The gas‐phase thermolyses of di‐, tri‐ and tetrachloroethene in hydrogen between 828 and 1050 K

Publisher Website
Google Scholar
Abstract
The thermolyses in hydrogen of 3–6 vol. % of 1,1‐dichloroethene, (E)‐1,2‐dichloroethene, trichloroethene and tetrachloroethene have been examined in a tubular flow reactor at atmospheric pressure between 828 and 1068 K. Major products are HCl, lower chlorinated ethenes, ethyne, ethene, ethane and methane. Chlorinated benzenes, major products in the straight pyrolysis of these compounds, are formed in only small amounts, the reasons for which are discussed. Dechlorination occurs in part via a chain mechanism involving H‐atom addition and ipso substitution of Cl. A second route, molecular elimination of HCl, also occurs but appears to become less important for the more chlorinated substrates. At 880 K, addition of a H atom to the monochloro‐substituted carbon of C2HCl3 takes place ca. 8 × more rapidly than it does to the dichloro site. The hydrogen‐atom concentration is somewhat greater than that calculated from equilibrium dissociation of H2 and varies by a factor of ca. 4 for the various substrates. Differences in hydrogen‐atom concentration are larger at lower temperatures, apparently due to the presence of relatively unreactive radicals in some systems, which lead to increased chain termination.