The chlorination pattern of naphthalene vapor when passed through a 1 cm particle bed of 0.5% (mass) copper (II) chloride ($CuCl_2$) mixed with silicon dioxide ($SiO_2$) was studied. Gas streams consisting of 92% (molar) $N_2$, 8% $O_2$ and 0.1% naphthalene vapor were introduced to an isothermal flow reactor containing the $CuCl_2/SiO_2$ particle bed. Chlorination of naphthalene was studied from 100 to $400^{circ}C$ at a gas velocity of 2.7 cm/s. Mono through hexachlorinated naphthalene congeners were observed at $250^{circ}C$ whereas a broader distribution of polychlorinated naphthalenes (PCNs) including hepta and octachlorinated naphthalenes was observed at $300^{circ}C$. PCN production was peak at $250^{circ}C$ 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 $300^{circ}C$ with a gas velocity of 0.32 cm/s. The degree of naphthalene chlorination increased as a gas velocity decreased.