Analysis of Reaction Kinetics of CO₂ Absorption into a Novel 1-(2-Hydroxyethyl)-piperidine Solvent Using Stopped-Flow Technique

In this present work, the absorption kinetics of CO₂ into aqueous 1-(2-Hydroxyethyl) piperidine (1-(2-HE)PP) solutions with respect to observed pseudo-first-order rate constant (k₀) and second order reaction rate constant (k₂), were determined using the stopped-flow apparatus within the 1-(2-HE)PP concentration range of 0.20-1.00 kmol/m³ and a temperature range of 293-313 K. The values of k₀ were then represented using the correlation based on the base-catalyzed hydration mechanism. The results show that the correlated values of k₀ matched well with the experimental values with an acceptable AAD of 8.3%, which indicates that the base-catalyzed hydration mechanism can satisfactorily describe the experimental kinetics data of the1-(2-HE)PP reaction with CO₂. In order to comprehensively understand the kinetics, the ion speciation plots of 1-(2-HE)PP-H₂O-CO₂ system were developed using the pH method. In addition, the Brønsted plots between k₂ (obtained from stopped-flow apparatus) and pK_a (obtained from experimental measurement) for 1-(2-HE)PP were developed, and then used to predict k₂ using the values of pK_a.