Preparation Of Amine-Functionalized Mesocellular Silica Foam （Mcf） And Their Application For CO₂Adsorption

Carbon dioxide is the main greenhouse gas causing global climate change, for the purpose of reducing carbon dioxide concentrations in the atmosphere, and effective research and development of carbon capture technology is particularly important. Research and development of effective carbon capture technology is particularly importantIn this thesis, mesocellular silica foam (MCF) was prepared using P123(EO20-PO70-E20) as templat, and adsorbents obtained through amino-functionalized. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2adsorption, fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) on MCF carriers and adsorbents were characterized. An on line mass spectrometer (MS) was connected to a fixed bed reaction apparatus to evaluate CO2adsorption capacity of adsorbents.The results are as follows:1. Mesocellular silica foam (MCF) materials having different pore sizes were prepared by adjusting the ratio of reactants, and seledted tetraethylenepentamine (TEPA) as functional reagents. CO2capture performances of the adsorbents were tested. The results indicated that the pore volume of supports has great effect on the CO2capture performance. MCF with different pore volumes impregnated same quality percentage TEPA, a larger pore volume with higher CO2adsorption performance. For MCF with larger pore volume, more unoccupied space is left after the same amount of TEPA was loaded into the pores. The unoccupied space is beneficial for higher CO2uptake because the mass transfer limitation can be reduced to some extent and the interaction between CO2and TEPA may be easier. MCF material with largest pore volume exhibited the largest CO2uptake of4.34mmol/g of adsorbent with a70wt%TEPA loading tested by the fixed-bed reactor and at least4.57mmol/g tested by thermogravimetric analysis (TGA) under the conditions of10.0%(v/v) CO2in N2at75℃. It was found that the adsorbents with good repeatability through adsorption-desorption cycles.2. MCF materials were functionalized with pentaethylenehexamine (PEHA) for CO2adsorption. It is shown that after modification with PEHA the structure of the support itself was undamaged as evidenced by N2adsorption. The highest CO2adsorption capacity of MCF-PEHA was obtained at75℃; With increasing PEHA loading, the CO2adsorption capacity increases and approached the highest adsorption capacity(3.55mmol/g) with a70%(w) PEHA loading, moisture improved the CO2adsorption performance of the adsorbents; research results show that, CO2adsorption capacity of MCF-70maintained stable after four adsorption-desorption cycles.3. The template of the as-synthesized MCFs was removed by high temperature calcination or low temperature ethanol extraction method, CO2adsorbent prepared by further grafting organic amine. The infrared results indicate that more silanol groups were preserved on solvent-extracted MCF than that on calcined MCF. The obtained template-free MCFs were grafted with3-aminopropyltriethoxysilane (APS) or3-(2-aminoethylamino)-propyl-dimethoxymethylsilane (APMS). Experimental results show that the solvent-extracted MCF grafted with APMS exhibited a higher CO2adsorption capacity (1.54mmol/g) under the condition of10.0%(v/v) CO2in N2at60℃. It was also found that the APMS-grafted sorbents are more capable in CO2sorption than APS-grafted, which is due to the higher amine content of the formers; and the CO2uptake can be further enhanced to2.02mmol/g with the presence of moisture. Although adsorbents adsorption capacities prepared by grafting below the impregnation method, but stability is higher than the latter, can exist stability under200℃. Cyclic CO2adsorption-desorption experiments results demonstrate that the composite sorbents are stable and regenerable.