DFT study of the formation mechanism of anthraquinone from the reaction of NO2 and anthracene on NaCl clusters: the role of NaNO3

Abstract

Polycyclic aromatic hydrocarbons (PAHs) and oxygenated-PAHs are globally worrisome air pollutants because of their highly direct-acting mutagenicity and carcinogenicity. The formation of oxygenated-PAHs is of crucial importance for the prevention of their atmospheric pollution successfully. In this paper, the formation mechanism of oxygenated-PAHs from the heterogeneous reaction of NO₂ with anthracene on the surface of NaCl was studied by density functional theory (DFT) calculations. At first, the various adsorption configurations of NO₂ and N₂O₄ on NaCl were investigated. The chemical conversion mechanisms among these configurations were also investigated. It is found that these structures can easily interconvert due to their low energy barriers. NaNO₃ was found to be the main product of the reaction of NO₂/N₂O₄ on NaCl. Then the oxidation mechanism of anthracene by NO₂ on the NaCl surface showed that NaNO₃ is able to oxidize anthracene and plays a catalytic role in the reaction process. This means that the formation of NaNO₃ is very important to promote the formation of 9,10-anthraquinone from the heterogeneous reaction of NO₂ with anthracene. Our calculations also showed that the introduction of water can greatly accelerate this reaction process.