Automated microreactors

The catalysts were tested for their CO oxidation activity in an automated microreactor apparatus. The catalysts were tested at space velocities of 7,000 -60,000 hr . A small quantity of catalyst (typically 0.1 - 0.5 g.) was supported on a frit in a quartz microreactor. The composition of the gases to the inlet of the reactor was controlled by mass flow controllers and was CO = 50 ppm, CO2 = 0, or 7,000 ppm, HjO = 40% relative humidity (at 25°C), balance air. These conditions are typical of conditions found in spacecraft cabin atmospheres. The temperature of the catalyst bed was measured with a thermocouple placed half way into the catalyst bed, and controlled using a temperature controller. The inlet and outlet CO/CO2 concentrations were measured by non-dispersive infrared (NDIR) monitors. 

Many speciahzed laboratory reactors and operating conditions have been used. Sinfelt has alternately passed reactants and inert materials through a tubular-flow reactor. This mode of operation is advantageous when the activity of the fixed bed of catalyst pellets changes with time. A system in which the reactants flow through a porous semiconductor catalyst, heated inductively, has been proposed for studying the kinetics of high-temperature (500 to 2000°C) reactions. An automated microreactor... 

In another example of application of the simplex method, McMullen et cd. [38] demonstrated the rapid optimization and scaling of a Heck reaction using an automated microreactor system with HPLC monitoring and feedback control. Optimal reaction conditions in the microreactor were determined after 19 automated experiments and required a relatively small amount of starting material. The reaction was then successfully scaled up 50-fold from a microreactor to a Coming meso-scale glass reactor using the optimal conditions determined by the microreactor system. 

FIGURE 6.4. Illustration of nitrate esters synthesized in an automated microreactor. 

Integrating chemical analysis methods and physical sensors with microreactors enables monitoring of reaction conditions and composition. This ability renders instrumented microreactors powerful tools for determining chemical kinetics and identifying optimal conditions for chemical reactions. The latter can be achieved by automated feedback-controlled optimization of reaction conditions, which greatly reduces time and materials costs associated with the development of chemical synthesis procedures. 

One of the most successful applications of microsystem technology is the use of pTAS in diagnostics [332-335]. Microreactors have been integrated into automated analytical systems, which eliminate errors associated with manual protocols. Furthermore microreactors can be coupled with numerous detection techniques and pretreatment of samples can be carried out on the chip. In addition, analytical systems that comprise microreactors are expected to display outstanding reproducibility by replacing batch iterative steps and discrete sample treatment by flow injection systems. The possibility of performing similar analyses in parallel is an attractive feature for screening and routine use. 

Scheme4.88 Microfluidic system for MALDI protein analysis, (a) automated sample pretreatment and injection (b) microreactor (c) microdispenser used to deposit sample into nanovials (d) shallow nanovials on the MALDI target plate and (e) automated MALDI-ToF-MS analysis. Reprinted with permission from [345]. Copyright 2000 American Chemical Society.

In comparison to the conventional automated synthesis, the radiochemical yield and purity of the compound obtained by microreactor processing was higher and also had shorter synthesis time [21]. Multiple doses of2-deoxy-2-[18F]fluoro-D-glucose for positron emission tomography imaging studies in mice were prepared. Today, 2-deoxy-2-[18F]fluoro-D-glucose is routinely produced in about 50 min with the use of... 

Miniaturized near-infrared sensors were developed and implemented for online analysis and automated process control to also meet the safety requirements for handling of ozone and halogenating agents [49,50]. A target is to reduce the time from process idea to production (time-to-market) as well as development costs and costs for installation of the production unit. As pharmaceutical industry relies on the manufacture of many different products on smaller scale, and intermediates in quantities ranging from some kilograms to tons per year a modular approach toward a multipurpose microreactor plant is demanded. 

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. 

Small-scale combinatorial chemistry for library and analogue generation is easily automated with microreactors, using similar technology to that used for automated hplc, where sequential syntheses can be carried out on the same chip , for example in the preparation of analogues of ciprofloxacin. ... 

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