Kinetic modeling of the synthesis of N-aminopiperidine via the Raschig process: Reaction optimization and continuous process

• We studied the formation of N-aminopiperidine (NAPP) via the Raschig process.
• We established a kinetic model for its rate of formation and those of side-reactions.
• We verified the accuracy of the model in a diluted medium.
• This model allowed defining the optimal conditions for NAPP synthesis in batch.
• This model enabled scaling-up NAPP synthesis by its transfer to a continuous process.

N-aminopiperidine (NAPP) belongs to a large family of compounds, namely the cyclic alkylhydrazines, used as precursors for different targets in fine chemicals, such as pharmaceuticals and cosmetics. The formation of NAPP via the Raschig process by reacting piperidine (C5H10NH, PP) with monochloramine (NH2Cl) involves many side-reactions because of the reactivity of the latter. An exhaustive kinetic model, which reflects the rate of NAPP formation and that of side-reactions occurring during the synthesis of NAPP, was established. Additionally, a comparative study of theoretical and experimental concentration-time curves permitted to verify the accuracy of the model in a diluted medium. Moreover, the established kinetic model allowed to define the optimal conditions for NAPP synthesis in a concentrated medium, by varying the reactants concentrations, [PP]/[NH2Cl] ratio, pH and temperature. Hence, the application of the kinetic model enabled to optimize the reaction in view of its transfer to a continuous process.