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Thermodynamic study on dynamic water and organic vapor sorption on amorphous valnemulin hydrochloride

Jinbo OUYANG, Jingkang WANG, Yongli WANG, Qiuxiang YIN, Hongxun HAO

《化学科学与工程前沿（英文）》 2015年第9卷第1期页码 94-104 doi: 10.1007/s11705-015-1460-3

摘要： The sorption of water and organic vapors on valnemulin hydrochloride was determined by dynamic vapor sorption at 25 °C. The adsorption-desorption behavior of water vapor and a series of organic vapors was investigated to probe the structural changes in valnemulin hydrochloride before and after sorption. The isothermal adsorption equilibrium data was evaluated using Guggenheim-Anderson-deBoer (GAB) and Brunauer-Emmett-Teller (BET) models. The BET model is applicable only at low relative pressures (0.1≤RP≤0.4) while the GAB model is applicable in the whole range of RPs (0.1≤RP≤0.9). The sorption kinetics at high RPs was determined by fitting the sorption data to the Avrami equation and the sorption content time relationship could be predicted by the Avrami equation. Finally, the possible sorption mechanism of valnemulin hydrochloride was also discussed.

关键词： valnemulin hydrochloride water vapor organic vapors sorption kinetics

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The dehydration behavior and non-isothermal dehydration kinetics of donepezil hydrochloride monohydrate

Tiantian LIU, Yuanyuan RAN, Bochao WANG, Weibing DONG, Songgu WU, Junbo GONG

《化学科学与工程前沿（英文）》 2014年第8卷第1期页码 55-63 doi: 10.1007/s11705-013-1352-3

摘要： Powders of donepezil hydrochloride monohydrate (Form I) underwent isomorphic dehydration, losing 3% w/w water between 90% and 10% relative humidity (RH) without changing its powder X-ray pattern. Below 10% RH, additional dehydration occurred in conjunction with a reversible phase transition between the monohydrate state and a dehydrated state, with a 4.0% w/w loss to 0% RH. A combination of methods was used to understand the structural changes occurring during the desolvation process, including dynamic vapor sorption measurements, thermal analysis and powder X-ray diffraction. Form I showed the characteristics of the channel hydrate, whose non-isothermal dehydration behavior proceeds in two steps: (1) the loss of non-crystalline water adsorbed on the surface, and (2) the loss of one crystalline water in the channel. Dehydrated Form I is structurally similar to the monohydrate Form I. According to the heat of fusion and the crystal density criteria, the two crystal forms belonged to the univariant system, and the anhydrate (Form III) is stable. The dehydration kinetics was achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 15 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 were best expressed by the Zhuralev-Lesokin-Tempelman equation, suggesting a three-dimensional diffusion-controlled mechanism.

关键词： dehydration thermal analysis transformation dehydration kinetics