Measurement of CO₂ absorption enthalpy and heat capacity of aqueous hexamethylenediamine and its aqueous mixture with N-methyldiethanolamine

Highlights: • Measurement of CO₂ absorption enthalpy in aqueous HMDA and (HMDA + MDEA) solvents. • Measurement of heat capacity of aqueous HMDA and (HMDA + MDEA) solvents. • ANN model to predict CO₂ absorption enthalpy in aqueous HMDA and (HMDA + MDEA) solvents. - Abstract: In this work, enthalpy of carbon dioxide (CO₂) absorption in aqueous hexamethylenediamine (HMDA) and its blend with N-methyldiethanolamine (MDEA) is measured using an automated reaction calorimeter in the temperature range of (30–60) °C. Concentrations of aqueous HMDA solution studied are (10, 20, 30) mass% and that for mixed amine system are (5% HMDA + 25% MDEA), (10% HMDA + 20% MDEA) and (15% HMDA + 15% MDEA). The heat capacity of the unloaded aqueous amine solvents is also measured in the same range of temperature and concentration. The experimental enthalpy of absorption data is presented as a function of CO₂ loading (mol CO₂ per mol total amine) and temperature. A combined model for the prediction of CO₂ absorption enthalpy in aqueous HMDA and (HMDA + MDEA) solvent systems is presented using artificial neural network (ANN) tool. A multi-layer feed-forward network is developed using Levenberg-Marquardt back propagation algorithm. Average absolute deviation between experimental and ANN model predicted data is found to be 0.38%.