Applications of Microreactors

Watts P, Haswell SJ (2005) The Application of Microreactors for Organic Synthesis. Chem Soc Rev 34 235-246... 

W-Methyl-A/ -nitroso-p-toluenesulfonamide (MNTS) is an important precursor for the production of diazomethane. Diazomethane is then further converted to a range of useful molecules in the pharmaceutical and fine chemical industry [69]. Production of MNTS is a highly exothermic process and includes the presence of the extremely toxic materials. Stark et al. [70] have explored the application of microreactor technology for the production of this industrially valuable material, assuming that due to the efficient heat exchange and the closed system, microflow conditions provide a safer environment for these hazards. 

Despite the high specific surface areas, the amount of accessible catalyst remains low due to the limited thickness of the porous catalytic layer dictated by considerations such as the adhesion to the substrate. The susceptibility of the fine channels to blockage with solid impurities or deposits formed in the reaction, together with the problems of integrating connections with the external macroenvironments and ensuring uniform gas distribution between the individual channels, a prerequisite for numbering up, represent further questions that have to be resolved for the industrial application of microreactors to become practicable. 

None of the existing microfabrication techniques available cover the complete range of materials which might be of interest in the present case. The choice of the microfabrication method therefore selects the material to be applied and determines the range of temperature, pressure or solvents for the application. Material selection is therefore important when new applications of microreactors are envisaged. 

In the numbering-up technology, the same reaction is carried out in every microchannel. If different reagents are supplied in different combinations for all the microchannels, many different products can be obtained at once [52], This is another eagerly expected application of microreactors and it would be very effective, especially for combinatorial synthesis in drug discovery [8], For the... 

One application of microreactors that is likely to appear in commercial devices soon is in the generation of hydrogen for portable-power generation. The power needs of portable electronic devices increase every year. Advances in battery technology have not kept pace... 

Microreactor technology has also been applied in some reactions to be able to more accurately control the stereoselectivity of reactions. Skelton and coworkers have reported the application of microreactors for the Wittig reaction [14, 35], The authors used the microreactor to prepare the cis- and tr ns-nitrostilbene esters 19 and 20 using the Wittig reaction (Scheme 14.6). Several features such as stoichiometry and stereochemistry were investigated. When two equivalents of the aldehyde 22 to the phosphonium salt 21 were used in the reaction, a conversion of 70% was achieved. The microreactor demonstrated an increase in reaction efficiency of 10% over the traditional batch synthesis. The reaction stoichiometry... 

This imposes some restriction on potential applications of microreactors, particularly with regard to their use in heterogeneous catalysis (see below). Another interesting aspect of MRT is enhanced mass transfer due to dramatically lowered mixing times ( 1 s compared to some 10 s for conventional reactors) and short diffusion times to such an extent that the influence of mass transfer on the reaction kinetics can be almost neglected. 

Zhang, X.N., S. Stefanick, and F.J. Villani, Application of microreactor technology in process development. Organic Process Research and Development, 2004, 8 455-460. 

This entry introduces some applications of microreactors for nanoparticle preparation and growth analysis. 

Zhang X, Stefanick S and VUlani F J (2004), Application of Microreactor technology in Process Development , Org Proc Res Dev, 8,455-460. 

A. de Mello, R. Wootton, What is it good for Applications of microreactor technology for the fine chemical industry. Lab Chip 2002, 2, 7N-13N... 

The application of microreactors for the generation of metal nanoparticles is motivated from two aspects On the one hand, static micromixers allow very quick mixing of metal salt (complex) and reducing agent solution. On the other, rapid changes in temperature, pH or other parameters can be used for switching between nucleation and particle growth. 

The application of microreactors in emulsiflcation processes has been investigated in recent years. A detailed overview on this topic of emulsification in general can be found in Chapters 20 and 21. Here, the focus is only to outline the major traits which might be of interest with regard to the consumer goods industry. Emulsification is certainly currently the application area which shows the largest connection to that industry. 

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