Add p-toluenesulfonic acid and an m-phosphorous compound used as raw materials into a reaction kettle, dropwise adding thionyl chloride while stirring. Controlling the temperature in the reaction kettle at 68-76 ℃ and heating to perform condensation after dropwise addition; inputting water and hydrochloric acid into the reaction kettle, cooling to 0 ℃. The reaction solution generated in the previous step was drawn into the water, vacuum filtration was performed, and centrifuging was used to obtain a crude product, p-toluenesulfonic anhydride. Furthermore, it was inputting ethyl acetate, performing heating reflux, and freezing to perform crystallization, thus obtaining the qualified finished product.
