Experimental and computational study of diethyl sulfide pyrolysis and mechanism

Abstract

The pyrolysis of diethyl sulfide (C2H5SC2H5), a simulant for mustard chemical warfare agents, was studied in a turbulent flow reactor with extractive gas composition analysis by GC/MS and FTIR. Experiments were performed at approximately atmospheric pressure for four different temperatures between 630 and 740°C with maximum residence times between 0.06 and 0.08s. Temperature and species profiles were obtained on the centerline of the reactor. The mixing characteristics in the reactor were determined by using carbon monoxide as a tracer. 80% destruction of diethyl sulfide was observed for the experiment at the temperature of 740°C and the residence time of 0.06s. The following species were quantified: diethyl sulfide, ethylene, methane, ethane, acetylene, carbon disulfide, and thiophene. In addition, ethanethiol, methyl thiirane CH3-(Cy-CH-CH2-S), ethyl methyl disulfide, and diethyl disulfide were identified but not quantified. A light yellow solid containing sulfur condensed in sampling probes. Thermochemical properties for all species and a detailed mechanism were developed for modeling the reaction system. Thermodynamic and kinetic parameters were based on density functional theory and ab initio calculations using isodesmic work reactions for enthalpies. Kinetic parameters for chemical activation and unimolecular dissociation reactions were determined with multi frequency quantum RRK analysis for k(E) and master equation for fall-off. Important reactions were identified by sensitivity analysis and reaction pathway analysis of the mechanism. Model predictions show overall good agreement with experiment.