Polycyclic aromatic hydrocarbons (PAHs) play a crucial role in soot inception, interstellar evolution, and nanomaterial synthesis. Although several mechanisms, such as hydrogen-abstraction acetylene/vinylacetylene addition, have previously been proposed, PAH formation and growth are not yet fully understood. We propose an alternate PAH growth mechanism wherein propargyl radical reacts with butadiyne to form larger radicals containing newly fused aromatic rings. Butadiyne is an important intermediate in hydrocarbon oxidation and carbon rich stars, while propargyl is one of the most important resonantly stabilized radicals that persists for long times. Our proposed mechanism is validated by quantum chemical calculations, elementary reaction experiments, laminar flame analysis, and kinetic modeling. Our findings challenge the conventional wisdom that radical site regeneration, being central to PAH growth, requires sequential hydrogen elimination and/or abstraction. In our proposed mechanism, PAH growth does not depend on abundant free radical consumption, and could, therefore, help explain carbonaceous nanoparticle coalescence in radical-deficient reaction environments.
Bibliographical noteKAUST Repository Item: Exported on 2021-08-31
Acknowledgements: Research reported in this work was funded by the Office of Sponsored Research at King Abdullah University of Science and Technology, Chinese Universities Scientific Fund WK2310000069, Key Technologies R&D Program of Henan Province (Grant 212102210614), and National Natural Science Foundation of China (Grant 51906060). We thank Prof. Katharina Kohse-Höinghaus for her valuable discussions
and suggestions in this study. We also appreciate the great help from Prof. Lixia Wei (Guanxi University) and Dr. Beibei Feng,
Dr. Qiang Xu, Ms. Shubao Song, and Prof. Zhandong Wang (University of Science and Technology of China) during our experiments.
ASJC Scopus subject areas
- Materials Science(all)