CO₂-Induced Gate-Opening Adsorption on a Chabazite/Phillipsite Composite Zeolite Transformed from a Faujasite Zeolite...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Zeolites are widely used as adsorbents for gas separation.
• Developing selective adsorbents for CO2 capture is critical for mitigating climate change.
• Existing zeolites often require structure-directing agents or exhibit limited CO2 selectivity.

Purpose of the Study:

• To synthesize a novel Cs+-type chabazite/phillipsite (CHA/PHI) composite zeolite.
• To investigate the CO2 adsorption behavior and mechanism of the Cs+-type CHA/PHI zeolite.
• To evaluate the CO2/N2 separation performance for post-combustion carbon capture applications.

Main Methods:

• Organic structure-directing agent-free synthesis via steam-assisted conversion of FAU-type zeolite.
• Cs+ ion exchange to create the Cs+-type CHA/PHI composite.
• In situ powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FTIR) for mechanism elucidation.
• CO2 breakthrough measurements and Ideal Adsorbed Solution Theory (IAST) calculations for separation performance.

Main Results:

• The Cs+-type CHA/PHI zeolite exhibited unique gate-opening CO2 adsorption behavior and good thermal stability.
• Na+-type CHA/PHI zeolite did not show this behavior, indicating Cs+ ion or framework mobility is key.
• High CO2/N2 separation coefficients (>10,000) were achieved at 298 K and 318 K.
• Excellent CO2 working capacity was demonstrated for both pressure- and temperature-swing processes.

Conclusions:

• The Cs+-type CHA/PHI composite zeolite is a promising material for selective CO2 separation.
• The observed gate-opening adsorption is attributed to Cs+ ion or framework dynamics within the composite structure.
• This material offers a viable solution for CO2 capture from flue gas in power plants.