Process and Apparatus for the Production of Para-xylene
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Abstract
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.
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20 Claims
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1-15. -15. (canceled)
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16. An apparatus for the production of para-xylene comprising:
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a first para-xylene adsorption section, which produces a first para-xylene-rich stream and a first para-xylene-depleted stream from a first hydrocarbon feed, and a second para-xylene adsorption section, which produces a second para-xylene-rich stream and a second para-xylene-depleted stream from a second hydrocarbon feed, the first and second para-xylene adsorption sections fluidly connected to a divided wall raffinate column in which the first and second para-xylene-depleted streams are provided to opposite sides of the dividing wall and separated 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; a vapor phase isomerization unit fluidly connected to the divided wall raffinate column to isomerize meta-xylene, ortho-xylene, and ethylbenzene in the ethylbenzene-rich stream at least partially in the vapor phase back towards to an equilibrium concentration of xylene isomers and produce a first isomerized stream having a higher para-xylene concentration than the first and second para-xylene-depleted streams; and a liquid phase isomerization unit fluidly connected to the divided wall raffinate column to isomerize the ethylbenzene-depleted stream back towards an equilibrium concentration of the xylenes isomers and produce a second isomerized stream having a higher para-xylene concentration than the first and second para-xylene-depleted streams. - View Dependent Claims (17, 18, 19, 20)
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Specification