Integrated process and system for producing paraxylene

Abstract

An integrated process for producing paraxylene can include: catalytically reforming a naphtha feed stream to form a reformate stream; separating the reformate stream into a C1-C7 hydrocarbon stream and a C8 + hydrocarbon stream; exposing the C1-C7 hydrocarbon stream to a first solvent in a solvent extraction unit to form a non-aromatic stream and a C6-C7 aromatic stream; separating the C6-C7 aromatic hydrocarbon stream into at least a toluene feed stream; separating the C8 + hydrocarbon stream into a C9 + hydrocarbon stream and a xylene stream; separating the xylene stream in a paraxylene separation unit to form a paraxylene stream and a xylene isomer stream; isomerizing the xylene isomer stream to produce a p-xylene rich stream; and upgrading the toluene feed stream and the C9 + hydrocarbon stream with a hydrogen stream and a mixed transalkylation / dealkylation catalyst in a mixed dealkylation / transalkylation unit to produce a product stream comprising paraxylene.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority to U.S. Non - Provisional Application Serial No. 18 / 183,299, filed Mar. 14, 2023, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] Embodiments of the present disclosure generally relate to refining and upgrading hydrocarbon oils and, in particular, to integrated methods and systems for upgrading a naphtha stream to para - xylene. BACKGROUND OF THE DISCLOSURE

[0004] Aromatic compounds (such as benzene, toluene, and xylenes (BTX)) are fundamental intermediates in many petrochemical industries. Particularly desirable are the xylene isomers of the para - xylene, 1,2 - dimethylbenzene group (ortho - xylene or o - xylene), 1,3 - dimethylbenzene (meta - xylene or m - xylene), or 1,4 - dimethylbenzene (para - xylene or p - xylene). Para - xylene can be used as a raw material for synthesizing commercial plastics in clothing fibers, liquid, and food storage containers, as well as for other uses such as thermoforming in manufacturing. Therefore, methods for converting all hydrocarbon feeds to para - xylene are desirable. SUMMARY OF THE DISCLOSURE

[0005] In a refinery process for generating BTX, a naphtha feed is first sent to a catalytic reformer. The catalytic reformer reforms the naphtha stream into an aromatics - rich reformate stream. Then, the reformate stream is typically separated into a light (carbon content less than 8) stream and a heavy (carbon content greater than 7) stream.

[0006] However, aromatic compounds with a carbon content greater than 9 (C 10+ ) are typically removed from the heavy stream and not used in any way because these streams are considered petroleum coke precursors, which can deactivate catalysts and accumulate as un - converted fractions in recycle streams. Since subsets of hydrocarbon streams and naphtha streams can contain large percentages of these C 10+ fractions, a significant amount of para - xylene and other xylene isomers are not utilized within existing processes. Therefore, methods for converting the C 10+ fractions in a naphtha stream are desirable in order to utilize the entire naphtha stream and maximize the yield of para - xylene.

[0007] Accordingly, an integrated method and system for producing para - xylene from a naphtha feed stream are described herein, while providing the aforementioned benefits. In particular, C 9+ fractions (such as the aforementioned C 10+The (fraction) can be converted using a hybrid transalkylation / dealkylation unit and a catalyst to increase the yields of xylene and para-xylene. In this way, all of the heavy fractions of the naphtha feed stream can be converted to xylene, and in particular para-xylene.

[0008] According to one embodiment herein, an integrated process for producing para-xylene can include: catalytically reforming a naphtha feed stream to form a reformate product stream; separating the reformate product stream into a C1-C7 hydrocarbon stream and a C 8+ hydrocarbon stream; exposing the C1-C7 hydrocarbon stream to a first solvent in a solvent extraction unit to form a non-aromatic hydrocarbon stream and a C6-C7 aromatic hydrocarbon stream; separating the C6-C7 aromatic hydrocarbon stream into at least a toluene feed stream; separating the C 8+ hydrocarbon stream into a C 9+ hydrocarbon stream and a xylene stream comprising ortho-xylene, meta-xylene, and para-xylene; separating the xylene stream in a para-xylene separation unit to form a para-xylene stream and a xylene isomer stream comprising ortho-xylene and meta-xylene; isomerizing the xylene isomer stream with an isomerization catalyst to produce a para-xylene rich stream; and upgrading the toluene feed stream and the C 9+ hydrocarbon stream with a hydrogen stream and a hybrid transalkylation / dealkylation catalyst in a hybrid dealkylation / transalkylation unit to produce a product stream comprising para-xylene, wherein the weight ratio of the toluene feed stream to the C 9+ hydrocarbon stream is from 0.3 to 3.

[0009] According to another embodiment herein, an integrated system for producing para-xylene can include: a catalytic reformer comprising a reforming catalyst; a first separator fluidly connected to the catalytic reformer and downstream of the catalytic reformer; a solvent extraction unit comprising a first solvent, the solvent extraction unit fluidly connected to the first separator and downstream of the first separator; a toluene separation unit fluidly connected to the solvent extraction unit and downstream of the solvent extraction unit; a xylene separation unit fluidly connected to the first separator and downstream of the first separator; a hybrid transalkylation / dealkylation unit comprising a hybrid transalkylation / dealkylation catalyst, the hybrid transalkylation / dealkylation unit fluidly connected to the toluene separation unit and the xylene separation unit and downstream of the toluene separation unit and the xylene separation unit; a para-xylene separation unit fluidly connected to the xylene separation unit and downstream of the xylene separation unit; and a xylene isomerization unit comprising an isomerization catalyst, downstream and upstream of the para-xylene separation unit, the xylene isomerization unit fluidly connected to the para-xylene separation unit.

[0010] Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description, or recognized by practicing the embodiments described herein, including the detailed description which follows and the claims.

[0011] Brief Description of the Drawings

[0012] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, in which:

[0013] Figure 1 (FIG.1) shows a process flow diagram of an exemplary method according to the embodiments described herein;

[0014] Figure 2 shows another process flow diagram of an exemplary method according to the embodiments described herein; and

[0015] Figure 3 shows the comparison results of two pilot plant experiments of an exemplary method according to the embodiments described herein.

[0016] For simplicity of description and illustration of the associated drawings, many valves, temperature sensors, electronic controllers, etc. that are available and well known to those of ordinary skill in the art in the field of certain chemical processing operations are not included. Additionally, the accompanying components that are often included in typical chemical processing operations, such as air supply devices, catalyst hoppers, and flue gas treatment systems, are not depicted. The accompanying components in the hydrotreating unit, such as bleed streams, spent catalyst discharge subsystems, and catalyst replacement subsystems, are also not shown. It should be understood that these components are within the spirit and scope of the embodiments of the present disclosure. However, operating components such as those described in the present disclosure can be added to the embodiments described in the present disclosure.

[0017] It should also be noted that the arrows in the accompanying drawings refer to process flows. However, the arrows can equivalently refer to transfer lines, which can be used to transfer process flows between two or more system components. Additionally, the arrows connected to system components define the inlets or outlets in each given system component. The arrow direction generally corresponds to the main direction of movement of the material of the flow contained within the physical transfer line as indicated by the arrow. Furthermore, arrows that do not connect two or more system components represent product streams leaving the shown system or system inlet streams entering the shown system. The product streams can be further processed in an accompanying chemical processing system or can be commercialized as end products. The system inlet streams can be streams transferred from an accompanying chemical processing system or can be unprocessed feed streams. Some arrows can represent recycle streams, i.e., outlet streams of system components that are recycled back into the system. However, it should be understood that in some embodiments, any represented recycle stream can be replaced by a system inlet stream of the same material, and a portion of the recycle stream can leave the system as a product.

[0018] In addition, the arrows in the accompanying drawings can schematically depict the process steps of transporting a flow from one system component to another. For example, an arrow pointing from one system component to another can represent "delivering" the outlet of the system component to another system component, which can include the contents of the process flow "leaving" or being "removed" from one system component and the contents of the product stream being "introduced" into another system component.

[0019] It should be understood that, according to the embodiments presented in the relevant accompanying drawings, the arrows between two system components can represent an unprocessed flow between the two system components. In other embodiments, the flow indicated by the arrow can have substantially the same composition throughout its transportation between the two system components. Additionally, it should be understood that in an embodiment, the arrow can represent that at least 75 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt% or even 100 wt% of the flow is transported between system components. Thus, in an embodiment, if there is a slip stream, less than all of the flow indicated by the arrow can be transported between system components.

[0020] It should be understood that when two or more lines intersect in the schematic flowcharts of the associated figures, two or more process streams "mix" or "merge". Mixing or merging can also include mixing by directly introducing two streams into the same reactor, separation unit, or other system component. For example, it should be understood that when two streams are depicted as being directly merged before entering a separation unit or reactor, in an embodiment, these streams can equivalently be introduced into the separation unit or reactor and mixed in the reactor. Alternatively, when two streams are depicted as entering a system component independently, in an embodiment, they can be mixed together before entering the system component.

[0021] Reference will now be made in more detail to various embodiments, some of which are illustrated in the accompanying figures. Wherever possible, the same reference numbers will be used throughout the figures to refer to the same or like parts. Detailed Description

[0022] Embodiments herein relate to integrated systems and methods for forming p-xylene from a naphtha stream while providing the aforementioned benefits.

[0023] As used herein, the term "C # hydrocarbon", where "#" is a positive integer, is intended to describe all hydrocarbons having # carbon atoms. In addition, the term "C #+ hydrocarbon" is intended to primarily describe all hydrocarbon molecules having # or more carbon atoms. Thus, the term "C 8+ hydrocarbon" is intended to describe a mixture of hydrocarbons primarily containing 8 or more carbon atoms. Similarly, the term "C #- hydrocarbon" is intended to primarily describe all hydrocarbon molecules having # or fewer carbon atoms. Similarly, the term "C # -C #’ " hydrocarbon is intended to describe a mixture of hydrocarbon molecules primarily containing between # and #' carbon atoms.

[0024] As used herein, "catalyst" refers to any substance that increases the rate of a specific chemical reaction. The catalysts described in the present disclosure can be used to facilitate various reactions, such as but not limited to cracking (including aromatics cracking), demetallization, desulfurization, denitrification, methylation, disproportionation, dealkylation, dearomatization, transalkylation, and isomerization. As used herein, "cracking" generally refers to a chemical reaction in which carbon-carbon bonds are broken. For example, a molecule having carbon-carbon bonds is broken into more than one molecule by the breaking of one or more carbon-carbon bonds, or a compound including a cyclic moiety (such as cycloalkane, cycloalkene, naphthalene, aromatic hydrocarbons, etc.) is converted into a compound that does not include a cyclic moiety or contains fewer cyclic moieties than before cracking.

[0025] As used herein, "catalytic reforming" refers to a conversion process in the petroleum refining and petrochemical industries. The reforming process generally catalytically converts low-octane naphtha distilled from crude oil into higher-octane reformate products that contain aromatic compounds with a large amount of BTX. Generally, four main types of reactions occur during the reforming process: (1) dehydrogenation of naphthenes to aromatics; (2) dehydrogenation cyclization of paraffins to aromatics; (3) isomerization; and (4) hydrocracking.

[0026] As used herein, the term "crude oil" should be understood to represent a mixture of petroleum liquids, gases, or a combination of liquids and gases that includes some impurities that have not undergone significant separation or reaction processes, such as sulfur-containing compounds, nitrogen-containing compounds, and metal compounds. Crude oil is different from the fractions of crude oil. As used herein, crude oil can be crude oil that has been minimally processed to provide a hydrocarbon oil feedstock having a total metal (nickel + vanadium) content of less than 5 parts per million by weight (ppmw) and a Conradson carbon residue of less than 5 wt%. Such minimally processed material can be considered the crude oil described herein.

[0027] It should be understood that "effluent" generally refers to the stream that leaves a system component (such as a separation unit, reactor, or reaction zone) after a specific reaction or separation and generally has a different composition (at least proportionally) from the stream that enters the separation unit, reactor, or reaction zone.

[0028] As used herein, the term "hydrogen / feed ratio", or "hydrogen-to-feed ratio", or "hydrogen-to-feed stream ratio" refers to a standard measure of the volumetric ratio of hydrogen recycled through a reactor relative to the volume of the feed. The hydrogen / feed ratio can be determined by comparing the flow volume of the hydrogen stream and the flow volume of the feed stream entering the reactor.

[0029] As used herein, the term "naphtha" refers to a mixture of substances mainly comprising C5 to C 11 hydrocarbons. "Light naphtha" as used herein is a fraction of naphtha that mainly comprises C5 to C6 hydrocarbons, but it may also include C7 hydrocarbons. As used herein, the term "heavy naphtha" refers to a fraction of naphtha that mainly comprises C7 to C 11 hydrocarbons.

[0030] As used herein, a "reactor" refers to a vessel in which one or more chemical reactions can optionally occur between one or more reactants in the presence of one or more catalysts. For example, a reactor can include a tank or tubular reactor configured to operate as a batch reactor, a continuous stirred tank reactor (CSTR), or a plug flow reactor. Example reactors include packed bed reactors, such as fixed bed reactors and fluidized bed reactors. One or more "reaction zones" can be provided in the reactor. As used herein, a "reaction zone" refers to the region in the reactor where a specific reaction occurs. For example, a packed bed reactor having multiple catalyst beds can have multiple reaction zones, where each reaction zone is defined by the region of each catalyst bed.

[0031] As used herein, any stream referred to as "rich" in some chemical substance contains 50% or more by volume or weight of that chemical substance, such as 50% to 100%, or 50% to 99%, with the remaining 1% including trace amounts of other chemical substances.

[0032] As used herein, a "separation unit" or "separator" refers to any separation device that at least partially separates one or more chemicals mixed in a process stream from each other. For example, a separation unit can selectively separate different chemicals, phases, or materials of different sizes from each other to form one or more chemical fractions. Examples of separation units include, but are not limited to, distillation columns, flash tanks, separation drums, separation vessels, centrifuges, cyclone separators, filtration devices, collectors, scrubbers, expansion devices, membranes, solvent extraction devices, etc. It should be understood that the separation methods described in the present disclosure may not completely separate all of one chemical component from all of another chemical component. It should be understood that the separation methods described in the present disclosure "at least partially" separate different chemical components from each other, and even if not explicitly stated, it should be understood that the separation can include only partial separation. As used herein, one or more chemical components can be "separated" from a process stream to form a new process stream. Generally, a process stream can enter a separation unit and be split or separated into two or more process streams of the desired composition. Additionally, in some separation methods, a "lower boiling fraction" (sometimes referred to as a "light fraction" or "light fraction stream") and a "higher boiling fraction" (sometimes referred to as a "heavy fraction", "heavy hydrocarbon fraction", or "heavy hydrocarbon fraction stream") can leave the separation unit, where, on average, the contents of the lower boiling fraction stream have a lower boiling point than the higher boiling fraction stream. Other streams can be intermediate between the lower boiling fraction and the higher boiling fraction, such as an "intermediate boiling fraction".

[0033] As used throughout this disclosure, "zeolite" can refer to a microporous inorganic material having regular intra-crystalline cavities and molecular-sized channels. Zeolites generally comprise a crystalline structure rather than an amorphous structure (such as amorphous silica) that can be observed in some porous materials. Zeolites generally include a microporous framework, which can be identified by the framework type. The microporous structure of zeolites (e.g., pore size from 0.3 nm to 2 nm) can provide a large surface area and desirable size / shape selectivity, which can be beneficial for catalysis. The zeolites described can include, for example, aluminosilicates, titanosilicates, or pure silicates. In embodiments, the zeolites described can include micropores (present in the microstructure of the zeolite) and additionally include mesopores. As used throughout this disclosure, micropores refer to pores in a structure having a diameter greater than or equal to 0.1 nm and less than or equal to 2 nm, and mesopores refer to pores in a structure having a diameter greater than 2 nm and less than or equal to 50 nm. Unless otherwise described herein, the "pore size" of a material refers to the average pore size, but the material can additionally include micropores and / or mesopores having specific sizes different from the average pore size.

[0034] It should be further understood that a stream can be named according to the components of the stream, and the named components of the stream can be the major components of the stream (e.g., comprising 50 weight percent (wt%), 70 wt%, 90 wt%, 95 wt%, 99 wt%, 99.5 wt% or even 99.9 wt% to 100 wt% of the stream contents). It should also be understood that when a stream containing components is disclosed as being delivered from one system component to another system component, the named components of the stream are disclosed as being delivered from the one component to the other component. As a non-limiting example, reference to delivering a "C2-C4 hydrocarbon stream" from a first system component to a second system component should be understood as equivalently disclosing delivering "C2-C4 hydrocarbons" from the first system component to the second system component, etc.

[0035] First refer to Figure 1, shows an integrated system 100 for the conversion of naphtha feedstock. As used herein, "feedstock" may also be used to refer to "feed stock(s)" or "feed stream(s)". The integrated system 100 may include a catalytic reformer 102, a first separator 104, a solvent extraction unit 106, a toluene separation unit 107, a xylene separation unit 110, a combined alkyl transfer / dealkylation unit 116, a para-xylene separation unit 118, and a xylene isomerization unit 120. The toluene separation unit 107 may further include a benzene column 108 and a toluene column 109, both of which may be atmospheric distillation units, as explained in more detail herein.

[0036] The first separator 104 may be fluidly connected to both the catalytic reformer 102 and the solvent extraction unit 106, downstream of the catalytic reformer 102 and upstream of the solvent extraction unit 106. The benzene column 108 (which may also be regarded as a second separator 108) may be fluidly connected to the solvent extraction unit 106 and the toluene column 109, downstream of the solvent extraction unit 106 and upstream of the toluene column 109. The toluene column 109 (which may also be regarded as a third separator 109) may be fluidly connected to and upstream of the combined alkyl transfer / dealkylation unit 116. The xylene separation unit 110 (which may also be regarded as a fourth separator 110) may be fluidly connected to the first separator 104, the combined alkyl transfer / dealkylation unit 116, and the para-xylene separation unit 118. The xylene separation unit 110 may be downstream of the first separator 104 and upstream of the combined alkyl transfer / dealkylation unit 116 and the para-xylene separation unit 118.

[0037] The para-xylene separation unit 118 (which may also be regarded as a fifth separator) may be fluidly connected to the xylene separation unit 110 and the xylene isomerization unit 120. The para-xylene separation unit 118 may also be downstream of the xylene separation unit 110 and upstream of the xylene isomerization unit 120. The xylene isomerization unit 120 may in turn be upstream of the para-xylene separation unit 118, i.e., the xylene isomerization unit 120 may recycle its product to the para-xylene separation unit 118.

[0038] Still referring to Figure 1 , the catalytic reformer 102 may catalytically reform the naphtha feed stream 2 using a catalytic reforming catalyst to produce a reformate product stream 4. The reformate product stream 4 may be rich in aromatic compounds, particularly C 6+ or C6-C 12Aromatics. As previously described, any stream referred to as "rich" in some chemical substance contains 50% or more by volume or weight of that chemical substance, such as 50% to 100%, or 50% to 99%, with the remaining 1% including trace amounts of other chemical substances.

[0039] The catalytic reformer 102 can operate at an operating temperature in the range of 450°C to 600°C. The catalytic reformer 102 can also operate at an operating pressure in the range of 0.3 MPa to 7 MPa. The catalytic reformer can also operate at a liquid hourly space velocity of -1 from 0.1 h -1 to 5 h.

[0040] The catalytic reforming catalyst can include a support and a noble metal. The support includes silica, alumina, or silica-alumina, and the noble metal includes platinum, ruthenium, or both. The reforming catalyst can also be chlorinated. The first separator 104 can receive the reformate stream 4 and separate it into a C1-C7 hydrocarbon stream 6 and a C 8+ hydrocarbon stream 8.

[0041] The naphtha feed stream 2 can include light naphtha or heavy naphtha. The naphtha feed stream 2 can also include one or more non-hydrocarbon components, such as one or more heavy metals, sulfur compounds, nitrogen compounds, inorganic components, or other non-hydrocarbon compounds. The naphtha feed stream 2 can also be hydrotreated naphtha, hydrotreated light naphtha, or hydrotreated heavy naphtha, such that at least a portion of one or more non-hydrocarbon components can be removed from the naphtha feed stream 2.

[0042] The solvent extraction unit 106 can receive the C1-C7 hydrocarbon stream 6 and the first solvent 5. The solvent extraction unit 106 can thus expose the C1-C7 hydrocarbon stream 6 to the first solvent 5, forming a non-aromatic stream 10 and a C6-C7 aromatic stream 12. The non-aromatic stream 10 can include C1-C7 non-aromatic gases and hydrogen. The C6-C7 aromatic stream 12 can include toluene and benzene and can be rich in toluene, benzene, or a combination thereof.

[0043] In an embodiment, the solvent extraction unit 106 can include one or more extractive distillation columns, one or more absorbent columns, or a combination thereof. The first solvent 5 can include a polar solvent, such as but not limited to sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, N-formylmorpholine, polyethylene glycol, or a combination thereof. The solvent extraction unit 106 can operate at an operating temperature in the range of 160°C to 220°C. The solvent extraction unit 106 can also operate at an operating pressure in the range of 0.5 MPa to 20 MPa.

[0044] The toluene separation unit 107, particularly the benzene column 108, can receive the aromatic hydrocarbon stream 12 and can thus separate the C6-C7 aromatic hydrocarbon stream 12 into a benzene-rich stream 13 and a toluene-rich stream 14. The toluene column 109 can receive the toluene-rich stream 14 and can form a toluene feed stream 15. The toluene separation unit 107 can also send the toluene feed stream 15 to the mixed alkyl transfer / dealkylation unit 116, such as through the toluene column 109. The toluene feed stream 15 can also be combined with an external toluene stream where the toluene within the system is not at a level sufficient to carry out the required alkyl transfer.

[0045] Still referring Figure 1 , the xylene separation unit 110 can receive the C 8+ hydrocarbon stream 8 and can separate it into a C 9+ hydrocarbon stream 18 and a xylene stream 20. The xylene stream can include ortho-xylene, meta-xylene, and para-xylene. The mixed alkyl transfer / dealkylation unit 116 can then receive the C 9+ hydrocarbon stream 18 and the toluene feed stream 15. The mixed alkyl transfer / dealkylation unit 116 can then upgrade the combination of the two streams with the hydrogen stream 22 to a product stream 24, which can include xylene.

[0046] The product stream 24 can also include unreacted C9 and C 10+ hydrocarbon fractions, including but not limited to trimethylbenzene (TMB), methylethylbenzene (MEB), tetramethylbenzene, dimethylethylbenzene, tetraethylbenzene, and unreacted toluene fractions. In an embodiment, the product stream can also include an aromatic fraction produced by the disproportionation of toluene and C 9+ hydrocarbon fractions. In one non-limiting example, toluene and trimethylbenzene can form benzene and tetramethylbenzene, respectively. Without being bound by theory, this may be because the alkyl transfer reaction of trimethylbenzene and toluene and other C 9+ aromatic-toluene pairs is an equilibrium reaction, where at least some disproportionation occurs to the chemicals involved when exposed to the mixed alkyl transfer / dealkylation catalyst.

[0047] Additionally, without being bound by theory, the efficiency of the alkyl transfer reaction to produce xylene from TMB and toluene and other C 9+ aromatic-toluene pairs may be affected by the volume ratio of these substances entering the mixed alkyl transfer / dealkylation unit 116, at least because the alkyl transfer reaction of TMB / toluene is an equilibrium reaction, as described above. Therefore, in the embodiments herein, it is contemplated that the ratio of the toluene feed stream 15 to the C 9+ hydrocarbon stream 18 can be from 0.3 to 3. At ratios less than 0.3, there may be insufficient toluene within the mixed alkyl transfer / dealkylation unit 116, and thus C 9+Hydrocarbon-based, less energy-efficient disproportionation reactions may dominate over transalkylation reactions in the mixed transalkylation / dealkylation unit 116. At ratios higher than 3, the opposite may be the case, where an overabundance of toluene undergoes less energy-efficient toluene disproportionation. Without being limited by theory, the transalkylation of TMB and toluene can be considered more energy-efficient because all the products of the reaction are xylenes, rather than xylenes and non-xylene aromatics.

[0048] The mixed transalkylation / dealkylation catalyst may comprise a solid zeolite composite mixed with an alumina binder. The solid zeolite composite may have macroporous mordenite and mesoporous ZSM-5. In the solid zeolite composite, the weight ratio of macroporous mordenite to mesoporous ZSM-5 may be from 1:1 to 5:1. Also as used herein, a "macroporous" zeolite is defined as a zeolite having 12-membered rings forming the zeolite framework. Also as used herein, a "mesoporous" zeolite is defined as a zeolite having 10-membered rings forming the zeolite framework.

[0049] In addition, the mixed transalkylation / dealkylation catalyst may have a mesostructure comprising at least one disordered mesophase and at least one ordered mesophase. The ordered mesophase may be a hexagonal mesophase, and the disordered mesophase may include a hexagonal mesophase. As used herein, an "ordered mesophase" may refer to a crystalline zeolite with uniformly arranged mesopores, where the "mesopores" have an average pore diameter between 2 nanometers and 50 nanometers. As used herein, a "disordered mesophase" means a non-uniform arrangement of pores, where the mesopores have an average pore diameter between 2 nanometers and 50 nanometers. The mixed transalkylation / dealkylation catalyst may also include an active metal. The active metal may be impregnated on the mixed transalkylation / dealkylation catalyst. The active metal may be selected from the group consisting of molybdenum, chromium, platinum, nickel, palladium, rhenium, or combinations thereof.

[0050] The mixed transalkylation / dealkylation unit 116 may operate at an operating temperature in the range of 300 °C to 480 °C. The mixed transalkylation / dealkylation unit 116 may also operate at an operating pressure in the range of 1 MPa to 3 MPa. The mixed transalkylation / dealkylation unit 116 may also operate at a liquid hourly space velocity of 0.1 hr -1 to 10 hr -1 . The mixed transalkylation / dealkylation unit 116 may also operate at a ratio of hydrogen to the feed streams (stream 15 and stream 18) of 1 to 6.

[0051] Still referring to Figure 1, the system 100 may further include a sixth separator 122. The sixth separator 122 may be fluidly connected to the mixed alkylation / transalkylation unit 116 and downstream thereof. The sixth separator 122 may also be fluidly connected to the xylene separator 110, the benzene column 108, and the para-xylene separation unit 118 and upstream thereof. The sixth separator 122 may receive the product stream 24 and may separate the product stream 24 into at least an additional non-aromatic stream 10, an additional C6-C7 aromatic stream 12, an additional xylene stream 20, and an unreacted C 9+ hydrocarbon stream 26. The unreacted C 9+ hydrocarbon stream 26 may particularly include an unreacted C9 hydrocarbon fraction stream and an unreacted C 10+ hydrocarbon fraction stream. In an embodiment, the sixth separator 122 may also send the unreacted C 9+ hydrocarbon stream 26 to be combined with the C 9+ hydrocarbon stream 26. Thus, the unreacted C 9+ hydrocarbon stream 26 may then be recycled in the mixed transalkylation / alkylation unit 116 for upgrading to form an additional product stream 24.

[0052] As previously discussed, in some refinery processes for producing BTX, C 10+ aromatics are typically removed from the system, such as to a fuel oil pool. One reason for this may be that the conversion efficiency of C 10+ aromatics is lower than that of C9 aromatics, resulting in the progressive accumulation of these fractions in the feed during subsequent runs. Additionally, it is known that C 10+ aromatics may deactivate the catalyst (such as poisoning or fouling), which increasingly becomes a problem as the percentage of the feed containing C 10+ aromatics increases. However, as further explained in detail in the examples below, the mixed alkylation-transalkylation unit 116 and the mixed alkylation-transalkylation catalyst exhibit an unexpected ability to convert C 10+ hydrocarbon fractions, thereby reducing the accumulation of such fractions in the mixed alkylation-transalkylation unit 116 during subsequent runs. Thus, the C 10+ hydrocarbon fraction may be recycled to the mixed alkylation-transalkylation unit 116, which may result in the use of all hydrocarbon feeds for the production of BTX (and particularly para-xylene).

[0053] Without being bound by theory, it is contemplated that the unexpected ability of the mixed alkylation-transalkylation catalyst may be at least partially attributed to its partial transalkylation function. In particular, including a transalkylation function may be operable to remove heavy aromatic fractions (such as C 10+Aromatics (diethylbenzene and / or tetramethylbenzene, methylpropylbenzene, trimethylethylbenzene, etc.)) are dealkylated to form lighter aromatic fractions (such as TMB, xylene, and toluene). As previously mentioned, these lighter aromatic fractions can effectively undergo transalkylation reactions with the toluene feed stream 15 to form xylene. Similarly, considering that the dealkylation function of the mixed transalkylation-dealkylation catalyst can, to a lesser extent, remove the alkyl groups that act as bridges for bi-aromatics and poly-aromatics (such as C 12+ aromatic fractions).

[0054] Still referring Figure 1 to, the para-xylene separation unit 118 can receive the xylene stream 20 and an additional xylene stream 20. The para-xylene separation unit 118 can also be operated to separate the xylene stream 20 into a para-xylene stream 29 and a xylene isomer stream 30, for example, by using adsorption, crystallization, or a combination of both, as can be understood in the art. The xylene isomer stream 30 can include meta-xylene isomers and ortho-xylene isomers. In an embodiment, the para-xylene separation unit 118 can include one or more absorption towers, one or more crystallization columns, or a combination thereof.

[0055] The xylene isomerization unit 120 can receive the xylene isomer stream 30 and isomerize it with an isomerization catalyst to form a para-xylene-rich stream 31, which can be recycled back to the para-xylene separation unit 118 to further extract the para-xylene stream 29 and the xylene isomer stream 30. The xylene isomerization unit 120 can be operated at an operating temperature in the range of 200°C to 540°C. The xylene isomerization unit 120 can also be operated at an operating pressure in the range of 1 MPa to 5 MPa. The xylene isomerization unit 120 can also be operated at a liquid hourly space velocity of 0.1 hr -1 to 20 hr -1 .

[0056] The isomerization catalyst can include a mesoporous zeolite-based catalyst. The isomerization catalyst can also include a support and an active metal. The support can be selected from the group consisting of mesoporous mordenite, mesoporous ZSM-5 zeolite, or beta zeolite. The active metal can be selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or a combination thereof. The isomerization catalyst can include 1 wt% to 10 wt% mordenite, by weight of the catalyst, such as approximately 4 wt% mordenite. The isomerization catalyst can be similar to the disproportionation catalyst.

[0057] Now referring Figure 2 to, the system 200 can be similar to the system 100 in some or all aspects and can further include one or more additional processing units or separators, as further explained in detail below. For example, and as Figure 2As shown, system 100 may further include a toluene disproportionation unit 124, which includes a disproportionation catalyst. The toluene disproportionation unit may be fluidly connected to, and downstream of, the toluene separation unit 107 (specifically, the toluene column 109), and may be configured to receive at least a portion of the toluene feed stream 15 as a toluene disproportionation feed stream 16.

[0058] Without being bound by theory, a toluene disproportionation unit 124 may be included in the system to account for excess toluene that is a feed to the combined alkyl transfer / dealkylation unit 116. For example, and in an embodiment, the weight ratio of the toluene feed stream 15 to the C 9+ hydrocarbon stream 18 may be from 0.3 to 3.0. However, as this ratio continues to increase, particularly beyond 1.5, the desired TMB and the alkyl transfer rate of the toluene to xylene and other C 9+ arene / xylene pair may decline, and the proportion of toluene disproportionation to xylene and benzene may increase. Accordingly, a toluene disproportionation unit 124 may be included in the system to relieve at least a portion of the burden on the combined alkyl transfer / dealkylation unit 116 and reduce the ratio within the combined alkyl transfer / dealkylation unit 116 to an optimized level.

[0059] The disproportionation catalyst may include a mesoporous zeolite-based catalyst. The disproportionation catalyst may also include a support and an active metal. The support may be selected from the group consisting of mesoporous mordenite, mesoporous ZSM-5 zeolite, or both. The active metal may be selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or combinations thereof. The disproportionation catalyst may include from 1 wt% to 10 wt% mordenite, by weight of the catalyst, such as about 4 wt% mordenite. The disproportionation catalyst may be similar to the isomerization catalyst.

[0060] The toluene disproportionation unit 124 may operate at an operating temperature in the range of 200°C to 540°C. The toluene disproportionation unit 124 may also operate at an operating pressure in the range of 1 MPa to 5 MPa. The toluene disproportionation unit 124 may also operate at a liquid hourly space velocity of 1 hr -1 to 20 hr -1 .

[0061] Now referring Figures 1 - 2 , embodiments herein also include an integrated process for producing para-xylene. The process may include any one of the integrated systems 100-200 described above. The process may include: catalytically reforming a naphtha feed stream 2 to form a reformate product stream 4, separating the reformate product stream 4 into a C1-C7 hydrocarbon stream 6 and a C 8+ hydrocarbon stream 8, exposing the C1-C7 hydrocarbon stream 6 to a first solvent 5 in a solvent extraction unit 106 to form a non-aromatic stream 10 and a C6-C7 aromatic stream 12, and separating the C6-C7 aromatic stream 12 to form at least a toluene feed stream 15.

[0062] The method may further include separating C 8+ hydrocarbon stream 8 into C 9+ hydrocarbon stream 18 and xylene stream 20, separating xylene stream 20 in para-xylene separation unit 118 to form para-xylene stream 29 and xylene isomer stream 30, and isomerizing xylene isomer stream 30 with an isomerization catalyst to produce para-xylene rich stream 31. The method may also include upgrading toluene feed stream 15 and C 9+ hydrocarbon stream 18 in mixed alkyl transfer / dealkylation unit 116 with hydrogen stream 22 and a mixed alkyl transfer / dealkylation catalyst to produce product stream 24. In an embodiment, the ratio of toluene feed stream 15 to C 9+ hydrocarbon stream 18 may be from 0.3 to 3.

[0063] As mentioned previously, the additional streams produced in mixed alkyl transfer / dealkylation unit 116 may be used to increase the production of para-xylene, such as by being recycled in one or more units of systems 100-200 described herein. For example, and in an embodiment, the method may further include: combining additional non-aromatic stream 10 with non-aromatic stream 10; combining additional C6-C7 aromatic stream 12 with C6-C7 aromatic stream 12; combining additional xylene stream 20 and para-xylene rich stream 31 with xylene stream 20; and combining unreacted C9 hydrocarbon stream and unreacted C 10+ hydrocarbon distillate stream with C 9+ hydrocarbon stream 18.

[0064] As Figure 1 and Figure 2 shown, forming toluene feed stream 15 (such as in toluene separation unit 107) may further include separating C6-C7 aromatic stream 12 into benzene rich stream 13 and toluene rich stream 14 (such as in benzene column 108). Forming toluene feed stream 15 may also include separating toluene feed stream 15 from toluene rich stream 14 (such as in toluene column 109). As Figure 2 shown, the method may also include sending at least a portion of toluene feed stream 15 to toluene disproportionation unit 124 having a disproportionation catalyst to form additional benzene rich stream 13 and additional xylene stream 20, such as when the ratio of toluene feed stream 15 to C 9+ hydrocarbon stream 18 is greater than 1.5 to 3.

[0065] Still referring to Figure 1 and Figure 2 , the method may also include upgrading unreacted C9 hydrocarbon stream and unreacted C 9+ hydrocarbon distillate stream with C 10+ hydrocarbon stream 18 in mixed alkyl transfer / dealkylation unit 116 to form additional product stream 24.

[0066] Examples

[0067] Various embodiments of methods and systems for converting a naphtha feed stream to para-xylene will be further illustrated by the following examples. These examples are illustrative in nature and should not be construed as limiting the subject matter of the present disclosure.

[0068] According to those discussed previously and Figure 1 shown, two pilot plant experiments were conducted. Example 1 is a baseline case where the unconverted C 9+ hydrocarbon fraction 26 is not recycled, i.e., single-pass. Example 2 includes recycling the unconverted C 9+ hydrocarbon fraction 26 to show the function of the mixed alkylation / transalkylation unit 116 in converting the C 10+ aromatic hydrocarbon fraction in subsequent runs. The results of the two examples are shown in Table 1 below.

[0069] Table 1: Pilot Plant Experiment Results

[0070] Component Example 1 Example 2 <![CDATA[New C 9+ Feed, kg / hr]]> 5.04 3.04 New Toluene Feed, kg / hr 3.36 3.36 Recycle Stream None <![CDATA[C 9+ > Recycle Feed, kg / hr 0 2 <![CDATA[Hydrogen, m 3 / hr]]> 6.9 6.9

[0071] Feed Composition Example 1 Example 2 Toluene, wt% 39.66 39.92 <![CDATA[C8, wt%]]> 1.23 2.11 MEB, wt% 9.82 7.38 TMB, wt% 38.73 38.05 <![CDATA[C9 Aromatics, wt%]]> 51.42 48.57 <![CDATA[C 10+ Aromatic hydrocarbons, wt%]]> 7.41 9.1 Product Distribution Example 1 Example 2 <![CDATA[C5 and below, wt%]]> 5.19 4.27 BTX, wt% 62.32 61.83 Benzene, wt% 3.42 3.04 Toluene, wt% 24.89 23.80 Xylene, wt% 34.01 34.98 MEB, wt% 2.55 2.03 TMB, wt% 23.14 24.54 <![CDATA[C9 Aromatics, wt%]]> 26.46 27.22 <![CDATA[C 10+ Aromatic hydrocarbons, wt%]]> 5.31 6.14 Conversion Rate Example 1 Example 2 Toluene Conversion Rate, % 37.26 40.38 MEB Conversion Rate, % 74.01 72.74 TMB Conversion Rate, % 40.24 35.48 <![CDATA[C9 conversion rate, %]]> 48.54 43.95 <![CDATA[C 10+ Conversion rate, %]]> 28.32 32.24 Total Conversion Rate, % 42.47 41.42

[0072] As shown in Table 1 above, after recycling the unconverted C 9+ hydrocarbon fraction 26, the C 10+ aromatic hydrocarbon conversion increased by approximately 4%, indicating that the mixed alkylation / transalkylation unit 116 and the mixed alkylation / transalkylation catalyst are capable of dealkylating the unconverted C 10+ hydrocarbon fraction in further runs. The unconverted C 10+ hydrocarbon fraction in the product stream was monitored by gas chromatographic analysis of product stream samples taken every three to six hours. This gas chromatographic analysis confirmed that there was no sign of an increase in the accumulation of the C 10+ hydrocarbon fraction compared to Example 1.

[0073] Furthermore, as shown in Table 1 and Figure 3 below, between the baseline case (Example 1) and subsequent runs (Example 2), the total BTX yield remained relatively constant. However, the decrease in the yields of benzene and toluene was associated with an increase in the yield of the desired product (xylene). Without being limited by theory, this may also tend to indicate that the alkylation and dealkylation functions of the catalyst can act synergistically, i.e., there may be a synergistic effect. In particular, the dealkylation function of the catalyst can operate to selectively dealkylate the C 10+ aromatic hydrocarbon fraction to C 9+An aromatic fraction, such as TMB. The transalkylation function of the catalyst can then selectively transalkylate toluene and in-situ generate TMB, for example, producing xylene in a preferred transalkylation reaction. Additionally considered, the dealkylation function can also have toluene and mixed xylenes as products, which also helps to increase the xylene yield.

[0074] The present disclosure may include one or more aspects. According to a first aspect, alone or in combination with any other aspect, an integrated method for producing para-xylene comprises: catalytically reforming a naphtha feed stream to form a reformate product stream; separating the reformate product stream into a C1-C7 hydrocarbon stream and a C 8+ hydrocarbon stream; exposing the C1-C7 hydrocarbon stream to a first solvent in a solvent extraction unit to form a non-aromatic hydrocarbon stream and a C6-C7 aromatic hydrocarbon stream; separating the C6-C7 aromatic hydrocarbon stream into at least a toluene feed stream; separating the C 8+ hydrocarbon stream into a C 9+ hydrocarbon stream and a xylene stream comprising ortho-xylene, meta-xylene, and para-xylene; separating the xylene stream in a para-xylene separation unit to form a para-xylene stream and a xylene isomer stream comprising ortho-xylene and meta-xylene; isomerizing the xylene isomer stream with an isomerization catalyst to produce a para-xylene-rich stream; and upgrading the toluene feed stream and the C 9+ hydrocarbon stream with a hydrogen stream and a mixed transalkylation / dealkylation catalyst in a mixed dealkylation / transalkylation unit to produce a product stream comprising para-xylene, wherein the weight ratio of the toluene feed stream to the C 9+ hydrocarbon stream is from 0.3 to 3.

[0075] According to a second aspect, alone or in combination with any other aspect, the method may further comprise separating the product stream into an additional non-aromatic hydrocarbon stream, an additional C6-C7 aromatic hydrocarbon stream, an un-converted C9 hydrocarbon fraction stream, an un-converted C 10+ hydrocarbon fraction stream, and an additional xylene stream.

[0076] According to a third aspect, alone or in combination with any other aspect, the method may further comprise: combining the un-converted C9 hydrocarbon stream and the un-converted C 10+ hydrocarbon fraction stream with the C 9+ hydrocarbon stream; and upgrading the un-converted C9 hydrocarbon fraction stream and the un-converted C 10+ hydrocarbon fraction stream in a mixed dealkylation / transalkylation unit to form an additional product stream.

[0077] According to a fourth aspect, alone or in combination with any other aspect, the method may further comprise: combining the additional C6-C7 aromatic hydrocarbon stream and the C6-C7 aromatic hydrocarbon stream; and separating the combined C6-C7 aromatic hydrocarbon stream into an additional toluene feed stream and a benzene-rich stream.

[0078] According to a fifth aspect, alone or in combination with any other aspect, the method may further comprise: combining an additional non-aromatic stream with the non-aromatic stream; and combining an additional xylene stream and a para-xylene-rich stream with the xylene stream.

[0079] According to a sixth aspect, alone or in combination with any other aspect, the mixed alkyltransalkylation / dealkylation catalyst comprises a solid zeolite composite and an active metal; the solid zeolite composite comprises macroporous mordenite and mesoporous ZSM-5, wherein the weight ratio of macroporous mordenite to mesoporous ZSM-5 is from 1:1 to 5:1; and the active metal is selected from the group consisting of molybdenum, chromium, platinum, nickel, palladium, rhenium, or combinations thereof.

[0080] According to a seventh aspect, alone or in combination with any other aspect, the active metal of the mixed alkyltransalkylation / dealkylation catalyst is molybdenum.

[0081] According to an eighth aspect, alone or in combination with any other aspect, the mixed alkyltransalkylation / dealkylation catalyst has a mesostructure comprising at least one disordered mesophase and at least one ordered mesophase.

[0082] According to a ninth aspect, alone or in combination with any other aspect, the ratio of the toluene feed stream to the C 9+ hydrocarbon stream is greater than 1.5 to 3; and the method further comprises sending at least a portion of the toluene feed stream to a disproportionation unit having a disproportionation catalyst to form an additional xylene stream and a benzene-rich stream.

[0083] According to a tenth aspect, alone or in combination with any other aspect, the disproportionation catalyst comprises: a support selected from the group consisting of mesoporous ZSM-5 zeolite and mesoporous mordenite; and an active metal selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or combinations thereof.

[0084] According to an eleventh aspect, alone or in combination with any other aspect, the reforming catalyst comprises a support and a noble metal, the support comprises silica, alumina, or silica-alumina, and the noble metal comprises platinum, ruthenium, or both; the first solvent comprises sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, N-formylmorpholine, polyethylene glycol, or combinations thereof; and the isomerization catalyst comprises: a support selected from the group consisting of fluorinated zeolite, mesoporous ZSM-5 zeolite, and mesoporous mordenite; and an active metal selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or combinations thereof.

[0085] According to a twelfth aspect, alone or in combination with any other aspect, the isomerization and disproportionation occur at a temperature of 200 °C to 540 °C, a pressure of 1 MPa to 5 MPa, and a liquid hourly space velocity of 0.1 hr -1 to 20 hr -1 of the liquid hourly space velocity.

[0086] According to a thirteenth aspect, alone or in combination with any other aspect, the mixed alkyl transfer / dealkylation occurs at a temperature of 300 °C to 480 °C, a pressure of 1 MPa to 3 MPa, a liquid hourly space velocity of 0.1 hr -1 to 10 hr -1 and a hydrogen-to-feed ratio of 1 to 6.

[0087] According to a fourteenth aspect, alone or in combination with any other aspect, an integrated system for producing p-xylene may include: a catalytic reformer including a reforming catalyst; a first separator fluidly connected to and downstream of the catalytic reformer; a solvent extraction unit including a first solvent, the solvent extraction unit fluidly connected to and downstream of the first separator; a toluene separation unit fluidly connected to and downstream of the solvent extraction unit; a xylene separation unit fluidly connected to and downstream of the first separator; a mixed alkyl transfer / dealkylation unit including a mixed alkyl transfer / dealkylation catalyst, the mixed alkyl transfer / dealkylation unit fluidly connected to and downstream of the toluene separation unit and the xylene separation unit; a p-xylene separation unit fluidly connected to and downstream of the xylene separation unit; and a xylene isomerization unit including an isomerization catalyst, downstream and upstream of the p-xylene separation unit, the xylene isomerization unit fluidly connected to the p-xylene separation unit.

[0088] According to a fifteenth aspect, alone or in combination with any other aspect, the toluene separation unit includes: a benzene column fluidly connected to and downstream of the solvent extraction unit; and a toluene column downstream of the benzene column and upstream of the mixed alkyl transfer / dealkylation unit, the toluene column fluidly connected to the benzene column and the mixed alkyl transfer / dealkylation unit.

[0089] According to a sixteenth aspect, alone or in combination with any other aspect, the system further includes: a sixth separator fluidly connected to the mixed alkyl transfer / dealkylation unit, the benzene column, the xylene separation unit, and the p-xylene separation unit, wherein the sixth separator is downstream of the mixed alkyl transfer / dealkylation unit and upstream of the benzene column, the xylene separation unit, and the p-xylene separation unit.

[0090] According to a seventeenth aspect, alone or in combination with any other aspect, the system further includes a toluene disproportionation unit including a disproportionation catalyst, downstream of the toluene column and upstream of the p-xylene separation unit, the toluene disproportionation unit fluidly connected to the toluene column unit and the p-xylene separation unit.

[0091] According to the eighteenth aspect, alone or in combination with any other aspect, the reforming catalyst comprises a support and a noble metal, the support comprises silica, alumina or silica-alumina, and the noble metal comprises platinum, ruthenium or both; the first solvent comprises sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, N-formylmorpholine, polyethylene glycol or a combination thereof; the isomerization catalyst and the disproportionation catalyst comprise: a support selected from the group consisting of fluorinated zeolite, mesoporous ZSM-5 zeolite and mesoporous mordenite; and an active metal selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium or a combination thereof; and the mixed alkyltransalkylation / dealkylation catalyst comprises a solid zeolite composite material and an active metal, the solid zeolite composite material comprises macroporous mordenite and mesoporous ZSM-5, wherein the weight ratio of the macroporous mordenite to the mesoporous ZSM-5 is from 1:1 to 5:1, and the active metal is selected from the group consisting of molybdenum, chromium, platinum, nickel, palladium, rhenium or a combination thereof.

[0092] According to the nineteenth aspect, alone or in combination with any other aspect, the active metal of the mixed alkyltransalkylation / dealkylation catalyst is molybdenum.

[0093] According to the twentieth aspect, alone or in combination with any other aspect, the xylene isomerization unit and the toluene disproportionation unit operate at a temperature of 200 °C to 540 °C, a pressure of 1 MPa to 5 MPa and a liquid hourly space velocity of 0.1 hr -1 to 20 hr -1 ; and the mixed alkyltransalkylation / dealkylation unit operates at a temperature of 300 °C to 480 °C, a pressure of 1 MPa to 3 MPa, a liquid hourly space velocity of 0.1 hr -1 to 10 hr -1 and a hydrogen-to-feed ratio of 1 to 6.

[0094] It should be noted that the expressions in the present disclosure that a component of the present disclosure is "operable" or "sufficient" in a specific manner to embody a specific property or to function in a specific manner are structural expressions, rather than expressions of intended use. More specifically, the reference in the present disclosure to the manner in which a component is "operable" or "sufficient" represents the existing physical conditions of the component, and thus, should be regarded as an explicit expression of the structural features of the component.

[0095] It should also be noted that when terms such as "preferably", "usually" and "typically" are used herein, they are not used to limit the scope of the claimed invention or to imply that certain features are critical, essential or even important to the structure or function of the claimed invention. Instead, these terms are merely intended to identify specific aspects of the embodiments of the present disclosure or to emphasize optional or additional features that may or may not be used in specific embodiments of the present disclosure.

[0096] It should be noted that one or more of the appended claims use the term "wherein" as a transitional phrase. To define the present invention, it should be noted that this term is introduced in the claims as an open transitional phrase for introducing a listing of a series of features of a structure and should be understood in the same manner as the more commonly used open preamble term "comprising".

[0097] After the subject matter of the present disclosure has been described in detail with reference to specific embodiments, it should be noted that the various details disclosed in the present disclosure should not be construed as implying that these details relate to elements that are essential components of the various embodiments described in the present disclosure. Additionally, it is obvious that modifications and variations can be made without departing from the scope of the present disclosure, including but not limited to the embodiments defined in the appended claims.

[0098] The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0099] Ranges are provided throughout the present disclosure. It is contemplated that each discrete value encompassed by the range is also included. Additionally, it is equally contemplated that ranges formed by each discrete value encompassed by the explicitly disclosed range are also included.

[0100] As used herein and in the appended claims, the words "comprising", "having", and "including" and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.

[0101] As used herein, terms such as "first" and "second" are arbitrarily assigned and are merely intended to distinguish between two or more instances or components. It should be understood that the words "first" and "second" have no other purpose and are not part of the name or description of a component, nor do they necessarily define the relative position, orientation, or order of the components. Additionally, it should be understood that the mere use of the terms "first" and "second" does not require the existence of any "third" component, although such a possibility is contemplated within the scope of the present disclosure.

Claims

1. An integrated process for producing p-xylene, the process comprising: Catalytically reforming a naphtha feed stream to form a reformate product stream; Separate the reformate product stream into a C1-C7 hydrocarbon stream and a C 8+ hydrocarbon stream; Exposing the C1-C7 hydrocarbon stream to a first solvent in a solvent extraction unit to form a non-aromatic stream and a C6-C7 aromatic stream; Separating the C6-C7 aromatic stream into at least a toluene feed stream; Separate the C 8+ hydrocarbon stream into a C 9+ hydrocarbon stream and a xylene stream containing o-xylene, m-xylene, and p-xylene; Separating the xylene stream in a p-xylene separation unit to form the p-xylene stream and a xylene isomer stream comprising ortho-xylene and meta-xylene; Isomerizing the xylene isomer stream with an isomerization catalyst to produce a p-xylene rich stream; and In a mixed dealkylation / transalkylation unit, the toluene feed stream and the C 9+ hydrocarbon stream are upgraded using a hydrogen stream and a mixed transalkylation / dealkylation catalyst to produce a product stream comprising para-xylene, wherein the weight ratio of the toluene feed stream to the C 9+ hydrocarbon stream is from 0.3 to 3.

2. The method according to claim 1, further comprising: separating the product stream into an additional non-aromatic stream, an additional C6-C7 aromatic stream, an un-converted C9 hydrocarbon fraction stream, an un-converted C 10+ hydrocarbon fraction stream and an additional xylene stream.

3. The process according to claim 2, further comprising at least one of the following: Combine the un-converted C9 hydrocarbon stream and the un-converted C 10+ hydrocarbon distillate stream with the C 9+ hydrocarbon stream, and upgrade the un-converted C9 hydrocarbon distillate stream and the un-converted C 10+ hydrocarbon distillate stream in the mixed dealkylation / transalkylation unit to form an additional product stream; Combining the additional C6-C7 aromatic stream and the C6-C7 aromatic stream and separating the combined C6-C7 aromatic stream into an additional toluene feed stream and a benzene rich stream; or Combining the additional non-aromatic stream with the non-aromatic stream and combining the additional xylene stream and the p-xylene rich stream with the xylene stream.

4. The process according to any one of claims 1 to 3, wherein: The mixed alkyl transfer / dealkylation catalyst comprises a solid zeolite composite and an active metal; The solid zeolite composite comprises macroporous mordenite and mesoporous ZSM-5, wherein the weight ratio of the macroporous mordenite to the mesoporous ZSM-5 is from 1:1 to 5:1; and The active metal is selected from the group consisting of molybdenum, chromium, platinum, nickel, palladium, rhenium, or combinations thereof.

5. The method according to claim 4, wherein, The active metal of the mixed alkyl transfer / dealkylation catalyst is molybdenum.

6. The method according to claim 4 or 5, wherein The mixed alkyl transfer / dealkylation catalyst has a mesostructure comprising at least one disordered mesophase and at least one ordered mesophase.

7. The process according to any one of claims 1 to 6, wherein: The toluene feed stream and the C 9+ hydrocarbon stream has a ratio of greater than 1.5 to 3; and The process further comprises sending at least a portion of the toluene feed stream to a disproportionation unit having a disproportionation catalyst to form an additional xylene stream and a benzene rich stream.

8. The method according to claim 7, wherein The disproportionation catalyst comprises: A support selected from the group consisting of mesoporous ZSM-5 zeolite and mesoporous mordenite; and An active metal selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or combinations thereof.

9. The process according to any one of claims 1 to 8, wherein: The reforming catalyst comprises a support and a noble metal, the support comprises silica, alumina, or silica-alumina, and the noble metal comprises platinum, ruthenium, or both; The first solvent comprises sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, N-formylmorpholine, polyethylene glycol, or combinations thereof; and The isomerization catalyst comprises: a support selected from the group consisting of fluorinated zeolite, mesoporous ZSM-5 zeolite, and mesoporous mordenite; and an active metal selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium, or combinations thereof.

10. An integrated system for producing p-xylene, the system comprising: A catalytic reformer comprising a reforming catalyst; A first separator fluidly connected to the catalytic reformer and downstream of the catalytic reformer; A solvent extraction unit, which contains a first solvent, and the solvent extraction unit is fluidly connected to the first separator and downstream of the first separator; A toluene separation unit, which is fluidly connected to the solvent extraction unit and downstream of the solvent extraction unit; An xylene separation unit, which is fluidly connected to the first separator and downstream of the first separator; A mixed alkyl transfer / dealkylation unit, which contains a mixed alkyl transfer / dealkylation catalyst, and the mixed alkyl transfer / dealkylation unit is fluidly connected to the toluene separation unit and the xylene separation unit and downstream of the toluene separation unit and the xylene separation unit; A p-xylene separation unit, which is fluidly connected to the xylene separation unit and downstream of the xylene separation unit; and An xylene isomerization unit, which contains an isomerization catalyst, downstream and upstream of the p-xylene separation unit, and the xylene isomerization unit is fluidly connected to the p-xylene separation unit.

11. The system according to claim 10, wherein, The toluene separation unit includes: A benzene column, which is fluidly connected to the solvent extraction unit and downstream of the solvent extraction unit; and A toluene column, downstream of the benzene column and upstream of the mixed alkyl transfer / dealkylation unit, and the toluene column is fluidly connected to the benzene column and the mixed alkyl transfer / dealkylation unit.

12. The system according to claim 11, further comprising: a sixth separator fluidly connected to the mixed alkylation / dealkylation unit, the benzene column, the xylene separation unit, and the para-xylene separation unit, wherein, The sixth separator is downstream of the mixed alkyl transfer / dealkylation unit, and upstream of the benzene column, the xylene separation unit and the p-xylene separation unit.

13. The system according to claim 11 or 12, further comprising a toluene disproportionation unit containing a disproportionation catalyst, downstream of the toluene column and upstream of the p-xylene separation unit, and the toluene disproportionation unit is fluidly connected to the toluene column unit and the p-xylene separation unit.

14. The system according to claim 13, wherein: The reforming catalyst contains a carrier and a noble metal, the carrier contains silica, alumina or silica-alumina, and the noble metal contains platinum, ruthenium or both; The first solvent contains sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, N-formylmorpholine, polyethylene glycol or a combination thereof; The isomerization catalyst and the disproportionation catalyst contain: a carrier selected from the group consisting of fluorinated zeolite, mesoporous ZSM-5 zeolite and mesoporous mordenite; and active metals selected from the group consisting of copper, nickel, molybdenum, tungsten, platinum, palladium or a combination thereof; The mixed alkyl transfer / dealkylation catalyst contains a solid zeolite composite material and an active metal, the solid zeolite composite material contains macroporous mordenite and mesoporous ZSM-5, wherein the weight ratio of the macroporous mordenite to the mesoporous ZSM-5 is 1:1 to 5:1, and the active metal is selected from the group consisting of molybdenum, chromium, platinum, nickel, palladium, rhenium or a combination thereof; and The active metal of the mixed alkyl transfer / dealkylation catalyst is molybdenum.

15. The system according to claim 13 or 14, wherein: The xylene isomerization unit and the toluene disproportionation unit operate at a temperature of 200 °C to 540 °C, a pressure of 1 MPa to 5 MPa, and a liquid hourly space velocity of 0.1 hr -1 to 20 hr -1 ; and The mixed alkyl transfer / dealkylation unit operates at a temperature of 300°C to 480°C, a pressure of 1 MPa to 3 MPa, a liquid hourly space velocity of 0.1 hr -1 to 10 hr -1 and a hydrogen-to-feed ratio of 1 to 6.

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