喹啉沥青的合成及其富氮衍生炭的微观结构研究

Synthesis of Quinoline Pitch and Microstructures of Its Nitrogen-rich Derived Carbons

富氮炭材料作为一种性能优异的功能材料,在化学催化、吸附分离、电极材料、储氢、染料废水处理等领域拥有广阔的应用前景。而富氮沥青由于原料丰富、制备方法相对简单且易大规模生产,作为一种优秀的富氮前驱体近年来受到人们的青睐。本工作以含氮单体喹啉为原料,5%(质量分数)的AlCl_(3)为催化剂,采用自升压法合成了四种喹啉沥青(QLP),利用傅立叶变换红外光谱、凝胶渗透色谱、热重分析仪对四种QLP的理化性质进行表征。通过元素分析、PLM、Raman和XRD研究了喹啉沥青衍生炭(CQLP)的氮含量及微观结构随炭化温度的变化情况。结果表明,四种QLP的收率都在90%左右,软化点在120℃左右,灰分小于2.5%,质均分子量为360~390,数均分子量为250~260。四种QLP的芳香指数(I_(ar))为0.55~0.69,邻位取代指数(I_(os))为0.52~0.72,支链化指数(CH_(3)/CH_(2))为0.11~0.23,750℃下的残炭率在29.0%~50.7%,其大小取决于合成条件。QLP的氮含量为8.22%,其氮含量随炭化温度升高呈先增加后略有下降的变化趋势,750℃下获得的CQLP具有最高的氮含量,为9.70%。三种CQLP的显微结构都以片状、纤维状组织为主,其含量分别占50%~60%和10%~30%,表现出良好的石墨化性。随炭化温度升高,CQLP的炭微晶尺寸增大,层间距减小,但规整性下降。

Nitrogen-rich carbon materialas a functional material with excellent performance has broad application prospects in chemical catalysis,adsorption and separation,electrode materials,hydrogen storage,dye wastewater treatment and other fields.Recently,nitrogen-rich pitch as an excellent nitrogen-rich precursor has been favored by many researchers because of its rich raw materials,relatively simple preparation method and easy mass production.In this work,four quinoline pitches were synthesized by self-rising pressure method using the nitrogen-containing mo-nomer quinoline as raw material and 5%(mass fraction)AlCl_(3) as catalyst.The physicochemical properties of four QLPs were characterized by Fourier transform infrared spectroscopy,gel permeation chromatography and thermogravimetric analyzer.The change of nitrogen content and microstructure of quinoline pitch-derived carbon(CQLP)with carbonization temperature was studied by elemental analysis,polarized light microscopy(PLM),Raman spectroscopy and X-ray diffraction(XRD)technique.The results showed that the yield of the four QLPs was all about 90%,the softening point was around 120℃,the ash content was less than 2.5%,the mass average molecular weight was 360—390,and the number average molecular weight was 250—260.The aromatic index(I_(ar))of the four QLPs was 0.55—0.69,the ortho-substitution index(I_(os))was 0.52—0.72,the branched chain index(CH_(3)/CH_(2))was 0.11—0.23,and the residual carbon yields at 750℃were in the range of 29.0%—50.7%,depending on the synthesis conditions.The nitrogen content of QLP was 8.22%,and its nitrogen content increased first and then decreased slightly with the increase of carbonization temperature.The CQLP obtained at 750℃had the highest nitrogen content of 9.70%.The microstructure of the three CQLPs carbon was mainly lamellar and fibrous textures,which account for about 50%—60%and 10%—30%respectively,showing good graphitization.With the increase of carbonization temperature,the carbon microcrystal size of CQLP increased,while the layer spacing decreased,but the regularity decreased.