P-ASC Through Combined Chlorosulfonation By HSO₃ Cl And PCl₅

HSO₃Cl was used as the sulfonation and chlorination in the step of p-Acetamino benzene sulfone chloride (P-ASC) in the traditional process. However, now the synthesis technology was died out gradually by the business and government because of the disappointed chlorosulfonated utilization and the kind of refractory inorganic wastewater. The outdated way of the higher molar rate of acetanilide : HSO₃Cl = 4.96 and the lower yield of 71%⁷4% must be replaced. Meanwhile, a new method of chlorosulfonated process has been systematically studied.Based on the literature, the chlorosulfonated mechanism of acetanilide was analyzed and factorial experiments were done. It is found that the higher efficiency in the sulfonation could be reached to 100% nonetheless the chlorination step can't be satisfied. So, a large amount of HSO₃Cl was used to improve the chlorination depth in the factory. In this paper, it was made a distinction between the reagents of sulfonation and chlorination, and the chlorination reagent was mainly studied in the experience. Finally, the new method was determined by choosing the best compatible ability between substitution reagent and HSO₃Cl.According to the different chlorination efficiency of HSO₃Cl, SOCl₂, PCl₃, PCl₅, and the compatibility with those reagents and HSO₃Cl, PCl₅ was ultimately determined as the substitution reagent, to use in the chlorination step. The all process conditions were systematic experimental studied in-deeply, and those factors were analyzed on the basis of the single factors and orthogonal experiments. At last, the optimum conditions were that the molar ratio of n(acetanilide) : n(HSO₃Cl) : n(PCl₅) : n(CCl4) : n(NH4Cl) = 1 : 2.1 : 1.10 : 0.2 : 5.0; the time of sulfonation and chlorination were 1.0h and 3.0h respectively, and the temperature of sulfonation and chlorination were 60±1℃and 72±1℃partly. With the optimum conditions, the highest yield would be reached at 85.4%. What's more, the waste water was reasonable and effective controlled, and brought to the additional value.At the end of reaction, P-ASC was crystallized in the ice-water by dropping, and got the mother liquor, which contained the HCl, H₂SO₄, H₃PO₄, inorganic salt and some organics. It was found that the crystalline precipitation was separated out in the form of organic salt within the mother liquor for standing certain hours, and the amount of the crystal was mainly affected by the acidity of mother solution, the crystalline time and temperature. The crystalline precipitation was deep studied and showed that is the mixture included sulfate and hydrochloride of p-acetamidobenzene sulfonic acid, and was possible to recycle and reuse after desulfurization and dechloridation.