Reaction Kinetics of CO₂ in Aqueous Ethylenediamine, Ethyl Ethanolamine, and Diethyl Monoethanolamine Solutions in the Temperature Range of 298−313 K, Using the Stopped-Flow Technique

Abstract

The observed pseudo-first-order rate constants (k 0) for the reactions between CO2 and ethylenediamine (EDA), ethyl ethanolamine (EEA), and diethyl monoethanolamine (DEMEA) have been studied using the stopped-flow technique in an aqueous solution at 298, 303, 308, and 313 K. The amine concentrations ranged from 26.2 mol/m3 to 67.6 mol/m3 for EDA, 28.2 mol/m3 to 81.9 mol/m3 for EEA, and 196.5 mol/m3 to 997.4 mol/m3 for DEMEA. The zwitterion mechanism was used to correlate the experimentally obtained rate constants. Both the zwitterion formation step and the proton removal step had a significant role for the primary and secondary amines (EDA and EEA). The reaction rate of CO2 in an aqueous EDA solution was observed to be much faster than that in aqueous MEA solution. The rate in aqueous EEA was much faster than in aqueous DEA, under the conditions studied. Finally, the reaction rate constant of CO2 in an aqueous tertiary amine (DEMEA) solution was observed to be much faster than that in methyl diethanolamine (MDEA). Only the zwitterion formation step had a significant role in the overall reaction. The base catalysis of the CO2 hydration mechanism could explain the reaction between CO2 and the tertiary amine. Therefore, the three selected amines are considered to be of interest to the gas sweetening industry.

Determination of Kinetics in Gas-Liquid Reaction Systems. An Overview

“…During a batchwise mode and the occurrence of a fast reaction, this would directly imply a relatively high pressure decrease (from an already low initial pressure) over a short period. A semi-batchwise operation takes a longer experimental time in the desired pseudo first order regime, thereby improving the experimental accuracy [17]. A typical experimental set-up with stirred cell apparatus and both methods of conducting experiments with respect to the gas phase are illustrated in Figures 4 and 5.…”

Reaction kinetics of CO2 in aqueous methyldiethanolamine solutions using the stopped-flow technique

“…The Bio-Kine software that controls stopped-flow experiments provided such a fitting option to extract rate constants directly from the measured data. The kinetic equation (11) expressed in terms of conductance that is proportional to the concentration is commonly used in analysing the first-order kinetic traces in a stopped-flow apparatus with a conductivity detection (Li et al 2007, Khorassani et al 2011). …”

Amine based solvent for CO2 absorption : from molecular structure to process

“…(Li, 2007) and MEA , 2.5 mole/L. Figure 7, shows that 1,6 Hexamethylenediamine shows an almost 10 times higher intrinsic kinetic rate constant than for MEA.…”

“…When assuming that the reaction rate for 1,6 Hexamethylenediamine is first order in the amine concentration and first order in CO 2, Figure 7, shows the comparative data for the second order rate constant of 2.5 mole/L 1,6 Hexamethylenediamine (HMDA) with the literature value of 2.5 mole/L MEA from and 2.5 mole/L Ethylenediamine (EDA) from Li et al 2007. (Li, 2007) and MEA , 2.5 mole/L.…”

“…Therefore in Table 5, the rate constant (DeCoursey approximation) for 1,6 Hexamethylenediamine (HMDA) and 1,6 Hexamethylenediamine, N,N' di-methyl (HMDA, N,N') is shown together with results for Diethylenetriamine, DETA (Hartono et al, 2009), Ethylenediamine, EDA (Li et al, 2007), Piperazine, Pz (Derks, 2006) and Monoethanolamine, MEA . The results suggested that 1,6 Hexamethylenediamine (HMDA) and 1,6 Hexamethylenediamine,N,N,N') show significantly faster kinetics than MEA, DEA and DETA, but lower than Piperazine, which has a cyclic structure.…”