Process and Apparatus for the Production of Para-xylene

摘要

The present invention is an improved process and apparatus for producing para-xylene, particularly with respect to a process that involves the methylation of toluene and/or benzene to selectively produce para-xylene, wherein streams having differing amounts of ethylbenzene are separately treated in the recovery of para-xylene. A first hydrocarbon feed comprising xylenes and ethylbenzene is provided to a first para-xylene adsorption section, and a second hydrocarbon feed comprising xylenes and less EB than the first hydrocarbon feed is provided to a second para-xylene adsorption section. Segregating the feeds with differing ethylbenzene contents increases the overall efficiency of the adsorption of para-xylene by the adsorption units. Efficiency and energy savings may be further improved by subjecting the lower-content ethylbenzene stream to liquid phase isomerization.

主权项

1. A process for producing para-xylene, the process comprising:
(a) providing a first hydrocarbon feed comprising xylenes and ethylbenzene to a first para-xylene adsorption section; (b) providing a second hydrocarbon feed comprising xylenes and less ethylbenzene than the first hydrocarbon feed to a second para-xylene adsorption section; (c) recovering a first para-xylene-rich stream and a first para-xylene-depleted stream from the hydrocarbon feed in the first para-xylene recovery unit; (d) recovering a second para-xylene-rich stream and a second para-xylene-depleted stream from the hydrocarbon feed in the second para-xylene recovery unit; (e) separating the first and second para-xylene-depleted streams into an ethylbenzene-rich stream and an ethylbenzene-depleted stream in a divided wall raffinate column, wherein the first and second para-xylene-depleted streams are provided to the divided wall raffinate column on opposite sides of the dividing wall; (f) isomerizing at least a portion of the ethylbenzene-rich stream at least partially in the vapor phase to produce a first isomerized stream having a higher para-xylene concentration than the first and second para-xylene-depleted streams; (g) isomerizing at least a portion of the ethylbenzene-depleted stream at least partially in the liquid phase to produce a second isomerized stream having a higher para-xylene concentration than the first and second para-xylene-depleted streams; (h) recycling at least a portion of the first isomerized stream to the first para-xylene adsorption section; and (i) recycling at least a portion of the second isomerized stream to the second para-xylene adsorption section.