Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1997-06-04
1999-03-23
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210674, 210690, 585826, 585828, B01D 1500
Patent
active
058847774
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method for adsorptively separating one or more components through the selectivity of an adsorbent from a mixture of feed containing both selectively adsorbed component A(containing one or more components) and a relatively less adsorbed component B(containing one or more components). More particularly, this invention relates to a method for separating a kind of isomer from a mixture of hydrocarbon feed containing several isomers. This invention specifically relates to a method for producing high-purity para-xylene through the improved adsorptive separation process from a mixture of feed containing para-xylene and its other isomers.
BACKGROUND OF THE INVENTION
It is well known that adsorptive separation is one of the separation methods widely adopted in the chemical industry, especially in petrochemical industry. For quite some time, this method has been adopted to separate a component which is difficult to be separated by other means from a mixture of feed containing various components.
In the prior art , there are abundant patent literatures describing methods for separating one kind of hydrocarbon from the other isomers. For instance, methods for separating para-isomers of monocyclic aromatics substituted by dialkyl group from other isomers, especially for separating paraxylene from other xylene isomers by employing a specific zeolite molecular sieve adsorbent to preferably adsorb para-isomers have been published in literatures of U.S. Pat. No. 3,626,5020, U.S. Pat. No. 3,663,638, U.S. Pat. No. 3,665,046, U.S. Pat. No. 3,700,744, U.S. Pat. No. 3,686,342, U.S. Pat. No. 3,734,47, U.S. Pat. No. 3,394,109, U.S. Pat. No. 3,997,620, CN1022622, CN1022826, CN10493294, CN1051549A, CN1064071 and CN1047489A in which benzene, toluene, chlorobenzene, fluoro-aromatics, halogen toluene, para-dialkylbenzene,diethyltoluene, and tetraline are respectively recommended as the desorbent depending on the composition of mixture of the feed.
A process of adsorptive separation may be effected both on a fixed bed or a moving bed , preferably on a simulated countercurrent moving bed system. For example, a simulated countercurrent moving bed system has been adopted for adsorptive separation in U.S. Pat. No. 2,985,589, U.S. Pat. No. 3,268,604 and U.S. Pat. No. 3,268,605 while a rotary valve for the system of simulated countercurrent moving bed has been disclosed in U.S. Pat. No. 3,040,777 and U.S. Pat. No. 3,422,848. Some drawbacks in the prior art , the objects of this invention and the scheme of settlement will be further explained hereinafter with reference to the accompanying drawing.
The drawing is a principle depiction of a continuous adsorptive separation system of a simulated countercurrent moving bed.
Referring to the drawing, a adsorptive separation system comprises four zones, consecutively as adsorption zone, purification zone, desorption zone and buffer zone. In the drawing, F represents a feed stream containing a selectively adsorbed component A and a relatively less adsorbed component B, D represents a desorbent stream, E represents an extract, i.e. a stream of desorbent containing the selectively adsorbed component A, R represents a raffinate, i.e. the remaining stream containing the relatively less adsorbed component B after desorption, H.sub.(in) and H.sub.(out) respectively represent an inflowing and an outflowing stream enriched in said desorbent for the primary flush stream for the lines connecting the adsorptive beds, X represents the secondary flush stream for the lines connecting the adsorptive beds, and M represents the simulated adsorbent moving direction shifted by the rotary valve. Zone I is between F and R wherein the charged feed contacts countercurrently with the adsorbent, and the selectively adsorbed component A shifts from the feed stream into the pores of said adsorbent, displacing the desorbent D from the pores at the same time. Thus, zone I is defined as adsorption zone. Zone II is between F and E. For the reason that the adsorbent adsorbs sel
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Chen Weimin
Li Yousong
Pan Weizhong
Wang Yubing
Xue Yusong
Cintins Ivars
Yangzi Petro-Chemical Corp. Sinopec
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