Study of the Thermal Degradation of Hexachlorobenzene in the Presence of a Hydrogen Donor (CH4)

Abstract

ABSTRACT In this paper, laboratory results and theoretical studies concerning the high-temperature gasphase thermal decomposition of hexachlorobenzene in the presence of a hydrogen donor (methane) are reported. The reaction was studied in tubular reactors under a pressure of one bar, with mean residence times of 0.4, 1.2 and 2.4 s, in the temperature range 900-1200°C. Studies of the effect of methane concentration on the conversion of Cl2 into HCl suggest that the oxygen concentration, the reaction duration and temperature play an important role in the conversion of chlorine to hydrochloric acid. During pyrolysis under a nitrogen atmosphere, total conversion is reached at 1200°C, with a Cl/H ratio lower than 0.15, and a residence time of the order of 2 to 3 s. However, this technique is not desirable, due to important amounts of soot formed in the cold part of the reactor as well as to graphitic carbon deposition on the reactor walls. In the presence of oxygen, the chlorine conversion into hydrogen chlori...