长链二元酸的水相反应结晶过程研究

Aqueous Phase Reaction Crystallization Process of Long-Chain Dicarboxylic Acids

针对目前由生物发酵法制备、水相结晶法提纯的长链二元酸产品晶形差、晶体粒度差、易于团聚等问题,本文以十二碳二元酸为研究模型,采用静态法测定了十二碳二元酸在水中的溶解度,并通过实验探究了原料流加方式、温度、pH值、搅拌速率等因素对水相结晶产品的影响.结果表明:十二碳二元酸在水中的溶解度极小,水相反应结晶过程中,极易导致反应体系局部产物过饱和度过高,从而爆发成核,晶体聚结,包藏杂质,进而影响产品质量;而选用双向流加反应原料的方式可以有效控制局部产物过饱和度,从而提高产品质量,由此开发出了一套完整可行的长链二元酸水相反应结晶工艺.

Long-chain dicarboxylic acids are basically prepared by biological fermentation method and purified via crystallization from aqueous solution. However, long-chain dicarboxylic acids obtained from these methods have many drawbacks, such as poor crystal shape and crystal size distribution （CSD）, heavily agglomerated character and so on. In this paper, dodecanedioic acid （DDDA） is used as the research model. To improve the DDDA product prop- erties, we determined the solubility of DDDA in water using a static analysis method and optimized the crystalliza- tion process via separately investigating the effects of adding rates and temperature of raw materials, pH, stirring rate and other factors on the final DDDA products. The results show that the solubility of DDDA in water is very poor, which may easily lead to high local supersaturation during crystallization process and consequently result in burst of nucleation, crystal agglomeration, and impurity inclusion in the product. Hence, a method of dual-addition of reacting materials was designed based on the above results. It is proven that this addition strategy can control the local product supersaturation and improve quality of products effectively. Furthermore, a complete and feasible aqueous phase reaction crystallization technology of long-chain dicarboxylic acids was developed.