The Effect of the Substrate on the Isomerization of Model Disperse Dyes based on Stilbene

A study of the thermal isomerization of a series of model disperse dyes based on stilbene is described. The results show that the rate of isomerization is influenced by the basicity of the substrate and also by the moisture content. It is suggested that the observed humidity effect is due to an increase in the ease of diffusion of the dye molecules in the substrate.     

Radiolytic Scissioning in Polydimethylsiloxane Networks

Abstract

^γ-radiation induced backbone cleavage in stressed polydimethylsiloxane networks displays the stress relaxation profile expected for random scission of a network possessing a Gaussian distribution of chain lengths. G (scission) as measured by stress relaxation, is found to be dose rate dependent below 0.4 Mr/hr, but does not reveal any atmospheric or temperature effects. The value of G (scission) = 0.7, obtained at a dose rate of 0.4 Mr/hr, is in good agreement with that determined from sol-dose measurements.

The postulated mechanism of scission is based upon a three step reaction scheme involving a siliconium ion produced initially by γ-ray cleavage of an SiO bond. The ion is capable of reacting with a neighbouring chain before it is terminated by an electron or some other neutralizing species. Mathematical analysis of this mechanism leads to the observed dose rate dependence.     

生活垃圾卫生填埋场渗沥液收集导排系统设计概要

在生活垃圾卫生填埋场底部设置合理的渗沥液导排系统,能及时将垃圾堆体中聚集的渗沥液及时导排出去,减少渗沥液外渗污染环境的可能性,并为污染物质的降解提供更为合适的环境。鉴于此,文章简要介绍了渗沥液导排系统的功能及构造、各组成部分材料的选择原则及设计中可采取的理论计算方法。     

Rheological Properties of Solid Disperse Systems

A set of equations is suggested for the analysis of the pressure-induced stress and strain in solid disperse materials. The set takes into account the rheological and physicochemical properties of the compacted material and the design parameters of the compaction process.     

Separation of Concentrated Solid–Liquid Systems

Experimental results on mass-transfer coefficients for adiabatic distillation, evaporation of pure liq-uids, and desorption of oxygen from water are reported. A procedure has been designed for calculating thekinetics of binary distillation including the superimposed effects of surface tension, the difference in the tem-peratures of phases, and the curvature of an equilibrium line. The findings of the calculation agree with exper-imental data resulting from laboratory and pilot-scale kinetic tests.     

Separation of Concentrated Solid–Liquid Systems

The effect of the interaction between particles of the settling solid phase on the separation efficiency in hindered settling of a suspension is analyzed.     

异构脱蜡产品质量的控制

以异构脱蜡装置实际生产情况为例,讨论了操作条件、产品调合及进料性质对加氢基础油产品质量的影响,力求精细调控以确保生产更优质的润滑油基础油及相应的副产品。     

异构化催化剂的性能对比

惠州炼油芳烃联合装置是目前国内同类单系列规模最大的装置。文章介绍了该装置异构化催化剂EM-4500催化剂应用情况,并与另一种异构催化剂进行了对比,分析了EM-4500催化剂对吸附进料的影响。     

Radiolytic Studies of the Cumyloxyl Radical in Aqueous Solutions

Formation and reactions of the cumyloxyl radical in aqueous solutions were studied by steady-state and pulse radiolytic techniques. Cumene hydroperoxide reacts with e⁻_aq (k = 4.4 × 10⁹ M⁻¹s⁻¹) to yield the cumyloxyl radical. The spectrum recorded after the pulse indicates formation of a species absorbing at 250 nm. This product was identified as acetophenone, which is formed by the fragmentation of the cumyloxyl radical. By comparison of the pseudo-first-order rates of e⁻_aq decay at 600 nm with the rate of production of acetophenone at 245 nm at increasing concentrations of cumene hydroperoxide, it was possible to derive a rate constant of 1.0 × 10⁷ s⁻¹ for the cleavage of cumyloxyl to acetophenone and methyl radical. This value is higher than that measured previously in organic solvents (1 × 10⁶ s⁻¹), as expected. HPLC analysis of the radiation products acetophenone and cumyl alcohol permitted determination of rate constants for hydrogen abstraction by the cumyloxyl radical, in competition with the fragmentation. The rate constants for H abstraction from i-PrOH, EtOH, and MeOH by CmO were found to be 9.9 × 10⁶, 3.8 × 10⁶, and 8.5 × 10⁵ M⁻¹ s⁻¹, respectively.     

Measurement and Correlation of Solid Drugs Solubility in Supercritical Systems

A dynamic experimental set-up was utilized to measure ibuprofen solubility in supercritical CO2 at the pressure range of 8-13 MPa and the temperatures of 308, 313 and 318 K. Mole fraction values varied from 0.015＆#215;10^-3 to 3.261＆#215;10^-3 and correlated by using seven different semi empirical equations of state （Bartle, Modi-fied Bartle, Mendez-Teja, Modified Mendez-Teja, Kumar-Johnson, Sung-shim and Gordillo） as well as seven cubic equations of state （van der Waals, Redlich-Kwong, Soave-Redlich-Kwong, Peng-Robinson, Stryjek-Vera, Patel-Teja-Valderana and Pazuki）. Single and twin-parametric van der Walls mixing rules （vdW1, vdW2） were ap-plied in order to estimate the supercritical solution properties. The physicochemical properties were also obtained using Joback, Lydersen and Ambrose methods. Absolute average relatives deviation （AARD） were calculated and compared for all the correlating systems. Results showed that among the cubic equations of state （EOSs） the Pazuki equation （AARD=19.85% using vdW1 and AARD=8.79% using vdW2） and SRK equation （AARD=19.20%using vdW1 and AARD=10.03%using vdW2） predicted the ibuprofen solubility in supercritical CO2 with the least error in comparison to the others. Among the semi-empirical EOSs the most desirable deviation （AARD〈10%） was obtained by using Modified Bartle and Modified Mendez-Teja equations in all the studied temperatures.     

含固体物系相平衡研究的现状和进展

本文介绍了含固体物系相平衡研究的意义、现状和最新动向。     

Radiolytic and hydrolytic degradation of the hydrophilic diglycolamides

The stability of different hydrophilic diglycolamides against acid degradation and radiolysis was studied. Tetraethyldiglycolamide (TEDGA) was found to undergo degradation in nitric acid at high reaction rates at elevated temperatures with a maximum of a ~8% decrease per hour at 65°C in 4 mol L^–1 HNO₃. The radiolysis was studied for tetramethyldiglycolamide (TMDGA), TEDGA, methyl-tetraethyldiglycolamide (Me-TEDGA), and dimethyl-tetraethyldiglycolamide (Me₂-TEDGA). The degradation rates decreased with increasing molecular weight, following the trend TMDGA > TEDGA > Me-TEDGA ≥ Me₂-TEDGA. Degradation products were identified by mass spectrometric techniques and were found to be comparable to those previously reported for the radiolysis of lipophilic diglycolamides in dodecane. Significant insight into the degradation mechanism in water was gained using pulse radiolysis experiments. The ^?OH radical was identified as the most important reactive species and predominant mechanism of radical reaction is one of electron transfer rather than H-atom abstraction.     

Model of Impact Initiation of Composite Explosive Solid Systems

A model of mechanical initiation of solid explosives, applicable for analysis of sensitivity of individual substances and composite explosives, is developed. The model includes a system of equations of work softening of a high explosive charge under an impact, resulting dissipative heating, and heat release due to chemical reactions between the components of the explosive mixture. The critical parameters and reaction kinetics were numerically calculated for initiation of charges consisting of a mixture of ammonium perchlorate and polymethylmethacrylate. The results are compared to experimental data on sensitivity of this mixture to the impact. Key words: high explosive, impact, explosion, impact sensitivity.     

Influence of Aqueous/Solid Interactions on Organic Droplet Shape in Liquid/Liquid/Solid Systems

Abstract

We report the results of a theoretical study of the complex phenomena relating to contact angle changes for hexadecane droplets on a gold surface in aqueous ionic surfactant solutions. This approach integrates changes in the nature of the solid absorbed surfactant phase through use of the quasi‐chemical approximation. This improvement is accomplished with minimal additional model complexity and provides evidence for changes in adsorbate structure as aqueous surfactant concentration is increased. The theoretical predictions are tested using previously published data regarding the contact angle of hexadecane on gold in sodium dodecyl sulfate and cetyl‐trimethylammonium bromide solutions.     

角黄素的异构化研究

在角黄素工业化生产中,主要有天然提取法,微生物发酵法,化学合成法。目前国内研究较多的是化学合成,通过化学合成的角黄素反式含量并不高,通常还需要经过异构化及重结晶提高产品的反式含量。本文结合已有报道的方法,通过实验的方法对比各种异构方法所得的角黄素反式含量,为其实现工业化生产和进一步的研究提供参考。     

芪类糖苷化合物合成研究

根据丹参水溶性成分中丹参酸B的苯并呋哺结构,合成了各种芪类化合物,而羟基芪类化合物理化性质上的缺陷限制了临床试用,设计对其进行糖苷化修饰。以丹酚酸类化合物为先导,设计合成了两个芪类化合物及其葡萄搪、半乳糖和乳糖搪苷类衍生物。     

Influence of Work of Adhesion on Dissolution Rate in Binary Solid Systems

In powder mixtures, the interactions between the particles are determined by the forces of adhesion and cohesion. The size and the specific surface area of the particles are also determinative factors in the interparticle interactions.

The aim of the present work was to investigate the surface properties of different physical mixtures of meloxicam (ME) and find a possible relation between surface properties and dissolution of physical mixtures. The contact angle, surface free energy, polarity, work of adhesion, and work of cohesion of the drug, the carrier, and their physical mixtures were calculated.

ME samples with different particle sizes were investigated without the carrier and in two different ratios with mannitol. A smaller (micronized) particle size without the carrier did not improve the dissolution of the drug. However, with the ideal particle size of the drug (ME2) and the ideal ratio of ME and mannitol (1:10), total dissolution of drug was achieved. In this case, mannitol functioned as a core covered with a monolayer of ME particles. The contact angle, the surface free energy, the polarity, and the work of adhesion can be used as critical parameters to characterization of a powder mixtures and determination of optimum dissolution profile.     

C8芳烃异构化反应温升分析

通过对C8芳烃异构化反应机理的分析．异构化反应温升与反应产物中非芳烃增量密切相关,是异构化反应温度和压力共同作用的宏观表现．能直接反映异构化反应情况。对减少C8芳烃加工损失,生产负荷调整,保证对二甲苯质量要重指导作用。     

四氢双环戊二烯异构化过程的溶剂效应

采用无水AlCl3为催化剂,考察了使用不同溶剂对桥式四氢双环戊二烯(endo-THDCPD)异构化为挂式四氢双环戊二烯(exo-THDCPD)过程中反应速率、反应转化率、收率、选择性及杂质生成量的影响。采用气相色谱对反应原料、产物及杂质进行定量分析。结果表明溶剂的使用对于异构化反应有显著的影响：甲苯作溶剂时对反应有很大的抑制作用,而1,2-二氯乙烷作溶剂时,则有明显改善,在催化剂浓度3％(wt)、最佳反应温度60℃条件下,反应结果：转化率97．73%、收率97.66％、选择性99．93％。同无溶剂反应时相比,最佳反应温度降低、产物中金刚烷生成量减少同时无焦油产生。实验中以原料endo-THDCPD为对象考察1,2-二氯乙烷作溶剂时的反应动力学,得到了动力学方程。