KR101974770B1 - Method and apparatus for the production of para-xylene - Google Patents

Abstract

The present invention is an improved method and apparatus for the production of para-xylenes, particularly associated with a process involving the methylation of toluene and / or benzene to produce para-xylenes, wherein a stream having a different amount of ethylbenzene Is treated separately at the recovery of para-xylene. A first hydrocarbon feed comprising xylene and ethylbenzene is provided in a first para-xylene adsorption section, and the second hydrocarbon feed comprising less than EB and the first hydrocarbon feed comprises a second para - It is fed into the xylene adsorption section. Separation of the feed with different ethylbenzene content increases the overall efficiency of adsorption of para-xylene by the adsorption unit. The efficiency and energy savings can be further improved by liquid-isomerizing the lower content of ethylbenzene stream.

Description

Method and apparatus for the production of para-xylene

Inventor : Robert G. Tinger, Dana L. Filialo, Michael Mo Linear

Cross-reference of related application - reference

This application claims the benefit of U.S. Provisional Application No. 62 / 154,774, filed April 30, 2015, and European Patent Application No. 15171577.8, filed on June 11, 2015.

The technical field of the present invention

The present application relates to an improved method and apparatus for the production of para-xylene, especially recovery of para-xylene from a stream having different amounts of ethylbenzene.

Ethylbenzene (EB), para-xylene (PX), ortho-xylene (OX) and meta-xylene (MX) are commonly present together in the C ₈ aromatic product stream from chemical plants and refineries. While high purity EB is an important raw material for the production of styrene, all high purity EB feedstocks used for styrene production for a variety of reasons are produced by alkylation of benzene with ethylene, rather than by recovery from the C ₈ aromatic stream. Among the three xylene isomers, PX has the largest commercial market and is mainly composed of terephthalic acid and terephthalic acid for use in the manufacture of various polymers such as poly (ethylene terephthalate), poly (propylene terephthalate), and poly (butene terephthalate) It is used for the production of esters. OX and MX are useful as solvents and raw materials for the production of products such as phthalic anhydride and isophthalic acid while the market demand for OX and MX and its downstream derivatives is smaller than for PX.

There is considerable commercial interest in maximizing PX production from any given source of C ₈ aromatics when there is a higher demand for PX compared to other isomers thereof. However, there are a number of key technical challenges to overcome in achieving this goal to maximize PX yield. For example, four C ₈ aromatics, especially three xylene isomers, are generally present at the concentrations indicated by the thermodynamics of the production of the C ₈ aromatic stream in a particular plant or refinery facility. As a result, PX production is limited to the amount that is inherent in the C ₈ aromatic stream at most, unless additional processing steps are used to increase the amount of PX and / or to improve the PX recovery efficiency. Various methods are known to improve the concentration of PX in C ₈ aromatic streams. These methods generally involve separating at least a portion of PX to produce a PX-deficient stream and circulating a stream between the xylene isomerization step in which the PX content in the PX-deficient stream is restored to an equilibrium concentration .

In a typical aromatic plant, the C ₈ < ₊ > aromatic feed stream, which is previously treated by a known method for removing the liquid feed, typically C ₇ -type (especially benzene and toluene) shown in Figure 1, 3). ≪ / RTI > Xylene reprocessing column (or, more simply, fractionation column) is evaporated and the feedstock, the xylene overhead mixture 5 and C ₉₊ aromatic (OX, MX, and PX) and ethylbenzene (EB) The C ₈ aromatics are separated into the lower product (61) containing. The overhead mixture typically has a composition of about 40-50% metaxylene (MX), 15-25% PX, 15-25% OX, and 10-20% EB. Unless otherwise indicated herein, percentages are by weight.

The overhead mixture 5 is then transported to the PX recovery unit 15, which may use crystallization techniques, adsorption techniques, or membrane separation techniques. These techniques can separate PX from its isomers and produce high purity PX up to 99.9%, which is collected from unit 15 via conduit 17. Unit 15. The adsorption separation unit, for example Parex ^TM or if the Eluxyl ^TM unit, a desorbent, such as p - ethyl benzene extract (17) containing (PDEB) is desired extract in distillation column 19, for example by distillation It is required to be separated from the PX. This produces a high purity PX stream 27, which may contain light impurities such as toluene, non-aromatic and water, which is further removed in a downstream column (not shown) to further improve PX purity. The desorbent is returned to the PX recovery system 15 via conduit 21.

Raffinate 65 containing predominantly MX, OX, EB and desorbent is transported to fractionation column 37 which produces stream 35 containing MX, OX, and EB, and bottom 63 do. The desorbent in the lower product 63 is returned to 15. As used herein, the term " raffinate " is used to mean a portion recovered from the PX recovery unit 15 regardless of whether the technique used is adsorption separation, crystallization, or membrane. Stream 35 is transported to isomerization unit 43 to isomerize MX and OX and, optionally, EB into an equilibrium mixture of four isomers. The isomerization unit 43 may be a vapor or liquid isomerization unit or both. The product of the isomerization unit 43 is transported via a conduit 51 to the _C7- distillation column 53, which transfers the product of the isomerization to the bottoms stream 59 comprising equilibrated xylene and _C7- aromatic, For example, overhead 47 comprising benzene and toluene. The bottom product 59 of the distillation column 53 is then transported to the xylene reprocessing column 3 which is either merged with the feed 1 as in Figure 1 or by a separate inlet (not shown) Can be injected.

However, the presence of EB in the C ₈ aromatic stream can affect the efficiency of the specific process described above. In particular, when an adsorptive separation unit is used for PX recovery, the adsorbent has a higher affinity for PX, while it can also adsorb EB to a considerable extent, thereby reducing the capacity of the adsorbent to adsorb PX . It is therefore desirable to reduce or minimize the amount of EB in the C ₈ aromatic stream delivered to the adsorbing separation unit, in order to avoid EB competition for adsorption capacity and to increase the efficiency of PX adsorption. In addition, the liquid isomerization converts EB which is slightly or absent in the PX-deficient stream, so that the amount of EB in the xylene loop can accumulate to a very high level. Thus, in order to maximize the use of liquid isomerization, it is also desirable to control the amount of EB in the PX-deficient stream that is subjected to liquid isomerization.

SUMMARY OF THE INVENTION

The present invention is an improved process for the preparation of PX, particularly associated with a process involving the methylation of toluene and / or benzene to selectively produce PX, wherein the stream with different amounts of EB is treated separately at the time of recovery of PX . A first hydrocarbon feed comprising xylene and EB is fed to the first PX adsorption section and the first PX-rich stream and the first PX-deficient stream are withdrawn from the feed. The second hydrocarbon feed comprising xylene and less EB than the first hydrocarbon feed is provided in a second PX adsorption section wherein the second PX-rich stream and the second PX-deficient stream are recovered from the feed . Separation of feeds having different EB contents increases the overall efficiency of adsorption of PX by the adsorption unit. The first and second PX adsorption sections may be individual PX adsorption units or individual towers of a single PX adsorption unit. In an embodiment, prior to the adsorption interval PX, the first hydrocarbon feed is first passed to a xylene fractionation column, a first overhead containing C ₈ hydrocarbons to be transported to the suction region PX and C ₉₊ streams A first bottoms stream containing hydrocarbons can be produced. Similarly, the second hydrocarbon feed is a second bottoms stream comprising a second overhead stream, and the C ₉₊ hydrocarbons containing C ₈ hydrocarbons to be transported to the second absorption zone PX through the second xylene fractionation column Can be generated.

The first and second PX-deficient streams provided on opposite sides of the separation wall in the separating wall raffinate column are then separated into an EB-rich stream and an EB-deficient stream. At least a portion of the EB-rich stream is then fed to a xylene isomerization unit wherein the EB-rich stream is isomerized under at least partial vapor conditions to produce a higher PX concentration than the first and second PX- 1 < / RTI > isomerized stream. At least a portion of the EB-deficient stream is then fed to a xylene isomerization unit wherein the EB-deficient stream is isomerized under at least partial liquidus conditions to produce a PX-rich solution having a higher PX concentration than the first and second PX- 2 < / RTI > isomerized stream. Because the vapor isomerization is more effective at converting EBs than liquid isomerization, but liquid isomerization is more energy efficient, separating the PX-deficient stream based on the EB content and adding each to a suitable isomerization process results in process efficiency And maximizes effectiveness. At least a portion of the first isomerization stream is then recycled to the first PX adsorption section or optionally to the first xylene fractionation tower and at least a portion of the second isomerization stream is then fed back to the second PX adsorption section or optionally to the second xylene Recycled to the fractionation tower to recover additional PX. This process is then repeated to define the so-called xylene isomerization loop.

The present invention also provides a process for the production of a first PX-rich stream and a second PX-rich stream from a first hydrocarbon feedstock and a first PX adsorption section for producing a first PX-rich stream and a first PX- And a second PX adsorption section for producing a stream. The first and second PX adsorption sections are in fluid communication with the separation wall raffinate column wherein the first and second PX-deficient streams are separated into an EB-rich stream and an EB-deficient stream. The fluid-communicating split-wall raffinate column comprises a vapor-isomerization unit that isomerizes the EB-rich stream and produces a first isomerized stream having a higher PX concentration than the first and second PX- Is a liquid isomerization unit that isomerizes the depleted stream and produces a second isomerized stream having a higher PX concentration than the first and second PX-deficient streams. In an embodiment, the first xylene fractionation column is in fluid communication with the downstream of the vapor isomerization unit and upstream of the first PX adsorption section, and the second xylene fractionation column is downstream of the liquid isomerization unit and the second PX adsorption And is in fluid communication with the upstream of the section.

1 is a flow diagram of a conventional para-xylene (PX) preparation and extraction process using liquid xylene isomerization and gaseous xylene isomerization.
2 is a flow chart of one embodiment of the present invention.
3 is a flow chart of a second embodiment of the present invention.
4 is a flow chart of a third embodiment of the present invention.
5 is a flowchart of a fourth embodiment of the present invention.

As used herein, the term " C _n " hydrocarbons in which n is a positive integer means a hydrocarbon having n number of carbon atom (s) per molecule. By way of example, a C ₈ aromatic hydrocarbon means a mixture of aromatic hydrocarbons or aromatic hydrocarbons having 8 carbon atoms per molecule. n is a positive integer The term "C _n +" hydrocarbons, on the other hand means a hydrocarbon having a carbon atom (s) of the number of one at least n per molecule, and n is a positive integer The term "C _n -" hydrocarbon group per molecule of n Means a hydrocarbon having a number of carbon atom (s) or less.

The present invention is an improved method and apparatus for producing PX, particularly in connection with a process involving the methylation of toluene and / or benzene to selectively produce PX, wherein streams having different amounts of ethylbenzene are separately treated Thereby increasing the efficiency of PX recovery. Referring to Figure 2, a first hydrocarbon feed 102 comprising xylene and EB is provided in a first para-xylene adsorption section 130 wherein the first PX-rich stream 132 and the first PX- The PX-deficient stream 134 is recovered from the feed. Xylene and a second hydrocarbon feed 104 containing less EB than the first hydrocarbon feed is fed to the second para-xylene adsorption section 140 where the second PX-rich stream 142 and / The second PX-deficient stream 144 is recovered from the feed. The first and second PX-depleted streams 134 and 144 are then separated into an EB-rich stream 172 and an EB-depleted stream 174 in a separate wall raffinate column 170. At least a portion of the EB-rich stream 172 is then fed to the xylene isomerization unit 180 and the EB-rich stream 172 is at least partially isomerized under meteoric conditions to form first and second PX- Produces a first isomerization stream (182) having a higher PX concentration than the first isomerization stream (134, 144). At least a portion of the EB-deficient stream 174 is then supplied to the xylene isomerization unit 190 where the EB-deficient stream 174 is at least partially isomerized under liquid conditions to form first and second PX- Producing a second isomerization stream 192 having a higher PX concentration than the streams 134, 144. At least a portion of the first isomerization stream 182 is then circulated to the first para-xylene adsorption section 130 and at least a portion of the second isomerization stream 192 is subsequently recycled to the second para- 140) to recover additional PX, and the process is repeated to define a so-called xylene isomerization loop.

hydrocarbon Supply

The first hydrocarbon feed 102 used in the process of the present invention may be any hydrocarbon stream containing xylene and EB, such as, but not limited to, a lipomate stream (product stream of the lipomate separation column), a hydrocracking product stream , A xylene or EB reaction product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, a Cyclar ™ process stream, and / or an import stream. The first feed 102 may contain at least 1.0 wt%, 2.0 wt%, 3.0 wt%, 5.0 wt%, 7.5 wt%, or 10.0 wt% EB.

The second hydrocarbon feed 104 may be a hydrocarbon stream containing less EB than xylene and the first hydrocarbon feed such as, but not limited to, a PX selective aromatic alkylation product stream, a non-selective (equilibrium PX) aromatic alkylation product stream, From a C ₂ -C ₄ alkane / alkene to aromatics product stream, an import stream, and / or from a PX recovery unit May be an off-spec PX stream. The second feed 104 may contain up to 10.0 wt%, 7.5 wt%, 5.0 wt%, 3.0 wt%, 2.0 wt%, or 1.0 wt% of EB, as long as it is less than the EB content of the first feed 102 can do.

In one embodiment, the second hydrocarbon feed 104 is the product of selective alkylation of benzene and / or toluene with methanol and / or dimethyl ether in a methylation reactor. The reactor can be a fluidized bed, a mobile bed, a fixed bed, a circulating bed, or a combination thereof. One fluidized bed methylation reactor is described in U.S. Patent Nos. 6,423,879 and 6,504,072, the entire contents of which are incorporated herein by reference, and a temperature of 120 ° C and 2,2 dimethylbutane pressure of 60 torr (8 kPa) And a porous crystalline material having a diffusion parameter of 2,2-dimethylbutane of about 0.1 - 15 sec < ^-1 > The porous crystalline material can be a mid-pore zeolite, such as ZSM-5, which can be used to control the reduction of the micropore volume of the material during the steaming step, for example, Lt; RTI ID = 0.0 > 950 C. < / RTI > Examples of fixed bed processes and catalysts are described in U.S. Patent Nos. 7,304,194 and 8,558,046, which describe the use of phosphorus-modified ZSM- 5 catalyst.

The feed may further comprise recycle stream (s) from the isomerization step (s) and / or various separation steps. The hydrocarbon feed comprises PX with MX, OX, and EB. In addition to xylene and EB, the hydrocarbon feed may also contain a certain amount of other aromatics or even non-aromatic compounds. Examples of such aromatic compounds include C ₇ - hydrocarbon, such as benzene and toluene, and C ₉ + aromatics, such as mesitylene, pseudo kyuren like. This type of feed stream (s) is described in Handbook of Petroleum Refining Processes, Eds. Robert A. Meyers, McGraw-Hill Book Company, Second Edition.

Depending on the first and second hydrocarbon feeds 102 and 104, one or more initial separation steps, which serve to remove C ₇ - and C ₉ + hydrocarbons from the feed, 104 to the first and second para-xylene adsorption sections 130, 140. In general, the initial separation step may include fractionation, crystallization, adsorption, reactive separation, membrane separation, extraction, or a combination thereof. In one embodiment, the first hydrocarbon feed (102) passes through the first xylene fractionation tower (110) before passing through the first para-xylene adsorption section (130). The first xylene fractionation tower 110 comprises a first overhead stream 112 comprising C ₈ hydrocarbons transported to a first para-xylene adsorption section 130, and a second overhead stream 112, To produce a first bottoms stream 114 containing _C9 < + > hydrocarbons.

Similarly, the second hydrocarbon feed 104 passes through the second xylene fractionation tower 120 before passing through the second para-xylene adsorption section 140. Second xylene fractionation tower 120 second para-xylene the second overhead stream 122 and second bottoms containing the C ₉₊ hydrocarbons containing C ₈ hydrocarbons to be transported to the adsorption zone (140) Stream 124 is generated. The second hydrocarbon feed 104 may be subjected to phenol and styrene removal steps such as those described in U.S. Patent Nos. 2013/0324779 and 2013/0324780 before or after the second xylene fractionation tower 120 , Which is incorporated herein by reference in its entirety. The second bottoms stream 124 may also optionally be treated with a second bottoms stream 114 prior to passing through a transalkylation unit (not shown) with the first bottoms stream 114, such as those described in U.S. Patent Nos. 2013/0324779 and 2013/0324780 Phenol and styrene removal steps.

Depending on material balance and equipment requirements, a portion of the first hydrocarbon feed 102 may be associated with the second hydrocarbon feed 104 prior to the xylene rectification column, or vice versa. Likewise, a portion of the overhead stream 112 may be associated with the overhead stream 122 prior to the PX adsorption periods 130, 140, or vice versa.

Para-xylene recovery

In an embodiment where a first xylene rectifϊed tower is used, a first overhead stream 112, or first hydrocarbon feed 102, comprising C ₈ hydrocarbons is fed to the first para-xylene adsorption section 130 To produce a first PX-enriched product stream 132 and a first PX-depleted stream 134. In an embodiment where a second xylene rectifier column is used, a second overhead stream 122, or a second hydrocarbon feed 104 comprising C ₈ hydrocarbon, is fed to the second para-xylene adsorption section 140 To produce a second PX-rich product stream 142 and a second PX-deficient stream 144. In one embodiment, the first and second PX-rich product streams 132 and 142 comprise at least 10 wt% PX, preferably at least 50 wt% PX based on the total weight of the PX rich product stream, Comprises at least 70 wt% PX, even more preferably at least 80 wt% PX, most preferably at least 90 wt% PX, ideally at least 95 wt% PX.

The first and second para-xylene adsorption sections 130, 140 preferably simulate a moving bed adsorber unit, such as a PAREX ™ unit or an ELUXYL ™ unit. This type of separation unit (s) and its design is described in Perry ' s Chemical Engineers ' Handbook ' Eds. R.H. Perry, D.W. Green and J.O. Maloney, McGraw-Hill Book Company, Sixth Edition, 1984, and the aforementioned Handbook of Petroleum Refining Processes. In a typical simulated moving bed adsorption unit, the adsorbent bed composed of a plurality of sub-beds is contained in two adsorption towers connected in series. In one embodiment, the first para-xylene adsorption section 130 and the second para-xylene adsorption section 140 are separate simulated moving bed adsorption units and have two adsorption towers in each section. In another embodiment, the first para-xylene adsorption section 130 and the second para-xylene adsorption section 140 each comprise one tower of a single simulated moving bed adsorption unit.

Feeds having different EB contents, for example, feeds having EBs of less than 1.0 wt% and EBs of greater than 1.0 wt% separately produce more efficient adsorption of PX. The adsorbent has a higher affinity for PX while it also adsorbs EB to a considerable extent, thereby reducing the capacity of the adsorbent to adsorb PX. Thus, feeding a feed having a smaller amount of EB, i.e., less than 1.0 wt% of EB, to a separate PX adsorption section minimizes the amount of EBs competing for adsorption capacity and reduces the efficiency of PX adsorption , Which in turn causes more efficient adsorption of PX.

2, such as a conventional simulated moving bed plant structure, the first and second PX-enriched product streams 132, 142 comprising PX and desorbent are transported to the extraction column 150 for separation, Stream 152 and a first desorbent stream 154. < RTI ID = 0.0 > The first desorbent stream 154 is optionally recycled through the adsorbent drum to the first and second para-xylene adsorption sections 130,140. The PX stream 152 is then transported to the finishing column 160, which produces a purified PX product 162. The toluene stream 164 is recovered as an overhead product from the finishing column 160 and can be recycled back to the PX manufacturing process, preferably selective alkylation of benzene and / or toluene with methanol and / or dimethyl ether . In a conventional simulated moving bed plant structure, the PX-deficient stream comprising MX, OX, EB, and desorbent is transported to a raffinate column; However, in the present process, the separating wall raffinate column is replaced by a conventional raffinate column, which will be described below.

Separation wall Raffinate column

2, the first and second PX-depleted streams 134 and 144 are separated by a separate wall raffinate column 170 that replaces a conventional raffinate column (rectification column 37 in FIG. 1) Which feeds the first and second PX-depleted streams 134 and 144 to the three stream-EB-rich streams 172, the EB-depleted stream 174, and the second desorbent stream 176 Separate. As its name implies, the term " separation wall distillation column " refers to a distillation column of a particularly well-known type comprising a separation wall. The separating wall bisects a portion of the interior of the distillation column vertically, but does not extend the upper or lower section of the column, thereby allowing the column to be refluxed and re-charged similar to conventional columns. The separating wall provides a fluid impermeable baffle dividing the interior of the column. An inlet for a column located on one or more side draws located on one side and opposite side of the separating wall, or an inlet for a plurality of draws from both sides of the separating wall column and the top surface and bottom of the column, The column can be structured for multiple processes.

In certain embodiments, the separation walls extend down from the top of the column down to the trays where the EB concentration is low enough to provide an optimal ratio of low EB and high EB products, ≪ / RTI > The first PX-depleted stream 134, derived from the first hydrocarbon feed 102 having a higher EB concentration, is provided to the separating wall raffinate column 170 on one side of the separating wall and has a lower EB concentration A second PX-depleted stream 144 derived from the second hydrocarbon feed 104 is provided to the separate wall raffinate column 170 on the opposite side of the separation wall. The EB-rich stream 172 and the EB-deficient stream 174 are removed from the top of the column or near the top of the column to remove harder components such as water. Each overhead stream may be processed through a separate overhead product system (not shown), and a portion of the EB-rich stream 172 and the EB-depleted stream 174 may be treated as a reflux by a separate wall raffinate column 170). Using a separation wall column as the raffinate column further improves EB separation in the PX-deficient stream, which allows more efficient use of the isomerization process.

At least a portion of the EB-rich stream 172 is transported to the isomerization unit 180 and at least a portion of the EB-depleted stream 174 is transported to the isomerization unit 190. In other implementations where the amount of EB in the EB-rich stream is minimal, the EB-rich stream may be purged for fuel blending. The second desorbent stream (176) is optionally recycled to the first and second para-xylene adsorption sections (130, 140) through the adsorbent drum.

Xylene Isomerization

In a preferred embodiment, the EB-rich stream 172 is transported to the isomerization unit 180, which is operated in the vapor phase, and the EB-deficient stream The stream 174 is transported to the isomerization unit 190, which is operated in liquid phase. Minimizing the amount of PX-depleted stream added to the meta-isomerization saves energy and money, which is a requirement for liquid isomerization to vaporize the PX-depleted stream, and the use of hydrogen and hydrogen requiring a hydrogen- Because it requires less energy and funds than the vapor isomerization process.

weather Isomerization

The EB-rich stream 172 is fed to the xylene isomerization unit 180 where the EB-rich stream 172 is fed back to the PX-deficient, EB-rich stream 172 at an equilibrium concentration of the xylene isomer Lt; RTI ID = 0.0 > xylene < / RTI > Generally, dealkylation of two types of vapor-phase isomerization catalysts-EB to produce benzene and ethylene, isomerization of the xylene isomers, and isomerization of the four different C8 aromatics containing EB to their equilibrium concentrations . The catalyst may be used for the vapor-phase isomerization unit 180.

EB Dealkylation

In one embodiment, the EB-rich stream 172 is subjected to xylene isomerization, wherein the EB in the stream can be dealkylated to produce benzene. In this embodiment where ethylbenzene is removed by decomposition / disproportionation, the para-xylene-deficient C ₈ stream is conveniently downstream of the first and first layers comprising at least an ethylbenzene conversion catalyst, And a second layer containing a isomerization catalyst. The layers may be in the same or different reactors. Alternatively, the ethylbenzene conversion catalyst and the xylene isomerization catalyst may be contained in a single layer reactor.

The ethylbenzene conversion catalyst typically has a Constraint Index in the range of 1 to 12, a silica to alumina molar ratio of at least about 5, such as at least about 12, such as at least 20, and at least 5, such as 75 to 5000 Mesopore size zeolite having an alpha value. The restraint index and its determination method are disclosed in U.S. Patent No. 4,016, 218, which is incorporated herein by reference, while the alpha test is described in U.S. Patent No. 3,354,078 and Journal of Catalysis, Vol. 4, p. 527 (1965); Vol. 6, p. 278 (1966); and Vol. 61, p. 395 (1980), each of which is incorporated herein by reference in its entirety. Experimental conditions for the tests used herein are described in Journal of Catalysis, Vol. 61, p. Lt; RTI ID = 0.0 > 538 C < / RTI > The higher alpha values correspond to more active cracking catalysts.

Examples of suitable mesopore size zeolites include ZSM-5 (U.S. Pat. No. 3,702,886 and Re. 29,948); ZSM-11 (U.S. Patent No. 3,709,979); ZSM-12 (U.S. Patent No. 3,832,449); ZSM-22 (U.S. Patent No. 4,556,477); ZSM-23 (U.S. Patent No. 4,076,842); ZSM-35 (U.S. Patent No. 4,016,245); ZSM-48 (U.S. Patent No. 4,397,827); ZSM-57 (U.S. Patent No. 4,046,685); ZSM-58 (U.S. Patent No. 4,417,780); EU-1; And mordenite. The entire contents of which are incorporated herein by reference. Preferred zeolites are ZSM-5, ZSM-12 or EU-1.

The zeolite used in the ethylbenzene conversion catalyst typically has a crystal size of at least 0.2 microns and is capable of reacting at a xylene pressure of 120 DEG C and 4.5 + 0.8 mm of xylene for xylene, which may be para, meta, ortho, Equilibrium sorption capacity of at least 1 gram per 100 grams of measured zeolite and ortho-xylene sorption time (equal temperature and pressure conditions) of more than 1200 minutes to 30% of its equilibrium ortho-xylene sorption capacity. The sorption measurement can be carried out under thermal equilibrium by gravimetric measurement. The sorption test is described in U. S. Patent No. 4,117, 026; 4,159,282; 5,173, 461; And Re. 31,782, each of which is incorporated herein by reference.

The zeolite used in the ethylbenzene conversion catalyst can be self-bonded (no binder) or complexed with an inorganic oxide binder, and the zeolite content can range from about 1 to 99 wt%, more typically from about 10 to about 80 wt% %, For example about 65% zeolite with about 35% binder. When a binder is used, it is preferably non-acidic, such as silica. Procedures for the preparation of silica bound to ZSM-5 are described in U.S. Patent Nos. 4,582,815; 5,053,374; And 5,182,242; And 5,182,242.

In addition, the ethylbenzene conversion catalyst typically comprises from about 0.001 to about 10 weight percent, such as from about 0.05 to about 5 weight percent, such as from about 0.1 to about 2 weight percent, of the hydrogenation / dehydrogenation component. Examples of such components are oxides, hydroxides, sulfides, or Group VIIIA metals (i.e. Pt, Pd, Ir, Rh, Os, Ru, Ni, Co, and Fe) in the form of free metal Metals (i.e., Sn and Pb), Group IIIB elements (e.g., Sn, Pb), metal (i.e., Mn, Tc, and Re), Group VIA Metals (i.e., Ga and In), and Group IB metals (i.e., Cu, Ag, and Au). Precious metals (i.e. Pt, Pd, Ir, Rh, Os and Ru) are the preferred hydrogenation / dehydrogenation components. A combination of catalytic forms of such noble metals or noble metals, for example, a combination of Pt with Sn, may be used. For example, if the component is in the form of an oxide or hydroxide, the metal may be in a reduced valence state. The reduced valence state of such a metal can be achieved in situ in the course of the reaction when a reducing agent, such as hydrogen, is included in the feed to the reaction.

The xylene isomerization catalysts used in this embodiment typically include mesoporous zeolites, for example those with a constraint index of 1 to 12, in particular ZSM-5. The acid value of ZSM-5 of such catalysts, expressed in alpha values, is generally less than about 150, such as less than about 100, for example, from about 5 to about 25. This reduced alpha value can be obtained by steaming. The zeolite typically has a crystallite size of less than 0.2 microns and it is capable of coping with ortho-xylene in an amount of 30% or less of its equilibrium sorption capacity for ortho-xylene at xylene pressures of 120 ° C and 4.5 + 0.8 mm mercury Lt; RTI ID = 0.0 > 50 < / RTI > minutes. The xylene isomerization catalyst may be in a self-bonded form (no binder) or may be complexed with an inorganic oxide binder, such as alumina. In addition, the xylene isomerization catalyst may contain the same hydrogenation / dehydrogenation component as the ethylbenzene conversion catalyst.

Using the catalyst systems described above, ethylbenzene decomposition / disproportionation and xylene isomerization are typically carried out at temperatures of from about 400 ℉ to about 1,000 ((204 캜 to 538 캜), from about 0 to about 1,000 psig (100 to 7,000 kPa) pressure, about 0.1 weight hourly space velocity (WHSV) of about 200 hr-1, and hydrogen of from about 0.1 to about 10, H ₂ to hydrocarbon, is carried out at conditions comprising a molar ratio of the HC. Alternatively, the conversion conditions can be selected from a temperature of about 650 ℉ to about 900 ((343 캜 to 482 캜), a pressure of about 50 to about 400 psig (446 to 2,859 kPa), a WHSV of about 3 to about 50 hr- And a H ₂ to HC mole ratio of from about 0.5 to about 5. The WHSV is based on the weight of the catalyst composition, i.e., the total weight of the active catalyst to which the binder is added, if used.

EB Isomerization

In another embodiment, EB- rich stream (172) produces a stream containing C ₈ aromatics to equilibrium concentrations is applied to the EB isomerization.

Typically, the EB isomerization catalyst is a mesopore size molecular sieve, such as ZSM-5 (U.S. Patent No. 3,702,886 and Re. 29,948), having a constraint index within the approximate range of 1 to 12; ZSM-11 (U.S. Patent No. 3,709,979); ZSM-12 (U.S. Patent No. 3,832,449); ZSM-22 (U.S. Patent No. 4,556,477); ZSM-23 (U.S. Patent No. 4,076,842); ZSM-35 (U.S. Patent No. 4,016,245); ZSM-48 (U.S. Patent No. 4,397,827); ZSM-57 (U.S. Patent No. 4,046,685); And ZSM-58 (U.S. Patent No. 4,417,780). Alternatively, the xylene isomerization catalyst may be MCM-22 (described in U.S. Patent No. 4,954,325); PSH-3 (described in U.S. Patent No. 4,439,409); SSZ-25 (described in U.S. Patent No. 4,826,667); MCM-36 (described in U.S. Patent No. 5,250,277); MCM-49 (described in U.S. Patent No. 5,236,575); And MCM-56 (described in U.S. Patent No. 5,362,697). The molecular sieve may also comprise an EUO structural type molecular sieve, or mordenite, and EU-1 is preferred. A preferred molecular sieve is of the EUO structure type having a Si / Al ratio of about 10-25 as disclosed in U.S. Patent No. 7,893,309. The entire contents of the above references are incorporated herein by reference.

It may be desirable to associate the molecular sieve of the xylene isomerization catalyst with other materials resistant to the temperature of the process and other conditions. Such matrix materials include synthetic or naturally occurring materials as well as inorganic materials such as clay, silica, and / or metal oxides (e.g., titanium oxide or boron oxide). The metal oxide may be naturally occurring or may be in the form of a gelatinous precipitate or gel comprising a mixture of silica and metal oxide. The naturally occurring clays that can be combined with the molecular sieve include those of the montmorillonite and kaolin series, which include sub-bentonite and kaolin, which are commonly referred to as Dixie, McNamee, Georgia, and Florida Clay or the like, wherein the major mineral component is halosite, kaolinite, dicite, nacrite, or anauxite. These clays can be used as raw materials of the original material mined, or can be applied initially to calcination, acid treatment, or chemical modification.

In addition to the materials described above, the molecular sieve may comprise a porous matrix material, such as alumina, zirconia, silica-alumina, silica-magnesia, silica-zirconia, silica-tori, silica- beryllium, silica-titania, aluminum phosphate, titanium phosphate, zirconia Phosphate as well as ternary compounds such as silica-alumina-tori, silica-alumina-zirconia, silica-alumina-magnesia, and silica-magnesia-zirconia. Mixtures of such components may also be used. The matrix may be in the form of a cogel. The relative proportions of the molecular sieve component based on anhydrous water and the inorganic oxide gel matrix can vary widely in molecular sieve content ranging from about 1 to about 99 wt%, more typically from about 10 to about 80 wt%, of the dry composite .

The EB isomerization catalyst also comprises one or more metals from the group VIII of the Periodic Table of the Elements and optionally one or more metals from the group IIIA, IVA, and VIIB. The Group VIII metal present in the catalyst used in the isomerization process of the present invention is preferably selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, preferably noble metals, more preferably palladium and platinum . More preferably, the Group VIII metal is platinum. The metal selected from the optionally present Group IIIA, IVA, and VIIB is selected from gallium, indium, tin, and rhenium, preferably indium, tin, and rhenium.

The conditions used for the EB isomerization process are generally temperatures from 300 to about 500 占 폚, preferably from about 320 to about 450 占 폚, more preferably from about 340 to about 430 占 폚; A partial pressure of hydrogen of from about 0.3 to about 1.5 MPa, preferably from about 0.4 to about 1.2 MPa, more preferably from about 0.7 to about 1.2 MPa; A total pressure of from about 0.45 to about 1.9 MPa, preferably from about 0.6 to about 1.5 MPa; And a weight hourly space velocity (WHSV) of from about 0.25 to about 30 hr ^-1 , preferably from about 1 to about 10 hr ^-1 , and more preferably from about 2 to about 6 hr ^-1 .

The product of the vapor phase xylene isomerization process 180 is a first isomerization stream having a higher PX concentration than the first and second PX-depleted streams 134, The first isomerization stream 182 is recycled to the first para-xylene adsorption section 130 to recover additional PX and the process is repeated to produce the so-called xylene isomerization loop. In an embodiment, the first isomerization stream 182 is passed through a detoluenizing fractionation column 184 to produce at least one C ₇ -isomerization stream and C _{8 +} isomerization stream 186 , Which passes through the first xylene fractionation column 110 before being recycled to the first para-xylene adsorption section 130 to recover additional PX. Preferably, the de-toluene fractionation column 184 comprises two C ₇ -isomerized stream-benzene and / or toluene streams 187 which can be transported to the extraction and hard / branched hydrogen stream 189, ).

Liquid phase Isomerization

The EB-deficient stream 174 is fed to the xylene isomerization unit 190 wherein the EB-deficient stream 174 is a PX-deficient, EB-deficient stream 174, which is again isomerized to the equilibrium concentration of the xylene isomer Is contacted with the xylene isomerization catalyst under at least partially liquid-phase conditions effective to effect conversion. Suitable conditions for the liquid isomerization include temperatures from about 200 DEG C to about 540 DEG C, preferably from about 230 DEG C to about 310 DEG C, more preferably from about 270 DEG C to about 300 DEG C, from about 0 to about 6,895 kPa (g) Preferably a pressure of from about 1,300 kPa (g) to about 3,500 kPa (g), a space per weight hour of from 0.5 to 100 hr ^-1 , preferably from 1 to 20 hr ^-1 , more preferably from 1 to 10 hr ^-1 Speed (WHSV). In general, the conditions will be expected to be a fraction of the C ₈ aromatics, preferably at least 25 wt%, more preferably at least 50 wt%, ideally 100 wt%. Below the solubility limit, low levels of hydrogen can be added to the liquid isomerization process.

Any catalyst capable of isomerizing xylene in the liquid phase may be used in the xylene isomerization unit, but in one embodiment, the catalyst comprises a mesopore size zeolite having a constraint index of 1-12. The constraint index and its method of determination are described in U.S. Patent No. 4,016,218, which is incorporated herein by reference. Specific examples of suitable mesopore size zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM- -11 is particularly preferable, and ZSM-5 is particularly preferable. The acidity of the zeolite expressed by its alpha value is preferably greater than 300, such as greater than 500, or greater than 1000. The alpha test is described in U.S. Patent Nos. 3,354,078; Journal of Catalysis, Vol. 4, p. 527 (1965); Vol. 6, p. 278 (1966); and Vol. 61, p. 395 (1980), each of which is incorporated herein by reference. Experimental conditions of the test used to determine the alpha value quoted herein are described in Journal of Catalysis, Vol. 61, p. Lt; RTI ID = 0.0 > 538 C < / RTI > Preferred catalysts are described in U.S. Patent No. 8,569,559, which is incorporated herein by reference.

The product of the liquid xylene isomerization unit 190 is a second isomerization stream 192 having a higher PX concentration than the first and second PX-depleted streams 134, 144. The second isomerization stream 192 is recycled to the first para-xylene adsorption section 130 or the second para-xylene adsorption section 140 to recover additional PX, and the process is repeated to produce the so-called xylene isomers Create a false loop. To maintain the level of EB in the liquid isomerization loop and prevent the accumulation of EB, the purge stream 194 is fed to the liquid xylene isomerization unit 190 (which may be determined by one skilled in the art) at regular intervals ) And can pass through the xylene isomerization unit 180 where the EB can be converted.

Performing xylene isomerization under liquid phase conditions produces fewer C ₉₊ aromatics than xylene isomerization under vapor phase conditions. Thus, the second isomerization stream 192 can be provided to the second xylene fractionation tower 120 at a higher tray location than the second hydrocarbon feed 194, resulting in more energy savings. In addition, a substantial portion of the second isomerization stream 192 can bypass the second xylene fractionation column 120 and flow directly into the second para-xylene adsorption section 140, Thereby saving energy.

In situations where only a single simulated moving bed unit is used as before, or it is not possible to separate feeds having different levels of EB, the high PX feeds taught in U.S. Patent Nos. 5,750,820 and 8,529,757 and It is advantageous to separate into low PX feeds, the entire contents of which are incorporated herein by reference. A separate wall column can be used to provide a PX feed unit with a high PX feed separately from a low PX feed, and to avoid the use of a separate xylene fractionation column.

In the embodiment shown in Figure 3, the hydrocarbon feed 202 containing the equilibrated xylene is provided to a separating wall xylenes fractionation column 210, and a hydrocarbon feed containing PX in an amount greater than its equilibrium concentration 204 are supplied to the column 210 on the other side of the separation wall. Feed 204 may be further reduced due to its higher concentration of PX or due to its lower concentration of _{C9 +} aromatics found in the toluene methylated or toluene disproportionated product stream which can typically be determined by those skilled in the art Can be supplied at a high tray position. Feed 202 may be any hydrocarbon stream that contains xylene at its equilibrium concentration, i. E., About 22-24 wt% PX, such as a lipomate stream (product stream of the lipomate separation column), a hydrocracked product stream, An aromatic dealkylation stream, a non-selective aromatic alkylation product stream, a methanol to aromatics product stream, a Cyclar ™ process stream, and / or an import stream. Feed 204 may comprise a hydrocarbon stream containing greater than about 22-24 wt% PX, such as a PX selective aromatic alkylation product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, an off-stack PX stream from a PX recovery unit, An intermediate stream from the crystallization unit and / or an import stream.

The separation wall xylene fractionation column 210 separates the feeds 202 and 204 into three stream-balanced PX streams 212, a condensed PX stream 214, and a bottom stream 216 containing _{C9 +} hydrocarbons Separated. Bottoms stream 216, containing a C ₉₊ hydrocarbons are transported to the transalkylation unit may produce additional benzene, toluene and / or xylene. The equilibrium PX stream 212 and the enriched PX stream 214 may be provided as a PX recovery unit 230, preferably a simulated moving bed adsorption unit, which includes a PX-rich product stream 232 and a PX- 234). PX-rich product stream 232 containing PX and desorbent is transported to extraction column 250 for separation, which produces PX stream 252 and desorbent stream 254. The desorbent stream 254 is optionally recycled to the PX recovery unit 230 via the desorbent drum. PX stream 252 is then transported to finishing column 260, which produces purified PX product 262. The toluene stream 264 is recovered as an overhead product from the finishing column 260 and can be recycled back to the PX product process, preferably methanol and / or the selective alkylation of benzene and / or toluene with dimethyl ether. In a conventional simulated moving bed plant structure, the PX-deficient stream comprising MX, OX, EB, and desorbent is transported to a raffinate column; However, in the present method, the separating wall raffinate column replaces the conventional raffinate column.

The PX-depleted stream 234 passes through a separate wall raffinate column 270 that replaces a conventional raffinate column (rectifier column 37 in FIG. 1), which feeds the PX-depleted stream 234 to three Stream-EB-rich stream 272, EB-depleted stream 274, and desorbent stream 276. At least a portion of the EB-rich stream 272 is transported to the isomerization unit 280 which is operated in the vapor phase and at least a portion of the EB-depleted stream 274 is transported to the isomerization unit 290 which is operated in the liquid phase. The desorbent stream 276 may optionally be recycled to the PX recovery unit 230 via the desorbent drum.

The product of the vapor phase xylene isomerization unit 280 is a vapor isomerization stream 282 having a higher PX concentration than the PX-deficient stream 234. The vapor isomerization stream 282 is then recycled to the PX recovery unit 230 to recover additional PX and the process is repeated to produce a so-called xylene isomerization loop. In an embodiment, the vapor isomerization stream 282 is passed through a de-toluene fractionation column 284 to produce at least one C _{7 -isomerization} stream and a C _{8 +} isomerization stream 286, And passes through the separation wall xylene fractionation column 210 before being recycled to the PX recovery unit 230 for recovery. Preferably, the de-toluene fractionation column 284 produces a benzene and / or toluene stream 287 that can be transported to the extraction and hard / hydrogen stream 289, which can be transported with two isomerization stream-fuels do.

The product of the liquid xylene isomerization unit 290 is a liquid isomerization stream 292 having a higher PX concentration than the PX-deficient stream 234. The liquid isomerization stream 292 is then recycled to the PX recovery unit 230 to recover additional PX and the process is repeated to produce the so-called xylene isomerization loop. In order to maintain the level of EB in the liquid isomerization loop and prevent accumulation of EB, a purge stream 294 is fed to the liquid xylene isomerization unit (e. G. 290) and can pass through the xylene isomerization unit 280 where the EB can be converted. The liquid isomerization stream 292 is passed first to the separation wall xylene fractionation column 210 on one side of the separation wall or to the PX recovery unit 230 along with the equilibrated PX stream 212 or the condensed PX stream 214 Can be provided.

Figure 4 shows an embodiment in which a separation wall xylene fractionation column is used in combination with two PX adsorption periods. The corresponding components in FIG. 3 use the same reference numerals in FIG. The hydrocarbon feed 202 containing the equilibrated xylene is provided to the separating wall xylene fractionation column 210 and the hydrocarbon feed 204 containing a greater amount of PX than the equilibrium concentration is fed to the separation wall on the other side of the separation wall Column 210 is provided. The separation wall xylene fractionation column 210 separates the feeds 202 and 204 into three stream-balanced PX streams 212, a condensed PX stream 214, and a bottom stream 216 containing _{C9 +} hydrocarbons Separated.

The balanced PX stream 212 is provided to a first PX collection unit 230, preferably a simulated moving bed adsorption unit, which produces a PX-rich product stream 232 and a PX-depleted stream 234. The concentrated PX stream 214 is provided to a first PX recovery unit 240, preferably a simulated moving bed adsorption unit, which produces a PX-rich product stream 242 and a PX-depleted stream 244. PX-enriched product streams 232 and 242 containing PX and desorbent are transported to extraction column 250 for separation and PX-depleted streams 234 and 244 are passed through separation wall raffinate column 270 do. The remainder of the step is similar to that described above in Fig.

Figure 5 shows an embodiment wherein a crystallizer is used to recover PX from the product of selective alkylation of benzene and / or toluene with methanol and / or dimethyl ether. Corresponding components in Figs. 3 and 4 use the same reference numerals in Fig. The product stream 502 from the selective alkylation of benzene and / or toluene with methanol and / or dimethyl ether in the methylation reactor is provided to the toluene fractionation tower 510, and a new toluene 504 can also be provided thereto . The toluene fractionation column produces an overhead toluene stream 506 that is recycled back to the methylation reactor (not shown) and a C ₈₊ substream 508 provided to the crystallizer 520. The C ₈₊ bottoms stream 508 may contain heavy oxygenates as disclosed in C ₉₊ aromatics such as trimethylbenzene, methylethylbenzene, tetramethylbenzene, naphthalene and U.S. Patent No. 8,907,152, and C ₈₊ Stream 508 may contain up to 10 wt% _{C9 +} aromatics before fractionation at the upstream of crystallizer 520 is required. Optionally, the C ₈₊ bottoms stream 508 may be provided to a separate wall xylene fractionation column 210.

The crystallizer 520 may be operated at about -20 DEG F with propylene refrigeration or at about -80 DEG F with ethylene refrigeration as may be determined by those skilled in the art. Running the crystallizer 520 at about -20 DEG F with propylene refrigeration produces a filtrate 524 having about 30 wt% PX and about 3-4 wt% EB while maintaining the crystallizer 52 at about- (520) produces a filtrate (524) with about 10 wt% PX and about 4-5 wt% EB.

If the filtrate 524 contains less than about 22-24 wt% of PX, such as when ethylene refrigeration is used, then the filtrate 524 is transported to the liquid isomerization unit 290 to make the xylene isomerized . If the filtrate 524 contains more than about 22-24 wt% of PX, e.g., propylene refrigeration is used, then the filtrate 524 is transported to the separation wall xylene fractionation column 210. The remaining steps follow the implementation shown in Figures 3 and 5. The PX recovery section of FIG. 5 shown as PX recovery unit 230 may follow the single PX recovery unit embodiment shown in FIG. 3 or the two section PX recovery unit embodiments shown in FIG.

While the present invention has been described and illustrated with reference to specific embodiments thereof, those skilled in the art will readily appreciate that many modifications and variations may be made thereto without departing from the spirit and scope of the present invention will be.

The trade names used herein are ^TM Symbol or the ® symbol, which may be protected by a trademark, for example, it may be a registered trademark in various jurisdictions. All patents and patent applications, test procedures (e.g., ASTM methods, UL methods, etc.), and other references cited herein, are hereby incorporated by reference in their entirety to the extent that such disclosure is consistent with the present invention and for all jurisdictions . When numerical lower limit values and numerical upper limit values are listed herein, ranges of any lower limit value to arbitrary upper limit value are considered.

Claims (20)

As a production method of para-xylene,
(a) feeding a first hydrocarbon feed comprising xylene and ethylbenzene to a first para-xylene adsorption section;
(b) feeding a second hydrocarbon feed comprising xylene and less ethylbenzene to the second para-xylene adsorption section than the first hydrocarbon feed;
(c) recovering a first para-xylene-rich stream and a first para-xylene-deficient stream from a first hydrocarbon feed in a first para-xylene adsorption section;
(d) recovering a second para-xylene-rich stream and a second para-xylene-deficient stream from a second hydrocarbon feed in a second para-xylene adsorption section;
(e) separating the first and second para-xylene-deficient streams into an ethylbenzene-rich stream and an ethylbenzene-deficient stream in a separate wall raffinate column, wherein the first and second para- Wherein the deficient stream is supplied to the separation wall raffinate column on the opposite side of the separation wall;
(f) at least partially isomerizing at least a portion of the ethylbenzene-rich stream in the gas phase to produce a first isomerization stream having a higher para-xylene concentration than the first and second para-xylene- step;
(g) at least partially isomerizing at least a portion of the ethylbenzene-deficient stream in the liquid phase to produce a second isomerization stream having a higher para-xylene concentration than the first and second para-xylene- step;
(h) recycling at least a portion of the first isomerization stream to a first para-xylene adsorption section; And
(i) recycling at least a portion of the second isomerization stream to a second para-xylene adsorption section
≪ / RTI > 2. The process of claim 1, wherein the first and second para-
Two simulated moving bed adsorption towers; or
One simulated moving bed adsorption tower
≪ / RTI > 3. The process according to claim 1 or 2, wherein the first hydrocarbon feed comprises at least 10.0 wt% ethylbenzene and the second hydrocarbon feed comprises less than 10.0 wt% ethylbenzene. The process according to claim 1, wherein step (f) is carried out under ethylbenzene dealkylation conditions. The process according to claim 1, wherein step (f) is carried out under ethylbenzene isomerization conditions. The process of claim 1 wherein the first hydrocarbon feed comprises a reformate stream, a hydrocracked product stream, a xylene or ethylbenzene (EB) reaction product stream, an aromatic disproportionated stream, an aromatic transalkylation stream, a Cyclar ™ process stream, Or an import stream,
The second hydrocarbon feed is para-selective aromatics alkylation product stream, the non-selective aromatic alkylation product stream, an aromatic disproportionation stream, aromatic transalkylation stream, a methanol / dimethyl ether to aromatic product stream and a synthesis gas to aromatic product stream, C ₂ - (PX) stream from a C ₄ alkaline / alkene to aromatics product stream, an import stream, and / or a para-xylene (PX) recovery unit. 3. The process of claim 1, wherein the second hydrocarbon feed comprises a selective benzene and / or toluene methylated product stream,
Wherein the selective benzene and / or toluene methylated product stream is produced in a fluid bed, a fixed bed, a moving bed or a cyclic bed reactor. The process according to claim 1, further comprising separating one or more C ₇ -isomerization streams from the first isomerization stream in a de-toluene fractionation column prior to step (h). 2. The process of claim 1, wherein step (a) comprises separating the _{C9 +} stream from the first hydrocarbon feed in the first xylene fractionation column prior to feeding the first hydrocarbon feed to the first para- (B) separating the C ₉₊ stream from the second hydrocarbon feed in the second xylene fractionation column prior to feeding the second hydrocarbon feed to the second para-xylene adsorption section ≪ / RTI > 10. The method of claim 9, further comprising providing the first isomerization stream as a first xylene fractionation column prior to step (h). 10. The method of claim 9, further comprising the step of providing a second isomerization stream to a second xylene fractionation column prior to step (i), wherein the second isomerization stream is fed to the second xylene fractionation column at a location higher than the second hydrocarbon feed 2 < / RTI > xylene fractionation column. As a production apparatus of para-xylene,
A first para-xylene adsorption section to produce a first para-xylene-rich stream and a first para-xylene-depleted stream from the first hydrocarbon feed, and a second para-xylene adsorption section from the second hydrocarbon feed to a second para- Xylene-depleted stream, wherein the first and second para-xylene-depleted streams are provided on the opposite side of the separation wall and the ethylbenzene- First and second para-xylene adsorption sections in fluid communication with a separate wall raffinate column separated by an enriched stream and an ethylbenzene-depleted stream;
Xylene-rich stream and producing a first isomerization stream having a higher para-xylene concentration than the first and second para-xylene-depleted streams. ; And
A liquid isomer in fluid communication with a separating wall raffinate column that isomerizes an ethylbenzene-deficient stream and produces a second isomerization stream having a higher para-xylene concentration than the first and second para-xylene- [0040]
≪ / RTI > 13. The process of claim 12, wherein the first and second para-
(1) two simulated moving bed adsorption columns, or
(2) One simulated moving bed adsorption tower
. The method according to claim 12 or 13,
A first xylene fractionation column in fluid communication with a vapor isomerization unit and a first para-xylene adsorption section, said first xylene fractionation column being downstream of the vapor isomerization unit, Rhen fractionation column; And
A second xylene fractionation column in fluid communication with the second para-xylene adsorption section, the second xylene fractionation column being downstream of the liquid isomerization unit and upstream of the second para-xylene adsorption section, Wren fraction column
Further comprising: 15. The method of claim 14, further comprising a de-toluene fractionation column in fluid communication with the vapor-phase isomerization unit and the first xylene fractionation column, wherein the de-toluene fractionation column is downstream of the vapor isomerization unit and comprises a first xylene fractionation column In the upstream of the manufacturing apparatus. delete delete delete delete delete

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