稀土催化体系催化PET固相缩聚的研究

研究了稀土催化体系对聚对苯二甲酸乙二酯固相缩聚反应的催化效果及对所得高分子量聚酯切片性能的影响,发现稀土催化体系可明显提高聚酯固相缩聚的反应速率,稀土催化体系对聚酯固相缩聚反应的催化活性明显高于传统催化体系,其中单一稀土催化体系与混合稀土催化体系在较低温度下具有相近的催化活性,而在较高温度下单一稀土催化体系的催化活性较高;加入稳定剂,不影响稀土催化的固相缩聚反应速率,稀土催化固相缩聚得到的PET样品具有较高的结晶度和较大的晶粒尺寸,其中单一稀土催化所得样品的晶粒尺寸最大,相应地,单一稀土催化的固相缩聚反应活化能也最大;稀土催化体系催化聚酯固相缩聚反应时添加适当稳定剂,可获得与采用传统催化体系得到的PET切片相近的热稳定性。     

Discrete model of random-pore aging by wall relief softening

A new (discrete) model for random-pore aging in isochoric system with wall relief softening is proposed. The main criterion of the evolution of such system is the reduction of solid-gas interface area with time. The model allows simulations of the evolution of aging porous system with time, and estimations of free energy of the system. Equations of the model are used for simulations of the evolution of porous system with time. It is shown that the proposed model is effective for theoretical studies of processes of pore transformations by aging.     

A sensitivity analysis of the smith predictor controller

The sensitivity of the Smith predictor controller to variations in system parameters is analyzed. The parameters considered are system gain, time constant, and delay or dead time. Both simulated and experimental results are discussed. First- and second-order models are studied. For the first-order model, a proportional plus integral control is used with the Smith predictor. A proportional plus integral plus derivative control is used with the Smith predictor for the second-order system. The controller is implemented digitally. An application of the Smith predictor with a model of the system obtained by a nonlinear least-squares parameter identification method is demonstrated on an experimental system.     

Esterification of Octanoic Acid with Octanol in Microemulsion and Emulsion System

The esterification of octanoic acid with octanol in microemulsion and emulsion system is studied. In the presence of 5–10% dodecylbenzene-sulfonic acid (DBSA), which is a surfactant-type catalyst, high conversion of esterification can be given both in microemulsion and in emulsion system. Compared with emulsion system, single-phase microemulsion is a more effective reaction system for esterification, with the advantages of comparatively little influence by the amount of water, no need of hard stirring, and stable state when laid long. The esterification of other fatty acids and alcohols in this reaction system were also accomplished in favorable conversion.     

用于煤制天然气的气化-热解耦合系统模拟研究及能量分析

大规模煤制天然气系统中气流床气化是一种重要且富吸引力的技术。对一种气流床气化-热解耦合系统进行了研究。该系统中气化炉分为两段:主要进行煤焦气化的气化段以及主要发生煤热解的热解段。采用流程模拟方法建立了耦合系统模型并与煤气化废锅系统进行了比较。同时,考察了操作条件对耦合系统气化性能的影响,提出了优化的操作条件。结果显示,气化温度1400 ℃时,耦合系统优化的蒸汽煤比为250~300 kg(steam)·t^-1(dry coal)。耦合系统的冷煤气效率为88.18%,高于气化废锅系统(84.14%),且其消耗指标均有所降低。但耦合系统的气化性能受到热解段焦油和CH₄产率很大的影响。耦合系统总体能量利用效率为92.26%,略低于气化废锅系统(93.39%),但其火用效率比气化废锅系统高2.2%。这说明通过热解-气化的耦合方式能够有效回收气化高温合成气中的显热并提高其能量品位。     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1:1的甲醇-水混合溶液在纳米碳管(CNT)中的静态结构以及输运行为.研究发现:在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失.另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1：1 的甲醇-水混合溶液在纳米碳管（CNT）中的静态结构以及输运行为. 研究发现：在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失. 另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.     

Sample introduction in correlation liquid chromatography Application,properties and working conditions for a novel injection system

To apply correlation liquid chromatography in practice, a reliable, accurate and simple injection system is essential. The injection system described is suitable. The system is tested thoroughly for different sample concentrations. The effects of possible non-idealities and incorrect working conditions are studied. The resulting disturbances are listed, so that inappropriate operating conditions can be traced and eliminated. To demonstrate the performance of the system, a standard mixture of polynuclear aromatic hydrocarbons is analysed and the results are compared with those obtained by conventional chromatography. The injection system and some special software greatly facilitates the practical use of correlation chromatography.     

Thermodynamic evaluation of heat recovery through a Canopus heat exchanger for vapor compression refrigeration (VCR) system

This communication deals with the waste heat recovery from the industrial refrigeration and air-conditioning system by introducing Canopus heat exchanger. There is a considerable amount of low-grade heat available in large-capacity systems. To recover this low-grade heat, a Canopus heat exchanger is introduced between compressor and condenser components. The system feasibility is studied with various operating parameters and its effect on heat recovery factor and overall COP of the system. The parametric results obtained for different eco-friendly working fluids, such as R-134a and R-507a, have been presented. It is found that, in general, overall COP of the system is improved without affecting the actual performance of the system. The potential of low-grade heat availability is increased with increasing cooling capacity.     

Conformational sampling via a self-regulating effective energy surface

The difficulty of efficiently sampling the phase space of complex systems with rough energy surfaces is well known. Typical solutions to the problem involve accelerating the crossing of barriers, but such methods often have the secondary problem that the low-energy states of interest are inadequately sampled, unless the parameters of the search algorithm are modified as the system evolves. A method is presented to improve the sampling with particular emphasis on the low-energy conformations, which make the most important contributions to the thermodynamics of the system. The algorithm proposed here samples the details of the minima, while easily surmounting barriers. This is achieved by introducing a self-regulating sampling variable which depends on the current state of the system. Two replicas of the system are introduced and the sampling variable is treated as a particle coupled to the physical system. The method is illustrated with a simple model system and is applied to the realistic example of barrier crossing in a protein-ligand complex.     

A new linear notation system based on combinations of carbon and hydrogen

A new linear notation system is described which was designed to have a one-to-one correspondence with the chemical structures represented by the notations. Each notation is unique and unambiguous, yet simple and compatible with computer input and output characters. The symbols used in the notation system denote carbon in terms of bonds and attached hydrogen(s). The notation system is illustrated with acyclic, carbocyclic, and heterocyclic examples.     

受限狭缝中CO_2-CH_4体系的汽液相平衡性质

受限条件下CO2-CH4体系的相平衡性质对化工工艺过程的设计具有非常重要的意义.采用Gibbs系综Monte Carlo模拟,对220K下CO2-CH4体系在主体相和受限狭缝中的相平衡性质进行了系统地研究.通过主体相模拟与实验结果比较,验证了流体分子势能参数的合理性;通过改变狭缝壁面原子的能量参数,研究了受限环境对CO2-CH4体系汽液相平衡性质的影响.与主体相相比,在硬壁狭缝中,CO2-CH4体系的露点压力增加,泡点压力降低,压力-组成相图变窄,且体系更容易达到超临界状态;在吸引狭缝中,随壁面原子能量参数的增大,CO2-CH4体系的压力-组成相图上移,临界点处CH4的摩尔分数减小,相图变窄.在体系汽液相总组成相同情况下,硬壁狭缝内体系的汽液相密度均比主体相中小;随壁面原子能量参数增大,气相密度变大、液相密度在CH4的摩尔分数较小时变大而当CH4的摩尔分数达到一定值后反而减小.在体系汽液相总组成相同时,受限环境下的汽化热比主体相的汽化热小且随壁面吸引势的增强越来越小;在主体相和硬壁狭缝中体系的汽化热随CH4含量的增加单调减小,而当壁面势能参数较大时汽化热随CH4含量增加先增大后减小.     

粘度法研究胶态分散凝胶交联过程

通过粘度测定方法,研究了部分水解聚丙烯酰胺（ＨＰＡＭ）／ 柠檬酸铝（ＡｌＣｉｔ） 交联过程中粘度变化的特性．聚合物浓度高的ＨＰＡＭ／ＡｌＣｉｔ 体系粘度随反应时间的延长而上升,其体系粘度最终高于相同聚合物浓度的ＨＰＡＭ 溶液粘度．聚合物浓度低的ＨＰＡＭ／ＡｌＣｉｔ 体系粘度随反应时间的延长而下降,其体系粘度低于相同聚合物浓度的ＨＰＡＭ 溶液粘度．ＨＰＡＭ／ＡｌＣｉｔ 交联体系的聚合物浓度低于临界浓度时,交联反应后形成稀胶态分散凝胶（ＴＣＤＧ） ．在实验条件下,临界浓度在１５０ ～３００ｍｇ／Ｌ 之间．当聚合物浓度于临界浓度和７００ｍｇ／Ｌ之间时,形成浓胶态分散凝胶（ＣＣＤＧ） ;当聚合物浓度高于７００ｍｇ／Ｌ 时,ＨＰＡＭ／ＡｌＣｉｔ 交联体系形成整体凝胶．     

氢化物发生-电感耦合等离子体原子发射光谱法同时测定锑锭中氢化物元素和非氢化物元素

运用改进的同心喇叭口双溶液管雾化器，采用连续氢化物发生法，在酸性介质中，对锑锭样品溶液既发生雾化作用，又对可形成氢化物的元素（Ａｓ、Ｓｅ、Ｐｂ）发生氢化作用，使它们的发射强度得到显著提高，而对非形成氢化物的元素（Ｆｅ、Ｃｕ）的发射强度基本不受影响，利用ＩＣＰ－ＡＥＳ同时测定锑锭中形成氢化物的元素和非形成氢化物的元素。对实际样品进行对比检测，结果令人满意。     

便携式远程激光诱导击穿光谱系统及其定量分析性能

因高温、辐射等极端环境限制，核领域亟需具备在线快速检测特性的分析仪器。基于小型风冷脉冲激光器与小型光纤光谱仪实现了远程激光诱导击穿光谱技术（LIBS）装置的小型化，对该便携式远程LIBS系统的定量分析性能进行了研究，实现了5 m外样品的元素遥测。在单脉冲激光能量100 mJ，脉冲延时1.0 μs的分析条件下，实现了白水晶、陶瓷及铝合金样品中Mn、Si、Al、Na、Ba、Ca及Cr元素的激发，验证了LIBS技术对材料组分和物料成分的远程探测能力，对铝合金样品的定量分析结果显示，该远程遥测系统对铝合金样品定量测量结果的最大相对平均偏差为12%，具备执行核领域快速分析场景下的半定量检测能力。     

In-line flow injection analysis for monitoring lactic acid fermentations

An automated system with in-line monitoring of important fermentation variables is described for investigating the kinetics of lactic acid fermentation. A laboratory fermentor is fitted with a continuous sample-withdrawal system and in-line analyzers are used to determine glucose, lactic acid, protein and cell density (from absorbance at 565 nm). The system is controlled by a personal computer. The flow injection analyzers for glucose and lactic acid are based on enzymatic oxidation followed by chemiluminescence detection. The flow-injection analyzer for protein is based on the biuret method. The system has a very good reproducibility and long-term stability. It appears to be ideally suited for the study of fermentation dynamics.     

Integration of optimization methodology with expert systems

An expert system for ion-pair liquid chromatography of basic drugs is described. Integration of experimental optimization methodology into the expert system is shown to be feasible. The system consists mainly of four modules: an introductory module, and initial guess module, a formal optimization module and an adaptation module. The formal optimization module, based on a simple 2 × 2 factorial design and an overlapping resolution map, is integrated with the expert system. The expert system was validated on 20 basic drugs and their 60 synthetic mixtures combined by using a random method. The rate of succes was satisfactory.     

低浓度HPAM/AlCit交联聚合物溶液性质研究

采用粘度法、扫描电镜（SEM）、核孔膜过滤、动态光散射（DLS）和27Al NMR法，研究了高分子量低浓度的部分水解聚丙烯酰胺（HPAM）与柠檬酸铝（AlCit）体系交联反应过程溶液性质变化.结果表明，HPAM与AlCit反应在低剪切速率时体系粘度随反应进行而降低，在剪切速率较高时具有剪切稠化现象，HPAM与AlCit反应过程中交联态Al的自旋 晶格弛豫时间随反应进行变短.低浓度的HPAM与AlCit发生分子内交联反应形成交联聚合物线团（LPC）在水中的分散体系，即交联聚合物溶液（LPS）.交联聚合物溶液中LPC的平均流体力学半径约为238 nm，其形态接近球形，具有多分散性. LPS对1.2 μm核孔膜的封堵程度与其反应时间有关.     

New hybrid method for reactive systems from integrating molecular orbital or molecular mechanics methods with analytical potential energy surfaces

A computational approach to calculating potential energy surfaces for reactive systems is presented and tested. This hybrid approach is based on integrated methods where calculations for a small model system are performed by using analytical potential energy surfaces, and for the real system by using molecular orbital or molecular mechanics methods. The method is tested on a hydrogen abstraction reaction by using the variational transition-state theory with multidimensional tunneling corrections. The agreement between the calculated and experimental information depends on the quality of the method chosen for the real system. When the real system is treated by accurate quantum mechanics methods, the rate constants are in excellent agreement with the experimental measurements over a wide temperature range. When the real system is treated by molecular mechanics methods, the results are still good, which is very encouraging since molecular mechanics itself is not at all capable of describing this reactive system. Since no experimental information or additional fits are required to apply this method, it can be used to improve the accuracy of molecular orbital methods or to extend the molecular mechanics method to treat any reactive system with the single constraint of the availability of an analytical potential energy surface that describes the model system.     

System Suitability in an Optimized HPLC System

Abstract

The relationship between calibration, validation and system suitability is demonstrated within the chemometric framework. The importance of system suitability is stressed and its interrelationship with mobile phase optimization is discussed. In addition, it is shown that sensitivity data generated in a mobile phase optimization study can be used to effectively set system suitability criteria and make improvements to an unacceptable chromatographic system.