According to Chinese patent No. CN-87106023, trichloroisocyanuric acid (TCCA) and dichloroisocyanuric acid (DCCA) are prepared by two-stage continuous chlorination using cyanurate and chlorine as raw materials.
The side reactions occurring at this time are:
The process of using cyanurate solution and chlorine as raw materials to continuously prepare trichloroisocyanuric acid and dichloroisocyanuric acid through two-stage continuous chlorination is carried out as follows: the raw materials required for the reaction are added to the first-stage reactor And overflow into the second-stage chlorination reactor through a pipeline. The characteristic of this process is that the first-stage reactor, a circulating pump and a jet pump constitute the outer loop of the first-stage chlorination reaction system. It is connected in series with another bubbling stirred reactor to form a two-stage chlorination reaction system. Another feature of this process is that the second-stage chlorination reactor is directly connected to the atmosphere through a pipe, and air can enter the second-stage reactor. Through the automatic compensation effect of the atmosphere, the reactor works under normal pressure.
The Chinese patent method is also characterized in that the second-stage chlorination reactor is connected to the inlet of the jet pump through a pipeline, so that the tail gas of the second-stage reactor can enter the first-stage reaction system. According to an embodiment: an aqueous solution of trisodium cyanurate with a concentration of 5-9% is continuously added to the first-stage reactor. The addition speed is such that the residence time in the reactor is between 1-3 hours. The first stage reaction temperature is 5-30°C. Then the raw materials enter the second-stage chlorination reactor through the first-stage chlorination reactor. At the same time, chlorine gas with a purity of 95% is continuously added to the second-stage chlorination reactor, and the chlorination reaction is carried out under the action of stirring and bubbling. The temperature of the second stage reactor is controlled at 5-25°C. By controlling the ratio of cyanurate solution and chlorine gas, the pH of the first-stage reactor is stabilized between 8-13. PH=3,5 in the second stage reactor.