Abstract: In response to the "Crude-to-Chemicals" trend in the refining industry and the growing demand for light olefins and aromatics, high-temperature fast catalytic pyrolysis offers an efficient route for converting petroleum hydrocarbons into value-added chemicals. This study investigates the pyrolysis of 1-alkenes, n-alkanes and n-alkylbenzenes with varying carbon numbers as model petroleum hydrocarbons by Pyrolysis-Gas Chromatography-Mass Spectrometry/Flame Ionization Detector (Py-GC-MS/FID). The experiments are conducted under fast pyrolysis conditions, reaching a final temperature of 700℃ at a heating rate of 20℃/ms. The modulation of product selectivity by acidic ZSM-5, acidic USY, and basic CaAl catalysts is systematically examined, with thermal pyrolysis serving as a baseline. The results demonstrate that the selectivity for C2-C4 light hydrocarbons follows the order: ZSM-5 acidic catalyst>CaAl basic catalyst>thermal pyrolysis>USY acidic catalyst, whereas the selectivity for BTX (benzene, toluene, and xylenes) is ordered as: acidic catalysts (ZSM-5 and USY)>CaAl basic catalyst>thermal pyrolysis. Specifically, for 1-alkenes over ZSM-5, the C2-C4 light hydrocarbons selectivity ranges from 31% to 51%, decreasing with increasing carbon number. For n-alkanes, the C2-C4 light hydrocarbons selectivities are 43%~68% over ZSM-5 and 30%~61% over USY. For n-alkylbenzenes over ZSM-5, this selectivity reaches 34%~62%. These trends are attributed to the synergistic effect of ZSM-5's acidic sites and shape-selective channels, which suppress bimolecular side reactions, including hydrogen transfer and oligomerization, and favor monomolecular β-scission into smaller molecules. In contrast, the strong acidity and hierarchical pore structure of USY promote hydrogen transfer and secondary reactions, leading to a higher yield of C5+ alkanes. The CaAl catalyst operates primarily via a radical-chain mechanism, suppressing hydrogen transfer and enhancing olefin selectivity, albeit with limited overall cracking severity. These findings elucidate the intrinsic relationship between hydrocarbon structure, catalyst properties, and product selectivity, providing theoretical and practical insights for the development of high-temperature fast catalytic pyrolysis technologies.

Key words: high-temperature fast catalytic pyrolysis, model compounds, pyrolysis-gas chromatography-mass spectrometry/flame ionization detector, product selectivity, light olefins

摘要： 面向炼化行业“减油增化”及低碳烯烃和轻芳烃需求，高温快速催化裂解已成为将石油烃分子高效转化为高附加值化学品的关键工艺。本工作以不同碳数的1-烯烃、n-烷烃与n-烷基苯为石油烃分子模型化合物，利用裂解-气相色谱-质谱/氢火焰离子化联用仪(Py-GC-MS/FID)在终温700℃、升温速率20℃/ms的高温快速裂解反应条件下，以热裂解为对照实验，系统研究了ZSM-5酸催化、USY (超稳Y型分子筛)酸催化与CaAl碱催化对产物选择性的调控规律。结果表明，C2-C4轻烃的选择性遵循ZSM-5酸催化>CaAl碱催化>热裂解>USY酸催化的变化规律；而BTX轻芳烃的选择性为酸催化(ZSM-5和USY)>CaAl碱催化>热裂解；1-烯烃在ZSM-5上对C2-C4轻烃的选择性为31%~51%，且随碳数升高而下降；n-烷烃在ZSM-5与USY上对C2-C4轻烃的选择性分别为43%~68%和30%~61%；n-烷基苯在ZSM-5上对C2-C4轻烃的选择性为34%~62%。上述规律源于ZSM-5的酸性位与孔道限域协同抑制了氢转移和低聚等双分子副反应，偏向单分子β-断裂生成小分子；USY的强酸性与多级孔道促进氢转移和二次反应，使C5+烷烃比例升高；而CaAl以自由基链式路径为主，抑制氢转移并提升烯烃选择性，但裂解深度受限。上述结果揭示了“石油烃分子结构-催化剂性质-产物选择性”的内在关联机制，对于石油高温快速催化裂解技术的开发具有一定的理论与实践意义。

关键词: 高温快速催化裂解, 模型化合物, 裂解-气相色谱-质谱/氢火焰离子化联用, 产物选择性, 低碳烯烃