Phase Change Study of a New Two-Phase Absorbent Based on DAP.

Area of Science:

• Chemical Engineering
• Environmental Science
• Materials Science

Background:

• Conventional CO2 absorbents suffer from slow absorption rates and low absorption capacities.
• There is a need for advanced absorbent systems to improve CO2 capture efficiency.

Purpose of the Study:

• To develop and investigate a novel two-phase absorbent system for enhanced CO2 absorption.
• To explore the use of nonaqueous solvents in combination with 1,3-propanediamine (DAP) and tetramethylethylenediamine (TMEDA) for CO2 capture.

Main Methods:

• Investigated CO2 absorption mechanisms using nuclear magnetic resonance (NMR) carbon spectroscopy.
• Compared absorption load, fraction ratio, and viscosity of different two-phase absorbents.
• Screened phase separation systems after CO2 absorption with various nonaqueous solvents.

Main Results:

• The DAP/TMEDA system showed an absorption load of 3.8 mol/kg, exceeding conventional ethanolamine solutions.
• The DAP/TMEDA/diglyme system achieved a 3.2 mol/kg absorption load with a reduced fraction of 38%.
• NMR and quantum chemical calculations confirmed carbamate formation, with DAP as the primary absorbent.

Conclusions:

• The developed two-phase absorbent system offers improved CO2 absorption performance.
• The addition of nonaqueous solvents enhances phase separation, reducing regeneration tower size and cost.
• Nonaqueous solvents accelerate phase separation via salt precipitation, without directly participating in CO2 absorption.