Patent ID: 8754281
Filing Date: 2014-06-17
Classification: B01D,C07C,C10G,Y02P

Abstract:
1. A process for producing one or more individual xylene isomers from feed streams containing C8 aromatics and C9-and-heavier aromatics, comprising: (a) a distillation process comprising two or more xylene columns separating C8-aromatics streams from a C9-and-heavier aromatics streams contained in at least one higher-boiling and at least one lower-boiling feed stream, wherein the at least one higher-boiling feed stream has a higher content of C9-and-heavier aromatics than the at least one lower-boiling feed stream, comprising distilling the at least one higher-boiling feed stream in at least one first low-pressure xylene column to separate a first C8-aromatics stream from a first C9-and-heavier aromatics stream, distilling the at least one lower-boiling feed stream in at least one second xylene column at an elevated pressure above the low pressure to separate a second C8-aromatics stream from a second C9-and-heavier aromatics stream, and condensing an overhead stream from the at least one second xylene column by exchanging heat with one or more of a reboiler of the at least one first low-pressure xylene column; (b) a xylene-isomer separation process to recover one or more xylene isomers from one or both of the first and second C8-aromatics streams by injecting the one or both aromatics streams and a desorbent stream into a moving-bed adsorption process to obtain a first mixture of the one or more xylene isomers and desorbent and a second mixture of non-equilibrium C8 aromatics and desorbent; and, (c) a desorbent-recovery process to separate the first mixture of step (b) by distillation in an extract column with a reboiler having an operating pressure of at least 300 kPa to obtain the one or more individual xylene isomers and a desorbent stream returned to the xylene isomer separation process, wherein the overhead stream of the at least one second xylene column of step (a) further exchanges heat to supply the reboiler of the extract column.