Tuning the Acidity and Textural Properties for Enhanced Economical CO2 Capture in Polyethyleneimine (PEI) Supported Adsorbents

Abstract

CO2 capture using amine based porous solids is one of the promising fields that has received tremendous research interest. Owing to high CO2 capture performance, fast uptake kinetics and easy regeneration, CO2 capture using amine-based sorbents is extensively 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 porous support play key roles in the CO2 capture performance of the adsorbent. Here, the dispersion of PEI in the adsorbent is tuned by varying the nature of acidity in the support. The acid-base interaction between the PEI and the support enhances the 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. The in-situ IR analysis majorly shows the formation of ammonium carbamates and negligible carbamic acid confirming well dispersed PEI on PSB support. Among the series of adsorbents, 25% PEI@PSB exhibited the highest CO2 uptake performance of 4.9 mmol CO2/g of the sorbent. The nitrogen sorption analysis revealed that 25 wt% of PEI is the loading optimum to retain porosity in the material facilitating better CO2 uptake. The long-term stability and regeneration studies confirmed PEI@PSB adsorbent was robust and could retain the similar adsorbent capacity up to 100 recycles.