Thermodynamic models for determination of solid–liquid equilibrium of the 6-benzyladenine in pure and binary organic solvents
Introduction
6-Benzyladenine (Fig. 1., C12H11N5, FW 225.25, CASRN: 1214-39-7), a white crystal powder, is a kind of cytokinin which can be produced by synthetic means for the first time. 6-Benzyladenine is widely used to promote plant growth in agriculture. It exerts a positive effect in promoting the cell growth of plant, inhibiting the plant chlorophyll degradation and increasing the content of amino acids [1], [2].
For most solid products, solution crystallization is the one of the most commonly employed operations for their recovery and purification, where the accurate quantity information of the solute solubility on solvents and temperature is essential. With the detailed solubility values, optimal crystallizer configurations and operation conditions together with the selection of the solvent for a specific solute can be achieved [3]. The solubility of the different organic solvents plays an important role in understanding the phase equilibria or solid–liquid equilibria in the research for crystallization or the liquid–liquid equilibria in the extraction process. Purity is an important part of a medicinal substance. This work aims to provide some useful data for industrial production of the 6-benzyladenine chemistry. We want to research the thermodynamic property of 6-benzyladenine. Further, we can explore more about separation processes such as the safety of operating and extractive crystallization.
In this study, the solubility of 6-benzyladenine in pure and mixture organic solvents was measured within the temperature range from 278.15 K to 333.15 K under 0.1 MPa by the gravimetric method. The solubility results were correlated using the modified Apelblat model, the Buchowski-Ksiazaczak λh model, the ideal model or the combined nearly ideal binary solvent/Redich-Kister (CNIBS/R-K)model, Jouyban-Acree model and Ma model. We expected to determine the best pure or mixed solvents in a crystallization process of 6-benzyladenine from the selected solvents according to experimental values. Besides, the analysis of thermodynamic properties would also help to determine the best temperature interval, which provides information on the solubility at different temperatures [4].
Section snippets
Materials and apparatus
6-Benzyladenine with a mass faction purity ⩾0.990 (which the mass faction for water ⩽0.005) was obtained from Aladdin Industrial Corporation. Its purity was measured by high performance liquid chromatography (HPLC type DIONEX P680 DIONEX Technologies). It was dried and the water content was less than 0.001. We measured the melting point by the melting point apparatus (HCRD-2C), which is from Chengdu Huacheng Instruments Co., Ltd. Other chemical reagents were used without further purification.
Solubility results and correlation models
The saturated mole fraction solubility (x) of 6-benzyladenine in methanol, ethanol, 1-butanol, acetone, acetonitrile, ethyl acetate, dimethyl formamide and tetrahydrofuran over the temperature range of (278.15–333.15) K is recorded in Table 2 and shown in Fig. 2.
The relative deviation (RD) and the relative average deviation (RAD) were estimated by comparing the models to the experimental values. Low values for the RD and RAD would suggest that a model agrees favourably with the experimental
Conclusions
1. The solubility of 6-benzyladenine in pure and mixture solvents increases with rising temperature, but the increment is different in different solvents. In binary solvent mixtures, the solubility increases with the rise of the ratio of dimethyl formamide. Dimethyl formamide can be considered as an effective solvent in the crystallization process and acetone could be used as an effective anti-solvent; (2) the solubility values can be successfully correlated using three equations (the ideal
Acknowledgements
This research work was financially supported by National key Research & Development (R&D) plan (2016YFD0201000), National Natural Science Foundation of China (31471692).
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Both authors are equally contributed to this work.