High-temperature gas-phase kinetics of the thermal decomposition of tetramethoxysilane

Abstract

Abstract The decomposition of tetramethoxysilane (Si(OCH3)4, TMOS) was studied in shock-tube experiments in the 1131–1610\u202fK temperature range at pressures ranging from 1.9 to 2.3\u202fbar behind reflected shock waves combining gas chromatography/mass spectrometry (GC/MS) and high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS). The initial reaction is a four-center elimination to form methanol. At elevated temperatures, TMOS also decomposes via a O–C bond scission forming a methyl (CH3) and the corresponding OSi(OCH3)3 radical. The main observed products were methane (CH4), methanol (CH3OH), ethylene (C2H4), and ethane (C2H6). The yields of these products increase with temperature. A kinetics mechanism from literature (Chu et\xa0al. 1995), which quantitatively accounts for the observed products in the decomposition of TMOS, was adopted and updated. The mechanism contains 13 silicon species and 24 reactions with silicon-containing species. It was combined with the methanol mechanism of Burke et\xa0al. (2006). The measured global rate constant for TMOS decomposition was found to be koverall[TMOS→products]\u202f=\u202f2.9\u202f×\u202f1011exp(−\u202f225\xa0kJ\xa0mol−1/RT)s−1.