| 3-Bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde are important fine chemical intermediates,which were used in chemical,pharmaceutical,agricultural products,cosmetics and other industries.It plays a significant role in pharmaceutical synthesis and chemical production.p-Hydroxybenzaldehyde bromided products are mainly used to synthesize methyl vanillin,ethyl vanillin and other important synthetic fragrances,as well as synthetic trimethoprim(TMP)sulfonamide synergists and bactericides in cosmetics and chemical systems.The market demand is huge.At present,p-hydroxybenzaldehyde is brominated to produce 3-bromo-4-hydroxybenzaldehyde.When the product is obtained,by-product 3,5-dibromo-4-hydroxybenzaldehyde is easily produced,resulting in low product selectivity and low yield,which makes traditional separation and purification methods difficult.Solvent crystallization as common separation method has the advantages of low energy consumption,environmental protection,no pollution,stability and reliability.It enables safe and efficient separation.Based on the solvent crystallization separation method,the solid-liquid phase equilibrium of different systems is studied in this paper,which provides basic data for the separation of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde.The equilibrium solubilities of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde in methanol,ethanol,n-pentanol,n-octanol,ethylene glycol,cyclohexane,ethyl acetate,acetonitrile,n-propanol,n-butanol,N,N-dimethylformamide(DMF),dimethyl sulfoxide(DMSO),1,4-dioxane,isopropanol,isobutanol and water were measured by using static method.With the gradual increase in temperature,the solubility of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde in pure solvents increased to varying degrees.At the same temperature,the solubility order of 3-bromo-4-hydroxybenzaldehyde is as follows(n-octanol,DMF)>1,4-dioxane>(DMSO,n-pentanol)>n-butanol>isobutanol>ethyl acetate>n-propanol>isopropanol>ethanol>acetonitrile>ethyl acetate>methanol>cyclohexane>water,and the solubility order of 3,5-dibromo-4-hydroxybenzaldehyde is as follows:1,4-dioxane>(DMF,n-octanol)>n-pentanol>DMSO>ethyl acetate>n-butanol>isobutanol>n-propanol>isopropanol>(ethanol,ethylene glycol)>acetonitrile>methanol>cyclohexane>water.Moreover,apelblat model,?h model,NRTL model and Wilson model are used to correlate the measured solubility data.The maximum value of average relative deviation(RAD)is 2.86%,and the root mean square deviation(RMSD)value is not more than 8.40×10-4.The model is generally more suitable for solubility data correlation.In addition,the KAT-LSER equation is used to explain the solvent effect on the solubility of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde in pure solvents.In addition,the mixing properties of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde in pure solvents were calculated.The equilibrium solubilities of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde products in(ethanol+water),(n-propanol+water),(acetonitrile+water)and(DMF+water)solvent mixtures were measured by using static method.As the temperature rises,the solubility increases continuously,while with the increase of the water mass fraction in the mixed solvent,the solubility decreases significantly.Moreover,the Jouyban-Acree model,Van't Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model are used to correlate the solubility data that obtained the function parameters of each model.The RAD and RMSD were no more than 3.83%and 4.69x10-4,respectively,and the Jouyban-Acree model is more suitable than the other two models.Besides,the standard enthalpy of dissolution and transfer properties of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde in mixed solvents were calculated.The solid-liquid phase equilibria of 3-bromo-4-hydroxybenzaldehyde+3,5-dibromo-4-hydroxybenzaldehyde+n-propanol and 3-bromo-4-hydroxybenzaldehyde+3,5-dibromo-4-hydroxybenzaldehyde+ethyl acetate at 298.15 K,308.15 K and 318.15 K were measured by Schreinemaker's method,and the ternary phase diagrams were obtained simultaneously.As the temperature gradually increases,the co-crystallization zone shrinks.The crystallization region of 3,5-dibromo-4-hydroxybenzaldehyde was larger than that of 3-bromo-4-hydroxybenzaldehyde at a given temperature,especially in 3-bromo-4-hydroxybenzaldehyde+3,5-dibromo-4-hydroxybenzaldehyde+n-propanol system,and n-propanol was more faviourable in separation of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde.In addition,the solubility data was correlated with the NRTL model and Wilson model.The maximum RMSD of the two models were 1.777×10-3 and 5.055×10-3 respectively,which illustrated that the NRTL model colud be correlate the 3-bromo-4-hydroxybenzaldehyde+3,5-dibromo-4-hydroxybenzaldehyde+n-propanol/ethyl acetate ternary systems accrurately. |
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