Vapor–Liquid Equilibria Data for 2‑Piperidineethanol and 1‑(2-Hydroxyethyl)pyrrolidine in Aqueous Solutions and a UNIQUAC Model Representation

This work reports equilibrium data for two amines, 2-piperidineethanol (2-PPE) and 1-(2-hydroxyethyl)­pyrrolidine (1-(2HE)­PRLD), and their aqueous solutions. The pressure, temperature, and composition data are used to calculate experimental activities. Data cover temperatures from 363 to 426 K for the pure amines and from 323 to 373 K for the aqueous solutions. A UNIQUAC model was used to represent the binary vapor–liquid equilibria (VLE), whereas the Antoine equation was used for pure components. In an aqueous solution, the vapor pressure of 1-(2-hydroxyethyl)­pyrrolidine (1-(2HE)­PRLD) over the measured composition and temperature ranges is higher than that of 2-piperidineethanol (2-PPE). The developed UNIQUAC models represent the data well. For 2-piperidineethanol (2-PPE), the model gave 1.9% deviations for total pressure, 12.4% for vapor-phase composition, 12.7% for the calculated activity coefficients, and 16.2% for the excess heat capacity. In the case of 1-(2-hydroxyethyl)­pyrrolidine (1-(2HE)­PRLD), the model was slightly more accurate, representing the data with 1.7% deviation for total pressure, 5.9% for vapor-phase composition, and 5.2% for the calculated activity coefficient.