(610c) Crystallization Process Development of Large Size TMP Crystals

2,2,6,6-Tetramethyl-4-piperidinol (TMP) crystal is a very important intermediate in organic synthesis. To obtain an improved crystallization yield and desirable crystal-size characteristics, several commonly used organic solvents were investigated to determine the solubility of TMP using a gravimetric method. An ethanol solvent and a cooling crystallization method were chosen to obtain an improved theoretical yield. The cooling crystallization process of TMP in the ethanol solution was further optimized to crystallize larger crystals with a narrow crystal-size distribution using an orthogonal array design. Comprehensive analysis showed that water content in ethanol and seed loading are respectively the main influence factors of the average diameter and the diameter span. Final TMP crystals with an average diameter of 1110 μm and a diameter span of 0.715 were obtained under laboratory conditions using the optimized process.