Achievements and tasks of electrochemical engineering

This review of some of the most outstanding achievements of ECE in recent years highlights the role played by new concepts in plant optimization and in the obtention of high space time yields. The application of new materials to the design and construction of electrochemical reactors has also been responsible for the latest breakthroughs in electrochemical industry. The fundamental approach whereby each achievement presented in this survey was made possible should encourage a more extended teaching of electrochemistry in chemical engineering schools.     

Electro-membrane reactor: A powerful tool for green chemical engineering

Electro-membrane reactors use electro-membranes for preferentially diffusive/electrophoretic migration or electroosmotic separation of in-situ reactive products, thereby maximizing the reaction rate and transport efficiencies of the products. These reactors are widely employed in the chemical engineering sectors such as green chemical synthesis, biorefining, electrocatalytic reduction/oxidation, and water treatment. In this review article, we provide an overview of the recent advances in three categories of electro-membrane reactors in chemical engineering sectors from three categories: (1) Electro-membrane reactors based on stacked ion-exchange membranes for resources recovery; (2) Electro-membrane reactors via Faraday reactions on functional anodes/cathodes for substance transformation; and (3) Closed-loop chemical reactions and substance separation via coupling of Faraday reactions and stacked membranes. The increasing demand for low-carbon economy has accelerated the advancement of environmentally friendly chemical engineering and sustainable processes and necessitates the use of electro-membrane processes. The macro perspective provides a timely reference for researchers and engineers.     

Verfahrenstechnik der Kohlehydrierung in Sumpfphasen-Reaktoren

Chemical engineering of coal hydrogenation in sump phase reactors . The science of chemical engineering was still in its infancy when the hydrogenation of coal was developed from 1924 onwards at Ludwigshafen, Rhineland. The term backmixing, for example, was unknown. Nevertheless, the scale-up from a pilot to a production reactor was performed correctly at that time. Even with today's knowledge, the IG Farben sump phase reactors could not have been better designed. Almost four decades have meanwhile elapsed since the cessation of coal hydrogenation in Germany (1945). Nowadays high pressure reactors having more than 50 times the volume of the IG reactors can be produced. Considerable advances have also been made in measurement and control engineering. Hence new chemical engineering questions and solutions arise. If coal hydrogenation is to be performed on a significant industrial scale in 10 to 20 years, this will be economically feasible only by exploiting the possibilities of large reactors having a throughput of 1 to 3 million tons of coal per annum.     

Milestones and perspectives in electrochemically promoted catalysis

Electrochemical promotion of catalysis is a unique tool for the in situ tuning of catalytic activity of electronically conductive metals or metal oxides in contact with solid electrolytes. The importance of electrochemical promotion to heterogeneous catalysis, surface science and electrochemistry research for the investigation of spillover phenomena and metal–support interactions is well recognized. The unlimited applications of the phenomenon, in terms of catalysts, solid electrolytes or catalytic reactions selection, has been proven through numerous laboratory investigations. Though the molecular origin of electrochemical promotion has been revealed, using a variety of experimental techniques and theoretical calculations, there is still a shortage on the practical level. However, in the last decade, spectacular progress has been made in the development of effective, low cost electropromoted catalysts and reactors. The major technological advances and milestones towards the practical utilization of electrochemical promotion are surveyed in view of electrocatalysts development and system/reactor engineering.     

Electrochemical microstructured reactors: design and application in organic synthesis

The use of micro structured reactors is an accepted technology in fundamental chemical research as well as in industrial applications. The application of electrochemical microreactors (ECMR) has not attracted as much attention as continuously performed reactions in a confined space. Nevertheless ECMRs are in use to perform electro-organic reactions. In this review, different aspects of ECMRs with structured electrodes and interelectrode distances of mainly ≤100 μm are investigated and discussed, together with various manufacturing techniques and prototypes described therein. Based on representative examples described in various publications for electrolysis (for direct and indirect electrolysis) advantages and disadvantages of electrochemical microreactors are presented and compared with those of conventional electrochemical reactors.     

Mathematical reactor modelling for coupled chemical and electrochemical processes: the ECE system

A procedure for modelling electrochemical reactions and reactors which involve heterogeneous reaction, homogeneous fast chemical reaction and diffusional mass transport is described. The procedure can be applied to any combination of first order reaction processes utilising numerical routines for the solution of initial value differential equations. By the use of collocation it can be extended to higher order processes. The reactor types considered are batch, plug flow and dynamic continuous stirred tanks and reactors with recycle. Operation with either potentiostatic, galvanostatic or constant cell voltage control is described and illustrated using the ECE reaction mechanism, involving successive electrochemical, chemical and electrochemical reaction.     

Reaktorstabilität und sichere Reaktionsführung

Reactor stability and safe reaction engineering . Stable operating behaviour of chemical reactors and stability in the sense of stability theory of chemical processes are by no means synonymous concepts. Thus, appropriate control can permit reliable operation at a unstable operating point, while even global stability will not necessarily rule out a runaway reaction. The latter is the case when strongly exothermal reactions are characterized by a pronounced parametric sensitivity. In order to delineate the concepts, ?stability”? and ?parametric sensitivity”? are explained first for stirred tank and tubular reactors with strongly exothermal reaction. Both the conventional view of reaction engineering and the theory of heat explosion commonly used in reaction engineering are considered in detail. Practical problems of safe reaction engineering are subsequently discussed for the control of batch reactors, the control of semibatch reactors, and the behaviour of bundled-tube reactors.     

多相反应体系的微界面强化简述

加氢、氧化等气液慢反应过程广泛存在于现代过程工业之中,这些反应过程一般受传质速率控制。因此,对这类多相反应体系的传质强化一直是研究热点之一。但总体而言,除外场和微通道（微流控）强化等一类强化反应器外,以往的研究大多集中于界面尺度为毫-厘米级的传统反应器的搅拌与混合方式、气泡分布状态、流体流型、构效关系等方面,而鲜有将研究视角投放到传统以米为直径计量单位的反应器平台上如何构建尺度为微米级的界面体系及其特殊效应方面。探讨了多相反应体系的微界面反应强化理念,并简述了微界面的涵义、微界面反应强化与构效调控方法、微界面反应器的结构与形成原理、微界面体系的微颗粒测试与相界面表征技术、微界面反应强化面临的问题与挑战等,以与本领域同行共同研讨。     

Recent Advances in MRI Studies of Chemical Reactors: Ultrafast Imaging of Multiphase Flows

NMR has long been established as an in situ technique for studying the solid-state structure of catalysts and the chemical processes occurring during catalytic reactions. Increasingly, pulsed field gradient (PFG) NMR and magnetic resonance imaging (MRI) are being exploited in chemical reaction engineering to measure molecular diffusion, dispersion and flow hydrodynamics within reactors. By bringing together NMR spectroscopy, PFG NMR and MRI, we are now able to probe catalysts and catalytic processes from the angstrom-to-centimeter scale. This article briefly reviews current activities in the field of MRI studies applied to catalysts and catalytic reactors. State-of-the-art measurements, which can already be used in real reactor design studies, are illustrated with examples of single-phase flow with and without chemical reaction in a fixed-bed reactor. The ability to obtain high spatial resolution (< 200μm) in images of the internal structure and flow field within reactors is demonstrated, and the potential uses of these data in reactor design and understanding bed fouling phenomena are discussed. In particular, MRI has produced the first detailed measurements of the extent of heterogeneity in the flow field within fixed-bed reactors. The example of a fixed-bed esterification process is used to show how NMR spectroscopy and MRI techniques can be combined to provide spatially resolved information on both hydrodynamics and chemical conversion within a process unit. The emerging area of ultrafast MRI is then highlighted as an area of particular interest. Recent advances have demonstrated that it is possible to record 2D images over timescales of ～100ms in the magnetically heterogeneous environments typical of heterogeneous chemical reactors. These advances open up opportunities to image many unsteady state processes for the first time. Examples are given of real-time visualization of bubble-train flow in a ceramic monolith and exploring the stability of the gas–liquid distribution as a function of liquid flow rate in a trickle-bed reactor.     

Finite element collocation solution of tubular and packed-bed reactor two point boundary value problems

Nonlinear two point boundary value problems (TPBVP's) are frequently encountered in chemical engineering. TPBVP's describing tubular and packed-bed reactors are important and have received much attention in the literature. For certain ranges of parameter values of the reactors, the TPBVP's become stiff and pose problems in numerical solution. These problems have been efficiently solved by the finite element collocation method using Hermite and B-spline functions in conjunction with quasilinearization. Numerical results have been presented and discussed. The problems have been solved for a wide range of parameter values without encountering any numerical difficulty.     

合成1,4—丁二醇开发技术中的工艺与工程

合成1,4-丁二醇的大规模工业生产是在国内外同时采用滴流床、浆态床和三相悬浮床三种反应器仅有的反应工艺,对这一反应工艺所用不同反应器的开发方法,包括催化剂制备及考评,各种专用冷模试验和专用反应器的热模试验及动力学测定。应用数学模拟分析和实验相结合,从小试、中试到工业试验,可为大型装置设计提供依据。本文总结了气、液、固三相反应器的基础研究和工业实践相结合的经验、催化剂和反应器工程协调的评价,以及催化剂的制备技术。     

Multifunktionale Reaktoren

In multifunctional reactors chemical and physical unit operations are carried out simultaneously. Traditionally chemical reaction engineering considers mass and heat transfer processes in combination with chemical reactions. However, the term multifunctional reactor points to an extended and more detailed view of process integration. By application of these reactors it is possible to save investment and/or operating costs, to meet environmentally relevant limits or to improve process safety. Mechanical and thermal unit operations are especially good candidates for integration with a chemical reaction step. In this contribution selected multifunctional reactors are presented, which were either adopted from the literature or are the subject of the authors' own research activities.     

Basismodelle für Reaktoren — eine kritische Bilanz

In the literature of chemical reaction engineering, the basic models for reactors are deduced in different ways. This paper demonstrates that the authors do not always stringently differentiate between fluid mechanics and chemical reaction engineering methods. Thus misinterpretations may arise. As this publication shows, it would be more precise to use instead of ideal reactors the term completely/radially mixed reactors (mixing vessel/pipe). In addition, attention is directed to convection reaction models. They give an idea of the local concentration profiles in reactors for a small mathematical effort. The models give predictions superior to those of the ideal reactor models and of the dispersion model, both of which can only give mean values.     

对载体催化剂的工程研究

运用化学工程的基本原理对载体催化剂进行工程研究导致化学反应工程与催化科学相结合。需按不同化学反应的特点进行催化剂设计,并解决大规模工业催化反应器所需工业催化剂的选用、改进、考评及制备等问题,所研究的内容包括:(1)载体催化剂设计的工程基础研究,(2)催化剂和反应器开发的工程协调;(3)载体催化剂制备技术和有关重要化工单元操作的研究与应用。本文涉及的领域是非常广泛的,因而仅能作简要的分析介绍。     

Organische Synthese mit mikrostrukturierten Reaktoren

Organic Synthesis with Microstructured Reactors This article describes the chances microstructured reactors offer for chemical plant engineering. This suitability for chemical production is commonly regarded to be the key to the market penetration. Seen in the long term, there is potential that new plants can be equipped with microstructured reactors. Only economic balances, however, which draw up profitability, will open the door to the usage of chemical micro process engineering for plant construction. Main arguments for using microstructured reactors are thus enhanced conversion and selectivity, increased space‐time yields, waste reduction and more safety via small reactor volumes. Credit‐card sized reaction systems allow one to perform the screening of multi‐phase reactions. More prominent, similar screening is carried out for single‐step reactions. Moreover, safe processing with microstructured reactors in the explosive regime enlarges the traditional range of processing. The reaction guidance by microstructured reactors can further influence subsequent processing steps such as product purification and, in this way, can lower the energy costs of processes.     

电化学反应器隔膜材料的分子设计与介尺度策略

电化学反应器中隔膜材料是将正极和负极在电子通路上隔开但在离子传输通路上保持畅通的特殊材料。作为电化学反应器三个关键材料之一,隔膜材料还需耐强酸/强碱和高电压等环境。围绕电化学反应器中隔膜材料,从分子设计的角度针对材料电化学性能与化学稳定性的调控、电化学装置的介观传质性能的促进和改善等研究思路与进展进行了综述,为相关研究提供性能导向的分子设计参考。     

化学反应体系的多定态特性

化学反应体系的多定态特性是化学反应体系存在的固有特性。近年来,对它的研究已成为化学反应工程研究的热门课题。本文对化学反应体系的多定态特性的研究进展,特别是对化学反应器、催化剂题粒的多定态特性及其理论研究模型和实验研究成果进行了评述,指出了今后研究工作的发展方向。     

间歇化学反应器的先进控制技术

介绍了间歇化学反应器的主要特征及先进控制技术在间歇化学反应器控制中的应用与分类。间歇式化学反应器具有极大的灵活性和多功能性的特点。用于间歇式反应器中的先进控制技术主要分为3类，即自适应控制、模型预测和智能控制。这3类控制技术在生产中得到了应用，产生了明显的经济效益。对国内外先进控制技术之间存在的差距进行了简要的分析，认清间歇化学反应器控制所存在的不足，并进行了展望。     

Periodic pressure forcing of catalytic reactions

Use of total pressure modulation to improve reactor performance has attracted attention for about three decades from a several different fields: chemical engineering, metallurgical engineering and biochemical engineering. Ultrasonic excitation of both mass transfer and reaction systems has been discussed in the literature extensively. Although ultrasonic pressure waves are low-amplitude, high-frequency, total-pressure oscillations, this review will consider such excitation just peripherally. Our attention will be focussed on forcing at higher amplitudes and much lower frequencies. These are directed at enhancing mass transfer in porous catalyst particles. High-amplitude forcing has been studied for other reactor operating variables such as feed composition and temperature. Modulation in which an abrupt pressure reduction is employed can stimulate reaction systems that are product-inhibited. There is a no literature in this area, but interest is growing because an extension of the principles involved leads to pressure-swing reactors.     

微反应器在化学化工领域中的应用

微反应器是微型化学反应系统,具有换热和传质效率高、严格控制反应时间、易于放大、安全性能好等特点。和传统搅拌反应器相比,这些特点使得微反应器在缩短反应时间、大幅度提高化学反应的转化率和产品收率等方面展现出一定的优势。但微反应器也存在易堵塞,催化剂负载、微通道的设计与制造难度大等问题。本文介绍了近年来快速发展的微反应器技术,回顾了微反应器的特点,重点探讨微反应器在化学化工领域的应用以及微反应器在精细化工和制药工业、生物化工领域的应用实例,讨论了微反应器目前存在的诸多挑战。微反应器目前是化学和化工学科的前沿和热点方向,分析表明微反应器仍然有很大的发展空间,有潜力改变化学化工前景。提出应进一步深入系统地认识微反应器内化学反应以及微通道设计的基本规律和机理,将微反应器技术引入更广泛的反应体系中,加强微反应器的集成化水平。