Determination of the influence of water on the SO 3 + CH 3 OH reaction in the gas phase and at the air-water interface

• Published in: Physical chemistry chemical physics : PCCP 2023-06, Vol.25 (23), p.15693-15701
• Main Authors: Ding, Chao, Cheng, Yang, Wang, Hui, Yang, Jihuan, Li, Zeyao, Lily, Makroni, Wang, Rui, Zhang, Tianlei
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/D3CP01245J

Liu ( , 2019, , 24966-24971) showed that at an altitude of 0 km, the reaction of SO with CH OH to form CH OSO H reduces the amount of H SO produced by the hydrolysis of SO in regions polluted with CH OH. However, the influence of the water molecule has not been fully considered yet, which will limit the accuracy of calculating the loss of SO in regions polluted with CH OH. Here, the influence of water molecules on the SO + CH OH reaction in the gas phase and at the air-water interface was comprehensively explored by using high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations. Quantum chemical calculations show that both pathways for the formation of CH OSO H and H SO with water molecules have greatly lowered energy barriers compared to the naked SO + CH OH reaction. The effective rate coefficients reveal that H O-catalyzed CH OSO H formation (a favorable route for CH OSO H formation) can be competitive with H O-assisted H SO formation (a favorable process for H SO formation) at high altitudes up to 15 km. BOMD simulations found that H O-induced formation of the CH OSO ⋯H O ion pair and CH OH-assisted formation of HSO and H O ions were observed at the droplet surface. These interfacial routes followed a loop-structure or chain reaction mechanism and proceeded on a picosecond time scale. These results will contribute to better understanding of SO losses in the polluted areas of CH OH.