Preparation and Dehydration Kinetics of Complex Sulfadiazine Calcium Hydrate with Both Channel-Type and Coordinated Water

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• 作者：Jia Sun ; Chuang Xie ; Xia Zhang ; Ying Bao ; Baohong Hou ; Zhao Wang ; Junbo Gong ; Hongxun Hao ; Yongli Wang ; Jingkang Wang ; Qiuxiang Yin
• 刊名：Organic Process Research & Development
• 出版年：2016
• 出版时间：April 15, 2016
• 年：2016
• 卷：20
• 期：4
• 页码：780-785
• 全文大小：420K
• 年卷期：0
• ISSN：1520-586X

文摘

A new hydrate of sulfadiazine calcium (Hydrate I) was discovered, and the crystal structure was determined using single crystal X-ray diffraction. Both channel-type water (9.23 wt %) and calcium-ion coordinated water (11.87 wt %) existed in the unit cell. The thermal stability and dehydration of Hydrate I were investigated by thermal gravimetric analysis, hot stage microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. A two-step dehydration process was detected from Hydrate I to anhydrous phase (AP) with the intermediate of the less-hydrated form (Hydrate II). The dehydration kinetics of Hydrate I with both channel-type and coordinated water was studied using model fitting method and model free method in isothermal mode. The dehydration activation energy was derived via the Friedman method. Further, the first-step dehydration of Hydrate I was determined to be the 2D phase boundary reaction mechanism, and the second-step dehydration was found to be 3D phase boundary reaction mechanism via model fitting approach.