Microstructured reactors and supports for ionic liquids

Different types of microstructures and their applications with respect to the synthesis and the use of ionic liquids are presented. Microstructured reactors are suitable for reactions with fast intrinsic kinetics, requiring high mass and heat transfer performances. Chemical synthesis can be performed safely under operating condition (e.g. high temperature, pressure, etc.) difficult to obtain in traditional reactors. The examples presented clearly indicate that microstructured reactors offer superior performance for the synthesis of ionic liquids in comparison to conventional equipment. For the use of ionic liquids as reaction media, existing ionic liquids show some limitations due to their higher viscosity compared to conventional solvents. Therefore, future research should be focused on the development of low viscosity ionic liquids.The approaches to use ionic liquids in microstructured reactors and in combination with microstructured supports for catalytic reactions show many advantages in view of high product selectivity and yield. The use of supported ionic liquids on microstructured materials seems to be particularly promising for gas phase as well as for gas/liquid reactions.     

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.     

微结构反应器中CuZnAlZr催化剂CO变换反应动力学研究

在基于泡沫金属材料的微结构反应器中进行CO变换反应，考察CuZnAlZr催化剂的CO变换反应动力学。对实验数据进行最小二乘非线性回归，所得反应速率方程与实验数据吻合。利用所得到的动力学方程，针对典型醇类重整气组成，分析了为燃料电池提供氢源的CO变换反应器的体积功率密度，结果表明，CuZnAlZr微结构反应器是为小型燃料电池提供氢源的有效方案。     

密封双极性MH/Ni电池结构改进与研制

Nickel metal hydride batteries in bipolar design offer significant advantages as a power storage system for electric vehicles. This study deals with some aspects in structure design and development of bipolar nickel metal hydride batteries. An improvement on conventional bipolar structure was made, and some novel sealed bipolar nickel metal hydride batteries with 6 cells were assembled and studied. Testing results showed that the improved structure effectively protected the worst single cell of bipolar battery, and led to a better pressure and cycle performances of novel batteries compared with conventional ones. In addition, the improved bipolar batteries showed excellent discharge and recharge ability, and low resistance in electrochemical tests. As simulating hybrid electric vehicle working conditions, the batteries displayed good stability during pulse cycles, which indicated the possibility of being used on electric vehicles.     

Optimization based conceptual design of reactive distillation for selectivity engineering

Reactive distillation can be effectively used to enhance the selectivity of the desired product in a multi-reaction system. Due to complex interaction of reactions and distillation, identification of an appropriate reactive distillation configuration for the known performance targets has been a challenge. The objective of this contribution is to present an MINLP optimization technique that would assist one to identify a suitable configuration for selectivity maximization at conceptual design level. An illustrative example of industrially important reaction of dimerization of isobutene for maximizing the selectivity toward di-isobutene is considered. The results of the optimization are found to be in agreement with those obtained by performing independent simulation using ASPEN PLUS simulator. Thus, the work highlights the potential of an optimization based tool for conceptual design of reactive distillation that involves complex reaction systems.     

Simulation of foaming in reaction injection molding

Blowing agents are often used in the reaction injection molding process to compensate for the shrinkage that occurs upon polymerization, thereby creating a structural foam part. Controlling the thickness of the solid skin and foamed core is essential to achieve the intended mechanical properties of the molded part. A numerical model was developed to predict the foaming behavior in reaction injection molding. This algorithm employs a novel primitive cell construction to enable it to analyze complex rectangular geometries, including inserts, with a two-dimensional, finite difference solution method. The analysis was applied to foaming of polyurethane in a rectangular cavity. The predicted skin thickness was found to be in good agreement with actual structural foam parts. Foaming as a function of cavity thickness was also treated. The algorithm Is useful for understanding and interpreting nonlinear phenomena of rapid, exothermic polymerizations such as foam formation adjacent to the mold wall or around a metal insert. The results can be used to formulate design guidelines for achieving desired skin/core thicknesses as a function of design, material, and process parameters.     

Numerical optimization of bipolar plates and gas diffusion layers for PEM fuel cells

This paper is devoted to the numerical optimization of the dimensions of channels and current transfer ribs of bipolar plates as well as the thickness and porosity of gas diffusion layers. A mathematical model of the transfer processes in a PEM fuel cell has been developed for this purpose. The results are compared with experimental data. Recommendations of the values of operating parameters and some design requirements to increase PEM fuel cell efficiency are suggested.This paper was originally Presented at the CHISA Congress, Prague, August 2004.An erratum to this article can be found at     

Pilot scale process for hydrodimerization of dimethyl maleate

A pilot scale process is described for the electrochemical hydrodimerization of dimethyl maleate to tetramethyl butanetetracarboxylate. The reaction is performed in an undivided bipolar cell using graphite electrodes, methanol as the solvent and sodium acetate as the supporting electrolyte. Several hundred kilograms of product were formed. Electrode lifetimes of four hundred hours were achieved with reasonable selectivity (70%) to the desired product. Dimethyl succinate is a major (20+%) byproduct along with minor quantities of dimethyl methoxysuccinate.     

Preliminary design and simulation of a microstructured reactor for production of synthesis gas by steam methane reforming

The present study considers the potentials of the well-known production of syngas by steam methane reforming (SMR), by operation within microstructured reactors. The model of a microchannel reactor is developed, including very fast kinetic reaction rates on the coated catalytic walls of the reactor module. By varying the characteristic dimensions of the channels, and considering technical constraints on the design and operating conditions, the results demonstrate that the SMR reactor can be drastically miniaturized while maintaining its productivity without any additional pressure drop. Furthermore, by reducing the channel characteristic dimensions, it is possible to suppress heat and mass-transfer limitations enabling SMR reactor operation at thermodynamic equilibrium. A fast method for preliminary design of microstructured heat-exchanger reactors is developed, that enables to identify the optimal channels number and heat power needed to reach process specifications.     

间歇与半间歇反应热失控危险性评估方法

针对间歇、半间歇反应器中频繁更换物系和/或反应工艺,受时间和经济条件限制往往不可能对发生在其中的反应动力学进行深入研究的特点,建立适用于它们的热失控危险评估方法具有重要意义。本文对此做了简要的综述并且认为,尽管迄今还没有普适性的方法,但是对于某些类型的重要反应,安全界限图方法和反应失控情景分析方法还是较为适用的。前者虽然涉及参数较多,且没有考虑高温下物料二次分解的可能性,但能按照反应结果将量纲1操作参数平面划分为无积累、反应失控、未充分引发及无害4个子区域,从而可以先验地获取更多的信息;后者虽然忽略了均相与非均相反应的不同,但该方法可对一定工艺条件下目标反应失控和二次分解反应进行分析评估,简单易行,考虑更全面。     

Controller design and performance analysis for a reactive extrusion process

This paper presents the design and analysis of a process control strategy for a reactive extrusion polypropylene degradation process. The primary control objective is to continuously produce polypropylene with desired properties (viscosity) despite variations in the properties of the feed material. The viscosity of the polypropylene, measured using an In-line Wedge Rheometer, is controlled by manipulating the feed concentration of the peroxide which acts as the initiator for the degradation reaction. An empirical model of the reactive degradation process is developed which describes the process dynamics and the characteristic process disturbances. Minimum variance (MV), constrained minimum variance (CMV), and pole placement (PP) controllers are first evaluated and compared in simulation. Then, a pole placement controller is implemented on the actual reactive extrusion process, with results being presented for the response of the controlled process to load disturbances due to feed material changes.     

Novel bipolar electrodes for battery applications

A novel bipolar graphite felt electrode for use in redox flow batteries and other electrochemical systems is described. The new electrode features a unique approach in the design of bipolar electrodes, employing carbon black free, nonconductive polymer materials as substrates. This innovation allows a dramatic reduction of processing time and cost compared to conventional carbon polymer composite electrodes used in bipolar battery systems. The conductivity of the new electrode assembly is similar to that of conventional bipolar electrodes, however, it shows significant improvements in mechanical properties. The functionality of these novel electrodes has been evaluated in the vanadium redox battery application and the results show comparable performance with conventional composite materials. An important operational advantage, however, is that side reactions leading to the deterioration of conductive filler in the electrode substrate material (i.e., electrode delamination due to CO₂-evolution) during cell overcharging are eliminated, making these electrodes more durable than the conventional designs. To date, these bipolar electrodes have been applied in vanadium redox cells but their design and properties promise further applications in a range of other redox flow batteries and bipolar electrochemical cell systems.     

Application of Polyimide-based Microfluidic Devices on Acid-catalyzed Hydrolysis of Dimethoxypropane

Microfluidic devices intensify transport phenomena and can improve chemical processes. New manufacturing processes and materials are perpetually developed due to constantly growing interest in process intensification. In this contribution, the authors present the design and application of polyimide-foil-based microfluidic mixing devices manufactured by reactive ion etching. As appropriate model reaction system, acid-catalyzed 2,2-dimethoxypropane (DMP) hydrolysis was chosen and investigated in three different mixing structure with varying flow rate. Energy dissipation rates were calculated to estimate mixing performances. The results show good mixing quality for Reynolds numbers between 10 and 100 and similar mixing times scales for all investigated microstructured mixers.     

Three-Dimensional Solar Cell Finite-Element Sintering Simulation

The sintering process is ubiquitous in manufacturing, but the design-oriented modeling of sintering has presented considerable challenges. This type of modeling is necessary to be able to predict deformation and thus design appropriate powder compacts so that after they are sintered, the desired dimensions will be achieved. Currently this is done through a costly and time-consuming trial and error process. In our research, an application of the Skorohod–Olevsky viscous sintering constitutive equation in a finite-element (FE) model is developed and used to model solar cell manufacturing. Experimental measurements are used to determine the properties of the solar cell materials, and these are used to calculate the parameters for the FE model. Simulation results are compared with experimental data and analysis has been made to evaluate the adequacy and usefulness of this approach.     

Fundamentals towards a Modular Microstructured Production Plant

For years, microtechnology is being considered as an emerging technique for chemical engineering tasks to overcome safety issues corresponding to high volumes and gaining higher selectivities and yields in reaction technology. Whereas in reaction technology a broad variety of microstructured equipment is available, in product purification/separation adequate equipment is missing. Research is focused on modular fast and flexible smaller production plants being operated continuously instead of batchwise in order to reduce engineering efforts and time‐to‐process. To cope with these demands, an appropriate definition of modules, which could be easily chosen and combined, is inevitable. In addition, these modules have to be well characterized concerning fluid dynamics and separation performance. This paper focuses on the characterization of available modules/devices. A standard method and analysis of the results concerning manufacturing accuracy and operation range is proposed. Miniplant technology is described as an efficient tool to validate process concepts proposed by process simulation studies. Necessary model parameters are determined for industrial complex mixtures in miniaturized laboratory equipment. Parameters are calculated model based to gain maximal accuracy. State of the art of miniplant technology is described and basic characteristic data are presented.     

The application of robust and non-interacting control schemes to a heat-exchanger stirred tank process

An experimental study involving the digital computer implementation of four multivariable control schemes to a heat-exchanger stirred process has been performed. The control schemes varied in their complexity and in the amount of process information required for their design. The analysis of the experimental data shows how each controller handled the asymmetric non-linearity and dead times inherent in the process. The development of the theory shows why the best control was not always achieved with the most sophisticated controller. The controllers are suitable for industrial applications.     

双极膜电渗析处理生物质水解液的过程性能研究

在由双极膜和阴离子交换膜组成的两室双极膜电渗析装置中,研究了生物质水解液糖、酸分离和酸回收的过程性能。考察了不同膜对、进料浓度、电流密度、处理室循环流量及操作温度等因素对于处理水解液过程中的电流效率和平均功耗的影响。结果表明,由BP-1双极膜与A501SB阴离子交换膜组成的膜对的性能最佳;过程的电流效率随进料液酸浓度的增大而下降,过高酸浓度的水解液进料对电渗析分离过程不利;较高操作电流密度条件下电流效率高,利于降低功耗,本装置的处理室适宜循环流量为30.0 mL/m in;操作温度的升高,对提高电流效率作用不明显,但利于降低平均功耗,本实验装置的合适操作温度为35℃。     

The application of robust and non-interacting control schemes to a heat-exchanger stirred tank process

An experimental study involving the digital computer implementation of four multivariable control schemes to a heat-exchanger stirred process has been performed. The control schemes varied in their complexity and in the amount of process information required for their design. The analysis of the experimental data shows how each controller handled the asymmetric non-linearity and dead times inherent in the process. The development of the theory shows why the best control was not always achieved with the most sophisticated controller. The controllers are suitable for industrial applications.     

Reduction of 2-nitropropane in an undivided,flooded, bipolar cell

As one model reaction in the study of the effect of contacting patterns on the overall specificity of electrosynthetic reactions, 2-nitropropane has been reduced to isopropylhydroxylamine and isopropylamine in an undivided, flooded, bipolar cell. Even though this cell was expected to be unfavourable for the overall reaction it was found that high space-time yields and current efficiencies could be obtained with a suitable choice of contacting pattern.