Estimation of Correlation between Electrical Conductivity and CO₂ Absorption in a Monoethanolamine Solvent System

Abstract

The present paper reports the ionic conductivities of carbamic acid (C2H5ONH3 +) and carbamate (C2H5ONHCOO–) by analyzing the measured electrical conductivity (EC) variation according to the amount of CO2 absorbed in an aqueous monoethanolamine (MEA) solvent system. On the basis of these conductivities, the study also investigates the correlation between EC variation and the amount of CO2 absorbed in five MEA solvents with a concentration range of 0.1 M to 0.5 M. The study is underpinned by several assumptions, and a CO2 absorption experiment is carried out with the five MEA solvents. The ionic conductivity of C2H5ONH3 + and C2H5ONHCOO– is calculated as 73.60 S·cm2·mol–1·z–1 and 16.40 S·cm2·mol–1·z–1, respectively. An average error between the estimated EC (ECc) variation calculated via the correlation equation and the measured EC (ECm) variation obtained from the experiments is 6.92 % in five MEA solvents. However, the ECc in the 0.5 M MEA system is 10.22 % lower than ECm. This difference may be ascribed to the substantial deviation from the assumptions of the 0.5 M solvent due to its relatively high concentration which decreases the ionic activity coefficient of existing ions in the solvent.

Estimation of CO2 Absorption Capacity via Correlating Measured Electrical Conductivity in a Diethanolamine Solvent System Compared to Monoethanolamine Solvent Systems

“…This methodology has been described in detail in our previous papers. 14,15 At 0.1, 0.2, 0.3, 0.4, and 0.5 M DEA solvent, CO 2 capacities obtained from the experiment were 6.43, 10.56, 14.54, 19.07, and 20.63 g CO 2 •kg −1 solvent, respectively. Although CO 2 capacities of 0.1−0.4 M DEA were slightly higher than the theoretical value of CO 2 capacities for the 1:1 reaction (indicated as the red solid line) but the CO 2 absorption capacity of 0.5 M DEA was smaller than the theoretical value by about 0.6%, overall experimental values of CO 2 capacities were very similar to the theoretical values.…”

“…The methodology used to estimate the concentrations of every ion based on the amount of absorbed CO 2 has been described in detail in our previous papers. 14,31 As a result, the ionic conductivity of R 2 NCOO − was calculated to be 20.01 S•cm 2 •mol −1 •z −1 with an average error of 12.2% in the calculation.…”

“…Although the mass composition is recommended to indicate the unit of all concentrations, with the values denoted in parentheses with superscripts a and b in this section, the molarity was also used as the unit of solvent concentration to clearly compare to the CO 2 absorption system using MEA solvent as reported in previous papers. 14,15 4.1. CO 2 Absorption Capacity of the DEA Solvent System.…”

Density, Viscosity, Refractive Index, and Electrical Conductivity of Degraded Monoethanolamine Solutions at Standard Temperatures

“…Unlike density, viscosity, and refractive index, there are very few publications about the electrical conductivity of MEA solutions. The electrical conductivity of MEA solutions with very low solvent concentration (lower than 0.5 mol·L –1 ) was reported. , Figure shows that the electrical conductivity increases slightly when the solvent is diluted from a very high concentration to a relatively low concentration. However, a huge increase can be witnessed when the MEA mass fraction is much lower, and a steep increase can be predicted when solvent reaches infinite dilution.…”

“…Good agreement was found as illustrated in reported. 28,29 Figure 4 shows that the electrical conductivity increases slightly when the solvent is diluted from a very high concentration to a relatively low concentration. However, a huge increase can be witnessed when the MEA mass fraction is much lower, and a steep increase can be predicted when solvent reaches infinite dilution.…”