Chemical reactors, miniaturization

Original citation Miniature chemical reactors will pave the way for the future. These reactors will cut today s monster chemical plants down to the size of a car, with huge financial and environmental gains [219],... 

Tonkovich, A. L. Y, Zilka, J. L., Powell, M. R., Gall, C. J., The catalytic partial oxidation of methane in a micro-channel chemical reactor, in Ehrfeld, W, Rinard, I. H., Wegeng, R. S. (Eds.), Process Miniaturization 2nd International Conference on Microreaction Technology, IMRET 2, Topical Conf. Preprints, pp. 45-53, AIChE, New Orleans (1998). 

The silicon chip as a miniaturized chemical reactor. Courtesy of Felice Frankel. 

Batteries are miniature chemical reactors that convert chemical energy into electrical energy on demand. The ihermodynainics of battery systems follow directly from that for hulk chemical reactions. For the general teaction... 

Many potential applications are under study. Miniature chemical reactors could be used for portable applications in which they provide advantages of rapid startup and shutdown and of increased safety (intensification by requiring only small quantities of hazardous materials). The development of chip-scale chemical and biological analysis systems has the potential to reduce the time and cost associated with conventional laboratory methods. These devices could be used as portable analysis systems for detection of hazardous chemicals in air and water. There is considerable interest in using a microreactor to provide in situ production of hydrogen for small-scale fuel-cell power applications by conducting a reformation reaction from some liquid hydrocarbon raw material (e.g., methanol). 

The field of chemical process miniaturization is growing at a rapid pace with promising improvements in process control, product quality, and safety, (1,2). Microreactors typically have fluidic conduits or channels on the order of tens to hundreds of micrometers. With large surface area-to-volume ratios, rapid heat and mass transfer can be accomplished with accompanying improvements in yield and selectivity in reactive systems. Microscale devices are also being examined as a platform for traditional unit operations such as membrane reactors in which a rapid removal of reaction-inhibiting products can significantly boost product yields (3-6). 

Yu, H., Sethu, R, Chan, T., Kroutchinina, N., Blackwell, J., Mastrangelo, C.H., Grodzinski, P., A miniaturized and integrated plastic thermal chemical reactor for genetic analysis. Micro Total Analysis Systems, Proceedings of the 4th [iTAS Symposium, Enschede, Netherlands, May 14-18, 2000, 545-548. 

The interaction between reactor miniaturization and catalyst nanotailoring to achieve an effective PI has been emphasized by Charpentier [28] and Dautzen-berg [29]. The role of membranes in PI has been discussed by Drioli ef al. [30]. This short overview of the recent state-of-the-art, although limited to reviews published in the last few years, evidences the intense research effort and broad-range type of applications for PI, from refinery and petrochemistry to biotechnology, fine and specialty chemical production. 

Micro reactor, a device consisting of a network of micron-sized chatmels connected to a series of reservoirs containing chemical reagents and products to form the complete device with overall dimensions of a few centimeters. The miniaturization of chemical reactors offers many fundamental and practical advantages, in particular the environmental benefits. The first example of multi-step peptide synthesis in a micro reactor was described using simple model reactions [P. Watts et al. Tetrahedron 2002, 58, 5427 S. J. Haswell, P. Watts, Green Chemistry 2003, 5, 240]. 

Transport phenomena are crudal in the scale-up of conventional, large-scale chemical reactors because many processes are heat and/or mass transfer controlled. Since transport coeflEcients are typically inversely proportional to the characteristic dimension of the system, miniaturization of chemical systems leads to a substantial increase in transport rates. This increase in turn enhances the overall rate of processes that are transport limited, leading to considerable process intensification, i.e. the same throughput can be achieved with a much smaller device and thus with much lower capital. Alternatively, much higher throughput can be achieved using a system of the same size as a conventional one, but made up of many small components (scaling out). 

In recent years, research activities have paid increasing attention to reactions on a very small scale. The development of manufacturing technology has also enabled the production of miniature components for chemical reactor technology. Microstructured or microchannel reactors are called microreactors. They can also be defined as miniaturized reaction systems. The channel dimensions in microreactors are typically 50 Jim to 2 mm. Microreactor manufacturers provide microstructured mixers, heat exchangers. 

Dream reactions can be performed using chemical micro process engineering, e.g., via direct routes from hazardous elements [18]. The direct fluorination starting from elemental fluorine was performed both on aromatics and aliphatics, avoiding the circuitous Anthraquinone process. While the direct fluorination needs hours in a laboratory bubble column, it is completed within seconds or even milliseconds when using a miniature bubble column. Conversions with the volatile and explosive diazomethane, commonly used for methylation, have been conducted safely as well with micro-reactors in a continuous mode. 

Among the hazardous chemical weapons scheduled class 1-3, methyl isocyanate becoming more and more important as a precursor [83]. This is just one among a number of substances which could be made via micro-reactor synthesis. Especially in the case of so-called binary weapons, where two relatively harmless substances are mixed to give a weapon, on-site mixing is demanded this can be accomplished with high performance by micro reactors. Pocket-sized miniature plants can neither be monitored nor detected. 

Die Fabrik auf dem Chip, Spektrum der Wissenschafi, October 2002 Miniaturization and modularization of parts of future chemical apparatus general advantages of micro flow expert opinions specialty and fine chemical applications leading position of German technology flexible manufacture large-capacity micro reactors reformers for small-capacity applications compatible and automated micro-reaction systems process-control systems temperature and pressure sensors [209]. 

Miniaturization and parallelization key approaches for drug development apparatus for combinatorial chemistry UHTS 1536 titer-plate format modular construction of apparatus applications of UHTS fine-chemical synthesis by micro reactors numbering-up nature as model general advantages of micro flow vision of plants-on-a-desk [233]. 

Lu H, Schmidt MA, Jensen KF (2001) Photochemical Reactions and On-Line UV Detection in Microfabricated Reactors. Lab Chip 1 22-28 Manz A, Harrison DJ, Verpoorte EMJ, Fettinger JC, Ludi H, Widmer HM (1991) Miniaturization of Chemical-Analysis Systems - A Look into next Century Technology or just a Fashionable Craze. Chimia 45 103-105 McCreedy T (1999) Reducing the Risks of Synthesis. Chem Ind 15 588-590 McCreedy T (2000) Fabrication Techniques and Materials Commonly Used for the Production of Microreactors and Micro Total Analytical Systems. Trac Trends Anal Chem 19 396-401... 

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