Growth Kinetics of S-Mandelic Acid in Aqueous Solutions in the Presence of R-Mandelic Acid

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• 作者：Lorenzo Codan ; Carl Friedrich Eckstein ; Marco Mazzotti
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：February 6, 2013
• 年：2013
• 卷：13
• 期：2
• 页码：652-663
• 全文大小：792K
• 年卷期：v.13,no.2(February 6, 2013)
• ISSN：1528-7505

文摘

In this work, the effect of R-mandelic acid on the growth kinetics of S-mandelic acid in aqueous solutions is investigated. Isothermal seeded batch experiments are conducted inside the two phase region where crystals of the S-enantiomer are at equilibrium with an enantiomerically enriched liquid phase. Crystal growth of S-mandelic acid is studied at three different temperature levels, i.e., at 15, 20, and 25 掳C, and at three different levels of concentration of the R-enantiomer, i.e., at 0 g/g of water, 0.0231 g/g of water, and 0.0393 g/g of water. A previous study reports a very narrow metastable zone width (MSZW) for secondary nucleation (Perlberg et al. Ind. Eng. Chem. Res.2005, 44, 1012鈥?020). The MSZW for secondary nucleation is however found to be dependent on the suspension density and on particle size (Kubota et al. J. Chem. Eng. Jpn.2002, 35, 1063鈥?071). By decreasing the average particle size and by increasing the mass of seed crystal, the MSZW for secondary nucleation could be increased thus enabling the exploration of a wider range of supersaturations. The concentration profile during the batch experiment is monitored by attenuated total reflection鈥揊ourier transform infrared (ATR-FTIR) spectroscopy, and the growth parameters are estimated by solving a population balance model. R-Mandelic acid is found to substantially lower the growth rate of S-mandelic acid. Using a semiempirical, size-independent growth rate expression, the measured concentration profiles can be satisfactorily described by three parameters, two that are independent of the concentration of R-mandelic acid in solution and one which implicitly describes the change in the growth rate due to presence of R-mandelic acid. Moreover, the presence of the R-enantiomer is also found to have a negative impact on crystal purity.