Solubility of disodium 4,4′-dinitrobibenzyl-2,2′-disulfonate in aqueous organic solutions and its effects on the oxidation reaction of DSD acid synthesis

The solubility of disodium 4,4′-dinitrobibenzyl-2,2′-disulfonate (DNDNa) in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution was measured over the temperature range from 278 to 334 K at atmospheric pressure by a dynamic method. The solubility of DNDNa in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution increased with temperature over all solvent mixture compositions investigated. A synergistic effect on DNDNa solubility was observed with the maximum solubility at solute-free mass fraction of ethylene glycol monoethyl ether w30=0.6003 and solute-free mass fraction of ethylene glycol monobutyl ether w40=0.4054 , respectively. The solubility data were correlated using the electrolyte non-random two-liquid model and model parameters were determined simultaneously. It was found that around 0.4 (solute-free mass ratio) ethylene glycol monobutyl ether solution is suitable as the reaction medium in oxidation 4-nitrotoluene-2-sulfonic acid to 4,4′-dinitrostilbene-2,2′-disulfonic acid. The effect of different aqueous organic solutions on the oxidation reaction was discussed.