Applications of Membrane Microreactors

As mentioned above, MMRs benefit from fast and thermodynamically limited reactions, for which mass transfer limits the reaction processes to a large extent. Owing to their compact features and high degree of control, MMRs are especially suitable for portable chemical processing. Table 8.1 summarizes typical applications of MMRs for catalytic reactions. 

Pd-based membranes possess high hydrogen permeation fluxes and infinite hydrogen selectivity, and have found considerable application in a variety of dehydrogenation reactions [40]. Applying microchannels in the membrane 

Annular tube Pd/AljO, Dehydrogenation Yield increased [29] 

Plate with coated Pd-Ag Partial oxidation Yh2=34.2% with [38] 

Stainless steel plate ZSM-5 and/ Knoevenagel Supra-equilibrium [3, 28] 

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The application of zeolite membranes in microreactors is still in an early stage of development, and suffers sometimes from unexpected problems arising from template removal [70]. However, several application examples of zeolite membranes in microstructured devices have been demonstrated yielding similar advantages as were to be expected from experiences on the macroscale. Because of the high surface to volume ratio of microreactors, the application of zeolite membranes in these systems has great potential. 

The efforts and advances during the last 15 years in zeolite membrane and coating research have made it possible to synthesize many zeolitic and related-type materials on a wide variety of supports of different composition, geometry, and structure and also to predict their transport properties. Additionally, the widely exploited adsorption and catalytic properties of zeolites have undoubtedly opened up their scope of application beyond traditional separation and pervaporation processes. As a matter-of-fact, zeolite membranes have already been used in the field of membrane reactors (chemical specialties and commodities) and microchemical systems (microreactors, microseparators, and microsensors). 

Abstract Process intensification (PI) is the future direction for the chemical and process industries and in this chapter, two key technologies to achieve this are discussed microreactors and so-caUed membrane microreactors (MMRs).There is great potential to enhance the overall efficiency of microreactors by integrating them with membrane technologies to make MMRs and there are tremendous opportunities for the application of MMRs in many fields. This chapter reviews microreactor design, fabrication and apphcations as well as materials for micromembranes (MM). The integration of MMs with microreactors and the applications of the resulting MMRs are then discussed. 

Ye S Y, Tanaka S, Esashi M, Hamakawa S, Hanaoka T and Miznkami F (2005), Thin palladium membrane microreactor with porons silicon support and their application in hydrogenation reaction , Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. Transducers 05. The 13th International Conference, 2,2078-2082. 

Rahman, M.A., Garcia-Garcia, F.R. and Li, K. (2012) Development of a catalytic hollow fibre membrane microreactor as a microreformer unit for automotive application./oMriw/ of Membrane Science, 390/391, 68-75. 

Photocatalytic membranes are mentioned in the literature as potentially interesting for a number of applications. Here, the membrane acts in the first place as a transparent storage medium for reactants, i.e., as a transparent microreactor system. 

Isobaric applications in the continuum regime, making use of molecular bulk diffusion and/or some viscous flow are found in catalytic membrane reactors. The membrane is used here as an intermediating wall or as a system of microreactors [29,46]. For this reason some attention will be paid to the general description of mass transport, which will also be used in Sections 9.4 and 9.5. 

Besides the synthesis of bulk polymers, microreactor technology is also used for more specialized polymerization applications such as the formation of polymer membranes or particles [119, 141-146] Bouqey et al. [142] synthesized monodisperse and size-controlled polymer particles from emulsions polymerization under UV irradiation in a microfluidic system. By incorporating a functional comonomer, polymer microparticles bearing reactive groups on their surface were obtained, which could be linked together to form polymer beads necklaces. The ability to confine and position the boundary between immiscible liquids inside microchannels was utilized by Beebe and coworkers [145] and Kitamori and coworkers [146] for the fabrication of semipermeable polyamide membranes in a microfluidic chip via interfacial polycondensation. 

Hence, their application field is not only restricted to their use in gas separation, pervaporation, and membrane reactors, but are also applicable in microscale devices (microreactors, microseparators, microvalves, microneedles, etc.) and for the preparation of functional materials (adsorbents for pollutant removal, controlled release systems, bactericidal, anticorrosive or antirefiective coatings, chemical sensors, and so on). 

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