Guo Qingxiang, Zhao Yuqiong, Lei Yaning, Li Guoqiang, He Yajun, Zhang Guojie, Zhang Yongfa, Li Kunjie
State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China.
Key Laboratory of Coal Science and Technology, Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China.
ACS Omega. 2023 Jul 13;8(29):25938-25950. doi: 10.1021/acsomega.3c01736. eCollection 2023 Jul 25.
Although the preparation of coal-based carbon nanotubes (CNTs) has been realized in many studies, the relationship between carbon source structure of coal and CNT growth has not been studied in depth. In this study, we used lignite and KOH as raw material and catalyst and tuned lignite structure via hydrothermal modification to promote the formation of CNTs during catalytic pyrolysis. The main carbon source of CNTs was explored from the change of coal structure and pyrolysis characteristics. The results indicate that the CNT yield of lignite pyrolysis products is only 2.39%, but the CNT yield increases significantly after lignite was hydrothermally modified in a subcritical water-CO system. The graphitization degree, the order degree, and CNT content increase continuously with the increase in modification temperature, and C-M has the highest CNT content of 9.41%. Hydromodification promotes the rearrangement of aromatic carbon structures to generate more condensed aromatic rings linked by short aliphatic chains and aromatic ether bonds. The variation of these structures correlates well with the formation of CNTs and leads to the change in the carbon source components released during coal pyrolysis. Compared to lignite, modified coal releases more aromatic compounds, especially polycyclic aromatic hydrocarbons with ≥3 rings and phenols during catalytic pyrolysis, which is conducive to the transformation into carbon clusters and provides carbon sources for CNT growth. In addition, modified coal releases a slightly more carbon-containing gas (CH and CO) than lignite, which has a limited effect on the growth of CNTs. This study provides a novel and efficient method for enhancing the growth of CNTs by a molecular tailoring strategy of coal.
尽管在许多研究中已经实现了煤基碳纳米管（CNT）的制备，但煤的碳源结构与CNT生长之间的关系尚未得到深入研究。在本研究中，我们以褐煤和KOH作为原料和催化剂，并通过水热改性来调整褐煤结构，以促进催化热解过程中CNT的形成。从煤结构和热解特性的变化中探索了CNT的主要碳源。结果表明，褐煤热解产物的CNT产率仅为2.39%，但在亚临界水-CO体系中对褐煤进行水热改性后，CNT产率显著提高。随着改性温度的升高，石墨化程度、有序度和CNT含量不断增加，且C-M的CNT含量最高，为9.41%。水热改性促进了芳族碳结构的重排，生成了更多由短脂肪链和芳族醚键连接的稠合芳环。这些结构的变化与CNT的形成密切相关，并导致煤热解过程中释放的碳源成分发生变化。与褐煤相比，改性煤在催化热解过程中释放出更多的芳族化合物，尤其是≥3环的多环芳烃和酚类，这有利于转化为碳簇并为CNT生长提供碳源。此外，改性煤释放的含碳气体（CH和CO）比褐煤略多，这对CNT的生长影响有限。本研究提供了一种通过煤的分子剪裁策略来增强CNT生长的新颖而有效的方法。
