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mass transfer) and heat exchange, each combined with a defined setting of residence times.
These speed-ups of transport are especially useful in challenging ultrafast metallorganic
reactions and highly exothermic reactions, respectively. Recently, chemists approached
this technology as a versatile tool in their quest for process automation and optimization
and coined such scientific endeavours 'flow chemistry'. It was the chemists, together with
the authors of this chapter, who - instead of 'only' releasing the intrinsic reaction potential
of a chemical reaction - aimed to use the microreactor as a tool by which to actively push
the chemistry to its limits.
In this way, the idea of novel process windows was developed. These represent a
gateway to entirely new operating conditions, intensifying the reaction kinetics at the
small scale and changing the overall process scheme at the large. A favourite tool with
whichtoaccomplishnovelprocesswindowsis microstructured equipment, with its
capabilities and modularity, which jointly lead to a higher selectivity, lower energy input
per product, lower amount of byproduct (and thus lower waste generation) and higher
yields. It is proposed that chemical intensification be explored via harsh conditions
attained by the application of high T, high p and high c (favourably under the use of
designer solvents). Successful examples promoting the concept are demonstrated in
this chapter.
Beyond making reactions much faster, microreactors also allow new transformations
such as direct or single-flow multistep syntheses. This, together with the reduction of
separation expenditure and the integration of processing functions, yields a completely
different process scheme for a flow process, called 'process design intensification'.
To conclude, three intensification fields - transport, chemical and process design - for
microreactors have been presented. The latter two constitute novel process windows and
enrich the role of micro process technology for future chemical manufacture. Via boosted
productivity and other measures, the cost structure of flow processes is affected, as is the
sustainability footprint. Novel process windows provide even greater degrees of freedom to
meet the demands which green chemistry and green engineering issues place on the
chemical industry.
Acknowledgement
Funding by the Advanced European Research Council Grant 'Novel Process Windows -
Boosted Micro Process Technology' under grant agreement number 267443 is gratefully
acknowledged.
References
(1) J.-C. Charpentier, Process intensification by miniaturization. Chem. Eng. Technol., 28, 255-
258 (2005).
(2) P. Gravesen, J. Branebjerg and O. Sondergard Jensen, Microfluidics - a review. J. Micromech.
Microeng., 3, 168-182 (1993).
(3) D. J. Laser and J. G. Santiago, A review of micropumps. J. Micromech. Microeng., 14, R35-
64 (2004).
(4) C. Wiles and P. Watts, Continuous flow reactors: a perspective. Green Chem., 14, 38-54 (2012).
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