| In recent decades,with the development of human society,the concentration of CO2 in the atmosphere is growing,so the greenhouse effect is exacerbated.And the Earth's climate and environment are damaged seriously.Energy-saving and emission reduction have become the world's problems.Although there are many ways to control the CO2 concentration of atmosphere,choosing an appropriate means to absorb CO2 is significant. The synthesis of the materials which can directly absorb the CO2 has become an important research topic.At present the separation and enrichment methods of CO2 are mainly divided into solvent absorption,adsorption,membrane separation and condensation.According to documents introduced,porous silica materials(PSM)has been extensively studied among many adsorbents.CO2 adsorption on PSM is mainly physical adsorption which is weak and the selective adsorption is relatively low.In order to improve CO2 adsorption behave,the PSM can be modified with organic amine or doped with alkaline oxides.In this paper,the study content is divided into the following three parts:Mesoporous SiO2 microspheres is synthesized by n-hexadecylamine and tetraethoxyorthosilicate(TEOS) in definite experimental conditions.Submarines, mesoporous SiO2 is modified withγ-aminopropyl-triethoxysilane by post-synthesis silylation methods.The structure and physicochemical properties of both mesoporous SiO2 and ATES-SiO2 are characterized with XRD,N2 adsorption-desorption and IR.The CO2 adsorption of SiO2 increases from 0.93 mmol·g-1 to 5.74 mmol·g-1 after amino-modified at room temperature and normal pressure.This shows that CO2 adsorption can be greatly enhanced by amino-modified material.In this part,the pore size of SiO2 spheres is enlarged by a low-cost and simple synthetic method.M esoporous SiO2 spheres is impregnated into three-ingredient salt solution,which is composed of H2O,NaCl,LiNO3 and KCl whose mass ratio is 70:20: 8:3.7,at 300℃for 2 h.The BET characterization results show that the average pore size of MS spheres is enlarged from 2.7 nm to 3.2 nm.The XRD pattern shows that the structure of SiO2 mesoporous after reamed is still amorphous.And the CO2 adsorption is greatly increased from 0.93 mmol·g-1 to 4.60 mmol·g-1.Then after amino-modified,the CO2 adsorption is increased to 5.85 mmol·g-1.In the preparation process of spherical mesoporous SiO2,the propriate amount of Ca(NO3)2·4H2O or Al(NO3)3·9H2O are doped respectively.Then hydroxide Ca(OH)2/Si and Al(OH)3/Si are obtained.Again these samples are calcined for 6 h at 600℃in the air atmosphere.The XRD characterization indicat that there are new samples obstained. According to CO2 absorption experiments,the CO2 adsorption of Ca(OH)2/Si sample is 5.46 mmol·g-1.The CO2 absorption capacity of mesoporous SiO2 materials doped by Ca(NO3)2·4H2O or Al(NO3)3·9H2O is increased.Compared with the amino-modifited method,this method has many advantages,such as low cost of raw materials,simple equipment requirements,easy operation and non-toxic harmless.
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