Measurement and Modeling of Phase Equilibria in Systems Containing Water, Xylose, Furfural, and Acetic Acid

Wood hydrolysates obtained in biotechnological processes are typically aqueous solutions that contain, among others, sugars, acetic acid, and furfural. Only little is known on the influence of the sugars on the phase equilibria in those mixtures. Therefore, liquid-liquid equilibria (LLE), solid-liquid equilibria (SLE), and solid-liquid-liquid equilibria (SLLE) in the system (water (W) + xylose (X) + furfural (F)) were studied in the present work at 298.15 and 333.15 K. Additionally, the LLE in the system (W + X + F + acetic acid (AA)) was studied at 298.15 K. The results show that, up to the solubility limit of xylose, adding xylose to mixtures of (W + F) hardly influences the width of the miscibility gap, and that there is practically no xylose in the furfural-rich phase. However, the miscibility gap in the ternary system (W + F + AA) is slightly widened by the addition of xylose. The experimental data on the phase equilibria from the present work were described using the nonrandom two-liquid model. The model describes the experimental data well.