Biogas upgrading: optimal activated carbon properties for siloxane removal

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Octamethylcyclotetrasiloxane (D4) is a volatile silicone compound requiring removal from industrial gas streams.
• Activated carbons (ACs) are widely explored for adsorptive removal of organic pollutants.

Purpose of the Study:

• To evaluate the performance of various commercial activated carbons for D4 removal.
• To investigate the influence of operational parameters on D4 adsorption capacity.
• To understand D4 polymerization on AC surfaces.

Main Methods:

• Dynamic adsorption experiments were conducted using 12 commercial activated carbons.
• ACs were characterized using physical and chemical techniques.
• D4 adsorption was tested under varying concentrations, carrier gases, and humidity levels.

Main Results:

• Adsorption capacity strongly correlated with the textural properties of the activated carbons.
• A wood-based chemically activated carbon exhibited the highest capacity (1732 ± 93 mg g⁻¹).
• D4 adsorption capacity was reduced by lower concentrations, biogas components (CH4, CO2), and humidity.
• D4 polymerization on AC surfaces was observed, linked to phenolic and carboxylic groups.

Conclusions:

• Optimized activated carbon selection and process conditions are crucial for efficient D4 removal.
• The presence of biogas matrix components and humidity significantly impacts D4 adsorption performance.
• D4 polymerization poses a challenge for AC regeneration, necessitating further investigation.