| The greenhouse effect and climate change caused by the substansive emission of CO2have aroused wide public concern. Compared to the other technologies, CO2adsorption could reduce its capture and seperation cost more significantly, showing favorable application prospect. Among the frequently reported adsorbents, the functional matetials composed of organic amines and porous supports has been a hot spot. On which, the CO2adsorption capacity has been prominently improved. However, several problems encountered were low amine efficiency and poor thermal stability. In this thesis, the nanotubes with large surface area and pore volume have been chosed as supporters in consideration of its accomodation and dispersion effect to the loaded amines. On this basis, several novel CO2adsorbents with superior adsorption capactiy and thermal stability have been developed. Furthermore, the mechanisms for the enhancement in adsorption performance on amine/supports composites through the modification of surface chemical properties of the supports have also been investigated.Firstly, polymeric amine functionalized protonated titanate nanotubes (PTNTs) have been prepared through a wet impregnation route. And then the effects of different amine loading amounts and adsorption temperature on CO2adsorption capacity have been studied. It was found that the CO2adsorption capacity of these composites could be maintained within the temperature range from75to100℃. And high thermal stability and well cyclic adsorption/desportion performance were also obtained for amine loaded PTNTs absorbents.After that, the influencing mechanism of surface chemical properties of PTNTs on CO2adsorption performances has been investigated. There are abundant Bronsted acid sites on the internal and external surface of PTNTs, which could anchor the loaded amines via acid-base interation, thereby enhancing the thermal stability of sorbents. Additionaly, the amine groups (NH2/NH) at the end-point of loaded amine could be protonated and formed NH3+/NH2+groups, whereas CO2could be weakly adsorbed on these NH3+/NH2+groups, which could be purged away easier than carbamate species formed through the zwitteration mechanism. Thus, the adsorption/desorption cyclic performance was greatly improved. Morever, the amine efficiency, CO2diffusion rate in the bulk network of amine ploymer were also improved.And then, SBA-15support was modified by mono-layered alkyl chain-(CH2)3-SO3H on the surface. Such modification could spatially disperse PEI into small particle size, which made it expose more active sites and decreased the CO2diffusion resistance. Hence the adsorpiotn amount of CO2could be greatly improved. The improvement of surface acid-base properties could prevent the loss of active sites caused by amine evoparation and guarantee the well adsorption/deportpion cyclic performances.Finally, the sulfnated mesoporous SBA-15with incorporated heteroatom Zr have been impregnated by PEI to capture CO2under7vol%CO2/N2mixture and75℃conditions. It was found that the adsorption capacity of PEI/NSZr3SBA was high as50mg/g, which was twice higher than that of un-modification one. And92%of the original amount could be retained after30cycles, while that was77%before modification.Several novel CO2adsorbents with high adsorption capacity and well cyclic stability have been developed to adress the problems encountered on the amine functionalized composites. We focused on modifying the surface acid/basic properties of nanotubes suppporters and investigating its effect onto the adsorption mechanism of loaded amines. Our results provided new insight into the design of high-efficiency adsorbent materials and laid the theoretical foundations for the application of amine functionalized composites. |
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