Microreactor technique

The microreactor technique described by the authors offered 30 and 50 times higher STY values than the conventional tubular reactor and the slurry reactor, respectively, suggesting microreactors to be a successful technique in mass transfer controlled reactions. 

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. 

It seemed possible that the microreactor technique developed by Emmett... 

The catalytic work on the zeolites has been carried out using the pulse microreactor technique (4) on the following reactions cracking of cumene, isomerization of 1-butene to 2-butene, polymerization of ethylene, equilibration of hydrogen-deuterium gas, and the ortho-para hydrogen conversion. These reactions were studied as a function of replacement of sodium by ammonium ion and subsequent heat treatment of the material (3). Furthermore, in some cases a surface titration of the catalytic sites was used to determine not only the number of sites but also the activity per site. Measurements at different temperatures permitted the determination of the absolute rate at each temperature with subsequent calculation of the activation energy and the entropy factor. For cumene cracking, the number of active sites was found to be equal to the number of sodium ions replaced in the catalyst synthesis by ammonium ions up to about 50% replacement. This proved that the active sites were either Bronsted or Lewis acid sites or both. Physical defects such as strains in the crystals were thus eliminated and the... 

Two engineering-type methodological developments are worthy of mention in connection with SPC (i) the appHcation of microwaves (/rW) and (ii) the microreactor technique. Whereas, the /U.W technique is stiU in its infancy, the microreactor has reached technical-scale maturity. 

This plan had the best-documented experimental procedure using the microreactor technique so far encountered. The reaction solvent to limiting reagent mass ratio for each step is as follows ... 

Shorter timescales a microreactor technique to examine fast exchange... 

A Canadian firm, SBI Fine Chemicals, is out to prove that continuous microreactor techniques can also be used on a larger scale. For that purpose, SBI is building a biodiesel demonstration plant in Edmonton, Alberta, that can make 201 of the fuel per minute from a variety of vegetable oils [9]. 

Nace, D.M., "Catalytic cracking over crystalline aluminosilicates. II. Application of Microreactor Technique to Investigation of Structural Effects of Hydrocarbon reactants", Ind. Eng. Chem. Proc. Des. Dev., 8(1), 31-38 (1969b). 

The chain-growth polymerization that finds the widest industrial uses is radical polymerization. However, a carbon radical is typically highly reactive and has a shorter lifetime than a carbocation or a carbanion. Radial polymerization is thus difficult to control based on high-resolution reaction time control, which is effective for cationic and anionic polymerizations described in this chapter. In other words, by using a simple flow microreactor technique radical polymerization cannot be living... 

Reproducible measurements of absolute activity for sulfur dioxide oxidation catalysts are very difficult to obtain for a number of reasons, including the fact that the reaction is extremely fast. In addition, there are differences in techniques and reporting methods used by the various workers. Pulse microreactors have been used to study quantities of these catalysts as small as 500 mg (83). 

Microwave technology has now matured into an established technique in laboratory-scale organic synthesis. In addition, the application of microwave heating in microreactors is currently being investigated in organic synthesis reactions [9-11] and heterogeneous catalysis [12, 13]. However, most examples of microwave-assisted chemistry published until now have been performed on a... 

WoRZ, O., Jacket, K. P., Richter, T, Wole, A., Microreactors, new efficient tools for optimum reactor design. Microtechnologies and Miniaturization, Tools, Techniques and Novel Applications for the BioPharmaceutical Industry, IBC Global Conferences, London (1998). 

Richter, T, Eheeeld, W., Wole, A., Gruber, H. P., Woez, O., Microreactors in hifrdy corrosion- and heat-resistant materials fabricated by various micro-EDM techniques, in Proceedings of Microreaction Technology, 1st International Conference on Microreaction Technology, IMRET 1, 23-25 Eebruary 1997, Erankfurt/M. (1997). 

Lu H, Schmidt MA, Jensen KF (2001) Photochemical Reactions and On-Line UV Detection in Microfabricated Reactors. Lab Chip 1 22-28 Manz A, Harrison DJ, Verpoorte EMJ, Fettinger JC, Ludi H, Widmer HM (1991) Miniaturization of Chemical-Analysis Systems - A Look into next Century Technology or just a Fashionable Craze. Chimia 45 103-105 McCreedy T (1999) Reducing the Risks of Synthesis. Chem Ind 15 588-590 McCreedy T (2000) Fabrication Techniques and Materials Commonly Used for the Production of Microreactors and Micro Total Analytical Systems. Trac Trends Anal Chem 19 396-401... 

Each microreactor consists of a polymer-bound substrate and a radiofrequency encoded microchip enclosed within a small porous vessel. The radiofrequency tag allows the identity of the substrate contained within each microreactor to be established readily. Using this technology, the polymer-bound substrates 86 were individually elaborated, within separate microreactors, by sequential reactions with acids 87 and alcohols 88 in a similar way to the solution-phase processes [25c]. Each of the microreactors was then subjected to the tandem RCM resin-cleavage conditions employing initiator 3. The products from each microreactor were obtained as a mixture of four compounds (89-92). The library of analogs prepared by this technique was then screened for biological activity [25c]. 

Microreactors evolved from the process intensification concepts and microfabrication techniques developed for the microelectronics industry. Process intensification was pioneered in the 1970s, arguably by Imperial Chemical Industries (ICI) researcher Colin Ramshaw, who began developing technologies and approaches that considerably reduced the physical size of unit operations while maintaining their... 

To build an efficient and compact microreactor, the fabrication technique must allow for three-dimensional structures and the use of the appropriate materials, and the technique should be low cost. Since reactants and products must flow in and out of the device, traditional standard thin film techniques are not suitable for the reactor framework. However, thin film techniques are very useful for integration, surface preparation, sensor integration, and finishing or packaging. Fortunately, traditional thin film techniques can be modified for microreactor fabrication other techniques, which will be discussed below, are also available. 

A number of fabrication techniques meet the general requirements for constructing an efficient and compact microreactor. Popular methods include LIGA, wet and dry etching processes, micromachining, lamination, and soft lithography. 

---