Solubilities Of NTSNa And NTS In The Sulfuric Acid+water System And Its Application In Related Process Improvement

As the important intermediate of producing dyes and fluorescent brighteners,4,4’-diaminostilbene-2,2’-disulfonic acid(DSD acid) undergoes wide application andan increasing demand all around the world because of its environmental friendlycharacter. Meanwhile, the intermediates produced in the production of DSD are alsoimportant intermediates for dyes. Thus, further research of the steps and intermediatesin the production of DSD acid is meaningful in practice. This article aimed at the newoptimizing process of sulfonation, neutralization and oxidation steps in the productionof DSD. We determined the feasibility of the new process and the parameters of mainpoints by determining the solubilities of related systems, and provided the basic datafor the implement of the new process.First, solubilities of NTS and NTSNa in H2SO4-H2O system was determined, theresult shows that solubilities of the two substances both increase with the increase oftemperature; with the increase of the content of H2SO4, solubilities of NTS andNTSNa decrease at first and increase later, reach the lowest value when the massfraction of sulfuric acid is60%; when the mass fraction of sulfuric acid is less than30%, the solubility of NTS is bigger that that of NTSNa, the discrepancy goes downwith the increase of the content of H2SO4; when the mass fraction of sulfuric acid isbigger than30%, solubilities of NTS and NTSNa are almost equal. According to thedetermination result, we decided the best condition for the separating out of NTS aftersulfonation and appropriate operation range of the new process. Second, thesolubilities of NTSNa in the NTS-H2SO4-H2O system were determined, the influenceof the existence of NTS to the solubility of NTSNa was analyzed. According toobtained data, the paramaters of the key streams in the new sulfonation, neutralizationand oxidation process were designed and calculated. We used the modified Apelblatmodel to correlate the data. The root-mean-square deviation of temperature wasbetween0.24~1.96K.According to the obtained solubilities data, combining the relationship ofmaterial flows in the optimizing process, we got the theoretical values of the specificoperation parameters by analysis and calculation. After that, testing the values byexperiments, we found they were available and effective after appropriate adjustment. This work realized the optimizing process of sulfonation and oxidation step.