Patent ID: 6762334
Filing Date: 2004-07-13
Classification: B01D,C07C

Abstract:
A process for producing a product aromatic compound, the process comprising:a) dehydrogenating a feed stream comprising a C6-C22 paraffin in a dehydrogenation zone and recovering therefrom a dehydrogenated product stream comprising a monoolefin and aromatic byproducts; b) selectively removing at least a portion of the aromatics byproducts from the dehydrogenated product stream by at least intermittently passing at least a portion of the dehydrogenated product stream to an on-stream aromatic byproducts removal zone containing sorbent at conditions effective to selectively sorb the aromatic byproducts on the sorbent and to produce a sorption effluent stream comprising the monoolefin; c) passing at least a portion of the sorption effluent stream to a selective alkylation zone and selectively alkylating a feed aromatic compound by reacting the feed aromatic compound and the monoolefin in the selective alkylation zone to form a product aromatic compound; d) recovering from the selective alkylation zone an alkylated product stream comprising the product aromatic compound; e) at least intermittently passing a purge stream comprising a purge component to an off-stream purge aromatic byproducts removal zone containing sorbent, wherein the sorbent in the off-stream purge aromatic byproducts removal zone is contained in a sorbent bed having a void volume and wherein the void volume contains the C6-C22 paraffin or the monoolefin, to displace the C6-C22 paraffin or the monoolefin from the void volume of the sorbent bed in the off-stream purge aromatic byproducts removal zone, and producing a purging effluent stream comprising the purge component and at least one of the C6-C22 paraffin and the monoolefin; f) at least intermittently passing a desorbent stream comprising a desorption component to an off-stream desorption aromatic byproducts removal zone containing sorbent, wherein the sorbent in the off-stream desorption aromatic byproducts removal zone contains sorbed aromatic byproducts, to desorb aromatic byproducts from the sorbent in the off-stream desorption aromatic byproducts removal zone, and producing a desorption effluent stream comprising the desorption component and the aromatic byproducts; g) at least intermittently passing at least a portion of the desorption effluent stream to a prefractionator distillation column; h) separating the compounds entering the prefractionator distillation column at distillation conditions to provide a prefractionator overhead stream comprising the desorption component and a prefractionator bottom stream comprising the aromatic byproducts; i) at least intermittently passing at least a portion of the prefractionator overhead stream to a main distillation column, and at least intermittently passing at least a portion of the prefractionator bottom stream to the main distillation column, wherein the prefractionator distillation column and the main distillation column are at least partially thermally coupled; j) at least intermittently passing at least a portion of the purging effluent stream to the main distillation column; k) separating the compounds entering the main distillation column to provide a main overhead stream comprising the purge component, a first main sidedraw stream comprising the desorption component, a second main sidedraw stream comprising the desorption component, and a main bottom stream comprising the aromatic byproducts; l) at least intermittently passing at least a portion of the second main sidedraw stream to the prefractionator distillation column; and m) periodically shifting the functions of the on-stream aromatic by-products removal zone, the off-stream purge aromatic byproducts removal zone, and the off-stream desorption aromatic byproducts removal zone by operating the on-stream aromatic byproducts removal zone to function as the off-stream purge aromatic byproducts removal zone, operating the off-stream purge aromatic byproducts removal zone to function as the off-stream desorption aromatic byproducts removal zone, and operating the off-stream desorption aromatic byproducts removal zone to function as the on-stream aromatic byproducts removal zone.