Post-combustion capture of CO2 using novel aqueous Triethylenetetramine and 2-Dimethylaminoethanol amine blend: Equilibrium CO2 loading-empirical model and optimization, CO2 desorption, absorption heat, and 13C NMR analysis

Abstract

The equilibrium CO2 loading was estimated by absorption of CO2 gas in the bubble column reactor for novel aqueous amine blend of triethylenetetramine (TETA) and 2-dimethylaminoethanol (DMAE). The absorption study was performed at a temperature of 298.15 to 333.15 K, mole fraction of TETA from 0.05 to 0.2, solution concentration varied from 1 to 3 mol/L, and CO2 partial pressure ranging from 10.13 to 25.33 kPa. The maximum experimental equilibrium CO2 loading was 0.92 mol CO2/mol amine at 315.65 K temperature, 17.73 kPa CO2 partial pressure, 0.13 mol fraction of TETA, and 1 mol/L solution concentration. The absorption results were validated by an empirical model with an average absolute relative deviation of 5.631 %. The desorption study was performed at a constant temperature and pressure of 393.15 K and 17.73 kPa, respectively. The cyclic loading capacity of this blend at 3 mol/L concentration showed 55.03 % higher results than that of 30 wt% (5 mol/L) monoethanolamine (MEA). The Gibbs-Helmholtz equation calculated the heat of CO2 absorption, and for this amine blend, it was found to be −67.135 KJ/mol. 13C nuclear magnetic resonance (NMR) spectroscopy was adopted to identify the chemical species in CO2-loaded and unloaded amine blends. Response surface methodology software optimized the final response. It predicted optimal equilibrium CO2 loading of 0.926207 mol CO2/mol amine at 304.36 K temperature, 0.14 mol fraction of TETA, 17.24 kPa partial pressure of CO2, and 1 mol/L solution concentration.