Removing c3 light hydrocarbons from lpg feedstock of a butane isomerization unit

Abstract

Systems and processes for processing C3 and C4 hydrocarbon mixtures are disclosed. The C3 and C4 hydrocarbon mixture is first processed in an isomerization unit to isomerize n-butane to form isobutane. The resulting isomerization unit effluent stream, which generally comprises primarily isobutane and C3 hydrocarbons, is passed to a separation unit configured to separate the effluent stream to form a C3 stream comprising C1 to C3 hydrocarbons and a C4 stream comprising primarily isobutane. The isobutane in the C4 stream is further dehydrogenated to form isobutene, which is further passed to an MTBE synthesis unit as a feedstock to produce MTBE.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to European Patent Application No. 20186357.8, filed on 17 July 2020, the entire contents of which are hereby incorporated by reference. Technical Field

[0003] This invention generally relates to a method for producing alkyl tert-butyl ethers. More specifically, this invention relates to a method for producing alkyl tert-butyl ethers using liquefied petroleum gas as a feedstock. Background Technology

[0004] MTBE is an organic compound used as an additive in gasoline to increase its octane rating. Since around 1970, MTBE has been synthesized by the etherification of isobutylene with methanol in the presence of an acidic catalyst. The isobutylene used in MTBE synthesis can be obtained from C4 hydrocarbons. Typically, isobutylene and methanol are fed into a fixed-bed reactor to produce an effluent containing MTBE. The effluent is then fed into a reaction column, where the remaining isobutylene reacts with additional methanol to produce more MTBE.

[0005] One source of C4 hydrocarbons used in MTBE production is liquefied petroleum gas (LPG), which primarily comprises C4 and C3 hydrocarbons. The LPG is processed in an isomerization unit and then by a dehydrogenation unit to produce isobutylene. The effluent from the dehydrogenation unit then flows to the MTBE synthesis unit, where it reacts with methanol to produce MTBE. However, when using LPG as feedstock, the reaction efficiency in the isomerization and / or dehydrogenation units is relatively low, resulting in higher production costs for MTBE.

[0006] Overall, while systems and methods exist for producing MTBE from mixtures of C4 and C3 hydrocarbons (e.g., liquefied petroleum gas), this field still requires improvement due to at least the aforementioned drawbacks of conventional systems and methods. Summary of the Invention

[0007] A solution has been found to the aforementioned problems associated with systems and methods for producing MTBE from a mixture of C4 and C3 hydrocarbons (e.g., liquefied petroleum gas). The solution lies in a method for processing a hydrocarbon mixture containing C4 and C3 hydrocarbons. This method includes treating the hydrocarbon mixture in an isomerization unit to produce isobutane, separating the effluent from the isomerization unit to form a C3 feed stream containing propane and a C4 feed stream containing isobutane, and dehydrogenating the isobutane in the C4 feed stream in a dehydrogenation unit to produce isobutene. The effluent from the dehydrogenation unit is further fed into an etherification unit for the production of alkyl tert-butyl ethers. This is advantageous for at least reducing the inert portion of the feed stream flowing into the isomerization unit and / or dehydrogenation unit, thereby improving the reaction efficiency of isobutane dehydrogenation. Furthermore, the disclosed method can reduce or eliminate large amounts of propane in the dehydrogenation unit effluent stream, resulting in a feed stream with a higher concentration of isobutene flowing into the MTBE synthesis unit. Therefore, the disclosed method can improve the reaction efficiency in the etherification unit and reduce the amount of gas recycled back to the dehydrogenation unit, thereby reducing the production cost of alkyl tert-butyl ethers. Thus, the system and method of the present invention provide technical solutions to at least some of the problems associated with conventional systems and methods for producing alkyl tert-butyl ethers.

[0008] Embodiments of the present invention include a method for processing a hydrocarbon mixture. The method includes processing a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit under reaction conditions sufficient to isomerize n-butane to produce isobutane and form an isomerization unit effluent comprising propane, isobutane, or a combination thereof. The method further includes separating the isomerization unit effluent to form a C3 stream comprising propane and a C4 stream comprising isobutane. The method further includes steam cracking the propane in the C3 stream under reaction conditions sufficient to produce propylene. The method further includes dehydrogenating the isobutane in the C4 stream in a dehydrogenation unit to produce isobutene in the dehydrogenation unit effluent. The method further includes reacting the isobutene in the dehydrogenation unit effluent with an alkanol in an etherification unit under reaction conditions sufficient to produce alkyl tert-butyl ethers in the etherification unit effluent, in the presence of an etherification catalyst.

[0009] Embodiments of the present invention include a method for processing a hydrocarbon mixture. The method includes processing a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit under reaction conditions sufficient to isomerize n-butane to produce isobutane and form an isomerization unit effluent comprising propane, isobutane, or a combination thereof. The method includes separating a second hydrocarbon mixture comprising propane, n-butane, and isobutane in a second separation unit to generate an overhead stream generally comprising propane and isobutane, and a first C4 stream primarily comprising n-butane. The method includes combining the overhead stream and the isomerization unit effluent to form a combined stream. The method includes separating the combined stream to form a C3 stream primarily comprising propane and a second C4 stream comprising isobutane. The method includes dehydrogenating the isobutane in the second C4 stream in a dehydrogenation unit to generate isobutene in the dehydrogenation unit effluent. The method includes reacting isobutylene from the dehydrogenation unit effluent with an alkanol in an etherification unit under reaction conditions sufficient to generate alkyl tert-butyl ethers in the etherification effluent.

[0010] Embodiments of the present invention include a method for processing a hydrocarbon mixture. The method includes processing a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit under reaction conditions sufficient to isomerize n-butane to produce isobutane and form an isomerization unit effluent comprising propane, isobutane, or a combination thereof. The method includes separating a second hydrocarbon mixture comprising propane, n-butane, and isobutane in a second separation unit to generate an overhead stream generally comprising propane and isobutane, and a first C4 stream comprising primarily n-butane. The method includes steam cracking the first C4 stream to produce olefins and / or aromatics. The method includes combining the overhead stream and the isomerization unit effluent to form a combined stream. The method includes separating the combined stream to form a C3 stream comprising primarily propane and a second C4 stream comprising isobutane. The method includes steam cracking the second C3 stream to produce olefins and / or aromatics. The method includes dehydrogenating isobutane in a second C4 feed stream in a dehydrogenation unit to generate isobutene in the dehydrogenation unit effluent. The method also includes reacting isobutene from the dehydrogenation unit effluent with methanol in an etherification unit under reaction conditions sufficient to generate methyl tert-butyl ether in the etherification effluent, in the presence of an etherification catalyst.

[0011] The following includes definitions of various terms and expressions used in this specification.

[0012] The terms “about” or “approximately” are defined as close to what a person skilled in the art would understand. In one non-limiting embodiment, these terms are defined as less than 10%, preferably less than 5%, more preferably less than 1%, and most preferably less than 0.5%.

[0013] The terms "weight%", "volume%", or "molar%" refer to the weight, volume, or mole percentage of a component, based on the total weight, total volume, or total number of moles of the material containing that component. In a non-limiting example, 10 moles of component in 100 moles of material is 10 moles of the component.

[0014] The term “basically” and its variations are defined as including ranges of up to 10%, up to 5%, up to 1%, or up to 0.5%.

[0015] When used in the claims and / or description, the terms “suppress” or “reduce” or “prevent” or “avoid” or any variation thereof include any measurable reduction or complete suppression to achieve the desired result.

[0016] The term “effective” as used in this specification and / or claims means sufficient to achieve the desired, anticipated, or anticipated result.

[0017] When used with the terms “comprising,” “including,” “containing,” or “having” in the claims or specification, the use of “a” or “a type” may mean “a type,” but it is also consistent with the meaning of “a type or more types,” “at least one type,” and “a type or more than one type.”

[0018] The words “contain,” “have,” “include,” or “contain” are inclusive or open-ended and do not exclude additional, unmentioned elements or methods or steps.

[0019] The method of the present invention may "comprise", "consistently constitute" or "consistent with" specific ingredients, components, compositions, etc. disclosed throughout the specification.

[0020] The term "major" as used in this specification and / or claims means greater than any one of 50 wt%, 50 mol%, and 50 vol%. For example, "major" can include all values ​​and ranges from 50.1 wt% to 100 wt%, 50.1 mol% to 100 mol%, or 50.1 vol% to 100 vol%.

[0021] Other objects, features, and advantages of the present invention will become apparent from the following drawings, detailed description, and embodiments. However, it should be understood that while the drawings, detailed description, and embodiments are given by way of illustration only, they are not intended to be limiting. Furthermore, it is conceivable that changes and modifications within the spirit and scope of the invention will be clearly apparent to those skilled in the art from this detailed description. In further embodiments, features from a particular embodiment may be combined with features from other embodiments. For example, a feature from one embodiment may be combined with features from any other embodiment. In further embodiments, additional features may be added to the specific embodiments described herein. Attached Figure Description

[0022] For a more complete understanding, please now refer to the following description in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 A schematic diagram of a system for producing MTBE according to an embodiment of the present invention is shown; and

[0024] Figure 2 A schematic flowchart of a method for producing MTBE according to an embodiment of the present invention is shown. Detailed Implementation

[0025] Currently, MTBE can be produced by sequentially processing a mixture of C3 and C4 hydrocarbons in an isomerization unit and a dehydrogenation unit. The effluent from the dehydrogenation unit, which contains isobutene, is then fed into an MTBE synthesis unit to produce MTBE. However, the C3 hydrocarbons and light hydrocarbons (e.g., methane and C2 hydrocarbons) in the hydrocarbon mixture are inert components, diluting the C4 hydrocarbon reactants in each reaction unit, thereby reducing reaction efficiency and increasing energy consumption for MTBE production. This invention provides a solution to this problem. The solution presupposes a system and method for processing hydrocarbons, which includes separating C3 and / or C1 to C2 hydrocarbons from the hydrocarbon mixture prior to processing in the isomerization and / or dehydrogenation units, resulting in a higher concentration of isobutane in the feed stream compared to conventional methods, thereby achieving higher reaction efficiency in the feed stream of the dehydrogenation unit. Furthermore, the separated C3 and / or C1 to C2 hydrocarbons can be processed in a steam cracking unit to produce light olefins and / or aromatics, thereby improving the utilization and overall value of the C3 and C4 hydrocarbon mixture. These and other non-limiting aspects of the invention will be discussed in further detail in the following sections.

[0026] A. Systems for processing mixtures of C3 and C4 hydrocarbons

[0027] In embodiments of the present invention, the system for processing hydrocarbon mixtures containing C3 and C4 hydrocarbons includes an isomerization unit, a separation unit, a dehydrogenation unit, a steam cracking unit, and an MTBE synthesis unit. Notably, compared to conventional systems, this system can reduce energy consumption and improve MTBE production efficiency. (See also...) Figure 1 The diagram shows a schematic of a system 100 for producing MTBE using a mixture of C3 and C4 as raw materials.

[0028] According to an embodiment of the invention, system 100 includes an isomerization unit 101. The isomerization unit 101 may be configured to isomerize at least some of the n-butane in a first feed stream 11 to produce isobutane. In an embodiment of the invention, the first feed stream 11 comprises a mixture of C3 and C4 hydrocarbons. The first feed stream 11 may also contain methane and C2 hydrocarbons. According to an embodiment of the invention, the first feed stream 11 is a liquefied petroleum gas stream. The first feed stream 11 may contain 0 to 7 wt% propane, 60 to 80 wt% isobutane, and 20 to 30 wt% n-butane. According to an embodiment of the invention, the isomerization unit 101 may be further configured to separate unreacted n-butane from isobutane to generate an isomerization unit effluent stream 12 primarily comprising isobutane and C3 hydrocarbons. The isomerization unit 101 may comprise a fixed-bed reactor, a continuous catalytic converter, and / or an adiabatic or cooled isothermal converter. In an embodiment of the present invention, the isomerization device 101 includes a catalyst, which includes Pt / AlCl3 / Al2O3, Pt / AlCl3 / zeolite, and Pt / SO4. 2- -ZrO2, SO4 2- / ZrO2-Al2O3, or any combination thereof. In an embodiment of the invention, the isomerization unit 101 further includes an isobutane removal tower configured to separate isobutane and C3 hydrocarbons from unreacted n-butane to generate an unreacted n-butane stream 22 mainly containing n-butane and an isomerization unit effluent stream 12 mainly containing isobutane.

[0029] According to an embodiment of the invention, system 100 includes a first separation unit 102 configured to separate a second feed stream 13 comprising a mixture of C3 and C4 hydrocarbons to form an overhead stream 14 comprising one or more C3 hydrocarbons and isobutane, and a first C4 stream 15 comprising primarily n-butane. The second feed stream 13 may have substantially the same composition as the first feed stream 11. The first separation unit 102 may include a distillation column. The distillation column may be an isobutane removal column. In an embodiment of the invention, the overhead stream 14 further comprises methane and / or one or more C2 hydrocarbons. In an embodiment of the invention, the outlet of the first separation unit 102 is in fluid communication with the inlet of a first steam cracking unit 103, such that the first C4 stream 15 flows from the first separation unit 102 to the first steam cracking unit 103. The first steam cracking unit 103 may be configured to steam crack the hydrocarbons comprising the n-butane of the first C4 stream 15 to produce (1) light olefins comprising propylene and ethylene, and / or (2) aromatics comprising benzene. In an embodiment of the invention, the outlet of the isomerization unit 101 is in fluid communication with the inlet of the first steam cracking unit 103, such that unreacted n-butane feed stream 22 flows from the isomerization unit 101 to the first steam cracking unit 103. Alternatively or concurrently with respect to the flow to the first steam cracking unit 103, the unreacted n-butane feed stream 22 may be combined with the first C4 feed stream 15 before flowing into the first steam cracking unit 103.

[0030] According to an embodiment of the invention, the outlet of the isomerization unit 101 may be in fluid communication with the inlet of the second separation unit 104. The outlet of the first separation unit 102 may be in fluid communication with the inlet of the second separation unit 104. In an embodiment of the invention, the first overhead stream 14 and the isomerization unit effluent stream 12 may be combined into a combined stream 16, which is fed into the second separation unit 104. Alternatively, the overhead stream 14 and the isomerization unit effluent stream 12 may flow separately into the second separation unit 104. The second separation unit 104 may be configured to separate the combined stream 16 or the isomerization unit effluent stream 12 to form a C3 stream 17 containing one or more C3 hydrocarbons and a second C4 stream 18 mainly containing isobutane. In an embodiment of the invention, the second separation unit 104 includes a propane removal column. The C3 stream 17 may also contain C1 to C2 hydrocarbons. In an embodiment of the invention, the outlet of the second separation device 104 is in fluid communication with the second steam cracking device 107, such that the C3 feed stream 17 flows from the second separation device 104 to the second steam cracking device 107. The second steam cracking device 107 may include a propane steam cracker configured to crack the hydrocarbons in the C3 feed stream 17 to produce light olefins (e.g., ethylene and propylene) and / or aromatics (e.g., benzene).

[0031] According to an embodiment of the invention, the outlet of the second separation unit 104 is in fluid communication with the dehydrogenation unit 105, such that the second C4 feed stream 18 flows from the second separation unit 104 to the dehydrogenation unit 105. The dehydrogenation unit 105 is configured to dehydrogenate the isobutane in the second C4 feed stream 18 to generate isobutene in the dehydrogenation unit effluent stream 19. The dehydrogenation unit effluent stream 19 may also contain unreacted isobutane. In an embodiment of the invention, the dehydrogenation unit 105 includes one or more fixed-bed reactors, one or more fluidized-bed reactors, and / or one or more continuous catalytic converters. The dehydrogenation unit 105 may contain a dehydrogenation catalyst containing chromium oxide / alumina, Pt / alumina, or any combination thereof.

[0032] According to an embodiment of the invention, the outlet of the dehydrogenation unit 105 may be in fluid communication with the inlet of the etherification unit 106, such that the effluent stream 19 from the dehydrogenation unit flows to the etherification unit 106. In an embodiment of the invention, the etherification unit 106 is configured to react the isopropylene from the effluent stream 19 of the dehydrogenation unit with methanol under reaction conditions sufficient to generate a product stream 20 containing MTBE and a recycle stream 21 containing isobutane. The etherification unit 106 may include an MTBE synthesis reactor and / or an ethyl tert-butyl ether (ETBE) synthesis reactor, and an effluent separator configured to separate the effluent from the MTBE synthesis reactor to form the product stream 20 and the recycle stream 21. The MTBE and / or ETBE synthesis reactor may contain a catalyst for catalyzing the MTBE and / or ETBE synthesis reaction, the catalyst comprising a cation exchange resin, sulfonated styrene-divinylbenzene, a cation exchange resin packed with a polystyrene polymer, or a combination thereof. In an embodiment of the present invention, the outlet of the etherification unit 106 is in fluid communication with the inlet of the dehydrogenation unit 105, so that the recirculated feed stream 21 flows back to the dehydrogenation unit 105.

[0033] According to an embodiment of the invention, the first separation unit 102 and the first steam cracking unit 103 are part of production facility 1, which may include a mixed butane cracker. The isomerization unit 101, the second separation unit 104, the dehydrogenation unit 105, and the etherification unit 106 may be part of production facility 2, which may include an MTBE synthesis unit. In an embodiment of the invention, the second steam cracking unit 107 may be part of production facility 3, which includes a propane cracking unit.

[0034] B. Methods for treating mixtures of C3 and C4 hydrocarbons

[0035] Methods for processing mixtures of C3 and C4 hydrocarbons have been discovered. For example... Figure 2As shown, embodiments of the present invention include a method 200 for processing a mixture of C3 and C4 hydrocarbons to produce MTBE, which improves efficiency and reduces energy consumption compared to conventional methods. Method 200 can be implemented by system 100, such as... Figure 1 As shown, as described above.

[0036] According to an embodiment of the invention, as shown in block 201, method 200 includes treating a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit 101 under reaction conditions sufficient to isomerize n-butane, to generate isobutane in an isomerization unit effluent stream 12. In an embodiment of the invention, the treatment at block 201 may include reacting the n-butane in the first feed stream 11 with isobutane in a reactor of the isomerization unit 101 to generate isobutane, and separating the mixture from the reactor of the isomerization unit 101 via a deisobutane column of the isomerization unit 101 to generate isobutane in the isomerization unit effluent stream 12 and an unreacted n-butane stream 22. The first feed stream 11 may contain 0 to 7 wt% propane, 60 to 80 wt% isobutane, and 20 to 30 wt% n-butane. The first feed stream 11 may also contain methane and / or C2 hydrocarbons. In an embodiment of the invention, the first feed stream 11 comprises liquefied petroleum gas. The effluent 12 from the isomerization unit may contain propane, isobutane, or any combination thereof. The effluent stream 12 from the isomerization unit may contain 95 to 99.5% by weight of isobutane and all ranges and values ​​therebetween, including the ranges of 95 to 95.5% by weight, 95.5 to 96% by weight, 96 to 96.5% by weight, 96.5 to 97% by weight, 97 to 97.5% by weight, 97.5 to 98% by weight, 98 to 98.5% by weight, 98.5 to 99% by weight, and 99 to 99.5% by weight.

[0037] The reaction conditions in the reactor of isomerization unit 101, at frame 201, may include a reaction temperature of 125°C to 175°C and all ranges and values ​​therebetween. The reaction conditions in isomerization unit 101 at frame 201 may also include a reaction pressure of 20 to 30 bar and all ranges and values ​​therebetween. The reaction conditions in isomerization unit 101 at frame 201 may also include a reaction time of 4 to 6 hours. -1 The heavy space velocity within the range, and all ranges and values ​​in between.

[0038] According to an embodiment of the invention, as shown in block 202, method 200 includes separating a second hydrocarbon mixture comprising propane, n-butane, and isobutane in a first separation unit 102 to generate an overhead stream 14 comprising primarily propane and isobutane, and a first C4 stream 15 comprising n-butane. In an embodiment of the invention, the second feed stream 13 comprises 0 to 7 wt% propane, 60 to 80 wt% isobutane, and 20 to 30 wt% n-butane. The second feed stream 13 may also comprise methane and / or C2 hydrocarbons. According to an embodiment of the invention, the second feed stream 13 comprises liquefied petroleum gas.

[0039] In an embodiment of the invention, the first separation unit 102 includes a distillation column. The distillation column can operate in a top dew point range of 40°C to 55°C, a bottom temperature range of 60°C to 90°C, and an operating pressure range of 7 bar to 8.5 bar. The top feed stream 14 can contain 0 to 21 wt% propane and 79 to 100 wt% isobutane. According to an embodiment of the invention, as shown in block 203, method 200 includes steam cracking the hydrocarbons of the first C4 feed stream 15 in a first steam cracking unit 103 under steam cracking conditions sufficient to produce light olefins and / or aromatics. Non-limiting examples of light olefins may include propylene and ethylene. Non-limiting examples of aromatics may include benzene. At block 203, the first steam cracking unit 103 can operate at a temperature of 750°C to 890°C and a residence time of 0.1 seconds to 0.5 seconds. In an embodiment of the present invention, unreacted n-butane feed stream 22 is fed into a first steam cracking unit 103, and the n-butane steam of the unreacted n-butane feed stream 22 is cracked to generate light olefins and / or aromatics.

[0040] According to an embodiment of the invention, as shown in block 204, method 200 includes merging the overhead stream 14 and the isomerization unit effluent stream 12 to form a combined stream 16. According to an embodiment of the invention, as shown in block 205, method 200 includes separating the combined stream 16 in a second separation unit 104 to form a C3 stream 17 primarily containing C3 hydrocarbons and a second C4 stream 18 primarily containing isobutane. Alternatively, the overhead stream 14 and the isomerization unit effluent stream 12 may flow separately into the second separation unit 104 and then separate to generate the C3 stream 17 and the second C4 stream 18. In an embodiment of the invention, the C3 stream 17 also contains C1 and C2 hydrocarbons. The second C4 stream 18 may contain 97 to 99% by weight of isobutane. The second separation unit 104 may include a distillation column. The distillation column can operate within a top dew point range of 40°C to 55°C, a bottom temperature range of 60°C to 95°C, and an operating pressure range of 17 bar to 19 bar. In an embodiment of the invention, the top feed stream 14 from the separation column and the effluent stream 12 from the isomerization unit in the second separation unit 104 are configured to increase the purity of the isobutane fed into the dehydrogenation unit 105, thereby improving the efficiency of the dehydrogenation unit 105 and the MTBE synthesis unit 106 by reducing the inert portion of the feedstock.

[0041] According to an embodiment of the invention, as shown in block 206, method 200 includes treating the second C4 feed stream 18 in the presence of a dehydrogenation catalyst in a dehydrogenation unit 105 under dehydrogenation conditions sufficient to dehydrogenate the isobutane in the second C4 feed stream 18, to form isobutene in the dehydrogenation unit effluent stream 19. In an embodiment of the invention, the dehydrogenation conditions at block 206 include a temperature of 520°C to 640°C, a pressure of 0.36 bar to 1.2 bar, and a time of 0.2 to 1.2 h. -1 The range of weight hourly space velocity. The dehydrogenation unit effluent stream 19 may contain 35 to 65 wt% isobutylene and all ranges and values ​​therebetween, including the ranges of 35 to 40 wt%, 40 to 45 wt%, 45 to 50 wt%, 50 to 55 wt%, 55 to 60 wt%, and 60 to 65 wt%.

[0042] According to an embodiment of the invention, as shown in block 207, method 200 includes reacting isobutylene from a dehydrogenation unit effluent stream 19 with an alkanol in an etherification unit 106, under reaction conditions sufficient to generate an alkyl tert-butyl ether, in the presence of an etherification catalyst. In embodiments of the invention, non-limiting examples of alkanols include methanol and ethanol. Non-limiting examples of alkyl tert-butyl ethers may include MTBE and ethyl tert-butyl ether. The etherification catalyst may include a cation exchange resin, an ion exchange resin packed with divinylbenzene polystyrene, an ion exchange resin packed with a polymer support, or a combination thereof. The reaction conditions in the etherification unit 106 at block 207 may include an etherification temperature of 40°C to 45°C, an etherification pressure of 5 to 8 bar, and a reaction time of 0.5 to 3.5 h. -1 The liquid hourly space velocity. In an embodiment of the invention, the etherification apparatus 106 is configured to generate a product stream 20 containing 98 to 99.5% by weight of MTBE and a recycled stream 21 containing isobutane.

[0043] According to an embodiment of the invention, as shown in block 208, method 200 includes steam cracking the hydrocarbons of C3 feed stream 17 in a second steam cracking unit 107 under conditions sufficient to generate light olefins and / or aromatics. Non-limiting examples of light olefins generated at block 208 may include propylene and ethylene. Non-limiting examples of aromatics generated at block 208 may include benzene. At block 208, the second steam cracking unit 107 can operate at a temperature of 750°C to 890°C and a residence time of 0.1 seconds to 0.5 seconds.

[0044] In an embodiment of the invention, the cracking of the first C4 stream 15 at frame 203 and / or the unreacted n-butane stream 22, and / or the cracking of the C3 stream 17 at frame 208, is configured to produce propylene and other high-value chemicals, including ethylene and benzene, thereby increasing the overall product value and offsetting the costs of the dehydrogenation unit 105 and the etherification unit 106, thereby improving the efficiency of system 100.

[0045] Although embodiments of the present invention have been referenced Figure 2 The boxes have been described, but it should be understood that the operation of the present invention is not limited to... Figure 2 The specific boxes and / or the specific order of the boxes shown. Therefore, embodiments of the present invention can use different... Figure 2 Various boxes in a specific order are used to provide the functionality described in this article.

[0046] The systems and processes described herein may also include various devices not shown and known to those skilled in the art of chemical processing. For example, some controllers, pipes, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, etc., may not be shown.

[0047] As part of this disclosure, specific embodiments are included below. These embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art will readily recognize that parameters can be changed or modified to produce substantially the same results.

[0048] In the context of this invention, at least 17 embodiments are described below. Embodiment 1 is a method for processing a hydrocarbon mixture. The method includes processing a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit under reaction conditions sufficient to isomerize n-butane to produce isobutane and form an isomerization unit effluent comprising propane, isobutane, or a combination thereof. The method further includes separating the isomerization unit effluent to form a C3 stream containing propane and a C4 stream containing isobutane. The method further includes cracking the propane in the C3 stream under reaction conditions sufficient to produce propylene. The method further includes dehydrogenating the isobutane in the C4 stream in a dehydrogenation unit to produce isobutene in the dehydrogenation unit effluent. Furthermore, the method includes reacting the isobutene in the dehydrogenation unit effluent with an alkanol in the presence of a catalyst in an etherification unit under reaction conditions sufficient to produce alkyl tert-butyl ethers in the product stream.

[0049] Implementation Scheme 2 is a method for processing a hydrocarbon mixture. The method includes processing a first hydrocarbon mixture containing propane, n-butane, and isobutane in an isomerization unit under reaction conditions sufficient to isomerize n-butane to produce isobutane and form an isomerization unit effluent containing propane, isobutane, or a combination thereof. The method further includes separating the second hydrocarbon mixture containing propane, n-butane, and isobutane in a second separation unit to generate an overhead stream generally containing propane and isobutane, and a first C4 stream containing n-butane and isobutane. The method further includes combining the overhead stream and the isomerization unit effluent to form a combined stream, and separating the combined stream to form a C3 stream mainly containing propane and a second C4 stream containing isobutane. The method further includes dehydrogenating isobutane in a dehydrogenation unit to generate isobutene in the dehydrogenation unit effluent, and reacting isobutene in the dehydrogenation unit effluent with an alkanol in the presence of a catalyst in an etherification unit under reaction conditions sufficient to generate alkyl tert-butyl ethers in the product stream. Embodiment 3 is the method according to Embodiment 2, further comprising steam cracking of the C3 stream in a first steam cracking unit. Embodiment 4 is the method according to Embodiment 3, wherein the steam cracking of the second C3 stream is carried out at a temperature of 750°C to 900°C and a steam cracker residence time of 0.1 seconds to 0.5 seconds. Embodiment 5 is the method according to any one of Embodiments 2 to 4, further comprising steam cracking of the first C4 stream in a second steam cracking unit. Embodiment 6 is the method according to any one of Embodiments 2 to 5, wherein the isomerization unit comprises Pt / AlCl3 / Al2O3, Pt / AlCl3 / zeolite, and Pt / SO4. 2- -ZrO2, SO4 2-Isomerization catalysts of ZrO2-Al2O3 or combinations thereof. Embodiment 7 is the method according to any one of Embodiments 2 to 6, wherein the reaction conditions in the isomerization device include an isomerization temperature of 125°C to 175°C. Embodiment 8 is the method according to any one of Embodiments 2 to 7, wherein the reaction conditions in the isomerization device include an isomerization pressure of 20 bar to 30 bar. Embodiment 9 is the method according to any one of Embodiments 2 to 8, wherein the effluent from the isomerization device contains 95 to 99.5% by weight isobutane. Embodiment 10 is the method according to any one of Embodiments 2 to 9, wherein the effluent from the dehydrogenation device contains 35 to 65% by weight isobutene. Embodiment 11 is the method according to any one of Embodiments 2 to 10, wherein the first hydrocarbon mixture and / or the second hydrocarbon mixture contains liquefied petroleum gas. Embodiment 12 is the method according to any one of Embodiments 2 to 11, wherein the first hydrocarbon mixture contains 60 to 80% by weight n-butane and 20 to 30% by weight isobutane. Embodiment 13 is the method according to any one of Embodiments 2 to 12, wherein the etherification unit further generates a recycle stream containing isobutane. Embodiment 14 is the method according to Embodiment 13, further comprising feeding the recycle stream into a dehydrogenation unit. Embodiment 15 is the method according to any one of Embodiments 2 to 14, wherein the dehydrogenation unit comprises a dehydrogenation catalyst containing chromium oxide / alumina, Pt / alumina, or a combination thereof. Embodiment 16 is the method according to any one of Embodiments 2 to 15, wherein the alkanol contains methanol, ethanol, or a combination thereof. Embodiment 17 is the method according to Embodiment 16, wherein the alkyl tert-butyl ether contains MTBE, ETBE, or a combination thereof.

[0050] Although the embodiments and advantages of this application have been described in detail, it should be understood that various changes, substitutions, and modifications can be made therein without departing from the spirit and scope of the embodiments as defined in the appended claims. Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions, tools, methods, and steps described in the specification. Those skilled in the art will readily understand from the foregoing disclosure that processes, machines, manufactures, compositions, means, methods, or steps that are currently existing or have been developed thereafter can be utilized to perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions, tools, methods, or steps within their scope.

Claims

1. A method of processing a hydrocarbon mixture, the method comprising: processing a hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit equipped with a deisobutanizer column configured to separate isobutane and C3 hydrocarbons from unreacted n-butane at reaction conditions sufficient to isomerize at least some of the n-butane to generate isobutane and form an isomerization unit effluent comprising propane, isobutane, or combinations thereof, and an unreacted n-butane stream; separating the isomerization unit effluent to form a C3 stream comprising propane and a C4 stream comprising isobutane; cracking the propane of the C3 stream at reaction conditions sufficient to generate propylene; dehydrogenating the isobutane of the C4 stream in a dehydrogenation unit to generate isobutene in a dehydrogenation unit effluent; and reacting the isobutene of the dehydrogenation unit effluent with an alkanol in the presence of a catalyst in an etherification unit at reaction conditions sufficient to generate alkyl tertiary butyl ether in a product stream.

2. A method of processing a hydrocarbon mixture, the method comprising: processing a first hydrocarbon mixture comprising propane, n-butane, and isobutane in an isomerization unit equipped with a deisobutanizer column configured to separate isobutane and C3 hydrocarbons from unreacted n-butane at reaction conditions sufficient to isomerize the n-butane to generate isobutane and form an isomerization unit effluent comprising propane, isobutane, or combinations thereof, and an unreacted n-butane stream; separating a second hydrocarbon mixture comprising propane, n-butane, and isobutane in a second separation unit to generate an overhead stream comprising primarily propane and isobutane and a first C4 stream comprising n-butane and isobutane; combining the overhead stream and the isomerization unit effluent to form a combined stream; separating the combined stream to form a C3 stream comprising primarily propane and a second C4 stream comprising isobutane; dehydrogenating the isobutane of the second C4 stream in a dehydrogenation unit to generate isobutene in a dehydrogenation unit effluent; and reacting the isobutene of the dehydrogenation unit effluent with an alkanol in the presence of a catalyst in an etherification unit at reaction conditions sufficient to generate alkyl tertiary butyl ether in a product stream. steam cracking the C3 stream in a first steam cracking unit.

4. The method of claim 3, wherein the steam cracking of the C3 stream is conducted at a temperature of 750 °C to 900 °C and a steam cracker residence time of 0.1 seconds to 0.5 seconds.

3. The method of claim 2, further comprising: steam cracking the first C4 stream in a second steam cracking unit.

7. The method of claim 2, wherein the reaction conditions in the isomerization unit comprise an isomerization temperature of 125 °C to 175 °C.

5. The method of claim 2, further comprising:

8. The method of claim 2, wherein the reaction conditions in the isomerization unit comprise an isomerization pressure of 20 bar to 30 bar.

6. The process of claim 2, wherein the isomerization unit comprises an isomerization catalyst comprising Pt / AlCl3 / Al203, Pt / AlCl3 / zeolite, Pt / SO42 2- / ZrO2, SO42 2- / ZrO2-Al203, or combinations thereof.

9. The method of claim 2, wherein the isomerization unit effluent comprises 95 to 99.5 weight % isobutane.

10. The method of claim 2, wherein the dehydrogenation unit effluent comprises 35 to 65 weight % isobutene.

11. The method of claim 2, wherein the first hydrocarbon mixture and / or the second hydrocarbon mixture comprises liquefied petroleum gas. ​ ​ 12. The method of claim 2, wherein the first hydrocarbon mixture comprises 60 to 80 wt% n-butane and 20 to 30 wt% isobutane.

13. The method of claim 2, wherein the etherification unit also produces a recycle stream comprising isobutane.

14. The method of claim 13, further comprising: causing the recycle stream to flow into the dehydrogenation unit.

15. The method of claim 2, wherein the dehydrogenation unit comprises a dehydrogenation catalyst comprising chromium oxide / alumina, Pt / alumina, or a combination thereof.

16. The method of claim 2, wherein the alkanol comprises methanol, ethanol, or a combination thereof.

17. The method of claim 16, wherein the alkyl tert-butyl ether comprises MTBE, ETBE, or a combination thereof.

18. The method of claim 5, wherein the dehydrogenation unit comprises a dehydrogenation catalyst comprising chromium oxide / alumina, Pt / alumina, or a combination thereof.

19. The method of claim 6, wherein the dehydrogenation unit comprises a dehydrogenation catalyst comprising chromium oxide / alumina, Pt / alumina, or a combination thereof.

20. The method of claim 7, wherein the dehydrogenation unit comprises a dehydrogenation catalyst comprising chromium oxide / alumina, Pt / alumina, or a combination thereof.

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