The influence of polyethyleneimine type and molecular weight on the CO2 capture performance of PEI-nano silica adsorbents

• Published in: Applied energy 2014-12, Vol.136, p.750-755
• Main Authors: Li, Kaimin, Jiang, Jianguo, Yan, Feng, Tian, Sicong, Chen, Xuejing
• Format: Article
• Language: English
• Subjects: Applied sciences; Carbon capture; CO2 adsorbent; Energy; Exact sciences and technology; Nano silica; Polyethyleneimine
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2014.09.057

•We tested the influence of PEI types and molecular weight on CO2 sorption capacity.•The preference of different PEIs to form urea with CO2 was investigated.•The volatilization and leaching behavior of different PEIs was estimated.•We measured the CO2 sorption and regeneration heat of different PEIs.•The influence of moisture on PEI-silica sorbents was preliminarily investigated. Amine–silica adsorbents are considered alternatives to aqueous solutions of amines, which have been traditionally used to capture carbon dioxide (CO2) from flue gas. Among amine–silica adsorbents, polyethyleneimine (PEI)-silica is particularly effective at capturing CO2 from flue gas due to its high thermal stability. In this study, we investigated the influence of PEI type (i.e. branched vs. linear) and molecular weight on the CO2 capture performance of PEI-silica adsorbents. PEI molecular weight influenced the thermal stability of PEI-silica adsorbents; however, when the molecular weight was ⩾1200Da the increase in stability was negligible in the temperature range of 25–160°C. Branched PEIs (BPEIs) achieved higher CO2 saturated sorption capacities compared to linear PEIs (LPEIs); however, LPEIs were more stable than BPEIs during CO2 sorption–desorption cycling. PEI molecular weight also influenced the CO2 saturated sorption capacity; CO2 saturated sorption capacity decreased as PEI molecular weight increased, and among the adsorbents tested in this study BPEI/800-silica had the highest CO2 saturated sorption capacity (202mg CO2/g adsorbent). Both PEI type and molecular weight exhibited influence on the sorption or desorption heat of PEI-silica adsorbents. The CO2 regeneration heat was much lower than that of MEA solution for all PEI-silica adsorbents tested in this study.