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 para-xylene, meta-xylene, ortho-xylene, and ethylbenzene to a first para-xylene adsorption section; (b) providing a second hydrocarbon feed comprising para-xylene, meta-xylene, ortho-xylene, 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 first hydrocarbon feed from the first para-xylene adsorption section; (d) recovering a second para-xylene-rich stream and a second para-xylene-depleted stream from the second hydrocarbon feed from the second para-xylene adsorption section; (e) separating the first and second para-xylene-depleted streams into an ethylbenzene-rich stream, which contains a majority portion of the ethylbenzene from the first and second para-xylene-depleted streams, and an ethylbenzene-depleted stream, which contains a minor portion of the ethylbenzene from the first and second para-xylene-depleted streams, 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 meta-xylene, ortho-xylene, and ethylbenzene in at least a portion of the ethylbenzene-rich stream at least partially in the vapor phase back towards to an equilibrium concentration of xylene isomers to produce a second isomerized stream having a higher para-xylene concentration than the para-xylene-depleted stream; (g) isomerizing at least a portion of the ethylbenzene-depleted stream at least partially in the liquid phase back towards an equilibrium concentration of the xylenes isomers to produce a first isomerized stream having a higher para-xylene concentration than the para-xylene-depleted stream; (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.