| 4,4'-Dinitrostibene-2,2'-disulfonic acid is an important intermediate for producing several dyes and optical brighteners. This material is required in large amounts, but the present method of preparing 4,4'-Dinitrostibene-2,2'-disulfonic acid is behindhand. This paper describes a new process for preparing 4,4'-Dinitrostibene-2,2'-disulfonic acid: p-Nitrotoluene was sulfonated by gaseous sulfur trioxide to preduce p-nitrotoluene-2-sulfonic acid;4,4'-Dinitrostibene-2,2'-disulfonic acid was prepared from p-nitrotoluene-2-sulfonic acid by oxidation of sodium hypochlorite in NaOH water solution.In the experiment of sulphonation, the temperature of adding SO3, heat preserving temperature, reaction time, the analytical method and purification of production have been investigated;the optimum conditions were determined. 31g p-nitrotoluene has been added in the reactor, aerate 1.1 ratio SO3 at 95 ℃ 1 hr, heat up to 125 ℃,maintain 20 min. At result, p-nitrotoluene-2-sulfonic acid was produced. The yield was 97%.In the experiment of oxidation, the temperature of reaction, the concentration of p-nitrotoluene-2-sulfonic acid, the dosage of NaClO and NaOH have been investigated;the optimum conditions were determined. 3.9g p-nitrotoluene-2-sulfonic acid was added to reactor, neutralization, add 2.7g NaOH;21g NaClO was dropped in 40 mins, keep the temperature at 65 ℃. When the reaction finished, maintain the temperature at 70℃, cooling, salt out the 4,4'-Dinitrostibene-2,2'-disulfonic acid. The yield was 82%.
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