一种用于多相催化可逆反应的实验方法

一种用于多相催化可逆反应的实验方法宋锡瑾，王杰（浙江大学化工系，杭州３１００２７）（杭州大学化学系，３１００２８）伍明，任仲皎，詹国庆（中南民族学院化学系，武汉４３００７４）多相催化可逆反应是一个复杂过程，其中既有化学过程，又有与物料传递性质有关的物...     

汽液共存相的粘度及导热系数间的关系

粘度和导热系数是石油、化工等工业过程设计中必需的两种主要传递性质，对它们的实验测定和理论预测或关联研究一直受到人们的广泛关注．对传递性质的研究有以下特点：在理论上，对气体，尤其是稀薄气体有较成功的动力学理论，但对稠密流体，尤其是液体，尚无严格的理论方法，实用中多为经验或半经验的模型；在实验测定方面，对液体的测定相对容易，已积累了大量数据，尤其是液体的粘度和导热系数．另外，在一些工业生产过程中，往往处理呈平衡（饱和）的汽、液两相。质，需要知道各种操作条件下两相工质的传递性质，因此，研究汽（气）、液…     

利用现有设备丰富化工实验内容

化工原理实验是一门重要的工程类实验课程 ,内容涉及动量传递、热量传递和质量传递及相关领域 ,面对的是复杂的实际问题和工程问题。通过化工原理实验课的教学 ,能使学生对工程实验方法有一个感性认识 ,提高学生发现问题、解决问题的能力。但对于大部分理科院校来说 ,化工原理实验是不能与分析、物化实验等相提并论的 ,因此 ,在化工原理实验的教学过程中 ,投入的人力、物力相对较少。　　不少院校对现有的设备进行日常维护和正常地完成实验教学工作 ,在经费上已显得捉襟见肘 ,更没有能力来添置新的实验设备和开设新的实验了。　　这里介绍的…     

化学教学语言必须做到“六个结合”

教学语言是教师在课堂上进行信息传递的工具和媒体,是一种行业性的特殊交际的语言,科学加艺术的教学语言能够有效地保证教学信息在传递过程中发挥最佳的效果。     

非平衡热力学在界面传递过程中的应用

21世纪以来，随着各学科之间的交叉渗透，化学工程的研究对象越来越复杂，界面传递对多相化工过程的影响越来越显示出它的重要性，传统的传递模型已经很难对界面复杂动态的传递行为进行定量描述．本文应用线性非平衡态热力学理论，对传统物质传递模型进行描述，分析界面传递过程速率，强化的三个因素：界面传质系数K、传递截面积A、界面化学位梯度△u．以含钾化合物作为模型体系，基于非平衡热力学原理建立了描述和预测固一液界面处介质传递速率的模型，并建立了描述其溶解速率的通用模型和测定钾离子动力学数据的实验方法，通过分析探讨了多相过程速率强化的途径．     

第四讲 玻璃毛细管气相色谱的应用

毛细管气相色谱法是一种高效快速的分离分析技术。与填充柱相比有较大的渗透性,可以作成很长的柱子增加总的分离能力。同时相比(即β值)较大,液膜薄而均匀,使柱内质传递过程大大加快,因而使用毛细管柱可以缩短分析时间。同时气相色谱方法本身又有很高的灵敏度,因此被广泛的应用于石油化工,石油地质,环境保护,食品饮料,植物挥发油,生化医药等一些比较复杂的样品的分析上。     

钙钛矿型铁酸盐氧化还原催化剂的晶格氧释放动力学研究

<正>绿色化工技术是实现化工行业可持续发展的关键~1。作为一种先进高效的低碳能源转化技术，化学链工艺在节能和减排等方面具有诸多优势~2。在化学链工艺中，氧化还原催化剂作为氧载体，实现不同反应器之间的晶格氧和热量传递。载氧体的晶格氧释放动力学是决定其反应性能的关键因素~3。ABO₃钙钛矿型复合金属氧化物由于其优良的结构循环稳定性和氧离子迁移能力，是一类具有潜在应用价值的催化材料，被广泛研究用于化学链、     

毛细管电泳接触反应法测定血清中铁传递蛋白的浓度

建立了一种测定血清中铁传递蛋白的毛细管电泳接触反应方法，利用血清中铁传递蛋白计算化学结合铁的性质，用标准铁饮和铁传递蛋通过对铁准确定量，测定血清铁伟递蛋白的有浓度。     

纤维氧化铝载体金属燃烧催化剂的研究

为了改善燃烧催化剂的传递特性,研制了纤维氧化铝载体金属燃烧催化剂。由于其较高的比表面、低的内孔扩散阻力和更高的金属分散度,该催化剂在微量丙烯及甲烷燃烧中都有比颗粒状氧化铝及其它耐热纤维载体催化剂高得多的催化活性和好的抗硫、耐热性能。钯—稀土纤维氧化铝催化剂是一种高效的烃类燃烧催化剂。     

NEWS

表复杂基体样品分子信息的快速高效获取是在分子层次上探索复杂体系化学本质的重要环节,是生命科学、食品、医药等领域发展的基础。采用常规质谱技术获取复杂基体样品分子信息时,一般需经繁复冗长的样品预处理,分析效率低,限制了相关领域的发展。近年来,东华理工大学江西省质谱科学与仪器重点实验室致力于对能量与电荷(简称能荷)在多相、多维复杂基体样品中传递及分子电离过程研究,提出了帮助理解能荷传递与中性分子电离过程的电子云     

Effects of magnetic fluids on crystallization characterizations in a multi-component and multiphase system

In this study, experiments are carried out on the effects of magnetic fluids on the crystallization char- acterizations in a multi-component and multiphase system, which contains the liquid and the vapor of HCFC141b, water, water vapor, and gas hydrates. The mass transfer phenomena between the phase interfaces of water-HCFC141b and water-vapor are also researched. The experimental results show that in the presence of a rotary magnetic field, magnetic fluids can remarkably enhance the heat and mass transfer between phase interfaces and, therefore, improve the performance of crystallization, especially in improving the formation temperature and velocity.     

染料敏化太阳电池中多相接触界面电子转移机制和动力学过程

采用电化学阻抗谱(EIS)研究了染料敏化太阳电池(DSC)中由导电玻璃、 纳米多孔TiO₂薄膜和电解质构成的多相复杂接触界面的电子转移机制和动力学过程. 通过沉积聚合物薄膜简化多相接触界面结构, 根据接触界面结构和电子转移途径的变化, 分析了不同偏压下多相接触界面电子转移机制, 构建与之对应的等效电路, 获得了DSC内部各个主要接触界面的电子转移动力学常数. 结果表明, 通过外加偏压的控制和多相接触界面结构的简化, 可以区别分析多相复杂接触界面电子转移机制与动力学过程.     

Dynamic behavior of interfaces: Modeling with nonequilibrium thermodynamics

In multiphase systems the transfer of mass, heat, and momentum, both along and across phase interfaces, has an important impact on the overall dynamics of the system. Familiar examples are the effects of surface diffusion on foam drainage (Marangoni effect), or the effect of surface elasticities on the deformation of vesicles or red blood cells in an arterial flow. In this paper we will review recent work on modeling transfer processes associated with interfaces in the context of nonequilibrium thermodynamics (NET). The focus will be on NET frameworks employing the Gibbs dividing surface model, in which the interface is modeled as a two-dimensional plane. This plane has excess variables associated with it, such as a surface mass density, a surface momentum density, a surface energy density, and a surface entropy density. We will review a number of NET frameworks which can be used to derive balance equations and constitutive models for the time rate of change of these excess variables, as a result of in-plane (tangential) transfer processes, and exchange with the adjoining bulk phases. These balance equations must be solved together with mass, momentum, and energy balances for the bulk phases, and a set of boundary conditions coupling the set of bulk and interface equations. This entire set of equations constitutes a comprehensive continuum model for a multiphase system, and allows us to examine the role of the interfacial dynamics on the overall dynamics of the system. With respect to the constitutive equations we will focus primarily on equations for the surface extra stress tensor.     

The intensification of rapid reactions in multiphase systems using slug flow in capillaries

A multiphase microreactor based upon the use of slug flow through a narrow channel has been developed. The internal circulation, which is stimulated within the slugs by their passage along the channel, is responsible for a large enhancement in the interfacial mass transfer and the reaction rate. Mass transfer performance data has been obtained for a glass chip-based reactor in a 380 microm wide channel by monitoring the extraction of acetic acid from kerosene slugs as they moved along the reactor channel. Finally, the data was compared with that provided from other inter-phase contacting techniques.     

Characterization of Simultaneous Heat and Mass Transfer Phenomena for Water Vapour Condensation on a Solid Surface in an Abiotic Environment—Application to Bioprocesses

The phenomenon of heat and mass transfer by condensation of water vapour from humid air involves several key concepts in aerobic bioreactors. The high performance of bioreactors results from optimised interactions between biological processes and multiphase heat and mass transfer. Indeed in various processes such as submerged fermenters and solid-state fermenters, gas/liquid transfer need to be well controlled, as it is involved at the microorganism interface and for the control of the global process. For the theoretical prediction of such phenomena, mathematical models require heat and mass transfer coefficients. To date, very few data have been validated concerning mass transfer coefficients from humid air inflows relevant to those bioprocesses. Our study focussed on the condensation process of water vapour and developed an experimental set-up and protocol to study the velocity profiles and the mass flux on a small size horizontal flat plate in controlled environmental conditions. A closed circuit wind tunnel facility was used to control the temperature, hygrometry and hydrodynamics of the flow. The temperature of the active surface was controlled and kept isothermal below the dew point to induce condensation, by the use of thermoelectricity. The experiments were performed at ambient temperature for a relative humidity between 35?C65% and for a velocity of 1.0?ms^?1. The obtained data are analysed and compared to available theoretical calculations on condensation mass flux.     

Energy transfer at a gas-liquid interface: kinematics in a prototypical system

A detailed characterization of collisional energy transfer at a liquid surface not only provides a framework for the interpretation of experimental studies but also affords insight into energy feedback mechanisms that may be important in multiphase combustion processes. We address this problem by performing simulations of a prototypical Lennard-Jones system, investigating the dependence of the energy transfer and incident-atom trapping probability on the liquid temperature, on the mass and angle of incidence of the impinging atom, and on the strength of the gas-liquid interaction. In general, in agreement with the results of experiments, these calculations point to the dominance of kinematic effects in determining the gross energy transfer, but they also attest to the important role played by surface roughening in the enhancement of energy transfer that accompanies an increase in the liquid temperature.     

Controlling bubbles using bubbles--microfluidic synthesis of ultra-small gold nanocrystals with gas-evolving reducing agents

Microfluidic wet-chemical synthesis of nanoparticles is a growing area of research in chemical microfluidics, enabling the development of continuous manufacturing processes that overcome the drawbacks of conventional batch-based synthesis methods. The synthesis of ultra-small (<5 nm) metallic nanocrystals is an interesting area with many applications in diverse fields, but is typically very challenging to accomplish in a microfluidics-based system due to the use of a strong gas-evolving reducing agent, aqueous sodium borohydride (NaBH(4)), which causes uncontrolled out-gassing and bubble formation, flow disruption and ultimately reactor failure. Here we present a simple method, rooted in the concepts of multiphase mass transfer that completely overcomes this challenge-we simply inject a stream of inert gas bubbles into our channels that essentially capture the evolving gas from the reactive aqueous solution, thereby preventing aqueous dissolved gas concentration from reaching the solubility threshold for bubble nucleation. We present a simple model for coupled mass transfer and chemical reaction that adequately captures device behaviour. We demonstrate the applicability of our method by synthesizing ultra-small gold nanocrystals (<5 nm); the quality of nanocrystals thus synthesized is further demonstrated by their use in an off-chip synthesis of high-quality gold nanorods. This is a general approach that can be extended to a variety of metallic nanomaterials.     

Continuous flow structuring of anisotropic biopolymer particles

We review concepts and provide examples for the controlled structuring of biopolymer particles in hydrodynamic flow fields. The structuring concepts are grouped by the physical mechanisms governing drop deformation and shaping: (i) capillary structuring, (ii) shear and elongational structuring and (iii) confined flow methods. Non-spherical drops can be permanently structured if a solidification process, such as gelation or glass formation in the bulk or at the interface, is superimposed to the flow field. The physical and engineering properties of these processes critically depend on an elaborate balance between capillary phenomena, rheology, gel or glass formation kinetics, and bulk heat, mass and momentum transfer in multiphase fluids. This overview is motivated by the potential of non-spherical suspension particles, in particular those formed from ‘natural’ and ‘sustainable’ biopolymers, as rheology modifiers in food materials, consumer products, cosmetics or pharmaceuticals.