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Measurement and Correlation of the Solubility of Tetramethylpyrazine in Nine Monosolvents and Two Binary Solvent Systems
journal contribution
posted on 2019-02-12, 14:51 authored by Nuoyang Zhang, Si Li, Haiyan Yang, Mengya Li, Yang Yang, Weiwei TangThe
solubility of tetramethylpyrazine (TMP) in nine monosolvents
(methanol, ethanol, n-propanol, isopropanol, n-butanol, acetone, acetonitrile, methyl acetate, and ethyl
acetate) and two binary solvent mixtures of (methanol + acetonitrile)
and (n-butanol + acetonitrile) was determined by
a static method using UV–vis spectroscopy at temperatures ranging
from 273.15 to 313.15 K. Expectedly, the solubility displays monotonously
rising temperature dependence, and the most remarkable change was
found in acetonitrile. In binary solvent mixtures, TMP solubility
bears a maximum value at 0.8 mole fraction of alcohols independent
of both temperature and solvent nature. The statistical correlations
were well performed by the λh equation, Apelblat
equation, and NRTL model, and the NRTL model achieves the best fitting
results. The mixing enthalpy, entropy, and Gibbs free energy were
derived on the basis of thermodynamic relations and the NRTL model.
The results suggest a spontaneous and entropy-driven mixing process
of TMP in studied solvent systems. The solubility data, correlated
models, and derived thermodynamic functions provide thermodynamic
fundamentals for the separation and purification of TMP crystallization
in industrial production.