无机膜及无机膜反应器的发展和应用

无机膜具有强度高、孔径容易控制、化学性质稳定、热稳定性好、易再生和不易老化等优点,成为膜技术领域重要研究方向,膜反应器是它的应用之一。综述了无机膜的发展状况,包括无机膜的分类和最新研究,无机膜反应器的特点、类型和它的作用;重点介绍了无机膜的应用和无机膜反应器的分类及应用研究,并提出了实现其工业化的不足。     

微孔无机膜反应器研究

主要介绍了无机膜在化学反应中的应用－－膜反应器研究，对膜反应器的特点、类型、应用、影响因素以及与其它反应器的比较进行了评述，并对其应用前景进行了展望。     

Entwicklung membranunterstützter Reaktionsprozesse

The use of membrane technology is developping from the solely work-up of product and waste streams all the way to integration into processes. The membrane reactor offers, by analogy with biological cells, great possibilities for product-integrated environmental protection. Two principal areas of application of membranes in reactors are becoming apparent. Use for removal of products or by-products from bioreactors and the coupling with chemical reactions considered in this article. The first such membrane reactors served for the removal of water from esterification reaction mixtures. Significant advances for membrane reactor technology came with the recent development of membranes of enhanced selectivity and flow density as well as improved thermal and chemical stability. In addition to the availability of high-performance membranes, fundamental knowledge and methods are required to assure efficient reaction-engineering utilization of membrane reactors. This paper discusses fundamental concepts relating to the use of various membrane reactors in parallel, consecutive, and equilibrium reactions. In general, in the case of membrane-supported parallel reactions, controlled addition of reactant can raise the reaction selectivity. Selective removal of primary and side products from consecutive or equilibrium reactions can increase yields. Comparison of membrane-supported reactor types (batch, loop, and plug-flow membrane reactors) indicate that the membrane-supported loop reactor will prove most effective in the majority of cases thanks to its pronounced flexibility.     

Zeolite based films, membranes and membrane reactors: Progress and prospects

The integration of reaction and separation in catalytic membrane reactors has received increasing attention during the past 30 years. The combination promises to deliver more compact and less capital-intensive processes with substantial savings in energy consumption. With the advent of new inorganic materials and processing techniques, there has been renewed interest in exploiting the benefits of membranes in many industrial applications. Zeolite membranes, however, have only recently been considered for catalytic membrane reactor applications. Despite the significant recent interest in these types of membranes there are relatively few reports of the application of such membranes in high-temperature catalytic membrane reactor applications. This can be attributed to a number of limitations that still need to be addressed such as the relatively high price of membrane units, the difficulty of controlling the membrane thickness, permeance, high-temperature sealing, reproducibility and the dilemma of upscaling. A number of research efforts, with some degree of success have been directed to finding solutions to the remaining challenges. This review makes a critical assessment of what has been achieved in the past few years in terms of hurdles that still stand in the way of the successful implementation of zeolite membrane reactors in industry.     

Application of inorganic membranes in the alkali recovery process

In the mills with wheat straw as raw material in China, the high silica content of raw material resulted in a low ratio of alkali recovery and high maintenance cost for equipment. However, till now, little progress has been made on removal of silica in the alkali recovery process of wheat straw pulping. Many researchers have investigated the feasibility of UF/RO organic membranes to treat black liquor (BL), but the success of UF/RO membranes in practice was discouraging due to their short life-span and low flux. In this study a novel process, the membrane-alkali recovery process, was developed by applying an inorganic MF membrane in the alkali recovery process. The rejection performance of inorganic MF membranes on lignin, silica and sodium salts was investigated, and the feasibility of the membrane-alkali recovery process was discussed in detail. The experimental results showed that the inorganic membranes could efficiently reject 75% of lignin and 80% of silica. A running period of more than 40 days for a 0.2 μ membrane was achieved with the maximum flux, 5001/m²h, under the conditions of TMP 0.2 MPa, crossflow velocity 2.3 m/s, and temperature 30—60°C. This newly developed membrane-alkali recovery process could efficiently reject silica. The interference of silica on the alkali recovery process was greatly decreased. Lime sludge could be reused in the membrane-alkali recovery process while it was discharged in the conventional alkali recovery process. The function of the alkali recovery boiler in the membrane-alkali recovery process was emphasized on the chemical reactor while the conventional furnace was taken as a steam regenerator and also a chemical reactor. The capital and maintenance of the new furnace could be decreased, and the operation could be simple and convenient compared with the conventional furnace. Therefore, the membrane-alkali recovery process overcame many disadvantages of the conventional alkali recovery process and fully utilized the organics and inorganics in the BL.     

Ion-Exchange membrane processes for clean industrial chemistry

New uses of artificial selective membranes, particularly ion-exchange membranes, improve on traditional methods of treating liquid mixtures before, during or after chemical or biochemical reactions. With the correct choice of ion-exchange membrane in a membrane reactor, reactions can be performed in such a way that the main product is not contaminated by undesired byproducts. Recent examples, mainly in organic chemistry, are given for eight typical ion-exchange membrane reactors: electrodialysis (ED), electrometathesis (EMT), electro-ion substitution (EIS), electro-ion injection-extraction (EIIE), coupled counter-transport (CCT), electro-electrodialysis (EED), electrohydrolysis with bipolar membranes (EHBM), and catalysis with ion-exchange membrane (IEMC).     

Heat transfer and temperature profiles in flow-through catalytic membrane reactors

In flow-through membrane reactors, a porous membrane is used as a microstructured catalyst support, which provides for an intensive contact between reactants and catalyst. When performing exothermal gas phase reactions, large temperature differences between feed and permeate side are observed. This work systematically derives an axial temperature profile inside the inaccessible membrane pores by combining a one-dimensional reactor model of mass and energy balances with experimental measurements of reactor temperatures and conversion, applying ethene hydrogenation as a model reaction. It is shown, that the anodized membrane reactor can be regarded as isothermal under any operating conditions and the heat transfer mechanisms inside the membrane prove to be irrelevant for the resulting membrane temperature. By applying the derived heat transfer model to the performed ethene hydrogenation experiments, the reactor temperature can be predicted satisfactorily in the whole range of performed experiments.     

国外膜催化剂的研究与应用

对当前国外膜催化技术(包括膜催化剂和膜反应器)的研究和应用作了全面的评述。着重考察了无机膜(各种金属膜和合金膜、陶瓷膜、各种氧化物膜、玻璃膜以及复合膜等)的催化作用,分加氢、脱氢、共轭反应、氧化还原、C_1-化学中的膜催化等进行了综述。分析了苏联、日本和美国等国家发展膜催化技术的作法,对我国开展膜催化研究提出了建议。     

Economic feasibility of silica and palladium composite membranes for industrial dehydrogenation reactions

This article addresses the economic feasibility of silica and palladium composite membranes for gaseous dehydrogenation reaction schemes. Unlike other methodologies addressed so far, this work presents the economic assessment of dehydrogenation reaction schemes using a conceptual design based simulation methodology for the comparative economic assessment of membrane reactors with conventional reactors. The suggested methodology is applied to two industrially prominent reaction schemes namely styrene (from ethylbenzene) and propylene (from propane) production using silica and palladium composite membrane reactors. Various sub-cases studied in this work include the influence of membrane area per reaction zone volume, reaction zone temperature, reaction and permeation zone pressure, membrane thickness and sweep gas flow rate on process economics. Based on this work, the propylene production scheme is evaluated to provide 60–70% excess profits using membrane reactors when compared with the conventional reactor based technology. However, the gross profit profiles for both conventional reactor and membrane reactor configurations have been found to be similar for styrene production case. For all cases, the cost contribution of membranes and other auxiliary equipment is estimated not to exceed 20% of the total costs. In addition, similar economic performance has been observed for both silica and palladium membranes. Based on these studies, it has been concluded that the industrial applicability of membrane reactors is economically suitable for those dehydrogenation reactions that enable significant conversion enhancement with respect to the conventional reactor technologies.     

Catalysis with membranes or catalytic membranes?

This paper considers the application of inorganic membranes in conjunction with catalysis and discusses attempts which have been made to affect changes in the yields and product distributions in a number of catalytic reactions with a number of different conformations of catalyst and membrane. Various possible reactor conformations are first considered and then some results obtained for catalytically-active perm-selective membranes are presented to illustrate some of the problems encountered with such membranes. The use of non-perm-selective wall-and-tube reactors is then considered. Finally, the results of model calculations are presented which show that the most promising confirmation for the use of perm-selective membranes is one in which the membrane and catalyst are in separate units and external recirculation of reactants and products is carried out.     

Fuel Cells,Advanced Reactors and Smart Catalysis: The Exploitation of Ceramic Ion‐Conducting Membranes

Membrane reactors are of great interest in the chemical industries because they offer the possibility of improved yields, improved selectivities and more compact plant. However, a significant barrier to their uptake is the unavailability of membrane systems having the required performance at an acceptable cost. In this paper we will explore the use of one class of membrane that has the potential to deliver high performance at reasonable cost. Ion‐conducting ceramic membranes can be used in a wide range of high temperature applications including fuel cells, advanced reactors and even smart catalytic systems.     

Keramische Membranen: Materialien – Bauteile – potenzielle Anwendungen

Ceramic membranes can be divided into dense and porous membranes. The materials, microstructure, and manufacturing methods are described and insights into current research topics are given. By adapting the material properties and tailoring microstructures, membranes and components suitable for a variety of processes can be developed. In applications, a distinction can be made between pure gas separation and membrane reactors. In the latter ones, in addition to gas separation, a chemical reaction takes place on one or both sides of the membrane. Membrane reactors can be used to produce basic chemicals or synthetic fuels. The supply of gases can be of interest for power plants, cement, steel or glassworks as well as for the medical sector or for mobile applications.     

Progress in membrane gas–liquid reactors

Gas–liquid reactions are crucially important in chemical synthesis and industries. In recent years, membrane gas–liquid reactors have attracted great attentions due to their high selectivity, productivity and efficiency, and easy process control and scale‐up. Membrane gas–liquid reactors can be divided into three categories: dispersive membrane reactor, non‐dispersive membrane reactor and pore flowthrough reactor. The progress in membrane gas–liquid reactors, including features, applications, advantages and limits, is briefly reviewed. © 2012 Society of Chemical Industry     

Solid electrolyte membrane reactors: Status and trends

A survey of recently published research work on solid electrolyte (SE) membrane reactors is given, with focus on high-temperature oxygen ion conductors, high-temperature proton conductors and low-temperature proton conductors. In these three material classes, the current status and the future trends of membrane reactor development are briefly elucidated. SE membrane reactor principles are realized in gas sensors, fuel cells, electrolyzers and reactors for partial oxidation. In all these fields SE membranes are in contact with porous electrolyte layers at which anodic or cathodic electrochemical reactions take place. In the area of membrane reactors using high-temperature oxygen ion conductors, there is a trend towards lower operating temperatures on order to ensure stable long-term operation of the membrane materials, and to match the optimal temperature window of the applied catalysts. As a younger generation of ion conducting ceramics, high-temperature proton conductors offer new possibilities for the implementation of electrochemical membrane reactors. Finally, current trends in the application of low-temperature proton conductors being based on polymeric materials are discussed. These materials can not only be used for fuel cells but also as membranes in hydrogenation or oxidation reactors.     

Experimental study on the effects of gas permeation through flat membranes on the hydrodynamics in membrane-assisted fluidized beds

Recently, many novel reactor concepts based on membrane fluidized bed reactors have been proposed. In this work, the effects of gas permeation through flat membranes on the hydrodynamics in a pseudo-2D membrane-assisted gas–solid fluidized bed have been investigated experimentally. A combination of the non-invasive techniques (Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA)) was employed to simultaneously investigate solids phase and bubble phase properties in great detail. Counter-intuitively, addition of secondary gas via the membranes, that constituted the confining walls of a gas–solid suspension at conditions close to incipient fluidization, did not result in a larger, but in a smaller equivalent bubble diameter, while gas extraction on the other hand, resulted in a larger equivalent bubble diameter, although in this case the effect was less pronounced. This could be explained by changes in the larger scale particle circulation patterns due to gas extraction and addition via the membranes.     

Membrane reactors in chemical production processes and the application to the pervaporation-assisted esterification

When appropriate membrane was used for the assistance of chemical and biochemical equilibrium reactions, it is possible to enhance the yield and the purity of the reaction product by selectively adding educts or selectively removing products and to a lower the energy input and the reaction time compared to conventional process. In this paper a review on membrane reactors with special emphasis on membrane-assistance of esterification reactions and a continuous tube membrane reactor for the pervaporation-assistance of the esterification are presented. The heterogeneously catalyzed esterification of ethanol and acetic acid to ethyl acetate and water was investigated as a typical chemical equilibrium reaction. The selective and simultaneous water separation from the reaction mixture of the esterification with polyvinyl alcohol pervaporation membranes is considered to be an interesting process alternative to the conventional distillation process. Compared to the distillation process, for the pervaporation-assisted process a decrease of the energy input of over 75% and of the investment and operating coasts of over 50% each was calculated.     

Microwave‐Assisted Continuous‐Flow Reactor Based on a Ridged Waveguide

Microwave‐assisted continuous‐flow reactors (MCFRs) are a valuable alternative to conventional reactors for accelerating chemical reactions. However, despite several interesting applications, only little quantitative research has been conducted on the temperature uniformity of the heating load. With water as a common inorganic solvent, a novel MCFR type based on a special ridged waveguide for heating water is studied by optimizing some parameters of micropipes in order to achieve better temperature uniformity. Compared to the original reactor, the standard deviation of the electric field decreased significantly when using the optimized reactor under the same heating conditions while the average electric field density increased. The optimized results were verified by experiments.     

膜化学反应器及其应用进展

提出将膜化学反应器分为四 ：膜反应分离器、膜混合反应器、膜混合反应分离器和膜介观孔道反应器，并分别对各类反应器的特征、功能及其应用进行了评述。     

Simulations of the effect of hydrodynamic conditions and properties of membranes on the catalytic performance of a fluidized-bed membrane reactor for partial oxidation of methane

In a fluidized-bed membrane reactor the selectivity of separation can be controlled by influencing the hydrodynamics of the fluidized bed. In this reactor type, with the mass transport limitation between bubbles and the emulsion phase, even with the non-selective membranes, high selectivity of separation can be achieved. This opens the possibility for applications of membrane reactors for reaction systems for which selective membranes do not exist, e.g. when Knudsen-type membranes or form-selective separation can not be applied. This paper is aimed at explaining the interaction between the selectivity of separation and the hydrodynamics of the fluidized bed by means of simulations that were performed for a fluidized-bed membrane reactor for catalytic partial oxidation of methane.     

New Integrated Catalytic Membrane Processes for Enhanced Propylene and Polypropylene Production

Newly reported integrated processes are discussed for aliphatic (paraffin) hydrocarbon dehydrogenation into olefins and subsequent polymerization into polyolefins (e.g., propane to propylene to polypropylene, ethane to ethylene to polyethylene). Catalytic dehydrogenation membrane reactors (permreactors) made by inorganic or metal membranes are employed in conjunction with fluid bed polymerization reactors using coordination catalysts. The catalytic propane dehydrogenation is considered as a sample reaction in order to design an integrated process of enhanced propylene polymerization. Related kinetic experimental data of the propane dehydrogenation in a fixed bed type catalytic reactor is reviewed which indicates the molecular range of the produced C₁-C₃ hydrocarbons. Experimental membrane reactor conversion and yield data are also reviewed. Experimental data were obtained with catalytic membrane reactors using the same catalyst as the non-membrane reactor. Developed models are discussed in terms of the operation of the reactors through computational simulation, by varying key reactor and reaction parameters. The data show that it is effective for catalytic permreactors to provide streams of olefins to successive polymerization reactors for the end production of polyolefins (i.e., polypropylene, polyethylene) in homopolymer or copolymer form. Improved technical, economic, and environmental benefits are discussed from the implementation of these processes.