Patent ID: 6376709
Filing Date: 2002-04-23
Classification: C07C

Abstract:
A process for the crystallization of dicarboxylic acids comprising recrystallizing a solution of crude dicarboxylic acid in a crystallizer in the presence of at least one additive selected from the group consisting of surfactants, buffer salts, acid salts or a mixture thereof, wherein the crystallizer comprises a series of cylindrical impellers, a crystallizer wall and a rotatable impeller shaft, wherein an annular space is formed between the impellers and crystallizer wall, said crystallization being effected while rotating the cylindrical impellers in a unidirectional flow with the solution of crude dicarboxylic acid that creates a velocity gradient which forms, upon cooling, crystals of dicarboxylic acids in the annular space at 10Â° C. to 80Â° C. that are sheared, elongated and increased in size.