高温氨气炭化制备氮掺杂炭干凝胶及其CO2吸附性能

摘要

以间苯二酚(R)和糠醛(F)为原料,通过溶胶-凝胶法、常压干燥法合成RF有机干凝胶,并在高温氨气氛下炭化制备氮掺杂炭干凝胶(ACXs).采用热重分析仪、比表面积及孔径分析仪、扫描电镜、傅里叶红外光谱与 X线光电子能谱对ACXs的表面物化性质进行表征;应用固定床等温吸附实验探讨ACXs对CO2的吸附性能.研究结果表明:高温氨气炭化后,ACXs 比表面积和总孔容随着炭化温度升高而增大,温度越高,增加幅度越大;高温氨气炭化使材料表面形成氨基、吡咯氮、吡啶氮等含氮官能团,从而显著提高表面含氮量,有利于提高 ACXs的CO2吸附性能;随着炭化温度升高,ACXs微球收缩变小,孔隙裂解、气化刻蚀效果增强,含氮量减少;氮的存在形态由氨基基团向吡啶基团转化,碱性含氮官能团减少,从而降低ACXs的CO2吸附能力;控制合理的氨气炭化温度,可以提高ACXs对CO2的吸附性能.%Organic xerogels were prepared by the sol-gel method and ambient drying method from polymerization ofresorcinol with furfural, these xerogels were carbonized in ammonia atmosphere to obtain nitrogen-doped carbonxerogels (ACXs). The surface physical and chemical properties of the ACXs were characterized by thermogravimetry(TG), specific surface area and pore distribution analyzer (BET), Fourier transform infrared spectroscopy (FTIR),scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The isothermal adsorptionperformance of the ACXs for carbon dioxide was investigated with fixed-bed apparatus. The results show that aftercarbonization at high temperature in ammonia atmosphere, the BET specific surface area and total pore volume of ACXsincrease with the increase of the carbonization temperature. The higher carbonization temperature is, the more theamplitude increases. Mainly nitrogen functional groups which are formed on the ACXs surfaces because ofhigh-temperature carbonization in ammonia atmosphere are amino groups, pyrroles and pyridines. Nitrogen content ofACXs improves significantly, and the adsorption performance of ACXs for carbon dioxide also improves. With theincrease of carbonization temperature, ACXs microspheres become smaller as a result of shrinkage, the pyrolysis and gasification process enhance remarkably, both leading the nitrogen content to decrease. Additionally, the presence ofnitrogen forms is converted from amino groups to pyridine ones. The reduction of carbon dioxide adsorption capacity ofACXs is attributed to the decrease of alkaline nitrogen functional groups. The carbon dioxide adsorption capacity ofACXs can be advanced by controlling carbonization temperature in ammonia atmosphere.