Aspect Ratio Modulation of Sucralose through {002}/{011} Preferred Orientation in Antisolvent Crystallization

The aspect ratio modulation in the alcoholysis process is highly significant for the production of high-quality sucralose. In this work, antisolvent crystallization (ASC) accompanied by preferred orientation was first adopted in the sucralose separation, based on which simultaneous modulations on aspect ratio, solubility, and stability have been realized. In detail, after the alcoholysis process in methanol, four antisolvents bearing different functional groups were used in ASC, i.e., isopentanol (IPN), isovaleraldehyde (IVD), isovaleric acid (IVA), and isobutyl propionate (IBP). To our interest, when IVA was used as the antisolvent, the highest separation efficiency (49.33%), fastest crystallizing rate (5.64%/h), lowest aspect ratio (1.55), and solubility (9.28 wt %) and good thermal stability (131.65 °C) of sucralose were achieved. Single crystal structures of sucralose using different antisolvents have been determined. Sucralose using IVA as the antisolvent exhibits the greatest molecular distortion and strongest intermolecular C-H···Cl hydrogen bonds; thus, the preferred growth along {002}/{011} directions has occurred and accounted for its lower aspect ratio, worse solubility, and better stability. The strongest methanol···IVA interactions due to the presence of a carboxyl group can accelerate the formation of the emulsion, resulting in the fastest crystallizing rate. The antisolvent screening and the discovery about relative mechanisms will provide a theoretical guide for the production of high-quality sucralose.