Carbon dioxide solubility in the aqueous mixtures of diisopropanolamine + l-arginine and diethanolamine +l-arginine at high pressures

Abstract

In recent years, emission of greenhouse gases especially carbon dioxide has been increased so that CO2is accounted for as a gas pollutant and leads to global warming. Thus, the removal of carbon dioxide is an important step in a gas capturing process. The absorption of CO2 in a mixture of alkanolamine + amino acid is a promising technique since this mixture reduces disposable contaminated solvents. In this work, CO2 solubility is measured in the aqueous solution of diisopropanolamine (DIPA) + l-arginine (ARG) and diethanolamine (DEA) + l-arginine (ARG) systems using a static high-pressure cell. We carried out the measurements at total pressure range of 1–38 bars and under isothermal conditions of 328.15, 348.15 and 363.15 K. We kept the total amine (amine + amino acid) concentration in the solution at 40 wt%, since this concentration has been shown that to be more effective in capturing of CO2 in a gas treatment industry. The compositions of the different systems were used as DIPA (40 wt%), DIPA + ARG (35 + 5 wt%), DIPA + ARG (30 + 10 wt%), DIPA + ARG (25 + 15 wt%), DEA (40 wt%), DEA + ARG (35 + 5 wt%), and DEA + ARG (30 + 10 wt%).We measured and correlated the densities of all mixtures versus temperature and mass fractions of the alkanolamine +amino acid. We presented the results as the partial pressure of CO2against its gas loading. It was found that loading of CO2enhanced with increasing pressure or decreasing temperature. Moreover, ARG (10 wt%) can mostly affect the CO2 solubility in DIPA + ARG and DEA + ARG systems at high temperature. Furthermore, a quadratic equation was used for correlation of the partial pressure of CO2against the gas loading so that the calculated results showed a good agreement with the experiment. Finally, the Clausius-Clapeyron equation was used for computation of the enthalpy of CO2 absorption for the present systems. As a result, it was shown that the DIPA + ARG (35 + 5 wt%) and DEA + ARG (35 + 5 wt%) systems have the lowest enthalpy of CO2 absorption (−∆Habs) values, respectively, so that these systems require less energy in a regeneration unit.