Design, characterisation and application of a miniaturised CSTR for reaction kinetic studies using in situ Raman spectroscopy

Abstract

Magnetically agitated miniaturised continuous stirred tank reactors (m-CSTRs) are an attractive tool for the investigation of reaction kinetics, as they combine active stirring with enhanced heat and mass transfer due to their small dimensions, while their compatibility with in situ spectroscopic techniques enables reaction monitoring and high-throughput data acquisition. This study presents the development of a 2.65 mL m-CSTR, integrated with in situ Raman spectroscopy for real-time kinetic data acquisition in continuous flow. The reactor, featuring a temperature-controlled stainless-steel chamber with a top quartz glass window and a PTFE slotted impeller, was assessed for its macro- and micromixing characteristics at flowrates between 0.5 and 4 mL/min. The slotted impeller led to near-ideal CSTR behaviour and improved micromixing quality in comparison to conventional cross stir bars of similar dimensions. Using the imine synthesis of n-benzylidenebenzylamine from benzaldehyde and benzylamine as a model reaction, kinetic parameters were determined with direct composition measurement inside the reactor and the most informative region of the design space, i.e., the experimental conditions that provide the most useful data for accurate kinetic parameter estimation and model validation, was identified to be in the region of high reactant concentrations and short residence times within the temperature range investigated (15-45 oC).