New solubility and heat of absorption data for CO2 in blends of 2-amino-2-methyl-1-propanol (AMP) and Piperazine (PZ) and a new eNRTL model representation

Abstract

New data comprising CO2 partial pressure, total pressure, and the heat of absorption of CO2 for over aqueous solution of 3 mol/dm3 AMP and 1.5 mol/dm3 PZ and total pressure and heat of absorption for different mol ratios of AMP/PZ (3.0/0.0, 0.0/1.5, 0.5/4.0, 1.5/3.0, 2.25/2.25, 3.0/1.5, 4.0/0.5) are presented as functions of CO2 loading and temperature.Measured solubility data and selected data reported in the literature were used in the regression of binary interaction energy parameters in the quaternary system (AMP/PZ/H2O/CO2) using the eNRTL model. The equilibrium constants and binary interaction energy parameters from our previous work on the ternary systems of AMP/H2O/CO2 and PZ/H2O/CO2 were used without refitting.Good agreement with the literature was observed for the total pressure data over aqueous solutions of 3.0 mol/dm3 AMP and 1.5 mol/dm3 PZ, and the CO2 partial pressure and heat of reaction data over aqueous solutions of 3.0 mol/dm3 AMP+1.5 mol/dm3 PZ at different loadings and temperatures. The results reflect that the new data are consistent with reported data from the literature.The modeling results show that the eNRTL model represents the data well with AARD values of 13.1% for total pressure and 20.9% for CO2 partial pressure. The volatility of AMP and PZ as function of loading and temperature and published speciation data for AMP/AMPH+, PZ/PZH+/PZH22+, PZCO2−/PZH+CO2−, PZ(CO2−)2 and HCO3−/CO32− were also well predicted.Only the heat of absorption data over an aqueous solution of 3.0M AMP+1.5M PZ from this work can be compared with literature data, and good agreement is observed. The eNRTL model also predicts satisfactorily the experimentally obtained heat of absorption data for all different ratios of AMP/PZ. Individual reaction contributions show that when the AMP/PZ ratio increases, the predicted total heat of absorption goes toward the single solvent AMP system where only protonated AMP is the main contributor. When the AMP/PZ ratio decreases, the predicted total heat of absorption also approaches the single solvent PZ system where the protonated PZ, PZ-monocarbamate and zwitterion reactions play important roles. In systems with high PZ-concentration, the contribution of the zwitterion, protonated PZ and PZ-carbamate cancel each other at high loadings.