WO2020178710A1 - Integrated process for mtbe production from isobutylene with selective butadiene hydrogenation unit - Google Patents

Abstract

Systems and methods for producing MTBE and propylene are disclosed. A C4 hydrocarbon stream from an effluent of hydrocarbon cracking unit is first processed in a selective hydrogenation unit to convert butadiene to 1-butene and 2-butene. The hydrogenated stream is then fed to MTBE synthesis unit to produce MTBE and a MTBE raffinate stream. The raffinate stream is then distilled to produce a first stream comprising n-butane and 2-butene, a second stream comprising isobutane and 1-butane, and a third stream comprising 1-butene and isobutylene. The 2-butene in the first stream is converted to 1-butene. The 1-butene in the second stream is converted to 2-butene. The resulting 1-butene, 2-butene, and 1-butene from the third stream are fed to an olefins conversion technology unit to produce propylene.

Description

INTEGRATED PROCESS FOR MTBE PRODUCTION FROM ISOBUTYLENE WITH SELECTIVE BUTADIENE HYDROGENATION UNIT

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent

Application No. 62/815,264, filed March 7, 2019, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

[0002] The present invention generally relates to production processes for propylene and methyl tert-butyl ether (MTBE). More specifically, the present invention relates to production processes that integrate a MTBE production unit with a propylene production unit for full utilization of a C4 mixture that is obtained from a hydrocarbon cracking unit.

BACKGROUND OF THE INVENTION

[0003] MTBE is used as a gasoline blending component. Typically, MTBE may be made by reacting isobutylene with methanol. The isobutylene for the reaction is usually obtained from a crude C4 stream. A crude C4 stream is a byproduct stream usually produced in a cracking process to produce olefins. The crude C4 stream is usually obtained from the steam cracking of hydrocarbons to produce ethylene. Typically, materials that make up the crude C4 stream have similar boiling points; thus extracting any one of the various components of the crude C4 stream can be difficult and expensive. Therefore, the raffinate from the MTBE production unit, which contains a large amount of 2-butene and 1 -butene, is often recycled back to the steam cracker and converted to low-value hydrocarbons.

[0004] Propylene serves as a building block for other petrochemical products and may be made by different processes. One of those processes, olefins conversion technology (OCT), involves metathesis and isomerization of hydrocarbons to form the propylene. More specifically, olefins conversion technology (OCT) may use 2-butene (or isomerized 1 -butene) and ethylene to produce propylene via metathesis reaction. However, 2-butene in various C4 processing streams, such as the raffinate from the MTBE, is relatively diluted. Therefore, directly using these C4 processing streams can result in low production rate of propylene. [0005] Overall, while production methods for MTBE and propylene exist, the need for improvements in this field persists in light of at least the aforementioned drawbacks for these methods for producing MTBE and propylene.

BRIEF SUMMARY OF THE INVENTION

[0006] A solution to at least some of the above-mentioned problems associated with producing MTBE and propylene has been discovered. The solution resides in an integrated process for producing MTBE and propylene. The integrated process uses a C4 mixture to produce MTBE. The raffinate from the MTBE production process is further processed to enrich 2-butene and 1 -butene. The 2-butene and 1 -butene enriched raffinate is used to produce propylene in an olefins conversion technology unit. This can be beneficial for fully utilizing the high valued 2-butene and 1 -butene from the MTBE raffinate. By way of example, the 2-butene and 1 -butene can be enriched via a series of steps that comprise distilling the raffinate from MTBE production process, further processing the streams produced from the distilling step in a first isomerization unit and a second isomerization unit, and separating isobutane and n-butane from the 2-butene and 1 -butene. The 2-butene and 1- butene enriched stream are used to react with ethylene in an olefins conversion technology (OCT) unit to produce propylene with an increased production rate compared to conventional methods. Furthermore, the integrated process can further include a steam cracking/catalytic cracking process to provide a C4 mixture for MTBE production. Still further, the n-butane and isobutane separated from the 1 -butene and/or 2-butene during the enriching step can be recycled back to the steam cracking and/or catalytic cracking process, or alternatively to an MTBE production complex, specifically as feed to the isomerization unit to produce MTBE, resulting in improved utilization rate for C4 hydrocarbons in the integrated process. Therefore, the integrated processes for producing MTBE and propylene of the present invention provide a technical solution to at least some of the problems associated with the currently available methods for producing MTBE and propylene, such as low utilization rate for 1 -butene and 2-butene, low production rate of propylene, and/or high production costs for both MTBE and propylene.

[0007] Embodiments of the invention include a method of producing propylene. The method comprises flowing a byproduct stream from a MTBE synthesis unit to a distillation unit. The byproduct stream comprises primarily 1 -butene, 2-butene, n-butane, and isobutane, collectively. The method further comprises distilling the byproduct stream in the distillation unit to produce a first stream comprising primarily n-butane and 2-butene, collectively, a second stream comprising primarily isobutane and 1 -butene, collectively, and a third stream comprising primarily 1 -butene and isobutylene, collectively. The method further comprises converting, in a first isomerization unit at least some 2-butene in the first stream to 1 -butene to produce a fourth stream comprising primarily n-butane and 1 -butene collectively. The method further comprises converting, in a second isomerization unit, at least some 1 -butene in the second stream to 2-butene to produce a fifth stream comprising primarily isobutane and 2 -butene. The method further comprises separating 1 -butene from the fourth stream. The method further still comprises separating 2-butene from the fifth stream. The method further comprises reacting the 1 -butene from the fourth stream, 2-butene from the fifth stream, and 1- butene from the third stream, in an olefins conversion technology unit, with ethylene to produce propylene.

[0008] Embodiments of the invention include a method of producing methyl tertiary butyl ether (MTBE) and/or propylene. The method comprises flowing a crude C4 hydrocarbon stream comprising ethyl acetylene, vinyl acetylene, butadiene, isobutylene, isobutane, 1 -butene, 2-butene, and n-butane to a selective hydrogenation unit. The method further comprises hydrogenating, in the selective hydrogenation unit, at least some of the butadiene to produce additional 1 -butene and additional 2-butene. The method further still comprises flowing effluent from the selective hydrogenation unit to an MTBE synthesis unit, the effluent comprising unreacted portions of the C4 hydrocarbon stream, the additional 1- butene, and the additional 2-butene. The method further comprises reacting methanol, in the MTBE synthesis unit, with the isobutylene in the effluent to form MTBE. The method further comprises flowing a byproduct stream from the MTBE synthesis unit to a processing unit, the byproduct stream comprising 1 -butene, 2-butene, n-butane, and isobutane. The method further comprises processing the byproduct stream in the processing unit to produce a first stream comprising primarily isobutane and 2-butene, collectively, a second stream comprising primarily n-butane and 1 -butene, collectively, and a third stream comprising primarily 1 -butene and isobutylene, collectively. The method further comprises separating the first stream into a stream comprising primarily isobutane and a stream comprising primarily 2-butene. The method further comprises flowing the stream comprising primarily 2 -butene to an olefins conversion technology unit. The method further comprises separating the second stream into a stream comprising primarily n-butane and a stream comprising primarily 1 -butene. The method further comprises flowing the stream comprising primarily 1 -butene to the olefins conversion technology unit. The method further comprises flowing the third stream to the olefins conversion technology unit. The method further comprises reacting 2-butene, in the olefins conversion technology unit, with ethylene to produce propylene.

[0009] The following includes definitions of various terms and phrases used throughout this specification.

[0010] The terms “about” or“approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0011] The terms“wt.%,”“vol.%” or“mol.%” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0012] The term“substantially” and its variations are defined to include ranges within

10%, within 5%, within 1%, or within 0.5%.

[0013] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification, include any measurable decrease or complete inhibition to achieve a desired result.

[0014] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0015] The use of the words“a” or“an” when used in conjunction with the term

“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.”

[0016] The words“comprising” (and any form of comprising, such as“comprise” and

“comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0017] The process of the present invention can“comprise,”“consist essentially of,” or“consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0018] The term“primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt. %, 50 mol. %, and 50 vol. %. For example,“primarily” may include 50.1 wt. % to 100 wt. % and all values and ranges there between, 50.1 mol. % to 100 mol. % and all values and ranges there between, or 50.1 vol. % to 100 vol. % and all values and ranges there between.

[0019] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [0021] FIG. 1 shows a schematic diagram for an integrated system for producing

MTBE and propylene, according to embodiments of the invention; and

[0022] FIG. 2 shows a schematic flowchart for an integrated process of producing

MTBE and propylene, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION [0023] The currently available systems for producing MTBE and/or propylene suffer several deficiencies including low utilization rate of 1 -butene and 2-butene, low production rate of propylene, and/or high production costs for both MTBE and propylene. The present invention provides a solution to at least some of these problems. The solution is premised on an integrated production process for MTBE and propylene. The MTBE production process uses a C4 mixture from a steam cracker and/or a catalytic cracker to produce MTBE and a raffinate. The raffinate can be further processed to produce 1 -butene and/or 2-butene enriched streams that are used as feed streams in an olefins conversion technology unit to produce propylene at a higher production rate than conventional methods. The isobutane and n-butane separated from the raffinate are recycled to the steam cracker and/or catalytic cracker to further increase the utilization rate of C4 hydrocarbons, which results in reduced production costs for propylene and MTBE. These and other non-limiting aspects of embodiments of the invention are discussed in further detail in the following sections.

A. Integrated System for Producing MTBE and Propylene

[0024] In embodiments of the invention, the integrated system for producing MTBE and propylene can include a MTBE production unit (typically an MTBE synthesis unit), a processing unit to produce 2-butene and/or 1 -butene enriched stream, and an olefins conversion technology unit. The processing unit can include a distillation unit, a selective hydrogenation unit, a first isomerization unit, a second isomerization unit, and/or two or more separation units. The integrated system can further include a steam cracker and/or a catalytic cracker. With reference to FIG. 1, a schematic diagram is shown of system 100 for producing MTBE and propylene with an improved 2-butene and 1 -butene utilization rate and reduced production costs compared to conventional production systems.

[0025] According to embodiments of the invention, system 100 may include hydrocarbon cracking unit 101 configured to crack a hydrocarbon feed stream to produce cracked stream 11 comprising C4 hydrocarbons and light olefins. In embodiments of the invention, hydrocarbon cracking unit 101 may include a steam cracker or a fluid catalytic cracker. The C4 hydrocarbons may include 1-butene, 2-butene, isobutylene, butadiene, n- butane, isobutane, or combinations thereof. According to embodiments of the invention, cracking unit 101 may be in fluid communication with first separation unit 102 such that cracked stream 11 flows from cracking unit 101 to first separation unit 102. First separation unit 102 may be configured to separate cracked stream 11 to produce crude C4 hydrocarbon stream 12 and a stream comprising light olefins. Non-limiting examples of first separation unit 102 may include one or more distillation columns, adsorption beds, cryogenic separation, and combinations thereof.

[0026] In embodiments of the invention, an outlet of first separation unit 102 may be in fluid communication with first selective hydrogenation unit 103 such that crude C4 hydrocarbon stream 12 flows from separation unit 102 to selective hydrogenation unit 103. According to embodiments of the invention, selective hydrogenation unit 103 may be adapted to selectively hydrogenate butadiene in crude C4 hydrocarbon stream 12 to produce first hydrogenated stream 13 comprising 1 -butene, 2-butene, isobutylene, n-butane, isobutane, or combinations thereof. In embodiments of the invention, first selective hydrogenation unit 103 may include multiple reactor units.

[0027] According to embodiments of the invention, first selective hydrogenation unit

103 may include a first reactor unit, a second reactor unit, and a third reactor unit. The first reactor unit and the second reactor unit can convert butadiene present in crude C4 hydrocarbon stream 12 to 2-butene, cis-2-butene, and/or trans-2-butene. The first and the second reactor units may include a selective hydrogenation catalyst. Exemplary selective hydrogenation catalyst may include palladium with an aluminum base, Pt, Rh, Pd, Ru, Co, Ni, Cu, and combinations thereof. The first reactor unit and the second reactor unit may have substantially the same catalyst. In embodiments of the invention, hydrogen may be injected to crude C4 hydrocarbon stream 12 prior to passing through the first reactor unit. According to embodiments of the invention, hydrogenation of di-olefins to desired mono-olefin ( e.g 1- butene) may be carried out in the third reactor unit. In embodiments of the invention, carbon monoxide may be injected to the third reactor unit to attenuate the catalyst and minimize isomerization from 1 -butene to 2-butene. The carbon monoxide may be injected into the third reactor unit at a rate of 2 ppm based on the feed rate (by weight) to the third reactor unit. In embodiments of the invention, crude C4 hydrocarbon stream 12 may be withdrawn from first selective hydrogenation unit 103 to mitigate the amount of 1 -butene being converted to 2 -butene. Each of the first reactor unit, the second first reactor unit, and the third reactor unit may comprise one or more reactors, which may include one or more fixed bed reactors or one or more fluidized bed reactors. According to embodiments of the invention, both the first reactor unit and the second reactor unit contain a catalyst comprising noble metal on alumina, or combinations thereof. According to embodiments of the invention, crude C4 hydrocarbon stream 12 may further contain propylene, ethyl acetylene, vinyl acetylene, or combinations thereof, which may undergo hydrogenation within first selective hydrogenation unit 103.

[0028] In embodiments of the invention, an outlet of first selective hydrogenation unit

103 may be in fluid communication with MTBE synthesis unit 104 such that first hydrogenated stream 13 flows from first selective hydrogenation unit 103 to MTBE synthesis unit 104. According to embodiments of the invention, MTBE synthesis unit 104 may be adapted to react the isobutylene in first hydrogenated stream 13 with methanol to form MTBE stream 14 comprising primarily MTBE and MTBE raffinate stream 15 comprising primarily 1 -butene, 2-butene, n-butane, isobutane, collectively. In embodiments of the invention, MTBE synthesis unit 104 may contain a catalyst comprising cation exchange resins mounted on styrene divinyl benzene matrix or polymeric support matrix, or combinations thereof.

[0029] In embodiments of the invention, an outlet of MTBE synthesis unit 104 may be in fluid communication with distillation unit 105 such that MTBE raffinate stream 15 flows from MTBE synthesis unit 104 to distillation unit 105. In embodiments of the invention, distillation unit 105 may include one or more distillation columns and/or one or more kinetic distillation columns. In embodiments of the invention, distillation unit 105 may be adapted to distill MTBE raffinate stream 15 to form first stream 16 comprising primarily n-butane and 2-butene, collectively, second stream 17 comprising primarily isobutane and 1- butene, collectively, and third stream 18 comprising 1 -butene and isobutylene, collectively.

[0030] According to embodiments of the invention, a bottom outlet of distillation unit

105 may be in fluid communication with first isomerization unit 106 such that first stream 16 flows from distillation unit 105 to first isomerization unit 106. In embodiments of the invention, isomerization unit 106 may be adapted to convert at least some 2-butene of first stream 16 into 1 -butene and form second hydrogenated stream 19 comprising primarily n- butane and 1 -butene, collectively. In embodiments of the invention, first isomerization unit

106 may be further adapted to produce first recycle stream 20 flowing from first isomerization unit 106 to distillation unit 105. First recycle stream 20 may include unconverted 2-butene and n-butane, or combinations thereof. In embodiments of the invention, first isomerization unit 106 can comprise any type of isomerization unit known in the art, including a catalytic isomerization unit, a non-catalytic isomerization unit, a hydro isomerization unit, a non-hydro-isomerization unit, a selective hydrogenation unit, or combinations thereof. Preferably, first isomerization unit 106 comprises a hydro isomerization unit. In embodiments of the invention, first isomerization unit 106 may include a catalyst selected from the group consisting of 0.01-1.0% Pd/alumina or Pt/alumina, Group VIII metals, Ru, Os, and combinations thereof.

[0031] According to embodiments of the invention, a top outlet of distillation unit

105 may be in fluid communication with second isomerization unit 107 such that second stream 17 flows from distillation unit 105 to second isomerization unit 107. In embodiments of the invention, second isomerization unit 107 may be adapted to convert at least some 1- butene of second stream 17 to 2-butene and form isomerized stream 21 comprising primarily isobutane and 2-butene, collectively. In embodiments of the invention, second isomerization unit 107 may be further adapted to produce second recycle stream 22 flowing from second isomerization unit 107 to distillation unit 105. Second recycle stream 22 may include unconverted 1 -butene, isobutane, or combinations thereof. In embodiments of the invention, second isomerization unit 107 can comprise any type of isomerization unit known in the art, including a catalytic isomerization unit, a non-catalytic isomerization unit, a hydro isomerization unit, a non-hydro-isomerization unit, a selective hydrogenation unit, or combinations thereof. Preferably, second isomerization unit 107 comprises a selective hydrogenation unit. In embodiments of the invention, second isomerization unit 107 may include a catalyst comprising one or more noble metals on alumina.

[0032] In embodiments of the invention, an outlet of first isomerization unit 106 may be in fluid communication with second separation unit 108 such that second hydrogenated stream 19 flows from first isomerization unit 106 to second separation unit 108. According to embodiments of the invention, second separation unit 108 may be adapted to separate n- butane from second hydrogenated stream 19 to produce 1 -butene stream 23 and n-butane stream 24. In embodiments of the invention, second separation unit 108 may include one or more distillation columns, one or more absorption units, or combinations thereof.

[0033] In embodiments of the invention, an outlet of second isomerization unit 107 may be in fluid communication with third separation unit 109 such that isomerized stream 21 flows from second isomerization unit 107 to third separation unit 109. According to embodiments of the invention, third separation unit 109 may be adapted to separate isobutane from isomerized stream 21 to produce 2-butene stream 25 and isobutane stream 26. In embodiments of the invention, third separation unit 109 may include one or more distillation columns, one or more absorption units, or combinations thereof.

[0034] According to embodiments of the invention, a first outlet of second separation unit 108 may be in fluid communication with hydrocarbon cracking unit 101 such that n- butane stream 24 flows from second separation unit 108 to hydrocarbon cracking unit 101. A first outlet of third separation unit 109 may be in fluid communication with hydrocarbon cracking unit 101 such that isobutane stream 26 flows from third separation unit 109 to hydrocarbon cracking unit 101.

[0035] According to embodiments of the invention, a second outlet of second separation unit 108 may be in fluid communication with olefins conversion technology unit 110 such that 1 -butene stream 23 flows from second separation unit 108 to olefins conversion technology unit 110. In embodiments of the invention, a second outlet of third separation unit 109 may be in fluid communication with olefins conversion technology unit 110 such that 2-butene stream 25 flows from third separation unit 109 to olefins conversion technology unit 110. In embodiments of the invention, a middle outlet of distillation unit 105 may be in fluid communication with olefins conversion technology unit 110 such that third stream 18 comprising 1 -butene and isobutylene flows from distillation unit 105 to olefins conversion technology unit 110.

[0036] According to embodiments of the invention, olefins conversion technology unit 110 may be configured to react 2-butene with ethylene to produce propylene. In embodiments of the invention, olefins conversion technology unit 110 may be further adapted to isomerize 1 -butene from 1 -butene stream 23 and 1 -butene from third stream 18 to produce 2 -butene that can be further reacted with ethylene to produce propylene. In embodiments of the invention, olefins conversion technology unit 110 may include a metathesis catalyst for producing propylene from 2-butene. Non-limiting examples of the metathesis catalyst may include a disproportionation catalyst comprising layered and mixed catalyst bed containing magnesium oxide and/or tungsten oxide on silica. Olefins conversion technology unit 110 may further include an isomerization catalyst for converting 1 -butene to 2-butene. Non limiting examples of the isomerization catalyst may include Pd/alumina, Pt/alumina, or other noble metal s/alumina, and combinations thereof. In embodiments of the invention, a purge outlet of olefins conversion technology unit 110 may be in fluid communication with cracking unit 101 such that purge stream 27 flows from olefins conversion technology unit 110 to cracking unit 101.

B. Method for Producing MTBE and Propylene

[0037] Methods of producing MTBE and propylene have been discovered to improve the utilization rate of C4 hydrocarbons from a cracking unit and reduce production cost for propylene via metathesis. As shown in FIG. 2, embodiments of the invention include method 200 for producing MTBE from C4 mixture of a hydrocarbon cracking unit and producing propylene using 2-butene and/or 1 -butene from a raffinate from the MTBE production process. Method 200 may be implemented by system 100, as shown in FIG. 1. According to embodiments of the invention, as shown in block 201, method 200 may include flowing crude C4 hydrocarbon stream 12 to a hydrogenation unit.

[0038] In embodiments of the invention, crude C4 hydrocarbon stream 12 may be produced by cracking a hydrocarbon stream to produce cracked stream 11 in hydrocarbon cracking unit 101 and separating light olefins from cracked stream 11 in first separation unit 102. Crude C4 hydrocarbon stream 12 may comprise ethyl acetylene, vinyl acetylene, butadiene, isobutylene, isobutane, 1-butene, 2-butene, n-butane, or combinations thereof. The hydrogenation unit may be first selective hydrogenation unit 103.

[0039] According to embodiments of the invention, method 200 may further include hydrogenating, in first selective hydrogenation unit 103, at least some of the butadiene to produce additional 1 -butene and additional 2-butene (including cis-2 -butene and trans-2- butene), as shown in block 202. In embodiments of the invention, at block 202, first selective hydrogenation unit 103 may be operated at an operating temperature of 25 to 80 °C and all ranges and values there between including range of 25 to 28 °C, 28 to 31 °C, 31 to 34 °C, 34 to 37 °C, 37 to 40 °C, 40 to 43 °C, 43 to 46 °C, 46 to 49 °C, 49 to 52 °C, 52 to 55 °C, 55 to 58 °C, 58 to 60 °C, 60 to 63 °C, 63 to 66 °C, 66 to 69 °C, 69 to 72 °C, 72 to 75 °C, 75 to 78 °C, 78 to 80 °C. According to embodiments of the invention, reaction conditions of the first reactor unit of first selective hydrogenation unit 103 may include a temperature of 40-70 °C, a pressure of 140 to 400 psig, and a liquid hourly space velocity of 10 to 12 hr ¹. Reaction conditions of the second reactor unit of first selective hydrogenation unit 103 may include a temperature of 50-60 °C, a pressure of 140 to 400 psig, and a liquid hourly space velocity of 150 to 200 hr ¹. Reaction conditions of the third reactor unit of first selective hydrogenation unit 103 may include a temperature of 60-80 °C, a pressure of 250 to 270 psig, and a liquid hourly space velocity of 8 to 10 hr ¹. In embodiments of the invention, the exit stream from the first reactor unit of first selective hydrogenation unit 103 may be 5 to 8 wt.%. The exit stream from the second reactor unit of first selective hydrogenation unit 103 may be 0.5 to 1.5 wt.%. The exit stream from the third reactor unit of first selective hydrogenation unit 103 may be less than 0.01 wt.%. In embodiments of the invention, about 90 wt.% butadiene from crude C4 hydrocarbon stream 12 may be hydrogenated to 1 -butene and/or 2-butene via hydrogenating at block 202.

[0040] According to embodiments of the invention, as shown in block 203, method

200 may further include flowing effluent (first hydrogenated stream 13) from selective hydrogenation unit 103 to MTBE synthesis unit 104. In embodiments of the invention, the effluent (first hydrogenated stream 13) from selective hydrogenation unit 103 comprises unreacted portions of crude C4 hydrocarbon stream 12, the additional 1 -butene, and the additional 2-butene.

[0041] In embodiments of the invention, as shown in block 204, method 200 may further include reacting methanol, in MTBE synthesis unit 104, with the isobutylene in the effluent (first hydrogenated stream 13) to form MTBE. Effluent generated in MTBE synthesis unit 104 may be further separated by a separation unit in MTBE synthesis unit to form MTBE stream 14 and MTBE raffinate stream 15 (byproduct stream). In embodiments of the invention, MTBE raffinate stream 15 may comprise 7 to 30 wt.% 1-butene, 5 to 20 wt.% 2-butene, 30 to 45 wt.% n-butane, and 10 to 25 wt.% isobutane. In embodiments of the invention, at block 204, MTBE synthesis unit 104 may be operated at an operating temperature of 52 to 65 °C and all ranges and values there between including 52 to 54 °C, 54 to 56 °C, 56 to 58 °C, 58 to 60 °C, 60 to 62 °C, 62 to 64 °C, and 64 to 65 °C. An operating pressure of MTBE synthesis unit 104 may be in a range of 8 to 12 bar and all ranges and values there between including 9 bar, 10 bar , and 11 bar.

[0042] According to embodiments of the invention, as shown in block 205, method

200 may further include flowing MTBE raffinate stream 15 (a byproduct stream) from MTBE synthesis unit 104 to distillation unit 105. In embodiments of the invention, the byproduct stream comprises primarily 1 -butene, 2-butene, n-butane, and isobutane, collectively. The byproduct stream may further include at least some isobutylene. [0043] In embodiments of the invention, as shown in block 206, method 200 may further include distilling the byproduct stream (MTBE raffinate stream 15) in distillation unit

105 to produce first stream 16, second stream 17, and third stream 18. According to embodiments of the invention, first stream 16 may comprise about 70 to 80 wt.% n-butane and 20 to 30 wt.% 2-butene. Second stream 17 may comprise 40 to 50 wt.% isobutane and 50 to 60 wt.% 1 -butene. Third stream 18 may comprise 80 to 95 wt.% 1 -butene and 5 to 20 wt.% isobutylene. In embodiments of the invention, the operating temperature of distillation unit 105 at block 206 may be in a range of 40 to 50 °C and all ranges and values there between including 40 to 41 °C, 41 to 42 °C, 42 to 43 °C, 43 to 44 °C, 44 to 45 °C, 45 to 46 °C, 46 to 47 °C, 47 to 48 °C, 48 to 49 °C, and 49 to 50 °C. The operating pressure of the distillation unit 105 at block 206 may be in a range of 6 to 8 bar and all ranges and values there between including 6.1 bar, 6.2 bar, 6.3 bar, 6.4 bar, 6.5 bar, 6.6 bar, 6.7 bar, 6.8 bar, 6.9 bar, 6.9 bar, 7.0 bar, 7.1 bar, 7.2 bar, 7.3 bar, 7.4 bar, 7.5 bar, 7.6 bar, 7.7 bar, 7.8 bar, and 7.9 bar.

[0044] According to embodiments of the invention, as shown in block 207, method

200 may further include converting, in first isomerization unit 106, at least some 2-butene in first stream 16 to 1 -butene to produce fourth stream (second hydrogenated stream 19) comprising primarily n-butane and 1 -butene, collectively. In embodiments of the invention, the fourth stream may include 70 to 80 wt.% n-butane and 20 to 30 wt.% 1-butene. In embodiments of the invention, converting at block 207 may further produce first recycle stream 20 flowing back to distillation unit 105. First recycle stream 20 may comprise unreacted 2-butene and/or at least some n-butane. In embodiments of the invention, first isomerization unit 106 may be operated at an operating temperature of 40 to 80 °C and all ranges and values there between including ranges of 40 to 43 °C, 43 to 46 °C, 46 to 49 °C, 49 to 52 °C, 52 to 55 °C, 55 to 58 °C, 58 to 60 °C, 60 to 63 °C, 63 to 66 °C, 66 to 69 °C, 69 to 72 °C, 72 to 75 °C, 75 to 78 °C, 78 to 80 °C. An operating pressure of first isomerization unit

106 may be in a range of 15 to 20 bar and all ranges and values there between including 16 bar, 17 bar, 18 bar, and 19 bar. Overall, at block 207, 2-butene may have a conversion rate of 50 to 70% on a per pass basis and all ranges and values there between including 50 to 52%, 52 to 54%, 54 to 56%, 56 to 58%, 58 to 60%, 60 to 62%, 62 to 64%, 64 to 66%, 66 to 68%, and 68 to 70%. [0045] According to embodiments of the invention, as shown in block 208, method

200 may further include converting, in second isomerization unit 107, at least some 1 -butene in second stream 17 to 1 -butene to produce a fifth stream (isomerized stream 21) comprising primarily isobutane and 2-butene, collectively. In embodiments of the invention, the fifth stream may include 40 to 50 wt.% isobutane, and 50 to 60 wt.% 2-butene. In embodiments of the invention, converting at block 208 may further produce second recycle stream 22 flowing back to distillation unit 105. Second recycle stream 22 may comprise unreacted 1- butene and/or at least some isobutane. In embodiments of the invention, second isomerization unit 107 may be operated at an operating temperature of 40 to 100 °C and all ranges and values there between including 40 to 43 °C, 43 to 46 °C, 46 to 49 °C, 49 to 52 °C, 52 to 55 °C, 55 to 58 °C, 58 to 61 °C, 61 to 64 °C, 64 to 67 °C, 67 to 70 °C, 70 to 73 °C, 73 to 76 °C, 76 to 79 °C, 79 to 82 °C, 82 to 85 °C, 85 to 88 °C, 88 to 91 °C, 91 to 94 °C, 94 to 97 °C, and 97 to 100 °C,. An operating pressure of second isomerization unit 107 may be in a range of 3 to 8 bar and all ranges and values there between including 3.5 bar, 4 bar, 4.5 bar, 5 bar, 5.5 bar, 6 bar, 6.5 bar, 7 bar and 7.5 bar. Overall, at block 208, 1-butene may have a conversion rate of 50 to 60% per pass and all range and values there between including 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, and 59%..

[0046] According to embodiments of the invention, as shown in block 209, method

200 may further include, in second separation unit 108, separating 1 -butene from the fourth stream (second hydrogenated stream 19) to form 1 -butene stream 23 and n-butane stream 24. In embodiments of the invention, second separation unit 108 may comprise one or more distillation columns, one or more absorption units, or combinations thereof. An operating temperature of second separation unit 108 may be in a range of 40 to 80 °C and all ranges and values there between including ranges of 40 to 43 °C, 43 to 46 °C, 46 to 49 °C, 49 to 52 °C, 52 to 55 °C, 55 to 58 °C, 58 to 60 °C, 60 to 63 °C, 63 to 66 °C, 66 to 69 °C, 69 to 72 °C, 72 to 75 °C, 75 to 78 °C, 78 to 80 °C.. An operating pressure of second separation unit 108 may be in a range of 5 to 8 bar and all ranges and values there between including 5 to 5.5 bar, 5.5 to 6.0 bar, 6.0 to 6.5 bar, 6.5 to 7.0 bar, 7.0 to 7.5 bar, and 7.5 to 8.0 bar. In embodiments of the invention, 1-butene stream 23 may include 80 to 98.5 wt.% 1-butene and all ranges and values there between including ranges of 80 to 82 wt.%, 82 to 84 wt.%, 84 to 86 wt.%, 86 to 88 wt.%, 88 to 90 wt.%, 90 to 92 wt.%, 92 to 94 wt.%, 94 to 96 wt.%, and 96 to 98.5%. [0047] According to embodiments of the invention, as shown in block 210, method

200 may further include, in third separation unit 109, separating 2-butene from the fifth stream (isomerized stream 21) to form 2-butene stream 25 and isobutane stream 26. In embodiments of the invention, third separation unit 109 may comprise one or more distillation columns, one or more absorption units, or combinations thereof. An operating temperature of third separation unit 109 may be in a range of 40 to 80 °C and all ranges and values there between. An operating pressure of third separation unit 109 may be in a range of 5 to 8 bar and all ranges and values there between. In embodiments of the invention, 2- butene stream 25 may include 80 to 98.5 wt.% 2-butene and all ranges and values there between.

[0048] According to embodiments of the invention, at least some 1 -butene from 1- butene stream 23 and 1 -butene from third stream 18 may be isomerized in olefins conversion technology unit 110 to form 2-butene. In embodiments of the invention, as shown in block 211, method 200 may further include reacting 2-butene, in olefins conversion technology unit 110, with ethylene via metathesis to produce a product stream comprising propylene. According to embodiments of the invention, the 2-butene reacted with ethylene at block 211 may include 2-butene obtained from isomerization the 1-butene of 1-butene stream 23, 2- butene of 2-butene stream 25 (the fifth stream), 2-butene obtained from isomerization the 1- butene of third stream 18, or combinations thereof.

[0049] In embodiments of the invention, at block 211, the operating temperature for metathesis in olefins conversion technology unit 110 may be in a range of 240 to 380 °C and all ranges and values there between including ranges of 240 to 247 °C, 247 to 254 °C, 254 to 261 °C, 261 to 268 °C, 268 to 275 °C, 275 to 282 °C, 282 to 289 °C, 289 to 296 °C, 296 to 303 °C, 303 to 310 °C, 310 to 317 °C, 317 to 324 °C, 324 to 331 °C, 331 to 338 °C, 338 to 345 °C, 345 to 352 °C, 352 to 359 °C, 359 to 366 °C, 366 to 373 °C, and 373 to 380 °C. The operating pressure for metathesis in olefins conversion technology unit 110 may be in a range of 30 to 40 bar and all ranges and values there between including 31 bar, 32 bar, 33 bar, 34 bar, 35 bar, 36 bar, 37 bar, 38 bar, and 39 bar. According to embodiments of the invention, a weight hourly space velocity for olefins conversion technology unit 110 at block 211 may be in a range of 5 to 10 hr ¹ and all ranges and values there between including 5 to 5.5 hr ¹, 5.5 to 6.0 hr ¹, 6.0 to 6.5 hr ¹, 6.5 to 7.0 hr ¹, 7.0 to 7.5 hr ¹, 7.5 to 8.0 hr ¹, 8.0 to 8.5 hr ¹, 8.5 to 9.0 hr ¹, 9.0 to 9.5 hr ¹, and 9.5 to 10.0 hr ¹. In embodiments of the invention, reaction conditions at block 211 may further include a weight ratio of 2-butene to ethylene feeding to olefins conversion technology unit 110 of 2.3 to 2.5 and all ranges and values there between including ranges of 2.3 to 2.31, 2.31 to 2.32, 2.32 to 2.33, 2.33 to 2.34, 2.34 to 2.35, 2.35 to 2.36, 2.36 to 2.37, 2.37 to 2.38, 2.38 to 2.39, 2.39 to 2.40, 2.40 to 2.41, 2.41 to 2.42, 2.42 to 2.43, 2.43 to 2.44, 2.44 to 2.45, 2.45 to 2.46, 2.46 to 2.47, 2.47 to 2.48, 2.48 to 2.49, and 2.49 to 2.5.

[0050] According to embodiments of the invention, the effluent stream generated in olefins conversion technology unit 110 may comprise 99 to 99.89 wt.% propylene and all ranges and values there between. In embodiments of the invention, the product stream of olefins conversion technology unit 110 may further include 0.02 to 0.2 wt.% propane. The effluent stream generated in olefins conversion technology unit 110 may be further separated by a separation unit of olefins conversion technology unit 110 into a Cs+ stream, a hydrogen stream, a C4 byproduct stream, and a propylene stream. In embodiments of the invention, isobutane stream 26 and n-butane stream 24 may be flowed back to cracking unit 101. A purge stream from olefins conversion technology unit 110 may be flowed to cracking unit 101. The purge stream may comprise 70-80% C4 olefm/alkanes, 18-30% C5+, less than 1 wt.% C3, or combinations thereof.

[0051] Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0052] In the context of the present invention, at least the following 17 embodiments are disclosed. Embodiment 1 is a method of producing propylene. The method includes flowing a byproduct stream from a MTBE synthesis unit to a distillation unit, the byproduct stream containing primarily 1 -butene, 2-butene, n-butane, and isobutane, collectively. The method further includes distilling the byproduct stream in the distillation unit to produce a first stream containing primarily n-butane and 2-butene, collectively, a second stream containing primarily isobutane and 1 -butene, collectively, and a third stream containing primarily 1 -butene and isobutylene, collectively. The method also includes converting, in a first isomerization unit at least some 2-butene in the first stream to 1 -butene to produce a fourth stream containing primarily n-butane and 1 -butene collectively. In addition, the method includes converting, in a second isomerization unit, at least some 1 -butene in the second stream to 2-butene to produce a fifth stream containing primarily isobutane and 2- butene. The method further includes separating 1 -butene from the fourth stream, separating 2 -butene from the fifth stream, and reacting the 2-butene from the fifth stream, in an olefins conversion technology unit, with ethylene to produce propylene. Embodiment 2 is the method of embodiment 1, further including the steps of isomerizing at least some of the 1- butene from the fourth stream and the 1 -butene from the third stream in the olefins conversion technology unit to form 2-butene. The method further includes reacting the 2- butene formed from the 1 -butene of the fourth stream and the 1 -butene of the third stream with ethylene in the olefins conversion technology unit to produce additional propylene. Embodiment 3 is the method of either of embodiments 1 or 2, wherein the byproduct stream from the MTBE synthesis unit is produced by a method including flowing a crude C4 hydrocarbon stream containing ethyl acetylene, vinyl acetylene, butadiene, isobutylene, isobutane, 1 -butene, 2-butene, and n-butane to a selective hydrogenation unit. The method also includes hydrogenating, in the selective hydrogenation unit, at least some of the butadiene to produce additional 1 -butene and additional 2-butene. In addition, the method includes flowing effluent from the selective hydrogenation unit to an MTBE synthesis unit, the effluent containing unreacted portions of the C4 hydrocarbon stream, the additional 1- butene, and the additional 2-butene. The method further includes reacting methanol, in the MTBE synthesis unit, with the isobutylene in the effluent to form MTBE. Embodiment 4 is the method of embodiment 3, wherein the crude C4 hydrocarbon stream includes an effluent stream from a steam cracker and/or a catalytic cracker. Embodiment 5 is the method of either of embodiments 3 or 4, wherein substantially all the butadiene is converted to the additional 1 -butene and the additional 2-butene in the selective hydrogenation unit. Embodiment 6 is the method of any of embodiments 3 to 5, wherein the selective hydrogenation unit includes three reactor units. Embodiment 7 is the method of embodiment 6, wherein the three reactor units include a first and a second reactor unit configured to convert butadiene to 2-butene. Embodiment 8 is the method of either embodiments 6 or 7, wherein the three reactor units include a third reactor unit configured to convert butadiene to 1 -butene. Embodiment 9 is the method of any of embodiments 1 to 8, wherein the first isomerization unit is operated at an operating temperature of 40 to 80 °C and an operating pressure of 15 to 20 bar. Embodiment 10 is the method of any of embodiments 1 to 9, wherein, in the first isomerization unit, the 2- butene from the first stream is converted at a conversion rate of 50 to 70%. Embodiment 11 is the method of any of embodiments 1 to 10, wherein the second isomerization unit contains a catalyst selected from a group consisting of one or more noble metals on alumina, and combinations thereof. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the second isomerization unit is operated at an operating temperature of 40 to 100 °C and an operating pressure of 3 to 8 bar. Embodiment 13 is the method of any of embodiments 1 to 12, wherein, in the second isomerization unit, the 1-butene from the second stream is converted at a conversion rate of 50 to 60%. Embodiment 14 is the method of any of embodiments 1 to 13, wherein the converting in the first isomerization unit further produces a first recycle stream containing n-butane and butene-2 recycled to the distillation unit. Embodiment 15 is the method of any of embodiments 1 to 14, wherein the converting in the second isomerization unit further produces a second recycle stream containing 1 -butene and isobutane recycled to the distillation unit. Embodiment 16 is the method of any of embodiments 1 to 15, wherein the n-butane separated from the fourth stream and/or the isobutane separated from the fifth stream are flowed to a steam cracker and/or a catalytic cracker. Embodiment 17 is the method of any of embodiments 1 to 16, wherein the olefins conversion technology unit contains a catalyst for isomerizing 1 -butene to form 2-butene and a catalyst for converting 2-butene and ethylene to propylene.

[0053] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A method of producing propylene, the method comprising: flowing a byproduct stream from a MTBE synthesis unit to a distillation unit, the byproduct stream comprising primarily 1 -butene, 2-butene, n-butane, and isobutane, collectively;

distilling the byproduct stream in the distillation unit to produce a first stream comprising primarily n-butane and 2-butene, collectively, a second stream comprising primarily isobutane and 1 -butene, collectively, and a third stream comprising primarily 1- butene and isobutylene, collectively; converting, in a first isomerization unit at least some 2-butene in the first stream to 1- butene to produce a fourth stream comprising primarily n-butane and 1 -butene collectively; converting, in a second isomerization unit, at least some 1 -butene in the second stream to 2-butene to produce a fifth stream comprising primarily isobutane and 2-butene; separating 1 -butene from the fourth stream; separating 2-butene from the fifth stream; and reacting the 2-butene from the fifth stream, in an olefins conversion technology unit, with ethylene to produce propylene.

2. The method of claim 1, further comprising the steps of: isomerizing at least some of the 1 -butene from the fourth stream and the 1 -butene from the third stream in the olefins conversion technology unit to form 2-butene; and reacting the 2-butene formed from the 1 -butene of the fourth stream and the 1 -butene of the third stream with ethylene in the olefins conversion technology unit to produce additional propylene.

3. The method of any of claims 1 and 2, wherein the byproduct stream from the MTBE synthesis unit is produced by a method comprising: flowing a crude C4 hydrocarbon stream comprising ethyl acetylene, vinyl acetylene, butadiene, isobutylene, isobutane, 1 -butene, 2-butene, and n-butane to a selective hydrogenation unit; hydrogenating, in the selective hydrogenation unit, at least some of the butadiene to produce additional 1 -butene and additional 2-butene; flowing effluent from the selective hydrogenation unit to an MTBE synthesis unit, the effluent comprising unreacted portions of the C4 hydrocarbon stream, the additional 1 -butene, and the additional 2-butene; and reacting methanol, in the MTBE synthesis unit, with the isobutylene in the effluent to form MTBE.

4. The method of claim 3, wherein the crude C4 hydrocarbon stream comprises an effluent stream from a steam cracker and/or a catalytic cracker.

5. The method of claim 3, wherein substantially all the butadiene is converted to the additional 1 -butene and the additional 2-butene in the selective hydrogenation unit.

6. The method of claim 3, wherein the selective hydrogenation unit comprises three reactor units.

7. The method of claim 6, wherein the three reactor units include a first and a second reactor unit configured to convert butadiene to 2-butene.

8. The method of claim 6, wherein the three reactor units include a third reactor unit configured to convert butadiene to 1 -butene.

9. The method of any of claims 1 to 2, wherein the first isomerization unit is operated at an operating temperature of 40 to 80 °C and an operating pressure of 15 to 20 bar.

10. The method of any of claims 1 to 2, wherein, in the first isomerization unit, the 2- butene from the first stream is converted at a conversion rate of 50 to 70%.

11. The method of any of claims 1 to 2, wherein the second isomerization unit comprises a catalyst selected from a group consisting of one or more noble metals on alumina, and combinations thereof.

12. The method of any of claims 1 to 2, wherein the second isomerization unit is operated at an operating temperature of 40 to 100 °C and an operating pressure of 3 to 8 bar.

13. The method of any of claims 1 to 2, wherein, in the second isomerization unit, the 1- butene from the second stream is converted at a conversion rate of 50 to 60%.

14. The method of any of claims 1 to 2, wherein the converting in the first isomerization unit further produces a first recycle stream comprising n-butane and butene-2 recycled to the distillation unit.

15. The method of any of claims 1 to 2, wherein the converting in the second isomerization unit further produces a second recycle stream comprising 1 -butene and isobutane recycled to the distillation unit.

16. The method of any of claims 1 to 2, wherein the n-butane separated from the fourth stream and/or the isobutane separated from the fifth stream are flowed to a steam cracker and/or a catalytic cracker.

17. The method of any of claims 1 to 2, wherein the olefins conversion technology unit comprises a catalyst for isomerizing 1 -butene to form 2-butene and a catalyst for converting 2-butene and ethylene to propylene.