| 摘要 |
An improved process for separating ethylbenzene at high purity and at high recovery from a feed stream comprising ethylbenzene and paraxylene which process employs an adsorbent comprising type X or type Y zeolite containing calcium at the exchangeable cationic sites. The process in one embodiment employs a countercurrent-flow fixed-bed flow system and includes the steps of maintaining at least three serially connected zones, an adsorption zone, a purification zone and a desorption zone, in a column of the adsorbent; contacting the feed stream with adsorbent in the adsorption zone to effect the adsorption of para-xylene; withdrawing from the adsorption zone a raffinate stream comprising ethylbenzene; contacting the adsorbent in the desorption zone with a desorbent material comprising toluene to effect the displacement of para-xylene from the adsorbent; withdrawing an extract stream comprising para-xylene from the desorption zone; and passing at least a portion of the raffinate stream to a separation means and therein separating desorbent material from ethylbenzene to produce an ethylbenzene product. The improvement resides in passing a portion of the ethylbenzene product into the adsorption zone to effect the displacement of desorbent material adsorbed by the adsorbent during a previous contacting of adsorbent with desorbent material in the desorption zone.
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