Patent ID: 6359186
Filing Date: 2002-03-19
Classification: C07C

Abstract:
A process for co-production of paraxylene and metaxylene from a hydrocarbon feedstock mixture, said process comprising separating said mixture in a simulated moving bed countercurrently or co-currently in at least one chromatographic column (5) that contains a plurality of adsorbent beds interconnected in a closed loop and that have a selectivity that is different for paraxylene, ethylbenzene, metaxylene and orthoxylene, said column comprising at least five zones delimited by injections of said hydrocarbon feedstock (4) and a desorbent (22) and draw-offs of an intermediate raffinate (17), a raffinate (13) and an extract (6), withdrawing paraxylene from desorption zone 1 located between the injection of the desorbent and the draw-off of the extract; desorbing ethylbenzene, orthoxylene and metaxylene from desorption zone 2 located between the draw-off of the extract and the injection of the feedstock; adsorbing paraxylene in adsorption zone 3A located between the injection of the feedstock and the draw-off of intermediate raffinate; adsorbing ethylbenzene in adsorption zone 3B located between the draw-off of intermediate raffinate and the draw-off of raffinate; zone 4 is between the raffinate draw-off and the injection of desorbent, wherein:the feedstock has an ethylbenzene content that is less than 5% by weight, the chromatographic column comprises at least twenty-five beds, the raffinate is distilled at least once to recover metaxylene with a purity of at least 99.0% and orthoxylene, the extract is distilled at least once to recover paraxylene with a purity of at least 99.60%.