Abstract: 1,3-dihalobenzene, particularly 1,3-dichlorobenzene, is produced in high efficiency from a mixture containing the subject compound and its corresponding 1,4-isomer by a special process in which the dihalobenzene mixture is treated with polyethylene glycols of varying molecular weight and the resulting slurry is filtered to remove a complex of 1,4-dihalobenzene and polyethylene glycol as a solid and the 1,3-dihalobenzene as the filtrate.The 1,4-dihalobenzene complexed with the polyethylene glycol can be recovered by a flash distillation under vacuum and the residue containing the polyethylene glycol can be recycled.The purity of the 1,3-dihalobenzene obtained by this process can further be improved by subjecting the product obtained after the polyethylene glycol treatment to a low temperature crystallization process where 1,3-dihalobenzene can be selectively crystallized to a purity of above 99%.

Abstract: A process for synthesizing 3,5-dichloroalkylbenzene and recovering 1,3-dichlorobenzene from a starting mixture of 1,3- and 1,4-dichlorobenzenes. The process includes the sequential steps of selectively alkylating the 1,3-dichlorobenzene in the starting mixture; isomerizing a portion of the 2,4-dichloroalkylbenzene produced to 3,5-dichloroalkylbenzene; separating the 1,4-dichlorobenzene from the isomeric mixture of dichlorocumenes; and selectively transalkylating the dichlorocumenes to yield alkylbenzene, 3,5-dichloroalkylbenzene and 1,3-dichlorobenzene. By selectively alkylating only a portion of the 1,3-dichlorobenzene, the reaction products are obtained in good yield and substantially free of undesirable by-products.

Abstract: Polychlorobenzenes are selectively dechlorinated to dichlorobenzenes and monochlorobenzene in the vapor phase in the presence of a sulfided palladium or platinum catalyst. The reaction may be carried out at a temperature of from 225.degree. C. to 450.degree. C., preferably at atmospheric pressure, with an equimolar ratio of hydrogen and polychlorobenzene, and a space velocity of 0.5 to 5 wt. feed/wt. catalyst-hour. Only small amounts of benzene are formed.