Microreactor focusing

GlaxoSmithKline Pharmaceuticals in Harlow, UK, performed an enamine synthesis using a microchip reactor under electroosmotic flow conditions [20]. The aim was a much higher research on enamine formation in microreactors focused on eliminating the need of using Lewis acid catalysts [21]. In addition, operation under mild conditions such as room-temperature processing was favored. 

Examples of using metal, polymer, and glass microreactors appear in other chapters of this volume. The present chapter focuses on microreactors created in silicon, a material that has high mechanical strength,... 

Researchers at BASF have shown that microreactors can be utilized that give access to operating conditions that cannot be realized by means of macroscopic equipment. They succeeded in improving yield and selectivity in a highly exothermal two-phase reaction in connection with the synthesis of a vitamin precursor. At Degussa company, a microreactor test facility for proprietary reactions is under construction. The major focus in this context is the implementation of microreaction devices as powerful tools for process development and, in particular, for the evaluation of new reaction pathways. 

In an application-focused work, Gmbbs and coworkers developed a microreactor for the continuous-flow ethenolysis of methyl oleate [59], This... 

In this chapter the focus will be on the application of electrical fields in microreactors, and the potential of such systems for chemical synthesis will be outlined. The end of the chapter will give an overview of less-studied concepts, like electronic control of surface chemistry, and will discuss the opportunities offered by nanotechnology for achieving such control. 

Novel applications have been developed from the combination of microreactor technology and nonequilibrium microplasma chemistry. Here we discuss a selection from the recent literature on this topic to illustrate several main trends. We will focus on microplasmas in confined microchannels for the purpose of chemical synthesis and environmental applications. 

Baxendale et al. (2008) reported a bifurcated approach to the synthesis of thiazoles and imidazoles by coupling a glass microreactor and a packed-bed reactor to achieve a base-mediated condensation reaction. As Scheme 32 illustrates, reactions focused on the use of ethyl isocyanoacetate 123, as the cyanide source, with variations made via the isothiocyanate reagent, as illustrated in Table 13. 

Exploitation of liquid-liquid microreactor in organic synthesis offers attractive advantages, including the reduction of diffusion path lengths to maximize the rate of mass transfer and reaction rates. Despite the advantages, interest in liquid-liquid micro reactors did not take off until recently, perhaps because of the complication of flow pattern manipulation combined with the limited numbers of liquid-liquid reactions. Initial interest focused on the control of parameters responsible for variation in flow patterns to engineer microemulsions or droplets. However, it was soon realized that liquid-liquid microdevices are more than just a tool for controlling flow patterns and further interest developed. 

In this chapter, we will focus on those bioorganic reactions in which biocatalysts, in particular, play a crucial role. We will not discuss peptide or natural product synthesis, as conventional organic chemistry will be covered by other chapters in this book. Also the discussion of the development of DN A chips, certainly one of the most exciting developments in the field of pTAS, is beyond the scope of this chapter, and the interested reader is referred to some excellent reviews [330,331], First, the application of bioorganic chemistry in diagnostics will be discussed. This will be followed by a discussion on biocatalysis in microreactors. Finally, the recent development of cells on a chip is highlighted. 

The German public funded project NEMESIS focuses on the design and development of microreactors for the synthesis of ionic liquids at pilot scale [52], Scientific objectives are to increase the yield of the corresponding ionic liquid as well as to decrease reaction time from hours up to days currently. Ionic liquids, a new innovative class of materials, are synthesized using microreaction technology. Possible application fields are their use as electrolytes for the elaborate deposition of metals. A concept for regeneration of the electrolyte is also considered. 

Dow Chemical in Midland, USA, the microprocess technologist Velocys in Plain City, USA, and PNNL in Richland, USA, as research institute in microreactor technology have a public funded project on high-intensity production of ethylene and other olefins by oxidation such as the formation of ethylene from ethane [1], A two-step reactor engineering is performed, starting with a bench-scale reactor with microchannel dimensions equal to the latter commercial unit and followed by numbering to the latter. An economic analysis with focus on reactor costs and energy consumption completes the project. 

Many strategies have been and are still being developed to access oligosaccharides by chemical synthesis. This chapter focuses on recent developments in the automated solid-phase synthesis of oligosaccharides and emphasizes the recent advances of novel microreactor techniques for carbohydrate synthesis. 

Recent reviews have provided systematic coverage of the enzymatic microreactors used in chemical analysis [4]. Considering that the focus of this chapter is biocatalytic synthesis, it does not consider the analytical applications and the reader is referred to the cited literature ([4] and references given therein). The use of microreactors for high-throughput kinetic characterization of enzymes is another very interesting application of the technology [8], which, for reasons of limited space, is not discussed herein. 

Hessel et al. [33] centered their book on the analysis of a series of specific examples, from gas- and liquid-phase, to gas/liquid-phase and liquid/liquid-phase reactions, where the use of a microreactor (or more generally microprocess technology) allows significantly enhance in performance. It is a very valuable source of examples taken from over 1500 publications analyzed. The recent book ofWirth [34] focuses instead on the analysis of the opportunities for organic synthesis and catalysis in the use of microreactor technology. 

At the beginning of microreactor research, many papers focused on establishing suitable micro fabrication and assembly techniques and having system integration, following the success stories of MEMS fabrication and packaging [15]. The main... 

Today, the use of microreactors for the synthesis of organic fine chemicals is just beginning to be invesdgated. A keynote lecture was presented with the focus on or-... 

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