Valorization Strategies in CO₂ Capture: A New Life for Exhausted Silica-Polyethylenimine

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Silica-polyethylenimine (Si-PEI) composites are utilized for CO2 adsorption in carbon capture and storage (CCS).
• Degradation of these materials after use necessitates sustainable end-of-life management strategies.
• Recovering valuable components or chemicals from spent adsorbents is crucial for circular economy principles.

Purpose of the Study:

• To investigate methods for the recovery and valorization of degraded Si-PEI materials after CO2 capture.
• To analyze the physico-chemical changes in polyethylenimine (PEI) after its use in CO2 adsorption.
• To explore the potential of pyrolysis for generating valuable chemicals from exhausted PEI.

Main Methods:

• Solvent extraction was employed to recover degraded PEIs and silica from Si-PEI composites.
• Pyrolysis was conducted to decompose the recovered PEI and analyze the resulting products.
• Thermal analysis (TGA), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), NMR spectroscopy, ATR-FTIR, and rheology were used to characterize the materials.

Main Results:

• Proxies for degradation, including urea/carbamate moieties, were identified in the extracted PEIs using Py-GC-MS, NMR, and ATR-FTIR.
• Pyrolysis of exhausted PEIs yielded alkylpyrazines, with yields estimated by Py-GC-MS.
• The study demonstrated the feasibility of recovering and transforming degraded Si-PEI materials.

Conclusions:

• Degraded Si-PEI materials from CO2 capture can be processed via solvent extraction and pyrolysis.
• The pyrolysis of exhausted PEIs offers a pathway to valuable chemical products, such as alkylpyrazines.
• This research highlights the potential for upcycling spent CO2 adsorbents, contributing to sustainable materials management.