Ambient-Temperature Adsorption Of Low-Concentration Carbon Dioxide On Resin Based Solid Amine Sorbents

Solid amine sorbents are the-state-the-art CO2chemical sorbents with high capacity and good selectivity, which have been studied widely for low concentration CO2removal in the closed space. In the present work, a cost-effective solid amine sorbents have been developed by using macroporous adsorption resin as the supports and organic amine such as polyethylenimine (PEI) as the active ingredients. The low concentration CO2adsorption behavior over these solid amine sorbents were systematically studied. The major conclusions are summarized as follows:(1) Macroporous adsorption resins have large surface area, high pore volume and developed3D interconnected network, making them good candicates as the supports for organic amines. Herein, the macroporous polymethyl methacrylate resin HP2MGL was screened to be an ideal support and the polyethylenimine (PEI) with molecular weight of600was screened as the best organic amine with high adsorption capacity and good thermal stability. The CO2adsorption capacity generally increased with the increase of PEI loading, but the utilization of amine decreased gradually. The optimal PEI loading was found to be50wt.%and the highest CO2adsorption capacity at25℃was175.1mg/g.(2) The5000ppmCO2adsorption behavior over the resin based solid amine was studied. In the case of the dry gas (only N2as the carrier gas), the HP2MGL-PEI-50had a high equilibrium CO2adsorption capacity of93.5mg/g at room temperature. While the moisture present, the adsorption capacity increased remarkabley, indicating the moisture played a promoting effect on the sorption of CO2. The largest improvement was achieved at40%RH, while the adsorption capacity was increased to164.9mg/g. The sorbents had only limit adsorption ability towards O2. However, the present of O2in the mixture gas had a negative effect on the CO2adsorption capacity which was slightly decreased to81mg/g. The present of O2didn’t affect the cycling performance of the sorbents. The addition of CO2-neutral surfactant into the HP2MGL-PEI system could create extra CO2transfer pathways, facilitating CO2diffusion into the deeper PEI films. Consequently, the sorbents offered increased amount of reactive sites and higher utilization efficiency of amine groups, leading to a dramatically enhanced CO2dynamic capacity and regenerablity. While5%CTAB added, the sorbents showed a very high adsorption capacity of124mg/g for dry mixture gas and CO2adsorption capacity of165.5mg/g for a mixture gas with21%O2and40%RH moisture. The temperature swing adsorption (TSA) showed a good regeneration ability towards the sorbents at100℃.(3) The direct CO2capture from the ambient air was studied using resin based soild amines. At room temperature of25℃, the HP2MGL-PEI-50had a very high CO2adsorption capacity of86mg/g for400ppmCO2, which is among the highest values for the reported direct CO2capture results of the solid sorbents. Similar to the5000ppm adsorption behavior, the O2had a disadvantageous effect while the moisture had a promoted role on the direct CO2capture from the ambient air. The highest adsorption capacity of CO2was reached as high as139mg/g while the moisture was10%RH.