Synergetic effect and mechanism between propylene carbonate and polymer rich in ester and ether groups for CO2 physical absorption

Abstract

Polymers rich in ester and ether groups may have excellent behavior for CO2 absorption. However, these polymers are not widely used in industry due to their high kinematic viscosities. The introduction of a small-molecule solvent is supposed to reduce kinematic viscosity of the polymer and help the polymer to be the excellent CO2 absorbent, but the effect and related mechanism remain unknown. This work proposed propylene carbonate (PC) + poly(ethylene glycol) bis(2-ethylhexanoate) (PEGB) as potential CO2 capture absorbent and carried out a theoretically and experimentally integrated study for CO2 capture using high-molecule polymer. Firstly, quantum chemistry calculation based on the density functional theory (DFT) attributes the strong PEGB-CO2 interaction to the large amount of effective binding sites including ester and ether groups. Secondly, the DFT simulation shows the synergetic effect of PC and PEGB: CO2 absorption of PC+PEGB is obviously easier than that of pure PC or PEGB. The synergetic effect is verified by thermodynamic experiment, the relatively high and positive value of excess CO2 absorption capacity of the PC+PEGB mixture is obtained. Thirdly, the synergetic mechanism is assessed to be the stronger Lewis acid-base and hydrogen-bond interaction offered by the mixed absorbent based on charge transfer behavior analysis. Finally, 0.2513 PC+0.7487 PEGB may be the optimum mass ratio for promising CO2 capture because of its high CO2 absorption capacity (0.3276 mol-CO2/mol-solution) and appropriate kinematic viscosity (2.5721 × 10−5 m2 s−1, about 60% decrease compared with PEGB).