Put 98% sulphuric acid in the oil bath sulfonated cauldron and add 99% aniline to it after stirring the sulphuric acid for 1 hour. Raise the temperature of the cauldron to 160℃. Launch the vacuum system and make the vacuum degree0.053MPa in the cauldron.Then the temperature of the cauldron is raised to 200℃. The heat preservation lasts for half an hour before the temperature is raised to 260℃ and the completion of heat preservation to transposition. At this time cool and close the vacuum system, keep 10 minutes and discharge the vacuum in the cauldron, gradually cooling to 80℃ . Add water and stir it before putting in the storage tank. In the storage tank, the material is heated to 70-80 degrees centigrade. Add the sodium carbonate and neutralize it to pH=7.0 - 7.5 before moving into the neutralization cauldron with the batch mother liquid. The relative density of water is adjusted to 1.12 before being heated to boiling. Then the activated carbon will be added and stirring is made for half an hour followed by the thermal filtration. The filter cake is washed with water, and the filtrate is steamed to a relative density of 1.18. Afterwards, it is put into the crystallizer and cooled to 30 ℃ in 8 hours followed by the centrifuge filtration. The filtrate can be used as the next batch of mother liquid and the filter cake is p-aminophenylsulfonic acid.
