Oxidation chemistry of carbon disulfide (CS2) and its interaction with hydrocarbons in combustion processes

This thesis presents a series of scientific studies exploring the oxidation chemistry of carbon disulfide (CS2) and its interaction with hydrocarbons in combustion systems. The results illustrate the extreme flammability of CS2 even at low temperature (self-ignition temperature at 363 K under ambient pressure). The thesis proposes a comprehensive oxidation mechanism that works over a wide range of atmospheric and combustion conditions with and without moisture. The thesis also provides experimental validation on the promotion of CS2 on the ignition of methane. Experiments involving CS2 oxidation in combustion processes have been conducted with tubular-flow (TFR) and jet-stirred (JSR) reactors to provide experimental validation for the proposed mechanism. Online Fourier transform infrared (FTIR) spectroscopy served to identify and quantitate the product species and to obtain the detailed species conversion profiles during the combustion process. Low ignition temperature of CS2 of 860 K in TFR and 710 K JSR, with residence time at 0.3 s under ambient pressure, implies the extreme flammability of CS2. The presence of moisture exhibits no effect on the oxidation of CS2 for ignition temperature and species profile at below 1100 K, although moisture converts CO into CO2 at higher temperature (> 1200 K). Co-oxidation experiments of CH4/CS2/O2 in JSR illustrate the promotion effect of CS2 on the ignition of methane. Quantum calculations afford the investigation of primary steps governing the OH-initiated oxidation of CS2 in the atmosphere. We also propose a comprehensive oxidation mechanism of CS2 in combustion systems. The thesis suggests the intersystem crossing (ISC) between triplet and singlet pathways to explain the extreme flammability of CS2, in analogy to the controlling steps operating for other reduced sulfur species. DFT calculations examine the interplay between the SH radical and C1 - C4 hydrocarbons to demonstrate the distinct inhibition and promotion effects