Process for producing dichlorodiphenylsulfone

Dichlorodiphenylsulfone is prepared with an enhanced yield by (1) dehydration-condensing chlorobenzene with 4-chlorobenzenesulfonic acid; (2) adding water to the resultant reaction product mixture in a 4-chlorobenzenesulfonic acid/water molar ratio of 1:0.8 to 1:2 to convert the non-reacted 4-chlorobenzenesulfonic acid to monohydrate thereof and allow the resultant monohydrate to precipitate; (3) recovering the precipitated 4-chlorobenzenesulfonic acid monohydrate; (4) collecting the reaction product consisting of dichlorodiphenylsulfone; and optionally (5) dehydrating the recovered 4-chlorobenzenesulfonic acid monohydrate and returning the dehydrated 4-chlorobenzenesulfonic acid to the dehydration-condensing step (1).