Study On CO₂ Adsorption Properties Of Porous Materials Modified By Hyperbranched Polymer

Global cooling will occur in the upper atmosphere in conjunction with global warming in the troposphere due to long-term increase of greenhouse gas concentrations, particularly carbon dioxide. Carbon dioxide capture and storage（CCS） has commonly been seemed as a major option for reducing emission of CO₂. In this paper, with a larger pore diameter（4.75 nm） of disordered mesoporous silica（DMS）, more amines could be loaded on and CO₂ mass-transfer would be easier with lower diffusion resistance. Polyamidoamine（PAMAM）, tri（3-aminopropyl） amine（TRPN） dendrimers, TEPA-AN（TN） were synthesized, and impregnated on DMS to generate CO₂ adsorbents. Besides, the CO₂ adsorption capacity was dramatically enhanced by aggrandizing the acid site via introduction of Ti atom into the silica matrix. Detailed contents were as following:A novel series of polyamidoamine（PAMAM） dendrimers（generation 1.0 and 2.0） were synthesized and impregnated on DMS to generate CO₂ adsorbents. The CO₂ uptake of DMS-P1-50 and DMS-P2-50 was 126.5 and 119.8 mg×g-1 in pure CO₂ at 25 °C, respectively. After consecutive 8 adsorption-desorption runs, DMS-P1-50 showed an adsorption capacity of 124.8 mg·g-1, remaining 98.7% of its original value. The developed materials exhibited excellent cycling stability.Original series of tri（3-aminopropyl） amine（TRPN） dendrimers were synthesized and impregnated on DMS to generate CO₂ adsorbents. CO₂ adsorption/desorption tests indicated that the adsorption capacity of TS-G1-3CN-50（138.2 mg·g-1） was a bit lower than that of TS-TRPN-50（163.7 mg·g-1）. However, the later was difficult to desorb CO₂ completely, but TS-G1-3CN-50 could easily desorbed CO₂ completely at 100 oC at N2 atmosphere. After consecutive 12 adsorption-desorption runs, TS-G1-3CN-50 showed an adsorption capacity of 136.8 mg·g-1, remaining 99% of its original value. The developed materials exhibited excellent adsorption capacity and cycling stability.The organic-inorganic hybrid adsorbent was synthesized by introducting of Ti atom into the silica matrix before the impregnation of TN. With the incorporation of Ti, the series of Ti-DMS-TN composite adsorbents shows significantly enhanced CO₂ adsorption capacity and high amine efficiency. The highest CO₂ uptake（204.6 mg·g-1） was obtained for Ti（0.1）-DMS-TN in the flow of 90% CO₂. It shows the amine efficiencies of 1.4 and 2.0 times higher than the conventional DMS-TN in the flow of 90% and 1% CO₂, respectively. Consecutive 15 adsorption-desorption runs revealed that the Ti（0.1）-DMS-TN showed only a tiny decrease in adsorption capacity（from 78.98 to 78.23 mg·g-1, decreased by 0.01%）, providing thermal durability and adsorbent longevity.In conclusion, compared with organic amine of small molecule, polymer and modified organic amine possessed excellence consistency and unique modification. The synthesized functional adsorbents had excellent regenerability and stability with consecutive adsorption-desorption runs. Besides, the adsorbent prepared by DMS with the introduction of heteroatoms remained to be explored.