PREDICTIONS WITH UNIFAC OF LIQUID SOLID-PHASE DIAGRAMS - APPLICATION TO WATER SUCROSE GLUCOSE, WATER SUCROSE FRUCTOSE AND WATER XYLOSE MANNOSE

The objective of this study is to develop a prediction model of solid-liquid equilibria based on the UNIFAC method which is applicable to sugar systems. Three new groups, X, F and G, representing respectively the cyclic structure of D-xylose, D-fructose and D-glucose are introduced and new interaction parameters for these groups are calculated. The use of groups X, F and G permits the identification of mannose as composed of X, OH and CH2 and of sucrose as composed of G, F and -O-. The model is tested on three ternary systems: water-sucrose-D-glucose; water-sucrose-D-fructose; water-D-xylose-D-mannose. The results compare favourably with the experimental data except in the invariant point region, corresponding to saturation with both solutes. A similar technique could be applied in the prediction of the behaviour of other sugar systems containing these basic rings.