Phase transfer catalysis (PTC) is a chemical method employing catalysts with the ability to penetrate the interface between two immiscible phases and to transfer the immiscible reactants into the phase where the reaction takes place. PTC reactions are most commonly performed in stirred tanks where the inhomogeneous mixing often results in loss of selectivity and product quality.

Microreactors, with their narrow drop size distribution and interfacial surface-to-volume ratios above 10 000 m²m^–3, have been shown to be an efficient tool for the intensification of PTC reactions.

J. C. Schouten and colleagues, Eindhoven University of Technology, The Netherlands, present a novel interdigital mixer-redispersion capillary assembly aimed at preventing coalescence in the bubbly flow. The microreactor assembly was tested on the phase transfer-catalyzed esterification of sodium benzoate and benzyl bromide into benzyl benzoate.

Compared to the conventional phase transfer-catalyzed esterification, the continuous operation in the interdigital mixer-redispersion capillary assembly eliminated the use of solvents and bases, removed an energy-intensive step of distillation while increasing process safety.

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• Redispersion Microreactor System for Phase Transfer-Catalyzed Esterification,
  J. Jovanović; W. Hengeveld; E. V. Rebrov;  T. A. Nijhuis; V. Hessel; J. C. Schouten,
  Chem. Eng. Technol. 2011.
  DOI: 10.1002/ceat.201100118