The invention discloses a phosgenation reactor and a method for preparing an
isocyanate monomer by using the phosgenation reactor. The phosgenation reactor comprises an inner material inlet
pipe, an outer material inlet
pipe, a mechanical stirring rotation shaft, a rotation area and a kettle body, wherein the rotation area comprises a support structure, a rotation area filler block, an upper material outlet device and a lower material outlet device, the inner material inlet
pipe and the outer material inlet pipe are coaxially arranged from inside to outside, the upper material outlet device and the lower material outlet device are arranged in parallel, are connected through the support structure, and are respectively communicated to the outer material inlet pipe and the inner material inlet pipe, the rotation area filler block is filled between the upper material outlet device and the lower material outlet device, the upper material outlet device is connected to the mechanical stirringrotation shaft, and the kettle body is provided with a
gas phase material outlet, a
liquid phase material outlet, a
gas phase material inlet and a
liquid phase material inlet. According to the present invention, by pre-treating the
hydrochloride solution in the reactor, the salt forming concentration and the quality of the
hydrochloride solution are improved while the rapid removal of
hydrogen chloride gas during the phosgenation is achieved, such that the generation of chlorination by-products is effectively reduced, and the product separation difficulty is reduced.