Improved hydrocarbon separation process

Claim 2

Claim 2 further characterized in that said adsorbent contains at least one pair of cations selected from the group consisting of potassium and barium, potassium and beryllium, potassium and magnesium, rubidium and barium, cesium and barium, potassium and rubidium, and potassium and cesium and combinations thereof.

Claim 3

In an improved process for the separation of para-xylene from a feed containing a mixture of C8 aromatic hydrocarbons which process employs a crystalline aluminosilicate adsorbent particles selected from the group consisting of Type X structured and Type Y structured zeolites containing at least one selected cation at the exchangeable cationic sites within said zeolite and having interstitial void spaces between said particles, said process comprising the steps of: i. contacting said adsorbent with said feed at adsorption conditions to effect the selective adsorption of para-xylene by the adsorbent; ii. removing a raffinate material from the adsorbent which comprises less selectively adsorbed components of the feed; iii. contacting said adsorbent with a desorbent material containing para-diethylbenzene at desorption conditions to effect the desorption of said para-xylene from said adsorbent; iv. removing extract material comprising para-diethylbenzene and para-xylene from said adsorbent; wherein the improvement comprises using desorption conditions comprising a two step desorption operation in which: a. a first desorbent stream containing para-diethylbenzene contacts said adsorbent to effect the desorption of para-xylene therefrom; and b. a second desorbent stream comprising a saturated hydrocarbon containing less para-diethylbenzene than said first desorbent stream contacts said adsorbent to effect the flushing of desorbed para-xylene and said first desorbent stream from the interstitial void spaces between said particles.

Claim 4

Claim 4 further characterized in that said adsorbent contains at least one cation selected from the group consisting of lithium, sodium, potassium, beryllium, magnesium, calcium, strontium, barium, nickel, copper, silver, manganese, cadmium, and combinations thereof.

Claim 5

Claim 5 further characterized in that said adsorbent contains at least two pairs of cations selected from the group consisting of potassium and barium, potassium and beryllium, potassium and magnesium, rubidium and barium, cesium and barium, potassium and rubidium, and potassium and cesium, and combinations thereof.

Claim 6

Claim 4 further characterized in that said first desorbent stream contains more than ten volume percent para-diethylbenzene.

Claim 7

Claim 4 further characterized in that said second desorbent contains less than ten volume percent para-diethylbenzene.

Claim 8

Claim 8 further characterized in that said second desorbent stream contains less than two volume percent para-diethylbenzene.

Claim 9

Claim 9 further characterized in that said second desorbent stream is free of para-diethylbenzene.

Claim 10

An improved process for the separation of para-xylene from a feed containing a mixture of C8 aromatic hydrocarbons, which process employs crystalline aluminosilicate adsorbent particles selected from the group consisting of Type X structured and Type Y structured zeolites containing at least one selected cation at the exchangeable cationic sites within said zeolite and having interstitial void spaces between said particles, said process comprising the steps of: i. contacting said adsorbent with said feed at adsorption conditions to effect the selective adsorption of para-xylene on the adsorbent by displacing para-diethylbenzene present at the selective pore volume of the adsorbent from a hereinafter defined desorption operation; ii. removing a raffinate material from the adsorbent which comprises the less selectively adsorbed components of the feed stock and displaced para-diethylbenzene; iii. contacting said adsorbent with desorbent material containing para-diethylbenzene at desorption conditions to effect a desorption of saiD para-xylene from said adsorbent by para-diethylbenzene which is adsorbed at the selective pore volume of the adsorbent; iv. removing extract material comprising para-xylene and desorbent material from said adsorbent; v. passing at least a portion of the raffinate material to a raffinate separation means at separation conditions to effect the separation of para-diethylbenzene from the feed stock components in the raffinate material; vi. passing at least a portion of said extract material to an extract separation means at separation conditions to effect the separation of para-xylene from desorbent material; wherein the improvement comprises using desorption conditions comprising a two-step desorption operation in which: a. a first desorbent stream derived from said raffinate separation means containing para-diethylbenzene contacts said adsorbent to effect the desorption of para-xylene therefrom, and b. a second desorbent stream derived from said extract separation means comprising material containing less para-diethylbenzene than said first desorbent stream contacts said adsorbent to effect the flushing of desorbed para-xylene from the interstitial void spaces from said particles.