensity of Van der Waals and hydration interactions of a solute and particle surface by examination of their partitioning in a biphasic system calibrated for the hydrophobic and hydration properties of the phases is discussed.     

纳米粒子的精准组装

纳米材料由于其独特的光、电、磁、力学等性质,成为了构建功能材料与器件的理想基元。实现纳米粒子的精确组装,是探究粒子之间的耦合聚集性质和制备宏观功能器件的基础。但是由于纳米粒子的小尺寸以及在溶液中运动的随机性与复杂性,精准控制纳米粒子组装体的形貌以及在空间中的相对位置仍存在巨大挑战。为了将纳米粒子组装成理想的有序结构,许多控制粒子组装的策略与方法得到发展。本文首先概述了纳米粒子自组装的控制方法与典型形貌,着重分析了影响粒子精准排布的因素与控制方法,并对纳米粒子及其组装体的光学性质与器件应用的最新研究进展进行了讨论,最后对目前纳米粒子精准组装所面临的挑战以及未来发展的方向进行了展望。     

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.     

Bond energies and the enthalpies of formation of mono- and polyradicals in nitroalkanes 2. Nitro derivatives of ethane and propane

Based on the experimental results and the published data, the enthalpies of formation of ethane and propane nitro derivatives were obtained for both the standard state and gas phase. The bond dissociation energies of the ethane and propane nitro derivatives were calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. The calculated values were compared with the kinetic data on thermal decomposition. The bond dissociation energies in radicals of the ethane and propane nitro derivatives were also calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. Regularities of changes in the bond dissociation energies of the ethane and propane nitro derivatives and their radicals were established.     

The wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solution of two cationic surfactants mixture

Advancing contact angle (theta) measurements were carried out for aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) mixtures on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA). The obtained results indicate that the wettability of PTFE and PMMA by aqueous solutions of CTAB and CPyB mixtures depends on the composition and concentration of the mixture; however, synergism in the wettability does not exist. In the range of low concentrations of aqueous solution mixtures there is a linear dependence between the contact angle and composition of the mixtures, but at a concentration close to CMC a deviation from linear dependence is observed. In contrast to Zisman, there is no linear dependence between costheta and the surface tension of aqueous solution of CTAB and CPyB mixtures, but a linear dependence exists between the adhesional and surface tension, and these lines have a slope -1 and -0.34 for PTFE and PMMA, respectively, which suggests that adsorption of CTAB and CPyB mixtures at water-air and PTFE-water is the same, and the orientation of the CTAB and CPyB molecules at both interfaces in the saturated monolayer should also be the same. Adsorption of these mixtures at water-air interface is considerably higher than at PMMA-water interface, and CTAB and CPyB molecules should be parallelly oriented to PMMA surface in the saturated monolayer. Extrapolation of the straight lines to the points corresponding to the surface tension of aqueous solution, which completely spreads over the PTFE and PMMA surface, gives a critical surface tension of wetting equal to 23.44 and 33.13 mN/m, respectively. The value of 23.44 mN/m is higher than that of the surface tension of PTFE, but the value of 33.13 is lower than that of Lifshitz-van der Waals components of PMMA surface tension. On the basis of the critical surface tension, the surface tension of PTFE and PMMA, the Young equation, and thermodynamic analysis of the adhesion work of aqueous solution of surfactant to polymer surface, it was found that for PTFE and PMMA the changes of the contact angle of aqueous solution of two cationic surfactants mixtures on their surfaces as a function of the solution concentration resulted only from the decrease of the polar component of the solution surface tension.     

Effects of Black Liquor,Petroleum Sulfonate And Poly Acrylamide On The Transport Behavior of Nonionic Surfactants From Water Phase To Oil Phase

We used the radiosoptopic tracer and HPLC to measure the concentration of nonionic surfactants, petroleum sulfonate and polyacrylamide respectively,and studied the effect of petroleum sulfonate.polyacrylamide, black liquor, and black liquor system on distribution and diffusion of nonionic surfactants in the system of toluene and water, and tbe effect of nonionic surfactants on the distribution of petroleum sulfonate and polyacrylamide with different temperature. It was found that petroleum sulfonate mainly existed in the oil phase.polyacrylamide was quite the contrary, the existence of black liquor system and its components decreased both diffusion rates and partition coefficients of nonionic surfactants and the distribution of ic surfactants and the distribution of nonionic surfactants was different with the variation of HLB and temperature.     

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     

Structural Chemistry of 1-Hydroxyethylidenediphosphonic Acid Complexes

The structural features of complexes of 1-hydroxyethylidenediphosphonic acid (HEDP) with different metals (geometric isomerism, dentate numbers and the mode of coordination of organophosphorus ligand, the structural type and degree of oligomerization, regular distortions of the coordination polyhedron, and the mutual influence of the ligands) are considered. The dependences of the complex structures and of the degree of deprotonation of the HEDP ligands on the synthesis conditions (solution pH and metal : HEDP ratio), on the nature of the metal and the outer-sphere cation, on the composition of the hydrate sphere, and on the availability of the accompanying ligands are also established.