EP4642871A1

EP4642871A1 - Cascaded methods and systems for enriching n-pentane in natural gas liquid feedstock

Info

Publication number: EP4642871A1
Application number: EP23841354.6A
Authority: EP
Inventors: Zeeshan NAWAZ; Abdulaziz Saad AL-ARIFI; Thamire Srinavasa RAO; Pradyut SAMANTA
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2022-12-28
Filing date: 2023-12-28
Publication date: 2025-11-05
Also published as: WO2024141978A1; CN120418391A

Abstract

Systems and methods for concentrating n-pentane from a natural gas liquid (NGL) for a cracking process to enhance ethylene production. Fresh NGL is fed to a first de-iso-pentanizer column, where the NGL is fractionated to a first stream of enriched iso-pentane with light hydrocarbons and a second stream containing n-pentane, residual NGL and heavy hydrocarbons. The second stream can be fed to a cracking unit to produce olefins, including ethylene. The iso- pentane is fed to hydrotreating unit to remove sulphur and impurities to meet the requirements of a reverse isomerization reactor to produce a third stream that containing n-pentane, iso-pentane, and minor hydrocarbons. This third stream is fed to stabilizer and a second iso-pentanizer column to recover an iso-pentane product and recycle it into the reverse isomerization reactor. Streams containing the n-pentane are also supplied to the cracking unit to produce olefins.

Description

CASCADED METHODS AND SYSTEMS FOR ENRICHING N-PENTANE IN NATURAL GAS LIQUID FEEDSTOCK

Inventors: Zeeshan Nawaz

Abdulaziz Saad Al-Arifi Thamire Srinavasa Rao Pradyut Samanta

TECHNICAL FIELD

[0001] The present disclosure generally relates to systems and methods for processing natural gas liquids feedstocks to enrich n-pentane during the production of olefins.

BACKGROUND

[0002] Natural gas liquids (NGL) are components of natural gas that are separated from the gas state in the form of liquids. NGLs is petrochemical feedstock containing ethane, propane, C4 hydrocarbons, and natural gasoline components (mostly pentanes and hexanes), that is turned into. NGL is supplied to the crackers, such as pyrolysis furnaces, to produce a variety of hydrocarbon products. The pentane content in NGL is usually made up of mixed pentanes (n-C5 around 50% and i-C5 around 43%), which may vary with well to well. The pyrolysis furnaces cracks feedstock to high value olefins, such as ethylene, propylene, and butadiene. Lighter olefin products are in increasing demand over the years and improvement of their yield at the outlet of crackers ultimately enhances the overall economics and operational efficiencies of the plant. There is a need for improving the yield of light olefins by upgrading the feedstock before supplying it to the crackers. Furthermore, there is a need for such processes to minimize the carbon loss, while maximizing the productivity in an energy sustainable manner.

SUMMARY

[0003] To address these and other shortcomings in the art, Applicant has developed systems and methods for producing a feed enriched in n-pentane from a NGL feedstock before supplying it for olefin production. Certain embodiments of these methods include the following steps: supplying a natural gas liquid stream containing substantially n-pentane and iso-pentane to a first de-iso-pentanizer to produce a first stream enriched in n-pentane and a second stream enriched in iso-pentane. The methods further include supplying the first stream enriched in n- pentane to a cracking furnace to produce a product stream containing light olefins, passing the second stream enriched in iso-pentane to a hydrotreating unit to remove sulfur and other impurities from the second stream enriched in iso-pentane, supplying the second stream enriched in iso-pentane to a reverse isomerization unit to produce a third stream containing n-pentane, iso-pentane, and minor hydrocarbons, and passing the third stream containing n- pentane, iso-pentane, and minor hydrocarbons through a fractionator to remove the minor hydrocarbons from the third stream and produce an isomerized pentane stream containing n- pentane and iso-pentane. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n-butane, and C6 isomers (C6).

[0004] The fractionator can be a stabilizer. The more volatile C1-C4 hydrocarbons are removed from isomerized pentane stream. The methods further include supplying the isomerized pentane stream containing n-pentane and iso-pentane to a second de-iso-pentanizer to produce a fourth stream enriched in iso-pentane and a fifth stream enriched in n-pentane, and supplying the fifth stream enriched in n-pentane to a cracking unit to produce the product stream containing light olefins, such as ethylene and propylene. The methods may also include the step of passing the fourth stream enriched in iso-pentane to the reverse isomerization unit. The first stream may be enriched in n-pentane. The fifth stream enriched in n-pentane may contain more n- pentane than each of iso-pentane or neo-pentane. The first stream enriched in n-pentane can contain at least 45 mol.% n-pentane and the fifth stream enriched in n-pentane can contain at least 45 mol.% n-pentane. The first stream enriched in n-pentane can contain at least 50 mol.% n- pentane and the fifth stream enriched in n-pentane can contain at least 50 mol.% n-pentane. The natural gas liquid stream can be obtained from a processing of natural gas at a refinery. The natural gas liquid stream can be separated out of a natural gas at the point of production in a field.

[0005] In certain embodiments, the method further includes the step of separating, at a separation unit, the product stream containing light olefins to produce a second product stream containing ethylene and propylene and a recycle stream containing n-pentane and iso-pentane; and supplying the recycle stream to processing in the reverse isomerization unit. In certain embodiments, the recycle stream can be passed through a hydrotreating unit prior to being processed in the reverse isomerization unit.

[0006] Embodiments include systems for production of a feed enriched in n-pentane for olefin production. An example of a system includes the following units: a first de-iso-pentanizer operable to receive a natural gas liquid stream containing substantially n-pentane and isopentane and allow for production of a first stream enriched in n-pentane and a second stream enriched in iso-pentane; a cracking furnace operable to receive the first stream enriched in n- pentane and allow for production of a product stream containing light olefins; a reverse isomerization unit operable to receive the second stream enriched in iso-pentane and allow for production of a third stream containing n-pentane, iso-pentane, and minor hydrocarbons; a fractionator operable to receive the third stream containing n-pentane, iso-pentane, and minor hydrocarbons and allow for production of an isomerized pentane stream containing n- pentane and iso-pentane; a second de-iso-pentanizer operable to receive the isomerized pentane stream containing n-pentane and iso-pentane and allow for production of a fourth stream enriched in iso-pentane and a fifth stream enriched in n-pentane; and a cracking unit operable to receive the fifth stream. The cracking unit can include a catalytic cracking reactor or a thermal cracking reactor. The fractionator can be a stabilizer. The first stream enriched in n- pentane can contain at least 45 mol.% n-pentane and the fifth stream enriched in n-pentane can contain at least 45 mol.% n-pentane. The first stream enriched in n-pentane can contain at least 50 mol.% n-pentane and the fifth stream enriched in n-pentane can contain at least 50 mol.% n- pentane. In certain embodiments, the system can include a hydrotreater unit operable to receive the second stream enriched in iso-pentane and allow for removal of sulfur impurities from the second stream enriched in iso-pentane prior to the second stream being supplied to the reverse isomerization unit.

[0007] 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

[0008] 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. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate embodiments of the disclosure.

[0009] FIG. 1 is a diagrammatic representation of a system for production of a n-pentane rich feed from a natural gas liquid feedstock, according to an embodiment of the present disclosure.

[0010] FIG. 2 is a diagrammatic representation of another embodiment of a system for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure.

[0011] FIG. 3 is a diagrammatic representation of another embodiment of a system for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure.

[0012] FIG. 4 is a diagrammatic representation of another embodiment of a system for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure.

[0013] FIG. 5 is a block diagram of a method for production of a n-pentane rich feed from a natural gas liquid feedstock, according to an embodiment of the present disclosure.

[0014] FIG. 6 is a graphical representation of the effect of change in the n-C5 concentration in NGL on ethylene productivity.

DETAILED DESCRIPTION

[0015] The present disclosure describes various embodiments related to processes, methods, and systems for production of a feed enriched in n-pentane from a natural gas liquid feedstock. Further embodiments may be described and disclosed. The natural gas liquid feedstock can be obtained from a processing of natural gas at a refinery. The natural gas liquid feedstock can be separated out of a natural gas at the point of production in a field.

[0016] 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.

[0017] 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.

[0018] 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. [0019] 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. [0020] 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.” 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. The term “enrich” or “rich” or their variations mean an amount of at least generally about 20 wt.%, or about 25 wt.%, or about 25 wt.%, of a compound or class of compounds in a stream. The term “substantially” mean an amount of at least generally about 50 wt.%, or at least about 60 wt.%, or at least about 70 wt.%, or at least about 80 wt.%, or at least about 90 wt.%, at least about 95 wt.%, at least about 97 wt.%, or at least about 99 wt.%, or more, or any integer between 50% and 100% of a compound or class of compounds in a stream.

[0021] Disclosed here are systems and methods for fractionating iso-pentane from a natural gas liquid (NGL) and converting it into n-pentane for a cracking process configured to enhance ethylene production. In certain embodiments, fresh NGL is supplied to a first de-iso-pentanizer column where NGL is fractionated to main streams — a first stream containing iso-pentane with light hydrocarbons and a second stream containing the residue of the NGL feed, such as n-pentane, NGL, and heavy hydrocarbons. The deisopentanizer can be operated at a temperature ranging from about 80 °C to about 100 °C, or ranging from about 85 °C to about 95 °C. The residue of the NGL feed is fed to a steam cracker directly without any further process or treatment. The first stream containing iso-pentane with light hydrocarbons is supplied to a hydrotreating unit to remove sulphur and impurities to meet the requirements of a reverse isomerization reactor.

[0022] Reverse isomerization of the isopentane-containing stream is process that employs an isopentane reverse isomerization catalyst and isomerization conditions that result in conversion of at least some isopentane in the isopentane-containing stream to normal paraffins. Isopentane reverse isomerization units, as well as isopentane reverse isomerization catalysts and conditions for reverse isomerization of isopentane, are known to those of skill in the art. Examples of suitable reverse isomerization catalysts can include, but are not limited to, zeolitic catalysts and sulfated zirconia catalysts. Exemplary conditions for reverse isomerization of isopentane include a temperature ranging from about 135 °C to about 700 °C, and a pressure ranging from about 1378 kiloPascals (kPa) to about 3103 kPa. Depending on the reaction conditions and the type of reverse isomerization catalyst that is used, different hydrocarbons are produced in addition to n-pentane. Treatment of the first stream containing iso-pentane here with light hydrocarbons in the reverse isomerization reactor produces a third stream containing n-pentane, iso-pentane, olefins, and methane. This third stream is fed to a stabilizer and a second de-iso-pentanizer column to separate/recover an iso-pentane product out of the n-pentane, olefin, and methane stream. The more volatile C1-C4 hydrocarbons are removed from the third stream. The stream containing n- pentane, olefin, and methane is supplied to the reverse isomerization reactor. In certain embodiments, hydrogen is supplied to the reverse isomerization reactor, which is also recovered after the reactor. In certain embodiments, the second stream and the remaining third stream contain substantially low amounts of isopentane and are fed to a steam cracker to enhance ethylene yield and production.

[0023] Disclosed embodiments include systems for production of a feed enriched in n-pentane from a natural gas liquid feedstock for olefin production. FIG. 1 is a diagrammatic representation of a system 100 for production of a n-pentane rich feed from a natural gas liquid feedstock, according to an embodiment of the present disclosure. The natural gas liquid stream 102 can be obtained from a processing of natural gas at a refinery or can be separated out of a natural gas at the point of production in a field. This system 100 includes a first de-iso-pentanizer 104 operable to receive a natural gas liquid stream 102 containing n-pentane and iso-pentane and allow for production of a first stream 106 enriched in n-pentane and a second stream enriched in isopentane 110. This system 100 includes a cracking unit 108 operable to receive the first stream enriched in n-pentane 106 and allow for production of a product stream containing light olefins 109. The cracking unit may be a cracking furnace, a catalytic cracking reactor, or a thermal cracking reactor. The first stream may be enriched in n-pentane and may contain more n-pentane than each of iso-pentane or neo-pentane. The first stream enriched in n-pentane can contain at least 45 mol.% n-pentane. The first stream enriched in n-pentane can contain at least 50 mol.% n- pentane. This system 100 includes a hydrotreater unit 112 operable to receive the second stream enriched in iso-pentane 110 and allow for removal of sulfur impurities from the second stream enriched in iso-pentane. This second stream with reduced sulfur content 114 is supplied to the reverse isomerization unit 116. This reverse isomerization unit 116 is operable to receive the second stream with reduced sulfur content 114 and allow for production of a third stream 118 containing n-pentane, iso-pentane, and minor hydrocarbons, and a stabilizer 120 operable to receive the third stream 118 and allow for production of an isomerized pentane stream 122 containing n-pentane and iso-pentane. The size and operation of the reverse isomerization unit 116 depend upon the iso-pentane concentration in the NGL feed and recycle rate. This reverse isomerization unit 116 can operate at equilibrium using platinum- based catalysts. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n-butane, and C6 isomers (C6). The fractionator can be a stabilizer. The C1-C4 hydrocarbons are removed from isomerized pentane stream.

[0024] This system 100 also includes a second de-iso-pentanizer 124 operable to receive the isomerized pentane stream 122 and allow for production of a fourth stream 128 enriched in iso-pentane and a fifth stream 126 enriched in n-pentane. The fourth stream 128 enriched in iso-pentane is recycled to the first de-iso-pentanizer 104. The fifth stream 126 enriched in n- pentane may contain more n-pentane than each of iso-pentane or neo-pentane. The fifth stream 126 enriched in n-pentane can contain at least 45 mol.% n-pentane. The fifth stream 126 enriched in n-pentane can contain at least 50 mol.% n-pentane. The fifth stream 126 is supplied to the cracking unit 108 that allows for production of the product stream containing light olefins 109, such as ethylene and propylene. The cracking unit may be a cracking furnace, a catalytic cracking reactor, or a thermal cracking reactor.

[0025] FIG. 2 is a diagrammatic representation of a system 200 for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure. This system 200 includes a first de-iso-pentanizer 204 operable to receive a natural gas liquid stream 202 containing n-pentane and iso-pentane and allow for production of a first stream 206 enriched in n-pentane and a second stream enriched in iso-pentane 210. This system 200 includes a cracking unit 208 operable to receive the first stream enriched in n- pentane 206 and allow for production of a product stream containing light olefins 209, such as ethylene and propylene. The cracking unit may be a cracking furnace, a catalytic cracking reactor, or a thermal cracking reactor. The first stream 206 may be enriched in n-pentane and may contain more n-pentane than each of iso-pentane or neo-pentane. The first stream 206 can contain at least 45 mol.% n-pentane. The first stream 206 can contain at least 50 mol.% n-pentane. This system 200 includes a hydrotreater unit 212 operable to receive the second stream 210 and allow for removal of sulfur impurities from the second stream. This second stream with reduced sulfur content 214 is supplied to the reverse isomerization unit 216.

[0026] In certain embodiments, hydrogen is supplied along with the second stream 214 to the reverse isomerization unit 216 to facilitate the desired reactions and to help minimize coke formation on the catalyst. This reverse isomerization unit 216 is operable to receive the second stream with reduced sulfur content 214 and allow for production of a third stream 218 containing n-pentane, iso-pentane, and minor hydrocarbons, and a stabilizer 220 operable to receive the third stream 218 and allow for production of an isomerized pentane stream 222 containing n-pentane and iso-pentane. The size and operation of the reverse isomerization unit 216 depend upon the iso-pentane concentration in the NGL feed and recycle rate. This reverse isomerization unit 216 can operate at equilibrium using platinum-based catalysts. The fractionator can be a stabilizer. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n-butane, and C6 isomers (C6). The volatile Cl -C4 hydrocarbons are removed from isomerized pentane stream. The third stream 218 can be supplied to a H2 separation unit before being supplied to the stabilizer 220. This H2 separation unit removes and recycles the H2 back to the feed of the reverse isomerization unit 216. [0027] This system 200 also includes a second de-iso-pentanizer 224 operable to receive the isomerized pentane stream 222 and allow for production of a fourth stream 228 enriched in iso-pentane and a fifth stream 226 enriched in n-pentane. The fourth stream 228 enriched in iso-pentane is recycled to the hydrotreater unit 212 or to the reverse isomerization unit 216. The fifth stream 226 enriched in n-pentane may contain more n-pentane than each of iso-pentane or neo-pentane. The fifth stream 226 enriched in n-pentane can contain at least 45 mol.% n- pentane. The fifth stream 226 enriched in n-pentane can contain at least 50 mol.% n-pentane. The fifth stream 226 is supplied to the cracking unit 208 that allows for production of the product stream containing light olefins 209, such as ethylene and propylene.

[0028] FIG. 3 is a diagrammatic representation of a system 300 for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure. This system 300 includes a first de-iso-pentanizer 304 operable to receive a natural gas liquid stream 302 containing n-pentane and iso-pentane and allow for production of a first stream 306 enriched in n-pentane and a second stream enriched in iso-pentane 312. This system 300 includes a cracking unit 308 operable to receive the first stream enriched in n- pentane 306 and allow for production of a product stream containing light olefins 309, such as ethylene and propylene. The cracking unit may be a cracking furnace, a catalytic cracking reactor, or a thermal cracking reactor. The first stream 306 may be enriched in n-pentane and may contain more n-pentane than each of iso-pentane or neo-pentane. The first stream 306 can contain at least 45 mol.% n-pentane. The first stream 306 can contain at least 50 mol.% n-pentane. This system 300 includes a hydrotreater unit 314 operable to receive the second stream 312 and a hydrogen stream 316 and allow for removal of sulfur impurities from the second stream 312. This second stream with reduced sulfur content 318 along with a stream 322 of one or more additives is supplied to an additives mixer 320. The stream enriched in iso-pentane along with the additives 324 is supplied to a dryer 326 to reduce the moisture content and produce an iso-pentane-enriched and dry stream 330.

[0029] This system 300 includes a reverse isomerization unit 332 is operable to receive the iso- pentane-enriched and dry stream 330 and allow for production of a third stream 334 containing n-pentane, iso-pentane, and minor hydrocarbons, and a stabilizer 336 operable to receive the third stream 334 and allow for production of an isomerized pentane stream 340 containing n-pentane and iso-pentane. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n- butane, and C6 isomers (C6). The size and operation of the reverse isomerization unit 332 depend upon the iso-pentane concentration in the NGL feed and recycle rate. This reverse isomerization unit 332 can operate at equilibrium using platinum-based catalysts. The fractionator can be a stabilizer. The stabilizer 336 is operable to remove any light hydrocarbons made during the reactions from the third stream 334. The light hydrocarbons containing stream 338 exits the stabilizer 336 and may be supplied for further processing, including blending into the refinery fuel gas system.

[0030] This system 300 also includes a second de-iso-pentanizer 342 operable to receive the isomerized pentane stream 340 and allow for production of a fourth stream 346 enriched in iso-pentane and a fifth stream 344 enriched in n-pentane. The fourth stream 346 enriched in iso-pentane is recycled to the hydrotreater unit 314 or to the reverse isomerization unit 332. The fifth stream 344 enriched in n-pentane may contain more n-pentane than each of iso-pentane or neo-pentane. The fifth stream 344 enriched in n-pentane can contain at least 45 mol.% n- pentane. The fifth stream 344 enriched in n-pentane can contain at least 50 mol.% n-pentane. The fifth stream 344 is supplied to the cracking unit 308 that allows for production of the product stream containing light olefins 310.

[0031] FIG. 4 is a diagrammatic representation of a system 400 for production of a n-pentane rich feed from a natural gas liquid feedstock, according to another embodiment of the present disclosure. This system 400 includes a first de-iso-pentanizer 404 operable to receive a natural gas liquid stream 402 containing n-pentane and iso-pentane and allow for production of a first stream 406 enriched in n-pentane and a second stream enriched in iso-pentane 412. This system 400 includes a cracking unit 408 operable to receive the first stream enriched in n- pentane 406 and allow for production of a product stream containing light olefins 410, such as ethylene and propylene. The cracking unit may be a cracking furnace, a catalytic cracking reactor, or a thermal cracking reactor. The first stream 406 may be enriched in n-pentane and may contain more n-pentane than each of iso-pentane or neo-pentane. The first stream 406 can contain at least 45 mol.% n-pentane. The first stream 406 can contain at least 50 mol.% n-pentane. This system 400 includes a hydrotreater unit 414 operable to receive the second stream 412 and allow for removal of sulfur impurities from the second stream 412. This second stream with reduced sulfur content 416 is supplied to a first fractionator 418. [0032] The fractionator 418 is operable to remove a non-condensable components from the feed stream as an off-gas stream 420 and a first light hydrocarbons containing stream 422. These streams 420 and 422 exits the fractionator 436 and may be supplied for further processing in the refinery. The stream enriched in iso-pentane 424 is supplied from the fractionator 418 to a reverse isomerization unit 426. This unit 426 receives the stream enriched in iso-pentane 424 and is operated to allow for production of a third stream 428 containing n-pentane, isopentane, and minor hydrocarbons, and a second fractionator 430 operable to receive the third stream 428 and allow for production of an isomerized pentane stream 434 containing n- pentane and iso-pentane. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n-butane, and C6 isomers (C6). The size and operation of the reverse isomerization unit 426 depend upon the isopentane concentration in the NGL feed and recycle rate. This reverse isomerization unit 426 can operate at equilibrium using platinum-based catalysts. The second fractionator can be a stabilizer. The second fractionator 430 is operable to remove any light hydrocarbons made during the isomerization reactions from the third stream 428. The second light hydrocarbons containing stream 432 exits the second fractionator 430 and may be supplied for further processing, including blending into the refinery fuel gas system.

[0033] This system 400 also includes a second de-iso-pentanizer 436 operable to receive the isomerized pentane stream 434 and allow for production of a fourth stream 440 enriched in iso-pentane and a fifth stream 438 enriched in n-pentane. The fourth stream 440 enriched in iso-pentane is recycled to the hydrotreater unit 414 or to the reverse isomerization unit 426. The fifth stream 438 enriched in n-pentane may contain more n-pentane than each of iso-pentane or neo-pentane. The fifth stream 438 enriched in n-pentane can contain at least 45 mol.% n- pentane. The fifth stream 438 enriched in n-pentane can contain at least 50 mol.% n-pentane. The fifth stream 438 is supplied to the cracking unit 408 that allows for production of the product stream containing light olefins 410, such as ethylene and propylene.

[0034] Disclosed embodiments include methods for production of a feed enriched in n-pentane from a natural gas liquid feedstock for olefin production. In certain embodiments, the natural gas liquid can be obtained from a processing of natural gas at a refinery or can be separated out of a natural gas at the point of production in a field. FIG. 5 is a block diagram of an embodiment of a method 500 for production of a n-pentane rich feed from a natural gas liquid feedstock. This method 500 includes the step 502 of supplying a natural gas liquid stream containing n-pentane and iso-pentane to a first de-iso-pentanizer to produce a first stream enriched in n-pentane and a second stream enriched in iso-pentane. In certain embodiments, the first stream enriched in n-pentane contains more n-pentane than each of iso-pentane or neo-pentane. This first stream can contain at least 40 mol.% of n-pentane. This first stream can contain at least 45 mol.% of n- pentane. This first stream can contain at least 50 mol.% of n-pentane. The method 500 further includes the step 504 of supplying the first stream enriched in n-pentane to a cracking unit to produce a product stream containing light olefins. The method 500 further includes the step 506 of passing the second stream enriched in iso-pentane to a hydrotreating unit to remove sulfur and other impurities from the second stream enriched in iso-pentane, and step 508 of supplying the second stream enriched in iso-pentane to a reverse isomerization unit to produce a third stream containing n-pentane, iso-pentane, and minor hydrocarbons. The method 500 further includes the step 510 of passing the third stream containing n-pentane, iso-pentane, and light olefins through a fractionator to remove the light olefins from the third stream and produce an isomerized pentane stream containing n-pentane and iso-pentane. The minor hydrocarbons in the isomerization reaction products can include one or more of small amounts of methane, ethane, propane, isobutane, n-butane, and C6 isomers (C6). The C1-C4 hydrocarbons are removed from isomerized pentane stream. The fractionator can be a stabilizer. The more volatile C1-C4 hydrocarbons are removed from isomerized pentane stream. The third stream is either stabilized to remove C1-C4 hydrocarbons in a single column, or is fractionated in stages sequentially removing the C1-C4 hydrocarbons in multiple columns.

[0035] The method 500 further includes the step 512 of supplying the isomerized pentane stream containing n-pentane and iso-pentane to a second de-iso-pentanizer to produce a fourth stream enriched in iso-pentane and a fifth stream enriched in n-pentane, and the step 514 of supplying the fifth stream enriched in n-pentane to the cracking unit to produce the product stream containing light olefins. In certain embodiments, the fifth stream enriched in n-pentane contains more n-pentane than each of iso-pentane or neo-pentane. This fifth stream can contain at least 40 mol.% of n-pentane. This fifth stream can contain at least 45 mol.% of n-pentane. This fifth stream can contain at least 50 mol.% of n-pentane. In certain embodiments, the method 500 includes a step of passing the fourth stream enriched in iso-pentane to the reverse isomerization unit. [0036] The method 500 can further include the step of separating, at a separation unit, the product stream containing light olefins to produce a second product stream containing ethylene and propylene and a recycle stream containing n-pentane and iso-pentane, and supplying the recycle stream to processing in the reverse isomerization unit. In certain embodiments, the recycle stream is passed through a hydrotreating unit prior to being processed in the reverse isomerization unit.

EXAMPLES

[0037] The example provided below illustrates selected aspects of the various methods and systems of integrating petrochemical plant and refinery operations.

Example 1

[0038] Simulation based estimations were conducted using a software for simulation of steam cracking furnaces. The case studies were used the normal operational conditions of liquid furnaces for ethylene maximization, such as high severity coils. High severity (characterized by residence time of less than 0.5 second and temperature up to 900-1100 °C) conditions increase ethylene yield and lowers propylene yield. The degree of severity is described by the propylene/ethylene ratio (P/E). The P/E ratio for the simulations was set at 0.4. Results shown in FIG. 6 demonstrate the effect of n-C5 concentration change in NGL on ethylene productivity. Increase in the amount of n-pentane in the NGL feed led to consistent increase in the amount of ethylene in the product stream from the steam cracking furnace.

[0039] 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.

[0040] 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

CLAIMS What is claimed:

1. A method for production of a feed enriched in n-pentane for olefin production, the method comprising: supplying a natural gas liquid stream containing substantially n-pentane and isopentane to a first de-iso-pentanizer to produce a first stream enriched in the n- pentane and a second stream enriched in the iso-pentane; supplying the first stream enriched in the n-pentane to a cracking furnace to produce a product stream containing light olefins; passing the second stream enriched in the iso-pentane to a hydrotreating unit to remove sulfur and other impurities from the second stream enriched in the isopentane; supplying the second stream enriched in the iso-pentane to a reverse isomerization unit to produce a third stream containing the n-pentane, the iso-pentane, and minor hydrocarbons; passing the third stream through a fractionator to remove the minor hydrocarbons from the third stream and produce an isomerized pentane stream containing the n-pentane and the iso-pentane; supplying the isomerized pentane stream containing the n-pentane and the isopentane to a second de-iso-pentanizer to produce a fourth stream enriched in the iso-pentane and a fifth stream enriched in the n-pentane; and supplying the fifth stream enriched in the n-pentane to the cracking furnace to produce the product stream containing the light olefins.

2. The method according to claim 1, further comprising the step of: passing the fourth stream enriched in the iso-pentane to the reverse isomerization unit.

3. The method according to claims 1 or 2, wherein the first stream enriched in the n- pentane and the fifth stream enriched in the n-pentane contain more n-pentane than each of iso-pentane or neo-pentane.

4. The method according to according to claims 1 or 2, wherein the first stream enriched in the n-pentane and the fifth stream enriched in the n-pentane contain at least 45 mol.% n- pentane.

5. The method according to according to claims 1 or 2, wherein the first stream enriched in the n-pentane and the fifth stream enriched in the n-pentane contain at least 50 mol.% n- pentane.

6. The method according to any one of claims 1 to 5, wherein the natural gas liquid stream is obtained from a processing of natural gas at a refinery.

7. The method according to any one of claims 1 to 5, wherein the natural gas liquid stream is separated out of a natural gas at a point of production in a field.

8. The method according to any one of claims 1 to 7, the method further comprising: separating, at a separation unit, the product stream containing the light olefins to produce a second product stream containing ethylene and propylene and a recycle stream containing the n-pentane and the iso-pentane; and supplying the recycle stream to processing in the reverse isomerization unit.

9. The method according to claim 8, wherein the recycle stream is passed through the hydrotreating unit prior to being processed in the reverse isomerization unit.

10. The method according to any one of claims 1 to 9, wherein the fractionator is a stabilizer.

11. A system for production of a feed enriched in n-pentane for olefin production, the system comprising: a first de-iso-pentanizer operable to receive a natural gas liquid stream containing n-pentane and iso-pentane and allow for production of a first stream enriched in the n-pentane and a second stream enriched in the iso-pentane; a cracking unit operable to receive the first stream enriched in the n-pentane and allow for production of a product stream containing light olefins; a reverse isomerization unit operable to receive the second stream enriched in the iso-pentane and allow for production of a third stream containing the n-pentane, the iso-pentane, and minor hydrocarbons; a fractionator operable to receive the third stream containing the n-pentane, the iso-pentane, and the minor hydrocarbons and allow for production of an isomerized pentane stream containing the n-pentane and the iso-pentane; and a second de-iso-pentanizer operable to receive the isomerized pentane stream containing the n-pentane and the iso-pentane and allow for production of a fourth stream enriched in the iso-pentane and a fifth stream enriched in the n- pentane, the cracking unit being further operable to receive the fifth stream.

12. The system according to claim 11, wherein the cracking unit contains a catalytic cracking reactor or a thermal cracking reactor.

13. The system according to claim 11 or 12, wherein the fractionator is a stabilizer.

14. The system according to any one of claims 11 to 13, wherein the fifth stream enriched in the n-pentane contains at least 45 mol.% n-pentane.

15. The system according to any one of claims 11 to 14, further comprising: a hydrotreater unit operable to receive the second stream enriched in the isopentane and allow for removal of sulfur impurities from the second stream enriched in the iso-pentane prior to the second stream being supplied to the reverse isomerization unit.