Patent ID: 8536326

Claim:
A method for preparing sucralose comprising: adding a chlorinating agent or a chlorinating agent solution dropwise to a mixed solvent composing of a fixed amount of DMF (N,N-dimethylformamide) and an impurities removing agent to obtain a first composition; heating the first composition up to a temperature ranging from 40 to 80° C. for reaction for a period ranging from 1 to 5 hours; evaporating the impurities removing agent from the first composition by reducing pressure of the first composition, thereby obtaining a pure Vilsmeier chlorinating reagent; adding DMF and composite catalyst to the pure Vilsmeier chlorinating reagent to obtain a second composition and cooling the second composition down to 0° C.; adding sucrose-6-acetic ester DMF solution dropwise to the second composition; heating the second composition up gradually to a temperature ranging from 105 to 115° C. and maintaining the temperature for a period ranging from 2 to 3 hours; cooling the second composition down to room temperature and neutralize the second composition with alkali to obtain a neutralized composition and extract the neutralized composition with an extracting agent; removing the extracting agent by vacuum removal to obtain a third composition; adding water to dissolve the third composition to obtain a fourth composition; cooling the fourth composition down for crystallization and thereby obtaining a crude product of sucralose-6-acetic ester; recrystallizing the crude product with water and ethyl acetate to obtain white sucralose-6-acetic ester crystals; dissolving the crystals with methanol to obtain a methanol solution; adding potassium hydroxide to the methanol solution until pH value reaches a range of 9 to 11 to obtain a fifth composition; leaving the fifth composition for reaction for a period ranging from 3 to 5 hours neutralizing the fifth composition with diluted acetic acid, hydrochloric acid and so forth; removing the solvent from the fifth composition by reducing pressure of the fifth composition to obtain a sixth composition; adding water to the sixth composition for dissolution; adding less polar extracting solvent to the sixth composition to extract less polar impurities; after a majority of solvent is removed by reducing aqueous phase pressure, reducing temperature for crystallization and thereby obtaining an end product having a content of more than 99% sucralose.