The chlorination pattern of naphthalene vapor when passed through a 1 cm particle bed of 0.5% (mass) copper (II) chloride (CuCl2) mixed with silicon dioxide (SiO2) was studied. Gas streams consisting of 92% (molar) N2, 8% O2 and 0.1% naphthalene vapor were introduced to an isothermal flow reactor containing the CuCl2/SiO2 particle bed. Chlorination of naphthalene was studied from 100 to 400 °C at a gas velocity of 2.7 cm/s. Mono through hexachlorinated naphthalene congeners were observed at 250 °C whereas a broader distribution of polychlorinated naphthalenes (PCNs) including hepta and octachlorinated naphthalenes was observed at 300 °C. PCN production was peak at 250 °C 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 300 °C with a gas velocity of 0.32 cm/s. The degree of naphthalene chlorination increased as a gas velocity decreased.