Co-production of high purity isobutane and butene-1 from mixed C4

Abstract

The disclosed systems and methods can be used to produce a high purity isobutane stream and a high purity 1-butene stream from a mixed C4 stream having different starting compositions.

Description

Technical Field

[0001] Embodiments herein relate to methods and systems for the co-production of isobutane and 1-butene. Background Art

[0002] Various methods have been disclosed for producing a high purity isobutylene stream from a mixed C4 stream. Many of these methods include etherification of isobutylene to produce methyl tert-butyl ether (MTBE), which can be separated from the remaining C4 and then back-cracked to form a pure isobutylene stream. Such methods may be disclosed, for example, in US5628880 and US5321163, among others.

[0003] The separation of isobutylene in the form of MTBE allows the separation and recovery of butenes (1-butene and 2-butene). Summary of the invention

[0004] To the best of the inventors' knowledge, there is no prior art process that provides for the co-production of a high purity isobutane stream and a high purity 1-butene stream.

[0005] In one aspect, embodiments herein relate to a method for co-producing high-purity isobutane stream and high-purity 1-butene stream.Methods described may include providing a first mixed C4 stream and a second mixed C4 stream, each of which comprises isobutene, isobutane, 1-butene and 2-butene, and wherein the first mixed C4 stream has an isobutane concentration higher than the second mixed C4 stream.The first mixed C4 stream and the methanol feed as reactant or selector (selectivator) can be fed to the first reaction system to convert the isobutene contained therein into methyl tertiary butyl ether or isobutylene dimer.The second mixed C4 stream and the methanol feed as reactant or selector can be fed to the second reaction system to convert the isobutene contained therein into methyl tertiary butyl ether or isobutylene dimer. Then the method may include separating the effluent from the first reaction system in the first separation system including a water wash system, to reclaim the first light stream, the first methanol+water stream and the first heavy stream comprising methyl tertiary butyl ether or isobutylene dimer comprising 1-butene, 2-butene, isobutane. In addition, the method is included in separating the effluent from the second reaction system in the second separation system including a water wash system, to reclaim the second light stream, the second methanol+water stream and the second heavy stream comprising methyl tertiary butyl ether or isobutylene dimer comprising 1-butene, 2-butene and isobutane. Then the first methanol+water stream and the second methanol+water stream can be fed to a methanol recovery system to separate methanol from water, and at least a portion of the methanol is returned to any one or two in the first reaction system and the second reaction system. The second light stream can be fed to a separation system, to reclaim the stream, 1-butene stream and the first heavy C4 stream comprising normal butane and 2-butene containing isobutane. The isobutane-containing stream and the first lights stream may be fed to a separation system to recover an isobutane stream and a second heavier C4 stream comprising n-butane and 2-butene.

[0006] In another aspect, embodiments disclosed herein relate to a system for co-producing high-purity isobutane and high-purity 1-butene streams. The system includes a first mixed C4 feed stream and a second mixed C4 feed stream, each of which contains isobutene, isobutane, 1-butene and 2-butene. The first mixed C4 stream can have a higher isobutane concentration than the second mixed C4 stream. The system also includes a first methanol feed stream and a second methanol feed stream. The first reaction system is configured to receive the first mixed C4 stream and the first methanol stream and react the first mixed C4 stream with the methanol as a reactant or a selector, thereby converting the isobutene contained therein into methyl tertiary butyl ether or isobutylene dimer. The second reaction system is configured to receive the second mixed C4 stream and the second methanol stream and react the second mixed C4 stream with the methanol as a reactant or a selector, thereby converting the isobutene contained therein into methyl tertiary butyl ether or isobutylene dimer. The system also includes a first separation system (including a water washing system) for separating the effluent from the first reaction system to recover a first light stream containing 1-butene, 2-butene, isobutane, a first methanol + water stream, and a first heavy stream containing methyl tert-butyl ether or isobutylene dimer; and a second separation system (including a water washing system) for separating the effluent from the second reaction system to recover a second light stream containing 1-butene, 2-butene, isobutane, a second methanol + water stream, and a second heavy stream containing methyl tert-butyl ether or isobutylene dimer. A common methanol recovery system and a flow line are provided, the common methanol recovery system is used to receive the first methanol + water stream and the second methanol + water stream to separate methanol from water, and the flow line is used to return at least a portion of the methanol to either or both of the first reaction system and the second reaction system; a first light separation system is used to receive the second light stream and recover a stream containing isobutane, a 1-butene stream, and a first heavy C4 stream containing normal butane and 2-butene. The second lights separation system is configured to receive the first lights stream and to recover an isobutane stream and a second heavy C4 stream comprising normal butane and 2-butene.

[0007] Other aspects and advantages will be apparent from the following description and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a simplified process flow diagram of a system for co-producing isobutane and 1-butene according to an embodiment of the present invention.

[0009] Figure 2 is a simplified process flow diagram of a system for co-producing isobutane and 1-butene according to an embodiment of the present invention.

[0010] Figure 3 is a simplified process flow diagram of a system for co-producing isobutane and 1-butene according to an embodiment of the present invention.

[0011] Figure 4 is a simplified process flow diagram of a system for co-producing isobutane and 1-butene according to an embodiment of the present invention. DETAILED DESCRIPTION

[0012] Embodiments herein relate to methods and systems for the combined production of isobutane and 1-butene. More specifically, embodiments herein relate to producing high purity isobutane and 1-butene streams by mixed C4 streams. Even more specifically, embodiments herein relate to producing high purity 1-butene streams and isobutane streams simultaneously by mixed C4 feedstocks from RFCC / FCC and / or steam cracking unit (SCU).

[0013] A variety of upstream production processes can be used to produce C4 streams, such as fluid catalytic cracking (FCC) units, residual oil sulfidation catalytic cracking units (RFCC), steam crackers, pyrolysis units (thermal cracking with or without steam), and a variety of other methods of producing mixed C4 can be used. The mixed C4 stream produced by these units can include isobutylene, isobutane, 1-butene, 2-butene, normal butane and butadiene and other components.

[0014] While producing similar chemical compounds, these upstream C4 production systems produce streams with different composition mixtures of various C4 compounds. For example, the C4 mixed by FCC or RFCC can have a significantly higher isobutane concentration (for example, >20 weight % or >25 weight %) than the raffinate-1 (for example <5 weight % or <3 weight % isobutane) recovered from the steam cracker butadiene production process. Meanwhile, the isobutene concentration in FCC / RFCC C4 is significantly lower than that of steam cracker C4 (such as <25 or 30 weight % of RFCC, compared to >35 or 40 weight % of steam cracker C4). Similarly, each (FCC / RFCC compared to steam cracker) may have a difference in the concentration of 1-butene (such as less than 20 or 15 weight %, compared to greater than 35 or 40 weight %). In addition, the diene content of the C4 mixed by FCC / RFCC is significantly higher than that of steam cracker raffinate-1 (such as 0.3 weight % or 3,000ppmw, compared to 40ppmw).

[0015] It is expected that the mixed C4 is separated into various product streams, such as isobutane stream and 1-butene stream, and those skilled in the art can simply mix each in various C4 streams to carry out co-processing. However, the inventor has found that, based on the difference in composition between streams, these raw materials should be separately processed in parallel reaction train device (train), and this includes the shared equipment of integrated reaction train device, to produce required high purity isobutane and high purity 1-butene product. Parallel reaction train device is used to provide for reclaiming raffinate-2 stream, mixed C4 stream, wherein effectively remove isobutene from each reaction train device, and allow operator to optimize the equipment size design and related power consumption required for isobutane and 1-butene purification. The raffinate-2 from FCC / RFCC reaction train device will have relatively high isobutane concentration and lower 1-butene concentration. In contrast, the raffinate-2 from steam cracker reaction train device will have significantly higher 1-butene concentration and lower isobutane concentration.

[0016] In two reaction series devices, isobutylene can be removed from a separate raffinate 2 stream by dimerization and / or conversion to methyl tertiary butyl ether in the reaction series device (as used herein, series device 1 = FCC / RFCC C4 conversion, and series device 2 = steam cracker C4 conversion). The reactor configuration in each series device can be specific for the upstream C4 feed provided, customized to meet the needs for converting isobutylene. In addition, it has been found that appropriate integration of product separation can provide a high purity isobutane stream. Even if the steam cracker C4 feed has a relatively low isobutane content, the additional isobutane added to the FCC / RFCC raffinate stream also provides a high purity isobutane product stream.

[0017] When the reaction system produces isooctene (isobutylene dimer), the isooctene produced in the two reaction train units can be combined, purified to remove oxygenates, and then, if necessary, sent to a saturation reactor to convert the isooctene to isooctane. The isobutylene dimer can also be optionally used for alkylation. For example, when the reaction system produces methyl tert-butyl ether (MTBE), the MTBE can be back-cracked to form a high purity isobutylene stream.

[0018] The reactor trains (train 1 and train 2) can each use methanol as a reactant (to produce MTBE) or as a selector (for selective dimerization). The raffinate stream from each reactor train can be independently water washed to remove methanol. The resulting water / methanol stream can then be fed to a common methanol recovery system to provide methanol recycle and wash water recycle.

[0019] As noted above, the configuration of the reactor series device can be designed to provide efficiency based on the C4 supply to the individual series device. For example, a reactor series device with a higher initial isobutylene concentration can be processed in a fixed bed reactor or a series of fixed bed reactors, and an intermediate separation stage can be included to remove a portion of the product (MTBE or dimer), thereby providing additional driving force for the continuous conversion in the downstream reactor. When the initial concentration of isobutylene is low, intermediate separation can be used or not. In some embodiments, the upstream reactor effluent can be fed to a finishing reactor (which can be a catalytic distillation reactor) to provide the simultaneous reaction of any remaining isobutylene and the separation of dimer / MTBE product and remaining C4 components (including normal butane, isobutane, 1-butene and 2-butene). The catalyst in the catalytic distillation reactor can also have the function of selectively hydrogenating any butadiene present, thereby forming additional butenes.

[0020] Reference now Figure 1 , shows a simplified process flow diagram of a system for the joint production of isobutane and 1-butene according to an embodiment of the present invention. A mixed C4 stream 10 (such as an FCC or RFCC C4 stream) with a relatively high isobutane concentration can be fed to a first reaction series device 12. The reaction series device 12 can be used to convert the isobutene contained therein into MTBE or isobutene dimers (isooctenes), which include methanol 13 fed as a reactant or selector. The reaction series device 12 including an internal separation (not shown) can produce a raffinate-2 stream 14 with low or no residual isobutene and a heavy material (MTBE and / or isooctene) stream 16.

[0021] Similarly, a mixed C4 stream 20 (such as a steam cracker C4 stream) having a relatively low isobutane concentration can be fed to a second reaction train unit 22. The reaction train unit 22 can be used to convert the isobutylene contained therein into MTBE or isobutylene dimers (isooctenes), including methanol 23 fed as a reactant or selector. The reaction train unit 22, including internal separation (not shown), can produce a raffinate-2 stream 24 with low or no residual isobutylene and a heavies (MTBE and / or isooctene) stream 26.

[0022] The heavy streams 16, 26 containing MTBE or isooctene, respectively, may be combined to form a converted isobutylene product stream 28. The dimer or ether may be further processed (not shown), such as via hydrogenation or back cracking, among other possible means, to produce the desired product. Stream 28 may also include heavy oxygenate byproducts.

[0023] The raffinate-2 stream 14 (from the first reactor train device 12) can include various C4 components, such as isobutane, 1-butene, 2-butene and normal butane, and can be isobutene-depleted or lacking. The raffinate-2 stream 14 can also include methanol and / or other oxygenate byproducts, such as dimethyl ether. The raffinate-2 stream 14 can then be fed to a water scrubber 30 to extract methanol, thereby producing a water / methanol stream 32 and a mixed C4 stream 34.

[0024] The raffinate-2 stream 24 (from the second reactor train device 22) can include various C4 components, such as isobutane, 1-butene, 2-butene, butadiene and n-butane, and can be isobutene-depleted or lacking. The raffinate-2 stream 24 can also include methanol and / or other oxygen-containing compound byproducts, such as dimethyl ether. The raffinate-2 stream 24 can then be fed to a water scrubber 40 to extract methanol, thereby producing a water / methanol stream 42 and a mixed C4 stream 44.

[0025] The water / methanol stream 42, 32 can then be fed to a common methanol recovery system 50 to separate the methanol from the water. The recovered water (not shown) can be fed back to the water wash system 30, 40, and the recovered methanol can be fed as the methanol stream 13, 23 as a reactant or selector in the reaction train unit 12, 22. Fresh methanol (not shown) can also be supplied within the methanol recovery system 50 or directly to the reactor at the desired location within the reaction train unit 12, 22.

[0026] Mixed C4 stream 44 (having relatively high concentration of 1-butene) can be fed to separation system to reclaim high purity 1-butene stream.1-Butene recovery system can include heavies tower 60, thereby 1-butene is separated from the normal butane and 2-butene present.In some embodiments, reaction zone (upstream or within heavies tower 60, not shown) can be set to isomerize 2-butene to 1-butene.Heavies tower 60 can produce heavy C4 stream 62 (comprising normal butane and 2-butene) and overhead product stream 64 (containing isobutane and 1-butene). Overhead product stream 64 may then be fed to 1-butene lights column 70 where isobutane and any dimethyl ether present may be recovered as overhead product 72 and 1-butene may be recovered as bottoms product 74, which may be a high purity 1-butene stream, such as having a 1-butene concentration greater than 90 wt%, 95 wt%, 98 wt%, or 99 wt%.

[0027] The overhead product stream 72 containing isobutane from the reaction train device 2 and the mixed C4 stream 34 with relatively high isobutane concentration can be fed to a separation system to reclaim a high purity isobutane stream, such as having an isobutane concentration greater than 90 wt %, 95 wt %, 98 wt % or 99 wt %. The isobutane recovery system can include a deisobutanizer 80, thereby separating isobutane from the normal butane and 2-butene present. In some embodiments, a reaction zone (upstream or within the deisobutanizer 80, not shown) can be set to isomerize any 1-butene present to 2-butene. The deisobutanizer 80 can produce a heavy C4 stream 82 (comprising normal butane and 2-butene) and an overhead product stream 84 (containing isobutane). The overhead product stream 84 can then be fed to a DME lights tower 90, where isobutane can be separated from any dimethyl ether present. The lights / DME may be recovered as an overhead product 92, and isobutane may be recovered as a bottoms product 94, which may be a high purity isobutane stream.

[0028] If desired, the heavy C4 streams 62, 82 (comprising n-butane and 2-butene) can be combined into a heavy C4 product stream 95 for further processing or recovery. For example, n-butane and 2-butene can be separated to provide a high purity 2-butene stream.

[0029] In some embodiments, the initial separation of isobutylene may be via dimerization or via etherification, as described above. Figure 2 and Figure 3 A simplified process flow diagram of a system in which isobutylene is separated via dimerization is shown. Although both systems achieve similar end results and may include similar reactors, due to the different feed compositions, each series of units may be optimized for a specific feed composition or expected composition range.

[0030] Reference now Figure 2 , a simplified process flow diagram of reaction train unit 1 (high isobutane content) is shown. A mixed C4 stream 10 and methanol 13 can be fed to dimerization reactors 101, 103, each containing a selective dimerization catalyst for converting isobutylene into isobutylene dimers. The effluent 104 from the first dimerization reactor 101 can be fed to the second dimerization reactor 103 for additional conversion of isobutylene. The effluent 106 from the second dimerization reactor can then be fed to a catalytic distillation column 108 for additional conversion of isobutylene, while separating the unreacted lighter C4 components from the desired dimers and any heavy oxygenated compound by-products. Additional methanol 109 can be added to the catalytic distillation column 108 as needed. The lighter C4 components can be recovered as an overhead fraction 110, while dimers and heavy by-products can be recovered as a bottoms fraction 112.

[0031] The overhead product fraction 110 may include isobutane, 1-butene, 2-butene and methanol and other components. The overhead product fraction 110 may then be fed to a water scrubber 120 to separate methanol from C4 hydrocarbons. Wash water 121 may be fed toward the top of the water scrubber 120 and contact the C4 hydrocarbons in a countercurrent manner to remove methanol. The C4 hydrocarbons may be recovered from the water scrubber 120 as an overhead product fraction 122, and a methanol / water mixture may be recovered as a bottom product fraction 124.

[0032] Reference now Figure 3 , a simplified process flow diagram of reaction train unit 2 (high isobutylene content) is shown. A mixed C4 stream 20 and methanol 23 may be fed to a first dimerization reactor 201, which contains a selective dimerization catalyst for converting isobutylene into isobutylene dimers. The effluent 202 from the first dimerization reactor 201 may be fed to a debutanizer 204 to separate dimers 206 from unreacted C4 components 208, which are more depleted in isobutylene than the C4-based feed stream 20.

[0033] The overhead fraction 208 (unreacted C4) can then be fed to a second dimerization reactor 210 for additional conversion of isobutylene. The effluent 212 from the second dimerization reactor can then be fed to a catalytic distillation column 216 for additional conversion of isobutylene while separating the unreacted lighter C4 components from the desired dimers and any heavy oxygenate byproducts. Additional methanol 218 can be added to the catalytic distillation column 108 as needed. The lighter C4 components can be recovered as an overhead fraction 220, while the dimers and heavy byproducts can be recovered as a bottoms fraction 222.

[0034] The overhead product fraction 220 may include isobutane, 1-butene, 2-butene and methanol and other components. The overhead product fraction 220 may then be fed to a water scrubber 230 to separate methanol from C4 hydrocarbons. Wash water 232 may be fed toward the top of the water scrubber 230 and contact the C4 hydrocarbons in a countercurrent manner to remove methanol. The C4 hydrocarbons may be recovered from the water scrubber 230 as an overhead product fraction 234 and a methanol / water mixture may be recovered as a bottom product fraction 236.

[0035] The methanol / water stream 124 ( Figure 2 ) and 236 are combined and fed to a common methanol recovery system 250. The methanol recovery system 250 may include distillation separation and / or membrane separation to separate water from methanol. As shown, the distillation of the water / methanol mixture may produce a bottom product water stream 260 and an overhead product methanol stream 262. The water in the bottom product water stream 260 may be returned to the water wash tower 230, 120 ( via streams 232, 121). Figure 2), and the methanol in stream 262 can be fed to each reactor (201, 210, 216, 101, 103, 108) as needed, such as via streams 13 and 23.

[0036] In some embodiments, the heavy stream (208, 222, 124 ( Figure 2 In some embodiments, the heavy streams may be combined and separated in a distillation column 280 to recover a dimer fraction 282 and a heavy oxygenate fraction 284, each of which may be further processed and / or used for fuel blending (e.g., in gasoline, diesel, etc.).

[0037] After isobutylene is removed via reaction and a separate raffinate-2 stream is produced in a separate reactor train unit, the mixed C4s can then be separated to produce the desired isobutane and 1-butene product streams. Figure 4 An integrated isobutane and 1-butene purification zone is shown according to some embodiments herein.

[0038] The mixed C4 stream 234 with relatively high 1-butene concentration can be fed to a separation system to reclaim a high-purity 1-butene stream. The 1-butene recovery system can include a heavies tower 300, thereby separating 1-butene from the normal butane and 2-butene present. The heavies tower 300 can produce a heavy C4 stream 302 (comprising normal butane and 2-butene) and an overhead product stream 304 (containing isobutane and 1-butene). The overhead product stream 304 can then be fed to a 1-butene lights tower 310, where isobutane and any dimethyl ether present can be recovered as an overhead product 312, and 1-butene can be recovered as a bottoms product 314, which can be a high-purity 1-butene stream.

[0039] The overhead product stream 312 containing isobutane from the reaction train unit 2 and the mixed C4 stream 122 with a relatively high isobutane concentration can be fed to a separation system to recover a high purity isobutane stream. The isobutane recovery system can include a deisobutanizer 330, thereby separating isobutane from the normal butane and 2-butene present. The deisobutanizer 330 can produce a heavy C4 stream 332 (comprising normal butane and 2-butene) and an overhead product stream 334 (comprising isobutane). The overhead product stream 334 can then be fed to a DME light substance tower 340, where isobutane can be separated from any dimethyl ether present. Light substances / DME can be recovered as an overhead product 342, and isobutane can be recovered as a bottom product 344, which can be a high purity isobutane stream. The heavy C4 streams 302, 332 (comprising normal butane and 2-butene) can be combined into a heavy C4 product stream 350.

[0040] As described above, embodiments herein may be used to efficiently produce isobutane and 1-butene products from various mixed C4 feed streams having different compositions.

[0041] In some embodiments, the charging of each reaction series device can be through pretreatment.As will be described below, the first reaction series device can be used for processing the C4 stream of high isobutane content, and the second reaction series device can be used for processing the C4 stream of low isobutane content, and some of these shared systems integrate these two reaction series devices.As described below, the stream of high isobutane content (such as FCC or RFCC C4 stream) will be fed to series device 1, and as described below, the stream of low isobutane content (such as steam cracker C4 stream) will be fed to series device 2.

[0042] Series 1 Feed pretreatment

[0043] FCC / RFCC C4 can be fed pre-treated in the first pre-treatment system. The unsaturated mixed C4 feed from an upstream unit (such as an LPG unit) can be filtered and then washed in a water scrubber with a countercurrent flow of softened wash water under flow control to remove most of the water-soluble impurities, such as nitriles. The top of the water scrubber can be equipped with a mesh pad to coalesce and remove any unseparated water. The used wash water from the bottom product can be transported to the refinery wastewater system for treatment.

[0044] The washed mixed C4 can then be taken from the top of the wash water tower and delivered to the Series 1 C4 feed surge drum under pressure control. The surge drum can also be equipped with a coalescer and a water boot to remove any remaining traces of free water. In the event that a small amount of non-condensable vapor accumulates in the surge drum, a pressure discharge system with associated nitrogen purge can be set up to dilute these vapors and discharge them to the flare. The washed C4 feed can then be pumped out of the surge drum and delivered to the Series 1 primary reactor.

[0045] Series 2 Feed Pretreatment

[0046] Steam cracker C4 or C4 (such as raffinate-1C4 raw material) from upstream butadiene device can also be subjected to feed pretreatment.Unsaturated raffinate-1C4 raw material from upstream BD device can be filtered, then washed in water scrubber under flow control using the countercurrent flow of softening washing water to remove most of water-soluble impurities, such as nitriles.The top of water scrubber can be equipped with mesh pad to coalesce and remove any unseparated water.The used washing water from tower bottoms product can be transported to wastewater system for further treatment.

[0047] The washed mixed C4 can be taken from the top of the wash water tower and delivered to the Series 2 C4 feed buffer tank under pressure control. The buffer tank can also be equipped with a coalescer and a waterproof cover to remove any remaining traces of free water. In the event that a small amount of non-condensable vapor accumulates in the buffer tank, a pressure discharge system with an associated nitrogen purge can be set up to dilute these vapors and discharge them to the flare. The washed C4 feedstock can then be pumped out of the buffer tank and delivered to the Series 2 primary reactor.

[0048] FCC / RFCC reaction system

[0049] In some embodiments, the FCC / RFCC reaction system includes a reactor for selectively converting isobutylene to methyl tert-butyl ether via a reaction with methanol. In other embodiments, the FCC / RFCC reaction system includes a reactor for selectively dimerizing isobutylene to form isooctene, in which an oxygen-containing compound (such as methanol) can be used as a selector.

[0050] For example, the treated mixed C4 olefin feed from the train unit 1 C4 feed buffer tank can be mixed with recycled oxygenates and fresh and recycled methanol (selective agent) and fed to a dimerization reactor, such as a primary tempered water-cooled tubular reactor (WCTR). The mixed feed stream can be preheated by a low pressure (LP) steam preheater. The process fluid then passes through the catalyst-filled tube side of the WCTR.

[0051] The dimerization of isobutylene to isooctene occurs at relatively low temperatures in the primary DIB (di-isobutylene) WCTR. The heat of reaction can be removed by a closed loop tempering water system provided for the shell side of the WCTR.

[0052] Series 1 Debutanizer

[0053] The effluent from the primary WCTR can then be fed to a debutanizer under pressure control. The effluent can be heated via a debutanizer feed / bottoms exchanger before entering the debutanizer.

[0054] The overhead vapor (mainly C4 and methanol) from the debutanizer is cooled, condensed, and the condensate is collected in the debutanizer overhead tank. The distillate from the overhead tank is pumped out of the tank under liquid level control. A portion of the distillate is returned to the debutanizer as reflux, and the net distillate stream can be preheated via the LP steam preheater and then sent to the secondary WCTR reactor.

[0055] The debutanizer bottoms stream is cooled via a debutanizer feed / bottoms exchanger and then passed to a splitter column discussed further below.

[0056] Series 1 Secondary DIB (Di-Isobutylene) Reactor

[0057] The distillate stream from the debutanizer is combined with recycled oxygenates, cooled via a feed cooler, and fed to the inlet of a secondary water-cooled tubular reactor (WCTR) to enable further conversion of isobutylene to isooctene and other C8 olefins. Isobutylene dimerization occurs again under low temperature conditions in the secondary WCTR. The heat of reaction is also removed by circulating water through the shell side of the reactor using a tempering water system.

[0058] Series device 1CD reaction tower

[0059] The effluent from the secondary WCTR flows to the CD reaction tower via the CD reaction tower feed / bottom product exchanger. The CD reaction tower is operated in a similar manner to a conventional distillation tower and is equipped with an external reboiler and an overhead condenser. The CD reaction tower also contains trays above and below the feed inlet nozzle. The CD module (a structured catalyst support containing a catalyst) is also located in the bed above the feed nozzle. The CD module facilitates both reaction and simultaneous distillation, and separates the reaction products and heavier hydrocarbons (C8+) from unreacted C4 hydrocarbons as well as MTBE and other oxygenates.

[0060] Along with other C4 hydrocarbons, unreacted isobutylene is distilled upward from the feed point through the CD reaction column to the reaction zone within the CD module to convert isobutylene. Unreacted C4 hydrocarbons, as well as excess methanol and light impurities in the feed, leave the column as overhead.

[0061] The distillate is cooled, condensed, and the condensate is collected in the CD reaction tower overhead tank. The distillate from the overhead tank is pumped out of the tank under liquid level control. A portion of the distillate is returned to the CD reaction tower as reflux, and then the net distillate stream is cooled and sent to the series unit 1 methanol extraction tower to separate excess methanol.

[0062] Isooctenes (DIB), C8 olefins, and other heavier hydrocarbons leave the CD reactor as a bottoms product along with oxygenates. The bottoms are cooled via a CD reactor feed / bottoms exchanger and then sent to a DIB / MTBE splitter for separation and recovery of oxygenates for use as a selector in the main reactor section. Any oxygenates purged from the top of the DIB / MTBE splitter are sent to the OSBL for blending into the motor gasoline (Mogas) pool.

[0063] Reactor series unit 2

[0064] In some embodiments, the steam cracker C4 reaction system includes a reactor for selectively converting isobutylene to methyl tert-butyl ether via reaction with methanol. In other embodiments, the FCC / RFCC reaction system includes a reactor for selective dimerization of isobutylene to form isooctene, in which an oxygenate (such as methanol) can be used as a selector.

[0065] When dimers are produced, Series 2 may include a primary DIB (di-isobutylene) reactor. The treated mixed C4 olefin feed (raffinate-1) from the Series 2 C4 feed buffer tank may be mixed with recycled oxygenates and fresh and recycled methanol (selector). The mixed feed stream may be preheated by a LP steam preheater before entering the primary tempered water-cooled tubular reactor (WCTR). The process fluid then passes through the catalyst-filled tube side of the WCTR.

[0066] Isobutylene dimerization to isooctene occurs at relatively low temperature in the primary DIB (di-isobutylene) WCTR. The heat of reaction is removed by a closed loop tempering water system provided for the shell side of the WCTR.

[0067] Series 2 Debutanizer

[0068] The effluent from the Train 2 Primary WCTR is then fed to the Train 2 debutanizer under pressure control. The effluent is heated via a debutanizer feed / bottoms exchanger before entering the debutanizer.

[0069] The overhead vapor (mainly C4 and methanol) from the debutanizer is cooled, condensed, and the condensate is collected in the debutanizer overhead tank. The distillate from the overhead tank is pumped out from the tank under liquid level control. A portion of the distillate is returned to the debutanizer as reflux, and the net distillate stream is preheated via the LP steam preheater and then transported to the series unit 2 secondary WCTR reactor. The series unit 2 debutanizer bottoms stream can be cooled via the debutanizer feed / bottoms exchanger and then transported to the MTBE / DIB splitter under flow control.

[0070] Series 2 Secondary DIB (Di-Isobutylene) Reactor

[0071] The distillate stream from the train 2 debutanizer is combined with recycled oxygenates and fed to the inlet of the train 2 secondary water-cooled tubular reactor (WCTR) to enable further conversion of isobutylene to isooctene and other C8 olefins. Isobutylene dimerization occurs in the secondary WCTR again under low temperature conditions.

[0072] Series 2 MTBE CD reaction tower (including CDHydro function)

[0073] The effluent from the secondary WCTR flows to the series unit 2 CD reaction tower via a CD reaction tower feed / bottom product exchanger. The CD reaction tower operates in a similar manner to a conventional distillation tower and is equipped with an external reboiler and an overhead condenser. The CD reaction tower also contains trays above and below the feed inlet nozzle. The CD module (structured catalyst support containing the catalyst) is also located in the bed above the feed nozzle.

[0074] The CD module in the Series 2 CD reactor can facilitate reactions (selective hydrogenation and isobutylene dimerization) and simultaneous distillation, and separate the reaction products and heavier hydrocarbons (C8+) from unreacted C4 hydrocarbons as well as MTBE and other oxygenates.

[0075] For Series 2, the CD reactor is equipped with two types of CD modules. The first type of CD module provides a catalyst for supporting the continued dimerization of isobutylene to C8. The second type of CD module provides a catalyst for the selective hydrogenation of butadiene. These CD modules provide the unique CDHydro functionality. Hydrogenation also requires the injection of a small amount of fresh hydrogen into the CD reactor.

[0076] Three types of chemical reactions occur in the CDHydro section: hydrogenation of butadiene to n-butenes, hydroisomerization of n-butenes between 1-butene and 2-butene, and olefin saturation. Olefin saturation can be minimized using highly selective catalysts and by the high reactivity of butadiene relative to olefins.

[0077] The selective hydrogenation is an exothermic process and therefore causes a temperature increase throughout the reactor. The heat of reaction is absorbed by the CD column reflux as it passes downward through the CD module.

[0078] Together with other C4 hydrocarbons, unreacted isobutylene and butadiene are distilled upward from the tower feed point through the CD reaction tower to the reaction zone within the CD module for isobutylene conversion and diene saturation. Unreacted C4 hydrocarbons as well as excess methanol and light impurities in the feed are recovered from the tower as overhead distillate.

[0079] The distillate is cooled, condensed, and the condensate is collected in the overhead tank of the series unit 2CD reaction tower. The distillate from the overhead tank is pumped out of the tank under liquid level control. A portion of the distillate is returned to the CD reaction tower as reflux, and then the net distillate stream is cooled and sent to the methanol extraction tower for separation of excess methanol. Non-condensables are discharged from the overhead tank regularly using a remote HC valve.

[0080] Isooctenes (DIB, dimer 8), C8 olefins, and other heavier hydrocarbons leave the CD reactor as a bottom product along with oxygenates. The bottom product can be cooled via a CD reactor feed / bottom product exchanger and then sent to a DIB / MTBE splitter for separation and recovery of oxygenates used as a selector in the primary reactor section. A portion of the oxygenates purged from the top of the DIB / MTBE splitter can be sent for blending in the Mogas pool.

[0081] Dimer 8 shared methanol recovery section (reaction series units 1 and 2)

[0082] As described above, the C8 distillate streams (containing a mixture of C4 hydrocarbons and methanol) from the CD reaction towers in the series 1 and 2 are first treated independently in the series 1 and 2 methanol extraction towers. Methanol can be washed from each C8 distillate stream using a countercurrent demineralized water stream. Each methanol extraction tower can be equipped with a mesh pad at the top of the tower to prevent water from being brought in. The washed C8 hydrocarbons are taken out from the top of each of the series 1 and 2 towers to provide a separate raffinate-2 stream.

[0083] The washed raffinate-2 from the methanol extraction column of the train unit 1 is then fed to the isobutane purification section. The washed raffinate-2 from the methanol extraction column of the train unit 2 is then fed to the 1-butene recovery and purification section.

[0084] Then the aqueous extract (bottom product) stream from the methanol extraction tower of series device 1 and series device 2 is combined and transported to the common methanol recovery tower for separating methanol and water by distillation. The overhead vapor from the common methanol recovery tower is cooled, condensed, and the condensate is collected in the methanol recovery tower overhead tank. The distillate from the overhead tank is pumped out from the tank under liquid level control. A part of the distillate is returned to the methanol separation tower as reflux, and the net distillate stream (purified methanol) is recycled back to the reaction series device 1 and series device 2 primary and secondary reactors and CD reaction tower. Fresh additional methanol can also be added in the overhead tank. The washing water from the methanol recovery tower bottom product is recycled back to the methanol extraction tower of series device 1 and series device 2 to reuse.

[0085] Shared Dimer 8DIB / Oxygenate Splitter

[0086] The bottoms streams from the dimer 8 reaction train unit 1 and train unit 2 debutanizer and CD reaction tower may contain oxygenates such as TBA, MTBE, MSBE and C9 ethers, which are removed in the DIB / oxygenate splitter. These bottoms streams from train unit 1 and train unit 2 are combined and fed to a single DIB / oxygenate tower.

[0087] In the DIB / oxygenate column, most of the lighter oxygenates (MTBE, MSBE and TBA) are distilled upward in the vapor phase and then condensed at the top of the column. The overhead vapor is water-cooled and condensed in the splitter condenser, and the condensate is collected in the oxygenate / DIB splitter column overhead tank.

[0088] The distillate from the overhead tank is pumped out and a portion of the distillate is returned as reflux to the MTBE / DIB splitter. Most of the oxygenate exhaust from the tower is pumped back and blended with the unit feed to be used as a selector in the primary and secondary reactors of the dimer 8 reaction series unit 1 and series unit 2. A smaller portion of the distillate product is transported as an oxygenate exhaust for blending in the Mogas pool. The splitter bottoms stream consists of isooctene (DIB), other C8 olefins, C12, C16 and C9 ethers. The bottoms stream is then transported to the C8 saturation section to provide an isooctane product.

[0089] Shared isooctene saturation

[0090] If desired, the isooctene recovered from the splitter column bottoms stream may be hydrogenated to form isooctane.

[0091] Isobutane purification (raffinate from series 1 - 2)

[0092] The raffinate-2 stream from reaction train unit 1 is combined with the overhead product from the B1 lights column (see process description below for 1-butene separation unit) and sent to the isobutane purification section.

[0093] The combined raffinate-2 feedstock is first fed to a deisobutanizer. The deisobutanizer is used to remove isobutane and light hydrocarbons from the remaining C4 in raffinate 2. The net condensate stream from the deisobutanizer is then fed to a DME lights column. The bottoms stream from the DME lights column is recovered as a bottoms product, which may contain 2-butene and n-butane.

[0094] DME Lightweight Tower

[0095] The net overhead product stream from the deisobutanizer is then fed to the DME lights column. The DME lights column is used to remove light oxygenates (such as DME) and other light hydrocarbons from the high purity isobutane product. The deisobutanizer overhead product stream can be preheated via a DME lights column feed / effluent exchanger and then fed to the DME lights column.

[0096] The overhead vapor from the DME light column is cooled, condensed, and the condensate is collected in the DME light column overhead tank. A portion of the distillate is returned to the DME light column as reflux, and the net distillate stream (DME and other light hydrocarbons) is recovered as a DME light product.

[0097] The bottom product stream from the DME lights column is cooled via a DME lights column feed / effluent exchanger, further cooled via an isobutane product cooler, and then delivered to the battery limit as a high purity isobutane product. In some embodiments, the recovered isobutane stream may have a purity of at least 99% by weight. In other embodiments, the recovered isobutane stream may have a purity greater than 99.2% by weight, greater than 99.3% by weight, greater than 99.4% by weight, or even greater than 99.5% by weight.

[0098] 1-Butene separation (raffinate-2 from series 2)

[0099] The raffinate-2 from reaction train unit 2 is fed to the combined B1 heavies column and B1 lights column to separate and purify the butene-1 product from the remaining raffinate-2 feed. The raffinate-2 from dimer 8 reaction train unit 1 is first fed to the B1 heavies column.

[0100] The compressed overhead product stream from the B1 heavies column is partially condensed via a reboiler for the B1 heavies column, and the condensate is then cooled and collected in the B1 heavies column reflux drum. The condensate from the reflux drum is pumped out, and a portion of the condensate is returned to the B1 heavies column as reflux. The net condensate stream is then fed to the B1 lights column.

[0101] The bottoms stream from the B1 heavies column is pumped to the plant boundary and provides a raffinate-3 product.

[0102] Lightweight tower section

[0103] The net condensate stream from the B1 heavies column reflux drum is pumped out to the B1 lights column section for further separation and purification of 1-butene. The compressed overhead product stream from the B1 lights column is partially condensed via a reboiler for the B1 lights column, and the condensate is then water-cooled and collected in the B1 lights column reflux drum. The condensate from the reflux drum is pumped out, and a portion of the condensate is returned to the B1 lights column as reflux. The net (isobutane-rich) condensate stream is then combined with the raffinate 2 from the series unit 1 and processed in the isobutane purification section as described above.

[0104] The bottom product stream from the B1 lights column is a high purity butene-1 product. In some embodiments, the 1-butene stream recovered can have a purity of at least 99% by weight. In other embodiments, the 1-butene stream recovered can have a purity greater than 99.2% by weight, greater than 99.3% by weight, greater than 99.4% by weight, or even greater than 99.5% by weight.

[0105] As described above, the embodiments herein can provide efficient co-production of both high purity 1-butene and high purity isobutane. The composition of the initially mixed C4 stream is advantageously utilized, with partial shared processing being utilized in advantageous cases, to produce high purity products. Maintaining the reaction train device and water wash as separate systems enables the production of high quality and high purity isobutane and 1-butene streams.

[0106] While the present disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the appended claims.

Claims

1. A method for co-producing a high purity isobutane stream and a high purity 1-butene stream, the method comprising: providing a first mixed C4 stream and a second mixed C4 stream, each comprising isobutylene, isobutane, 1-butene, and 2-butene, and wherein the first mixed C4 stream has a higher isobutane concentration than the second mixed C4 stream; Feeding the first mixed C4 stream and methanol as a reactant or selector into a first reaction system to convert the isobutylene contained therein into methyl tert-butyl ether or isobutylene dimer; Feeding the second mixed C4 stream and methanol as a reactant or selector to a second reaction system to convert the isobutylene contained therein into methyl tert-butyl ether or isobutylene dimer; Separating the effluent from the first reaction system in a first separation system including a water wash system to recover a first light stream comprising 1-butene, 2-butene, isobutane, a first methanol+water stream, and a first heavy stream comprising the methyl tert-butyl ether or the isobutylene dimer; separating the effluent from the second reaction system in a second separation system including a water wash system to recover a second light stream comprising 1-butene, 2-butene and isobutane, a second methanol+water stream, and a second heavy stream comprising the methyl tert-butyl ether or the isobutylene dimer; feeding the first methanol+water stream and the second methanol+water stream to a methanol recovery system to separate methanol from the water, and returning at least a portion of the methanol to either or both of the first reaction system and the second reaction system; feeding the second light stream to a separation system to recover an isobutane-containing stream, a 1-butene stream, and a first heavy C4 stream comprising normal butane and 2-butene; feeding the isobutane-containing stream and the first light stream to a separation system to recover an isobutane stream and a second heavy C4 stream comprising normal butane and 2-butene; wherein the method further comprises feeding a hydrocarbon stream to a steam cracking process and recovering the second mixed C4 stream, wherein the second mixed C4 stream has an isobutane concentration of less than 5 wt%; wherein the first mixed C4 stream has an isobutylene concentration of less than 25 wt %, and wherein the second mixed C4 stream has an isobutylene concentration of at least 30 wt %.

2. The method of claim 1, further comprising separating dimethyl ether from the isobutane stream.

3. The process of claim 1, wherein the isobutane stream has a purity of at least 99 wt% and wherein the 1-butene stream has a purity of at least 99 wt%.

4. The method of claim 1, further comprising feeding a hydrocarbon stream to a fluid catalytic cracking process or a residue fluid catalytic cracking process and recovering the first mixed C4 stream, wherein the first mixed C4 stream has an isobutane concentration of at least 20 wt%.

5. A system for co-producing a high purity isobutane stream and a high purity 1-butene stream, the system comprising: a first mixed C4 stream and a second mixed C4 stream, each comprising isobutylene, isobutane, 1-butene, and 2-butene, and wherein the first mixed C4 stream has a higher isobutane concentration than the second mixed C4 stream; a first methanol stream and a second methanol stream; a first reaction system configured to receive the first mixed C4 stream and the first methanol stream and react the first mixed C4 stream with methanol as a reactant or a selector, thereby converting the isobutylene contained therein into methyl tert-butyl ether or isobutylene dimer; a second reaction system configured to receive the second mixed C4 stream and the second methanol stream and react the second mixed C4 stream with methanol as a reactant or a selector, thereby converting the isobutylene contained therein into methyl tert-butyl ether or isobutylene dimer; A first separation system comprising a water wash system for separating the effluent from the first reaction system to recover a first light stream comprising 1-butene, 2-butene, isobutane, a first methanol+water stream, and a first heavy stream comprising the methyl tert-butyl ether or the isobutylene dimer; a second separation system comprising a water wash system for separating the effluent from the second reaction system to recover a second light stream comprising 1-butene, 2-butene, isobutane, a second methanol+water stream, and a second heavy stream comprising the methyl tert-butyl ether or the isobutylene dimer; a common methanol recovery system and a flow line, the common methanol recovery system being used to receive the first methanol+water stream and the second methanol+water stream to separate methanol from the water, the flow line being used to return at least a portion of the methanol to either or both of the first reaction system and the second reaction system; a first lights separation system for receiving the second lights stream and recovering an isobutane-containing stream, a 1-butene stream, and a first heavy C4 stream comprising normal butane and 2-butene; a second lights separation system for receiving the first lights stream and for recovering an isobutane stream and a second heavy C4 stream comprising normal butane and 2-butene; wherein the system is further configured to feed a hydrocarbon stream to a steam cracking process and recover the second mixed C4 stream, wherein the second mixed C4 stream has an isobutane concentration of less than 5 wt%; wherein the first mixed C4 stream has an isobutylene concentration of less than 25 wt %, and wherein the second mixed C4 stream has an isobutylene concentration of at least 30 wt %.

6. The system of claim 5, further comprising a first mixer for mixing the first heavy C4 stream and the second heavy C4 stream, and a second mixer for mixing the first heavy stream and the second heavy stream.

7. The system of claim 5, wherein each of the first reaction system and the second reaction system is configured to produce isobutylene dimer.

8. The system of claim 5, wherein each of the first reaction system and the second reaction system is configured to produce methyl tert-butyl ether.

9. The system of claim 5, wherein the first reaction system comprises one fixed bed reactor or two or more fixed bed reactors connected in series or in parallel, followed by a catalytic distillation reactor.

10. The system of claim 5, wherein the second reaction system comprises one fixed bed reactor or two or more fixed bed reactors connected in series or in parallel, followed by a catalytic distillation reactor.

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