Solubility Of CDMB And CDMA In Reduction Reaction Solvents And Its Application In The Selection Of Reaction Medium

4-chloro-2,5-dimethoxyaniline(CDMA) is an important intermediate of azo organic dyes, it can be prepared for many yellow and red azo dyes by diazotization reaction. At present, CDMA is mainly prepared by the means of chlorination nitration method, which includes four steps: alkylation, chlorination, nitration and reduction. The reduction step can be achieved by iron powder reduction reaction or hydrogenation reduction reaction. Iron powder reduction is usually carried out in aqueous methanol or aqueous ethanol, while hydrogenation reaction is usually carried out in methanol, ethanol, toluene or xylene. The solubility of reactant 4-chloro-2,5-dimethoxynitrobenzene(CDMB) and product CDMA in reaction solvent has important influence on the process of reduction reaction and product separation.The solubility of CDMB and CDMA in aqueous methanol solution, aqueous ethanol solution, methanol, ethanol, toluene, o-xylene, m-xylene and p-xylene were measured by a dynamic method over the temperature range from(278 to 338) K and ambient pressure. Experimental results show that in all the systems, the solubility of CDMB and CDMA increase with temperature. The solubility of CDMB and CDMA in aqueous methanol solution and aqueous ethanol solution decreases with addition of water into the(methanol + water) solvent mixtures and the(ethanol + water) solvent mixtures. CDMB and CDMA are almost insoluble in water. With the scope of the pure solvent, the solubility of CDMB and CDMA in toluene is the biggest. And in the same solvent, the solubility of CDMA is larger than the solubility of CDMB. The Wilson model and the NRTL model were employed to correlate the experimental results. The interaction parameters of the models and the root-mean-square-devation(RMSD) were obtained. The results show that for the system of(CDMB + methanol + water),(CDMB + ethanol + water),(CDMA + methanol + water) and(CDMA + ethanol + water), the Wilson model can describe well the solubility data, but the values of RMSD correlated by the NRTL model are larger. So for these systems, the NRTL model has low accuracy. For the system of(CDMB + pure solvent) and(CDMA + pure solvent), the Wilson model and the NRTL model can both describe well the solubility data.According to the solubility data measured in the experiment, we put forward the optimization of the choice of the CDMB reduction reaction solvent. We chose 0.74 mass fraction aqueous ethanol solution as the solvent for iron powder reduction reaction from the perspective of reaction and cost of production, and chose toluene as the solvent for hydrogenation reduction reaction from the point of view of cost of production and separation of products.