Mass transfer intensification of 2-methyl-5-nitrotetrazole synthesis in two-phase liquid–liquid Taylor flow in microreactor

Abstract Alkylation of 5-nitrotetrazole sodium salt with dimethyl sulfate was carried out under two-phase Taylor flow conditions in a system “dichloromethane-water” in a microreactor of 1.22 mm diameter. A comparative analysis was performed of the specific interfacial area, the surface and volume mass transfer coefficients with respect to results obtained in the presence of phase transfer catalysis in a batch reactor with a magnetic stirrer (MM) or a high speed rotor disperser (HSD). It was shown that regardless of the larger drops formed in the microreactor (and an essentially less value of the specific interfacial area a) as compared to the HSD reactor the surface mass-transfer coefficient ( k L ) attained in the microreactor is 15 and 208 times higher (in MM and HSD reactors correspondingly) in the absence of the phase transfer catalyst and 3.17 (MM) and 36.2 (HSD) times higher at the application of the latter. Without phase transfer catalyst the volume mass transfer coefficient ( k L a ) in the microreactor is 15.2 (MM) and 6.8 (HSD) times larger than in batch reactors. At the use of the phase transfer catalyst the volume mass transfer coefficient ( k L a ) in the microreactor is 3.24 (MM) and 1.2 (HSD) times larger than in batch reactors, even though interfacial area in HSD 30 times higher than that in the microreactor. The application of microreactors in future may provide a possibility to eliminate the use of phase transfer catalysts and high speed mixing devices and would lower the hazard level of the corresponding processes.