For the routine application of ionic liquids in organic synthesis and catalysis, high purity is a key issue. Prerequisite for this is a reproducible synthesis procedure, so a detailed knowledge of kinetics and thermodynamics is required. We combined reaction calorimetry with ATR-IR spectroscopy based on fibre optics for the operando monitoring in order to achieve an appropriate characterisation of the established batch processes. Based on this a continuous process utilising micro-structured equipment was realised that avoids end-of-pipe workup. (c) 2007 Elsevier B.V. All rights reserved.