Continuous membrane microreactors

Interesting KRs of ibuprofen were performed in single chaimel three-phase continuous-flow microreactors [108, 109]. Laminar streams of two phases were separated by an interposed third stream of an IL. Selective esterification of (S)-ibuprofen by CrL in the ethanoUc stream was followed by transportation of the (S)-ester through the IL serving as a pseudo-membrane and finally the (S)-acid was recovered by hydrolysis catalyzed by porcine pancreas lipase (PPL) in the aqueous stream. 

Two classes of gas-liquid microchannel reactors were developed in the past years -continuous-phase contacting falling film, overlapping charmel, mesh, and annular flow approaches, and dispersed-phase contacting by Taylor flow reactors, micromixers for bubble and foam formation, and miniaturized packed bed microreactors, which follow classical trickle-bed operation at smaller scale. Recently integration of operations inside a microdevice has been studied and led to the development of membrane microreactors. 

The optimal contact between two immiscible solvents (MTBE/H2O) in the microreactor set-up resulted in a high initial reaction rate and enantio-selectivity, comparable to the batch process in which optimized conditions were only obtained under vigorous stirring (2008CEJS89). In-line work-up of the cyanohydrin 6 was achieved via a membrane-based phase separation, allowing the continuation of the two-step reaction approach toward the protected mandelonitrile 7, while both steps have incompatible reaction conditions (2015OBC1634). 

Continuous production of a diazo compound in microreactors separated by a hydrophobic membrane was also patented by DSM IP Assets, The Netherlands, and... 

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