Separation And Purification Of Iodoaniline Isomers By Crystallization

By using laser scattering technique,the solubility data of o-iodoaniline and p-iodoaniline in pure solvents（water,methanol,ethyleneglycol,ethylacetate,hexane,cyclohexane,dichloromethane,trichloromethane and tetrachloromethane）from 273K to 333K was measured.And the data was correlated with NRTL model,Apelblat equation,λh equation and van’t Hoff equation.The average relative deviations in thep-iodoaniline system were 12.40%（NRTL）,4.501%（Apelblat）,6.105%（λh）,in o-iodoaniline system were 8.103%（NRTL）,6.085%（Apelblat）,7.751%（λh）.Results indicated that Apelblat equation gave the best fitting results,van’t Hoff equation did not apply to this system.The super solubility of iodine aniline solution at the cooling rate of 0.2K/10min was also studied.The equilibrium between o-iodoaniline and p-iodoaniline in the same solvent was compared.The freezing point of two component mixtures of o-iodoaniline and p-iodoaniline was measured by step cooling curve method,the solid-liquid equilibrium phase diagram of o-iodoaniline and p-iodoaniline was obtained,and the experimental data were correlated by the ideal solid-liquid equilibrium model.The results show that the solid-liquid equilibrium phase diagram of this system was a simple eutectic phase diagram of solid-liquid,the eutectic temperature was 298.56K,and the mole fraction of o-iodoaniline was 0.4976 at this point.The average relative deviation between the calculated values of the ideal solution model and the experimental values was 0.17%,the maximum relative deviation was 0.58%.So this system meets the ideal solid-liquid equilibrium model.The fusion enthalpy of o-iodoaniline was1.9761kJ/mol by calculating the model,and the fusion enthalpy of p-iodoaniline was1.5795kJ/mol.In this experiment,KIO₃ is used to catalyze iodine and aniline to synthesize o-iodoaniline.The optimum reaction conditions for 70 mL of methanol and 60 mL of water mixture 1.8626g aniline,2.115g I₂,0.6g KIO₃ and 2.0 mL of concentrated HCl at 318.15K,separation and crystallization product 2.3454g,the yield is 53.55%.The quality fraction of o-iodoidine was 10.68%.The catalyst in this experiment was cheap and mild,and it reached the yield in the synthetic literature of o-iodoaniline.The crude o-iodaniline was purified by melt crystallization.First,the crude o-iodaniline was concentrated to 70.95%and then melte crystallization.Effects of the cooling rate,final temperature in the crystallization process,crystal growing time,heating rate and final temperature in the sweating process on the yield and purity of the product were investigated and analyzed.The results show that when the cooling rate is 0.3K/5min,the final crystallization temperature is 301.15K,crystal growing time is 2h and the heating rate of sweating is 0.2K/5min,the final sweating temperature is 313.15K,99.07%o-iodaniline can be obtained by melt crystallization and the yield is 61.75%.