METHOD AND APPARATUS FOR CONTINUOUS PURIFICATION OF PARACETAMOL BY RECRYSTALLISATION Russian patent published in 2025 - IPC C07C231/24 C07C233/25 B01D9/02 

FIELD: chemistry.

SUBSTANCE: present invention relates to chemical engineering, particularly to a novel method for continuous purification of paracetamol by recrystallisation, as well as to an apparatus for realizing said method. Method for continuous purification of paracetamol by recrystallisation is implemented in several main successive steps: preparing a saturated solution of contaminated paracetamol; purification from insoluble impurities of saturated solution of contaminated paracetamol; cooling the saturated solution of purified paracetamol and creating crystal nuclei; growing crystals in a suspended layer and separating crystals of a given size. Disclosed method is based on using several circulation loops, which enable to simultaneously carry out several process operations in continuous mode without detriment to quality for each of the steps. Furthermore, use of the nucleation step in circulation conditions through an ultrasonic disintegrator enables accurate control of the required size and type of the obtained crystals depending on the given end characteristics of the product. Method enables to carry out recrystallisation of paracetamol in a continuous mode without the need for external inoculum for crystallisation of the product to obtain purified paracetamol of high purity (not less than 99.9 %) and homogeneity on the polymorphic shape of the crystals, and also enables to control a given particle size distribution, having a narrow distribution of crystals by size.

EFFECT: unit provides trouble-free loading of solid contaminated paracetamol eliminating lumping and sticking of paracetamol powder as a result of solvent vapours penetration.

18 cl, 5 dwg, 2 ex