Experimental and theoretical investigation of the reaction between CO2 and carbon dioxide binding organic liquids

Abstract

The reaction kinetics of CO2 absorption into new carbon dioxide binding organic liquids (CO2 BOLs) was comprehensively studied to evaluate their potential for CO2 removal. A stopped-flow apparatus with conductivity detection was used to determine the CO2 absorption kinetics of novel CO2 BOLs composed of DBN (1,5-diazabicyclo[4.3.0]non-5-ene)/1-propanol and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene)/1-butanol. A modified termolecular reaction mechanism for the reaction of CO2 with CO2 BOLs was used to calculate the observed pseudo-first-order rate constant k0 (s-1) and second-order reaction rate constant k2 (m3/kmol.s). Experiments were performed by varying organic base (DBN or TBD) weight percentage in alcohol medium for a temperature range of 288-308 K. It was found that k0 increased with increasing amine concentration and temperature. By comparing using two different CO2 BOL systems, it was observed that the TBD/1-butanol system has faster reaction kinetics than the DBN/1-propanol system. Finally, experimental and theoretical activation energies of these CO2 BOL systems were obtained and compared. Quantum chemical calculations using spin restricted B3LYP and MP2 methods were utilized to reveal the structural and energetic details of the single-step termolecular reaction mechanism.