State Key Laboratory of Solidification Processing, Carbon/Carbon Composites Research Center, Northwestern Polytechnical University, Xi'an, 710072, China.
Sci Rep. 2019 Dec 20;9(1):19496. doi: 10.1038/s41598-019-56136-0.
A density functional theory (DFT) study was employed to explore the mechanism of the conversion of methane to benzene in chemical vapor infiltration (CVI) based on the concluded reaction pathways from C-species to C-species. The geometry optimization and vibrational frequency analysis of all the chemical species and transition states (TS) were performed with B3LYP along with a basis set of 6-311 +G(d, p), and Gaussian 09 software was used to perform the study. The rate constants were calculated by KiSThelP according to the conventional transition state theory (TST), and the Wigner method was applied to acquire the tunneling correction factors. Then the rate constants were fitted to the modified Arrhenius expression in the temperature range of 800-2000 K. As for the barrierless reactions calculated in this paper, the rate constants were selected from the relating references. Through the energetic and kinetic calculations, the most favorable reaction pathway for benzene formation from methane was determined, which were mainly made of the unimolecular dissociation. The conversion trend from C-species to C-species is mainly guided by a strong tendency to dehydrogenation and the pathways from C-species to C-species are all presumed to be able to produce CH molecule.
采用密度泛函理论（DFT）研究了在化学气相渗透（CVI）过程中甲烷转化为苯的机制，该研究基于从 C 物种到 C 物种的总结反应途径。采用 B3LYP 与 6-311 + G（d，p）基组对所有化学物质和过渡态（TS）进行了几何优化和振动频率分析，并使用 Gaussian 09 软件进行了研究。根据传统过渡态理论（TST），KiSThelP 计算了速率常数，并应用 Wigner 方法获取了隧道校正因子。然后，根据修改后的 Arrhenius 表达式，在 800-2000 K 的温度范围内对速率常数进行拟合。对于本文中计算的无势垒反应，速率常数选自相关参考文献。通过能量和动力学计算，确定了甲烷生成苯的最有利反应途径，主要由单分子解离组成。C 物种到 C 物种的转化趋势主要受脱氢的强烈趋势引导，并且 C 物种到 C 物种的途径都被认为能够产生 CH 分子。
