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Hexamethyldisiloxane (HMDSO) is one of the main impurities in the syngas produced from sewage and landfill plants. In order to utilize this syngas or control the characteristics of the generated silica particles, it is crucial to understand the chemical kinetics of HMDSO combustion. This study investigated the process of HMDSO combustion using synchrotron radiation mass spectrometry (SRMS), gas chromatography (GC), and ReaxFF molecular dynamics simulations. First, the force field used for ReaxFF simulation was validated by comparing the energies of different bond lengths, bond angles, and dihedral angles with the ones from DFT calculations. Good agreements were found. Then, ReaxFF simulations of HMDSO combustion with this force field were conducted under various conditions, which include different equivalence ratios (0.67, 1.0, and 1.5) and temperatures ranging from 2000 to 3500 K. The oxidation characteristics of HMDSO were analyzed, including the evolution of gas products and particle formation. Finally, based on the results from experiments and ReaxFF simulations, the reaction pathways, reaction lists, and reaction kinetics data during HMDSO combustion were obtained. A detailed reaction mechanism was proposed and validated by applying it in modeling the H2/HMDSO/O2 combustion systems. The temperature and part of the gas products such as CO and CO2 as well as SiO could be well predicted. [ABSTRACT FROM AUTHOR]

The pyrolysis kinetics of hexamethyldisiloxane (HMDSO) at various temperatures was studied using the reactive force field (ReaxFF) molecular dynamics simulations. Reaction rate constants and the main pyrolysis pathways were explored at the initial decomposition stage of HMDSO and intermediates decomposition stage. The activation energy and pre‐exponential factor describing the reaction rate constants were obtained and further validated by experimental data and DFT theoretical calculations. The formation of C5H15OSi2 fragment by Si–C bond dissociation was dominant at the initial decomposition stage of HMDSO at the simulation temperatures of 2500–4000 K. The subsequent reaction pathways involved the formation of C5H14OSi2 and C4H11OSi2. After that, the pathways were different for 2500 and 3000 K. At 4000 K, small silicon‐containing fragments were formed, including CH3Si, CH4Si, and C3H9Si, etc. The simulations also revealed that the major hydrocarbons generated during HMDSO pyrolysis were CH3 and CH4. Also, CH4 formation was more important in the end of HMDSO pyrolysis when simulation temperature was over 3500 K. [ABSTRACT FROM AUTHOR]