Tuning the acidity and textural properties of polyethyleneimine-supported adsorbents for enhanced economical CO2 capture

Abstract

CO₂ capture using amine-based porous solids is a promising field that has received tremendous research interest. Owing to high CO₂ capture performance, fast uptake kinetics and easy regeneration, CO₂ capture using amine-based sorbents has extensively been studied. Herein, polyethyleneimine (PEI)-based sorbents were developed using pseudoboehmite (PSB) and gamma alumina (γ-Al₂O₃) as supports, represented as PEI@PSB and PEI@γ-Al₂O₃, respectively. The dispersion, morphology and dynamics of PEI on a porous support play key roles in the CO₂ capture performance of an adsorbent. The dispersion of PEI in an adsorbent is tuned by varying the nature of acidity of the supports. The acid–base interaction between PEI and a support enhances its dispersion in the adsorbent. It was observed that PEI@PSB with enhanced Brønsted acidic sites showed excellent PEI dispersion and consequently showed superior CO₂ uptake performance compared to PEI@γ-Al₂O₃. In situ IR analysis majorly shows the formation of ammonium carbamates and negligible carbamic acid, confirming well-dispersed PEI on the PSB support. Among the series of adsorbents, 25% PEI@PSB exhibited the highest CO₂ uptake performance of 4.9 mmol CO₂ per g of the sorbent. Nitrogen sorption analysis revealed that 25 wt% of PEI is the loading optimum to retain the porosity of the material, facilitating better CO₂ uptake. The long-term stability and regeneration studies confirmed that the PEI@PSB adsorbent was robust and could retain a similar adsorbent capacity of up to 100 recycles. Finally, life-cycle assessment (LCA) depicted a decrease of 19–21-fold in all the environmental impact categories per ton of carbon capture with renewable energy input, indicating the potential for decarbonizing hard-to-abate industrial emissions and achieving net-zero climate targets.