FCC富芳烃油定向可控改性及中间相结构形成机制研究

Mesophase pitch is selected as an excellent precursor to prepare the carbon fiber material with distinct features of high modulus. However, the research and development of low-cost high-quality carbon fiber are severely restricted because of high softening point, poor thermal stability and easy-coking property of petroleum based mesophase pitch, which have negative influences on the spinning of mesophase pitch. In this study, the methods of vacuum distillation, solvent selective extraction and quantitative hydrogenation-alkylation would be employed to pretreat a feedstock of FCC aromatic-riched oil, respectively, achieving the adjustments of initial molecular weight distribution, structural composition and the content of alkyl structure of carbonation system. The action mechanism of initial molecular weight distribution, structural composition and alkyl groups on formation and development of mesophase pitch would be investigated, as well as the structure-function relationship between structural group compositions of feedstock and characteristics of mesophase pitch product, containing optical structure, rheological property, molecular structure and crystal structure. Further, a creative combined pretreatment would be put forward via integrating the above-mentioned three pretreatment methods of feedstock with each other. The technological route design and processing condition optimization of the combined pretreatment would be done, and meanwhile, the action mechanism of combined pretreatment on formation and development of mesophase pitch would be explored to provide theoretical and technical support for the preparation of mesophase pitch as an excellent carbon fiber precursor and the high value-added utilization of FCC aromatic-riched oil.

中间相沥青是制备高强高模碳纤维的优良前驱体，但目前成本较低的石油基中间相沥青在纺丝过程中存在软化点高、热稳定性差和易结焦的问题，严重阻碍了石油基碳纤维的研发。针对这一问题，本项目拟以FCC富芳烃油为原料，采用减压蒸馏、溶剂选择性萃取和氢化烷基化三种方法对原料进行改性处理，实现炭化体系初始分子量分布调控、分子结构组成调整和原料分子中烷基结构类型的定向调控，探讨体系初始分子量分布、分子结构组成和烷基结构种类及含量对中间相结构形成与发展的影响，揭示原料结构族组成与中间相沥青光学结构、流变性能和液晶结构性质之间的构效关系。在此基础上，将这三种改性处理方法复合，提出富芳烃油制备中间相沥青的复合改性处理工艺，完成复合改性处理方法路线设计及工艺条件优化，探究富芳烃油复合改性处理过程对中间相结构的调控机制，为高性能石油基碳纤维前驱体中间相沥青的制备和FCC富芳烃油的高值化利用提供理论依据和技术支持。

中间相沥青被公认是制备高性能沥青基碳纤维的优良前驱体，其合成原料和制备工艺是影响中间相品质的主要因素。本项目采用减压蒸馏、溶剂选择性萃取、氢化烷基化和复合改性四种方法对FCC富芳烃油进行改性处理，探究改姓原料分子量分布和分子结构组成对中间相结构形成与发展的作用机制。结果表明，在原料芳香度相似的情况下，随着原料分子量分布变窄、分子中环烷结构增加和烷基侧链变短，所制备的中间相沥青各向异性结构尺寸增大，可溶性中间相含量提高，软化点降低，残炭值提高，中间相沥青的中间组分（正庚烷不溶-甲苯可溶组分HI-TS和甲苯不溶-吡啶可溶组分TI-PS）在体系中的最大含量逐渐降低。同时，中间相晶格缺陷减少，微晶结构尺寸增大。此外，氢化烷基化改性原料中环烷结构对石油基中间相沥青品质的改善效果最优，其次为烷基短链，改善效果最弱的为烷基长链。具有较多环烷结构、适量甲基基团或少量乙基基团的富芳烃馏分经过热缩聚反应可以制得光学结构优异、分子结构有序和石墨化程度高的优质中间相沥青。与单纯的减压蒸馏、溶剂选择性萃取和氢化烷基化改性工艺相比，复合改性处理工艺所制备的中间相微晶结构缺陷更少、纺丝性能更好。