Solubility and selective oxidation of 2-chloroethyl ethyl sulfide in imidazole-based ionic liquids

Abstract

In this study, a novel decontamination method against mustard agent simulant 2-chloroethyl ethyl sulfide (CEES) was conducted with 30% H2O2 aqueous solution in 1-butyl-3-methylimidazolium based ionic liquids (ILs). More than 99% of the CEES was oxidized within H2O2/[BMIm]HCO3 at a concentration of 20mgmL−1 in 30min with the corresponding sulfoxide yield more than 97%. Decontamination was effective at very low temperatures (−32°C). [BMIm]HCO3 can be recycled 4 times without significant decrease in decontamination efficacy. The decontamination efficacy against CEES was mainly depended on the hydrophilic-hydrophobic property and the ability of activating H2O2. The singlet oxygen (1O2) generated chemically in H2O2/[BMIm]HCO3 was able to oxidize CEES to corresponding 2-chloroethyl ethyl sulfoxide (CEESO) and ethyl vinyl sulfoxide (EVSO). The ILs was oxidized by the reaction intermediate to 2-imidazolone, which in turn inhibited the formation of corrosive 2-chloroethyl ethyl sulfone (CEESO2). The influencing factors about imidazole-based ILs hydrogen-bond basicity (β), ILs alkyl chain length, oxidant/CEES mole ratio, reaction temperature and ILs reusability of the decontamination system were also checked.