Miniaturized reactor

As an alternative and complementary technique to the study of chemical materials by DTA, DSC, or ARC, the study of chemical processes in miniature reactors has been developed. Equipment which is sufficiently instrumented to permit full... 

We have already described the design of our miniature reactors, the overall concept and the details of the window seals (1,10). Briefly, the cell has a small volume, ca. 2ml, on grounds of both safety and cost (when using scXe ). It is constructed from stainless steel and can be filled from an external syr—- K ... 

One form of combinatorial chemistry involves parallel synthesis or array synthesis. In parallel synthesis, each new compound is formed in its own miniature reactor or well. If a new library is to contain 500 members, synthesis of the library will require 500 wells in the final step. For this reason, parallel synthesis is associated with the phrase one compound-one well. 

Zech, T., Claus, P., Honicke, D., Miniaturized reactors in combinatorial catalysis and high-throughput experimentation, Chimia 2002, 56, 611-620. 

More recently, microreactor technology has entered the field of biocatalysis enzymes are used for synthesis rather than for diagnostics. The concept behind the use of biocatalytic microreactor systems is in fact twofold. First, a miniaturized reactor allows an efficient use of small amounts of enzyme, when enzyme kinetics determination is involved. Second, the classical advantages of microreactors in synthesis, namely, better control over heat- and mass-transfer... 

Figure 3 shows a schematic view of a flow reactor. It is similar to the photochemical reactor previously described in [5] but the UV photolysis cell has been replaced by a 1 m. stainless steel coil in a heated oil bath. As before, FTIR is used to monitor the conversion and optimise the conversion of reactant to product. Using such a system (C5Me5)Mn(CO)2(C2H4) can be obtained in a high yield as in Scheme 1. We are now scaling up this miniature reactor to a technical scale, ultimately with the aim of carrying out solvent-free reactions on a kilogramme scale.

Fig. 4 Gas composition of pyrocatechol conversion (miniature reactor, 0.2 M Pyrocatechol, 600°C, 25 MPa, 0.0018 M KOH) as (unction of reaction time.

The accurate tuning and control of the reaction conditions lead to impressively high product selectivity and energy efficiency. Thus, MSRs are versatile tools for the development of sustainable processes. Further objectives of the application of miniaturized reactors concern the generation of chemical information, facilitation of catalyst development, optimization, and characterization of reaction kinetics. 

Table 3.2 Specific interfacial areas of selected conventional and miniaturized reactor types. (Data from Ref. [40].)...

Basically, microreactors are defined as miniaturized reactors to be used in continuous production processes. From an industrial point of view, the main advantages of production with the aid of microreactors compared to conventional production are as follows ... 

Microreactors Miniaturized reactors consist of fluidic components, with dimensions below 1 mm used for various purposes in chemical engineering [30]. Microreactors facilitate the performance of heat and mass transfer-limited reactions. Another important feature of microreactors is its safety aspect. 

A particularly convenient feature of this technique, by contrast with solution-phase synthesis, is that there is no need for multistep purification of the product because the by-products and debris are easily washed away from the solid support before proceeding to the next coupling cycle with a new amino acid. The solid support can be reacted with reagents in various types of apparatus it can be simply held in a tube sandwiched between porous frits whilst reagents are pumped past, or reagents can be injected into and sucked out of vials sealed with a rubber septum, or it can be treated in 96-well plate format blocks of miniature reactors. There are also several proprietory styles of solid support designed for convenience of use. 

Miniaturized bioreactors can be divided into two categories based on scale microreactors and nanoreactors. These bioreactors present several fundamental advantages and open new venues. Miniaturized reactors allow for bench-scale chemical and biochemical production, which can be used by researchers. They also allow for cost-effective production when smaller quantities of a chemical are required. Other larger bioreactors are often not feasible because the production is not cost effective if the product is not very valuable or if the production is not consistent or pure enough for higher value chemicals. Miniaturized bioreactors, however, provide a great deal of conpol over reaction kinetics and hydrodynamics. 

Novel bioreactors can be represented by many different designs and variations, but the most novel and promising approach may turn out to be miniaturized reactors. 

Novel mechanical or bubble-induced flow designs are not trendsetters nor do they solve many of the and gas-liquid mass transfer problems. Miniaturized reactors, however, could decrease process design and implementation signiflcantly. The numbering-up method for these reactors reduces the time and amount of work necessary for scale-up the process is determined for one experimental unit and then the unit is copied multiple times. The rest of the work is spent on the industrial and economic problems rather than hydrodynamic and gas-liquid mass transfer issues commonly found in scale-up issues for other bioreactors. 

Oxidative homocoupling of 4-hydroxy-3-methoxyphenylacetic acid using H2O2 is achieved using a miniaturized reactor having peroxidase immobilized on alumina surfaces to give 2,2 -dihydroxy-3,3 -dimethoxybiphenyl-5,5 -diacetic acid (Figure 7.14) [74]. 

Technically, this Is achieved e.g. by synthesis robots that are able to disperse reagents rapidly over hundreds of miniaturized reactors contained on a microtiter plate. If a few reactants of types 1,..., n are combined in many possible combinations, a combinatorial library of compounds is the result. After synthesis, the product library is searched or screened for the desired property. Often, screening also is performed automatically with high throughput rates, in which case we speak of high throughput screening (HTS). 

The use of miniaturized reactors with characteristic dimensions below about 1 mm, so-called microreactors, is also a currently interesting development. An overview of the basic principles of microreactors is given by Emig and Klemm (2005). Details are found in Hessel, Hardt, and Loewe (2004). Subsequently, short summaries of these new concepts based on the cited literature are given. 

The presented recent approaches impressively illustrate the (r)evolution of chemist s toolkits from flasks and beakers to miniaturized reactors with highly efficient and selective catalysts, inherently combined with separation techniques. 

Zech, T., Klein, J., Schunk, S.A., lohann, T., Schiith, R, Kleditzsch, S., and Deutschmann, O. Miniaturized reactor concepts and advanced analytics for primary screening in high-throughput experimentation, la High Throughput Analysis A Toolfor Combinatorial Materials Science, PotyraUo, R.A. and Amis, E.J., Eds. Kluwer Academic/Plenum Publishers Dordrecht, 2003. 

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