Chemical synthesis, microreactor systems

Edelmann FT (1996) Rare Earth Complexes with Heteroallylic Ligands. 179 113 -148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Effenhauser CS (1998) Integrated Chip-Based Microcolumn Separation Systems. 194 51 - 82 Ehrfeld W, Hessel V, Lehr H (1998) Microreactors for Chemical Synthesis and Biotechnology -Current Developments and Future Applications. 194 233 - 252 Ekhart CW, see de Raadt A (1997) 187 157-186... 

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. 

Why is fast chemical synthesis needed The most appropriate answer to this question is because we can just do it with our present knowledge and technologies. Extremely fast reactions that are complete within a second used to be difficult to control on a preparative scale because we were using conventional macrobatch reactors. However, we are now able to conduct such reactions in a controlled manner with the aid of microflow systems constructed with micro-structured reactors and microreactor technology. 

The benefits of microreactors are many more ideal temperature exchange for gas phase reactions they enable the reaction process to take place in an electric field and the performance of complex catalytic reactions can be simplified [18]. These benefits will also provide access to novel structures. Additionally, the bottleneck caused by limited availability of unusual building blocks and scaffolds will be eased, or altogether eliminated, by microreactor operations and miniaturized screening formats. The advent of microreactor systems for chemical synthesis not only opens the door for direct integration of synthesis and screening, but also provides better access to novel compounds. 

Through years of development, the portfolio of applications of droplet-based microreactors has expanded from chemical kinetics to a wide spectrum of applications including protein crystallization [10, 67, 96-99] and modeling complex reaction networks [100-104]. Interfacial reaction at the oil/water interface has also been explored for chemical synthesis [105]. Another interesting area is using droplets as highly effective reaction system to prepare nanoparticles [94, 106-108]. 

There is a chance that continuous flow synthesis will see a similar development in chemical synthesis as was encoimtered in analytical chemistry when HPLC was introduced into the chemist s laboratory. In this context, microreactor technology and microfluid systems will also play an important role [66,67]. 

Continuous microreactor systems have gained a lot of interest in the field of organic synthesis as these possess enhanced mass and heat transfer properties. Microreactor technology also offers a contemporary way of conducting chemical reactions In a more sustainable fashion due to the miniaturization and increased safety, and also In a technically improved manner due to intensified process efficiency. Recent developments in this area related to the synthesis of heterocyclic compounds are recorded in this chapter. Also, telescoping, in which several subsequent reaction steps (with or without purification) can be achieved by connecting different reactors to each other, is covered. 

Systanix, Inc. has developed a scalable and adaptable system for chemical synthesis called SysFlo. With its patent-pending microreactor and catalyst technology, SysFlo s modular design enables highly efficient, on-demand chemical production while decreasing equipment footprint . 

Microreactor systems have since evolved from basic, single-step chemical reactions to more complicated multistep processes. Beider et al. (2006) claim to have made the first example of a microreactor that integrated synthesis, separation, and analysis on a single device [15]. The microfluidic chip fabricated from fused silica (as seen in Figure 1.4) was used to apply microchip electrophoresis to test the enantioselective biocatalysts that were created. The authors reported a separation of enantiomers within 90 s, highlighting the high throughput of such devices. 

According to the experts in the field of chemical synthesis, it is more preferable to use continuous process in microreactors for up to 70% of all chemical reactions [19]. Today, a lot of homogeneous reactions in liquid-liquid systems are investigated because they can be simply carried out in microreactors. Heterogeneous reaction systems, both liquid-liquid and gas-liquid, in microreactors are more and more intensively studied and find practical application. Special attention is given to catalytic processes as they dominate in chemical technology. 

Organic reaction systems using microcapsules and microreactors to perform chemical synthesis. Acc. Chem Res., 46, 327-338 (b) McQuade, D.T. 

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