Kinetics Study and Modeling of CO₂ Capture in New Class Dual-Functionalized Ionic Liquid Blend Methyl Diethanolamine Absorbents

Abstract

In the capture of CO2 through the absorption process, selecting the absorbent blend system based on the absorption kinetics is crucial. This study focuses on the kinetic investigation of two new lab-synthesized dual-functionalized ionic liquids (DFILs), namely, T-Im and D-Im, which were employed as promoters in low-reactive aqueous methyldiethanolamine (MDEA) solvent for making a highly CO2 absorbing blend system. Then, CO2 absorption kinetic performance of these blends was assessed across a temperature range of 303–328 K. The results indicated a significant enhancement in the initial absorption rate with an increase in the DFIL concentration (2.5–10 wt %). The overall rate constant (k ov) values were higher in the capture using these DFILs compared to those with the reported promoters such as monoethanolamine (MEA), diethanolamine (DEA), and piperazine (PZ). The absorption rate followed the Arrhenius law with an activation energy of 25.61 kJ/mol for T-Im/MDEA and 24.87 kJ/mol for D-Im/MDEA, respectively. 13C NMR characterization confirmed that carbamate formation increased with an increasing T-Im concentration in the blend. The rate kinetic was modeled using the termolecular, zwitterion, and base-catalyzed hydration mechanisms. The rate equations based on the zwitterion mechanism for the T-Im and D-Im blended absorbents were k 2 , normalT − I m = 2.242 × 10 9 exp ( − 3531.09 T ) and k 2 , normalD − I m = 1.11 × 10 9 exp ( − 3504.22 T ) , respectively. The accuracy of the rate kinetic models expressed in terms of average absolute deviation (AAD) was found to be in the range of 4 to 8%.