A Combined Experimental and Computational Study on the Shuttle Mechanism of Piperazine for the Enhanced CO₂ Absorption in Aqueous Piperazine Blends

Abstract

Piperazine (PZ) blends containing PZ and monoethanolamine (MEA)/N-methyldiethanolamine (MDEA)/2-amino-2-methyl-propanol (AMP) were experimentally and computationally investigated to analyze their potential capabilities for CO2 capture, and the shuttle mechanism of PZ for enhanced CO2 absorption were verified. In experiments, the concentration of both PZ and MEA/MDEA/AMP were varied to show the effect of concentration ratio and the influence of amine components on the CO2 absorption rate and capacity. Experimental results showed that all the PZ blends possessed high absorption rates and large absorption capacities. To further understand the interaction behavior of amines/products and possible reaction pathways, both qualitative and quantitative 13C NMR analyses were conducted. The results indicated the conversion between absorption products, which can release free PZ to capture CO2 and consequently improve the absorption performance. Moreover, the static quantum mechanical calculations and ab initio molecular dynamics (AIMD) simulations combined with metadynamics sampling were conducted to evaluate the thermodynamic stability of absorption products and kinetically favorable key elementary reactions in PZ blends. This study highlights an accurate description of the shuttle effect of PZ for the enhanced CO2 capture by PZ blends.

Experimental Evaluation of Chemical Reactions Involved in Ultrasonic-Assisted Absorption of Bulk CO2

“…In each position, the O-H functional group is attached to a carbon atom, which is sterically hindered. Additionally, when atoms are close together, the energy of the covalent bonds that keep the atoms together in the molecule increases [40,41]. Due to the increased energy, breaking the chemical bond of the O-H functional groups of the MDEA molecule for generating OḢ radicals is more complex than in water, which is not considered a steric hindrance.…”

Comprehensive analysis of thermodynamic models for CO2 absorption into a blended N,N‐diethylethanolamine‐1,6‐hexamethyl diamine (DEEA‐HMDA) amine

“…MDEA, and AMP to study their CO 2 absorption capacity. 9 It was found that the addition of PZ could greatly improve the absorption rate and capacity of CO 2 . The absorption-desorption ability of CO 2 was studied by mixing MEA with tertiary amines.…”