萘低温催化热缩聚机理研究

Mechanism for the catalytic thermal polycondensation of naphthalene at low temperature

萘在高温煤焦油中的含量可达10%以上,以萘为原料进行催化缩聚是制备中间相沥青和功能炭材料的有效途径。本研究以无水AlCl_(3)为催化剂,系统研究了萘在不同温度(90-170℃)及AlCl_(3)与萘物质的量比(1∶100-30∶100)条件下的常压聚合过程。结果表明,当温度低于110℃时,缩聚产物主要由多联三环化合物构成,重质产物仅占29.5%;温度为150℃时,缩聚产物以四至五环迫位芳香缩合物为主,中质组分含量保持在50%;温度为170℃时,缩聚产物中存在大量六环芳香核,原料转化率高达90.7%,而且产物具有良好的流动性及在THF中的溶解性,有利于高温热缩聚及后续石墨化工艺。本研究在提出“齐聚-热解-稠环化”反应机理基础上,考察了催化萘聚合产物的结构与组成:当AlCl_(3)与萘物质的量比为1∶100时,对萘短链齐聚进行模拟,可得二至七级萘齐聚物,而将AlCl_(3)与萘物质的量比提升至10∶100时,萘受AlCl_(3)催化热解可产生乙炔和甲基萘。该研究阐明了萘沥青前驱体的形成机理,为进一步萘催化缩聚制备中间相沥青的产物控制和沥青缩聚轻组分的循环再利用提供理论依据。

Naphthalene is an important component of high temperature coal tar and its content can reach more than 10%.Catalytic polycondensation of naphthalene is an effective way to prepare mesophase pitch and functional carbon materials.In this work,anhydrous AlCl_(3) was used as a catalyst for the polymerization of naphthalene under atmospheric pressure below 170 ℃ and the reaction mechanism was then systematically investigated.The results indicate that at 110 ℃,the polymer product is mainly composed of tricyclic compounds and the content of heavy products is only 29.5%.At 150 ℃,four to five peri-condensed aromatic compounds turn to be the main components and the content of medium components remains about 50%.At 170 ℃,there appear a large number of six-ring aromatic cores and the conversion of naphthalene reaches 90.7%.The polymer products exhibit good fluidity and solubility in THF,which can facilitate the high-temperature thermal polycondensation and subsequent graphitization process.With an AlCl_(3)/naphthalene molar ratio of 1/100,the second to seventh order naphthalene oligomers are obtained by the simulation of the short chain oligomerization of naphthalene.In contrast,when the AlCl_(3)/naphthalene molar ratio exceeds 10/100,acetylene and methylnaphthalene are produced by the catalytic pyrolysis of naphthalene.The mechanism of “Oligomerization-Pyrolysis-Aromatization ” was then proposed to explain the molecular transformation from naphthalene to pitch,which should be useful for the production of mesophase pitch precursor.