玉米淀粉掺杂沥青基活性炭的甲烷/氮气吸附分离性能

Adsorptive separation performance of CH_(4)/N_(2) on corn starch doped asphalt based activated carbon

选用沥青为碳源,掺杂玉米淀粉,采用物理活化法制备沥青基活性炭,采用SEM、元素分析仪、FT-IR、77 K-N_(2)吸附脱附等温线和273 K-CO_(2)吸附等温线对活性炭的表面性质和孔结构进行分析,从而研究玉米淀粉掺杂量对沥青活性炭的表面性质、孔结构及CH_(4)/N_(2)吸附分离性能的影响,并采用Toth模型对298 K和100 kPa下CH_(4)和N_(2)吸附等温线进行拟合。结果表明,随着玉米淀粉掺杂量的增加,沥青活性炭的微孔体积从0.142 cm^(3)/g提高到0.406 cm^(3)/g,微孔比表面积从352 cm^(2)/g提高到1015 cm^(2)/g,且0.4~0.6 nm的微孔含量增加,玉米淀粉的加入提高了沥青活性炭的孔隙率。活性炭在298 K,100 kPa下的CH_(4)吸附量与0.4~1.0 nm范围内的微孔体积有关;CH_(4)/N_(2)的分离比是与0.4~0.6 nm范围内的微孔含量及表面含氧和含硫总量有关。玉米淀粉掺杂沥青基活性炭不仅具备纯玉米淀粉活性炭较高的CH_(4)吸附量,而且具备纯沥青活性炭良好的CH_(4)/N_(2)分离比。沥青基活性炭Y1(m(沥青)∶m(玉米淀粉)=2∶1)的CH_(4)吸附量达到21.7 cm^(3)/g,CH_(4)/N_(2)的分离比达到3.8。

A series of activated carbons are prepared by physical activation method using asphalt as carbon source and corn starch as doping material.And the surface properties and pore structure of activated carbons are analyzed by SEM,EDS,FT-IR,77 K-N_(2) adsorption-desorption isotherms and 273 K-CO_(2) adsorption isotherms.The experiments are conducted to explain the influence of the corn starch content on surface properties,pore structure and CH_(4)/N_(2) adsorption and separation properties of asphalt based activated carbons.The adsorption isotherms of CH_(4) and N_(2) are measured at 298 K and 100 kPa,which are fitted by Toth model.The results show that with the increase of corn starch,the micropore volume of activated carbon increases from 0.142 cm^(3)/g to 0.406 cm^(3)/g,the specific surface area of the micropore increases from 352 cm^(2)/g to 1015 cm^(2)/g,and the micropore content of 0.4-0.6 nm increases,indicating that the addition of corn starch improves the porosity of asphalt activated carbon.By analyzing the relationship between micropore volume and surface functional groups and adsorption capacity and selectivity,the adsorption capacity of CH_(4) on activated carbon at 298 K and 100 kPa is mainly ascribed to the micropore volume in the range of 0.4-1.0 nm,and the selectivity of CH_(4)/N_(2) is mainly related to the micropore content of 0.4-0.6 nm and the total amount of oxygen and sulfur on the surface.Corn starch doped asphalt based activated carbon not only has a higher CH_(4) adsorption capacity of pure corn starch activated carbon,but also has a good separation ratio of CH_(4)/N_(2) on pure asphalt activated carbon.The adsorption capacity of CH_(4) on the Y1(pitch∶corn starch=2∶1)is to 21.7 cm^(3)/g and the segregation ratio of CH_(4)/N_(2) is to 3.8.