The Solubility Determination Of Related Components In The DSD Acid Synthesis And The Selection Of Oxidation Medium

4,4'-diaminostilbene-2,2'-disulfonic acid(DSD)is widely used as green chemical intermediate in producing fluorescent brightener,detergent and dyestuff.The production process of DSD production includes three stages: sulfonation,oxidation,and reduction.Air oxidizing 4-nitrotoluene-2-sulfonic acid(NTS)to 4,4'-dinitrostilbane-2,2'-disulfonic acid(DND)and 4,4'-dinitrostilbene-2,2'-disulfonic acid(DNS)is main oxidation process which is usually carried out in the alkaline aqueous solution with many side reactions,large amount of wastewater and relative low yield.Numerous researchers have been focused on improving NTS oxidation process and aqueous organic solutions have been proved to be feasible in replacing traditional aqueous solution due to the following advantages: mild reaction condition,high yield and easy product separation.Therefore,it is very important to choose suitable aqueous organic solution for improving the oxidation process.In this work,the solubility of DNDNa in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution were determined in order to choose a more suitable aqueous organic solution based on previous solubility of NTSNa and DNSNa.The results showed that both solubility of DNDNa increase with temperature increasing in the investigated binary solvent system.The solubility of DNDNa first increases and then decreases afterwards with increasing solute-free ethylene glycol monoethyl ether and solute-free ethylene glycol monobutyl ether mass fraction.DNDNa has the largest solubility at 0.4000 mass fraction aqueous ethylene glycol monoethyl ether solution and 0.6000 mass fraction aqueous ethylene glycol monobutyl ether,respectively.The use of above mixed-solvents shows the phenomenon of synergistic effect in the determined DNDNa-water-ethylene glycol monoethyl ether and DNDNa-water-ethylene glycol monobutyl ether systems.The solubility of NTSNa,DNDNa and DNSNa in glycol dimethyl ether were determined to seek a more suitable organic solvents in view of handle reaction solvents difficultly.The solubility of NTSNa,DNDNa and DNSNa increase with temperature increasing and first increase and then decrease afterwards with increasing solute-free glycol dimethyl ether.They have the largest solubility at 0.6000 mass fraction aqueous glycol dimethyl ether.The experimental data obtained in this work were correlated with electrolyte non-random two-liquid(E-NRTL)model which provides athermodynamically framework for representation phase behavior of mixed-solvent electrolyte systems.By all these data,at the suitable oxidation temperature from 320 to 330 K,the about 0.6000 mass fraction aqueous glycol dimethyl ether is a more suitable oxidation solvent in which NTSNa has the largest solubility and favorable for the oxidation reaction.