Study On Synthesis And CO₂Adsorption Properties Of Amine Modified Materials

Since the time of the industrial revolution, the atmospheric CO2concentration has risenby nearly40%to its current level of390.9ppm. The increased carbon dioxide concentrationin the atmosphere has been suggested to be a leading contributor to global climate change. Toslow the increase, reductions of CO2emissions are necessary. In this paper, five molecularsieves M1, M2, M3, M4and SBA-15were prepared by hydrothermal synthesis. With thesematerials, several different solid amine adsorbents were synthesized by impregnation method.Dynamic adsorption test of these adsorbents confirmed good adsorptive properties of M4andSBA-15materials. Zwitterion mechanism was confirmed by the adsorption test of S-MEA-50,S-DEA-50and S-TEA-50adsorbents. Langmuir adsorption model was used to study thekinetics and thermodynamics of M4-MEA-50, M4-MN-50, S-TEPA-50and S-TN-50solidamine adsorbents. Conclusions were drawn as follows:(1) Compared with M1, M2and M3materials, TM modified M4adsorbent showed thebest CO2adsorption capacity. The highest CO2adsorption capacity (up to159.1mg/g) wasgot by the M4-TM-60(60%amine loading) when using pure CO2at the temperature of25oC.Satisfactory adsorption stability (less than1%of initial capacity loss) during12adsorptiondesorption turnovers was achieved. Compared with the material of TEPA modified adsorbent,M4-TM adsorbent showed good CO2adsorption and desorption properties and was found tobe promising solid amine adsorbent for CO2capture.(2) TN modified SBA-15solid amine adsorbent exhibited good CO2adsorptive anddesorptive performance. A good adsorption capacity153.0mg/g was gained by the S-TN-50material at the temperature of25oC. Compared with S-TEPA-50, S-TN-50could desorbcompletely under the temperature of100oC in70min, while S-TEPA-50needed180min.The12adsorption-desorption cycle experiments revealed that the S-TN material exhibitedgood regenerability and stability. Thereby, compared with S-TEPA material, S-TN adsorbentwas one of the promising candidates for CO2capture.(3) Zwitterion mechanism was confirmed by the adsorption test of S-MEA-50,S-DEA-50and S-TEA-50adsorbents. When using pure CO2, the CO2adsorption capacities ofthese there adsorbents were169.6mg/g,85.3mg/g and27.5mg/g at the temperature of25oC. The kinetics and thermodynamics study of M4-MEA-50, M4-MN-50, S-TEPA-50andS-TN-50adsorbents confirmed the exothermic reaction and decreased randomness of CO2onto adsorbents. The negative values of Gibbs free energy changes approved a spontaneous innature of adsorption and confirmed affinity of adsorbents for CO2.In summary, compared with primary solid amine adsorbent, modified secondaryadsorbent exhibited good adsorption and desorption capacity and was approved as one of thepromising adsorbents for CO2capture.