Abstract: The present invention pertains to a process for the purification of an organic product by fractionated crystallization, characterized in that the organic product is purified by circulation in filled tubes by varying the circulation rate at each purification and concentration stage. The invention also pertains to an apparatus for the purification of an organic product by fractionated crystallization designed for the implementation of said process.

Abstract: The invention concerns a process for purifying naphthalene. The process comprises selective hydrotreatment corresponding to hydrodesulphuration and/or hydrodenitrogenation and/or hydrodehydroxylation and/or hydrogenation of olefins while limiting naphthalene hydrogenation. The catalyst used comprises a matrix, at least one group VIII metal, at least one group VI metal and optionally phosphorous. It has a specific surface area of at most 220 m2/g, a pore volume of 0.35-0.7 ml/g and an average pore diameter of over 10 nm. The process is carried out at 150-325° C. at a pressure of 0.1-0.9 MPa, with an HSV of 0.05-10 h−1, and a H2/naphthalene ratio of 0.1-1.3 mole/mole. The effluent, freed of H2S, NH3 and water, undergoes a naphthalene separation process by distillation or, as is preferable, by crystallisation. Further, recycling the separated tetralin to the hydrotreatment step can substantially increase the naphthalene yield.