Process for separating ethylbenzene

Claim 2

In a process for separating ethylbenzene from a feed stream comprising a mixture of ethylbenzene and para-xylene which process employs an adsorbent comprising type X or type Y zeolite containing calcium at the exchangeable cationic sites and comprises the steps of: (a) contacting the adsorbent with said feed at adsorption conditions to effect the selective adsorption of para-xylene; (b) removing a raffinate stream comprising ethylbenzene from said adsorbent; (c) contacting said adsorbent with a desorbent material comprising toluene at desorption conditions to effect the desorption of para-xylene from the adsorbent; and, (d) removing from the adsorbent an extract stream comprising para-xylene, THE IMPROVEMENT WHICH COMPRISES contacting the toluene containing adsorbent which has previously contacted desorbent material with a portion of ethylbenzene containing raffinate stream substantially free of desorbent material to effect the displacement of toluene prior to again contacting the adsorbent with the feed stream.

Claim 3

The process of claim 1 further characterized in that said feed stream contains ortho-xylene.

Claim 4

The process of claim 1 further characterized in that said feed stream contains meta-xylene.

Claim 5

The process of claim 1 further characterized in that said feed stream contains para-xylene and one other xylene isomer.

Claim 6

The process of claim 1 further characterized in that said feed stream contains para-xylene, meta-xylene and ortho-xylene.

Claim 7

The process of claim 1 further characterized in that said adsorbent comprises type X zeolite.

Claim 8

The process of claim 1 further characterized in that said adsorption conditions and desorption conditions include a temperature within the range of from about 20° to about 230° C. and a pressure within the range of from about atmospheric to about 500 psig.

Claim 9

In a process for the separation of ethylbenzene from a feed stream comprising a mixture of ethylbenzene and para-xylene which process employs an adsorbent comprising type X or type Y zeolite containing calcium at the exchangeable cationic sites and comprises the steps of:

Claim 10

In a process for the separation of ethylbenzene from a feed stream comprising a mixture of ethylbenzene and para-xylene which process employs an adsorbent comprising type X or type Y zeolite containing calcium at the exchangeable cationic sites and comprises the steps of:

Claim 11

(a) maintaining net fluid flow through a column of an adsorbent in a single direction, which column contains three zones having separate operational functions occurring therein and being serially interconnected with the terminal zones of said column connected to provide a continuous connection of said zones; (b) maintaining an adsorption zone in said column, said zone defined by the adsorbent located between a feed input stream at an upstream boundary of said zone and a raffinate output stream at a downstream boundary of said zone; (c) maintaining a purification zone immediately upstream from said adsorption zone, said purification zone defined by the adsorbent located between an extract output stream at an upstream boundary of said purification zone and said feed input stream at a downstream boundary of said purification zone; (d) maintaining a desorption zone immediately upstream from said purification zone, said desorption zone defined by the adsorbent located between a desorbent input stream at an upstream boundary of said zone and said extract output stream at a downstream boundary of said zone; (e) passing said feed stream into said adsorption zone at adsorption conditions to effect the selective adsorption of para-xylene by said adsorbent in said adsorption zone and withdrawing a raffinate stream comprising ethylbenzene from said adsorption zone; (f) passing a desorbent material comprising toluene into said desorption zone at desorption conditions to effect the displacement of para-xylene from the adsorbent in said desorption zone, and the adsorption of toluene by said adsorbent; (g) withdrawing an extract stream comprising para-xylene and desorbent material from said desorption zone; (h) passing at least a portion of said raffinate stream to a separation means and therein separating at separation conditions ethylbenzene from said desorbent material to produce an ethylbenzene product substantially free of desorbent material; (i) periodically advancing through said column of adsorbent particles in a downstream direction with respect to fluid flow in said adsorption zone the feed input stream, raffinate output stream, desorbent input stream, and extract output stream to effect the shifting of zones through said mass of adsorbent and the production of extract and raffinate streams, WHEREIN THE IMPROVEMENT COMPRISES passing a portion of said ethylbenzene product into said adsorption zone to effect the displacement of toluene adsorbed by the adsorbent during a previous contacting of said adsorbent with desorbent material in said desorption zone.

Claim 12

(a) maintaining net fluid flow through a column of an adsorbent in a single direction, which column contains three zones having separate operational functions occurring therein and being serially interconnected with the terminal zones of said column connected to provide a continuous connection of said zones; (b) maintaining an adsorption zone in said column, said zone defined by the adsorbent located between a feed input stream at an upstream boundary of said zone and a raffinate output stream at a downstream boundary of said zone; (c) maintaining a purification zone immediately upstream from said adsorption zone, said purification zone defined by the adsorbent located between an extract output stream at an upstream boundary of said purification zone and said feed input stream at a downstream boundary of said purification zone; (d) maintaining a desorption zone immediately upstream from said purification zone, said desorption zone defined by the adsorbent located between a desorbent input stream at an upstream boundary of said zone and said extract output stream at a downstream boundary of said zone; (e) passing said feed stream into said adsorption zone at adsorption conditions to effect the selective adsorption of para-xylene by said adsorbent in said adsorption zone and withdrawing a raffinate stream comprising ethylbenzene from said adsorption zone; (f) passing a desorbent material comprising toluene into said desorption zone at desorption conditions to effect the displacement of para-xylene from the adsorbent in said desorption zone, and the adsorption of toluene by said adsorbent; (g) withdrawing an extract stream comprising para-xylene and desorbent material from said desorption zone; (h) passing at least a portion of said raffinate stream to a separation means and therein separating at separation conditions ethylbenzene from said desorbent material to produce an ethylbenzene product substantially free of desorbent material; (i) periodically advancing through said column of adsorbent particles in a downstream direction with respect to fluid flow in said adsorption zone the feed input stream, raffinate output stream, desorbent input stream, and extract output stream to effect the shifting of zones through said mass of adsorbent and the production of extract and raffinate streams, WHEREIN THE IMPROVEMENT COMPRISES passing a portion of said ethylbenzene product into said adsorption zone to effect the displacement of toluene adsorbed by the adsorbent during a previous contacting of said adsorbent with desorbent material in said desorption zone.

Claim 13

The process of claim 8 further characterized in that said feed stream contains ortho-xylene.

Claim 14

The process of claim 8 further characterized in that said feed stream contains meta-xylene.

Claim 15

The process of claim 8 further characterized in that said feed stream contains para-xylene and one other xylene isomer.

Claim 16

The process of claim 8 further characterized in that said feed stream contains para-xylene, meta-xylene and ortho-xylene.

Claim 17

The process of claim 8 further characterized in that said adsorbent comprises type X zeolite.

Claim 18

The process of claim 8 further characterized in that said adsorbent contains from about 2 to about 15 wt. % calcium.

Claim 19

The process of claim 8 further characterized in that said adsorbent contains from about 0.2 to 4 wt. % H 2 O measured by loss on ignition at 500° C.

Claim 20

The process of claim 8 further characterized in that it includes the step of maintaining a buffer zone immediately upstream from said desorption zone, said buffer zone defined as the adsorbent located between the desorbent input stream at a downstream boundary of said buffer zone and a raffinate output stream at an upstream boundary of said buffer zone.

Claim 21

The process of claim 8 further characterized in that it includes the step of passing at least a portion of said extract output stream to a separation means and therein separating at separation conditions desorbent material to produce an extract product substantially free of desorbent material.

Claim 22

The process of claim 8 further characterized in that said adsorption conditions and desorption conditions include a temperature within the range of from about 20° C. to about 230° C. and a pressure within the range of from about atmospheric to about 500 psig.

Claim 23

The process of claim 8 further characterized in that the ethylbenzene product passing into the adsorption zone enters the adsorption zone at a point closer to the feed input stream than to the raffinate output stream.