Separation and recovery of ethylbenzene by dual desorbent composition and temperature separation processes

In a process for continuously separating, in a liquid phase, the components of a liquid C.sub.8 aromatic feedstream containing a xylene isomer and ethylbenzene wherein at least one of said components is selectively adsorbed by contact with a solid sorbent material, utilizing a simulated countercurrent flow system wherein liquid streams are allowed to flow downward through a desorption zone, a rectification zone and a sorption zone, each zone being serially and circularly interconnected and divided into a plurality of serially interconnected sections, each section being packed with a mass of said solid sorbent material, the improvement which comprises:

• a. introducing, into the first section of said desorption zone, a first desorbent stream comprising a desorbent selected from the group consisting of m-diisopropylbenzene, toluene, p-diethylbenzene, o-dichlorobenzene and a mixture of diethylbenzene isomers in an amount ranging from about 40 to about 100 weight percent and a paraffinic diluent having from 8 to 16 carbon atoms;
• b. withdrawing a desorption effluent containing ethylbenzene from the last section of said desorption zone;
• c. introducing, into the first section of said rectification zone, a second desorbent stream containing said paraffinic diluent and from about 15 to about 60 weight percent of said desorbent;
• b. introducing said hydrocarbon feedstream into the first section of said sorption zone;
• e. withdrawing a raffinate effluent containing said xylene isomer from the last section of said sorption zone;
• and
• f. wherein the concentration of said desorbent present in the first desorbent stream is higher than the concentration of said desorbent present in the second desorbent stream by at least 20 weight percent.

In a process for continuously separating, in a liquid phase, the components of a liquid C.sub.8 aromatic feedstream containing a xylene isomer and ethylbenzene wherein at least one of said components is selectively adsorbed by contact with a solid sorbent material, utilizing a simulated countercurrent flow system wherein liquid streams are allowed to flow downward through a desorption zone, a rectification zone and a sorption zone, each zone being serially and circularly interconnected and divided into a plurality of serially interconnected sections, each station being packed with a mass of said solid sorbent materials, the improvement which comprises:

• a. introducing, into the first section of said desorption zone, a first desorbent stream comprising a desorbent selected from the group consisting of m-diisopropylbenzene, toluene, p-diethylbenzene, o-dichlorobenzene and a mixture of diethylbenzene isomers in an amount ranging from about 40 to about 100 weight percent and a paraffinic diluent having from 8 to 16 carbon atoms;
• b. withdrawing a desorption effluent containing said xylene isomer from the last section of said desorption zone;
• c. introducing, into the first section of said rectification zone, a second desorbent stream containing said paraffinic diluent and from about 15 to about 60 weight percent of said desorbent;
• d. introducing said hydrocarbon feedstream into the first section of said sorption zone;
• e. withdrawing a raffinate effluent containing ethylbenzene from the last section of said sorption zone;
• and
• f. wherein the concentration of said desorbent present in the first desorbent stream is higher than the concentration of said desorbent present in the second desorbent stream by at least 20 weight percent.