Experimental and theoretical investigation of the reaction between CO$_{2}$ and carbon dioxide binding organic liquids

Abstract

The reaction kinetics of CO$_{2}$ absorption into new carbon dioxide binding organic liquids (CO$_{2}$BOLs) was comprehensively studied to evaluate their potential for CO$_{2}$ removal. A stopped-flow apparatus with conductivity detection was used to determine the CO$_{2}$ absorption kinetics of novel CO$_{2}$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 CO$_{2}$ with CO$_{2}$BOLs was used to calculate the observed pseudo-first-order rate constant k$_{0}$ (s$^{-1})$ and second-order reaction rate constant k$_{2}$ (m$^{3}$/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 k$_{0}$ increased with increasing amine concentration and temperature. By comparing using two different CO$_{2}$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 CO$_{2}$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.