不同质量分数乙醇、乙酸钠溶液对双乙酸钠结晶过程影响

Study on the crystallization property of sodium diacetate in different mass fractions of ethanol and sodium acetate solutions

为提高双乙酸钠（ SDA）的产品质量，考察了温度、溶剂组成、乙酸钠含量等条件对SDA溶解性的影响，采用动态法测定了SDA在不同质量分数乙醇-水、乙酸钠-水混合溶剂中的溶解度，并测定了SDA在纯水和质量分数为0.7996（w1＝0.7996）的乙醇溶液中的介稳区。结果表明，SDA易溶于水，微溶于乙醇，随乙醇质量分数增加，SDA溶解度降低愈加显著，且在w1＝0.7996的乙醇溶液中降低最为明显；随产物中乙酸钠含量增加，SDA溶解度逐渐减小，且在质量分数为0.0832乙酸钠溶液中降低幅度最大；在300~315 K范围内，w1＝0.7996的乙醇溶液对SDA和乙酸钠有明显的分离效果；SDA的介稳区宽度在纯水中随温度升高逐渐变窄，而在w1＝0.7996的乙醇溶液中受温度影响变化小，且介稳区宽度较纯水中窄。因此，在SDA结晶中，可采用w1＝0.7996的乙醇溶液结晶分离SDA，且过饱和浓度需控制在介稳区内。

In order to imProve the quality of SDA,the effect of temPerature,solvent comPosition and NaAc content on the solubility of SDA in water were exPlored,the solubilities of SDA in ethanol and NaAc solu-tions were determined by dynamic method. In addition,the metastable zone of SDA in water and ethanol solution（w1 =0. 799 6）were obtained. The results showed that SDA was soluble in water,while slightly soluble in ethanol,and with the increase of ethanol in solvent mixtures,the solubilities decreased obvious-ly,esPecially the mass fraction of ethanol was 0. 799 6. Also,the solubilities of SDA decreased with the in-crease of NaAc in solvent mixtures,esPecially the mass fraction of NaAc was 0. 083 2. What’s more,etha-nol solution（w1 =0. 799 6）had Played an active role for the seParation of SDA and sodium acetate in the range of 300~315 K. The metastable zone of SDA in water gradually narrowed with the increase of tem-Perature,while in ethanol solution（w1 =0. 799 6）was little influenced by temPerature changes and was narrower. Therefore,ethanol solution（w1 =0. 799 6）can be used as mixed solvent for crystallization and seParation of SDA,and the suPersaturated concentration should be controlled in the metastable zone.