煤焦油沥青基碳气凝胶微球的制备及分析

Preparation and analysis of carbon aerogel microspheres based on coal tar pitch

煤沥青是由多环芳烃组成的复杂混合物,其具有含碳量高的特点,是合成各种功能性碳材料的优质前体之一。以煤焦油沥青为原料、糠醛为交联剂,在硫酸催化作用下反应形成沥青-糠醛凝胶,进而经过常压干燥和碳化处理得到碳气凝胶,探讨了煤焦油沥青与溶剂、交联剂和催化剂的比例对沥青-糠醛凝胶的凝胶化程度以及碳气凝胶微球密度的影响。扫描电镜(SEM)结果显示,碳气凝胶微球的微观结构是由球状颗粒堆积而成;傅里叶红外光谱仪(FTIR)和同步热分析仪(TG)解析了沥青-糠醛凝胶在凝胶过程中的结构演变,及形成机理;CO_(2)活化后,碳气凝胶微球的孔隙结构得到明显改善,并保留了球状颗粒的微观形貌,且颗粒形状规整、表面光滑。

Coal tar pitch is a complex mixture composed of highly condensed aromatic compounds,which has the advantages of high carbon content,widely availability,and low price.It is regarded as one of the promising precursors in the synthesis of various functional carbon materials.Using coal tar pitch as raw material and furfural as a cross-linking agent,pitch-furfural gel is formed by the cross-linking reaction under the catalysis of sulfuric acid,then,the carbon aerogel microspheres were obtained after ambient-pressure drying and carbonization.The effects of the coal tar pitch to solvent,crosslinking agent,and catalyst ratios on the gel degree of carbon gel and carbon aerogel microspheres density were discussed.It was found that the optimal ratio of pitch to solvent was 0.5 g/ml,pitch to crosslinking agent was 0.10 g/ml,and pitch to catalyst was 5 g/ml.The density of carbon aerogel spheres was 0.24 g/cm3 after carbonization.The microstructure of carbon aerogel microspheres is generated by the accumulation of spherical particles,according scanning electron microscopy(SEM).Fourier transform infrared spectroscopy(FTIR)and thermogravimetric analyzer(TG)were used to examine the structure evolution of pitch furfural gel during the gelation process,as well as the production mechanism of pitch-furfural aerogel.The pore structure of the carbon aerogel spheres was dramatically improved after CO_(2)activation.With the increase of activation temperature and activation time,the specific surface area and pore diameter of the obtained samples were continuously increased,and mesopores with pore diameter of 2-3 nm were gradually formed.The samples activated in a CO_(2)atmosphere at 900℃for 4 h and 950℃for 2 h has specific surface areas of 2540 and 2852 m2/g,respectively.The microstructure of the carbon aerogel microspheres was unaffected,and the micromorphology of spherical particles was preserved,the particle shape was regular and the surface was smooth.