Model-based scale-up and reactor design for solvent-free synthesis of an ionic liquid in a millistructured flow reactor

We investigated solvent-free synthesis of the ionic liquid 1-butyl-3-methylimidazolium bromide in a microreactor setup. Time–conversion curves were used to derive a model for the liquid–liquid two-phase system taking both heat transfer and mass transfer into account. Simulations conducted with parameter variations were used to evaluate the general influence of mass and heat transfer coefficients on the conversion and temperature profiles in a flow reactor. A scale-up of the microreactor experiments to production in a millistructured plate reactor can be limited by insufficient heat removal, which results in parametric sensitivity. Thus, a general stability criterion was applied to the reactor model to derive stability diagrams from the calculated temperature profiles. These diagrams provide parameter ranges that ensure stable reactor operation, and can be used to predict the effectiveness of different scale-up concepts. Several concepts were combined in the design of a reaction-specific optimized multi-injection flow reactor with a channel geometry that could be adapted to the predicted local rate of heat generation.