A SHOCK-TUBE STUDY OF CHLOROBENZENE PYROLYSIS

The pyrolysis of a 2.1% chlorobenzene-Ne mixture was studied behind reflected shock waves over the temperature range 1580-2000 K and total pressures of 0.30-0.50 atm. Time dependent reactant and major product profiles were obtained using time-of-flight mass spectrometry. Acetylene, hydrogen chloride, and diacetylene are the major products. Minor products include C6H2, benzene, and C8H2. The only radical detected is phenyl which appears at early reaction times. HCl is the only chlorine containing product recorded; Cl atoms, Cl2, and species with m/e > 114 were not detected and were assumed to be below the TOF detectability limit which is approximately 10(-10) mol/cm3. The total carbon balance depends upon temperature. The maximum imbalance occurs around 1800 K. C2H2 and C4H2 represent only 25-40% of the carbon resulting from the decomposition of chlorobenzene. C6H2, C6H6 and C8H2 add another 10%; the remaining 50-65% of carbon atoms from C6H5Cl decomposition are lost to soot formation by the end of the observation time (approximately 700 mus). A 60 step mechanism is employed to model the reaction profiles reported herein and some chlorobenzene/hydrogen pyrolysis results from other workers. It is concluded that Cl atoms and chlorinated polycyclic aromatic hydrocarbon radicals play important roles in the soot formation process.