Study on Autocatalytic Decomposition of Dimethyl Sulfoxide (DMSO) III: Investigations Regarding the Main Decomposition

It is important to know the entire decomposition mechanism of energetic materials for safety purposes, such as the assessment, control, mitigation, and prevention of thermal hazards. Dimethyl sulfoxide (DMSO) is a common solvent that is widely used in laboratories and industrial applications; however, several severe incidents due to its decomposition have been reported. The decomposition mechanism of DMSO has been studied for several years; however, it has not been sufficiently clear until now. To elucidate the complicated decomposition pathway, analyses of materials from DMSO decomposition were conducted. Several new chemical bonds were found in the decomposition products through gas chromatography–mass spectrometry (GC-MS) analysis, which suggests a radical reaction. Atomic sulfur S(0) or organic divalent sulfur S(II) was found on the inner wall of the vessel after decomposition, which indicates that the sulfur atom in DMSO was reduced during decomposition. In addition to the chemical analyses, a kinetic study was carried out for the data obtained through isothermal heating tests. All of the DMSO samples with or without the studied impurities showed similar activation energies for the main decomposition. Autocatalysts in DMSO decomposition are proposed to work not by accelerating the main decomposition but rather by shortening the induction period. It is proposed that the main decomposition of DMSO occurs via a radical pathway.