Reaction dynamics, ionic liquids diffusion

Another demonstration of a continuous flow operation is the psi-shaped microreactor that was used for lipase-catalyzed synthesis of isoamyl acetate in the 1-butyl-3-methylpyridinium dicyanamide/n-heptane two-phase system [144]. The chosen solvent system with dissolved Candida antarctica lipase B, which was attached to the ionic liquid/n-heptane interfacial area because of its amphiphilic properties, was shown to be highly efficient and enabled simultaneous esterification and product removal. The system allowed for simultaneous esterification and product recovery showed a threefold reaction rate increase when compared to the conventional batch. This was mainly a consequence of efficient reaction-diffusion dynamics in the microchannel system, where the developed flow pattern comprising intense emulsification provided a large interfacial area for the reaction and simultaneous product extraction. Another lipase-catalyzed isoamyl acetate synthesis in a continuously operated pressure-driven microreactor was reported by the same authors [145]. The esterification of isoamyl alcohol and acetic acid occurred at the interface between n-hexane and an aqueous phase with dissolved lipase B from Candida antarctica. Controlling flow rates of both phases reestablished a parallel laminar flow with liquid-liquid boundary in the middle of the microchannel and a separation of phases was achieved at the y-shaped exit of the microreactor (Figure 10.25). The microreactor approach demonstrated 35% conversion at residence time 36.5 s at 45 °C and at 0.5 M acetic acid and isoamyl alcohol inlet concentrations and has proven more effective and outperformed the batch operation, which could be attributed to the favorable mass and heat transfer characteristics. 

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