| 摘要 |
A crystallisation process for the purification of para-xylene from a feedstock of C8 aromatic hydrocarbons, comprises: (a) Passing the feedstock, contg. 65-90% of para-xylene, to a prim. crystallisation stage operating at -15 to 5 deg C. producing a prim. suspension which is separated to give prim. stage crystals and a prim. mother liquor; (b) re-cycling part of the mother liquor to the prim. crystallisation stage and the sec. part to a sec. crystallisation stage operating at -15 to -35 deg C, to produce a sec. stage suspension which is separated to give sec. stage crystals and a sec. mother liquor; (c) re-cycling a prim. part of the sec. liquor to the sec. crystallisation stage and passing of the sec. stage crystals to the prim. crystallisation stage; (d) passing the prim. stage crystals into a suspension drum, operating at 0-10 deg C, to form a slurry, at a third stage; (e) passing the third stage suspension into a final prod. separator, to give purified para-xylene crystals of 99.5% purity or more and a separated liq.; and (f) separating the purified crystals from the separator liq. and re-cycling the liq. to the first crystallisation stage and to the suspension drum while recovering the purified prod.. Also claimed are similar methods to purify para-xylene with variations in steps (a)-(f) or including further steps and where para-xylene percentages and processing temps. are slightly different.
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