The Effect of Chemical Structure of Newly Synthesized Tertiary Amines Used for the Post Combustion Capture Process on Carbon dioxide (CO2): Kinetics of CO2 Absorption Using the Stopped-Flow Apparatus and Regeneration, and Heat Input of CO2 Regeneration

Abstract

This work presents the effect of chemical structure of newly synthesized tertiary amines; 4-(dimethylamino)-2-butanol (DMAB), 4-((2-hydroxyethyl)(methyl)amino)-2-butanol (HEMAB) and 4-((2-hydroxyethyl)(ethyl)amino)-2-butanol (HEEAB) based on the kinetic of the reactions of CO2 absorption in aqueous amine solution in terms of the second-order reaction rate constant (k2) using the stopped-flow apparatus at 298-313K and 0.1-1.0M. The rates and heats of CO2 absorption and regeneration using actual concentrations of single amine and blended amine solvents were also measured respectively at 313K and 363K. The results showed that the k2 of CO2 in amine solutions (i.e. HEEAB and HEMAB) were the first and second highest (1096.9 and 1043.6 m3/kmol.s) comparing to DEAB, DMAB and MDEA (47.2, 19.9 and 11.1 m3/kmol.s), respectively. Three amines (i.e. HEEAB, HEMAB and DMAB) had fast CO2 absorption rate (0.142, 0.111 and 0.082mol CO2/min, respectively) and CO2 regeneration rate (0.295, 0.452 and 0.512mol CO2/min, respectively) while maintaining a low heat input of CO2 regeneration (72.44, 60.48 and 39.73kJ/mol CO2, respectively). The three blended amine solutions (MEA-HEEAB, MEA-HEMAB and MEA-DMAB) at ratio 5:1.25M all had fast CO2 absorption rates (0.129, 0.108 and 0.094mol CO2/min, respectively), CO2 regeneration rates (0.064, 0.072 and 0.070mol CO2/min, respectively) and low heat input of CO2 regeneration (188.78, 171.85 and 130.27kJ/mol CO2, respectively). Based on these results, it was proven that HEEAB, HEMAB and DMAB can be considered to be promising amine components for a post combustion CO2 capture process.