微/纳反应器的研究现状及发展前景

微化工系统已经成为解决许多高新技术领域的化工过程问题的关键,而微反应器作为微化工系统的核心已经成为研究的热点之一。本文着重分析了微反应器的概念、分类及其性能优势,总结出近年来国内外微反应器的研究发展情况和存在的问题,并对发展前景进行了展望。     

微化工技术研究进展

微化学工程与技术着重研究微时空尺度内的微型设备和并行系统中的过程特征和规律.由于特征尺度的微型化,表(界)面作用增强,传递作用较常规尺度的设备中提高了2～3个数量级.开展微化工技术研究旨在增强化工过程安全性、促进过程强化和化工系统小型化,提高能源、资源利用效率,达到节能降耗之目的;其成功开发与应用将对化学化工领域产生重大影响.本文将讨论微化学工程与技术的最新研究进展.     

微化工技术

微化工技术是20世纪90年代初顺应可持续发展与高技术发展的需要而兴起的一门新的学科,它着重研究时空特征尺度在数百微米和数百毫秒以内的微型设备和并行分布系统中的过程特征和规律.微化工系统通常包括了微热系统、微反应系统、微分离系统和微分析系统.微型设备的面积体积比很大,表面作用增强,传递作用比在常规尺度的设备中提高了2～3个数量级.本文就微化工技术的发展历史、基本特征、研究内容以及发展方向做一简单的介绍.     

微尺度内液-液传质及反应过程强化的研究进展

微化工技术作为一种高效的过程强化技术获得了广泛应用。本文从流动、传递及反应三者之间的耦合机制出发,系统综述了近十五年以来关于微尺度内液-液两相流动与传质过程特征、强化传质的微反应器、评价标准及其在化学品合成与材料制备中的应用等方面的研究进展,并对其未来发展方向进行了展望。     

微尺度下非均相反应的研究进展

微结构反应器(微反应器)是微化工系统的核心装备之一,是实现化工过程强化的重要技术基础。从微尺度非均相反应过程的基本原理出发,系统综述了近十年来微尺度下多相流动、分散和传递等方面的相关报道,系统地介绍了一些典型微尺度非均相反应过程,分析总结了微尺度反应技术的优势和特点,并对未来微尺度反应技术的发展方向提出了展望。     

微型化工设备的研究与应用进展

微型化、集成化是未来科学技术的发展方向,在微化工过程中,微型化工设备的开发和应用为微化工的实现提供了强大的支持。按用途将微型化工设备分为微热交换器、微反应器、微分离器、微混合器等,分别对其特点和研究应用现状进行简单的介绍,并对其前景进行展望,同时指出了未来发展可能会遇到的难题。     

微反应器研究最新进展

微化工系统是实现化工过程绿色、安全、高效的重要方法,微反应器作为微化工系统的核心已经成为科学研究的热点之一.近年来,随着微尺度下"三传一反"研究的进展,微尺度流体的性能得到了深入揭示,微反应器技术也被广泛应用于科学研究和工业生产领域.本文以液相微反应器性能和应用为中心,重点讨论微反应器研究的最新进展.     

面向硝基化学品安全生产的绝热连续微反应技术发展及思考

硝化反应是典型的快速强放热反应，是生产含能化学品的重要反应，但也是安全事故频发的反应，因此“谈硝色变”是含能化学品生产面临的重大挑战。本文指出：与国外比，我国硝化工艺和装备都存在明显差距，连续硝化是卡脖子技术。文中总结了清华大学微化工团队提出绝热微反应连续硝化思路，提出其在芳香化合物绝热微反应硝化研究中取得的进展，指出该技术创新主要涉及微反应工艺安全系统评价方法、硝化动力学、绝热反应工艺、微化工系统构建和硝化全流程工艺再造。     

微化工技术研究分析

当今的社会生产力水平高度发达,科学技术更是高度发展,延伸到社会的各个领域和人民群众的日常生活当中。二者相辅相成、相互促进,在作用与反作用过程当中使社会得到了高度的发展,达到了前所未有的程度。在二者相互促进发展的过程中催生了一种高新技术,即微化工技术,是一种将化学化工原理和微机电系统相结合的多学科交叉的科技前沿领域,所涉及的有物理、化学、化工、电子、控制学、材料等各种工程技术和学科等。并将几百毫秒和几百微米以内,并行分布系统和化工微设备设计、模拟、生产和应用过程中特征和规律这些作为微化学工程的主要研究内容。微化工技术能提高单位体积的生产能力,大大提高能量和资源的利用率,可见,发展微化工技术对促进经济的发展和社会的进步有着重大的意义。     

微化工技术的研究与应用

微化工技术是20世纪90年代初兴起的多学科交叉的科技前沿领域,是集微机电系统设计思想和化学化工基本原理于一体,并移植集成电路和微传感器制造技术的一种高新技术,涉及化学、材料、物理、化工、机械、电子、控制学等各种工程技术和学科;其主要研究对象为特征尺度在数微米到数百微米间的微化工系统.作者对微化工技术的过程强化原理、微化...     

旋转床超重力环境下多相流传递过程研究进展

旋转填充床作为一种高效的传质、分离与反应设备,在化工、环境保护、纳米材料制备、能源、制药等工业过程得到广泛应用。本文对旋转填充床超重力环境下,流体力学特性、传质性能、微观混合、多尺度传递特性等方面的研究进行了总结归纳。近年来,随着计算机科学与多相流传递过程的研究进展,对传递过程的研究也由实验手段为主转变为实验与数值模拟相结合的手段,对有关的数值模拟研究以及相应的多相流模型也予以总结描述。在此基础上,对旋转填充床超重力环境下多相流研究的未来发展提出了有关设想。     

喷射环流反应器应用研究进展

描述了喷射反应器的结构和工作原理,详细介绍了喷射反应器作为多相反应器在化学化工、生物化学、环境保护和其它领域的应用研究进展,充分显示了喷射反应器的优异性能及其在多个领域中的重要地位,并对其未来的发展进行了展望。     

Multiphase catalytic reactor engineering and design for pharmaceuticals and fine chemicals

A review of recent developments in multiphase catalytic processes for the manufacture of pharmaceutical and fine chemicals, and an overview of reaction engineering principles needed for analysis of the local and overall reaction rate for reactor design and interpretation of performance is presented. The first section gives an overview of recent applications in pharmaceuticals and fine chemicals where heterogeneous and homogeneous catalyzed multiphase chemistries have been identified that are more efficient and represent safer operation with decreased environmental impact when compared to existing processes. The next three sections describe a scheme for classification of the various types of reactions that are typically encountered, along with distinguishing features of these reactions and commonly used multiphase reactor types. This is followed by a review of reaction engineering principles needed for describing the local overall rate of reaction, including a summary of typical models for evaluation of the intrinsic reaction kinetics, incorporation of transport-kinetic interactions, methods for identification of the controlling reaction regime and assessment of the relative contribution of transport effects. The next two sections set forth basic reactor models for commonly used reactor types, including mechanically agitated reactors and bubble column reactors. A brief summary of commonly used correlations for estimation of mass transfer coefficients in these reactors for gas-liquid and liquid-liquid systems is also given. The final section is devoted to a summary of key reaction engineering issues that occur in pharmaceutical and fine chemical multiphase catalytic processes, along with some thoughts on future needs and challenges.     

Catalytic wet oxidation: micro–meso–macro methodology from catalyst synthesis to reactor design

Compared to alternative mature wet oxidation technologies that have tremendously proliferated in industry, heterogeneously mediated catalytic wet oxidation (CWO) has achieved, thus far, poor commercial penetration. The two factors that are likely responsible for this situation are (i) the lack of efficient and robust catalysts that pass with success the acid-test for commercial exploitation remote from the aseptic academic conditions, (ii) and the lack of a comprehensive reactor design framework and methodology for scale-up, reactor selection and operation inherent to the multiphase nature of the CWO reactors. This synthetic review summarizes the recent research and development work conducted at Laval University on the CWO from both the perspectives of catalyst development and testing, and multiphase reactor simulations and selection. Specific emphasis was put, on the one hand, on the development brought to some manganese oxide–ceria composites against deactivation, and on the other hand, on the formulation of multidimensional unsteady–steady non-isothermal mass-energy transport/reaction models, embedding catalyst deactivation or not, for trickle bed reactors, packed bubble column reactors, three-phase fluidized beds and slurry bubble columns. A micro–Meso–macro scale methodology was adopted from the materials synthesis up to reactor selection in which the catalyst performance (conversion, selectivity, and deactivation), the intrinsic chemical kinetics, the fluid phase thermodynamics, the pellet scale transport, and the reactor scale physical phenomena (heat, mass transport and hydrodynamics) were integrated. As a result, several aspects relevant to reactor behaviour such as solvent evaporation due to CWO reaction exothermic effects, catalyst partial wetting and catalyst deactivation, and back-mixing effects were covered, and recommendations were formulated.     

微通道限域空间内的气泡破裂研究进展与展望

多相微反应器等微通道设备具有高效、安全等优势与广阔的应用前景,其中气泡分散相的形变、聚并、破裂等诸多流体力学行为对反应体系具有非常重要的影响,然而由于微通道的尺度特征以及多相流动非均匀性、复杂性等特点,复杂限域结构内的气泡形变与破裂机理认识仍不够充分。本文针对近年来在微尺度限域结构中的气泡形变与破裂等研究进展进行综述,首先概述了微通道多相流主要研究对象及研究方法,探讨了含有颗粒等受限狭窄空间及复杂多相条件下的传递机理研究进展,总结了气泡界面演变及不稳定破裂过程的多相相间作用机制。最后,提出研究体系构建、研究方法改进、相间作用解析以及工程化需求匹配是微尺度复杂限域空间内的气泡行为研究关键,并对下一步研究方向进行了分析与展望。     

Numerical simulation of micro-mixing in gas–liquid and solid–liquid stirred tanks with the coupled CFD-E-model

The coupled CFD-E-model for multiphase micro-mixing was developed, and used to predict the micro-mixing effects on the parallel competing chemical reactions in semi-batch gas–liquid and solid–liquid stirred tanks. Based on the multiphase macro-flow field, the key parameters of the micro-mixing E-model were obtained with solving the Reynolds-averaged transport equations of mixture fraction and its variance at low computational costs. Compared with experimental data, the multiphase numerical method shows the satisfactory predicting ability. For the gas–liquid system, the segregated reaction zone is mainly near the feed point, and shrinks to the exit of feed-pipe when the feed position is closer to the impeller. Besides, surface feed requires more time to completely exhaust the added H⁺ solution than that of impeller region feed at the same operating condition. For the solid–liquid system, when the solid suspension cloud is formed at high solid holdups, the flow velocity in the clear liquid layer above the cloud is notably reduced and the reactions proceed slowly in this almost stagnant zone. Therefore, the segregation index in this case is larger than that in the dilute solid–liquid system.     

Numerical simulation of micro-mixing in gas-liquid and solid-liquid stirred tanks with the coupled CFD-E-model

The coupled CFD-E-model for multiphase micro-mixing was developed, and used to predict the micro-mixing effects on the parallel competing chemical reactions in semi-batch gas-liquid and solid-liquid stirred tanks. Based on the multiphase macro-flow field, the key parameters of the micro-mixing E-model were obtained with solving the Reynolds-averaged transport equations of mixture fraction and its variance at low computational costs. Compared with experimental data, the multiphase numerical method shows the satisfactory predicting ability. For the gas-liquid system, the segregated reaction zone is mainly near the feed point, and shrinks to the exit of feed-pipe when the feed position is closer to the impeller. Besides, surface feed requires more time to completely exhaust the added H⁺ solution than that of impeller region feed at the same operating condition. For the solid- liquid system, when the solid suspension cloud is formed at high solid holdups, the flow velocity in the clear liquid layer above the cloud is notably reduced and the reactions proceed slowly in this almost stagnant zone. Therefore, the segregation index in this case is larger than that in the dilute solid-liquid system.     

生物膜填料床内含有生化反应的多相传输模型

废气处理生物膜滴滤塔的多孔填料床内是带有气液两相流动、有机污染物扩散、生物膜内生化反应的复杂生化反应体系.在平行平板理论模型基础上,建立了生物膜多孔填料床内含生化反应的多元多相流动及传输特性的多相混合模型,获得了废气处理生物膜滴滤塔净化效率的理论计算方法.模型的理论预测值与生物膜滴滤塔净化低浓度甲苯废气的实验结果基本吻合.     

Environmentally benign multiphase catalysis with dense phase carbon dioxide

Environmental concerns stemming from the use of conventional solvents and from hazardous waste generation have propelled research efforts aimed at developing benign chemical processing techniques that either eliminate or significantly mitigate pollution at the source. This paper provides an overview of heterogeneous and homogeneous catalysis in dense phase CO₂, considered a green solvent. In addition to solvent replacement, the demonstrated advantages of using dense phase CO₂ include the enhanced miscibility of reactants, such as O₂ and H₂ which eliminate interphase transport limitations, and the chemical inertness of CO₂. Further, the physicochemical properties of CO₂-based reaction media can be pressure-tuned to obtain unique fluid properties (e.g. gas-like transport properties, liquid-like solvent power and heat capacities). The advantages of CO₂-based reaction media for optimizing catalyst activity and product selectivity are highlighted for a variety of reactions including alkylation on solid-acid catalysts, hydrogenation on supported noble metal catalysts and a broad range of homogeneous oxidations with transition metal catalysts and dioxygen as an oxidant. Through these examples, the need is emphasized for a systematic approach to research and development of supercritical carbon dioxide based processes, taking into account conventional multiphase reaction engineering principles, catalytic chemistry and phase behavior.