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    Para xylene separation process
    2.
    发明授权
    Para xylene separation process 失效
    对二甲苯分离过程

    公开(公告)号：US2672487A

    公开(公告)日：1954-03-16

    申请号：US9605849

    申请日：1949-05-28

    Applicant: STANDARD OIL DEV CO

    Inventor： TEGGE BRUCE R ,  CARLSON CARL S ,  JOSEPH STEWART

    IPC: B01D9/00 ,  C07C7/14

    CPC classification number: B01D9/0013 ,  B01D9/0059 ,  C07C7/14 ,  C07C15/08

    Abstract: Para-xylene is separated from a hydrocarbon mixture, e.g. of xylenes and ethylbenzene, by crystallizing para-xylene from the mixture by contact with cold walls in a scraped surface chilling zone at a temperature between -40 DEG C and -90 DEG C, removing the para-xylene crystals from the cold walls by slow scraping, e.g. 5-20, preferably 5-10, scrapes per minute, holding the crystals in an agitated remaining portion of the liquid mixture for further growth, and separating the grown crystals from the resultant mother liquor. The crystals may be washed with a substantially immiscible solvent. As described the liquid feed, e.g. an aromatic hydrocarbon fraction boiling in the range 130-160 DEG C, is pumped through heat exchanger 2 to a scraped surface chiller 4 cooled to about -60 DEG C, the temperature depending on the composition of the feed. Slurry from chiller 4 flows to a refrigerated holding tank 6 with agitator 3 for crystal growth, the final crystals and mother liquor being discharged continuously or intermittently by line 7 to separator 8, Fig. 2, which may be a centrifuge, filter press &c. Alternatively part only of the feed may pass through chiller 4, the remainder being supercooled at 41 and 42 and passed direct to holding tank 6. In another arrangement the tank 6 is dispensed with and chiller 4 used as a holding tank. The crystals are preferably allowed to grow for at least 30 minutes. Filtrate from separator 8 passes along line 33 and heat exchanger 2 to storage. The filter cake is washed with water and a polar oxygen-containing organic compound e.g. methanol, acetone, dioxane, from line 9, the spent wash going to settler 11 and the filter cake to melter 24. The melted para-xylene is scrubbed with water from line 27 in mixer 26 to remove wash liquid which is retained in the aqueous layer in settler 28 from which para-xylene goes to storage and the aqueous layer to stripping tower 20 to recover the organic component part of which returns to the tower as reflux and the remainder as make-up to line 9. From settler 11 wash liquid (the upper phase) is returned to line 9 and the hydrocarbon phase, after scrubbing with water in mixer 14, flows to settler 16 from which the hydrocarbon phase is returned by line 17 to the feed line 1 and the aqueous phase to stripping tower 20. The use of miscible hydrocarbon wash liquids is also referred to. U.S.A. Specification 1,940,065 is referred to.

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