Editing Microreactor (section)

==Benefits==
Using microreactors is somewhat different from using a glass vessel. These reactors may be a valuable tool in the hands of an experienced chemist or reaction engineer:

* Microreactors typically have [[Heat transfer coefficient|heat exchange coefficients]] of at least 1 megawatt per cubic meter per [[kelvin]], up to 500 MW&nbsp;m<sup>−3</sup>&nbsp;K<sup>−1</sup> <!-- see talk page re exponents in ChemEng -->vs. a few kilowatts in conventional glassware (1 L flask ~10&nbsp;kW&nbsp;m<sup>−3</sup>&nbsp;K<sup>−1</sup>). Thus, microreactors can remove heat much more efficiently than vessels and even critical reactions such as [[nitration]]s can be performed safely at high temperatures.<ref>{{cite journal |last1=Roberge |first1=D. M. |last2=Ducry |first2=L. |last3=Bieler |first3=N. |last4=Cretton |first4=P. |last5=Zimmermann |first5=B. |title=Microreactor Technology: A Revolution for the Fine Chemical and Pharmaceutical Industries? |journal=Chemical Engineering & Technology |date=March 2005 |volume=28 |issue=3 |pages=318–323 |doi=10.1002/ceat.200407128 }}</ref> Hot spot temperatures as well as the duration of high temperature exposition due to [[exothermic]]ity decreases remarkably. Thus, microreactors may allow better [[Chemical kinetics|kinetic]] investigations, because local temperature gradients affecting reaction rates are much smaller than in any batch vessel. Heating and cooling a microreactor is also much quicker and [[operating temperature]]s can be as low as −100&nbsp;°C. As a result of the superior heat transfer, reaction temperatures may be much higher than in conventional batch-reactors. Many low temperature reactions as organo-metal chemistry can be performed in microreactors at temperatures of −10&nbsp;°C rather than −50&nbsp;°C to −78&nbsp;°C as in laboratory glassware equipment.
* Microreactors are normally operated continuously. This allows the subsequent processing of unstable intermediates and avoids typical batch [[Work-up (chemistry)|workup]] delays. Especially low temperature chemistry with reaction times in the millisecond to second range are no longer stored for hours until dosing of reagents is finished and the next reaction step may be performed. This rapid work up avoids decay of precious intermediates and often allows better selectivities.<ref>{{cite journal |last1=Schwalbe |first1=Thomas |last2=Autze |first2=Volker |last3=Wille |first3=Gregor |title=Chemical Synthesis in Microreactors |journal=CHIMIA |date=November 2002 |volume=56 |issue=11 |pages=636 |doi=10.2533/000942902777679984 |doi-access=free }}</ref>
* Continuous operation and mixing causes a very different concentration profile when compared with a batch process. In a batch, [[reagent]] A is filled in and reagent B is slowly added. Thus, B encounters initially a high excess of A. In a microreactor, A and B are mixed nearly instantly and B won't be exposed to a large excess of A. This may be an advantage or disadvantage depending on the [[reaction mechanism]] - it is important to be aware of such different concentration profiles.
* Although a bench-top microreactor can synthesize chemicals only in small quantities, scale-up to industrial volumes is simply a process of multiplying the number of microchannels. In contrast, batch processes too often perform well on R&D bench-top level but fail at batch pilot plant level.<ref>{{cite journal |last1=Schwalbe |first1=Thomas |last2=Autze |first2=Volker |last3=Hohmann |first3=Michael |last4=Stirner |first4=Wolfgang |title=Novel Innovation Systems for a Cellular Approach to Continuous Process Chemistry from Discovery to Market |journal=Organic Process Research & Development |date=May 2004 |volume=8 |issue=3 |pages=440–454 |doi=10.1021/op049970n }}</ref>
* Pressurisation of materials within microreactors (and associated components) is generally easier than with traditional batch reactors.  This allows reactions to be increased in rate by raising the temperature beyond the boiling point of the solvent.  This, although typical Arrhenius behaviour, is more easily facilitated in microreactors and should be considered a key advantage.  Pressurisation may also allow dissolution of reactant gasses within the flow stream.