GB809815A - Recovery of sucrose esters - Google Patents

Abstract

Mono-esters of sucrose with saturated aliphatic monocarboxylic acids and di-esters of sucrose with saturated and unsaturated monocarboxylic acids are recovered from crude reaction mixtures containing such esters by removing organic solvent from the reaction mixture, adding water to the residue, adjusting the pH of the aqueous mixture to below pH 7 and separating the sucrose ester from the mixture. The process is preferably applied to mono esters of sucrose with monocarboxylic acids containing at least 16 carbon atoms such as stearic and palmitic acids, and to diesters of sucrose with monocarboxylic acids containing at least 8 carbon atoms. The initial esterifying reaction is effected in an organic solvent of relatively high boiling point such as dimethylformamide. In the recovery process the solvent is removed, for example by distillation under reduced pressure. Water is then added and temperature of the mixture is desirably adjusted to below 20 DEG C., preferably to the range 0 DEG to 5 DEG C. The pH is adjusted by adding an acidic substance such as sulphuric acid, acetic acid, sulphur dioxide, carbon dioxide or an acidic ion exchange resin, preferably to pH 3-4. The sucrose ester is thereby precipitated and may be separated from the mixture, for example, by filtration or centrifuging. In examples: (1) sucrose is reacted with methyl stearate in dimethylformamide in the presence of potassium carbonate to produce sucrose monostearate, methyl alcohol and dimethylformamide are removed by distillation, the dried residue is stirred into water, sulphuric acid is added to reduce the pH to below 7 and the sucrose ester is filtered off; (2) sucrose monostearate produced as in (1) after removal of dimethyl formamide is stirred into water and sulphur dioxide is passed through the solution at between 0 DEG and 5 DEG C. to give a pH below 7; the sucrose ester precipitated is centrifuged off and resuspended in water and recentrifuged; (3) sucrose, ethyl oleate and potassium carbonate are heated together for 6 hours in dimethylformamide at 100 DEG C. and 80-100 mm. Hg. to produce sucrose dioleate, the solvent is distilled off, water is added and the slurry warmed and stirred; on cooling to 15 DEG C. and passing in sulphur dioxide to give a pH of 4 to 5 the diester is coagulated and filtered.