Separation of non-aromatics from a naphtha stream using a membrane system

Abstract

Provided herein are processes, systems, and methods for separating non-aromatic hydrocarbons from aromatic hydrocarbons by utilizing membrane separators. One or more membrane separators may be positioned upstream or downstream from a reformate fractionating column. Accordingly, the processes, systems, and methods of this disclosure are useful in generating aromatic hydrocarbon products such as benzene, toluene, xylenes, A9 / A10 / A11, and non-aromatic hydrocarbon products based on a reformate that includes a mixture of aromatic hydrocarbons and non-aromatic hydrocarbons. The processes, systems, and methods of this disclosure are especially useful that complement operating a reformer at low severity.

Description

NON-AROMATICS SEPARATION TECHNIQUES USING A MEMBRANE SYSTEMFIELD

[0001] This disclosure is directed to techniques for producing certain aromatic hydrocarbon streams by separating non-aromatics during the production of the aromatic hydrocarbons. The disclosed techniques include positioning membrane separators at one or more relative locations (e.g., downstream of certain apparatuses, separation stages, and the like) to generate an enriched product streams that include aromatic hydrocarbons.BACKGROUND

[0002] High purity aromatic hydrocarbon products (e.g., benzene, toluene, xylenes, p-xylene, o-xylene, ethylbenzene, and the like) are valuable industrial commodities that are useful for the production of other value-added industrial chemicals. In a modern petrochemical plant, aromatic hydrocarbon products are generated by separating a mixture comprising one or more such aromatic hydrocarbons and non-aromatic hydrocarbons. One example of such mixture is a reformate stream, which can comprise non-aromatic hydrocarbons at a high concentration (e.g., up to 30 wt %, based on the total weight of the reformate stream). Other examples of such mixture include primarily aromatic hydrocarbon streams generated from a xylenes’ isomerization unit, a transalkylation unit, or a toluene disproportionation unit. Many of the non-aromatic hydrocarbons present in the mixtures are co-boilers of the target aromatic hydrocarbons. As such, generating high purity aromatic hydrocarbon products from the mixture may be difficult and it may be desirable to improve the efficiency of such processes by using techniques other than conventional distillation or extraction processes and equipment.SUMMARY

[0003] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0004] As discussed above, certain processes for generating aromatic hydrocarbons using only distillation processes may be relatively inefficient and costly. For example, after separation of para-xylene, the unconverted meta- and ortho-xylenes are recycled back to the isomerization reactor, along with the non-aromatic compounds. The concentration of non-aromatics continues to increase within the recycle loop as fresh feed from a reformer containing non-aromaticscontinues to be added to the isomerization reactor feed and para-xylene continues to be removed from the recycle loop. Due to this, non-aromatic concentration continues to build up to a high level in the recycle loop negatively affecting the para-xylene yield, and overall process efficiency and capacity.

[0005] Alternatively, the reformer may operate at a high severity to obtain relatively low levels (e.g., 3% or less) of non-aromatics within the final product. However, operating at high severity leads to unwanted side effects, such as higher gas yield and more severe coking of catalysts, which reduces liquid yield and life cycle of the catalyst. Currently, there is a need for improved systems for selectively removing non-aromatic compounds in aromatics-containing streams to form products such as benzene, toluene, xylenes, p-xylene, o-xylene to improve yield, overall process efficiency, and reducing overall costs (e.g., operating costs) of such processes.

[0006] This disclosure relates to methods, processes, and systems for positioning of membrane separators upstream or downstream a reformate splitter to selectively remove non-aromatic hydrocarbons from aromatic hydrocarbons to increase overall process efficiency, improve yield, and provide economic benefits. In general, the techniques discussed herein include positioning one or more membrane separators upstream from the reformate splitter. As such, the membrane separator may generate an enriched reformate stream and a non-aromatics hydrocarbon stream. Additional membrane separators may be positioned downstream from the reformate splitter to generate enriched product streams. In this way, positioning membrane separators allows for the separation of non-aromatics from various aromatic streams during the production of aromatic hydrocarbons products. Further, this may the reformer to be operated at a lower severity with advantages discussed above.

[0007] These and other features and attributes of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

[0009] FIG. 1 is a schematic diagram of a non-aromatic separating system wherein membrane separators are positioned along various streams to separate non-aromatic hydrocarbons from a mixture including aromatic hydrocarbons and non-aromatic hydrocarbons, in accordance with the present disclosure;

[0010] FIG. 2 is a graph illustrating reformate yield vs research octane numbers, in accordance with the present disclosure;

[0011] FIG. 3 is a graph illustrating light ends yield vs research octane numbers, in accordance with the present disclosure;DETAILED DESCRIPTION

[0012] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0013] When introducing elements of various embodiments of the present disclosure, the articles “a," “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. All numerical values within the detailed description herein are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. For example, “about” or “approximately” may refer to ±0.5%, ±1%, ±2, ±5%, ±10%, or ±15%.

[0014] Herein, the use of terms such as “having,” “has,” “including,” or “includes” are open-ended and are intended to have the same meaning as terms such as “comprising” or “comprises” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may” are intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

[0015] By “comprising” or “containing” or “including” is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0016] In the present disclosure, a process is described as comprising at least one “step." It should be understood that each step is an action or operation that may be carried out once or multiple times in the process, in a continuous or discontinuous fashion. Unless specified to thecontrary or the context clearly indicates otherwise, each step in a process may be conducted sequentially in the order as they are listed, with or without overlapping with one or more other step(s), or in any other order, as the case may be. In addition, one or more or even all steps may be conducted simultaneously with regard to the same or different batch of material. For example, in a continuous process, while a first step in a process is being conducted with respect to a raw material just fed into the beginning of the process, a second step may be carried out simultaneously with respect to an intermediate material resulting from treating the raw materials fed into the process at an earlier time in the first step.

[0017] The term “aromatic” is used herein to designate a hydrocarbon-based organic compound containing at least one aromatic ring. The term “non-aromatic” is used herein to designate a hydrocarbon compound having no aromatic nucleus. The term “mixed xylene” is used herein to designate a mixture comprising meta-xylene, ortho-xylene, and para-xylene.

[0018] The term “hydrocarbon” refers to (i) any compound consisting of hydrogen and carbon atoms or (ii) any mixture of two or more such compounds in (i). The term “Cn hydrocarbon,” where n is a positive integer, means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). The term “Cn aromatic hydrocarbon,” where n is a positive integer, means (i) any aromatic hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of n, or (ii) any mixture of two or more such aromatic hydrocarbon compounds in (i). Thus, a C2 hydrocarbon can be ethane, ethylene, acetylene, or mixtures of at least two of them at any proportion. A “Cm to Cn hydrocarbon” or “Cm-Cn hydrocarbon,” where m and n are positive integers and m < n, means any of Cm, Cm+1, Cm+2, ..., Cn-1, Cn hydrocarbons, or any mixtures of two or more thereof. Thus, a “C2 to C3 hydrocarbon” or “C2-C3 hydrocarbon” can be any of ethane, ethylene, acetylene, propane, propene, propyne, propadiene, cyclopropane, and any mixtures of two or more thereof at any proportion between and among the components. A “saturated C2-C3 hydrocarbon” can be ethane, propane, cyclopropane, or any mixture thereof of two or more thereof at any proportion. A “Cm to Cn aromatic hydrocarbon” or “Cm-Cn hydrocarbon,” where m and n are positive integers and m < n, means any of Cm, Cm+1, Cm+2, ..., Cn-1, Cn aromatic hydrocarbons, or any mixtures of two or more thereof. A “Cn+ hydrocarbon” means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of at least n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A “Cn- hydrocarbon” means (i) any hydrocarbon compound comprising carbon atoms in its molecule at the total number of at most n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A “Cm hydrocarbon stream” means a hydrocarbon stream consisting essentiallyof Cm hydrocarbon(s). A “Cm-Cn hydrocarbon stream” means a hydrocarbon stream consisting essentially of Cm-Cn hydrocarbon(s). A “Cn+ aromatic hydrocarbon” means (i) any aromatic hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of at least n, or (ii) any mixture of two or more such aromatic hydrocarbon compounds in (i). A “Cn-aromatic hydrocarbon” means (i) any aromatic hydrocarbon compound comprising carbon atoms in its molecule at the total number of at most n, or (ii) any mixture of two or more such aromatic hydrocarbon compounds in (i). A “Cm aromatic hydrocarbon stream” means a hydrocarbon stream consisting essentially of Cm aromatic hydrocarbon(s). A “Cm-Cn aromatic hydrocarbon stream” means a hydrocarbon stream consisting essentially of Cm-Cn aromatic hydrocarbon(s). C8 aromatics are aromatic compounds having 8 carbon atoms. Examples of C8 aromatics include PX, MX, OX, and ethylbenzene. The term “C8 aromatics” may be used herein interchangeably for PX, MX, OX, and ethylbenzene.

[0019] A number of abbreviations are used herein. B / T stands for Benzene / Toluene. PX stands for paraxylene. MX stands for metaxylene. OX stands for ortho-xylene. EB stands for ethylbenzene. TOL stands for toluene. A9 stands for aromatics molecules which contain 9 carbons. A10 stands for aromatic molecules which contain 10 carbons. Al 1+ stands for aromatic molecules which contain 11 and more carbons. NA stands for non-aromatics such as paraffins, iso-paraffins, or naphthenes, which may be introduced into an adsorption apparatus as a feed impurity, especially when the feed comprises Cs aromatics obtained from a reforming process. HAR stands for heavy aromatics (A9+). HCF stands for hydrocarbon fluids.

[0020] “Xylene,” either in singular or plural form, shall collectively mean one of or any mixture of two or three of para-xylene, meta-xylene, and ortho-xylene at any proportion thereof.

[0021] The term “rich” or “enriched” when describing a component in a stream means that the stream comprises the component at a concentration higher than a source material from which the stream is derived.

[0022] The term “line” refers to a pipe or system of pipes for conveying, carrying, or transferring a fluid.

[0023] The term “depleted” when describing a component in a stream means that the stream comprises the component at a concentration lower than a source material from which the stream is derived. Thus, in embodiments where an admixture stream comprising an aromatic hydrocarbon and a non-aromatic hydrocarbon is separated by a membrane separator comprising a membrane to generate a permeate stream comprising the aromatic hydrocarbon at a higher concentration than the admixture stream and the non-aromatic hydrocarbon at a lower concentration than theadmixture stream, the permeate stream is rich or enriched in the aromatic hydrocarbon and depleted in the non-aromatic hydrocarbon relative to the admixture stream.

[0024] The term “lean” means depleted. A “lean-solvent,” or “lean solvent,” or “hydrocarbon-lean solvent” in this disclosure interchangeably means a composition or stream depleted in hydrocarbon(s) and consisting essentially of solvent.

[0025] A “rich-solvent,” “rich solvent,” or “hydrocarbon-rich solvent” in this disclosure interchangeably means a composition or stream comprising solvent and rich in hydrocarbon(s).

[0026] The term “co-boiler” refers to a compound having a normal boiling point in proximity to that of a reference compound or product. For example, where a reference compound or product has a normal boiling point of bp °C, a co-boiler thereof can have a normal boiling point in the range of bp+30 °C, bp±25°C, bp+20 °C, bp±15 °C, bp±10°C, or bp±5°C. A co-boiler of a reference compound can have a relative volatility in a range from, e.g., 0.5 to 5, or 0.5 to 3, or 0.5 to 2, or 0.5 to 1.5. Typical co-boilers of benzene include, but not are not limited to: methylcyclopentane, cyclohexane, 2,3-dimethylpentane, dimethylcyclopentanes, ethylcyclopentane, and 3 -methylhexane. Due to close boiling points, conventional distillation typically cannot be economically used to separate co-boilers from a reference compound or product. Major non-aromatic co-boilers of aromatic hydrocarbons present in petrochemical products and petrochemical process streams tend to comprise linear, branched, and / or cyclic alkanes and olefins at total high concentration thereof of, e.g., A 60 wt%, A 70 wt%, A 80 wt%, A 90 wt%, A 95 wt%, or even A 98 wt%, based on the total weight of the non-aromatic co-boilers. It should be noted that “co-boilers” and “non-aromatic hydrocarbons” may be used interchangeably.

[0027] The term “heavy components” as used herein refers to components that may be present in a lean- solvent stream differing from the solvent and having a normal boiling point of at least 140 °C, e.g., 150 °C, > 160 °C, > 180 °C, and even > 200°C.

[0028] As referred to herein, a “naphtha” refers to a material obtainable as a distillate of petroleum with a boiling range of approximately 70 to 400°F (20 to 205°C).

[0029] The term “coke” refers to the solid or semi-solid product that can be produced during the steam cracking of hydrocarbons that includes carbon and high carbon-content organic molecules, whether produced within the convection section, radiant section, transfer lines therebetween, or within transfer lines and other equipment, e.g., a transfer line heat exchanger, downstream of the radiant section.

[0030] As used herein, “wt%” means percentage by weight, “vol%” means percentage by volume, “mol%” means percentage by mole, “ppm” means parts per million, and “ppm wt” and“wppm” are used interchangeably to mean parts per million on a weight basis. All “ppm”, as used herein, are ppm by weight unless specified otherwise. All concentrations herein are expressed on the basis of the total amount of the composition in question. Thus, e.g., the concentrations of the various components of a feed composition are expressed based on the total weight of the feed composition. All ranges expressed herein should include both end points as two specific embodiments unless specified or indicated to the contrary.

[0031] The term “membrane separator” refers to a unit that separates materials using a membrane based on, e.g., molecular polarity. Aromatics being more soluble in membrane material absorb in the membrane and diffuse to the permeate side. Non-aromatics being less / non-soluble remains on the feed side and are separated as retentate stream.

[0032] A membrane separator useful in the processes according to the various aspects of this disclosure can comprise a vessel having a first volume, a second volume, and a membrane between the first volume and the second volume. The first volume is separate from the second volume by the membrane. An admixture stream comprising a first component and a second component having a lower polarity than the first component is supplied into the first volume. The membrane is selected to have a polarity such that it is more permeable to the first component than to the second component. Thus, on contacting the admixture stream, the membrane preferentially permits the first component to permeate through to enter into the second volume, from which a permeate stream rich in the first component and depleted in the second component relative to the admixture stream exits. A retentate stream exiting the first volume becomes depleted in the first component and rich in the second component relative to the admixture stream. The permeation of component(s) through the membrane is preferentially facilitated by a pressure drop from the first volume to the second volume. Structure and operation of exemplary membrane separator are provided in FIG. 1 and described in greater detail below.

[0033] The membrane can be polymer-based. The term polymer includes, but is not limited to, homopolymers, copolymers, terpolymers, polymer blends, and the like. For example, suitable polymers for the membrane include, but are not limited to, polyesters, polyethers, polysulfones, polyimides, polyamides, polymers derived from bisphenol-A dianhydride, polyvinyl alcohols, polyacrylonitriles, polyurethanes, polyureas, polyacrylic acids, poly acrylates, elastomeric polymers such as polybutadiene, polyisoprenes, polyvinylpyridines, halogenated polymers, fluoroelastomers, polyvinyl halides, polysiloxanes, poly dimethyl siloxanes, a copolymer comprising at least one of the foregoing polymers, a blend comprising at least one of the foregoing polymers, an alloy comprising at least one of the foregoing polymers, or a combination comprisingat least one of the foregoing polymers, copolymers, blends, or alloys. The polymers could be further physically or chemically cross-linked to increase chemical stability.

[0034] As referred to herein, components (e.g., fractionating columns, membrane separators, and the like) that are in “direct fluid communication” refers to the components having no intervening components. As referred to herein, two components that are in “indirect communication” refers to the components having one or more intervening components, such as membrane separators, fractionating columns, and the like.

[0035] In various preferred embodiments, the membrane can be a polyimletside -based membrane treated by a lubricating oil. In other embodiments, the membrane can comprise an ionic liquid carried by an organic or inorganic matrix material.

[0036] In various preferred embodiments, during operation, the admixture stream supplied into the first volume is in liquid phase. Preferably, during operation, a positive pressure gradient of deltaP kPa exists between the first volume and the second volume, facilitating the permeation of the first component from the first volume into the second volume. Preferably, deltaP can ranges from deltaPl to deltaP2, where deltaPl and deltaP2 can be, independently, e.g., 345, 350, 400, 450, 500, 600, 700, 800, 900, 1,000, 1,500, 2,000, 2,500, 3,000, 3,447, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000, 10,342, as long as deltaPl < deltaP2. Preferably deltaPl = 3,447 and deltaP2 = 8,274.

[0037] Structure, operation and description of exemplary membranes, membrane separators, and membrane separation processes useful in the processes of the aspects of this disclosure include, e.g., U.S. Patent Nos. 4,571,444; 6,187,987; 6,180,008; and 7,642,393; and Zhang, Fan, “Selective Separation of Toluene / n- Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4],” Chem. Eng. Technol. 2015, 38, No. 2, 355-361, the relevant contents in which are incorporated herein by reference.

[0038] Structurally, membrane units may each include a one-stage or multi-stage (e.g., two-stage) membrane system. For example, a one-stage system may be configured to remove approximately 50% of non-aromatics present in an inlet stream while losing approximately 10% of aromatics present in the inlet stream, the aromatics comprising mixed xylenes. A two-stage or other multi-stage membrane system may remove approximately 50% of non-aromatics present in an inlet stream while reducing the loss of aromatics to half of that of single stage membrane system. Adding stages to the membrane unit(s) increases purity of the xylenes that it preferably permeates, though it costs more to construct and maintain. Accordingly, the structure and materials of the membrane(s) making up the membrane units may vary with respect where the membrane separators may be implemented. Membrane units may also operate over a wide varietyof pressure ranges to facilitate improved separation including vacuum conditions to facilitate separation. One mode is “pressure driven membrane process" refers to a type of membrane filtration where a pressure difference is applied across a semipermeable membrane to separate components of a fluid mixture. The second mode is “pervaporation mode” where a membrane separates liquid mixtures by passing one component of the mixture through a membrane and into a vapor phase.

[0039] Reference is now made to the embodiments illustrated in FIGS. 1-3, wherein like numerals are used to designate like parts throughout.

[0040] FIG. 1 illustrates a schematic diagram of a non-aromatic separating system 10, wherein membrane separators can be positioned along various streams (e.g., relative locations upstream / downstream of certain components (e.g., reformers, fractionating columns, and the like)) to separate non-aromatic hydrocarbons from a mixture including aromatic hydrocarbons and non-aromatic hydrocarbons in accordance with an embodiment of the present disclosure. As shown, the non-aromatic separating system 10 includes a reformer 12, a reformate fractionating column 14 (e.g., reformate splitter), a fluid columns unit 16 (e.g., heavy aromatics (HAR) fractionating column), xylenes fractionating column 18 (e.g., xylenes splitter), an OX fractionating column 20 (e.g., OX column), a para-xylenes (PX) recovery unit 22, a xylene isomerization unit 24, a deheptanizer unit 26, and a clay treater unit 28. Further, the non-aromatic separating system 10 includes membrane separators 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, and 30j (collectively 30). In general, the non-aromatic separating system 10 of FIG. 1 generates a B / T stream 32, a PX stream 34, an OX stream 36, an A9 / A10 stream 38, and an A10 / A11+ stream 40. It should be noted that the positions of the membrane separators 30 illustrated in this figure are meant to be illustrative and non-limiting.

[0041] In some embodiments, the non-aromatic separating system 10 may include one or more membrane separators. For example, in one embodiment, the non-aromatic hydrocarbon separating system 10 may include one or more membrane separators 30 upstream of the reformate fractionating column 14. In another embodiment, the non-aromatic hydrocarbon separating system 10 may include the membrane separator 30a, 30b, or a combination thereof, but membrane separators 30c, 30d, 30e, 30f, 30g, 30h, 30i, and 30j may be omitted. In some embodiments, the non-aromatic hydrocarbon separating system 10 may include one or more membrane separators downstream of the reformate fractionating column 14. For example, the non-aromatic hydrocarbon separating system 10 may include membrane separators 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, or any combination thereof. As such, it is presently recognized that the positioning the membrane separators 30 may allow the reformer 12 to operate at a lower severity and or with atailored feed, thereby causing the reformer 12 to produce a reformate stream 50 that is relatively high in non-aromatics within the carbon range of interest (e.g., greater than 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, and so on). While producing relatively more non-aromatics may result in higher amounts of non-aromatics in resulting product streams (e.g., the B / T stream 32, the PX stream 34, the OX stream 36, the A9 / A10 stream 38, and the A10 / A11+ stream 40), the membrane separators 30 may remove the additional non-aromatics. Accordingly, the nonaromatic separating system 10 may produce high purity product streams based on the reformate stream 50 output by the reformer 12, although the reformer 12 is operating at a lower severity.

[0042] In general, a naphtha stream 42 may be provided to a membrane separator 30a. Membrane separator 30a may be positioned (e.g., disposed, placed) downstream from a naphtha supplier to receive the naphtha stream 42. In this way, the membrane separator 30a may receive as input (e.g., via one or more inlet ports) and separate the naphtha stream 42, thereby generating (e.g., producing) an aromatics stream 44 and an enriched naphtha stream 46. The aromatics stream 44 and enriched naphtha stream 46 may be output (e.g., via one or more outlet ports) from the membrane separator 30a. Accordingly, positioning membrane separator 30a upstream from the reformer 12 advantageously enables processing various naphtha stream 42 (e.g., stream cracking of naphtha (SCN)-steam cracked, fluid cracked, hydro cracked, virgin naphtha, cracked naphtha). The cracked naphtha may originate from a coker, a fluid catalytic cracker, a hydrocracker, selective catalytic cracking processes. For example, a virgin naphtha stream may include about 50 to about 65% of a mixture including linear paraffins and isoparaffins, about 30 to about 40% of naphthenes, about 5 to about 10% aromatics, and low levels of olefins. A steam cracked naphtha stream may include about 15 to about 40% of a mixture including linear paraffins and isoparaffins, about 2 to about 7% of naphthenes, about 55 to about 78% aromatics, and treated to low levels of olefins. A catalyst (cat) cracked naphtha stream may include about 20 to about 70% of a mixture including linear paraffins and isoparaffins, about 10 to about 20% or more of naphthenes, about 20 to about 30% or more aromatics, and treated to low levels of olefins. Based on the composition and type of naphtha, the naphtha stream 42 would be pretreated. Accordingly, the naphtha stream 42 may be fed into a membrane separator 30 (e.g., membrane separator 30a) to make a retentate stream enriched in aromatics and a permeate stream enriched in non-aromatics. The removal of unwanted products from the naphtha stream 42 prior to feeding the stream into the reformer 12 enables the non- aromatic separating system 10 to accommodate various compositions of naphtha stream 42 and allows the reformer 12 to operate at a lower severity. In addition, depending on the type of naphtha stream 42, the enriched naphtha stream 46 could be routed directly to the reformer 12 or bypass the reformer 12 and be routed to alternative columns. In this way, positioning amembrane separator 30a upstream from the reformer 12 provides many advantages, as various configurations of non-aromatic hydrocarbon separating system 10 may be implemented based on the naphtha stream 42 accordingly.

[0043] With the foregoing in mind, the reformer 12 receives the enriched naphtha stream 46 and generates reformate stream 50. The reformate stream 50 may be a mixture containing non-aromatic hydrocarbons and aromatic hydrocarbons. The aromatic hydrocarbons may include benzene, toluene, ethylbenzene, xylenes (e.g., ortho-xylene, para-xylene, meta-xylene), heavy aromatics (e.g., A9 / A10 / A11+). As shown, the reformate stream 50 is in fluid communication with membrane separator 30b, wherein the membrane separator 30b may be positioned downstream to receive as input the reformate stream 50 such that it may separate non-aromatic hydrocarbons from the reformate stream 50 and generate enriched aromatic hydrocarbons stream 52. The enriched aromatic hydrocarbons stream 52 (e.g., additional reformate stream) includes aromatic hydrocarbons (e.g., may include benzene, toluene, ethylbenzene, xylenes (e.g., orthoxylene, para-xylene, meta-xylene), heavy aromatics (e.g., A9 / A10 / A11+)) and is depleted in non-aromatic hydrocarbons (e.g., co-boilers) relative to (e.g., based on) the reformate stream 50. Additionally, the membrane separator 30b may generate a non-aromatics hydrocarbons stream 54 from the reformate stream 50 wherein the non-aromatics hydrocarbons stream 54 is enriched with non-aromatic hydrocarbons and depleted in aromatic hydrocarbons relative to the reformate stream 50. By positioning membrane separator 30b downstream from the reformer 12, it enables the reformer 12 to operate at a low severity and reduces gas yield. It should be noted that the membrane separators 30 may generate one or more streams, wherein a first stream may consist of a stream enriched with non-aromatic hydrocarbons and depleted in aromatic hydrocarbons, and a second stream may consist of a stream enriched with aromatic hydrocarbons and depleted in non-aromatic hydrocarbons.

[0044] Non-aromatics hydrocarbons stream 54 may still include aromatic hydrocarbons at various quantities. As such, while non-aromatic hydrocarbon processing is omitted from the diagram, additional columns and / or units may be in fluid communication with the non-aromatic hydrocarbon streams (e.g., non-aromatics hydrocarbons stream 54) and can be sent to extraction units, mogas blending systems, or other outlets if needed. It should be noted that any of the non-aromatics hydrocarbons streams produced may preferentially be used for steam cracking or selective catalytic cracking. In general, positioning the membrane separator 30b downstream from the reformer 12 allows for the reformer 12 to operate at a lower severity. Although operating the reformer 12 at a lower severity may generate a larger amount of non-aromatic hydrocarbons relative to operating the reformer 12 at a higher severity, positioning and implementing one ormore membrane separators 30 upstream or downstream from the reformer 12 provides advantages such as operating the reformer 12 at a low severity and introducing one or more purification stages to obtain enriched product streams.

[0045] As shown in FIG. 1, the reformate fractionating column 14 may be in fluid communication with the membrane separator 30b, a membrane separator 30c, and membrane separator 30d. The reformate fractionating column 14 is positioned downstream from the membrane separator 30b such that it may receive enriched aromatic hydrocarbons stream 52 from the membrane separator 30b. In turn, the reformate fractionating column 14 may generate a crude B / T stream 56 and a crude xylene stream 58 by fractionating the enriched aromatic hydrocarbons stream 52.

[0046] As shown, the membrane separator 30c is positioned downstream from the reformate fractionating column 14 and is in fluid communication with the reformate fractionating column 14 such that it may receive the crude B / T stream 56. The crude B / T stream 56 may include a mixture of benzene, co-boilers of benzene, toluene, and co-boilers of toluene. Accordingly, the membrane separator 30c may separate non-aromatic hydrocarbons from the crude B / T stream 56, thereby generating enriched B / T stream 118. The enriched B / T stream 60 includes a stream enriched in benzene and toluene and depleted in non-aromatic hydrocarbons relative to crude B / T stream 56. Membrane separator 30c may also generate a non-aromatics hydrocarbons stream 62 from the crude B / T stream 56. The non-aromatics hydrocarbons stream 62 is enriched with non-aromatic hydrocarbons and depleted in benzene and toluene relative to the crude B / T stream 56. Further, the membrane separator 30c is in fluid communication with extraction unit 64, wherein the extraction unit 64 is disposed downstream from the membrane separator 30c such that it may receive enriched B / T stream 60. In general, positioning the membrane separator 30c downstream from the reformate fractionating column 14 provides advantages such as reducing the energy consumption and unit capacity of downstream units (e.g., extraction unit 64). Accordingly, the extraction unit 64 may extract product streams based on the enriched B / T stream 60, thereby generating B / T stream 32. For example, the B / T stream 32 may include a benzene-enriched stream, a benzene / toluene mixture stream, a toluene-enriched stream, C8 hydrocarbons-enriched stream, and a non-aromatics hydrocarbons stream. It should be noted that while the various streams generated by the extraction unit 64 are omitted from the diagram, additional columns and / or units may be in fluid communication with the various streams and can be sent to alternative outlets. For example, the various aromatic hydrocarbon streams can be used as high-quality feeds for various downstream processes (e.g., transalkylation, xylene isomerization, toluene disproportionation, benzene / toluene methylation for making xylenes). Further, a portion or theentirety of the non-aromatic hydrocarbons stream 62 can be sent to extraction units, mogas blending systems, or other outlets if needed.

[0047] As shown, the membrane separator 30d is positioned downstream from the reformate fractionating column 14 and is in fluid communication with the reformate fractionating column 14 such that it may receive the crude xylenes stream 58. The crude xylenes stream 58 may include a mixture of xylenes (e.g., OX, PX, MX), ethylbenzene (EB), C8+ aromatics, co-boilers of xylenes, co-boilers of C8+ aromatics, and co-boilers of EB. Accordingly, the membrane separator 30d may separate non-aromatic hydrocarbons from the crude xylenes stream 58, thereby generating enriched xylenes stream 66. The enriched xylenes stream 66 includes a stream enriched in xylenes (e.g., OX, PX, MX), ethylbenzene (EB), and C8+ aromatics and depleted in non-aromatic hydrocarbons relative to crude xylenes stream 58. Membrane separator 30d may also generate a non-aromatics hydrocarbons stream 68 based on cmde xylenes stream 58, wherein the non-aromatics hydrocarbons stream 68 is enriched with non-aromatic hydrocarbons and depleted in xylenes (e.g., OX, PX, MX) and ethylbenzene (EB) relative to the cmde xylenes stream 58. A portion or the entirety of the non-aromatic hydrocarbons stream 68 can be sent to extraction units, mogas blending systems, or other outlets if needed. In general, positioning the membrane separator 30d downstream from the reformate fractionating column to receive cmde xylenes stream 58 provides advantages such as reducing non-aromatics cracking in the xylene isomerization unit 24, energy savings of downstream columns (e.g., OX fractionating column 20, fluid columns unit 16), and purification of cmde xylenes stream 58 to obtain the enriched xylenes stream 66. Accordingly, the xylenes fractionating column 18 may receive the enriched xylenes stream 66 for additional processing.

[0048] The xylenes fractionating column 18 is positioned downstream from membrane separator 30d such that it may receive enriched xylenes stream 66. The xylenes fractionating column 18 may include a fractional distillation column, selective sorption unit, or other technology known in the art. Accordingly, the xylenes fractionating column 18 may fractionate the enriched xylenes stream 66, thereby generating cmde PX stream 70 (top-cut) and cmde OX stream 72 (bottom-cut). Because the xylenes fractionating column 18 generates two streams (e.g., cmde PX stream 70 and cmde OX stream 72), the xylenes fractionating column 18 is in fluid communication with membrane separator 30e and membrane separator 30i.

[0049] As shown, the membrane separator 30e is positioned downstream from the xylenes fractionating column 18 and is in fluid communication with the xylenes fractionating column 18 such that it may receive cmde PX stream 70. The cmde PX stream 70 may include a mixture of PX, C8+ aromatics, co-boilers of C8+ aromatics, and co-boilers of PX. It should be noted thatcrude PX stream 70 may be depleted in OX, MX, EB, C8+ aromatics relative the amount of PX. Accordingly, the membrane separator 30e may separate non-aromatic hydrocarbons from the crude PX stream 70, thereby generating enriched PX stream 74. The enriched PX stream 74 includes a stream enriched in PX and C8+ aromatics and depleted in non-aromatic hydrocarbons relative to the crude PX stream 70. Membrane separator 30e may also generate a non-aromatics hydrocarbon stream 76 based on crude PX stream 70, wherein the non-aromatics hydrocarbons stream is enriched with non-aromatic hydrocarbons and depleted in PX and C8+ aromatics relative to the crude PX stream 70. In general, positioning the membrane separator 30e downstream from the xylene fractionating column 18 provides advantages such as reducing the energy consumption of downstream units (e.g., PX recovery unit 22) and reducing the amount of non-aromatics cracking in the xylenes isomerization unit 24. A portion or the entirety of the non-aromatic hydrocarbons stream 76 can be sent to extraction units, mogas blending systems, or other outlets if needed. Accordingly, the PX recovery unit 22 may receive the enriched PX stream 74 for additional processing.

[0050] The PX recovery unit 22 is positioned downstream from the membrane separator 30e such that it may receive the enriched PX stream 74 within the xylene recovery loop 150. The paraxylenes recovery unit 22 may include one or more of any of the PX recovery units known in the art, including, for example, a crystallization unit, an adsorption unit (such as a PAREX™ unit or an ELUXYL™ unit), a reactive separation unit, a membrane separation unit, an extraction unit, a distillation unit, an extractive distillation unit, a fractionation unit, a simulated moving bed type of recovery unit, or any combination thereof. The PX recovery unit 22 may process the enriched PX stream 74 and generate PX stream 34 wherein the PX stream 34 is enriched in PX to generate higher purity PX products. Concomitantly, the PX recovery unit 22 may generate a PX depleted stream 78, which may be received by a membrane separator 30f. In general, the PX depleted stream 78 may consist of other C8+ aromatics (e.g., MX, OX, EB) in greater amounts than PX.

[0051] As shown, the membrane separator 30f is positioned downstream from the PX recovery unit 22 and is in fluid communication with the PX recovery unit 22, allowing it to receive PX depleted stream 78. Accordingly, the membrane separator 30f may separate non-aromatic hydrocarbons from the PX depleted stream 78, thereby generating a C8 aromatics enriched stream 80, wherein C8 aromatics enriched stream 80 is enriched with C8 aromatics (e.g., MX, OX, EB, small amounts of PX) and depleted in non-aromatic hydrocarbons. The membrane separator 30f may also generate a non-aromatics hydrocarbons stream 82 that is enriched with non-aromatic hydrocarbons and depleted in C8+ aromatics. In general, positioning the membrane separator 30f downstream from the PX recovery unit 22 provides advantages such as reducing the amount ofnon-aromatics cracking in the xylenes isomerization unit 24. A portion or the entirety of the nonaromatic hydrocarbons stream 82 can be sent to extraction units, mogas blending systems, or other outlets if needed.

[0052] Further downstream, the xylene isomerization unit 24 may be in fluid communication with membrane separator 30f and positioned to receive C8 aromatics enriched stream 80. The xylene isomerization unit 24 may also be in fluid communication to receive, directly or indirectly, a hydrogen (H2) stream 84 (e.g., from a source external from non-aromatic hydrocarbon separating system 10). Accordingly, the xylene isomerization unit 24 may output a crude isomerization product stream 86. The xylene isomerization unit 24 may generate equilibrium xylene ratios of approximately about 50% by weight meta-xylene, about 26% by weight ortho-xylene, and about 24% by weight para-xylene. In other embodiments, the equilibrium xylene ratio of para-xylene may be under 24%, and the ratios for meta-xylene and ortho-xylene would be proportionally higher. The xylene isomerization unit 24 may also crack certain hydrocarbons to form lighter molecules, categorized as fuel gas, as well as certain aromatics. The xylene isomerization unit 24 may be any type of isomerization unit known in the art, including, for example, a unit comprising a catalyst for adequate xylene conversion.

[0053] With the foregoing in mind, the membrane separator 30g may be positioned downstream from the xylene isomerization unit 24 and is in fluid communication with the xylene isomerization unit 24 such that it may receive crude isomerization product stream 86. As a result, the membrane separator 30g may separate crude isomerization product stream 86, thereby enriched isomerization product stream 88, wherein the enriched isomerization product stream 88 is depleted in non-aromatic hydrocarbons relative to crude isomerization product stream 86. Additionally, the membrane separator 30g may generate a non-aromatics hydrocarbons stream 91 from the crude isomerization product stream 86, wherein the non-aromatics hydrocarbons stream 91 is enriched with non-aromatic hydrocarbons relative to crude isomerization product stream 86.

[0054] The deheptanizer unit 26 is positioned downstream from the membrane separator 30g and is in fluid communication with the membrane separator 30g such that it may receive the enriched isomerization product stream 88 and generate a xylene rich stream 90, a fuel gas stream 92 (e.g., C5 compounds), and a hydrocarbon stream 94. In general, positioning the membrane separator 30g upstream from the deheptanizer unit 26 provides advantages such as reducing the amount of non-aromatics cracking. Accordingly, the hydrocarbon stream 94 may include C6 aromatic compounds, C7 aromatic compounds, and non-aromatic hydrocarbons. The deheptanizer unit 26 may direct the xylene rich stream 90 to the clay treater unit 28, direct the fuel gas stream92 outside of non-aromatic hydrocarbon separating system 10, and direct the hydrocarbon stream 94 to membrane separator 30h.

[0055] The clay treater unit 28 may be positioned downstream from the deheptanizer unit 26 and is in fluid communication with the deheptanizer unit 26 such that it may receive the xylene rich stream 90. As such, the clay treater unit 28 may generate a clay treated stream 96, which may be fed back into the xylenes fractionating column 18, upon which the process of xylene recovery loop 150 may be repeated.

[0056] As shown, the membrane separator 3 Oh may be positioned downstream from the deheptanizer unit 26 and is in fluid communication with the deheptanizer unit 26 such that it may receive hydrocarbon stream 94. As such, the membrane separator 30h may separate non-aromatic hydrocarbons from the hydrocarbon stream 94, thereby generating an aromatic enriched stream 32, 98 (e.g., an additional B / T stream). The aromatics enriched stream 98 may be enriched with C6 aromatic compounds (e.g., benzene, toluene) and C7 aromatic compounds and depleted in non-aromatic hydrocarbons relative to hydrocarbon stream 94. Additionally, the membrane separator 30h may generate a non-aromatics hydrocarbons stream 100 from the hydrocarbon stream 94, wherein the non-aromatics hydrocarbons stream 100 is enriched with non-aromatic hydrocarbons and depleted in aromatic hydrocarbons relative to the hydrocarbon stream 94. In general, positioning the membrane separator 30h downstream from the deheptanizer unit 26 provides advantages such as producing B / T stream 32, 98. As such, while non-aromatic hydrocarbon processing is omitted from the diagram, additional columns and / or units may be in fluid communication with the non-aromatic hydrocarbon streams (e.g., non-aromatics hydrocarbons stream 100) and can be sent to extraction units, mogas blending systems, or other outlets if needed. Further, aromatics enriched stream 98 may be in fluid communication with additional units for processing if desired.

[0057] In some instances, it may be advantageous to direct the non-aromatics hydrocarbons stream 91 and / or the non-aromatics hydrocarbons stream 100 back to the xylene isomerization unit 24. For example, the xylene isomerization unit 24 (e.g., EB isomerization type catalyst) may utilize a C8 naphthene intermediate, wherein the operation of the deheptanizer unit 26 may be modified to include the fractionation of the C8 naphthene intermediate as a side product or included with the B / T stream 32,98. Accordingly, the membrane separators 30g and / or 30h may allow the C8 naphthene intermediate to be separated from the aromatics stream and recycled back to the xylene isomerization unit 24. Put differently, the non-aromatics hydrocarbons stream 91 and / or the non-aromatics hydrocarbons stream 100 may be recycled upstream (e.g., combinedwith PX depleted stream 78). In this way, the membrane separators 30g and / or 30h enable efficient recycling and reduce loss of product.

[0058] As shown, the membrane separator 30i is positioned downstream from the xylenes fractionating column 18 and is in fluid communication with the xylenes fractionating column 18 such that it may receive crude OX stream 72. The crude OX stream 72 may include OX, MX, EB, C8+ aromatics, co-boilers of OX, co-boilers of MX, co-boilers of C8+ aromatics, and co-boilers of EB and depleted in PX (e.g., small quantities of PX). Accordingly, the membrane separator 30i may separate crude OX stream 72, thereby generating enriched OX stream 102. The enriched OX stream 102 includes xylenes (e.g., OX, MX, EB, C8+ aromatics) and depleted in non-aromatic hydrocarbons relative to the crude OX stream 72. Additionally, the membrane separator 30i may generate a non-aromatics hydrocarbons stream 104 from the crude OX stream 72, wherein the non-aromatics hydrocarbons stream 104 is enriched with non-aromatic hydrocarbons and depleted in OX, MX, EB, and C8+ aromatics relative to the crude OX stream 72. A portion or the entirety of the non-aromatic hydrocarbons stream 104 can be sent to extraction units, mogas blending systems, or other outlets if needed. In general, positioning the membrane separator 30i downstream from the xylenes fractionating column 18 to receive crude OX stream 72 provides advantages such as reducing energy consumption of downstream columns (e.g., OX fractionating column 20) and purification of crude OX stream 72 to obtain the enriched OX stream 102. Accordingly, the OX fractionating column 20, that is disposed downstream from the membrane separator 30i, may receive the enriched OX stream 102 to generate OX stream 36.

[0059] The OX fractionating column 20 is in fluid communication with membrane separator 30i such that it may receive enriched OX stream 102 as input and generate OX stream 36. It should be noted that the OX stream 36 (e.g., OX product stream) is enriched with OX relative to the enriched OX stream 102. Concomitantly, the OX fractionating column 20 may also generate OX depleted stream 106 (e.g., crude heavy aromatics stream). The OX depleted stream 106 may include MX, EB, C8+ aromatics, non-aromatic hydrocarbons and depleted in OX. Accordingly, the OX fractionating column 20 is in fluid communication with membrane separator 30j, which is positioned downstream from the OX fractionating column 20. As such, the membrane separator 30j may receive OX depleted stream 106 and separate non-aromatic hydrocarbons from the OX depleted stream 106, thereby generating enriched C8+ aromatics stream 108 (e.g., enriched heavy aromatics stream). Enriched C8+ aromatics stream 108 may be enriched with MX, EB, C8+ aromatics (e.g., A9 / A10 / A11+) and depleted in non-aromatic hydrocarbons relative to OX depleted stream 106. Additionally, the membrane separator 30j may generate a non-aromatic hydrocarbon stream 110, wherein the non-aromatics hydrocarbons stream 110 is enriched withnon-aromatic hydrocarbons and depleted in xylenes (e.g., MX), C8+ aromatics, and ethylbenzene (EB) relative to the OX depleted stream 106. A portion or the entirety of the non-aromatic hydrocarbons stream 110 can be sent to extraction units, mogas blending systems, or other outlets if needed. As such, fluid columns unit 16 may be positioned downstream from the membrane separator 30j such that it may receive the enriched C8+ aromatics stream 108. In general, positioning the membrane separator 30j downstream from the OX fractionating column 20 provides advantages such as reducing energy consumption and capacity of downstream columns (e.g., fluid columns unit 16) and purification of OX depleted stream 106 to obtain the enriched C8+ aromatics stream 108. Accordingly, the C8+ aromatics stream 108 may be provided to the fluid columns unit 16 for additional processing.

[0060] The fluid columns unit 16 is in fluid communication with membrane separator 30j such that it may the receive enriched C8+ aromatics stream 108 and generate A9 / A10 stream 38 and A10 / A11+ stream 40. The enriched C8+ aromatics stream 108 may include a mixture of A9, A10, A11+, co-boilers of A9, co-boilers of A10, and co-boilers of A11+. Accordingly, the fluid columns unit 16 may output one or more streams (e.g., fluid product streams, fluid products, heavy aromatic product streams, heavy products, heavy fluids) based on the enriched C8+ aromatics stream 108. For example, fluid columns unit 16 may separate the enriched C8+ aromatics stream 108 and output heavy aromatic product streams, such as hydrocarbon fluid (HCF) stream 38, HCF stream 40, HCF stream 42, and HCF stream 44. In general, the HCF stream 38 may be predominantly A9, the HCF stream 40 may include a mixture of A9 and A 10, the HCF stream 42 may include a mixture of All and A12, and the HCF stream 44 may be predominantly A11+ stream. The one or more heavy aromatics streams produced by fluid columns unit 16 may be used as solvent-based products. For example, the one or more heavy aromatics streams may include an A9 / A10 stream and an A10 / A11+ stream. It should be noted that the streams 38, 40, and 110 may be in fluid communication with additional units and undergo additional processing.

[0061] It should be noted that the positions of the membrane separators 30 illustrated in this figure are meant to be illustrative and non-limiting. That is, in some embodiments, only some of the membrane separators 30 may be included in the non-aromatic hydrocarbon separating system 10.

[0062] In any case, the non-aromatic separating system 10 of FIG. 1 includes one or more membrane separators 30 disposed on flow paths that connect different components (e.g., including one or more of the reformer 12, the reformate splitter 14, the fluid columns unit 16, the xylene splitter 18, the OX column 20, the PX recovery unit 22, the xylene isomerization unit 24, the deheptanizer 26, and the like) of the non-aromatic hydrocarbon separating system 10. In someembodiments, the non-aromatic separating system 10 includes a first flow path (e.g., including one or more of the enriched naphtha stream 46, the reformate stream 50, and the enriched aromatic hydrocarbons stream 52) having one or more membrane separators 30. The first flow path fluidly connects or couples the reformer 12 and the reformate splitter 14. In some embodiments, the non-aromatic separating system 10 includes a second flow path (e.g., including one or more of the crude xylene stream 58, the enriched xylenes stream 66, the crude OX stream 72, the enriched OX stream 102, the OX depleted stream 106, and the enriched C8+ aromatics stream 108) having one or more membrane separators 30. The second flow path fluidly connects the reformate splitter 14, the xylene splitter 18, the OX column 20, and the fluid columns 16. In some embodiments, the non-aromatic separating system 10 includes a third flow path (e.g., including the crude B / T stream 56, the enriched B / T stream 60, or both) having one or more membrane separators 30. The third flow path fluidly connects the reformate splitter 14 and the extraction unit 14. Additionally of alternatively, the non-aromatic separating system 10 may include the xylene recovery loop 150 having one or more membrane separators 30. In such embodiments, the xylene recovery loop 150 may be fluidly coupled to the second flow path.

[0063] With the foregoing in mind, FIGS. 2 and 3 show specific, non-limiting examples of the reformate versus research octane numbers (RON) and light ends (e.g., non-aromatic hydrocarbons) versus research octane numbers (RON), respectively, when operating the reformer 12 at a low severity. In general, RON correlates inversely to non-aromatic levels. Typically, a reformer severity is adjusted to maintain non-aromatics targets with specific carbon number ranges (e.g., C7 range, C8 range, C9 range). Without the present invention, it likely requires operating at increased reformer severity and will downgrade product (i.e., reformate yields) and generate lighter ends. For example, FIG. 2 is a graph 200 illustrating reformates in liquid % volume versus octane numbers. The reformate produced in accordance with the system of FIG. 1 may exhibit a reformate yield that decreases as the RON increases from about 90 to about 100.

[0064] FIG. 3 is a graph 210 illustrating light ends in liquid% volume versus octane numbers. In general, the light ends produced include C1-C2, H2, C4, and C3. In general, the yield of Cl-C2, H2, C4, and C3 increases slightly as the RON increases from about 90 to about 100.

[0065] Certain conventional techniques may use membrane separators at process locations to achieve removal of non-aromatic to low levels (e.g., less than 10%) from an aromatic stream (e.g., benzene, toluene, mixed xylenes). Surprisingly, the disclosed techniques demonstrate membrane separators have an equal or even greater utility during “process intensification", which refers to a process wherein bulk separation is performed for streams that are not primarily aromatics (e.g., naphtha stream 42, enriched naphtha stream 46, crude B / T stream 60). Given that membraneseparators may be utilized for process intensification, various feed streams that vary in composition can be processed by the membrane separators, which provides benefits such as enabling feeds to existing assets to be tailored, thereby meeting changes in feed availability and product demands. The use of membranes for “process intensification” (e.g., membrane separators 30a, 30b, 30c) improves yields across numerous downstream processing steps and energy efficiency, which greatly improves the magnitude of the benefit and will have particular usefulness in helping manage feedstock and product transitions expected over the next 20 years with electrification of automobiles, thereby creating energy and capital efficient processing options. Particularly, the discovery may enable existing technology to achieve higher chemical yields and lower fuel byproducts.

[0066] Historically, meeting non-aromatics levels in ortho-xylene products and heavy fluids products has been easily achievable since reformer operations were valued for both hydrogen and octane and / or aromatics production. As fuel transitions occur, both of the following scenarios may follow, which include: 1) large scale, lower cost, hydrogen production that includes carbon capture will likely change the demand and value of reformer hydrogen and 2) demand for reformate (e.g., reformer unit product) for motor gasoline where large volumes are utilized will decline due to an increase in electric vehicles (EVs), thereby reducing a demand for motor gasoline. These scenarios may create a transition period, wherein feeds and operating severity of reformers will change and operate differently relative to conventional means. Accordingly, the disclosed techniques, such as the novel implementation of the membrane separators, provide a viable means to navigate such scenarios in a cost-efficient way. This novelty, when combined with membranes located upstream of the main aromatic processing block (e.g., membrane separators 30a, 30b, or 30c), may fully enable removal of downstream steps (e.g., skipping of reformate and fractionation steps) by utilizing membrane separators (e.g., 30i, 30j) to remove residual co-boiling non-aromatics in the ortho-xylene and heavy fluids products in existing equipment.

[0067] Accordingly, the present disclosure is directed to methods, processes, and systems for positioning membrane separators upstream or downstream a reformate fractionating column (e.g., reformate splitter) to selectively remove non-aromatic hydrocarbons from aromatic hydrocarbons to increase overall process efficiency, improve yield, and provide economic benefits. In general, one or more membrane separators may be positioned upstream from the reformate fractionating column such that it may separate non-aromatic hydrocarbons from the reformate. Additionally, one or more membrane separator may be positioned downstream from the reformate splitter such that it may separate non-aromatic hydrocarbons from product streams. One or more membraneseparators may be advantageously positioned in one or more positions to remove non-aromatic hydrocarbons from aromatic hydrocarbons. It is presently recognized that incorporating one or more membrane separators to separate non-aromatics from aromatic hydrocarbons allows for the reformer to operate at a lower severity, which provides technical effects and advantages such as increasing overall process efficiency, improving yield, and providing economic benefits by reducing consumption of catalysts. For example, the membrane separators may remove non-aromatics from streams downstream of the reformer 12 that include a relatively higher amount of non-aromatics (e.g., greater than 3 wt% in the reformate stream 50) due to operating at a lower severity. Furthermore, positioning a membrane separator upstream the reformer advantageously enables various types of naphtha streams to be processed. In this way, the systems described herein may accommodate various types of naphtha streams.

[0068] Embodiment 1. A system includes one or more membrane separators configured to receive a flow path including a naphtha stream, and wherein the one or more membrane separators are configured to produce, based on the naphtha stream, an aromatics rich stream and an enriched naphtha stream, wherein the naphtha stream includes aromatic hydrocarbons and non-aromatic hydrocarbons.

[0069] Embodiment 2. The system of any preceding claim, further including one or more conduits providing the flow path of the naphtha stream to the one or more membrane separators.

[0070] Embodiment 3. The system of any preceding claim, including an isomerization unit, wherein the enriched naphtha stream is recycled upstream of the isomerization unit.

[0071] Embodiment 4. The system of any preceding claim, wherein the naphtha stream is generated based on operation of a coker, a fluid catalytic cracker, a hydrocracker, or selective catalytic cracking processes.

[0072] Embodiment 5. The system of any preceding claim, wherein the naphtha stream includes about 20 to about 70% linear paraffins and isoparaffins.

[0073] Embodiment 6. The system of any preceding claim, wherein the naphtha stream is pretreated to remove olefins.

[0074] Embodiment 7. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators produces the aromatics rich stream and the enriched naphtha stream while operating in accordance with a pervaporation mode.

[0075] Embodiment 8. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators includes a one-stage membrane system.

[0076] Embodiment 9. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators includes a multi-stage membrane system.

[0077] Embodiment 10. The system of any preceding claim, wherein the naphtha stream includes a SCN-steam cracked stream, a fluid cracked stream, a hydro cracked stream, a virgin naphtha stream, a cracked naphtha stream, an output stream of a coker, a catalytically cracked naphtha stream, or any combination thereof.

[0078] Embodiment 11. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators produces the aromatics rich stream and the enriched naphtha stream while operating in accordance with vacuum conditions.

[0079] Embodiment 12. The system of any preceding claim, further including a reformer upstream of the one or more membrane separators along the flow path.

[0080] Embodiment 13. The system of any preceding claim, further including a fractionating column disposed along the flow path.

[0081] Embodiment 14. A system includes a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream includes aromatic hydrocarbons and non-aromatic hydrocarbons. The system also includes a reformate splitter positioned downstream from the reformer, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream. Further, the system includes one or more membrane separators are positioned upstream, downstream, or both from the reformate splitter, wherein the one or more membrane separators is configured to remove at least a portion the aromatic hydrocarbons.

[0082] Embodiment 15. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators is positioned upstream from the reformer, wherein the membrane separator is configured to generate an enriched naphtha stream by removing at least the portion of aromatic hydrocarbons from the naphtha stream, and wherein the reformer is configured to generate the reformate stream based on the enriched naphtha stream.

[0083] Embodiment 16. The system of any preceding claim, wherein a membrane separator of the one or more membrane separators is positioned downstream from the reformer and upstream of the reformate splitter, wherein the membrane separator is configured to generate an enriched aromatics hydrocarbon stream by removing at least the portion of the aromatic hydrocarbons from the reformate stream, and wherein the reformate splitter is configured generate the crude xylenes stream and the crude benzene / toluene stream based on the enriched aromatic hydrocarbons stream.

[0084] Embodiment 17. The system of any preceding claim, further including an extraction unit positioned downstream from the reformate splitter. A membrane separator of the one or more membrane separators is positioned downstream from the reformate splitter and upstream from the extraction unit, wherein the membrane separator is configured to generate an enrichedbenzene / toluene stream by removing at least the portion of the aromatic hydrocarbons from the crude benzene / toluene stream, and wherein the extraction unit is configured to generate a benzene / toluene product stream based on the enriched benzene / toluene stream.

[0085] Embodiment 18. The system of any preceding claim, further including a xylene splitter positioned downstream from the reformate splitter. A membrane separator of the one or more membrane separators is positioned downstream from the reformate splitter and upstream from the xylene splitter, wherein the membrane separator is configured to generate an enriched xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude xylenes stream, and wherein the xylene splitter is configured to generate a crude para-xylenes stream and a crude ortho-xylenes stream based on the enriched xylene stream.

[0086] Embodiment 19. The system of any preceding claim, further including a xylene splitter positioned downstream from the reformate splitter, wherein the xylene splitter is configured to generate a crude ortho-xylenes stream based on the crude xylenes stream; and an ortho-xylenes column positioned downstream from the xylene splitter. A membrane separator of the one or more membrane separators is positioned downstream from the xylene splitter and upstream from the ortho-xylenes column, wherein the membrane separator is configured to generate an enriched ortho-xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude ortho-xylenes stream, and wherein the xylene splitter is configured to generate an ortho-xylenes product stream based on the enriched ortho-xylenes stream.

[0087] Embodiment 20. The system of any preceding claim, wherein a first membrane separator of the one or more membrane separators is positioned upstream of the reformer, wherein the first membrane separator is configured to generate an enriched naphtha stream by removing at least the portion of aromatic hydrocarbons from the naphtha stream. A second membrane separator of the one or more membrane separators is positioned downstream from the reformer and upstream of the reformate splitter, wherein the membrane separator is configured to generate an enriched aromatics hydrocarbon stream by removing at least the portion of the aromatic hydrocarbons from the reformate stream, and wherein the reformate splitter is configured generate the crude xylenes stream and the crude benzene / toluene stream based on the enriched aromatic hydrocarbons stream.

[0088] Embodiment 21. A system includes a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream includes aromatic hydrocarbons and non-aromatic hydrocarbons. The system also includes a reformate splitter positioned downstream from the reformer, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream. Further, thesystem includes a xylene splitter positioned downstream from the reformate splitter, wherein the xylene splitter is configured to generate a crude ortho-xylenes stream and a crude para-xylenes stream based on the crude xylenes stream. Further still, the system includes one or more membrane separator positioned downstream from the reformer, the xylenes splitter, or both, wherein the one or more membrane separators is configured to remove at least a portion of the aromatic hydrocarbons.

[0089] Embodiment 22. The system of any preceding claim, wherein the one or more membrane separators includes a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude benzene / toluene stream. The one or more membrane separators also includes a second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude xylenes stream.

[0090] Embodiment 23. The system of any preceding claim, wherein the one or more membrane separators includes a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude xylenes stream. The one or more membrane separators also includes a second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude ortho-xylenes stream.

[0091] Embodiment 24. The system of any preceding claim, wherein the one or more membrane separators includes a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude xylenes stream. The one or more membrane separators also include a second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude para-xylenes stream.

[0092] Embodiment 25. The system of any preceding claim, wherein an additional membrane separator of the one or more membrane separators is positioned upstream from an ortho-xylenes column.

[0093] Embodiment 26. The system of any preceding claim, wherein the one or more membrane separators includes a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude ortho-xylenes stream. The one or more membrane separators also includes a second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the ortho-xylenes depleted stream.

[0094] Embodiment 27. The system of any preceding claim, wherein an additional membrane separator of the one or more membrane separators is positioned upstream from the xylene splitter, wherein the additional membrane separator is configured to generate an enriched ortho-xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude ortho-xylenes stream.

[0095] Embodiment 28. The system of any preceding claim, including an ortho-xylenes column positioned downstream from the xylene splitter. A membrane separator of the one or more membrane separators is positioned downstream from the ortho-xylenes column, wherein the membrane separator is configured to generate an enriched heavy aromatics stream by removing at least the portion of the aromatic hydrocarbons from an ortho-xylenes depleted stream.

[0096] Embodiment 29. The system of any preceding claim, wherein the one or more membrane separators positioned upstream from the reformate splitter.

[0097] Embodiment 30. A system includes a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream includes aromatic hydrocarbons and non-aromatic hydrocarbons. The system also includes a reformate splitter positioned downstream from the reformer and fluidly coupled to the reformer along a first flow path, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream. Further, the system includes a second flow path and a third flow path fluidly coupled to the reformer splitter; and one or more membrane separators configured to remove aromatic hydrocarbons from generate an enriched aromatic hydrocarbons stream and a non-aromatic hydrocarbon stream, wherein the one or more membrane separators are positioned along the first flow path, the second flow path, the third flow path, or a combination thereof.

[0098] Embodiment 31. The system of any preceding claim, wherein the second flow path includes one or more of a xylene splitter, an OX column, and a fluid column.

[0099] Embodiment 32. The system of any preceding claim, including a xylene recovery loop fluidly coupled to the second flow path.

[0100] Embodiment 33. The system of any preceding claim, wherein the xylene recovery loop includes a xylene isomerization unit and a deheptanizer unit positioned downstream from the xylene isomerization unit, wherein the one or more membrane separators include an additional membrane separator positioned downstream from the deheptanizer unit.

[0101] Embodiment 34. The system of any preceding claim, wherein an output of the additional membrane separator is recycled upstream of the xylene isomerization unit.

[0102] Embodiment 35. The system of any preceding claim, wherein the third flow path includes an extraction unit configured to generate a benzene / toluene product.

[0103] Embodiment 36. The system of any preceding claim, wherein the one or more membrane separators are a plurality of membrane separators, wherein the plurality of membrane separators is positioned along two or more of the first flow path, the second flow path, or the third flow path.

[0104] This written description uses embodiments / examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other embodiments / examples that occur to those skilled in the art. Such other embodiments / examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

CLAIMS:

1. A system, comprising:one or more membrane separators configured to receive a flow path comprising a naphtha stream, and wherein the one or more membrane separators are configured to produce, based on the naphtha stream, an aromatics rich stream and an enriched naphtha stream, wherein the naphtha stream comprises aromatic hydrocarbons and non-aromatic hydrocarbons.

2. The system of claim 1, further comprising one or more conduits providing the flow path of the naphtha stream to the one or more membrane separators.

3. The system of claim 1, comprising an isomerization unit, wherein the enriched naphtha stream is recycled upstream of the isomerization unit.

4. The system of claim 1, wherein the naphtha stream is generated based on operation of a coker, a fluid catalytic cracker, a hydrocracker, or selective catalytic cracking processes.

5. The system of claim 4, wherein the naphtha stream comprises about 20 to about 70% linear paraffins and isoparaffins.

6. The system of claim 1, wherein the naphtha stream is pretreated to remove olefins.

7. The system of claim 1, wherein a membrane separator of the one or more membrane separators produces the aromatics rich stream and the enriched naphtha stream while operating in accordance with a pervaporation mode.

8. The system of claim 1, wherein a membrane separator of the one or more membrane separators comprises a one-stage membrane system.

9. The system of claim 1 , wherein a membrane separator of the one or more membrane separators comprises a multi-stage membrane system.

10. The system of claim 1, wherein the naphtha stream comprises a SCN-steam cracked stream, a fluid cracked stream, a hydro cracked stream, a virgin naphtha stream, a crackednaphtha stream, an output stream of a coker, a catalytically cracked naphtha stream, or any combination thereof.

11. The system of claim 1, wherein a membrane separator of the one or more membrane separators produces the aromatics rich stream and the enriched naphtha stream while operating in accordance with vacuum conditions.

12. The system of claim 1, further comprising a reformer upstream of the one or more membrane separators along the flow path.

13. The system of claim 1, further comprising a fractionating column disposed along the flow path.

14. A system, comprising:a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream comprises aromatic hydrocarbons and non-aromatic hydrocarbons;a reformate splitter positioned downstream from the reformer, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream; andone or more membrane separators are positioned upstream, downstream, or both from the reformate splitter, wherein the one or more membrane separators is configured to remove at least a portion the aromatic hydrocarbons.

15. The system of claim 14, wherein a membrane separator of the one or more membrane separators is positioned upstream from the reformer, wherein the membrane separator is configured to generate an enriched naphtha stream by removing at least the portion of aromatic hydrocarbons from the naphtha stream, and wherein the reformer is configured to generate the reformate stream based on the enriched naphtha stream.

16. The system of claim 14, wherein a membrane separator of the one or more membrane separators is positioned downstream from the reformer and upstream of the reformate splitter, wherein the membrane separator is configured to generate an enriched aromatics hydrocarbon stream by removing at least the portion of the aromatic hydrocarbons from the reformate stream,and wherein the reformate splitter is configured generate the crude xylenes stream and the crude benzene / toluene stream based on the enriched aromatic hydrocarbons stream.

17. The system of claim 14, further comprising an extraction unit positioned downstream from the reformate splitter; andwherein a membrane separator of the one or more membrane separators is positioned downstream from the reformate splitter and upstream from the extraction unit, wherein the membrane separator is configured to generate an enriched benzene / toluene stream by removing at least the portion of the aromatic hydrocarbons from the crude benzene / toluene stream, and wherein the extraction unit is configured to generate a benzene / toluene product stream based on the enriched benzene / toluene stream.

18. The system of claim 14, further comprising a xylene splitter positioned downstream from the reformate splitter; andwherein a membrane separator of the one or more membrane separators is positioned downstream from the reformate splitter and upstream from the xylene splitter, wherein the membrane separator is configured to generate an enriched xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude xylenes stream, and wherein the xylene splitter is configured to generate a crude para-xylenes stream and a crude ortho-xylenes stream based on the enriched xylene stream.

19. The system of claim 14, comprising:a xylene splitter positioned downstream from the reformate splitter, wherein the xylene splitter is configured to generate a crude ortho-xylenes stream based on the crude xylenes stream;an ortho-xylenes column positioned downstream from the xylene splitter; and wherein a membrane separator of the one or more membrane separators is positioned downstream from the xylene splitter and upstream from the ortho-xylenes column, wherein the membrane separator is configured to generate an enriched ortho-xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude ortho-xylenes stream, and wherein the xylene splitter is configured to generate an ortho-xylenes product stream based on the enriched ortho-xylenes stream.

20. The system of claim 14, wherein a first membrane separator of the one or more membrane separators is positioned upstream of the reformer, wherein the first membrane separatoris configured to generate an enriched naphtha stream by removing at least the portion of aromatic hydrocarbons from the naphtha stream; andwherein a second membrane separator of the one or more membrane separators is positioned downstream from the reformer and upstream of the reformate splitter, wherein the membrane separator is configured to generate an enriched aromatics hydrocarbon stream by removing at least the portion of the aromatic hydrocarbons from the reformate stream, and wherein the reformate splitter is configured generate the crude xylenes stream and the crude benzene / toluene stream based on the enriched aromatic hydrocarbons stream.

21. A system, comprising:a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream comprises aromatic hydrocarbons and non-aromatic hydrocarbons;a reformate splitter positioned downstream from the reformer, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream;a xylene splitter positioned downstream from the reformate splitter, wherein the xylene splitter is configured to generate a crude ortho-xylenes stream and a crude para-xylenes stream based on the crude xylenes stream; andone or more membrane separator positioned downstream from the reformer, the xylenes splitter, or both, wherein the one or more membrane separators is configured to remove at least a portion of the aromatic hydrocarbons.

22. The system of claim 21, wherein the one or more membrane separators comprise:a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude benzene / toluene stream; anda second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude xylenes stream.

23. The system of claim 21, wherein the one or more membrane separators comprise:a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude xylenes stream; anda second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude ortho-xylenes stream.

24. The system of claim 21, wherein the one or more membrane separators comprise: a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude xylenes stream; anda second membrane separator configured to remove a second portion of the aromatic hydrocarbons from the crude para-xylenes stream.

25. The system of claim 24, wherein an additional membrane separator of the one or more membrane separators is positioned upstream from an ortho-xylenes column.

26. The system of claim 24, wherein the one or more membrane separators comprise:a first membrane separator configured to remove a first portion of the aromatic hydrocarbons from the crude ortho-xylenes stream; anda second membrane separator configured to remove a second portion of the aromatic hydrocarbons from an ortho-xylenes depleted stream.

27. The system of claim 24, wherein an additional membrane separator of the one or more membrane separators is positioned upstream from the xylene splitter, wherein the additional membrane separator is configured to generate an enriched ortho-xylenes stream by removing at least the portion of the aromatic hydrocarbons from the crude ortho-xylenes stream.

28. The system of claim 21, comprising an ortho-xylenes column positioned downstream from the xylene splitter; andwherein a membrane separator of the one or more membrane separators is positioned downstream from the ortho-xylenes column, wherein the membrane separator is configured to generate an enriched heavy aromatics stream by removing at least the portion of the aromatic hydrocarbons from an ortho-xylenes depleted stream.

29. The system of claim 28, wherein the one or more membrane separators positioned upstream from the reformate splitter.

30. A system, comprising:a reformer configured to generate a reformate stream based on a naphtha stream, wherein the reformate stream comprises aromatic hydrocarbons and non-aromatic hydrocarbons;a reformate splitter positioned downstream from the reformer and fluidly coupled to the reformer along a first flow path, wherein the reformate splitter is configured to generate a crude xylenes stream and a crude benzene / toluene stream based on the reformate stream;a second flow path and a third flow path fluidly coupled to the reformer splitter; and one or more membrane separators configured to remove aromatic hydrocarbons from generate an enriched aromatic hydrocarbons stream and a non-aromatic hydrocarbon stream, wherein the one or more membrane separators are positioned along the first flow path, the second flow path, the third flow path, or a combination thereof.

31. The system of claim 30, wherein the second flow path comprises one or more of a xylene splitter, an OX column, and a fluid column.

32. The system of claim 30, comprising a xylene recovery loop fluidly coupled to the second flow path.

33. The system of claim 32, wherein the xylene recovery loop comprises a xylene isomerization unit and a deheptanizer unit positioned downstream from the xylene isomerization unit, wherein the one or more membrane separators comprise an additional membrane separator positioned downstream from the deheptanizer unit.

34. The system of claim 33, wherein an output of the additional membrane separator is recycled upstream of the xylene isomerization unit.

35. The system of claim 30, wherein the third flow path comprises an extraction unit configured to generate a benzene / toluene product.

36. The system of claim 30, wherein the one or more membrane separators are a plurality of membrane separators, wherein the plurality of membrane separators is positioned along two or more of the first flow path, the second flow path, or the third flow path.

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