Enhancing Reactive Microemulsion Processes: Dynamic Optimization and Cyclic Semibatch Operation for the Reductive Amination of Undecanal in a Mini-Plant

Abstract

Achieving the maximum production rate of a chemical component in a process requires an optimal process design and operating strategy. One possible approach toward this goal is the elementary process function (EPF) optimization where the optimal temperature, pressure, and mass flow profiles for a Lagrangian fluid element are determined. In the current study, the EPF methodology is applied to the reductive amination of long-chain aldehydes in microemulsion systems (MES) to maximize the reaction performance. These solvent systems are a multiphase green chemistry approach to combine highly selective homogeneous catalysis with excellent catalyst retention using a water phase. For the reductive amination in MES, a cyclic semibatch operation is selected as the best approximation of the optimal EPF trajectories. This new process concept is implemented in a modular mini-plant, and successful validation of the optimization results is achieved for 19 consecutive semibatch reactions during a 125 h mini-plant campaign. The yield (43.8 ± 3.3) %, selectivity (64.3 ± 5.4) %, and conversion (68.0 ± 3.4) % are higher than those achieved in a previous mini-plant operation using a CSTR. Especially, the strong increase in selectivity, achieved through suppression of side product formation, proves that the EPF calculation can lead to a better process design and operating strategy. 99.1% of the catalyst entering the settler is recycled to the reactor, and the reaction performance remains constant for 125 h without requiring additional catalyst. This excellent catalyst retention and long-term stability support the results of previous studies, which outline the large potential of microemulsion systems as reaction media for homogeneous catalysis and their readiness for process implementations.