Methods and systems for selective c5 valorization

Abstract

Systems and methods for fractionating a mixed C5 stream from a cracker to produce a light fraction containing C1-C4 hydrocarbons, isopentane, and isopentene, and desulfurizing the light fraction to produce a substantially sulfur-free C5-rich product for a gasoline pool. A heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclo-C5 compounds from fractionating the mixed C5 stream is recycled to the cracker.

Description

METHODS AND SYSTEMS FOR SELECTIVE C5 VALORIZATIONInventors: Prasanna Pathath and Sankaran NedumbamanaCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to European Application No. EP23193589.1, filed on August 25, 2023, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure generally relates to systems and methods for processing mixed C5 streams from a cracker by separation and enrichment before supplying it to a gasoline pool.BACKGROUND

[0003] As part of an olefins production process, C2-C5 alkanes are cracked to produce corresponding olefins and several high molecular weight components are produced. These high molecular weight components are separated by downstream operations. One of these fractions, the mixed C5 fraction, is recycled to the cracker to generate more olefins. However, the cracker efficiency as well as the yield of olefins produced by cracking of the mixed C5 fraction dominated by isopentane / isopentene is less than the yield of olefins produced from fresh feed.SUMMARY

[0004] To address these and other shortcomings in the art, Applicant has developed systems and methods for processing mixed C5 streams and valorization of selective C5 streams. In certain examples, the selective C5 streams are recycled to a cracker with fresh feed to increase olefin production. In certain examples, the mixed C5 recycle stream is processed further before being supplied as cracker feed. The C5 compounds are separated from the cracker product stream, further enriched for the C5 content and provided for blending in gasoline pool.

[0005] Embodiments include a method for production of a substantially sulfur-free C5-rich product. The method includes the steps of fractionating a mixed C5 stream from a cracker to produce (a) a light fraction containing C1-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, cyclopentane, and, cyclopentene. The method further includes recycling the heavy fraction to the cracker and desulfurizing the light fraction to produce a substantially sulfur-free C5-rich product containing pentenes and isopentane. In certain embodiments, the substantially sulfur-free C5-rich product is supplied to a gasoline pool to increase octane number. In certain embodiments, the light fraction contains greater than about 50 wt.% of pentenes and isopentane. In certain embodiments, the heavy fraction contains about greater than about 50 wt.% of n-pentane and cyclopentane. The light fraction may contain isopentane / isopentene and other pentenes ranging from about 70 wt.% to about 85 wt.%. In certain embodiments, The heavy fraction may contain n-pentane and cyclopentane / cyclopentene ranging from about 75 wt.% to about 95 wt.%. The method specifically involves the separation of isopentane / isopentene from n-pentane / pentenes and cyclo-C5 compounds. Increasing the concentration of the n-pentanes and cyclo-C5 compounds in the cracker feed increase the yield of the olefins, whereas presence of isopentane / isopentene decrease the olefin yield. Moreover, the isopentane / isopentane-rich stream is advantageous for gasoline blending as it can increase the octane number of the gasoline product.

[0006] Another method for production of a substantially sulfur-free C5-rich product includes the step of processing a mixed C5 stream from a cracker through a hydrogenator to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) and produce a treated mixed C5 stream containing paraffins, olefins, and saturated aromatics, and fractionating the treated mixed C5 stream to produce (a) a light fraction containing C1-C4 hydrocarbons and isopentane, and (b) aheavy fraction containing C5+ hydrocarbons, n-pentane, and cyclopentane. The method further includes recycling the heavy fraction to the cracker and desulfurizing the light fraction to produce a substantially sulfur-free C5-rich product containing isopentane. In certain embodiments, the substantially sulfur-free C5-rich product is supplied to a gasoline pool. In certain embodiments, the light fraction contains greater than about 70 wt.% of n-pentane and isopentane. In certain embodiments, the heavy fraction contains greater than about 35 wt.% of cyclopentane.

[0007] Embodiments include systems for production of a substantially sulfur-free C5-rich product. One such system includes a cracker to process a C5+ hydrocarbon stream to produce a mixed C5 stream and a fractionating column in fluid communication with the cracker and configured to receive the mixed C5 stream and to produce (a) a light fraction containing C1-C4 hydrocarbons, pentenes, and isopentane and (b) a heavy fraction containing C5+ hydrocarbons, n- pentane, and cyclo-C5 compounds that is recycled to the cracker. The system further includes a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction to produce substantially sulfur-free C5-rich product. In certain examples, the desulfurization unit is a mercaptan oxidation unit configured to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction and produce the substantially sulfur-free C5-rich product to be blended into a gasoline pool. The gasoline pool contains a mixture of blend stocks with specifications that varies by seasons and regions.

[0008] Another embodiment of a system for production of a substantially sulfur-free C5-rich product includes a cracker to process C5+ hydrocarbon stream to produce a mixed C5 stream and a hydrogenator in fluid communication with the cracker and configured to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) and to produce a treated mixed C5 streamcontaining paraffins, olefins, and saturated aromatics. The system further includes a fractionating column in fluid communication with the hydrogenator and configured to receive the treated mixed C5 stream and to produce (a) a light fraction containing C1-C4 hydrocarbons and isopentane and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclopentane that is recycled to the cracker. The system also includes a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction to produce a substantially sulfur-free C5-rich product. In certain examples, the desulfurization unit is a mercaptan oxidation unit configured to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction and produce the substantially sulfur-free C5-rich product to be blended into a gasoline pool.

[0009] 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

[0010] 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 madeto 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.

[0011] FIG. l is a diagrammatic representation of a system for production of a substantially sulfur- free C5-rich product, according to an embodiment of the present disclosure.

[0012] FIG. 2 is a diagrammatic representation of a system for production of a substantially sulfur-free C5-rich product, according to another embodiment of the present disclosure.DETAILED DESCRIPTION

[0013] The present disclosure describes various embodiments related to processes, methods, and systems for production of a substantially sulfur-free C5-rich product from a mixed C5 stream exiting a cracker. Further embodiments may be described and disclosed.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.%, and preferably about 25 wt.%, of a compound or class of compounds in a stream.

[0019] Certain embodiments include methods for selective valorization of a mixed C5 stream. These methods include processing a mixed C5 stream from a cracker through a fractionating column. In some examples, the C2-C5 feed is supplied to the cracker operated at a temperature ranging from 800 °C to 900 °C and a pressure of about 1 atm or less. In certain examples, the mixed C5 stream contains about forty weight percent (40 wt.%) of C5 components that may include linearpentenes, isopentene, n-pentanes, isopentanes, as well as cyclopentene, cyclopentadiene, linear and branched C5 dienes, and acetylenes. The mixed C5 stream is separated by the fractionating column into (a) a light fraction containing C1-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclo-C5 compounds. In certain examples, the light fraction contains about 70 wt.% to about 85 wt.% of pentenes and isopentane / isopentene, and the heavy fraction contains about 75 wt.% to about 95 wt.% of n- pentane and cyclopentane / cyclopentene. In certain examples, the light fraction from the fractionating column contains at least 70 wt.% of C5 components rich with pentanes and isopentane. The heavy fraction from the fractionating column may contain less than 35 wt.% of C5 components rich with n-pentane and cyclopentane. The separation ratio is decided and controlled by the process parameters depending upon composition of mixed C5 stream. The olefins yield in the cracker is affected due to the presence of isopentane / isopentene in the C5 recycle stream to the cracker. The cracker efficiency decreases and leads to fouling and eventually have an effect on cracker run length. Therefore, processing the mixed C5 stream to result in a recycle stream that is substantially depleted in isopentane / isopentane increases cracker efficiency. In some examples, this processing leads to enhanced olefin yields.

[0020] In certain examples, the fractionating column is a deisopentanizer that separates a light fraction containing about 5 to 20 wt.% of isopentanes, about 5 to 35 wt.% of pentenes, and C1-C4 hydrocarbons and a heavy fraction containing about 5 to 35 wt.% of n-pentanes, about 9 to 45 wt.% of cyclopentanes and C5+ hydrocarbons. In certain examples, the light fraction from the deisopentanizer contains at least 70 wt.% of C5 components rich with pentenes and isopentane. The heavy fraction from the deisopentanizer may contain less than 35 wt.% of C5 components rich with n-pentane and cyclopentane. These methods further include desulfurization of the lightfraction to remove substantially all mercaptans and other sulfur- containing compounds and blending the resulting sulfur-free C5- fraction into a gasoline pool. In certain examples, the desulfurization is a mercaptan oxidation process to remove mercaptans from a light fraction to produce a fuel stream with reduced sulfur levels. The sulfur content of the light fraction is about 300 ppm and the fuel stream has reduced sulfur levels of about 1 ppm or less. In certain examples, the fuel stream with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in gasoline pool.

[0021] Certain embodiments of the methods include processing a mixed C5 stream from a cracker through a hydrogenator to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) and to produce a treated mixed C5 stream containing paraffins, olefins, and saturated aromatics. This treated mixed C5 stream is supplied to a fractionating column to produce (a) a light fraction containing C1-C4 hydrocarbons and isopentane and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclopentane. In certain examples, the light fraction contains about 35 wt.% to about 50 wt.% of isopentane, and the heavy fraction contains about 75 wt.% to about 95 wt.% of n-pentane and cyclopentane. The separation ratio is decided and controlled by the process parameters.

[0022] In certain examples, the fractionating column is a deisopentanizer that separates a light fraction containing about 1 to 20 wt.% of isopentanes and C1-C4 hydrocarbons and a heavy fraction containing about 9 to 40 wt.% of n-pentanes, about 15 to 45 wt.% of cyclopentanes and C5+ hydrocarbons. These methods further include desulfurization of the light fraction to remove substantially all mercaptans and other sulfur-containing compounds and blending the resulting sulfur-free C5- fraction into a gasoline pool. In certain examples, the desulfurization is a mercaptan oxidation process to remove mercaptans from a light fraction to produce a fuel stream with reducedsulfur levels. The sulfur content of the light fraction is about 300 ppm and the fuel stream has reduced sulfur levels of about 1 ppm or less. This fuel stream may be blended to produce an aviation fuel. In certain examples, the fuel stream with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in gasoline pool.

[0023] Certain embodiments of the systems include (i) a cracker to process C5+ hydrocarbon stream to produce a mixed C5 stream, (ii) a fractionating column in fluid communication with the cracker and configured to receive the mixed C5 stream and to produce (a) a light fraction containing C1-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclo-C5 compounds that is recycled to the cracker, and (iii) a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction. In some embodiments, the fractionating column can be a tray fractionator. In certain examples, the mixed C5 stream contains about 40 wt.% of mixed C5 components. In certain examples, the light fraction contains about 15 wt.% to about 45 wt.% of pentanes and isopentane, and the heavy fraction contains about 45 wt.% to about 85 wt.% of n- pentane and cyclopentane. In certain examples, the light fraction from the fractionating column contains at least 70 wt.% of C5 components rich with pentenes and isopentane. The heavy fraction from the fractionating column may contain less than 35 wt.% of C5 components rich with n- pentane and cyclopentane. In certain examples, the fractionating column is a deisopentanizer that separates a light fraction containing about 35 to 50 wt.% of isopentanes, about 0 to 15 wt.% of pentenes, and C1-C4 hydrocarbons and a heavy fraction containing about 9 to 40 wt.% of n- pentanes, about 15 to 45 wt.% of cyclopentanes and C5+ hydrocarbons.

[0024] In certain examples, the desulfurization unit is a mercaptan oxidation unit configured to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction and produce a C5-rich product with reduced sulfur levels to be blended into a gasoline pool. The sulfur content of the light fraction is about 300 ppm and the C5-rich product has reduced sulfur levels of about 1 ppm or less. In certain examples, the system configurations include a postseparation desulfurization unit, as the hydrogenator cannot decrease sulfur content to recommended levels. In certain examples, the fuel stream with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in gasoline pool.

[0025] Certain embodiments of the systems include (i) a cracker to process C5+ hydrocarbon stream to produce a mixed C5 stream, (ii) a hydrogenator in fluid communication with the cracker and configured to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) in the mixed C5 stream to produce a treated mixed C5 stream containing paraffins, olefins, and saturated aromatics; (iii) a fractionating column in fluid communication with the hydrogenator and configured to receive the treated mixed C5 stream and to produce (a) a light fraction containing C1-C4 hydrocarbons and isopentane and (b) a heavy fraction containing C5+ hydrocarbons, n- pentane, and cyclopentane that is recycled to the cracker, (iv) a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction. In certain examples, the mixed C5 stream contains about 40 wt.% of mixed C5 components. In certain examples, the fractionating column is a deisopentanizer that separates a light fraction containing C1-C4 hydrocarbons and about 15 to 45 wt.% of isopentanes, and a heavy fraction containing and C5+ hydrocarbons about 9 to 40 wt.% of n-pentanes, and about 15 to 45 wt.% of cyclopentanes. In certain examples, the desulfurization unit is a mercaptan oxidation unitconfigured to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction and produce a C5-rich product with reduced sulfur levels to be blended into a gasoline pool. In certain examples, the fuel stream with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in a gasoline pool.

[0026] FIG. 1 is a diagrammatic representation of a system 100 for production of a substantially sulfur-free C5-rich product, according to an embodiment of the present disclosure. This system 100 includes a cracker 102 to process C5+ hydrocarbon stream and to produce a mixed C5 stream 104. The system 100 includes a fractionating column 106 configured to receive the mixed C5 stream 104 and in fluid communication with the cracker 102. In certain examples, the mixed C5 stream contains about 40 wt.% of mixed C5 components. This mixed C5 stream 104 is separated to produce (a) a light fraction 108 containing C1-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction 110 containing C5+ hydrocarbons, n-pentane, and cyclo-C5 compounds that is recycled to the cracker 102. The system 100 includes a desulfurization unit 112 in fluid communication with the fractionating column 106 and configured to receive the light fraction 108 and to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction 108. In certain examples, the light fraction 108 from the fractionating column 106 contains at least 70 wt.% of C5 components rich with pentenes and isopentane. The heavy fraction 110 from the fractionating column 106 may contain less than 35 wt.% of C5 components rich with n- pentane and cyclopentane. The desulfurization unit 112 is configured to produce a C5-rich product 114 with reduced sulfur levels that is supplied to a gasoline blending unit 116 to be blended into a gasoline pool. In certain examples, the C5-rich product with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in gasoline pool. Thesulfur content of the light fraction is about 300 ppm and the C5-rich product has reduced sulfur levels of about 1 ppm or less.

[0027] FIG. 2 is a diagrammatic representation of a system 200 for production of a substantially sulfur-free C5-rich product, according to another embodiment of the present disclosure. This system 200 includes a cracker 202 to process C5+ hydrocarbon stream to produce a mixed C5 stream 204 and a hydrogenator 206 in fluid communication with the cracker 202 and configured to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) to produce a treated mixed C5 stream 208 containing paraffins, olefins, and saturated aromatics. In certain examples, the mixed C5 stream contains about 40 wt.% of mixed C5 components. This system 200 includes a fractionating column 210 in fluid communication with the hydrogenator 206 and configured to receive the treated mixed C5 stream 208 and to produce (a) a light fraction 212 containing C1-C4 hydrocarbons and isopentane and (b) a heavy fraction 214 containing C5+ hydrocarbons, n- pentane, and cyclopentane that is recycled to the cracker. This system 200 includes a desulfurization unit 216 in fluid communication with the fractionating column 210 and configured to receive the light fraction 212 and to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction 212. In certain examples, the fractionating column is a deisopentanizer that separates a light fraction containing C1-C4 hydrocarbons and about 35 wt.% to 50 wt.% of isopentanes, and a heavy fraction containing and C5+ hydrocarbons about 9 wt.% to 40 wt.% of n-pentanes, and about 15 wt.% to 45 wt.% of cyclopentanes.

[0028] The desulfurization unit 216 is configured to produce a C5-rich product 218 with reduced sulfur levels that is supplied to a gasoline blending unit 220 to be blended into a gasoline pool. In certain examples, the fuel stream with reduced sulfur levels is rich in C5 components with a high octane number (>94) and can easily be blended in gasoline pool. In certain examples, thedesulfurization unit 216 is a mercaptan oxidation unit configured to produce a C5-rich product 218 with reduced sulfur levels to be blended into a gasoline pool.EXAMPLES

[0029] The examples provided below illustrates selected aspects of the various methods and systems for processing mixed C5 streams to increase the production of olefins.Example 1

[0030] In this example, a mixed C5 stream from a cracker is supplied to a deisopentanizer. Composition of this mixed C5 stream is provided in Table 1. The mixed C5 stream is separated by the deisopentanizer into a light fraction and a heavy fraction. The composition of the light fraction is provided as the overhead stream from the deisopentanizer to the mercaptan oxidation unit in Table 1. The composition of the heavy fraction cycled to the cracker is provided as the deisopentanizer bottom stream in Table 1.

[0031] Table 1 | |Example 2

[0032] In this example, a mixed C5 stream from a cracker is supplied to a hydrogenator to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) to produce a treated mixed C5 stream containing paraffins, olefins, and saturated aromatics. Composition of this mixed C5 stream is provided in Table 2. The mixed C5 stream is separated by the deisopentanizer into a light fraction and a heavy fraction. The composition of the light fraction is provided as the overhead stream from the deisopentanizer to the mercaptan oxidation unit in Table 2. The composition of the heavy fraction cycled to the cracker is provided as the deisopentanizer bottom stream in Table 2.

[0033] Table 2 ] | | ] ] ] ] ] ]

[0034] 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, rangesfrom 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.

[0035] 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 for production of a substantially sulfur- free C5-rich product, the method comprising: fractionating a mixed C5 stream from a cracker to produce (a) a light fraction containing Cl-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclopentane; recycling the heavy fraction to the cracker; desulfurizing the light fraction to produce a substantially sulfur-free C5-rich product containing pentenes and isopentane; and supplying the substantially sulfur-free C5-rich product to a gasoline pool.

2. The method of claim 1, wherein the light fraction contains greater than about 50 wt.% of pentenes and isopentane.

3. The method of claim 1 , wherein the heavy fraction contains about greater than about 50 wt. % of n-pentane and cyclopentane.

4. The method of claim 1, wherein the light fraction contains isopentane / isopentene and other pentenes ranging from 70 wt.% to 85 wt.%.

5. The method of claim 1, wherein the heavy fraction contains n-pentane and cyclopentane / cyclopentene ranging from 75 wt.% to about 95 wt.%.

6. A method for production of a substantially sulfur-free C5-rich product, the method comprising: processing a mixed C5 stream from a cracker through a hydrogenator to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) and produce a treated mixed C5stream; fractionating the treated mixed C5 stream to produce (a) a light fraction containing C1-C4 hydrocarbons and isopentane and (b) a heavy fraction containing C5+ hydrocarbons, n- pentane, and cyclopentane; recycling the heavy fraction to the cracker; desulfurizing the light fraction to produce a substantially sulfur-free C5-rich product containing isopentane; and supplying the substantially sulfur-free C5-rich product to a gasoline pool.

7. The method of claim 6, wherein the light fraction contains greater than about 70 wt. % of n- pentane and isopentane.

8. The method of claim 6, wherein the heavy fraction contains greater than about 35 wt. % of cyclopentane.

9. A system for production of a substantially sulfur-free C5-rich product, the system comprising: a cracker to process a C5+ hydrocarbon stream to produce a mixed C5 stream; a fractionating column in fluid communication with the cracker and configured to receive the mixed C5 stream and to produce (a) a light fraction containing C1-C4 hydrocarbons, isopentane, and isopentene, and (b) a heavy fraction containing C5+ hydrocarbons, n- pentane, and cyclopentane that is recycled to the cracker; and a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction to produce a substantially sulfur-free C5- rich product.

10. The system of claim 9, wherein the light fraction contains greater than about 50 wt. % of pentenes and isopentane.

11. The system of claim 9, wherein the desulfurization unit is a mercaptan oxidation unit configured to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction and produce the substantially sulfur-free C5-rich product to be blended into a gasoline pool.

12. A system for production of a substantially sulfur-free C5-rich product, the system comprising: a cracker to process C5+ hydrocarbon stream to produce a mixed C5 stream; a hydrogenator in fluid communication with the cracker and configured to saturate olefins, diolefins, and unsaturated aromatics (such as styrene) and produce a treated mixed C5 stream; a fractionating column in fluid communication with the hydrogenator and configured to receive the treated mixed C5 stream and to produce (a) a light fraction containing Cl- C4 hydrocarbons and isopentane, and (b) a heavy fraction containing C5+ hydrocarbons, n-pentane, and cyclopentane that is recycled to the cracker; and a desulfurization unit in fluid communication with the fractionating column and configured to receive the light fraction and to remove substantially all mercaptans and other sulfur- containing compounds from the light fraction to produce a substantially sulfur-free C5- rich product.

13. The system of claim 12, wherein the light fraction contains greater than about 70 wt. % of n- pentane and isopentane.

14. The system of claim 12, wherein the heavy fraction contains greater than about 35 wt.% of cyclopentane.

15. The system of claim 12, wherein the desulfurization unit is a mercaptan oxidation unit configured to remove substantially all mercaptans and other sulfur-containing compounds from the light fraction and produce the substantially sulfur-free C5-rich product to be blended into a gasoline pool.

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