Kinetic Modeling of Pyrocarbon Deposition Obtained by Propane Pyrolysis

摘要

A detailed kinetic mechanism modeling gas and surface reactions involved in pyrocarbon deposition by propane pyrolysis (CVD) was recently proposed. Simulated results were compared with experimental data obtained with a perfectly stirred reactor at low pressure (20 torr). The kinetic mechanism, which is comprised of 608 gas and 275 surface elementary steps, is efficient to predict both pyrocarbon deposition rate and gas phase composition for temperature ranging from 1173 to 1323 K, residence time ranging from 0.5 to 4 seconds and surface to volume ratio ranging from 20 to 170 cm~(-1). In this paper, we discuss the main pyrocarbon deposition pathways using flow rate and sensitivity analysis. In our experimental conditions, pyrocarbon is mostly formed by deposition of small unsaturated species (acetylene and ethylene) and methyl radicals. The pyrocarbon deposition rate is controlled by mole fractions of H, CH_3, C_2H_2 and C_2H_4 in the gas phase and by the value of the kinetic rate of a few key surface reactions.