Homologue Patterns of Polychlorinated Naphthalenes (PCNs) formed via Chlorination in Thermal Process

Abstract

The chlorination pattern of naphthalene vapor when passed through a 1 cm particle bed of 0.5% (mass) copper (II) chloride (<TEX>$CuCl_2$</TEX>) mixed with silicon dioxide (<TEX>$SiO_2$</TEX>) was studied. Gas streams consisting of 92% (molar) <TEX>$N_2$</TEX>, 8% <TEX>$O_2$</TEX> and 0.1% naphthalene vapor were introduced to an isothermal flow reactor containing the <TEX>$CuCl_2/SiO_2$</TEX> particle bed. Chlorination of naphthalene was studied from 100 to <TEX>$400^{\circ}C$</TEX> at a gas velocity of 2.7 cm/s. Mono through hexachlorinated naphthalene congeners were observed at <TEX>$250^{\circ}C$</TEX> whereas a broader distribution of polychlorinated naphthalenes (PCNs) including hepta and octachlorinated naphthalenes was observed at <TEX>$300^{\circ}C$</TEX>. PCN production was peak at <TEX>$250^{\circ}C$</TEX> with 3.07% (molar) yield, and monochloronaphthalene (MCN) congeners were the major products at two different temperatures. In order to assess the effect of a residence time on naphthalene chlorination, an experiment was also conducted at <TEX>$300^{\circ}C$</TEX> with a gas velocity of 0.32 cm/s. The degree of naphthalene chlorination increased as a gas velocity decreased.