A detailed kinetic study of the thermal decomposition of tetraethoxysilane

Abstract

This work presents a detailed kinetic modelling study of the thermal pyrolysis of tetraethoxysilane (TEOS). A chemical mechanism is proposed based on an analogy between the hydrocarbon branches attached to the central silicon atom and an existing mechanism for the decomposition and combustion of ethanol. Important reaction pathways are identified through element flux and sensitivity analyses. It was found that the key reaction routes are the step-wise four-centre molecular decomposition of TEOS to form silanols and ethylene: Si(OH)n(OC2H5)m→Si(OH)n+1(OC2H5)m−1+C2H4 (n+m=4) and the barrier-less CC bond cleavage of the ethoxy branches: Si(OH)n(OC2H5)m→Si(OH)n(OC2H5)m−1(OCH2)+CH3 (n+m⩽4). Rate constants were calculated using conventional and variational transition state theories (TST and VTST) for all the reactions in the first route and for the methyl radical removal from Si(OH)3(OC2H5) in the second route. The calculated results are similar to the rate constants of the corresponding ethanol reactions, providing support for the analogy with the ethanol decomposition. Simulations using the proposed mechanism are shown to be consistent with experimental data for the decomposition of TEOS.