Chapter 19
Semi-Batch Cooling Crystallization of Quizalofop-Ethyl with Polymorphism 1
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AkihiroShiroishi ,IsaoHashiba ,RyoKokubo ,KazuoMiyake ,and Yuji Kawamura 2
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Nissan Chemical Industries, Ltd., 7-1, 3-chome, Kanda-Nishiki-cho, Chiyoda-ku, Tokyo, Japan Department of Chemical Engineering, Hiroshima University, Shitami, Saijo-machi, Higashihiroshima, Japan
Downloaded by PURDUE UNIV on December 4, 2016 | http://pubs.acs.org Publication Date: September 21, 1990 | doi: 10.1021/bk-1990-0438.ch019
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It was found that two different crystal forms, namely a platelike α-form and a hairlike β-form, were obtained by cooling crystallization of quizalofop ethyl dissolved in ethyl alcohol. The solubilities, supersolubility and stabilities of the two crystals were investigated. Two solubility curves for the α -form and the β-form respectively were found to intercept at 284K. A metastable supersaturation zone up to 13-15K at 314K was found. It was confirmed that a little amount of α-form crystals suspended in a saturated solution at temperature above 316K gradual ly changed into β-form crystals. Considering those results, authors developed a semi-batch crystallization process to obtain α-form crystal selectively in which crystallization temperature was lowered enough below 293K. Quizalofop-ethyl (1), (4) which has been developed as an effective herbicide by Nissan Chemical Industries, L t d . i s needed as i t s c r y s t a l l i n e state i n commercial production. But no physical properties, s o l u b i l i t i e s and/or any other information useful for the c r y s t a l l i zation of the compound have not appeared to be a v a i l a b l e . Therefore a few physical properties of quizalofop-ethyl, such as i t s s o l u b i l i t y and i t s s u p e r s o l u b i l i t y i n ethyl a l c o h o l , were studied. Two types of c r y s t a l s with different shapes were obtained by cooling c r y s t a l l i z a t i o n and the s t a b i l i t i e s of the crystals were tested i n saturated solutions at various temperatures. P l a t e l i k e α - f o r m c r y s t a l s e a s i l y separate from the solvent i n commercial operation but h a i r l i k e ß - f o r m c r y s t a l s are troublesome because t h e i r suspension i s extremely viscous. So the main purpose of t h i s work i s to develop a modified c r y s t a l l i z a t i o n process to obtain a-form c r y s t a l s e l e c t i v e l y . 0097-156/90/0438-0261$06.00/0 © 1990 American Chemical Society
Myerson and Toyokura; Crystallization as a Separations Process ACS Symposium Series; American Chemical Society: Washington, DC, 1990.
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CRYSTALLIZATION AS A SEPARATIONS PROCESS
Physical Properties of Qulzalofop-ethyl The chemical structure for quizalofop-ethyl i s shown below.
The
CH:
1^P-0-
