Method for purifying sucralose

A method for purifying sucralose, sequentially comprising:

• adding sucralose to ultrapure water (UPW) to obtain a mixture, heating the mixture to obtain a dissolved solution, and filtering the dissolved solution to obtain a recrystallization solution;
• extracting the recrystallization solution with an extraction solvent to remove non-polar impurities to obtain an extracted recrystallization solution;
• subjecting the extracted recrystallization solution to concentration by evaporation to obtain a concentrated recrystallization solution with a preset concentration, and leaving the concentrated recrystallization solution to stand at a preset temperature for a preset time to produce a sucralose crystal nucleus in the concentrated recrystallization solution;
• subjecting the concentrated recrystallization solution containing the sucralose crystal nucleus to gradient cooling to obtain a recrystallization solution with a large amount of a sucralose crystal;
• and
• centrifuging the recrystallization solution with a large amount of a sucralose crystal to obtain a solid, and subjecting the solid to water-washing and drying to obtain the sucralose crystal;
• wherein
• the preset concentration is in a range of 60 wt % to 80 wt %;
• the preset temperature is in a range of 50° C. to 60° C.;
• and
• the preset time is in a range of 0.5 h to 3 h;
• and
• the gradient cooling comprises:
• cooling the concentrated recrystallization solution containing the sucralose crystal nucleus from a first temperature of 52° C. to 58° C. to a second temperature of 43° C. to 47° C. at a first cooling rate of 1° C./10 min to 1° C./60 min,
• holding at the second temperature for 0.5 h to 3 h, and
• cooling to a third temperature of 18° C. to 22° C. at a second cooling rate of 1° C./10 min to 1° C./60 min.