介孔材料氨基表面修饰及其对CO_2的吸附性能

CO_2 Capture by the Amine-modified Mesoporous Materials

采用接枝方法在介孔材料MCM-41和SBA-15的孔道内表面进行氨基化修饰,XRD、29Si-NMR、FT-IR、TGA、BET等测试结果表明,氨丙基三乙氧基硅烷(APTS)和氨乙基氨丙基甲基二甲氧基硅烷(AEAPMDS)都分别接枝在介孔材料的孔道内,表面氨基修饰量约为1.5-2.9mmol·g-1.表面修饰后介孔材料的孔道仍高度有序,但比表面积减小.表面修饰前后介孔材料对CO2的吸附性能发生显著变化,由于物理吸附转化为以氨基为活性中心的化学吸附,吸附量从修饰前的0.67mmol·g-1提高到2.20mmol·g-1.

Novel CO2 adsorbents were prepared by gaffing of two different aminosilanes on mesoporous silica MCM-41 and SBA-15. The properties of the mesoporous materials before and after surface modification were investigated by powder X-ray diffraction （XRD） pattern, solid-state ^29Si nuclear magnetic resonance （NMR）, Fourier transform infrared （FT-IR） spectra, and measurements of N2 adsorption and desorption isothermal, which confirmed that aminosilanes were grafted on the surface of the channels in the mesoporous materials. Thermogravimetry analysis （TGA） evaluated the amounts of grafted amine to be about 1.5-2.9 mmol·g^-1. The CO2 adsorption capacities of MCM-41 increased from 0.67 mmol·g^-1 to 2.20 mmol·g^-1 after AEAPMDS （N-β-（aminoethyl）-γ-aminopropyl dimethoxy methylsilane） modification （p =101 kPa） at room temperature. The studies of the mechanism of CO2 adsorption suggested that there were two main contributions for the increase： the chemical adsorption based on the active sites of amine groups and the capillary condensation caused by the nano-scale channels of the mesoporous materials.