Solubility of fructose and sucrose in mixtures of methanol and water: Experiment and application of equations of state and activity coefficient model

Beyond biochemical functions, carbohydrates have great industrial and economic importance. To improve industrial processes and to develop new applications for these substances, the knowledge of their solubility behavior in different solutions is often necessary. Therefore, the purpose of this work was to collect experimental data on the solubility of fructose and sucrose in hydroalcoholic solutions of methanol and water, using a chromatographic method. The solubility was evaluated for the entire mole fractions of the binary mixture covering the temperatures from 298.15 K to 323.15 K. The results indicated that the chromatographic method is suitable for determining sugar concentration, but it implies an increased uncertainty over the results. The solubility of both sugars was low in methanol-rich binary mixtures, rising with the increasing proportion of water. Greater dependence of the solubility as a function of the composition of the binary mixture was observed for sucrose, indicating stronger molecular interaction and therefore greater deviation from ideality. The NRTL activity coefficient model and the PC-SAFT and CPA equations of state were successfully employed to correlate the solid-liquid equilibrium. The binary interaction parameters were optimized as a function of temperature. The NRTL model has shown greater deviations than those presented by the equations of state. Meanwhile, the equations of state have presented a similar performance.