Synthesis Of Modified PEI Functionalized Silica-based CO₂ Adsorbents And Their Performances

The global climate change caused by greenhouse effect has motivated extensive public concern in the world. Much research attention has been paid to the capture of emitted CO2, the main green house gas (GHG). Due to some unsolvable problems of commercial absorption technology involved with MEA solution, such as corrosion of installment and disadvantages on regeneration, the solid adsorption technology has been considered as a prospective alternate. Recently, mesoporous silica-amine hybrid materials are popular in the development of CO2 adsorptive material. However, their adsorption capacity was generally inhibited by loaded amine dispersion, which should be further improved for real application. In this dissertation, different modifications of supported-amine materials have been made to enhance the organic amine dispersion for improving CO2 adsorptive performances based on PEI-SBA-15 adsorbents.Firstly, a series of phosphoric ester based surfactants have been added to PEI/SBA-15 adsorbents during the process of impregnation for CO2 adsorption. Experimental results indicated that the addition of both BEP and TEP had positive effects on the improvement of CO2 adsorption capacity. In particular, over TEP modified sample, the dispersion of PEI was efficiently enhanced, thereby benefitting the diffusion of CO2 in the bulk of PEI. In addition, the adsorption/desorption cyclic performance was also enhanced after the TEP addition, which might be attributed to the enhancement of the CO2 diffusion and the thermal stability of the adsorbents.Secondly, SBA-15 grafted by amine alkyl chain (AαSBA-15) was prepared by the one-pot method and was used to support PEI for CO2 adsorption. AaSBA-15 could maintain the ordered and periodic pore structure as APTS content used was less than 15%. After that, the deformation of the tunnel in the resulted sample would occur. CO2 adsorption capacity of P35AaSBA-15 increased at a higher APTS content. Among which, P35A15SBA-15 showed an improvement of about 70% in adsorption capacity as compared with the base sample at 75℃. Especially, its CO2 adsorption capacity in pure CO2 at 35℃ was over 1.5 times higher than P35SBA-15. This finding indicated that the dispersion of PEI was greatly improved after amine alkyl chain grafting. Another reason of the highly increased adsorption performance might be attributed to the synergistic function between amino group of aminopropyl and PEI.Finally, the effects of NH4HSO4 concentration during the sulfation of Zr5SBA-15 process on the CO2 adsorption performance after loading PEI were investigated. It was found that acidity of the samples especially the Br(?)nsted acidity was strengthened with the increase of sulfation degree. And the CO2 adsorption capacity also increased with the rising of sulfation degree. The optimal adsorbent (P35NS1.0Zr5SBA-15) showed a 50% increase in CO2 adsorption capacity compared to the un-sulfation sample. Furthermore, an improved cyclic performance was also observed over sulfation sample. This could be attributed to the fact that the sulfation of Zr5SBA-15 would enhance the strength and amount of the acid sites on the surface of the supports, which could disperse and fix the amine supported on them.