脱氢乙酸合成条件的优化及提纯方法的改进
作者：李星
院校:南京工业大学
关键字:食品防腐剂;脱氢乙酸;合成;提纯;非水滴定
学位：硕士
专业:应用化学
摘要:
脱氢乙酸是一种新型的食品添加剂,它具有广谱﹑抑制酵母菌强﹑相对稳定性高﹑安全性高等优点,广泛用于食品加工行业中。 本文通过对两种方法进行脱氢乙酸的合成,对反应时间,反应温度,催化剂及反应时间等条件对产率的影响,得出最佳的反应条件。得出在以乙酰乙酸乙酯为原料的情况下,最佳条件是催化剂选用NaHCO3+Na2CO3(重量比1:1),反应温度为200℃,反应时间为6h,得到的收率为43.1%。在以双乙烯酮为原料的情况下,最佳反应条件是催化剂选用三乙烯二胺,反应温度为40℃,反应时间为80min,得到的收率为83.6%。 现在的工业生产一般用减压蒸馏的方法对产物进行提纯,但是由于脱氢醋酸的凝固点较高,在生产中容易堵塞管道,为了克服这一个缺点,有的采用有机溶剂重结晶的方法来提纯,但有机溶剂重结晶得出的产品纯度不高,且给产品引入有机溶剂杂质。本文根据脱氢乙酸的性质,通过用水溶液重结晶和水蒸气汽提的方法进行产品的提纯,不存在堵塞管道和引入有机溶剂杂质的问题,且设备简单,易连续生产,得出的产品纯度较高,纯度能达到99%以上。 对产品进行结构分析,所合成的产物通过元素分析,红外光谱,1H NMR的分析,表征分子结构,结果显示合成的产物为脱氢乙酸。 对脱氢乙酸钠的分析,传统的脱氢乙酸钠分析方法是让它转化为脱氢乙酸后用紫外分光光度法和色谱法进行分析,由于这些方法所需的设备昂贵,操作复杂,而且其只能用于食品中微量脱氢乙酸钠的分析,对于脱氢乙酸钠的常量分析还未见报道。本文根据脱氢乙酸钠的特点找出用P—萘酚苯作为指示剂,用高氯酸进行非水滴定的简便方法,该方法可用于脱氢乙酸钠工业生产中的质量控制。 在对脱氢乙酸的防腐性能的测试中,也显示了它有具有很好的防腐效果。
Abstract:
Dehydroacetic acid is a new type of food antiseptic, which has broad- spectrum、strong antibiotic action、 high stability and security. It was used in food industry extensively. The DHA was synthesized with the catalyst by two methods in this paper. The influences of reaction time, reaction temperature and the amount of catalyst have been studied. The optimized reaction conditions were obtained. When the raw material is acetoacetic ester, the optimized reaction temperature is 200℃,the optimized reaction time is 6hr, the optimized catalyst is NaHCO3+Na2CO3, and the yield is 43.1%. When the raw material is diketene, the optimized catalyst is triethlenediamine, the optimized reaction temperature is 40℃, the optimized reaction time is 80 min, and the yield is 83.6%. The traditional purification in industry is reduced pressure distillation. Because of its low melting point, the product often jam the line of pipes, so some people purify the product by recrystallization. The recrystallization also has defaults; the product has lower purity, so it is difficult in food. In this paper, we purify the product by using hot water extration and water vapor distilation.The product gained is high purity, its purity is above 99%, and the method is simple. The product has been analyzed by IR, 1HNMR, etc, and the result reviews the product is dehydroacetic acid. Ultraviolet spectrophotometric method and chromatography are often used in the analysis of dehydroacetic sodium. But those methods need exorbitant equipment, operation is difficult, and it only has been used in microanalysis. The method of commercial product’s analysis is not reported. In this paper, we found a method of commercial product’s analysis by using nonaqueous titration. In this method, the p- naphtholbenzene is used as indicator. This method can be used as quality control in industry. In the test of dehydroacetic acid’s performance, it reveals excellent antiseptic capability.