Research On The Crystallization Process Of Vanillin

Vanillin is the first flavor synthesized by human, it is one of the most importantraw material in the food additive industry, which is also widely used in the chemicalindustry and pharmaceutical industry. Crystallization is the common method used inindustrial production to purify the final product, however, compared to the productionabroad, our home-produced vanillin production technology is relatively backward. So,aiming at solving the problems existed in the manufacturing process of vanillin in ourcountry, such as low yield, poor color, low purity, low bulk density, uneven CSD, andpoor crystal habit, this paper carried out a deeply and systematic research on thecrystallization process of vanillin.Firstly, this paper determined the powder X-ray diffraction patterns of vanillin,and the single crystal data was obtained based on the single crystal cultivated by theauthor. Then, with the help of BFDH model and AE model, the crystal habit ofvanillin was simulated. Meanwhile, some approaches, such as PXRD, DSC andpolarizing microscope, were applied to characterize the two polymorphs existed in thecooling crystallization process.Then, the thermodynamic properties of vanillin were studied."static method"was applied to determine the solubility of vanillin in pure solvent, such as methanol,water and n-propanol, and in mixed solvent with different proportions such asmethanol-water and n-propanol-water. Then, the Apelblet simplified empiricalequations and the λ h equation were used to fit the solubility data. At the same time,with the help of FBRM, ATR-FTIR, PVM and polarizing microscope, the authorstudied the liquid-liquid phase separation of vanillin in n-propanol-water systemduring the cooling crystallization process, and some effective methods were adoptedto eliminate or inhibit this phenomenon.Using the laser light scattering method, the supersolubility of vanillin inmethanol-water system was measured at different temperatures, and the metastablezone in this solvent were drawn, and the influence of initial concentration, coolingrate as well as stirring rate on the metastable zone width were also discussed. Then,by determining the induction time of vanillin in methanol-water system, the surface tension of vanillin in this solvent was calculated, and, the nucleation kineticsparameters of vanillin at experimental conditions were confirmed at alst.On the basis of thermodynamic and kinetic studies, cooling crystallizationprocess of vanillin was conducted. The influence of various operating conditions,such as solvent, seeding, cooling pattern, initial concentration and stirring rate, on thecooling crystallization process was investigated comprehensively. Ultimately, theoptimum operating conditions of vanillin during cooling crystallization process wereestablished, according to this process, ideal product with prefert habit and CSD, noagglomeration, high yield and purity was obtained at last.