连续微反应加氢技术在脱保护反应中的应用

保护与脱保护是医药中间体等精细化工领域中较为常见的一种有机合成策略。常用的保护基主要有苄基与苄氧羰基,通常可利用催化加氢法将其脱除。采用高压加氢间歇釜工艺存在气液传质效率低,操作安全性差,氢解效率低等问题。采用连续微反应加氢技术进行非均相催化加氢脱保护,可以利用其较高的气液传质效率和平推流特性实现高选择性脱保护,并显著缩短反应时间。本文阐述了连续微反应加氢技术在脱保护反应中的优点及其在药物中间体合成中的实际应用,并介绍了催化剂与溶剂对脱保护反应的影响。最后对连续微反应加氢技术在脱保护中的应用进行了展望。     

Mass transfer and selectivity of ozone reactions

The present research concerns the behavior of mass transport in absorption of ozone accompanied by decomposition and ozonation reactions in aqueous solutions. On the basis of the film theory, a mathematical model has been formulated for the transport process taking into account molecular diffusion and the simultaneous decomposition and ozonation reactions of different orders. Analytical approximate and finite difference methods have been employed to predict concentration profiles, enhancement factor and selectivity of the chemical mass transfer in gas-liquid systems. The rate of mass transfer is enhanced by the chemical reactions as well as the availability of liquid reactant in the aqueous phase. When the ozonation reaction is much faster than the decomposition reaction, a large fraction of the absorbed ozone is utilized effectively in reacting with the liquid constituent and a high selectivity of the gas-liquid reactions can be obtained. Calculated results indicate that removal of certain organic pollutants by the oxidation process may be effective only in acidic or neutral solutions where a high mass transfer rate and selectivity is achieved.     

微通道内伴有化学吸收气液两相流的空隙率与压力降

微通道内气液两相流空隙率与压力降对微反应器的热质传递性能有显著影响,是微反应器的重要设计参数。采用高速摄像仪和压力测量系统分别对矩形微通道内单乙醇胺水溶液化学吸收CO₂过程的空隙率和压力降进行了研究,考察了弹状流下气液两相流量与化学反应速率对空隙率及压力降的影响。结果表明:当液相流量一定时,微通道内空隙率和压力降均随着气相流量的增大而增大,空隙率随化学反应速率的增大而减小,压力降随化学反应速率的增大而增大;当气相流量一定时,随着液相流量和化学反应速率的上升,微通道内空隙率下降,而压力降上升。提出了微通道内伴有化学吸收的空隙率和压力降的半理论预测模型,模型平均误差分别为15.79%和11.12%,显示了良好的预测性能。     

气液冷等离子体多相反应器基础研究与应用进展

等离子体作为物质存在的一种基本形态,因其特有的高活性而不同于固、液、气三种形态,逐渐应用于多个领域,并发展成了一门新兴学科。由于冷等离子体参与的气液化学反应能产生更多的活性物质,而且液体的流动性能够强化活性物质的传递,因此,气体放电产生的冷等离子体与液相反应在许多领域表现出重要的应用价值,更具有探究意义。综述了几种冷等离子体的放电形式以及表征技术,重点阐述了气液冷等离子体多相反应器的不同结构以及应用,并对气液冷等离子体技术发展进行了展望。     

CONTRIBUTION TO THE ANALYSIS OF THE SELECTIVITY OF GAS-LIQUID REACTIONS PART II: COMPARISON OF EXPERIMENTAL RESULTS WITH MODEL PREDICTIONS

The chlorination of paracresol is used in an experimental study of selectivity in gas-liquid contactors.

Experiments in a batch reactor show the influence on selectivity of the dimensionless numbers presented in Part I and involving competition between mass transfer and chemical reaction together with the hydrodynamics.

The extension of open reactor model presented in Part 1 to the batch reactor permits a comparison between theory and experiments and shows a good agreement     

微反应器中乙炔法合成N-乙烯基吡咯烷酮的过程研究

搭建了以商用微反应器为核心的气液微反应系统,成功实现了加压乙炔法合成N-乙烯基吡咯烷酮（NVP）的产品过程,采用液相循环方式完成反应物2-吡咯烷酮的高效转化,全面考察了反应温度、KOH含量、内构件数量和原料乙炔纯化对液相反应的影响。结果表明,反应温度和KOH含量对选择性有显著影响,高温和高含量催化剂会严重降低产物NVP的选择性,综合调控反应温度和KOH含量,可保证产物选择性在95%以上;微反应器中内构件的存在有利于促进气液传质过程;反应体系水分的脱除有助于循环反应中转化率和选择性的提高;与高压釜相比,产物NVP收率提高了28.7%（无助剂）,反应时间有适当缩短。     

蛇形微通道内泄漏流特性

微流体系统通常具备极大的比表面积、易于控制等优势,在气-液相传质、传热、反应等方面具有良好的应用前景。本文考察了6个气液相体系在矩形截面蛇形微通道中的气液两相泰勒流流动情况以及气泡和液弹的动态行为,以气泡截面形状的几何模型为基础,得到了微通道中净泄漏流的量化方程。同时发现在较大的操作区间内,蛇形微通道对泄漏流的可控性优于直形微通道。并且详细分析了不同气液相流量、液相物性（表面张力和黏度）和气泡长度对蛇形微通道主通道净泄漏流的具体影响。     

Digital Image Processing of Gas-Liquid Reactions in Coiled Capillaries

In the course of the investigation of biocatalytic gas-liquid reactions with color change in straight and coiled capillaries, a non-invasive evaluation method is needed to determine reaction progress and selectivity. Correlations between hydrodynamics, mass transfer phenomena, and reaction kinetics are in the focus of our work. For this purpose, it is necessary to investigate the flow and evaluate the reaction progress without disturbing the flow. Digital image processing (DIP) is presented as a suitable optical evaluation method for reactions with color change in capillary reactor designs. The developed DIP program is independent from the capillary reactor design, applicable to differently colored systems, and can analyze up to three different species simultaneously.     

Enhanced Reaction Efficiency in Continuous Flow

Continuous flow reactors are enabling tools that can significantly benefit chemical reactions, especially those that are path length dependent (e.g., photochemical), mixing or transport dependent (e.g., gas-liquid), exothermic, or utilize hazardous or unstable intermediates. In this review, it is demonstrated how the nearly instantaneous mixing, exceptionally fast mass transfer, safe access to high temperatures and pressures, and high surface area to volume ratio can be leveraged to improve product yield, reaction rates and/or selectivity. By showcasing five synthetic methodologies examined by our group, it is hoped that the reader will gain an appreciation of the accessible and transformative nature of flow chemistry for improving existing transformations, enabling rapid optimization, and for developing new methodologies that depend on precise parameter controls.     

Taylor Bubble Study of the Influence of Fluid Dynamics on Yield and Selectivity in Fast Gas-Liquid Reactions

A consecutive competitive gas-liquid reaction is investigated using a Taylor bubble setup regarding the influence of fluid mixing in the bubble wake on yield and selectivity. The concentration fields behind a Taylor bubble are visualized and measured quantitatively with a novel time-resolved absorption imaging technique based on Beer Lamberts law and an integral selectivity is derived. In addition, the calculation of the local selectivity, often used in numerical approaches, is discussed and the existing experimental limits for its derivation are pointed out. Finally, an increase in selectivity of a competitive consecutive reaction for enhanced mixing is experimentally confirmed.     

湿法烟气脱硫塔内传递与化学反应过程CFD模拟

以某330 MW燃煤发电机组湿法烟气脱硫塔为研究对象，采用欧拉-拉格朗日方法建立了塔内气-液两相流动、热质交换模型，以溶解平衡、质量守恒及电荷守恒描述浆液内13种溶质组分瞬时化学反应特性，通过用户自定义函数实现流动模型与传质模型、化学反应模型的耦合。基于上述模型预测了脱硫塔内气-液两相流动、液滴蒸发与SO₂化学吸收过程，获得了SO₂浓度与浆液pH的径向分布特性，详细分析了气-液流动对化学吸收特性的影响，结果表明局部液气比分布特性是影响SO₂径向分布的关键因素之一，可通过调控近壁区及主管道区的两相流动状态提高脱硫塔的吸收性能；随着气相侧SO₂浓度提高或液滴粒径减小，浆液pH下降速率增大且各化学组分浓度达到稳定状态用时缩短。     

Effects of hydrodynamics and Lagrangian transport on chemically reacting bubble flows

The objective of this study is to investigate the dynamics of flows occurring in the wakes of rising bubbles of different shapes and sizes. Different wake dynamics can result in qualitatively different mixing characteristics. In the case of fast gas-liquid reaction networks, reactions occur almost exclusively in the bubble wake. Thus, wake mixing can have a strong impact on the reaction yield and selectivity. Dynamic numerical simulations were performed to study the flow of liquid around bubbles of different shapes. The obtained velocity and pressure fields were used to investigate the liquid-phase mixing in the flow for each case. As a strong connection between mixing and chaos is known to exist, Lagrangian tracking of passive tracer particles was used to identify chaotic fluid transport in the flows. Chaotic dynamics lead to folding and stretching of fluid elements, which results in very effective mixing. To quantify mixing, stretching fields were computed for each flow case. Finally, different liquid-phase chemical reaction networks were tested to illustrate the effects of mixing on chemical reaction yields and selectivities.     

竖直降液膜流动在反应工程中的应用

竖直元件上的降液膜流动由于具有传热传质系数高、气液接触面积大和表面更新速度快等优点,因而在化工和聚合反应工程上有着广泛应用。本文综述了竖直降膜元件上液膜流动的实验研究、理论分析和数值模拟,分别介绍了低黏流体降液膜流动在气体吸收与化学反应等方面的应用和高黏流体降液膜流动在涂覆与聚合物脱挥等聚合物加工中的应用情况。总结表明,目前对于低黏流体在竖直元件上的降液膜流动研究已较为成熟,而高黏流体降液膜流动的大部分研究仅着重于其成膜性能上。最后分析了降液膜流动的研究趋势,指出涉及热质传递与化学反应耦合的高黏流体在竖直结构上的降液膜流动是今后的重点研究对象。     

微流道气-液两相流研究及其在PEMFC中的应用进展

微流道由于具有比表面积高、传质能力强等优点,已成功地应用于化工领域的多种气-液反应体系中。此外,其在化工领域中的研究成果还可以应用于目前备受关注的燃料电池领域以提高其电化学转化效率。然而,微流道尺度的微小化以及其中气-液两相流规律的复杂性使得微流道内的气-液两相流特性的阐明还需要进一步的研究,才能促使微流道在实际应用中发挥更优异的作用。本文从流型、压降和传质三个关键特征的研究角度来介绍微流道内气-液两相流的研究进展,简述了不同流型的特征及其形成条件,阐明了其对应的压降大小和传质能力的高低,回顾了现有的压降和传质系数的预测模型及其相应的优化措施,并分析了运用这三个关键特征的相关参数来优化质子交换膜燃料电池流场设计方面的研究进展,得到了流场类型、流道尺寸、流道形状、流道表面特性等的优化方案。但是,燃料电池中的精细流道的特殊结构及其特定工况使得其与传统的微流道有显著的区别。由此,本文提出了应当根据燃料电池精细流道的特点探明其中的两相流型、压降和传质的动态变化规律以及构建相应的压降预测模型的建议,以期为流场设计提供更准确的参考依据,进而提高燃料电池性能,加速燃料电池的商用进程。     

水力喷射空气旋流器中射流流型及其对传质面积和气相压降的影响

为了进一步提高水力喷射空气旋流器（WSA）的传质效率以及认识射旋流体系的气液传质机理,对WSA中的射流流型进行了系统的观察研究,绘制出了不同进口气速下射流流型图。以CO₂-NaOH化学吸收体系测定了相应射流流型下的有效比相界面积a。结果表明,在低射流流速（≤4.42 m·s^-1）下,液相射流随着进口气速增大,主要存在稳态射流、变形旋线射流、破碎旋线射流、雾化旋线射流、贴壁雾化旋线射流5种流型;在高射流流速（≥6.19 m·s^-1）下,射流主要出现稳态射流、破碎旋线射流以及雾化旋线射流3种流型。a值与流型有关,雾化旋线射流下的a值大于其他流型下的对应值。低流速下的贴壁雾化,不利于气液两相充分接触,对应a值较小。a值与射流流速有一定关系,随着射流速度的增大而略有增大,且随着射流流速增大至8.84 m·s^-1以上,增大的幅度变大。     

Engineering Aspects of Gas-Liquid Catalytic Reactions

The modeling of a reaction unit in which the absorption of a gas is associated with a liquid-phase catalytic reaction is a difficult problem in which both chemical and fluodynamic factors are involved. Many excellent reviews in which the chemical details of the liquid-phase catalytic processes and the engineering implications of the gas-liquid reactions are separately discussed are available.     

对二甲苯氧化过程控制步骤分析

实验测定了对二甲苯高温氧化各步反应动力学数据。结合反应器中的气液传质数据以及有关的混合时间数据,比较了反应、传质和混合速率的相对大小。结果表明,工业反应器中的混合速率远大于反应速率,反应器可以作为理想混合反应器考虑。在典型的工业条件下,对二甲苯氧化过程为液相化学反应控制,控制步骤为对甲基苯甲酸生成对羧基苯甲醛的反应步骤。     

气液等离子体过程强化技术及其在高级氧化过程的应用

气液等离子体过程强化技术是20世纪80年代发展起来的一门新兴交叉学科,在高级氧化过程、液相化学合成和纳米材料制备等领域具有巨大的研究与应用价值。从化学工程的角度理解,气液等离子体过程强化技术的本质是特殊外场作用下的多相传递与反应过程,其中涉及高能电子碰撞、化学活性组分氧化、紫外光解和冲击波等多种物理与化学作用。由于气液等离子体过程强化技术本身的复杂性及多学科交叉性,对其复杂的物理与化学耦合机理还未得到充分认识,同时缺乏对气液等离子体反应器的系统研究及设计指导,从而极大程度地限制了该技术的进一步应用和发展。为全面认识气液等离子体过程强化技术,本文综述了近年来有关气液等离子体过程强化技术的诊断及机理研究进展,并剖析了气液等离子体反应器的设计思路,同时回顾和展望了气液等离子体高级氧化过程的最新研究进展,讨论了气液等离子体过程强化技术的研究方向。     

A study of oxygen absorption kinetics in ionic Cu(I) aqueous solutions

We developed the oxidation reaction of Cu(I) ion in aqueous hydrochloric solution by oxygen in a gas-lift capillary bubble column. The method of gas-liquid absorption with chemical reaction was used. Test data confirmed that the rate constant of the reaction is strongly affected by solution compositions, and that chloride ions induce an inhibition effect. The kinetical orders found are equal to 1 and 2 for oxygen and Cu(I) respectively. The influence of temperature on reaction rate constant showed the existence of a maximum value between 303 and 313K. The effect of gas-liquid of gas-liquid system on the liquid-side mass transfer coefficient k_L was also investigated.     

微化工过程中的传递现象

微化学工程是现代化学工程学科前沿,主要研究微时空尺度下流体流动、传热、传质现象与反应规律。着重介绍近十年来微通道内气-液、液-液两相流体流动、混合与传质的理论和实验的最新研究进展,并对微化工技术的发展进行展望。