Solid-Liquid Equilibrium of Xylose in Water and Ethanol/Water Mixture

Abstract

This work deals with the study of thermodynamical models for the solid-liquid equilibrium (SLE) and comparing its performance with experimental data. The xylose solubility in the xylose-water and xylose-water-ethanol systems has been measured using a variant of the isothermal method. A total of 12 experiments were performed in a 100 mL glass jacketed crystallizer with helix-type agitator by changing the temperature from 0 to 60°C. The solution was mixed during 72 h with an IKA Labortechnic, RW 20.n agitator at 450 rpm. Later, the experimental and reported results were fitted using the prediction models based on the vapor-liquid-equilibrium (UNIFAC (Universal Functional Activity Coefficient), ASOG (Analytical Solutions of Groups) and GSP (Group Solubility Parameter); semi-empirical models based on the vapor-liquid-equilibrium (VLE) (UNIQUAC (Universal Quasi Chemical), Wilson and NRTL (Non Randon Two Liquid)) on the solid-liquid-equilibrium, and empirical model with fitted parameters (Nývlt, λh, Margules with 1 and 2 parameters). The results showed that the UNIQUAC model with fitted parameters can describe the SLE with reasonable accuracy (1.28 and 3.36% for binary and ternary systems, respectively). The average deviation was the arithmetic mean of the deviations. On the other hand, the other methods resulted in poor agreement with the system’s behavior presenting systematic deviations from the experimental data.