Structure Design of Low-Temperature Regenerative Hyperbranched Polyamine Adsorbent for CO₂ Capture

A novel low-temperature regenerative hydroxy-functionalized hyperbranched polyamine adsorbent (0.16OH-HBPA) for CO₂ capture was readily prepared using glutaraldehyde to cross-link amino-terminated hyperbranched polymers (HBP) and functionalized with glycidol, followed by the reduction of the imino groups of 0.16OH-HBPA to alkyl aminos using NaBH₄. Here, the HBP has been prepared through the one-pot reaction between pentaethylenehexamine and methyl acrylate. The as-prepared 0.16OH-HBPA adsorbent showed a high adsorption capacity (4.05 mmol/g) for CO₂ (concentration, 10%) in the presence of water at 25 °C, and the alkyl amino utilization efficiency reached 73%. More importantly, the CO₂-adsorbed 0.16OH-HBPA showed excellent regenerative performance at low temperatures (85 °C, under pure CO₂ gas) due to the introduced hydroxyl that can cooperatively adsorb CO₂ via the amino groups to form stable carbamic acid. This process suppressed the formation of open-chain urea and cyclic urea and could overcome the disadvantages of high regeneration temperatures (≥90 °C, under pure inert gas) of CO₂-adsorbed traditional solid amine adsorbents.