Methods and systems for paraffin isomerization and separation

Abstract

Systems and methods are discussed for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in n-paraffins or iso-paraffins. One method includes the step of contacting a light naphtha feedstock containing C4-7 iso-paraffins with an isomerization catalyst disposed on a retentate side of a molecular sieve membrane. The method includes the step of isomerizing a least a portion of the C4-7 iso-paraffins of the light naphtha feedstock to produce a reaction mixture having an increased content of C4-7 n-paraffins, a portion of the reaction mixture being recycled to continue contacting the isomerization catalyst. The method includes the step of separating the C4-7 n-paraffins of the reaction mixture on a permeate side of the molecular sieve membrane. The method includes the step of collecting an upgraded light naphtha stream that is rich in the C4-7 n-paraffins from the permeate side of the molecular sieve membrane.

Description

METHODS AND SYSTEMS FOR PARAFFIN ISOMERIZATION AND SEPARATIONTECHNICAL FIELD

[0001] The present disclosure generally relates to systems and methods for performing isomerization of C4-7 paraffins of a light hydrocarbon feedstock and for separating linear paraffins (also referred to herein as normal paraffins, n-paraffins, or n-alkanes) from non-linear or branched paraffins (also referred to herein as iso-paraffins or iso-alkanes) for different applications, in which both the isomerization and separation steps are performed using a membrane isomerization reactor. The present disclosure also relates to systems and methods for isomerizing n-paraffins of a light naphtha feedstock into iso-paraffins, and for separating the iso-paraffins to produce an upgraded light naphtha stream for use in formulating gasoline having an enhanced octane rating. The present disclosure relates to systems and methods for isomerizing iso-paraffins of a light naphtha feedstock into n-paraffins, and for separating the n-paraffins to produce an upgraded light naphtha stream for steam cracking to produce an enhanced yield of ethene.BACKGROUND

[0002] The commercial applications for upgraded light hydrocarbon streams (e.g., C4-7 hydrocarbon streams) in refineries, petrochemical facilities, and gas processing plants has increased as the global demand for gasoline and petrochemicals has been steadily rising over the past decade. Many parts of the world have implemented increasingly strict laws, which has resulted in an increased demand for clean fuels. For example, gasoline is assigned an octane rating, also known as a research octane number (RON), that indicates the ability of the gasoline fuel to withstand compression in an internal combustion engine without detonating. In general, the higher the RON of a gasoline fuel, the greater compression the fuel can withstand before detonating. Regulatory agencies may require various grades of gasoline fuel to have a specified RON.

[0003] Ethene and propene are two building blocks for the manufacturing of numerous products, including polyethylene, polypropylene, ethylene oxide, propylene oxide, vinyl chloride, ethylbenzene, alcohols, and so forth. Because ethene is one of the most important, high-value feedstocks of the petrochemical industry, there is an increasing demand for ethene production. Some of the gaseous and liquid hydrocarbon feedstocks (e.g., ethane, naphtha, and gas oil) are now used almost exclusively to generate ethene through steam cracking. Steam cracking, with its high endothermicity and complex product-separation methods, is one of the most energy-consuming processes of the petrochemical industry. The product distribution of steam cracking is impacted by the composition of the hydrocarbon feedstock provided to the steam cracking reactor.SUMMARY

[0004] It is presently recognized that the RON of gasoline fuels can be modified using a light naphtha stream that is rich in branched C4-7 paraffins in the fuel formulation. For example, a light naphtha stream that is rich in iso-paraffins (also referred to herein as isomerate) has an RON between 80 and 93. As such, it is presently recognized that it is desirable to isomerize a light naphtha feedstock that is rich in n-paraffins (or includes a mixture of n-paraffins and iso-paraffins) to produce an upgraded light naphtha stream that is rich in iso-paraffins to serve as a component of a gasoline fuel formulation having enhanced RON.

[0005] It is further presently recognized that steam cracking of a light naphtha stream yields a substantial quantity of ethene when the C4-7 paraffins is rich in normal C4-7 paraffins. For example, it is known that different hydrocarbons have different propensities for forming ethene during steam cracking. For example, a list of hydrocarbon species organized by a descending propensity to form ethene during steam cracking includes: n-paraffins, iso-paraffins, olefins, naphthenes, and aromatics. As such, it is presently recognized that it is desirable to isomerize a light naphtha feedstock that is rich in iso-paraffins (or includes a mixture of iso-paraffins and n-paraffins) to produce an upgraded light naphtha stream that is rich in n-paraffins prior to steam cracking, which maximizes the quantity of ethene produced during steam cracking.

[0006] One way to upgrade light naphtha is to first separate the naphtha into a n-paraffin-rich stream and an iso-paraffin-rich stream. Then, in an isomerization zone, a considerable portion of the iso-paraffins is converted into n-paraffins (or vice versa) in the presence of an isomerization catalyst. A reaction mixture containing both n-paraffins and iso-paraffins is produced during the isomerization process, with the ratio dependent on the alkanes. Typically, fractionation columns are used to separate iso-paraffins and n-paraffins, which significantly raises the capital cost.

[0007] As such, there is a need for finding a better process for converting and separating the isoparaffins in light naphtha from the n-paraffins, or vice versa. Isomerization (also referred to herein as hydroisomerization) generally entails the conversion of a first paraffin species into a second paraffin species with a higher or lower degree of branching while maintaining the same carbon number. Isomerization is typically an equilibrium-limited reaction in which iso-paraffins are converted to n-paraffins, while n-paraffins are simultaneously converted to iso-paraffins, withinthe isomerization reaction mixture. It is presently recognized that removing the desired product (e.g., iso-paraffins or n-paraffins) from the reaction mixture can effectively shift the equilibrium in a desired direction to produce more of the desired product.

[0008] To address these demands in the industry and other shortcomings in the art, Applicant has developed systems and methods for performing isomerization and separation of either n-paraffins or iso-paraffins using a membrane isomerization reactor. The membrane isomerization reactor combines both isomerization and separation into a single hybrid unit. As such, the membrane isomerization reactor enables improved reaction separation efficiencies and lower energy usage compared to other isomerization and separation techniques. By removing one of the isomerization products, the process effectiveness is increased. For example, as noted, when a reaction is equilibrium-constrained, the removal of a product causes the reaction equilibrium to shift in favor of the product side, increasing the reaction conversion. By implementing a separation membrane (e.g., a zeolite separation membrane) that enables molecular sieving and selective adsorption to selectively permeate n-paraffins from a mixture of n-paraffins and iso-paraffins, the membrane isomerization reactor also minimizes the stages involved for product separation, simplifying the process relative to other separation techniques.

[0009] With the foregoing in mind, provided here are methods for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in n-paraffins. In certain examples, the method includes the step of contacting a light naphtha feedstock containing C4-7 isoparaffins with an isomerization catalyst disposed on a retentate side of a molecular sieve membrane. The method includes the step of isomerizing a least a portion of the C4-7 iso-paraffins of the light naphtha feedstock to produce a reaction mixture having an increased content of C4-7 n- paraffins, a portion of the reaction mixture being recycled to continue contacting the isomerization catalyst disposed on the retentate side of the molecular sieve membrane. The method includes the step of separating the C4-7 n-paraffins of the reaction mixture on a permeate side of the molecular sieve membrane. The method includes the step of collecting an upgraded light naphtha stream that is rich in the C4-7 n-paraffins from the permeate side of the molecular sieve membrane.

[0010] In certain examples, the isomerization catalyst contains platinum supported on zeolite. In certain examples, the isomerization catalyst contains platinum impregnated on sulfated zirconia (Pt / ZrCh-SCh2). In certain examples, the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof. In certain examples, the molecular sieve membrane has a pore diameterless than 6 Angstrom (A). In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certain examples, isomerizing includes the steps of heating the light naphtha feedstock to a temperature from about 200 degrees Celsius (°C) to about 400 °C and pressurizing the light naphtha feedstock to a pressure from about 10 bar gauge (barg) to about 50 barg while contacting the isomerization catalyst. In certain examples, the light naphtha feedstock contains at least 50 molar percent (mol. %) iso-paraffins. In certain examples, an n-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an n-paraffin content of the light naphtha feedstock. In certain examples, the method includes the step of steam cracking the upgraded light naphtha stream to produce at least an ethene product stream, in which a yield of the ethene product stream is greater than would be achieved by steam cracking the light naphtha feedstock. In certain examples, the yield of the ethene product stream is at least 5 weight percent (wt. %) greater than would be achieved by steam cracking the light naphtha feedstock.

[0011] Provided here are also methods for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in iso-paraffins. In certain examples, the method includes the step of providing a light naphtha feedstock containing C4-7 n-paraffins to a retentate side of a molecular sieve membrane. The method includes the step of separating the C4-7 n-paraffins of the light naphtha feedstock on a permeate side of the molecular sieve membrane to contact an isomerization catalyst disposed on the permeate side of the molecular sieve membrane. The method includes the step of isomerizing a least a portion of the separated C4-7 n-paraffins to produce a reaction mixture having an increased content of C4-7 iso-paraffins, the reaction mixture being recycled to the retentate side of the molecular sieve membrane. The method includes the step of collecting an upgraded light naphtha stream that is rich in the C4-7 iso-paraffins from the retentate side of the molecular sieve membrane.

[0012] In certain examples, the isomerization catalyst contains platinum supported on zeolite. In certain examples, the isomerization catalyst contains platinum impregnated on sulfated zirconia (Pt / ZrCh-SCh2). In certain examples, the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof. In certain examples, the molecular sieve membrane has a pore diameter less than 6 A. In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM- 5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certain examples, isomerizing includes the steps of heating the light naphtha feedstock to a temperature from about200 °C to about 400 °C and pressurizing the light naphtha feedstock to a pressure from about 10 barg to about 50 barg while contacting the isomerization catalyst. In certain examples, the light naphtha feedstock contains at least 50 mol. % n-paraffins. In certain examples, an iso-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an iso-paraffin content of the light naphtha feedstock. In certain examples, the method includes the step of combining the upgraded light naphtha stream with a gasoline stream having a first research octane number (RON) to produce a gasoline product stream having a second RON that is greater than the first RON. In certain examples, the second RON is at least 5 % greater than the first RON.

[0013] Provided here are systems for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in n-paraffins. In certain examples, the system includes a membrane isomerization reactor. The membrane isomerization reactor includes a molecular sieve membrane having a retentate side and a permeate side. The membrane isomerization reactor includes an isomerization catalyst disposed on the retentate side of the molecular sieve membrane and configured to receive and isomerize a light naphtha feedstock containing C4-7 iso-paraffins to produce a reaction mixture having an increased content of C4-7 n-paraffins, the molecular sieve membrane being configured to separate the C4-7 n-paraffins of the reaction mixture on the permeate side of the molecular sieve membrane. The membrane isomerization reactor includes a recycle flow path configured to recycle a portion of the reaction mixture back to the isomerization catalyst disposed on the retentate side of the molecular sieve membrane, the membrane isomerization reactor being configured to collect an upgraded light naphtha stream that is rich in the C4-7 n- paraffins from the permeate side of the molecular sieve membrane.

[0014] In certain examples, the isomerization catalyst is a fixed-bed, bifunctional catalyst that is separate and distinct from the molecular sieve membrane. In certain examples, the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof. In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certain examples, the molecular sieve membrane has a pore dimeter less than 6 A. In certain examples, the molecular sieve membrane includes zeolite having a uniform one-dimensional, two-dimensional, and three-dimensional structure with 8-membered, 10- membered, 12-membered rings defining a pore dimeter less than 6 A. In certain examples, the light naphtha feedstock contains at least 50 mol. % iso-paraffins, and an n-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an n-paraffin content of the lightnaphtha feedstock. In certain examples, the system includes a steam cracker in fluid communication with the membrane isomerization reactor and configured to receive and steam crack the upgraded light naphtha stream to produce at least an ethene product stream, in which a yield of the ethene product stream is at least 5 wt. % greater than would be achieved by steam cracking the light naphtha feedstock. In certain examples, the system includes a controller configured to provide control signals to flow control devices of the membrane isomerization reactor to maintain a pressure gradient between the retentate side and the permeate side of the molecular sieve membrane. In some examples, the pressure gradient is greater than 0 barg and less than 5 barg, and in other examples, the pressure gradient is greater than 10 barg and less than 50 barg.

[0015] Provided here are systems for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in iso-paraffins. In certain examples, the system includes a membrane isomerization reactor. The membrane isomerization reactor includes a molecular sieve membrane having a retentate side and a permeate side, the molecular sieve membrane being configured to contact a light naphtha feedstock containing C4-7 n-paraffins on the retentate side and to separate the C4-7 n-paraffins of the light naphtha feedstock on the permeate side. The membrane isomerization reactor includes an isomerization catalyst disposed on the permeate side of the molecular sieve membrane and configured isomerize the separated C4-7 n-paraffins to produce a reaction mixture having an increased content of C4-7 iso-paraffins. The membrane isomerization reactor includes a recycle flow path configured to recycle the reaction mixture to the retentate side of the molecular sieve membrane, the membrane isomerization reactor being configured to collect an upgraded light naphtha stream that is rich in the C4-7 iso-paraffins from the retentate side of the molecular sieve membrane.

[0016] In certain examples, the isomerization catalyst is a fixed-bed, bifunctional catalyst that is separate and distinct from the molecular sieve membrane. In certain examples, the molecular sieve contains zeolite, SAPO-x, or a combination thereof, and the molecular sieve membrane has a pore dimeter less 6 A. In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certain examples, the molecular sieve membrane contains zeolite having a uniform one dimensional, two dimensional, and three-dimensional structure with 8-membered, 10-membered, 12-membered rings defining a pore dimeter less than 6 A. In certain examples, the light naphtha feedstock contains at least 50mol. % n-paraffins, and an iso-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an iso-paraffin content of the light naphtha feedstock. In certain examples, the system includes a fluid catalytic cracker configured to receive and crack a hydrocarbon feedstock to produce a gasoline stream having a first research octane number (RON), in which the upgraded light naphtha stream is configured to be combined with the gasoline stream to produce a gasoline product stream having a second RON that is at least 5 % greater than greater than the first RON. In certain examples, the system includes a controller configured to provide control signals to flow control devices of the membrane isomerization reactor to maintain a pressure gradient between the retentate side and the permeate side of the molecular sieve membrane. In some examples, the pressure gradient is greater than 0 barg and less than 5 barg, and in other examples, the pressure gradient is greater than 10 barg and less than 50 barg.

[0017] Provided here are also methods for operating a membrane isomerization reactor to produce an upgraded light naphtha stream that is rich in n-paraffins. In certain examples, the method includes the step of contacting a light naphtha feedstock containing C4-7 iso-paraffins with an isomerization catalyst of the membrane isomerization reactor, the isomerization catalyst disposed on a retentate side of a molecular sieve membrane of the membrane isomerization reactor. The method includes the step of isomerizing a least a portion of the C4-7 iso-paraffins of the light naphtha feedstock to produce a reaction mixture having an increased content of C4-7 n-paraffins, a portion of the reaction mixture being recycled to continue contacting the isomerization catalyst disposed on the retentate side of the molecular sieve membrane. The method includes the step of separating the C4-7 n-paraffins of the reaction mixture on a permeate side of the molecular sieve membrane, thereby to shift an equilibrium of the isomerization on the retentate side of the molecular sieve membrane towards the production of additional C4-7 n-paraffins. The method includes the step of collecting an upgraded light naphtha stream that is rich in the C4-7 n-paraffins from the permeate side of the molecular sieve membrane.

[0018] In certain examples, the isomerization catalyst contains platinum supported on zeolite. In certain examples, the isomerization catalyst contains platinum impregnated on sulfated zirconia (Pt / ZrCh-SCh2). In certain examples, the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof. In certain examples, the molecular sieve membrane has a pore diameter less than 6 Angstrom (A). In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certainexamples, isomerizing includes the steps of heating the light naphtha feedstock to a temperature from about 200 degrees Celsius (°C) to about 400 °C and pressurizing the light naphtha feedstock to a pressure from about 10 bar gauge (barg) to about 50 barg while contacting the isomerization catalyst. In certain examples, the light naphtha feedstock contains at least 50 molar percent (mol. %) iso-paraffins. In certain examples, an n-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an n-paraffin content of the light naphtha feedstock. In certain examples, the method includes the step of steam cracking the upgraded light naphtha stream to produce at least an ethene product stream, in which a yield of the ethene product stream is greater than would be achieved by steam cracking the light naphtha feedstock. In certain examples, the yield of the ethene product stream is at least 5 weight percent (wt. %) greater than would be achieved by steam cracking the light naphtha feedstock.

[0019] Provided here are also methods for operating a membrane isomerization reactor to produce an upgraded light naphtha stream that is rich in iso-paraffins. In certain examples, the method includes the step of providing a light naphtha feedstock containing C4-7 n-paraffins to a retentate side of a molecular sieve membrane of the membrane isomerization reactor. The method includes the step of separating the C4-7 n-paraffins of the light naphtha feedstock on a permeate side of the molecular sieve membrane to contact an isomerization catalyst of the membrane isomerization reactor, the isomerization catalyst disposed on the permeate side of the molecular sieve membrane. The method includes the step of isomerizing a least a portion of the separated C4-7 n-paraffins to produce a reaction mixture having an increased content of C4-7 iso-paraffins, the reaction mixture being recycled to the retentate side of the molecular sieve membrane, wherein the separating of the C4-7 n-paraffins prior to isomerization shifts an equilibrium of the isomerization on the retentate side of the molecular sieve membrane towards the production of additional C4-7 iso-paraffins. The method includes the step of collecting an upgraded light naphtha stream that is rich in the C4-7 isoparaffins from the retentate side of the molecular sieve membrane.

[0020] In certain examples, the isomerization catalyst contains platinum supported on zeolite. In certain examples, the isomerization catalyst contains platinum impregnated on sulfated zirconia (Pt / ZrCh-SCh2). In certain examples, the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof. In certain examples, the molecular sieve membrane has a pore diameter less than 6 A. In some examples, the molecular sieve membrane contains Ferrierite zeolite, ZSM- 5 zeolite, Beta zeolite, Mordonite zeolite, or combinations thereof. In certain examples,isomerizing includes the steps of heating the light naphtha feedstock to a temperature from about 200 °C to about 400 °C and pressurizing the light naphtha feedstock to a pressure from about 10 barg to about 50 barg while contacting the isomerization catalyst. In certain examples, the light naphtha feedstock contains at least 50 mol. % n-paraffins. In certain examples, an iso-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an iso-paraffin content of the light naphtha feedstock. In certain examples, the method includes the step of combining the upgraded light naphtha stream with a gasoline stream having a first research octane number (RON) to produce a gasoline product stream having a second RON that is greater than the first RON. In certain examples, the second RON is at least 5 % greater than the first RON.

[0021] Still other aspects and advantages of these exemplary embodiments and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they may be practiced.

[0023] FIG. 1 is a diagrammatic representation of an embodiment of system that includes a membrane isomerization reactor that enables the isomerization of a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in n-paraffins, and includes a steam cracker that enables stream cracking of the upgraded light naphtha stream to produce ethene.

[0024] FIG. 2 is a diagrammatic representation of an embodiment of system that includes a membrane isomerization reactor that enables the isomerization of a light naphtha feedstock toproduce an upgraded light naphtha stream that is rich in iso-paraffins, which is used to produce a gasoline product stream having a suitably high RON.

[0025] FIG. 3 is a diagrammatic representation of an embodiment of the membrane isomerization reactor of FIG. 1.

[0026] FIG. 4 is a diagrammatic representation of an embodiment of the membrane isomerization reactor of FIG. 2.DETAILED DESCRIPTION

[0027] The present disclosure describes various embodiments related to processes, methods, and systems for upgrading a light naphtha feedstock to produce an upgraded light naphtha stream that is rich in n-paraffins or iso-paraffins using a membrane isomerization reactor. Further embodiments may be described and disclosed.

[0028] In the following description, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not have been described in particular detail in order not to unnecessarily obscure the various embodiments. Additionally, illustrations of the various embodiments may omit certain features or details in order to not obscure the various embodiments.

[0029] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in certain embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0030] The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0031] The term “about” refers to a range of values including the specified value, which a person of ordinary skill in the art would consider reasonably similar to the specified value. In embodiments, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting embodiment, when the term “about” is used with a particular value, then “about” refers to a range extending to ±10% of the specified value, alternatively ±5% of the specified value, or alternatively ±1% of the specified value, or alternatively ±0.5% of the specified value. In embodiments, “about” refers to the specified value.

[0032] The terms “reducing,” “reduced,” or any variation thereof, when used in the claims and / or the specification includes any measurable decrease or complete removal to achieve a desired result.

[0033] The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of a component in 100 grams of the material is 10 wt.% of such component.

[0034] As used herein, the term “Cx-y compounds,” in which x and y are positive integer values, refers to hydrocarbon-based compounds, each compound containing between x and y carbon atoms, x and y inclusive. For example, a C4-7 stream refers to a mixture that substantially contains or entirely contains hydrocarbon-based compounds, each compound containing 4, 5, 6, or 7 carbon atoms.

[0035] As used herein, when a first component is described as receiving (or being configured to receive) a stream from a second component, or when a first component is described as providing (or being configured to provide) a stream to a second component, the first and second components may be alternatively described as being in fluid communication with one another. It may be appreciated that, for the various streams discussed herein, a given stream substantially contains the compound or class of compounds in the name of the stream (e.g., an ethene product stream substantially contains ethene, a C4-7 hydrocarbon stream substantially contains C4, C5, Ce, and C7 hydrocarbons), and the stream may also include other components.

[0036] The term “substantially contains” means that the mixture includes at least 50 mol. % of the named compound or class of compounds, such as at least 60 mol. %, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, at least 98 mol. %, at least 99 mol. %, or 100 mol. %, or any sub-ranges there between.

[0037] The term “enriched” or “rich” or their variations mean an amount of at least generally about 50 mol. % of a compound or class of compounds in a stream.

[0038] Disclosed herein are systems and methods for performing isomerization and separation of either n-paraffins or iso-paraffins using a membrane isomerization reactor. The membrane isomerization reactor is combines both isomerization and separation into a single hybrid unit. As such, the membrane isomerization reactor enables improved reaction separation efficiencies and lower energy usage compared to other isomerization and separation techniques. By removing one of the isomerization products, the process effectiveness is increased. For example, as noted, whena reaction is equilibrium-constrained, the removal of a product causes the reaction equilibrium to shift in favor of the product side, increasing the reaction conversion. By implementing a molecular sieve separation membrane that enables molecular sieving and selective adsorption to selectively permeate n-paraffins from a mixture of n-paraffins and iso-paraffins, the membrane isomerization reactor also minimizes the stages involved for product separation, simplifying the process relative to other separation techniques.

[0039] FIG. 1 is a diagrammatic representation of an embodiment of system 100 that includes a membrane isomerization reactor 102 that enables the isomerization of a light naphtha feedstock 104 to produce an upgraded light naphtha stream 106 that is rich in n-paraffins. The system 100 also includes a steam cracker 108 that enables stream cracking of the upgraded light naphtha stream to produce an ethene product stream 110. The light naphtha feedstock 104 contains C4-7 paraffins, including C4-7 iso-paraffins. In some embodiments, the light naphtha feedstock 104 is rich in or consists essentially of C4-7 iso-paraffins.

[0040] As noted herein, it is presently recognized that C4-7 iso-paraffins have a lower propensity to form ethene during steam cracking, while C4-7 n-paraffins demonstrate a greater propensity to form ethene during steam cracking. As such, for the embodiment of the system 100 illustrated in FIG. 1, the light naphtha feedstock 104 is provided to the membrane isomerization reactor 102. An embodiment of the membrane isomerization reactor 102 is discussed in detail below with respect to FIG. 3. In general, the light naphtha feedstock 104 is first mixed with hydrogen gas (H2) 112 before contacting an isomerization catalyst 114 of the membrane isomerization reactor 102. In some embodiments, the isomerization reaction occurs at a pressure from about 10 bar gauge (barg) to about 40 barg, and at a temperature from about 200 degrees Celsius (°C) to about 400 °C. The isomerization catalyst 114 of the membrane isomerization reactor 102 isomerizes a substantial portion (e.g., up to about 90 mol. %) of the C4-7 iso-paraffins present within the light naphtha feedstock 104 into a reaction mixture that is enriched in C4-7 n-paraffins.

[0041] For the embodiment of the system 100 illustrated in FIG. 1, the isomerization catalyst 114 includes a fixed-bed, bifunctional catalyst. In some embodiments, the isomerization catalyst 114 includes platinum supported on zeolite, or platinum impregnated on sulfated zirconia (Pt / ZrCh- SO42’). The reaction mixture contacts a separation membrane 116 of the membrane isomerization reactor 102, which selectively blocks or restricts the C4-7 iso-paraffins from leaving the membrane isomerization reactor 102, while selectively allowing the C4-7 n-paraffins to advance, yielding theupgraded light naphtha stream 106 that is rich in n-paraffins. In some embodiments, the separation membrane 116 is a molecular sieve membrane. In some embodiments, the molecular sieve membrane is zeolite or a SAPO-x membrane (e.g., Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordenite zeolite). In some embodiments, the separation membrane 116 is formed from zeolites and has a uniform one dimensional, two dimensional, and three-dimensional structure with 8- membered, 10-membered, 12-membered rings having pore dimeter less than 6 Angstrom (A). In some embodiments, the upgraded light naphtha stream 106 contains at least 50 mol. % n-paraffins, at least 60 mol. % n-paraffins, at least 70 mol. % n-paraffins, at least 80 mol. % n-paraffins, at least 90 mol. % n-paraffins, at least 95 mol. % n-paraffins, at least 98 mol. % n-paraffins, or at least 99 mol. % n-paraffins.

[0042] For the embodiment of the system 100 illustrated in FIG. 1, the upgraded light naphtha stream 106 is directed to the steam cracker 108, which cracks the upgraded light naphtha stream 106 at elevated temperatures in the presence of steam to produce a steam cracked product stream that is directed to the downstream separation section 118 for separation into the ethene product stream 110, as well as other product streams 120. The downstream separation section 118 includes any suitable number of separation units (e.g., distillation columns, fractionating columns), such as a C2 / C3 separator, that separates the ethene product stream 110 and the other product streams 120 from the steam cracked product stream. As noted, the quantity of the ethene product stream 110 is substantially greater than the quantity of ethene that would be produced by steam cracking the light naphtha feedstock 104 instead of the upgraded light naphtha stream 106. For example, the quantity of the ethene product stream 110 may be at least 1 wt. % greater, at least 5 wt. % greater, at least 20 wt. % greater, at least 30 wt. % greater, or at least 50 wt. % greater than the quantity of ethene that would be produced by steam cracking the light naphtha feedstock 104 instead of the upgraded light naphtha stream 106.

[0043] FIG. 2 is a diagrammatic representation of an embodiment of system 200 that includes a membrane isomerization reactor 202 that enables the isomerization of a light naphtha feedstock 204 to produce an upgraded light naphtha stream 206 that is rich in iso-paraffins, which is used to produce a gasoline product stream 208 having a suitably high RON. The system 200 includes a fluid catalytic cracker (FCC) 210 that receives and catalytically cracks a hydrocarbon feedstock 212 at elevated temperatures to produce a fluid catalytically cracked stream that is directed to the downstream separation section 214 for processing and / or separation. In some embodiments, thehydrocarbon feedstock 212 contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. In some embodiments, the FCC 210 includes a reactor that receives and contacts the hydrocarbon feedstock 212 with a FCC catalyst (e.g., a ZSM-5-based cracking catalyst) at elevated temperatures (e.g., from about 450 °C to about 650 °C) to yield the FCC cracked stream. In some embodiments, the downstream separation section 214 includes any suitable number of reactors and / or separation columns that process and / or separate the received FCC cracked stream into a number of streams, including a gasoline stream 216. In some embodiments, the downstream separation section 214 includes a C2 / C3 splitter, a methyl tert-butyl ether (MTBE) reactor, a but-l-ene (Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, an acetylene hydrogenation reactor, any other suitable separation column (e.g., distillation column, fractional distillation column, deethanizer, depropanizer, debutanizer, depentanizer, C2 / C3 splitter, and so forth), or any combination thereof. However, the gasoline stream 216 may not have a desired RON to comply with particular regulations in certain jurisdictions. As such, it is presently recognized that it is desirable to combine the gasoline stream 216 with a suitable quantity of C4-7 iso-paraffins from the upgraded light naphtha stream 206 to adjust the RON of the gasoline stream 216 to produce the gasoline product stream 208 having an enhanced RON.

[0044] For the embodiment of the system 200 illustrated in FIG. 2, the membrane isomerization reactor 202 enables the isomerization of the light naphtha feedstock 204 to produce the upgraded light naphtha stream 206 that is rich in iso-paraffins. The light naphtha feedstock 204 contains C4- 7 paraffins, including C4-7 n-paraffins. In some embodiments, the light naphtha feedstock 204 is rich in or consists essentially of C4-7 n-paraffins. An embodiment of the membrane isomerization reactor 202 is discussed in detail below with respect to FIG. 4. In general, the light naphtha feedstock 204 is first mixed with hydrogen gas (H2) 218 before contacting a separation membrane 222 of the membrane isomerization reactor 202. The separation membrane 222 selectively allows C4-7 n-paraffins to traverse to a permeate side of the separation membrane 222 to reach an isomerization catalyst 220 of the membrane isomerization reactor 202 for isomerization, while selectively blocking or restricting the C4-7 iso-paraffins on a retentate side of the separation membrane 222. In some embodiments, the isomerization reaction occurs at a pressure from about 10 barg to about 50 barg, and at a temperature from about 200 °C to about 400 °C. The isomerization catalyst 220 of the membrane isomerization reactor 202 isomerizes a substantialportion (e.g., up to about 90 mol. %) of the C4-7 n-paraffins present within the light naphtha feedstock 204 into C4-7 iso-paraffins. The upgraded light naphtha stream 206 that is rich in isoparaffins is collected from a retentate side of the separation membrane 222.

[0045] For the embodiment of the system 200 illustrated in FIG. 2, the isomerization catalyst 220 includes a fixed-bed, bifunctional catalyst. In some embodiments, the isomerization catalyst 220 includes platinum supported on zeolite, or platinum impregnated on sulfated zirconia (Pt / ZrCh- SO42’). In some embodiments, the separation membrane 222 is a molecular sieve membrane that contains zeolite, SAPO-x, or a combination thereof (e.g., Ferrierite zeolite, ZSM-5 zeolite, Beta zeolite, Mordenite zeolite). In some embodiments, the separation membrane 222 is formed from zeolites and has a uniform one dimensional, two dimensional, and three-dimensional structure with 8-membered, 10-membered, 12-membered rings having pore dimeter less than 6 A. In some embodiments, the upgraded light naphtha stream 206 contains at least 50 mol. % iso-paraffins, at least 60 mol. % iso-paraffins, at least 70 mol. % iso-paraffins, at least 80 mol. % iso-paraffins, at least 90 mol. % iso-paraffins, at least 95 mol. % iso-paraffins, at least 98 mol. % iso-paraffins, or at least 99 mol. % iso-paraffins. In some embodiments, the amount of the upgraded light naphtha stream 206 in the gasoline product stream 208 is greater than 10 wt. %, greater than 20 wt. %, greater than 30 wt. %, greater than 40 wt. %, or greater than 50 wt. %. In some embodiments, the RON of the gasoline product stream 208 is at least 5% greater, at least 10% greater, at least 15% greater, or at least 20% greater than the RON of the gasoline stream 216 prior to the addition of the upgraded light naphtha stream 206.

[0046] For the embodiments discussed herein, the aforementioned isomerization reaction conditions can result in complex isomerization reaction mixtures. In some examples, the light naphtha feedstock 104 or 204 may include one or more of n-butane, iso-butane, n-pentane, one or more iso-pentanes (e.g., neo-pentane), n-hexane, one or more iso-hexanes, n-heptane, and one or more iso-heptanes. For example, when the light naphtha feedstock 104 or 204 includes n-butane or iso-butane, the reaction mixture may include unreacted n-butane or iso-butane, the desired isomerized butane product (e.g., n-butane or iso-butane), and one or more by-products (e.g., methane, ethane, and propane). When the light naphtha feedstock 104 or 204 includes n-pentane or iso-pentanes, the reaction mixture may include unreacted n-pentane or iso-pentanes, the desired isomerized pentane product (e.g., n-pentane or iso-pentanes), and one or more by-products (e.g., methane, ethane, propane, and butane isomers). When the light naphtha feedstock 104 or 204includes n-hexane or one or more iso-hexanes, the reaction mixture may include unreacted n- hexane or iso-hexanes, the desired isomerized hexane product (e.g., n-hexane or iso-hexanes), and one or more by-products (e.g., methane, ethane, propane, butane isomers, and pentane isomers). When the light naphtha feedstock 104 or 204 includes n-heptane or one or more iso-heptanes, the reaction mixture may include unreacted n-heptane or iso-heptanes, the desired isomerized heptane product (e.g., n-heptane or iso-heptanes), and one or more by-products (e.g., methane, ethane, propane, butane isomers, pentane isomers, and hexane isomers).

[0047] FIG. 3 is a diagrammatic representation of an embodiment of the membrane isomerization reactor 102 of FIG. 1. As noted, the membrane isomerization reactor 102 is designed to receive and isomerize the light naphtha feedstock 104 that contains iso-paraffins and then separate out the upgraded light naphtha stream 106 that is rich in n-paraffins from the isomerization reaction mixture. The membrane isomerization reactor 102 includes the isomerization catalyst 114 and the separation membrane 116, as discussed above, positioned within a body 302 of the membrane isomerization reactor 102. While both the isomerization catalyst 114 and the separation membrane 116 may include zeolites, it may be appreciated that the isomerization catalyst 114 is distinct from and is not integrated into (e.g., loaded into) the separation membrane 116, which enables separate selection of zeolites for the isomerization catalyst 114 and the separation membrane 116 to individually optimize the isomerization and separation aspects. In some embodiments, the membrane isomerization reactor 102 is implemented using a cylindrical body 302, in which the isomerization catalyst 114 is disposed along a longitudinal axis of the body 302 and the separation membrane 116 extends radially around the isomerization catalyst 114, defining a flow path 304 (e.g., an annular flow path) between the separation membrane 116 and the body 302.

[0048] For the embodiment of the membrane isomerization reactor 102 illustrated in FIG. 3, the light naphtha feedstock 104 is introduced directly to the isomerization catalyst 114 of the membrane isomerization reactor 102. Upon contacting the isomerization catalyst 114, iso-paraffins within the light naphtha feedstock 104 are desirably isomerized into n-paraffins. N-paraffins that were present within the light naphtha feedstock 104 or that are formed via isomerization of isoparaffins present within the light naphtha feedstock 104 have a sufficiently small kinetic diameter to traverse from a retentate side 306 to a permeate side 308 of the separation membrane 116. In contrast, the larger kinetic diameter of iso-paraffins of the light naphtha feedstock 104 that have yet not been isomerized into n-paraffins (and iso-paraffin by-products from undesiredisomerization of n-paraffins of the light naphtha feedstock 104), blocks or inhibits the iso-paraffins from traversing from a retentate side 306 to a permeate side 308 of the separation membrane 116. As such, the separation membrane 116 facilitates driving the equilibrium of the isomerization reaction toward the formation of n-paraffins by enabling n-paraffins to preferentially traverse the separation membrane 116 while retaining a substantial portion of iso-paraffins near the isomerization catalyst 114. The n-paraffin enriched stream that traverses the separation membrane 116 to reach the flow path 304 exits the membrane isomerization reactor 102 as the upgraded light naphtha stream 106. Additionally, after traversing the length of isomerization catalyst 114, the remainder of the light naphtha feedstock 104 that contains iso-paraffins and that does not traverse the separation membrane 116 is recycled along the recycling flow path 310, where it is combined with fresh light naphtha feedstock 104 and H2 112 before making another pass through the membrane isomerization reactor 102.

[0049] For the embodiment of the membrane isomerization reactor 102 illustrated in FIG. 3, it is presently recognized that the separation membrane 116 does not enable a perfect separation, and that a limited quantity of iso-paraffins may traverse the separation membrane 116 to become part of the upgraded light naphtha stream 106. It is further presently recognized that, by controlling the pressure gradient across the separation membrane 116, the amount of iso-paraffins that traverse the separation membrane 116 can be minimized. With this in mind, the embodiment of the membrane isomerization reactor 102 illustrated in FIG. 3 includes a controller 312 that is designed to control operation of the membrane isomerization reactor 102. The controller 312 includes at least one processor 314 (e.g., a central processing unit (CPU), graphics processing unit (GPU), application-specific integrated circuit (ASIC)) and at least one memory 316 (e.g., random access memory (RAM), read-only memory (ROM), flash memory, solid state disk (SSD)). For the illustrated embodiment, the memory 316 stores instructions that are executed by the processor 314 to process measurement data collected by analyzers and / or sensors disposed throughout the membrane isomerization reactor 102 to determine operational parameters of the reactor and to provide suitable control signals to modify the operational parameters of the reactor to ensure that they remain within pre-defined ranges.

[0050] For the embodiment of the illustrated in FIG. 3, the controller 312 is communicatively connected to various components of the membrane isomerization reactor 102 (e.g., via a suitable wired or wireless connection) to receive data indicative of current settings and operationalparameters of the membrane isomerization reactor 102 and to provide control signals to modify operation of the membrane isomerization reactor 102. For the illustrated embodiment, these components include a first flow analyzer 318 that measures the amount of iso-paraffins or the ratio of iso-paraffins to n-paraffins in the light naphtha feedstock 104 and a second flow analyzer 320 that measures the amount of iso-paraffins or the ratio of iso-paraffins to n-paraffins in the upgraded light naphtha stream 106. In some embodiments, using these measurements, the controller 312 determines an efficacy of the isomerization and separation provided by the membrane isomerization reactor 102 with respect to enriching the n-paraffin content.

[0051] For the embodiment illustrated in FIG. 3, the controller 312 is further communicatively connected to sensors of the membrane isomerization reactor 102 (e.g., pressure sensors, temperature sensors, flow sensors, or a combination thereof), including a first sensor 322 positioned on the retentate side 306 of the separation membrane 116 and a second sensor 324 positioned on the permeate side 308 of the separation membrane 116, that measure conditions (e.g., pressure, temperature, flow rate, or a combination thereof) within the membrane isomerization reactor 102 during operation. For the illustrated embodiment, the controller 312 is communicatively connected to conditionally provide control signals to modify the operation of various flow control devices based on the measurements received from the flow analyzers 318, 320 and the sensors 322, 324. For the illustrated embodiment, the flow control devices include: a flow control device 326 that controls the flow of the light naphtha feedstock 104 into the membrane isomerization reactor 102, the flow control device 328 that controls the flow of H2 112 into the membrane isomerization reactor 102, flow control device 330 that controls the flow of the upgraded light naphtha stream 106 from the membrane isomerization reactor 102, and flow control device 332 that controls the flow of the recycled iso-paraffin-containing reaction mixture back to the membrane isomerization reactor 102. In some embodiments, the controller 312 provides suitable control signals to modify operation of the flow control devices to ensure that the pressure gradient between the retentate side 306 and the permeate side 308 of the separation membrane 116 is greater than 0 bar gauge (barg) and less than 5 barg (or from about 10 barg to about 50 barg) to enable the membrane isomerization reactor 102 to produce the upgraded light naphtha stream 106 at a sufficiently high production rate and that is sufficiently enriched with n-paraffins to promote ethene production during steam cracking, as discussed above.

[0052] FIG. 4 is a diagrammatic representation of an embodiment of the membrane isomerization reactor 202 of FIG. 2. As noted, the membrane isomerization reactor 202 is designed to receive and isomerize the light naphtha feedstock 204 that contains n-paraffins, and then separate out the upgraded light naphtha stream 206 that is rich in iso-paraffins from the isomerization reaction mixture. The membrane isomerization reactor 202 includes the isomerization catalyst 220 and the separation membrane 222, as discussed above, positioned within a body 402 of the membrane isomerization reactor 202. While both the isomerization catalyst 220 and the separation membrane 222 may include zeolites, it may be appreciated that the isomerization catalyst 220 is distinct from and is not integrated into (e.g., loaded into) the separation membrane 222, which enables separate selection of zeolites for the isomerization catalyst 220 and the separation membrane 222 to individually optimize the isomerization and separation aspects. In some embodiments, the membrane isomerization reactor 202 is implemented using a cylindrical body 402, in which the isomerization catalyst 220 is disposed along a longitudinal axis of the body 402 and the separation membrane 222 extends radially around the isomerization catalyst 220, defining a flow path 404 (e.g., an annular flow path) between the separation membrane 222 and the body 402.

[0053] For the embodiment of the membrane isomerization reactor 202 illustrated in FIG. 4, the light naphtha feedstock 204 is introduced to the flow path 404 of the membrane isomerization reactor 202. N-paraffins that are present within the light naphtha feedstock 204 have a sufficiently small kinetic diameter to traverse from a retentate side 406 to a permeate side 408 of the separation membrane 222 to reach the isomerization catalyst 220. Upon contacting the isomerization catalyst 220, n-paraffins within the light naphtha feedstock 204 are desirably isomerized into iso-paraffins. In contrast, the larger kinetic diameter of iso-paraffins of the light naphtha feedstock 204 blocks or inhibits the iso-paraffins from traversing from the retentate side 406 to the permeate side 408 of the separation membrane 222. As such, the separation membrane 222 facilitates driving the equilibrium of the isomerization reaction toward the formation of iso-paraffins by enabling n- paraffins to preferentially traverse the separation membrane 222 while retaining a substantial portion of iso-paraffins within the flow path 404, and this iso-paraffin-enriched stream exits the membrane isomerization reactor 202 as the upgraded light naphtha stream 206. Additionally, after traversing the isomerization catalyst 220, the reaction mixture that contains n-paraffins is recycled along the recycling flow path 410, where it is combined with fresh light naphtha feedstock 204and H2 218 before being delivered to the flow path 404 of the membrane isomerization reactor 102

[0054] For the embodiment of the membrane isomerization reactor 202 illustrated in FIG. 4, it is presently recognized that the separation membrane 222 does not enable a perfect separation, and that a limited quantity of iso-paraffins may traverse the separation membrane 222, while a limited quantity of n-paraffins may not traverse the separation membrane 222 to reach the isomerization catalyst 220 and may instead become incorporated into the upgraded light naphtha stream 206. It is further presently recognized that, by controlling the pressure gradient across the separation membrane 222, the amount of iso-paraffins that traverse the separation membrane 222 and / or the amount of n-paraffins that fail to traverse the separation membrane 222 can be minimized. With this in mind, the embodiment of the membrane isomerization reactor 202 illustrated in FIG. 4 includes a controller 412 that is designed to control operation of the membrane isomerization reactor 202. The controller 412 includes at least one processor 414 (e.g., a CPU, GPU, ASIC) and at least one memory 416 (e.g., RAM, ROM, flash memory, SSD). For the illustrated embodiment, the memory 416 stores instructions that are executed by the processor 414 to process measurement data collected by analyzers and / or sensors disposed throughout the membrane isomerization reactor 202 to determine operational parameters of the reactor, and to provide suitable control signals to modify the operational parameters of the reactor to ensure that they remain within predefined ranges.

[0055] For the embodiment of the illustrated in FIG. 4, the controller 412 is communicatively connected to various components of the membrane isomerization reactor 202 (e.g., via a suitable wired or wireless connection) to receive data indicative of current settings and operational parameters of the membrane isomerization reactor 202 and to provide control signals to modify operation of the membrane isomerization reactor 202. For the illustrated embodiment, these components include a first flow analyzer 418 that measures the amount of n-paraffins or the ratio of n-paraffins to iso-paraffins in the light naphtha feedstock 204 and a second flow analyzer 320 that measures the amount of n-paraffins or the ratio of n-paraffins to iso-paraffins in the upgraded light naphtha stream 206. In some embodiments, using these measurements, the controller 412 determines an efficacy of the isomerization and separation provided by the membrane isomerization reactor 202 with respect to enriching the iso-paraffin content.

[0056] For the embodiment illustrated in FIG. 4, the controller 412 is further communicatively connected to sensors of the membrane isomerization reactor 202 (e.g., pressure sensors, temperature sensors, flow sensors, or a combination thereof), including a first sensor 422 positioned on the retentate side 406 of the separation membrane 222 and a second sensor 424 positioned on the permeate side 408 of the separation membrane 222, that measure conditions (e.g., pressure, temperature, flow rate, or a combination thereof) within the membrane isomerization reactor 202 during operation. For the illustrated embodiment, the controller 412 is communicatively connected to conditionally provide control signals to modify the operation of various flow control devices based on the measurements received from the flow analyzers 418, 420 and the sensors 422, 424. For the illustrated embodiment, the flow control devices include: a flow control device 426 that controls the flow of the light naphtha feedstock 204 into the membrane isomerization reactor 202, the flow control device 428 that controls the flow of Fb 218 into the membrane isomerization reactor 202, flow control device 430 that controls the flow of the upgraded light naphtha stream 206 from the membrane isomerization reactor 202, and flow control device 432 that controls the flow of the recycled n-paraffin-containing stream back to the membrane isomerization reactor 202. In some embodiments, the controller 412 provides suitable control signals to modify operation of the flow control devices to ensure that the pressure gradient between the retentate side 406 and the permeate side 408 of the separation membrane 222 is greater than 0 bar gauge (barg) and less than 5 barg (or greater than 10 barg and less than 50 barg) to enable the membrane isomerization reactor 202 to produce the upgraded light naphtha stream 206 at a sufficiently high production rate and that is sufficiently enriched with iso-paraffins to formulate a gasoline product stream having an enhanced RON, as discussed above.

[0057] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0058] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. It should be understood that although the disclosure contains certain aspects, embodiments, and optional features, modification, improvement, or variation of such aspects, embodiments, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.

Claims

CLAIMSWhat is claimed:

1. A method of operating a membrane isomerization reactor, the method comprising: contacting a light naphtha feedstock containing C4-7 iso-paraffins with an isomerization catalyst of the membrane isomerization reactor, the isomerization catalyst disposed on a retentate side of a molecular sieve membrane of the membrane isomerization reactor; isomerizing a least a portion of the C4-7 iso-paraffins of the light naphtha feedstock to produce a reaction mixture having an increased content of C4-7 n-paraffins, a portion of the reaction mixture being recycled to continue contacting the isomerization catalyst disposed on the retentate side of the molecular sieve membrane; separating the C4-7 n-paraffins of the reaction mixture on a permeate side of the molecular sieve membrane, thereby to shift an equilibrium of the isomerization on the retentate side of the molecular sieve membrane towards the production of additional C4-7 n- paraffins; and collecting an upgraded light naphtha stream that is rich in the C4-7 n-paraffins from the permeate side of the molecular sieve membrane.

2. The method of claim 1, wherein the isomerization catalyst contains platinum supported on zeolite.

3. The method of claim 1, wherein the isomerization catalyst contains platinum impregnated on sulfated zirconia.

4. The method of any of claims 1-3, wherein the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof, wherein the molecular sieve membrane has a pore diameter less than 6 Angstrom.

5. The method of any of claims 1-4, wherein the light naphtha feedstock contains at least 50 molar percent (mol. %) iso-paraffins.

6. The method of any of claims 1-5, wherein an n-paraffin content of the upgraded light naphtha stream is at least 5 mol. % greater than an n-paraffin content of the light naphtha feedstock.

7. A system, comprising: a membrane isomerization reactor including: a molecular sieve membrane having a retentate side and a permeate side; an isomerization catalyst disposed on the retentate side of the molecular sieve membrane and configured to receive and isomerize a light naphtha feedstock containing C4-7 iso-paraffins to produce a reaction mixture having an increased content of C4-7 n-paraffins, the molecular sieve membrane being configured to separate the C4-7 n-paraffins of the reaction mixture on the permeate side of the molecular sieve membrane; and a recycle flow path configured to recycle a portion of the reaction mixture back to the isomerization catalyst disposed on the retentate side of the molecular sieve membrane, the membrane isomerization reactor being configured to collect an upgraded light naphtha stream that is rich in the C4-7 n-paraffins from the permeate side of the molecular sieve membrane.

8. The system of claim 7, wherein the isomerization catalyst is a fixed-bed, bifunctional catalyst that is separate and distinct from the molecular sieve membrane.

9. The system of any of claims 7 or 8, wherein the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof, wherein the molecular sieve membrane has a pore dimeter less 6 Angstrom.

10. The system of any of claims 7-9, comprising a steam cracker in fluid communication with the membrane isomerization reactor and configured to receive and steam crack the upgraded light naphtha stream to produce at least an ethene product stream, wherein a yield of the ethene product stream is at least 5 weight percent (wt. %) greater than would be achieved by steam cracking the light naphtha feedstock.

11. A method of operating a membrane isomerization reactor, the method comprising: providing a light naphtha feedstock containing C4-7 n-paraffins to a retentate side of a molecular sieve membrane of the membrane isomerization reactor; separating the C4-7 n-paraffins of the light naphtha feedstock on a permeate side of the molecular sieve membrane to contact an isomerization catalyst of the membrane isomerization reactor, the isomerization catalyst disposed on the permeate side of the molecular sieve membrane; isomerizing a least a portion of the separated C4-7 n-paraffins to produce a reaction mixture having an increased content of C4-7 iso-paraffins, the reaction mixture being recycled to the retentate side of the molecular sieve membrane, wherein the separating of the C4-7 n-paraffins prior to isomerization shifts an equilibrium of the isomerization on the retentate side of the molecular sieve membrane towards the production of additional C4-7 iso-paraffins; and collecting an upgraded light naphtha stream that is rich in the C4-7 iso-paraffins from the retentate side of the molecular sieve membrane.

12. The method of claim 11, wherein the isomerization catalyst contains platinum supported on zeolite.

13. The method of any of claims 11 or 12, wherein the isomerization catalyst contains platinum impregnated on sulfated zirconia.

14. The method of any of claims 11 - 13, wherein the molecular sieve membrane contains zeolite, SAPO-x, or a combination thereof, wherein the molecular sieve membrane has pore dimeter less than 6 Angstrom (A).

15. The method of any of claims 11-14, wherein isomerizing comprises heating the light naphtha feedstock to a temperature from about 200 degrees Celsius (°C) to about 400 °C and pressurizing the light naphtha feedstock to a pressure from about 10 bar gauge (barg) to about 50 barg while contacting the isomerization catalyst.

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