A Study On The Cooling Crystallization Process Of Hydroquinone

Hydroquinone is an important basic organic material and has been extensively used in the fields of pharmaceutics, foodstuff and chemical industry. At present, there are some quality problems in the homemade hydroquinone products, such as poor crystal morphology, small stack-density, too deep color, asymmetry CSD and bad mobility etc. Hence, the crystallization process of hydroquinone was investigated systematically. In detail, the effects of solvents and additives on the crystal habit and the polymorphism phenomenon were experimentally explored.The solubilities of hydroquinone in water, methamol, ethanol, 2-propanol, ethyl acetate, butyl acetate and acetic acid were measured by use of the laser-monitoring dynamic method. The solubility data were correlated with Apelblat model. The metastable zone width was also measured by the laser method and the effects of cooling rate were investigated experimentally. In addition, the induction period of the supersaturation ethanol solution of hydroquinone was measured, through which the intersurface tension between the crystal and the solution was calculated.The effect of solvents on the crystal habit of hydroquinone and the polymorphism phenomenon of hydroquinone were studied by used of SEM, DSC, PXRD, XRD etc. According to the single crystal data, the crystal habit of hydroquinone under the vacuum condition was simulated by Cerius2 software with BFDH and AE models respectively, and the effect of solvents on the crystal habit of hydroquinone was explained in theory.The cooling crystallization kinetics of hydroquinone in ethanol solution was experimentally measured by the batch dynamic method. The effects of the supersaturation, the suspension density, the agitation speed on the nucleation rate and the crystal growth rate were investigated. A size-independent model and the moment transform method were chosen to deal with the experimental data, and the model equations of the nucleation rate and the crystal growth rate in the crystallization process of hydroquinone were finally obtained through the least square multivariate linear regression.Aimed at solving the problems existing in the manufacture process of hydroquinone, efforts were carried out from two aspects, decoloration of the raw crystallization solution and the cooling crystallization technology. In the decoloration...