Rapid Determination of the Reaction Kinetics of an n-Butylbenzaldimine Synthesis Using a Novel Mesoscale Oscillatory Baffled Reactor

Abstract

Abstract Two designs of “mesoscale” (∼4-5 mm diameter) oscillatory baffled reactor (OBR), namely integral (orifice plate-type) and central (axial disc) baffled OBRs were developed and characterised at low net flow rates of 0.4 – 1.0 ml/min (corresponding to 1.6 ≤ Re n ≤ 5.0) over a wide range of oscillation conditions of 80 ≤ Re o ≤ 200. For a reactor volume of approximately 30 ml and residence times from 25 to 90 min, high degrees of plug flow were achieved. For the integral design, the maximum number of tanks-in-series (N) achieved was 30 at Re o =130. Using the centrally baffled design, the maximum number of tanks-in-series achieved was 40, at Re o ≥180 for Re n ≥4. As plug flow can be easily achieved over a wide operating window at very low flow rates, these novel designs are ideal for rapid continuous process screening at laboratory scale. The reaction of benzaldehyde with n-butylamine to form the imine was chosen to demonstrate the ability of the mesoscale OBRs to rapidly screen process conditions and obtain kinetic data. In situ FTIR spectroscopy was used to determine concentrations in real time. The relative flows of the reagents were controlled to impose successions of aldehyde:amine molar ratios. A clear step-change between these molar ratios was observed and the kinetics of the reaction were modelled and determined. The results showed that the rate constants were 1.9 x 10 -2 s -1 and 2.0 x 10 -2 s -1 for the beaker and the meso-OBR, respectively.