Patent ID: 8257557

Claim:
A dehydration method for removing water from a hydrolysis reaction mixture containing phenol, unreacted monochlorobenzene, hydrogen chloride, and unreacted water generated when monochlorobenzene is hydrolyzed to produce phenol, said method for dehydrating the hydrolysis reaction mixture comprising the steps of supplying a hydrolysis reaction mixture to a distillation tower, supplying a liquid containing monochlorobenzene to the tower top portion of said distillation tower, and removing 99.95% or more of the water in the hydrolysis reaction mixture together with monochlorobenzene in the form of a vapor from said tower top portion by distillation: wherein the total amount of the monochlorobenzene supplied to said tower top portion of said distillation tower and the monochlorobenzene contained in the hydrolysis reaction mixture is 0.4 moles or more per mole of the water in the hydrolysis reaction mixture supplied to said distillation tower, and that the amount of the monochlorobenzene in the vapor obtained from said tower top portion is 0.39 moles or more per mole of the water in the hydrolysis reaction mixture, wherein the water and monochlorobenzene distilled from said tower top portion of said distillation tower is separated into a water phase mainly comprising water and an oil phase mainly comprising monochlorobenzene, and part of the oil phase is supplied to said tower top portion of said distillation tower, and the phenol is separated from the water and the hydrogen chloride through only one distillation operation.