CN107531590B

CN107531590B - Process and apparatus for producing paraxylene

Info

Publication number: CN107531590B
Application number: CN201580079303.XA
Authority: CN
Inventors: R·G·廷格; D·L·菲利德; M·莫利尼耶
Original assignee: ExxonMobil Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 2015-04-30
Filing date: 2015-12-15
Publication date: 2020-11-06
Anticipated expiration: 2035-12-15
Also published as: KR20170133427A; CN107531590A; JP6527960B2; KR101974770B1; JP2018514546A; WO2016175898A1

Abstract

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

Description

Process and apparatus for producing paraxylene

The inventor: robert g.tinger, Dana l.pilipod, Michel Molinier

Cross Reference to Related Applications

This application claims the benefit of provisional application No.62/154,774 filed on 30/4/2015 and EP application No.15171577.8 filed on 11/6/2015.

Technical Field

The present application relates to an improved process and apparatus for producing para-xylene, and in particular to recovering para-xylene from streams having varying amounts of ethylbenzene.

Background

Ethylbenzene (EB), Paraxylene (PX), Orthoxylene (OX) and Metaxylene (MX) are commonly present together in C from chemical plants and refineries₈Aromatic product stream. Although high purity EB is an important feedstock for the production of styrene, for various reasons, all of the high purity EB feedstock used in the production of styrene is produced by the alkylation of benzene with ethylene rather than from C₈Recovered in an aromatics stream. Of the three xylene isomers, PX has the largest commercial market and is used primarily in the manufacture of terephthalic acid and terephthalate esters, which are used in the production of various polymers such as poly (ethylene terephthalate), poly (trimethylene terephthalate), and poly (tetramethylene terephthalate). Although OX and MX can be used as solvents and feedstocks for the manufacture of products such as phthalic anhydride and isophthalic acid, the market demand for OX and MX and their downstream derivatives is much less than the market demand for PX.

Given the higher demand for PX compared to other isomers of PX, for any given C₈There is great commercial interest in aromatic material sources to maximize PX production. However, to achieve the goal of maximizing PX yield, a number of significant technical challenges need to be overcome. For example, four kinds of C₈Aromatic compounds, especially the three xylene isomers, are usually treated with C in a particular plant or refinery₈The aromatics stream is present in a concentration thermodynamically determined for production. Thus, PX production is limited to being originally present at C at most₈The amount in the aromatics stream unless additional process steps are used to increase the amount of PX and/or increase PX recovery efficiency. Various methods are known to increase C₈Concentration of PX in the aromatics stream. These processes generally include recycling the stream between separation steps (where at least a portion of the PX is recovered to produce a PX-depleted stream), and a xylene isomerization step (where the PX content of the PX-depleted stream is returned to equilibrium concentration)。

In a typical aromatic plant, as shown in FIG. 1, C has been removed, typically by treatment in advance by known methods_7-C of species, especially benzene and toluene₈₊A liquid feed of an aromatic feed stream is supplied from line 1 to a xylene re-distillation column 3. Xylene re-distillation column (or more simply fractionating column) evaporates the feed and separates C₈Separation of aromatics into an overhead mixture 5 of xylenes (OX, MX and PX) and Ethylbenzene (EB), and a mixture comprising C₉₊ A bottoms product 61 of aromatic compounds. The overhead mixture typically has a composition of about 40-50% meta-xylene (MX), 15-25% PX, 15-25% OX, and 10-20% EB. Unless otherwise indicated herein, percentages are weight%.

The overhead mixture 5 is then passed to a PX recovery unit 15, which may employ crystallization techniques, adsorption techniques, or membrane separation techniques. These techniques separate PX from its isomers and are capable of producing high purity PX of up to 99.9%, which is withdrawn from unit 15 via conduit 17. In unit 15 is an adsorption separation unit such as Parex^TMOr Eluxyl^TMIn the case of a unit, an extract 17 containing a desorbent, such as para-diethylbenzene (PDEB), needs to be separated from the desired extract PX in a distillation column 19, for example by distillation. This produces a high purity PX stream 27, which may contain light impurities such as toluene, non-aromatics, and water, which are removed in a downstream column (not shown) to further increase PX purity. The desorbent is returned to the PX recovery system 15 via conduit 21.

Raffinate 65, comprising predominantly MX, OX, EB and desorbent, is sent to fractionation column 37, producing MX, OX and EB containing stream 35 and bottoms 63. Desorbent in bottoms 63 is returned to 15. It should be noted that as used herein, the term "raffinate" is used to refer to the portion recovered from the PX recovery unit 15, whether the technique used is adsorptive separation, crystallization, or membrane. Stream 35 is sent to isomerization unit 43 to isomerize MX and OX and optionally EB to an equilibrium mixture of the four isomers. The isomerization unit 43 may be a vapor phase or liquid phase isomerization unit or both. The product of the isomerization unit 43 is sent to C via line 51_7-A distillation column 53 which is to separateThe structured product is separated into a bottoms stream 59 comprising equilibrium xylenes and a product comprising C_7-An overhead stream 47 of aromatics such as benzene and toluene. The bottoms 59 from the distillation column 53 are then sent to the xylene re-distillation column 3, either combined with the feed 1 as shown, or they may be introduced through a separate inlet (not shown).

However, at C₈The presence of EB in the aromatics stream can affect the efficiency of some of the processes described above. Particularly when using an adsorption separation unit for PX recovery, although the adsorbent has a higher affinity for PX, it can also significantly adsorb EB, thereby reducing the ability of the adsorbent to adsorb PX. Therefore, to avoid EB competition for adsorption capacity and increase PX adsorption efficiency, it is desirable to reduce or minimize C sent to the adsorption separation unit₈Amount of EB in the aromatics stream. In addition, liquid phase isomerization converts little or no EB in the PX-depleted stream, so the amount of EB in the xylene loop can accumulate to very high levels. Thus, to maximize the use of liquid phase isomerization, it is also necessary to control the amount of EB in the PX-depleted stream undergoing liquid phase isomerization.

Summary of The Invention

The present invention is an improved process for producing PX, particularly to a process comprising methylating toluene and/or benzene to selectively produce PX, wherein a stream having different amounts of EB is separately processed in the recovery of PX. A first hydrocarbon feed comprising xylenes and EB is provided to a first PX adsorption section, wherein a first PX-rich stream and a first PX-depleted stream are recovered from the feed. A second hydrocarbon feed comprising xylenes and less EB than the first hydrocarbon feed is provided to a second PX adsorption section, wherein a second PX-rich stream and a second PX-depleted stream are recovered from the feed. Separating feeds with different EB content increases the overall efficiency of the adsorption unit for adsorbing PX. The first and second PX adsorption sections may be individual PX adsorption units or individual columns of a single PX adsorption unit. In embodiments, prior to the PX adsorption section, the first hydrocarbon feed may be passed through a first xylene fractionation column to produce a product comprising C₈A first overhead stream of hydrocarbons (which is sent to the first PX adsorption section), and a first overhead stream containing C₉₊A first bottoms stream of hydrocarbons. Similarly, theThe second hydrocarbon feed may be passed through a second xylene fractionation column to produce a product comprising C₈A second overhead stream of hydrocarbons (which is sent to a second PX adsorption section), and a second overhead stream containing C₉₊A second bottoms stream of hydrocarbons.

The first and second PX-depleted streams provided to opposite sides of the dividing wall in the dividing wall raffinate column are then separated into an EB-enriched stream and an EB-depleted stream. At least a portion of the EB-rich stream is then fed to a xylene isomerization unit, where the EB-rich stream is isomerized under at least partial vapor phase conditions to produce a first isomerized stream having a higher PX concentration than the first and second PX-depleted streams. At least a portion of the EB-depleted stream is then fed to a xylene isomerization unit, where the EB-depleted stream is isomerized under at least partial liquid phase conditions to produce a second isomerized stream having a higher PX concentration than the first and second PX-depleted streams. Since vapor phase isomerization is more efficient in converting EB than liquid phase isomerization, but liquid phase isomerization is more energy efficient, the PX-depleted stream is separated based on EB content and each stream is subjected to an appropriate isomerization process to maximize the efficiency and effectiveness of the process. At least a portion of the first isomerized stream is then recycled to the first PX adsorption section or optional first xylene fractionation column, and at least a portion of the second isomerized stream is then recycled to the second PX adsorption section or optional second xylene fractionation column to recover additional PX. The process is then repeated to define a so-called xylene isomerization loop.

The invention also includes an apparatus for carrying out the process of the invention comprising a first PX adsorption section producing a first PX-rich stream and a first PX-depleted stream from a first hydrocarbon feed, and a second PX adsorption section producing a second PX-rich stream and a second PX-depleted stream from a second hydrocarbon feed. The first and second PX adsorption sections are fluidly connected to a dividing wall raffinate column in which the first and second PX-depleted streams are separated into an EB-enriched stream and an EB-depleted stream. Fluidly connected to the divided wall raffinate column are a vapor phase isomerization unit that isomerizes the EB-depleted stream and produces a first isomerized stream having a higher PX concentration than the first and second PX-depleted streams, and a liquid phase isomerization unit that isomerizes the EB-depleted stream and produces a second isomerized stream having a higher PX concentration than the first and second PX-depleted streams. In embodiments, a first xylene fractionation column is fluidly connected downstream of the vapor phase isomerization unit and upstream of the first PX adsorption section, and a second xylene fractionation column is fluidly connected downstream of the liquid phase isomerization unit and upstream of the second PX adsorption section.

Brief description of the drawings

FIG. 1 is a flow diagram of a conventional para-xylene (PX) production and extraction process employing liquid phase xylene isomerization and vapor phase xylene isomerization.

FIG. 2 is a flow chart of one embodiment of the process of the present invention.

FIG. 3 is a flow diagram of a second embodiment of the process of the present invention.

FIG. 4 is a flow diagram of a third embodiment of the process of the present invention.

FIG. 5 is a flow chart of a fourth embodiment of the method of the present invention.

Detailed Description

As used herein, the term "C_n"Hydrocarbon, wherein n is a positive integer, refers to a hydrocarbon having n carbon atoms per molecule. E.g. C₈Aromatic hydrocarbons refer to aromatic hydrocarbons or mixtures of aromatic hydrocarbons having 8 carbon atoms per molecule. The term "C_n+"Hydrocarbon, wherein n is a positive integer, refers to a hydrocarbon having at least n carbon atoms per molecule, and the term" C_n-"Hydrocarbon, wherein n is a positive integer, means a hydrocarbon having no more than n carbon atoms per molecule.

The present invention is an improved process and apparatus for producing PX, particularly to a process involving the methylation of toluene and/or benzene to selectively produce PX, wherein streams having different amounts of ethylbenzene are separately processed to increase the efficiency of PX recovery. Referring to fig. 2, a first hydrocarbon feed 102 comprising xylenes and EB is provided to a first para-xylene adsorption section 130, wherein a first PX-rich stream 132 and a first PX-depleted stream 134 are recovered from the feed. A second hydrocarbon feed 104 comprising xylenes and less EB than the first hydrocarbon feed 102 is provided to a second para-xylene adsorption section 140, wherein a second PX-rich stream 142 and a second PX-depleted stream 144 are recovered from the feed. The first and second PX-depleted streams 134,144 are then separated in a dividing wall raffinate column 170 into an EB-enriched stream 172 and an EB-depleted stream 174. At least a portion of the EB-rich stream 172 is then fed to a xylene isomerization unit 180, where the EB-rich stream 172 is isomerized under at least partial vapor phase conditions to produce a first isomerized stream 182 having a higher PX concentration than the first and second PX-depleted

streams

134, 144. At least a portion of the EB depleted stream 174 is then fed to a xylene isomerization unit 190, where the EB depleted stream 174 is isomerized under at least partial liquid phase conditions to produce a second isomerized stream 192 having a higher PX concentration than the first and second isopx depleted

streams

134, 144. At least a portion of the first isomerized stream 182 is then recycled to the first para-xylene adsorption section 130, and at least a portion of the second isomerized stream 192 is then recycled to the second para-xylene adsorption section 140 to recover additional PX, and the process is repeated to define a so-called xylene isomerization loop.

Hydrocarbon feedstock

The first hydrocarbon feed 102 used in the present process may be any hydrocarbon stream containing xylenes and EB, such as, but not limited to, a reformate stream (product stream of a reformate splitter column), a hydrocracked product stream, a xylene or EB reaction product stream, an aromatics disproportionation stream, an aromatics transalkylation stream, Cyclar^TMA process stream and/or an input stream. 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 xylenes and less EB than the first hydrocarbon feed 102, such as, but not limited to, a PX selective aromatics alkylation product stream, a non-selective (equilibrium PX) aromatics alkylation product stream, an aromatics disproportionation stream, an aromatics transalkylation stream, methanol/dimethyl ether to aromatics product stream, syngas to aromatics product stream, C₂-C₄An alkane/alkene to aromatics product stream, an input stream, and/or an off-spec PX stream from a PX recovery unit. The second feed 104 may containLess than 10.0, 7.5, 5.0, 3.0, 2.0, or 1.0 wt.% EB, as long as it is less than the EB content of the first feed 102.

In one embodiment, the second hydrocarbon feed 104 is the product of the selective alkylation of benzene and/or toluene with methanol and/or dimethyl ether in a methylation reactor. The reactor may be a fluidized bed, a moving bed, a fixed bed, a loop, or any combination thereof. U.S. Pat. Nos. 6,423,879 and 6,504,072 (the entire contents of which are incorporated herein by reference) describe a fluidized bed methylation reactor and use a catalyst comprising a porous crystalline material having a diffusion parameter of about 0.1-15s for 2, 2-dimethylbutane measured at a temperature of 120 ℃ and a 2, 2-dimethylbutane pressure of 60torr (8kPa)^-1. The porous crystalline material may be a medium pore zeolite, such as ZSM-5, which has been sufficiently steamed at a temperature of at least 950 ℃ in the presence of at least one oxide modifier (e.g. comprising phosphorus) to control the reduction in micropore volume of the material during the steaming step. Examples of fixed bed processes and catalysts are described in U.S. Pat. Nos. 7,304,194 and 8,558,046, which disclose steaming a phosphorus modified ZSM-5 catalyst at a temperature of 150-350 ℃ to increase selectivity to para-xylene.

The feed may further comprise recycle stream(s) from the isomerization step(s) and/or various separation steps. The hydrocarbon feed comprises PX, as well as MX, OX, and EB. In addition to xylene and EB, the hydrocarbon feedstock may also contain amounts of other aromatic or even non-aromatic compounds. Examples of such aromatic compounds are C_7-Hydrocarbons, e.g. benzene and toluene, and C₉₊Aromatic compounds such as mesitylene, and the like. These types of feed streams (one or more) are described in "Handbook of Petroleum Refining Processes", ed.k.a.Meyers, McGraw-Hill Book Company, second edition.

Depending on the composition of the first and second hydrocarbon feeds 102,104, the removal of C from the feeds may be performed prior to providing the first and second hydrocarbon feeds 102,104 to the first and second para-xylene adsorption sections 130,140_7-And C₉₊One or more initial separation steps of the hydrocarbons. Generally, the initial separation step may include fractionation, distillation, crystallization, adsorption, reactive separation, membrane separation, extraction, or any combination thereof. In one embodiment, the first hydrocarbon feed 102 is passed through the first xylene fractionation column 110 before being passed through the first para-xylene adsorption section 130. The first xylene fractionation column 110 produces a product containing C₈A first overhead stream 112 of hydrocarbons that is sent to the first para-xylene adsorption section 130, and contains C₉₊A first bottoms stream 114 of hydrocarbons, which may be sent to a transalkylation unit (not shown).

Likewise, the second hydrocarbon feed 104 passes through the second xylene fractionation column 120 before passing through the second para-xylene adsorption section 140. The second xylene fractionation column 120 produces a product stream containing C₈A second overhead stream 122 of hydrocarbons, which is sent to the second para-xylene adsorption section 140, and contains C₉₊A second bottoms stream 124 of hydrocarbons. The second hydrocarbon feed 104 may be subjected to phenol and styrene removal steps, such as those described in U.S. patent publication nos. 2013/0324779 and 2013/0324780, which are incorporated herein by reference in their entirety, either before or after the second xylene fractionation column 120. Second bottoms stream 124 can also be subjected to phenol and styrene removal steps, such as those described in U.S. patent publication nos. 2013/0324779 and 2013/0324780, optionally along with first bottoms stream 114, before being sent to a transalkylation unit (not shown).

Depending on the material balance and equipment requirements, a portion of the first hydrocarbon feed 102 may be combined with the second hydrocarbon feed 104, or vice versa, prior to the xylene fractionator. Likewise, a portion of the overhead stream 112 may be combined with the overhead stream 122, or vice versa, prior to the

PX adsorption section

130, 140.

Para-xylene recovery

In embodiments using a first xylene fractionator, the first hydrocarbon feed 102 or comprises C₈A first overhead stream 112 of hydrocarbons is supplied to a first paraxylene adsorption section 130 to produce a first PX-rich product stream 132 and a first PX-depleted stream 134. In embodiments using a second xylene fractionator, the second hydrocarbon feed 104 isOr comprises C₈A second overhead stream 122 of hydrocarbons is supplied to a second paraxylene adsorption section 140 to produce a second PX-rich product stream 142 and a second PX-depleted stream 144. In one embodiment, the first and second PX-enriched product streams 132,142 comprise at least 10 wt% PX, preferably at least 50 wt% PX, more preferably at least 70 wt% PX, even more preferably at least 80 wt% PX, most preferably at least 90 wt% PX, and ideally at least 95 wt% PX, based on the total weight of the PX-enriched product stream.

The first and second para-xylene adsorption sections 130,140 are preferably simulated moving bed adsorption units, such as PAREX^TMUnits or ELUXYL^TMAnd (4) units. These types of separation unit(s) and their design are described in "Perry's chemical Engineers' Handbook", ed, 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 consists of several sub-beds comprised of two serially connected adsorption columns. 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 having two adsorption columns per section. In another embodiment, the first para-xylene adsorption section 130 and the second para-xylene adsorption section 140 each comprise a column of a single simulated moving bed adsorption unit.

Separately processing feeds with different EB content, e.g., feeds with less than 1.0 wt.% EB and feeds with greater than 1.0 wt.% EB, results in more efficient adsorption of PX. Although the adsorbent has a higher affinity for PX, it can also significantly adsorb EB, thereby reducing the ability of the adsorbent to adsorb PX. Thus, subjecting a feed with a smaller amount of EB, i.e., less than 1.0 wt% EB, to a separate PX adsorption stage minimizes the amount of EB competing for adsorption capacity and increases the efficiency of PX adsorption in the adsorption stage, resulting in more efficient overall adsorption of PX.

In fig. 2, as in a conventional simulated moving bed unit configuration, first and second PX-enriched product streams 132,142 comprising PX and desorbent are sent to an extraction column 150 for separation, which produces a PX stream 152 and a first desorbent stream 154. The first desorbent stream 154 is recycled to the first and second para-xylene adsorption sections 130,140, optionally through a desorbent drum. The PX stream 152 is then sent to a rectification column 160, which produces a purified PX product 162. The toluene stream 164 is recovered as the overhead product of the rectification column 160 and may be recycled back to the PX production process, preferably the selective alkylation of benzene and/or toluene with methanol and/or dimethyl ether. In a conventional simulated moving bed unit configuration, a PX depleted stream comprising MX, OX, EB and desorbent is sent to a raffinate column; however, in the present process, a dividing wall raffinate column replaces the conventional raffinate column, which will be described below.

Dividing wall raffinate column

With continued reference to fig. 2, the first and second PX-depleted streams 134,144 are sent to a dividing wall raffinate column 170, which replaces the conventional raffinate column (fractionator 37 in fig. 1), which separates the first and second PX-depleted streams 134,144 into three streams-an EB-enriched stream 172, an EB-depleted stream 174, and a second desorbent stream 176. As the name implies, the term "dividing wall distillation column" refers to a specific known form of distillation column comprising a dividing wall. The dividing wall vertically bisects a portion of the interior of the distillation column, but does not extend to the top or bottom of the column, thus enabling the column to reflux and reboil similar to a conventional column. The dividing wall provides a fluid impermeable barrier separating the interior of the column. A divided wall column can be configured for multiple processes with the inlet of the column on one side of the divided wall and one or more side draws on the opposite side, or the inlet on both sides of the divided wall column and multiple draws from the top or bottom of the column, or any combination thereof.

In particular embodiments, the dividing wall extends from the top of the column down to a tray with an EB concentration low enough to provide an optimal ratio of low EB and high EB products, which can be determined by one skilled in the art using simulation tools. A first PX depleted stream 134 from the first hydrocarbon feed 102 having a higher EB concentration is provided to the dividing wall raffinate column 170 at one side of the dividing wall, and a second PX depleted stream 144 from the second hydrocarbon feed 104 having a lower EB concentration is provided to the dividing wall raffinate column 170 at the opposite side of the dividing wall. An EB-rich stream 172 and an EB-depleted stream 174 are withdrawn from at or near the top of the column to remove lighter components such as water. Each overhead stream may be processed through a separate overhead product system (not shown), and a portion of EB-rich stream 172 and EB-depleted stream 174 may be returned to dividing wall raffinate column 170 as reflux. The use of a divided wall column as a raffinate column further enhances the separation of EB in the PX-depleted stream, allowing for a more efficient use of the isomerization process.

At least a portion of EB-enriched stream 172 is sent to isomerization unit 180 and at least a portion of EB-depleted stream 174 is sent to isomerization unit 190. In embodiments where the amount of EB in the EB-rich stream is minimal, the EB-rich stream may be purged to the fuel mix. The second desorbent stream 176 is recycled to the first and second para-xylene adsorption sections 130,140, optionally through a desorbent drum.

Xylene isomerization

Since liquid phase isomerization converts little or no EB in the PX-depleted stream, in a preferred embodiment, the EB-enriched stream 172 is sent to an isomerization unit 180 operating in the vapor phase, while the EB-depleted stream 174 is sent to an isomerization unit 190 operating in the liquid phase. Minimizing the amount of PX-depleted stream that is subjected to vapor phase isomerization saves energy and capital because liquid phase isomerization requires less energy and capital than vapor phase isomerization processes due to the vapor phase isomerization process requiring vaporization of the PX-depleted stream and the use of hydrogen, which requires an energy and capital intensive hydrogen recycle loop.

Gas phase isomerization

The EB-rich stream 172 is fed to a xylene isomerization unit 180, wherein the EB-rich stream 172 is contacted with a xylene isomerization catalyst under at least partial vapor phase conditions effective to isomerize the PX-depleted EB-rich stream 172 back to the equilibrium concentration of xylene isomers. There are generally two types of vapor phase isomerization catalysts-one for dealkylating EB to produce benzene and ethylene and isomerizing xylene isomers, and one for four different C' s₈Aromatic compounds (including E)B) Isomerize to its equilibrium concentration. Both catalysts may be used in the vapor phase isomerization unit 180.

EB dealkylation

In one embodiment, EB-rich stream 172 undergoes xylene isomerization, where EBs in the stream can be dealkylated to produce benzene. In this embodiment, when ethylbenzene is removed by cracking/disproportionation, the para-xylene is depleted in C₈The stream is conveniently fed to a multi-bed reactor comprising at least a first bed comprising ethylbenzene conversion catalyst and a second bed downstream of the first bed and comprising xylene isomerization catalyst. The beds may be in the same or different reactors. Alternatively, the ethylbenzene conversion catalyst and the xylene isomerization catalyst may be contained in a single bed reactor.

The ethylbenzene conversion catalyst typically comprises a medium pore size zeolite having a constraint index of from 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 an alpha value of at least 5, such as from 75 to 5000. Constraint indices and methods for their determination are disclosed in U.S. Pat. No.4,016,218, which is incorporated herein by reference, while the alpha test is described in U.S. Pat. No.3,354,078 and Journal of Catalysis, Vol.4, p.527 (1965); volume 6, page 278 (1966); and volume 61, page 395 (1980), the literature on which is described being incorporated herein by reference. The experimental conditions tested as used herein included a constant temperature of 538 ℃ and variable flow rates as described in detail in Journal of Catalysis, volume 61, page 395. Higher alpha values correspond to more active cracking catalysts.

Examples of suitable medium pore size zeolites include ZSM-5 (U.S. Pat. Nos.3,702,886 and Re 29,948); ZSM-11 (U.S. Pat. No.3,709,979); ZSM-12 (U.S. Pat. No.3,832,449); ZSM-22 (U.S. Pat. No.4,556,477); ZSM-23 (U.S. Pat. No.4,076,842); ZSM-35 (U.S. Pat. No.4,016,245); ZSM-48 (U.S. Pat. No.4,397,827); ZSM-57 (U.S. Pat. No.4,046,685); ZSM-58 (U.S. Pat. No.4,417,780); EU-1; and mordenite. The entire contents of the above references 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 micron and exhibits an equilibrium adsorption capacity for xylenes (which may be para, meta, ortho or mixtures thereof) of at least 1 gram per 100 grams of zeolite measured at 120 ℃ and a xylene pressure of 4.5 ± 0.8 mm hg, an ortho-xylene adsorption time (under the same temperature conditions and pressure) of greater than 1200 minutes that is 30% of its equilibrium ortho-xylene adsorption capacity. The adsorption measurement can be performed by gravimetric analysis in thermal equilibrium. Adsorption testing is described in U.S. patent nos. 4,117,026; 4,159,282; 5,173,461, respectively; and re.31,782, each of which is incorporated herein by reference.

The zeolite used in the ethylbenzene conversion catalyst may be self-bound (binder-free) or may be composited with an inorganic oxide binder in an amount ranging from about 1 to about 99% by weight of the dry composite, more typically from about 10 to about 80% by weight of the dry composite, for example about 65% zeolite with about 35% binder. When a binder is used, it is preferably non-acidic, such as silica. Procedures for preparing silica bound ZSM-5 are described in U.S. patent nos. 4,582,815; 5,053,374, respectively; and 5,182,242, which are incorporated herein by reference.

Further, the ethylbenzene conversion catalyst typically comprises from about 0.001 to about 10 wt.%, such as from about 0.05 to about 5 wt.%, for example from about 0.1 to about 2 wt.% of the hydrogenation/dehydrogenation component. Examples of such components include oxides, hydroxides, sulfides or free metals (i.e., zero valent) of group VIIIA metals (i.e., Pt, Pd, Ir, Rh, Os, Ru, Ni, Co and Fe), group VIIA metals (i.e., Mn, Tc and Re), group VIA metals (i.e., Cr, Mo and W), group VB metals (i.e., Sb and Bi), group IVB metals (i.e., Sn and Pb), group IIIB metals (i.e., Ga and In) and group IB metals (i.e., Cu, Ag and Au). Noble metals (i.e., Pt, Pd, Ir, Rh, Os, and Ru) are preferred hydrogenation/dehydrogenation components. Combinations of catalytic forms of such noble or non-noble metals, such as Pt in combination with Sn, may be used. The metal may be in a reduced valence state, for example when the component is in the form of an oxide or hydroxide. The reduced valence state of the metal may be obtained in situ during the reaction when a reducing agent (e.g., hydrogen) is included in the feed to the reaction.

The xylene isomerization catalyst used in this embodiment typically comprises a medium pore size zeolite, such as a zeolite having a constraint index of from 1 to 12, particularly ZSM-5. The catalyst will have an acidity (expressed as a) of ZSM-5, typically less than about 150, for example less than about 100, for example from about 5 to about 25. Such a reduced alpha value can be obtained by steaming. Zeolites typically have a crystal size of less than 0.2 micron and an ortho-xylene adsorption time such that it takes less than 50 minutes to adsorb an amount of ortho-xylene equal to 30% of its equilibrium adsorption capacity of ortho-xylene at 120 ℃ and a xylene pressure of 4.5 ± 0.8 mm hg. The xylene isomerization catalyst can be in self-bound form (no binder) or can be composited with an inorganic oxide binder such as alumina. In addition, the xylene isomerization catalyst may contain the same hydrogenation/dehydrogenation components as the ethylbenzene conversion catalyst.

Using the catalyst system described above, ethylbenzene cracking/disproportionation and xylene isomerization are typically carried out at conditions including a temperature of from about 400 ° F to about 1,000 ° F (204 to 538 ℃), a pressure of from about 0to about 1,000psig (100 to 7,000kPa), from about 0.1 to about 200hr^-1And a Weight Hourly Space Velocity (WHSV) of about 0.1 to about 10 of hydrogen H₂Molar ratio to hydrocarbon HC. Alternatively, the conversion conditions may include a temperature of about 650 ° F to about 900 ° F (343 to 482 ℃), a pressure of about 50 to about 400psig (446 to 2,859kPa), about 3 to about 50hr^-1And a WHSV of about 0.5 to about 5₂Molar ratio to HC. WHSV is based on the weight of the catalyst composition, i.e., the total weight of the active catalyst plus its binder (if used).

EB isomerization

In another embodiment, EB-enriched stream 172 is EB isomerized to produce a stream containing an equilibrium concentration of C₈A stream of aromatic compounds.

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

It may be desirable to combine the molecular sieve of the xylene isomerization catalyst with another material that is resistant to the process temperatures and other conditions. Such matrix materials include synthetic or naturally occurring substances as well as inorganic materials such as clays, 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. Naturally occurring clays which may be composited with the molecular sieve include those of the montmorillonite and kaolin families which include the sub-bentonites and the kaolins commonly referred to as Dixie, McNamee, Georgia and Florida clays, or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the original mined state or first calcined, acid treated or chemically modified.

In addition to the above materials, the molecular sieve may be composited with a porous matrix material such as alumina, zirconia, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, aluminum phosphate, titanium phosphate, zirconium phosphate (zirconia), and ternary compounds such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. Mixtures of these components may also be used. The matrix may be in the form of a cogel. The relative proportions of the molecular sieve component and the inorganic oxide gel matrix on an anhydrous basis can vary widely, with the molecular sieve content ranging from about 1 to about 99 weight percent of the dry composite, more typically from about 10 to about 80 weight percent of the dry composite.

The EB isomerization catalyst also comprises at least one metal selected from the group VIII elements of the periodic table of elements and optionally at least one metal selected from groups IIIA, IVA and VIIB. The group VIII metal present in the catalyst used in the isomerization process of the present invention is selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, preferably from the noble metals, and highly preferably from palladium and platinum. More preferably, the group VIII metal is platinum. The optional metals from groups IIIA, IVA and VIIB are selected from gallium, indium, tin and rhenium, preferably from indium, tin and rhenium.

The conditions used in the EB isomerization process typically include a temperature of from 300 to about 500 ℃, preferably from about 320 to about 450 ℃, more preferably from about 340 to about 430 ℃; a partial pressure of hydrogen of about 0.3 to about 1.5MPa, preferably about 0.4 to about 1.2MPa, more preferably about 0.7 to about 1.2 MPa; total pressure of about 0.45 to about 1.9MPa, preferably about 0.6 to about 1.5 MPa; and a Weight Hourly Space Velocity (WHSV) of from about 0.25 to about 30hr^-1Preferably about 1 to about 10hr^-1More preferably from about 2 to about 6hr^-1。

The product of the vapor phase xylene isomerization process 180 is a first isomerized stream 182 having a higher PX concentration than the first and second PX-depleted

streams

134, 144. The first isomerized stream 182 is then recycled to the first para-xylene adsorption section 130 to recover additional PX, and the process is repeated to produce a so-called xylene isomerization loop. In embodiments, the first isomerized stream 182 is passed through a demethanizer fractionation column 184 to produce at least one C_7-An isomerized stream and C₈₊An isomerized stream 186 that is passed through the first xylene fractionation column 110 and then recycledTo the first para-xylene adsorption section 130 to recover additional PX. Preferably, the debenzolization fractionation column 184 produces two C' s_7-The isomerized stream-may be sent to an extracted benzene and/or toluene stream 187 and a light ends/hydrogen stream 189 that may be sent to fuel.

Liquid phase isomerization

The EB-depleted stream 174 is fed to a xylene isomerization unit 190, wherein the EB-depleted stream 174 is contacted with a xylene isomerization catalyst under at least partial liquid phase conditions effective to isomerize the PX-depleted, EB-depleted stream 174 back to an equilibrium concentration of xylene isomers. Suitable conditions for liquid phase isomerization include a temperature of from about 200 ℃ to about 540 ℃, preferably from about 230 ℃ to about 310 ℃, and more preferably from about 270 ℃ to about 300 ℃, a pressure of from about 0to 6,895kPa (g), preferably from about 1,300kPa (g) to about 3,500kPa (g), and a Weight Hourly Space Velocity (WHSV) of from 0.5 to 100hr^-1Preferably 1 to 20hr^-1And more preferably 1 to 10hr^-1. Typically, the conditions are chosen such that C will be expected₈A portion, preferably at least 25 wt%, and more preferably at least 50 wt%, and ideally 100 wt% of the aromatic compound will be in the liquid phase. Low levels of hydrogen below the solubility limit may be added to the liquid phase isomerization process.

Any catalyst capable of isomerizing xylenes in the liquid phase may be used in the xylene isomerization unit, but in one embodiment the catalyst comprises a medium pore size zeolite having a constraint index of 1 to 12. Constraint indices and methods for their determination are described in U.S. Pat. No.4,016,218, which is incorporated herein by reference. Specific examples of suitable intermediate pore size zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48 and MCM-22, with ZSM-5 and ZSM-11 being particularly preferred, and ZSM-5 being especially preferred. Preferably the zeolite has an acidity (expressed as its alpha value) of greater than 300, for example greater than 500, or greater than 1,000. Testing for α is described in U.S. Pat. nos.3,354,078; journal of Catalysis, volume 4, page 527 (1965); volume 6, page 278 (1966); and volume 61, page 395 (1980), the literature on this description is each incorporated herein by reference. The experimental conditions for the tests used to determine the alpha values cited herein include a constant temperature of 538 ℃ and variable flow rates, as described in detail in Journal of Catalysis, volume 61, page 395. Preferred catalysts are described in U.S. patent No.8,569,559, which is incorporated herein by reference.

The product of the liquid phase xylene isomerization unit 190 is a second isomerized stream 192 having a higher PX concentration than the first and second PX-depleted

streams

134, 144. The second isomerized stream 192 is then 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 a so-called xylene isomerization loop. To control the level of EB in the liquid phase isomerization loop and prevent accumulation of EB, a purge gas stream 194 may be withdrawn at regular intervals (which may be determined by one skilled in the art) from upstream or downstream of the liquid phase xylene isomerization unit 190 and passed to the xylene isomerization unit 180 which may convert EB.

Xylene isomerization under liquid phase conditions produces less C than xylene isomerization under vapor phase conditions₉₊An aromatic compound. Thus, the second isomerized stream 192 may be provided to the second xylene fractionation column 120 at a higher tray location than the second hydrocarbon feed 104, resulting in greater energy savings. In addition, a substantial portion of the second isomerized stream 192 may bypass the second xylene fractionation column 120 and directly enter the second para-xylene adsorption section 140, thereby saving energy by avoiding complete re-fractionation.

Where a single simulated moving bed unit is conventionally used, or where it is not possible to separate feeds with different levels of EB, it is advantageous to separate high PX feeds from low PX feeds, as taught in U.S. patent nos. 5,750,820 and 8,529,757, the entire contents of which are incorporated herein by reference. In order to provide the high PX feed to the PX recovery unit separately from the low PX feed and to avoid the use of a separate xylene fractionation column, a dividing wall column may be used.

In the embodiment shown in fig. 3, hydrocarbon feed 202 containing equilibrium xylenes is provided to dividing wall xylene fractionation column 210, and hydrocarbon feed 204 containing an amount of PX above its equilibrium concentration is provided to column 210 on the other side of the dividing wall. ByAt its higher PX concentration or its lower C₉₊The aromatic concentration (typically seen in toluene methylation or toluene disproportionation product streams), feed 204 may be supplied at a higher tray location, as can be determined by one skilled in the art. The feed 202 may be any hydrocarbon stream containing an equilibrium concentration of xylenes (i.e., about 22-24 wt% PX), such as a reformate stream (product stream of a reformate splitter column), a hydrocracked product stream, a xylene or EB reaction product stream, an aromatics disproportionation stream, an aromatics transalkylation stream, a non-selective aromatics alkylate product stream, a methanol-to-aromatics product stream, a Cyclar^TMA process stream and/or an input stream. The feed 204 may be a hydrocarbon stream containing greater than about 22 to 24 wt% PX, such as a PX selective aromatics alkylation product stream, an aromatics disproportionation stream, an aromatics transalkylation stream, an off-spec PX stream from a PX recovery unit, an intermediate stream from a crystallizer unit, and/or an input stream.

The dividing wall xylene fractionation column 210 separates the feeds 202,204 into three streams-an equilibrium PX stream 212, an enhanced PX stream 214, and a C-containing stream₉₊A bottoms stream 216 of hydrocarbons. May contain C₉₊The bottoms stream 216 of hydrocarbons is sent to a transalkylation unit to produce additional benzene, toluene, and/or xylenes. The equilibrated PX stream 212 and the enhanced PX stream 214 are provided to a PX recovery unit 230, preferably a simulated moving bed adsorption unit, which produces a PX-rich stream 232 and a PX-depleted stream 234. The PX-enriched product stream 232 comprising PX and desorbent is sent to an extraction column 250 for separation, which generates a PX stream 252 and desorbent stream 254. The desorbent stream 254 is recycled to the PX recovery unit 230, optionally via a desorbent drum. The PX stream 252 is then sent to a rectification column 260, which produces a purified PX product 262. The toluene stream 264 is recovered as overhead from rectifier 260 and may be recycled back to the PX production process, preferably the selective alkylation of benzene and/or toluene with methanol and/or dimethyl ether. In a conventional simulated moving bed unit configuration, a PX depleted stream comprising MX, OX, EB and desorbent is sent to a raffinate column; however, in the present process, a divided wall raffinate column is substituted for the common columnA conventional raffinate tower.

The PX-depleted stream 234 is sent to a dividing wall raffinate column 270 (which replaces the conventional raffinate column) (fractionator 37 in fig. 1), which separates the PX-depleted stream 234 into three streams, an EB-enriched stream 272, an EB-depleted stream 274, and a desorbent stream 276. At least a portion of EB-rich stream 272 is sent to isomerization unit 280 operating in the vapor phase and at least a portion of EB-depleted stream 274 is sent to isomerization unit 290 operating in the liquid phase. The desorbent stream 276 may be recycled to the PX recovery unit 230, optionally via a desorbent drum.

The product of the vapor phase xylene isomerization unit 280 is a vapor phase isomerized stream 282 having a higher PX concentration than the PX depleted stream 234. The vapor phase isomerized 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 embodiments, the vapor phase isomerized stream 282 is passed through a demethanizer fractionation column 284 to produce at least one C₇-an isomerized stream and C₈₊An isomerized stream 286, which is passed through the dividing wall xylene fractionation column 210, is then recycled to the PX recovery unit 230 to recover additional PX. Preferably, the debenzolization fractionation column 284 produces two C' s₇An isomerization stream-may be sent to an extracted benzene and/or toluene stream 287, and may be sent to a light ends/hydrogen stream 289 for fuel.

The product of the liquid phase xylene isomerization unit 290 is a liquid phase isomerized stream 292 having a higher PX concentration than the PX depleted stream 234. The liquid phase isomerized stream 292 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. To control the level of EB in the liquid phase isomerization loop and prevent accumulation of EB, a purge gas stream 294 may be withdrawn at regular intervals (which may be determined by one skilled in the art) from upstream or downstream of the liquid phase xylene isomerization unit 290 and passed to the xylene isomerization unit 280 which may convert EB. The liquid phase isomerized stream 292 may be first passed through a dividing wall xylene fractionation column 210 on either side of the dividing wall, or provided to a PX recovery unit 230 with the equilibrium PX stream 212 or enhanced PX stream 214.

Fig. 4 depicts an embodiment in which a divided wall xylene separation column is used in conjunction with two PX adsorption sections. Corresponding elements from fig. 3 are provided with the same reference numerals in fig. 4. The hydrocarbon feed 202 containing equilibrium xylenes is provided to a dividing wall xylene fractionation column 210 and the hydrocarbon feed 204 containing an amount of PX above its equilibrium concentration is provided to the column 210 on the other side of the dividing wall. The dividing wall xylene fractionation column 210 separates the feeds 202,204 into three streams-an equilibrium PX stream 212, an enhanced PX stream 214, and a C-containing stream₉₊A bottoms stream 216 of hydrocarbons.

The equilibrated PX stream 212 is provided to a first PX recovery unit 230, preferably a simulated moving bed adsorption unit, which produces a PX-enriched product stream 232 and a PX-depleted stream 234. The enhanced PX stream 214 is provided to a first PX recovery unit 240, preferably a simulated moving bed adsorption unit, which produces a PX-enriched product stream 242 and a PX-depleted stream 244. A PX-rich product stream 232,242 comprising PX and desorbent is sent to the extraction column 250 for separation, and a PX-depleted stream 234,244 is passed to the dividing wall raffinate column 270. The remaining steps are similar to those described with reference to fig. 3.

Fig. 5 depicts an embodiment of a crystallizer for recovering PX from a selective alkylation product of benzene and/or toluene with methanol and/or dimethyl ether. Corresponding elements from fig. 3 and 4 are given the same reference numerals in fig. 5. 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 a toluene fractionation column 510, which may also be provided with fresh toluene 504. The toluene fractionation column produces an overhead toluene stream 506 (which is recycled back to the methylation reactor (not shown)) and C₈₊A bottoms stream 508 (which is provided to crystallizer 520). C₈₊The bottoms stream 508 may contain C₉₊Aromatic compounds such as trimethylbenzene, methylethylbenzene, tetramethylbenzene, naphthalene and heavy oxygenates, but as taught in U.S. Pat. No.8,907,152, C is necessary before fractionation upstream of crystallizer 520₈₊The bottoms stream 508 may contain up to 10 wt.% C₉₊An aromatic compound. Optionally, C₈₊Bottoms stream 508 can be provided to a dividing wall xylene fractionation column210。

As can be determined by one skilled in the art, the crystallizer 520 can be operated at about-20 ° F with propylene refrigeration or at about-80 ° F with ethylene refrigeration. Crystallizer 520 is operated with propylene refrigeration at about-20 ° F to produce a filtrate 524 having about 30 wt% PX and about 3-4 wt% EB, while crystallizer 520 is operated with ethylene refrigeration at about-80 ° F to produce a filtrate 524 having about 10 wt% PX and about 4-5 wt% EB.

If filtrate 524 contains less than about 22-24 wt% PX, such as when ethylene refrigeration is used, filtrate 524 is sent to liquid phase isomerization unit 290 to isomerize xylenes. If the filtrate 524 contains greater than about 22-24 wt% PX, such as when propylene refrigeration is used, the filtrate 524 is sent to the dividing wall xylene fractionation column 210. The remaining steps follow the embodiments shown in figures 3 and 5. The PX recovery section of fig. 5, depicted as PX recovery unit 230, may follow a single PX recovery unit embodiment as shown in fig. 3 or a two-stage PX recovery unit embodiment as shown in fig. 4.

While the invention has been described and illustrated with reference to specific embodiments, those skilled in the art will appreciate that the invention is applicable without showing changes and modifications without departing from the spirit and scope of the invention.

Commodity name used herein is composed of^TMSymbol or

The notations indicate that the names are to be protected by certain trademark rights, for example, they may be registered trademarks of various jurisdictions. For all jurisdictions in which such incorporation is permitted, all patents and patent applications, test procedures (e.g., ASTM methods, UL methods, etc.), and other documents cited herein are fully incorporated by reference herein as long as such disclosure is not inconsistent with this invention. When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

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 a first hydrocarbon feed in a 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 in a second para-xylene adsorption section;

(e) separating the first and second para-xylene depleted streams in a dividing wall column into an ethylbenzene-enriched stream and an ethylbenzene-depleted stream, wherein the first and second para-xylene depleted streams are provided to the dividing wall column on opposite sides of a 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) at least a portion of the second isomerized stream is recycled to the second para-xylene adsorption section.

2. The process of claim 1, wherein the first and second para-xylene adsorption sections each comprise two simulated moving bed adsorption columns.

3. The process of claim 1, wherein the first and second para-xylene adsorption sections each comprise a simulated moving bed adsorption column.

4. The process of any of claims 1-3, wherein the first hydrocarbon feed comprises at least 10.0 wt.% ethylbenzene and the second hydrocarbon feed comprises less than 10.0 wt.% ethylbenzene.

5. The process of claim 1, wherein step (f) is conducted under ethylbenzene dealkylation conditions.

6. The process of claim 1, wherein step (f) is conducted under ethylbenzene isomerization conditions.

7. The process of claim 1, wherein the first hydrocarbon feed is selected from the group consisting of a reformate stream, a hydrocracking product stream, a xylene or EB reaction product stream, an aromatic disproportionation stream, and/or an aromatic transalkylation stream.

8. The process of claim 1, wherein the second hydrocarbon feed is selected from the group consisting of a para-selective aromatic alkylation product stream, a non-selective aromatic alkylation product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, a methanol/dimethyl ether to aromatic product stream, a syngas to aromatic product stream, C₂-C₄An alkane/alkene to aromatics product stream, an input stream, and/or an off-spec PX stream from a PX recovery unit.

9. The process of claim 1, wherein the second hydrocarbon feed comprises a selective benzene and/or toluene methylation product stream.

10. The process of claim 9, wherein the selective benzene and/or toluene methylation product stream is produced in a fluidized bed, fixed bed, moving bed or circulating bed reactor.

11. The process of claim 1, further comprising separating at least one C from the first isomerized stream in a demethanizer fractionation column prior to step (h)_7-Isomerizing the stream.

12. The process of claim 1, wherein step (a) further comprises separating C from the first hydrocarbon feed in a first xylene fractionation column prior to providing the first hydrocarbon feed to the first para-xylene adsorption section₉₊A stream, and wherein step (b) further comprises separating C from the second hydrocarbon feed in a second xylene fractionation column prior to providing the second hydrocarbon feed to the second para-xylene adsorption section₉₊And (3) feeding.

13. The process of claim 12, further comprising providing the first isomerized stream to a first toluene fractionation column prior to step (h).

14. The process of claim 12, further comprising providing the second isomerized stream to a second xylene fractionation column prior to step (i).

15. The process of claim 14, wherein the second isomerized stream is provided to the second xylene fractionation column at a higher location than the second hydrocarbon feed.

16. An apparatus for producing para-xylene comprising:

a first para-xylene adsorption section producing a first para-xylene enriched stream and a first para-xylene depleted stream from a first hydrocarbon feed, and a second para-xylene adsorption section producing a second para-xylene enriched stream and a second para-xylene depleted stream from a second hydrocarbon feed, the first and second para-xylene adsorption sections being fluidly connected to a dividing wall 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-enriched stream and an ethylbenzene-depleted stream;

a vapor phase isomerization unit fluidly connected to the divided wall column to isomerize the ethylbenzene-rich stream and produce a first isomerized stream having a higher concentration of para-xylene than the first and second para-xylene-depleted streams; and

a liquid phase isomerization unit fluidly connected to the divided wall column to isomerize the ethylbenzene-depleted stream and produce a second isomerized stream having a higher concentration of para-xylene than the first and second para-xylene-depleted streams.

17. The apparatus of claim 16, wherein the first and second para-xylene adsorption sections each comprise two simulated moving bed adsorption columns.

18. The apparatus of claim 16, wherein the first and second para-xylene adsorption sections each comprise a simulated moving bed adsorption column.

19. The apparatus of any one of claims 16-18, further comprising:

a first xylene fractionation column fluidly connected to the gas phase isomerization unit and the first para-xylene adsorption section, wherein the first xylene fractionation column is downstream of the gas phase isomerization unit and upstream of the first para-xylene adsorption section; and

a second xylene fractionation column fluidly connected to the liquid phase isomerization unit and the second para-xylene adsorption section, wherein the second xylene fractionation column is downstream of the liquid phase isomerization unit and upstream of the second para-xylene adsorption section.

20. The apparatus of claim 19, further comprising a de-toluene fractionation column fluidly connected to the vapor isomerization unit and the first xylene fractionation column, wherein the de-toluene fractionation column is downstream of the vapor isomerization unit and upstream of the first xylene fractionation column.