Detailed Modeling of the Pyrolysis of Trichloroethene: Formation of Chlorinated Aromatic Species

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Abstract
Comprehensive product yield determinations from the high-temperature, gas-phase pyrolysis of trichloroethene (C2HCl3) using two fused silica tubular flow reactors coupled to in-line gas chromatographic-mass spectrometry analyses are reported. Initial decomposition was observed at 1000 K with formation of HCl and C2Cl2. Pronounced molecular growth was observed at higher temperatures as evidenced by the formation of C2Cl2, C4Cl4, and C6Cl6 (cy) as major (≥5mole%) products and C4Cl2, C4Cl6, C6HCl5 (cy), C8Cl6 (cy), C8Cl8 (cy), C10Cl8 (cy), and C12Cl8 (cy) as minor (≤5mole%) products. The effects of reactor surface area to volume (S/V) ratio were evaluated by conducting detailed product analyses with 0.1 cm i.d. and 1.0cm i.d. reactors. Under the higher S/V ratio, C2HCl3 decomposition was increased by an order of magnitude and product distributions suggested that radical-radical and radical-atom recombination rates were enhanced. Product yields under reduced S/V ratio indicated that yields of perchlorinated aromatic and perchlorinated PAH species were a factor of 10 larger than observed for higher S/V ratios. A detailed reaction mechanism is presented for the 1 cm i.d. reactor data describing molecular growth up to the formation of C8Cl6 (cy) and C8Cl8 (cy). Comparison of predicted versus experimental major and minor species profiles are presented, with generally good agreement. Important radical-molecule addition reactions leading to molecular growth are identified using sensitivity analysis and production rate calculations.