Quantitative structure–activity relationship and mechanism of ionic liquids inhibiting spontaneous combustion of ferrous sulfide

Ferrous sulfide is one of sulfur corrosion products generated during the transportation and storage of petroleum. It possesses strong spontaneous combustion properties, potentially leading to fires or even explosions in the petrochemical industry. Ionic liquids, as a new class of green compounds, show promising potential for spontaneous combustion inhibition. In this paper, 60 common imidazolium-based ionic liquids are selected as inhibitors, and the inhibition effect and inhibition mechanism of ionic liquids are studied from the microscopic point of view. The results show that among the 60 imidazolium-based ionic liquids, those with the highest inhibition efficiency are [EMIM]C₅H₁₁BF₃, [OMIM]CH₃COO, and [C₁₂MIM]BF₄, and the inhibition efficiencies of the adsorbed molecules are in the following order: H₂O > H₂S > CH₃SH > O₂. An appropriate increase in the length of the alkyl chains on the imidazole ring of ionic liquids, as well as the introduction of substituents, can enhance the activity of the molecules, thereby improving their inhibition efficiency. Based on the structural properties and inhibition effect of ionic liquids, a quantitative structure–activity relationship (QSAR) method using quantum chemical descriptors to predict the inhibition effect of ionic liquids is proposed. Five descriptors are identified as the key factors influencing the inhibition efficiency of ionic liquids, with the prediction effect for O₂ being the most accurate. The results are of great significance for revealing the mechanism of ferrous sulfide spontaneous combustion inhibited and the prevention and control of spontaneous combustion hazards.