Laboratory microreactor process development

Microreactor Laboratory-scale Process Developments for Future Industrial Use... 

A variety of microreactors for liquid-liquid reactions are available and have been described in literature. The adopted throughputs start from below the mLh level for analytical purposes. Micromixers for laboratory-scale process development or organic synthesis can handle flows from mLh to Lh . For the range from above 10 Lh up to tens of m h microstructured mixers are also available and some are already in production use. 

Thus, it is more flexible to run both reactions continuously [44]. A microreactor is used for the more demanding, highly exothermic reaction, whereas a static mixer is sufficient for the second reaction. After laboratory process development, a pilot phase... 

Especially in chemical and process development it can be of particular interest to use a microreactor, which has a known strategy for scale-up or scale-out There are different strategies for increasing the throughput from the laboratory-scale to pilot- or production-scale (Figure 3.3). 

However, as more systems become commercially available, the user will need to be aware of the potential for problems and understand measurements that can be used to characterize performance. As noted by Hickman and Sobeck in a recent chapter, in which they were interested in generating laboratory-based kinetic information for process development applications, the mixing characteristics in the microreactor need to be characterized to model the reaction chemistry [7]. 

Stainless steel is the material of choice for process chemistry. Consequently, stainless steel microreactors have been developed that include complete reactor process plants and modular systems. Reactor configurations have been tailored from a set of micromixers, heat exchangers, and tube reactors. The dimensions of these reactor systems are generally larger than those of glass and silicon reactors. These meso-scale reactors are primarily of interest for pilot-plant and fine-chemical applications, but are rather large for synthetic laboratories interested in reaction screening. The commercially available CYTOS Lab system (CPC 2007), offers reactor sizes with an internal volume of 1.1 ml and 0.1 ml, and modular microreactor systems (internal reactor volumes 0.5 ml to... 

The modern methods of three dimensional microfabrication have lead to the development of extremely miniaturized chemical and biotechnological systems. These so called microreactors represent novel approaches in respect of production flexibility and chemical reactions not yet applied in chemical processing. This has stimulated world-wide research in this field so that the technical feasibility of such devices has been demonstrated in the laboratory scale. 

Researchers at Johnson and Johnson have reported the use of microreactors in the drug development process. They utilized a commercially available CYTOS benchtop system, shown in Fig. 15, to examine several reactions. One such reaction was the highly exothermic reaction to form A-methoxycarbonyl-L-rert-leucine by the addition of methylchloroformate to L-tert leucine. Such highly exothermic reactions present safety hazards in large-scale systems. Utilizing the CYTOS system, they were able to perform this reaction in the laboratory and achieved 91% yield. ... 

Similarly, radiolytically produced radical cations can be stabilized in zeohtes and related materials. This possibility was exploited by spectroscopists to study the EPR of radical cations and some neutral radicals even before the development of inert matrices such as rare gases and freons for radical cation stabilization. Recently, work in our laboratory has developed the use of inert zeolites as microreactors to control radical cation reactions and to study radiation chemistry in heterogeneous systems. In the case of active catalysts, radiolysis can potentially produce radical cations of products as weU as starting material. Thus, like the spontaneous oxidation process described above, radiolysis combined with EPR permits a method of post-reaction analysis of products by in situ spectroscopy. 

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