The separation of glucose and fructose by liquid‐liquid extraction

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Abstract
Some organic solvents, miscible with water, become partially miscible in the presence of either glucose or fructose, and the partition ratios of these sugars between the resulting phases then differ. This difference is considered as the basis for a separation of the glucose and fructose of invert sugar. An examination of binodal curves and tie‐lines of the two systems: solvent‐water‐glucose and solvent‐water‐fructose has been made in respect of eleven organic solvents. Among these n‐propanol and t‐butanol were found the most suitable for the separation of glucose and fructose. The concentrations of sugars in their solvent‐rich phases are much greater with these two solvents than in the corresponding phases of the best solvents partially miscible with water in absence of sugars. The quantities of the two alcohols needed to process a given weight of sugars are, correspondingly, very much smaller. About 40 theoretical stages would be needed to produce glucose and fructose of 90% purity.In the one liquid‐liquid extraction column used, fractionation of glucose and fructose was small, possibly because of the low rates of diffusion of the sugars, or because of column characteristics.Glucose was the more effective sugar in making the solvent and water partially miscible, except with aqueous 2,6‐dimethylpyridine, when fructose was more effective.An improved method of preparation of 2‐methyl‐1,4‐dioxan, one of the solvents examined in more detail, is described.

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