The Transition States for CO2 Capture by Substituted Ethanolamines

Area of Science:

• Computational chemistry
• Chemical kinetics
• Green chemistry

Background:

• Ethanolamines are widely used in CO2 capture.
• Understanding reaction mechanisms is crucial for solvent design.
• Electronic and steric factors influence reaction pathways.

Purpose of the Study:

• To investigate the electronic and steric effects on the reaction mechanisms of substituted ethanolamines with CO2.
• To determine the kinetic and thermodynamic favorability of carbamate and bicarbonate formation.
• To identify potential CO2 capturing solvents with enhanced reaction rates.

Main Methods:

• Utilizing SCS-MP2/6-311+G(2d,2p) quantum chemical calculations.
• Calculating activation energy barriers and reaction energies for carbamate and bicarbonate pathways.
• Incorporating implicit solvent effects using the universal solvation model SMD.

Main Results:

• Carbamate formation is kinetically and thermodynamically favored over bicarbonate for monoethanolamine (MEA).
• Increased steric hindrance around the nitrogen atom favors bicarbonate formation, leading to higher reaction rates.
• N-alkylation (N-methyl or N-ethyl) on MEA reduces activation barriers for both pathways, increasing reaction rates.

Conclusions:

• Steric and electronic effects significantly influence CO2 reaction mechanisms in ethanolamines.
• Substituted ethanolamines with optimized steric and electronic properties show promise as efficient CO2 capture solvents.
• N-alkylated ethanolamines exhibit higher reaction rates, making them attractive for industrial CO2 sequestration applications.