Microreactors systems

Molten carbonate fuel cells Micro-electro-mechanical systems Microreactor Technology for Hydrogen and Electricity Micro-structured membranes for CO Clean-up Membrane reactor... 

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). 

In comparison to conventional reactor systems, microreactors are easier to scale up by numbering-up (external or internal numbering). Most microreactors are made from silicon wafer or Si bulk using traditional semiconductor microfabrication methods, whilst other materials such as ceramic, glass and stainless steel have also been used in their design. The design of microreactors made from these materials is based on the application type, thermal conductivity, mechanical, electrical and electronic properties of each material. 

Microfluidic systems (microreactors) provide great benefits, such as precise fluid-manipulation [1] and high controllability of rapid and difficult to control chemical reactions (see Part 2, Bulk and Fine Chemistry). Advantages of microreaction technology have been utilized in polymer chemistry notable examples include the synthesis of fine solid polymeric materials [2,3] and excellent control of exceptionally reactive polymerization through mainly radical and cationic polymerization reactions (see Chapters 13-15). Other polymerizations using microreaction technology are still in their infancy, vhich include step polymerization, that is, polycondensation and polyaddition and other non-radical polymerizations. 

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 authors developed a multi-layered microreactor system with a methanol reforma- to supply hydrogen for a small proton exchange membrane fiiel cell (PEMFC) to be used as a power source for portable electronic devices [6]. The microreactor consists of four units (a methanol reformer with catalytic combustor, a carbon monoxide remover, and two vaporizers), and was designed using thermal simulations to establish the rppropriate temperature distribution for each reaction, as shown in Fig. 3. 

Rensi, T. a., Nyquist, )., Microfabricated mini-chemical systems technical feasibility, in Ehreeld, W. (Ed.), Microsystem Technology for Chemical and Biological Microreactors, DECHEMA Monographs,... 

Lohf, a., Lowe, H., Hessel, V., Ehefeld, W., A standardized modular microreactor system, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 441 51 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Garcia-Egido, E., Wong, S. Y. E., A Hantzsch synthesis of 2-aminothiazoles performed in a microreactor system, in Ramsey, J. M., van den Berg, A. (Eds.), Micro Total Analysis Systems,... 

Ehreeld, W., Gebauer, K., Lowe, H., Richter, T., Synthesis of ethylene oxide in a catalytic microreactor system. Stud. 

Shaw, J., Turner, C., Miller, B., Harper, M., Reaction and transport coupling for liquid and liquid/gas microreactor systems, in Ehreeld, W., Rinaed,... 

JOVANOVIC, G., Sacrittichai, P., Toppinen, S., Microreactors systems for dechlorination of p-chlorophenol on palladium based metal support catalyst theory and experiment, in Proceedings of the 6th International Conference on Microreaction Technology, IMRET 6, 11-14 March 2002, pp. 314-325, AIChE Pub. No. 164, New Orleans (2002). 

At the initial stage of bulk copolymerization the reaction system represents the diluted solution of macromolecules in monomers. Every radical here is an individual microreactor with boundaries permeable to monomer molecules, whose concentrations in this microreactor are governed by the thermodynamic equilibrium whereas the polymer chain propagation is kinetically controlled. The evolution of the composition of a macroradical X under the increase of its length Z is described by the set of equations ... 

The NSR capability of the catalysts was investigated under transient conditions in a flow microreactor system with samples in the powder form. 

In each run, 120 mg of catalyst (75-100 xm) were used and a total flow rate by 200 cm3/min STP was maintained in the different phases. The flow microreactor system... 

Activities of the catalysts were measured on a microreactor. About 3 g of catalyst was charged into a reactor and heat-treated in nitrogen at reaction temperature. Acetic acid was added to the process and the reaction was initiated by switching nitrogen to ethylene. Reaction product analyses were performed by an online gas chromatograph equipped with a flame ionization detector (Perkin Elmer Auto System II). 

Carbon dioxide chemisorptions were carried out on a pulse-flow microreactor system with on-line gas chromatography using a thermal conductivity detector. The catalyst (0.4 g) was heated in flowing helium (40 cm3min ) to 723 K at 10 Kmin"1. The samples were held at this temperature for 2 hours before being cooled to room temperature and maintained in a helium flow. Pulses of gas (—1.53 x 10"5 moles) were introduced to the carrier gas from the sample loop. After passage through the catalyst bed the total contents of the pulse were analysed by GC and mass spectroscopy (ESS MS). 

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