Method of recovering paraxylene from a mixture of aromatic hydrocarbons
A method for recovering paraxylene from a mixture of aromatic hydrocarbons. The process uses a pressure swing adsorption zone followed by a paraxylene recovery zone. The invention provides for lower throughput through the paraxylene recovery zone, resulting in lower capital costs and operating costs.
1. A process for the recovery of a paraxylene product from a mixture of C8 aromatic hydrocarbons, the process comprising:
introducing a feed stream comprising C8 aromatics hydrocarbons to a fractionation zone and separating the feed stream into an overhead product, a bottoms product, and a sidedraw product comprising xylenes, at least a portion of the sidedraw product being in a vapor phase;
condensing at least a portion of the sidedraw product being in the vapor phase to form a sidedraw condensate comprising a C8-rich aromatic hydrocarbon mixture;
pressurizing the sidedraw condensate comprising a C8-rich aromatic hydrocarbon mixture using a pump thereby producing a pressurized C8-rich aromatic hydrocarbon mixture;
pre-heating the pressurized C8-rich aromatic hydrocarbon mixture thereby producing a pre-heated C8-rich aromatic hydrocarbon mixture;
introducing the pre-heated C8-rich aromatic hydrocarbon mixture to a pressure swing adsorption unit operated in a vapor phase and separating the pre-heated C8-rich aromatic hydrocarbon mixture into a paraxylene-rich stream and a first paraxylene-lean stream; and
introducing the paraxylene-rich stream to a crystallization zone and separating at least a portion of the paraxylene-rich stream in the crystallization zone to form a paraxylene product stream and a second paraxylene-lean stream.
2. The process of claim 1 , further comprising isomerizing the first paraxylene-lean stream to form an isomerate having a paraxylene concentration greater than the paraxylene concentration of the first paraxylene-lean stream.
3. The process of claim 1 , further comprising isomerizing the second paraxylene-lean stream in a second isomerization reactor to form a second isomerate having a paraxylene concentration greater than the paraxylene concentration of the second paraxylene-lean stream.
4. The process of claim 3 , further comprising converting ethylbenzene to other compounds in the second isomerization reactor.
5. The process of claim 4 , further comprising feeding the isomerate and the second isomerate to the fractionation zone.