Coiled flow inverter as a novel alternative for the intensification of a liquid-liquid reaction

This paper explores a novel alternative to conventional biodiesel production by taking advantage of the mixing, mass and heat transfer enhancement inherent in coiled flow inverters (CFIs) using the transesterification of fatty acids as a model reaction. The results show that the reaction can be carried out twelve times faster in a CFI than in a batch reactor, with a conventional oil to methanol molar ratio of 1:6 (100% excess methanol). The mixing enhancement in CFIs increases the mass transfer between the reacting phases, achieving conversions of up to 93% for 2 min residence time at 10 ml/min with seven 90 bends. The performance of CFIs was compared to that of simple helical and straight tube reactors under the same operational conditions. The conversion observed in the CFIs was up to 18% higher than the conversion obtained in the helical and straight tube reactors. However, all the reactors achieved similar oil conversions when a longer residence time (4 min) was allowed under the same flow rate conditions. Additional experiments with CFIs were carried out in order to explore lower oil:methanol molar ratios. The experimental results suggest that CFIs are capable of achieving conversions of up to 90% at 50% methanol molar excess (1:4.5 oil:methanol ratio) with a 4 min residence time, which contrasts with the 60 min required in batch reactors to achieve the same conversion. The results confirm that CFIs successfully intensify liquid-liquid reactions such as the transesterification of fatty acids when compared to a batch reactor. (C) 2017 Elsevier Ltd. All rights reserved.