基于定量结构-性质关系预测含水二元共沸物的共沸温度与组成

以125种含水二元共沸物为研究对象,基于定量结构-性质关系,对该类共沸物在常压下的共沸温度及组成进行了预测研究,分别建立了多个预测模型。首先,利用HyperChem 8.0软件绘制了纯组分的三维分子结构,并利用分子力学方法和量子力学半经验方法对分子结构进行优化;然后,利用Materials Studio 8.0软件计算纯物质的分子描述符;其次,利用遗传算法分别筛选出与共沸温度及组成最为密切的特征描述符;再运用多元线性回归方法建立了6个共沸温度预测模型及5个共沸组成预测模型,并对模型的稳定性、拟合能力和预测能力进行对比分析;最后,对最适宜模型分别进行内部验证、外部验证、应用域分析、与文献中同类模型及UNIFAC基团贡献法进行对比。结果表明：最适宜共沸温度/组成预测模型分别是利用8/5个特征描述符所建立的模型;其复相关系数,调整复相关系数,均方根误差,平均绝对误差,留一法交叉验证系数和外部验证系数分别为0.960 6/0.997 0、0.957 2/0.996 9、2.940 0/0.016 1、1.890 0/0.010 4、0.947 5/0.995 7和0.943 9/0.997 6,且模型的稳定性、预测能力和泛化能力均优同类模型。     

含卤代烃二元共沸物共沸特性的QSPR模型

为了安全、经济地获取含卤代烃二元共沸物共沸特性数据,提出基于定量结构-性质关系(QSPR)原理预测共沸特性.选用239种含卤代烃的二元共沸物作为研究对象,利用遗传函数逼近算法(GFA)筛选分子描述符并分别构建共沸温度和共沸组成模型.根据拟合能力挑选最佳模型,然后采用内部验证、外部验证、y-随机验证及应用域分析对最佳模型...     

碳酸二甲酯-甲醇二元共沸物的分离方法

讨论了分离碳酸二甲酸－甲醇二元共沸物的各种方法，重点介绍了最有工业化前景的萃取精馏法，并对萃取剂的选择作了较为详细的讨论。     

预测共沸物的同伦-牛顿联合方法

为了更有效地预测共沸系统,文内提出了同伦-牛顿联合算法,首先利用具有全局收敛性的同伦算法产生较好的初值,然后利用收敛速度快的牛顿算法求解共沸方程。应用联合方法预测了多个二元和三元非理想性物系的共沸点,结果表明,同伦-牛顿联合方法有较大的收敛范围,较高的迭代过程稳定性,较快的收敛速度。     

基于定量构效关系的药物检测研究

定量构效关系以数学和统计学手段建立起化合物的化学结构与生物活性之间的定量关系。QSAR在化学与生物学之间架设起了一道桥梁。在探讨了几种定量构效关系方法的基础上,通过水杨酸镁的质量检测实验进行了应用分析,结果表明引入定量构效关系的实验分析结果可以起到补充、取长补短的效果,为建立更好的检测机制提供参考。这一研究对于化合物的分子结构性质数据的发展有一定的参考价值。     

丙酮-甲醇二元共沸物分离技术的现状

综述了目前较为常用的几种丙酮-甲醇共沸物分离方法,重点讲述了盐效精馏、萃取精馏、加盐萃取精馏和变压精馏工艺。现阶段的丙酮-甲醇共沸物分离技术较为成熟,未来应在现有基础上多做创新。在溶剂选择、回收和成本方面进行综合比较,为读者提供了选择分离共沸物方法的思路。     

甲醇-碳酸二甲酯二元共沸物的分离

分别用共沸精馏法和萃取精馏法对甲醇一碳酸二甲酯（DMC）二元共沸体系进行了分离,通过正交实验分别得到了最佳分离工艺条件。实验结果表明,共沸精馏法的最佳分离工艺条件：共沸剂正己烷用量为总质量（共沸剂＋甲醇）的76％,回流比控制在3：1,馏出速率为6mL／min;萃取精馏法的分离最佳工艺条件：以糠醛为萃取剂,回流比控制在3：1,萃取剂滴加速率为3mL／min,萃取剂配比为4：1。并分别从装置和纯度方面对两种方法进行比较,结果表明萃取精馏法占优。     

碳酸二甲酯的合成及其共沸物的分离

介绍了目前国内外碳酸二甲酯的合成及碳酸二甲酯—甲醇二元共沸物的分离方法，并指出了各种方法的优缺点。甲醇气相氧化碳基化法合成碳酸二甲酯具有发展潜力，对于甲醇—碳酸二甲酯二元共沸物的分离建议使用物料自身压力加压精馏法。     

应用定量构效关系（QSARs）预测有机化学品的理化参数

随着工农业生产的发展,化学品生产的种类和数量与日俱增。据统计全世界每天使用的合成化学品达7万余种,这些化学品在生产、运输、再加工、使用等过程中不可避免地要进入环境,造成严重的化学污染。1982年“经济合作与开发组织”理事会规定了化学品投产前最基本的安全评价项目(MPO),全面对化学品进行评价以确定是否可以     

碳酸二甲酯-甲醇二元共沸物的分离方法

论述了分离碳酸二甲酯-甲醇二元共沸物的各种方法,重点介绍了萃取精馏法,并对萃取剂的选择作了较为详细的报道.     

QSPR modeling of azeotropic temperatures and compositions for binary azeotropes containing lower alcohols using a genetic function approximation

Binary azeotropes, which contain two chemicals with a relative volatility of 1, are very common in the chemical industry. Understanding azeotropes is essential for effectively separating binary azeotropes containing lower alcohols. Experimental techniques and ab initio approaches can produce accurate results; however, these two processes are time consuming and labor intensive. Although thermodynamic equations such as UNIFAC are widely used, experimental values are required, and it is difficult to choose the best groups to represent a complex system. Because of their high efficiency and fast calculation speed, quantitative structure–property relationship(QSPR) tools were used in this work to predict the azeotropic temperatures and compositions of binary azeotropes containing lower alcohols. The QSPR models for 64 binary azeotropes based on centroid approximation and weighted-contribution-factor approximation were established using the genetic function approximation(GFA) procedure in Materials Studio software, and a leave-one-out cross-validation procedure was conducted.External tests of an additional 16 azeotropes were also investigated, and high determination coefficient values were obtained. The best QSPR models were explained in terms of the molecular structure of the azeotropes,and good predictive ability was obtained within acceptable prediction error levels.     

Catalyst-free growth of needle-shaped carbon filaments at low temperature in a near-critical binary fluid

Ultraviolet laser irradiation into a mixture of supercritical carbon dioxide and benzene at 266 nm wavelength in an electric field of 8 kV/cm resulted in production of needle-shaped carbon filaments at low temperature, observed T_min being 33.5 °C. Structures could only be produced under near- and supercritical conditions, and did not appear in sub-critical conditions, i.e., in the gas-liquid coexistence state. The filaments are straight, with maximum observed length approximately 20 μm, and are 0.5-1 μm in diameter at the base, and approximately 300 nm at the tip. They do not bundle together, but grow individually, aligned radially from the sharp edges of the silicon substrates attached to the electrodes. No catalyst particles were found inside, at the base or the tip of the filaments. We suggest that the primary facilitator in the filament growth is the local electric field strength, which corresponds to the substrate morphology, possibly further assisted by the unusual properties of the critical fluid phase, such as increased miscibility and high isothermal compressibility. The structures were observed by scanning electron microscopy, and further characterized by energy dispersive X-ray spectroscopy and visible and ultraviolet Raman spectroscopy.     

基于神经网络的定量结构-性质相关性研究预测有机物燃烧特性

介绍了神经网络及定量结构-性质相关性(QSPR)研究基本原理,综述了两者相结合在闪点、自燃点、爆炸极限等化学物质燃烧特性预测中的应用和进展.分别对各性质不同预测模型的优缺点及适用范围进行了评述.在此基础上对神经网络与线性回归方法的比较、神经网络技术的发展等进行了探讨,对实验样本设计、分子描述符选择及模型验证等的研究现状和发展趋势进行了讨论.展望了QSPR在安全研究领域的应用前景.     

超临界CO2二元系统相平衡的数值模拟

应用微扰理论,借助微扰状态方程,对超临界CO2 系统相平衡进行了模拟。编制了求解程序,介绍了状态方程中各参数的确定方法和程序模块的设计思想。针对超临界CO2 /非极性体系、超临界CO2 /极性体系,在不同温度、压力条件下的气液相平衡进行了计算,将计算结果与实验结果进行了比较,结果表明:微扰状态方程适合模拟超高压下的CO2 二元体系的相平衡。     

Study on low carbon containing MgO-C refractory: Use of nano carbon

Development of nano carbon containing magnesia carbon refractories has been studied to reduce the total carbon content, thereby reducing the heat loss from the metallurgical process and producing more eco-friendly refractories. The carbon contamination from refractory to liquid metal will be minimized using low amount of nano carbon. Different percentages of nano carbon are used in combination with graphite as carbon source and the total carbon is maintained below the half of the total carbon of the conventional MgO-C refractories. The compositions were processed as per the conventional manufacturing techniques and the properties were evaluated and compared against the conventional refractory prepared under exactly similar conditions. Also elemental mapping of carbon was done to study the distribution of the nano carbon in the matrix.     

Easy synthesis of ordered mesoporous carbon containing nickel nanoparticles by a low temperature hydrothermal method

Ordered mesoporous carbons (OMCs) with embedded metallic nickel (Ni) nanoparticles have been directly synthesized by a simple and low temperature (50 °C) hydrothermal method. The synthesis involved the use of a triblock copolymer Pluronic F127 as the mesostructure directing agent, resorcinol (R) and formaldehyde (F) as carbon precursors, and Ni(NO₃)₂·6H₂O as nickel source. It consisted in the self-assembly of F127, Ni²⁺ salt and RF polymer in an acidic medium and further carbonization, where the Ni²⁺ was captured by the network of F127/RF and further reduced into metallic Ni nanoparticles. The resultant Ni/carbon materials were characterised by X-ray diffraction, thermogravimetric analysis, transmission electron microscopy and nitrogen sorption. Ni/carbon materials with a highly ordered mesostructure were obtained using equal moles of resorcinol and formaldehyde molar ratio (R/F = 1/1), whereas an excess amount of formaldehyde (R/F = 1/2) was found to not form an ordered carbon structure. The results showed that nickel particles, with sizes of ∼10–50 nm, were homogeneously dispersed in the carbon matrices, while the pore mesostructure remained intact. The homogeneous Ni/carbon composites synthesized by this easy hydrothermal route have been demonstrated to be effective molecular adsorbents for magnetic separation.     

On the dynamics of distillation processes-V: The topology of the boiling temperature surface and its relation to azeotropic distillation

It is shown that ridges and valleys in the boiling temperature surface do not coincide with azeotropic distillation region boundaries. Thus, the prevai and valleys is shown to be false. This allows for a greater flexibility in design and a better understanding of the behavior of azeotropic distillation     

Ultra‐low temperature sintering microwave dielectric ceramics based on Ag2O–MoO3 binary system

The Ag₂Mo₂O₇ and Ag₆Mo₁₀O₃₃ ceramics for ultra‐low temperature co‐fired ceramic application were prepared by the solid‐state reaction route. The optimized densification temperatures of Ag₂Mo₂O₇ and Ag₆Mo₁₀O₃₃ are 460°C and 500°C, respectively. The phase structures and microstructures of these ceramics were systematically studied. The Ag₂Mo₂O₇ ceramic sintered at 460°C/4 h exhibits excellent microwave dielectric properties with ε_r=13.3, Q×f=25 300 GHz and τ_f=?142 ppm/°C at 9.25 GHz. The Ag₆Mo₁₀O₃₃ ceramic sintered at 500°C/4 h shows the microwave dielectric properties with ε_r=14.0, Q×f=8500 GHz and τ_f=?50 ppm/°C at 9.00 GHz. Moreover, when Ag₂Mo₂O₇ samples are sintered at ultra‐low sintering temperatures of 420°C‐490°C, the Q×f values of them are all above 20 000 GHz. Besides, the Ag₂Mo₂O₇ ceramic does not react with silver powder or aluminum powder. The variation of relative permittivity, resonant frequency, and Q×f values as a function of operating temperature has been also studied. All the results indicate that the Ag₂Mo₂O₇ ceramic is a good candidate for ultra‐low temperature co‐fired microwave devices.     

The effect of activated carbon surface moisture on low temperature mercury adsorption

Experiments with elemental mercury (Hg⁰) adsorption by activated carbons were performed using a bench-scale fixed-bed reactor at room temperature (27°C) to determine the role of surface moisture in capturing Hg⁰. A bituminous-coal-based activated carbon (BPL) and an activated carbon fiber (ACN) were tested for Hg⁰ adsorption capacity. About 75-85% reduction in Hg⁰ adsorption was observed when both carbon samples’ moisture (∼2 wt.% as received) was removed by heating at 110°C prior to the Hg⁰ adsorption experiments. These observations strongly suggest that the moisture contained in activated carbons plays a critical role in retaining Hg⁰ under these conditions. The common effect of moisture on Hg⁰ adsorption was observed for both carbons, despite extreme differences in their ash contents. Temperature programmed desorption (TPD) experiments performed on the two carbons after adsorption indicated that chemisorption of Hg⁰ is a dominant process over physisorption for the moisture-containing samples. The nature of the mercury bonding on carbon surface was examined by X-ray absorption fine structure (XAFS) spectroscopy. XAFS results provide evidence that mercury bonding on the carbon surface was associated with oxygen. The results of this study suggest that surface oxygen complexes provide the active sites for mercury bonding. The adsorbed H₂O is closely associated with surface oxygen complexes and the removal of the H₂O from the carbon surface by low-temperature heat treatment reduces the number of active sites that can chemically bond Hg⁰ or eliminates the reactive surface conditions that favor Hg⁰ adsorption.