US Patent 7211704 Method for producing p-dichlorobenzene

In a process for preparing p-dichlorobenzene by nuclear chlorination of benzene and/or chlorobenzene as the starting material with chlorine molecules, chlorination is carried out using aluminum chloride in an amount of 0.1–3 millimols per mol of the starting material and phenothiazines such as 10H-phenothiazine-10-carboxylic acid phenyl ester in an amount of 0.1–0.9 mols per mol of aluminum chloride so as to be a chlorination degree in a range of 1.2–2.5, by which p-dichlorobenzene can be obtained in a high para-selectivity and a short reaction time.