Thermodynamics and inhibition mechanism of imidazolium-based ionic liquids for inhibiting spontaneous combustion of iron sulfide

Abstract

The process safety and sustainable development of the petrochemical industry have been seriously threatened by the spontaneous combustion of iron sulfide. In this paper, four kinds of ionic liquids were used to study the inhibition of spontaneous combustion of iron sulfides (FeS, FeS2). The thermodynamic characteristics, inhibition performance, and mechanism of ionic liquids on the spontaneous combustion of iron sulfide have been systematically studied. The results showed that the iron sulfide samples’ overall surface roughness and the proportion of fine particles in the samples increased after the ionic liquid treatment. In the process of oxidative spontaneous combustion, the extrapolation reaction onset temperatures of the samples treated with ionic liquids were enhanced, and the temperature at the samples’ maximum mass loss rate also was delayed. At the same time, the effect of ionic liquids in this process also changed the samples’ reaction mechanism functions, the apparent activation energies, and the mass loss rate. And in all of the experiments, the apparent activation energy of the samples treated with [BMIM][NO3] was enhanced the most by 16.74 kJ/mol, 14.8 kJ/mol, 26.49 kJ/mol, 14.23 kJ/mol, and 13.87 kJ/mol, respectively, while the mass loss rate of the samples treated with this ionic liquid also decreased the most. Therefore, [BMIM][NO3] had the best inhibiting effect among the four ionic liquids in this study. In addition, the results of molecular simulations showed that there is an adsorption process between the ionic liquid and the iron sulfide. In the adsorption process, the ionic liquid dominated the adsorption competition with oxygen molecules, which raises the iron sulfide’s activation energy of the oxidation reaction, thus inhibiting spontaneous combustion.