Method for purifying sucralose-6-acetate

A method for purifying sucralose-6-acetate, comprising:

• preparation:
• providing a saturated solution of crude sucralose-6-acetate in ethyl acetate which is heated to a predetermined temperature;
• gradient crystallization:
• subjecting the saturated solution to multiple cooling crystallization and filtration, and collecting crude sucralose-6-acetate obtained after the multiple cooling crystallization and filtration, wherein during each cooling crystallization process, a low-polarity solvent is added dropwise to the saturated solution to reduce a polarity of the saturated solution during crystallization step by step;
• and
• purification:
• subjecting a resulting collected crude sucralose-6-acetate to recrystallization for purification by using a mixed solution of ethyl acetate and the low-polarity solvent to obtain a purified sucralose-6-acetate;
• wherein in the gradient crystallization, the saturated solution is subjected to the multiple cooling crystallization three times, wherein the multiple cooling crystallization comprises a first cooling crystallization, a second cooling crystallization, and a third cooling crystallization, wherein the first cooling crystallization is conducted at a temperature of 40° C. to 50° C., the second cooling crystallization is conducted at a temperature of 20° C. to 30° C., and the third cooling crystallization is conducted at a temperature of −10° C. to 0° C.