Characterizing Mixing Time Scales in an Exothermic Mixing-Limited Reaction

Exothermic mixing-limited reactions are commonly encountered in the pharmaceutical and fine chemicals industry, and are usually executed in semi-batch reactors. Their scale-up, however, requires a keen understanding of the heat and mass transfer aspects of the reaction and can be influenced by process parameters such as reagent dosing rate and agitation. In this contribution, we will present a case study where scale-up of a highly exothermic reaction resulted in variable yields in different reactor geometries due to heat and mass-transfer limitations. A systematic analysis of local meso-mixing rates with correlations by Bourne et al.^a and computational fluid dynamics in laboratory and pilot plant reactors revealed presence of local temperature hot-spots, which is attributed as the main cause of variable reaction yields. As a result, a scale-independent meso-mixing rate based parameter was applied to obtain a high reaction yield at different scales.

^aBourne, John R. "Mixing and the selectivity of chemical reactions." Organic Process Research & Development 7.4 (2003): 471-508.

The work presented here was sponsored by AbbVie. AbbVie contributed to the design, research, and interpretation of data, writing, reviewing, and approving the publication. All authors are employees of AbbVie.