System and process for producing methyl tert-butyl ether and maleic anhydride from C4 hydrocarbons

Abstract

A system and method for producing MTBE, maleic anhydride, n-butane, and / or olefins is disclosed. The system comprises a feed preparation unit, a deisobutanizer, an isobutane dehydrogenation unit, a steam cracker, a hydrogenation unit, and any one or both of an MTBE synthesis unit or a maleic anhydride unit.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] none Background of the Invention

[0004] A. Technical field of the present invention

[0005] The present invention generally relates to systems and methods for producing C4 hydrocarbon products, and methyl tert-butyl ether (MTBE) and maleic anhydride (MA) produced therefrom. The present invention describes the development of a process scheme for producing MTBE and MA from a C4 hydrocarbon stream containing C3 hydrocarbons, isobutane (iC4), normal butane (referred to herein as normal butane or nC4), and C5 or higher hydrocarbons (C5+), the C4 hydrocarbon stream typically being derived from a stream containing 2 to 5 wt.% C3 hydrocarbons, 25 to 35 wt.% isobutane, 65 to 75 wt.% normal butane, and 1 wt.% to 2 wt.% C5+ hydrocarbons. This is achieved by separating the C4 hydrocarbon stream in a deisobutanizer unit to produce an isobutane-rich stream containing >90 wt.% to 100 wt.% isobutane and an normal butane-rich stream containing >90 wt.% to 100 wt.% normal butane. These isobutane- and n-butane-rich streams are prepared by distilling a fresh C4 feed, a recycle stream after a hydrogenation process, or any other C4-containing stream containing n-butane and isobutane as components in a distillation unit, preferably a deisobutanizer unit. The overhead stream of the distillation unit forms an isobutane-rich stream for the production of MTBE by dehydrogenation or etherification, which is used for the production of MA, fed to a steam cracker as a steam cracker feed, or both. The bottoms stream from the deisobutanizer unit contains C5+ hydrocarbons and can be further processed, for example by recycling to a steam cracker.

[0006] B. Description of Related Art

[0007] Methyl tert-butyl ether (MTBE) is a flammable liquid used as an additive for unleaded gasoline to increase octane and oxygen levels and reduce polluting emissions. MTBE is prepared from isobutane or isobutene, which preferably comes from a crude steam cracker or fluid catalytic cracker (FCC) C4 hydrocarbon stream. The C4 hydrocarbon stream contains a mixture of C4 hydrocarbons including butane and isobutane from a fresh C4 stream, a hydrogenated C4 recycle stream from a steam cracker or from a fluid catalytic cracking process, and isobutane must be separated from the C4 hydrocarbon stream for MTBE synthesis, or isobutane must be prepared from n-butane by isomerization in a butane isomerization unit, also known as butane isomerization.

[0008] On the other hand, maleic anhydride (MA) is produced from n-butane, which must therefore be separated to produce this product.

[0009] In summary, while technologies exist to produce MTBE and / or maleic anhydride (MA), they can be energy inefficient and expensive.

[0010] Therefore, although technology exists for producing MTBE and maleic anhydride (MA), new and more efficient systems and methods for making these products are needed. It would be particularly beneficial to produce these products from C4 streams without the need to isomerize n-butane to make MTBE. Summary of the invention

[0011] It has been found that a solution is provided for at least one problem associated with the preparation of MTBE and / or maleic anhydride. One aspect relates to a process for producing MTBE and / or maleic anhydride from a C4 stream containing a mixture of C4 hydrocarbons containing n-butane and isobutane.

[0012] The present invention relates to a method for preparing methyl tert-butyl ether (MTBE). The method comprises the following steps: separating a stream with a boiling point of less than 200°C, a bottom stream containing fuel and asphalt, and a steam cracker feed from a hydrocarbon feed; feeding the steam cracker stream to a steam cracker and reacting under certain conditions to form a reaction product, the reaction product comprising hydrogen, methane, ethylene, propylene, 1,3-butadiene, 1-butene, 2-butene, isobutylene, isobutane, normal butane, cracked gas, fuel oil and unreacted ethane, propane and C4 paraffins; separating light (gas), olefins, cracked gas, fuel oil from the reaction product to form C4 olefins (1,3 butadiene, 1-butene, 2-butene, isobutylene) and C4 paraffins (isobutane and normal butane), referred to as crude steam cracked C4. 1,3-Butadiene, isobutylene, and 1-butene for MTBE production are separated from the C4 olefin stream and can be recovered as products, while the rest of the stream (called Raff-3) contains 2-butene, isopropane, and normal butane. The Raff-3 stream is fed to a hydrogenation unit to form C4 paraffins and produce a hydrogenated C4 stream comprising a mixture of mainly isobutane and normal butane. The hydrogenated C4 stream is combined with a fresh C4 hydrocarbon stream to form a combined C4 paraffin stream, and the combined C4 paraffin stream is fed to a deisobutanizer unit to form an isobutane stream, a normal butane stream comprising normal butane, and an optional bottom stream comprising C5+ hydrocarbons. The normal butane stream is a side draw stream from the deisobutanizer unit and is rich in normal butane, and is fed to an isomerization unit to convert normal butane into isobutane under conditions sufficient to achieve isomerization of normal butane to isobutane. The effluent from the isomerization reactor is recycled back to the deisobutanizer (DIB) unit for separation. The deisobutanizer overhead stream is rich in isobutane and is fed to an isobutane dehydrogenation (IBDH) unit where isobutene is produced under conditions sufficient to convert isobutane to isobutene. A crude C4 stream is separated from the steam cracker and contains 1,3-butadiene, isobutene, 1-butene, 2-butene, and saturated C4 hydrocarbons (i.e., isobutane and n-butane). 1,3-Butadiene is removed from the crude C4 stream to produce a stream called Raff-1, and the Raff-1 stream is fed to the MTBE unit. Raff-1 is mixed with the IBDH effluent and methanol to produce MTBE. The remaining stream after the isobutene conversion can be fed to a 1-butene recovery unit, and the remaining stream can be hydrogenated. The hydrogenated stream contains a mixture of isobutane and normal butane and can be sent to a steam cracker to produce olefins, or alternatively fed to a DIB unit to produce isobutene for MTBE production. The overhead effluent stream produced by the DIB unit contains C3 hydrocarbons, and the bottoms stream produced by the DIB unit contains mainly C5+ hydrocarbons.The C3 hydrocarbon and C5+ hydrocarbon streams can be processed in a stream cracker to produce various products including C2-C3 olefins, methane, hydrogen, and heavier products such as pyrolysis gas and fuel oil.

[0013] Aspects also relate to a process for preparing methyl tert-butyl ether (MTBE). The process comprises the steps of separating a stream having a boiling point of less than 200° C., a bottoms stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising 1,3-butadiene, isobutylene, 1-butene, 2-butene, and C4 paraffins (isobutane and n-butane) from a hydrocarbon feed. The complete crude C4 hydrocarbon stream from the steam cracker is hydrogenated to form C4 paraffins and produce a hydrogenated C4 stream comprising mainly isobutane and normal butane; the hydrogenated C4 stream is combined with a fresh C4 hydrocarbon stream (which may, for example, comprise 2 to 5 wt.% C3 hydrocarbons, 25 to 35 wt.% isobutane, 65 to 75 wt.% normal butane and 1% to 2 wt.% C5+) to form a combined C4 paraffin stream; the combined C4 paraffin stream is fed to a deisobutanizer unit to form an isobutane stream, an normal butane stream comprising normal C4 butane, and an optional bottoms stream comprising C5+ hydrocarbons. The remainder of the process is as described above.

[0014] The application also discusses other embodiments of the present invention.Any embodiment discussed about one aspect of the present invention is also applicable to other aspects of the present invention, and vice versa.Each embodiment described herein is understood to be an embodiment of the present invention applicable to other aspects of the present invention.It is expected that any embodiment or aspect discussed herein can be combined with other embodiments or aspects discussed herein, and / or can be implemented for any method or composition of the present invention, and vice versa.In addition, composition of the present invention can be used to realize method of the present invention.

[0015] Following are definitions of various terms and phrases used in this specification.

[0016] The term "C# hydrocarbons", where "#" is a positive integer, is meant to describe all hydrocarbons having # carbon atoms. Furthermore, the term "C#+ hydrocarbons" is meant to describe all hydrocarbon molecules having # or more carbon atoms. Thus, the term "C2+ hydrocarbons" is intended to describe a mixture of hydrocarbons having 2 or more carbon atoms. The term "C2+ alkanes" therefore relates to alkanes having 2 or more carbon atoms.

[0017] "Cracking" refers to a process involving the decomposition of organic compounds and the reorganization of molecules to produce a greater number of molecules than originally present. In cracking, a series of reactions occur with the transfer of hydrogen atoms between molecules. For example, naphtha can undergo thermal cracking reactions to form ethylene and hydrogen, methane, ethylene, propylene, 1,3-butadiene, C4 olefins, C4 paraffins, BTX and PFO, and other products.

[0018] "Hydrocarbons" are generally defined as molecules formed primarily of carbon and hydrogen atoms. Hydrocarbons may also include other elements, such as, but not limited to, halogens, metallic elements, nitrogen, oxygen, and / or sulfur. Hydrocarbon fluids may include, entrain, or be entrained in non-hydrocarbon fluids, such as hydrogen, nitrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, water, and / or ammonia.

[0019] The term "about" or "approximately" is defined as close to what one of ordinary skill in the art understands. In a non-limiting embodiment, the term is defined as within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0020] The terms "wt. %", vol. %"or" mol. "%" refers to the weight percent, volume percent or mole percent of a component based on the total weight, total volume or total number of moles containing the component, respectively. In a non-limiting example, 10 grams of a component in 100 grams of material is 10 wt.% of the component.

[0021] The term "substantially" and variations thereof are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0022] When used in the claims and / or specification, the terms "inhibit" or "reduce" or "prevent" or "avoid" or any variation of these terms includes any measurable reduction or complete inhibition to achieve the desired result.

[0023] The term "effective" as used in the specification and / or claims means sufficient to achieve a desired, intended, or expected result.

[0024] The use of the word "a" or "an" when used in conjunction with any of the terms "comprising," "including," "containing," or "having" in the claims or specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more."

[0025] The words "comprise" (and any forms of including, such as "contain" and "including"), "have" (and any forms of having, such as "have" and "having"), "include" (and any forms of including, such as "includes" and "including"), or "contains" (and any forms of containing, such as "contains" and "containing") are inclusive or open-ended and do not exclude additional unrecited elements or method steps.

[0026] The systems and methods of the present invention may "comprise," "consist essentially of," or "consist of" specific ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transition phrase "consist essentially of," in one non-limiting aspect, a fundamental and novel feature of the systems and methods of the present invention is their ability to produce olefin products (e.g., ethylene) in a cost and energy efficient manner via an ethane steam cracking unit that is capable of receiving ethane from a mixed feed steam cracker unit and feeding the C2+ product produced by the ethane steam cracker unit to the mixed feed steam cracker unit.

[0027] Other objects, features and advantages of the present invention will become apparent through the following drawings, detailed descriptions and examples. However, it should be understood that the drawings, detailed descriptions and examples, although indicating specific embodiments of the present invention, are given by way of illustration only and are not meant to be limiting. In addition, it is contemplated that changes and modifications within the inventive concept and scope of the present invention will become apparent to those skilled in the art from this detailed description. In other embodiments, features from a specific embodiment may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any other embodiment. In other embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Advantages of the present invention may become apparent to those skilled in the art having the benefit of the following detailed description and with reference to the accompanying drawings.

[0029] Figure 1 One embodiment of a system for producing MTBE, 1-butene, and n-butane without hydrogenating a crude C4 stream is shown.

[0030] Figure 2 One embodiment of a system for producing MTBE, 1-butene, and n-butane by fully hydrogenating a crude C4 stream is shown.

[0031] Figure 3 One embodiment of a system for producing maleic anhydride from n-butane without hydrogenating a crude C4 stream is shown.

[0032] Figure 4 An embodiment of a system for producing maleic anhydride from n-butane by fully hydrogenating a crude C4 stream is shown.

[0033] Figure 5 One embodiment of a system utilizing a steam cracker to produce MTBE, 1-butene, and n-butane without hydrogenating a crude C4 stream is shown.

[0034] Figure 6An embodiment of a system for producing MTBE, 1-butene, and n-butane utilizing a steam cracker with full hydrogenation of a crude C4 stream is shown.

[0035] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be drawn to scale. DETAILED DESCRIPTION

[0036] It has been found that a solution is provided for at least one of the problems associated with the preparation of MTBE and maleic anhydride. In one aspect, a crude mixed C4 hydrocarbon feed can be fed to a deisobutanizer unit to produce an isobutane stream, an n-butane stream, and a C5+ stream. The crude C4 stream is produced by a steam cracker and is preferably provided by feeding crude oil to a feed preparation unit where the crude oil is separated to produce gas and liquid streams, and a cracker bottoms stream comprising fuel and asphalt.

[0037] The isobutane stream is fed to an isobutane dehydrogenation unit to produce isobutene, which is then fed to an MTBE synthesis unit where it reacts with methanol to produce MTBE. A portion of the isobutane-rich stream may be fed to a polyethylene unit.

[0038] The n-butane stream may be recovered as a product, or it may be fed to a maleic anhydride synthesis unit to react under reaction conditions to produce maleic anhydride, or alternatively or in combination to a steam cracker to increase the production of ethylene and other chemical products.

[0039] Conditions in the maleic anhydride unit include temperatures of 375°C to 425°C. Typical conversions are 80 to 86 wt% conversion of n-butane, which produces 50-60 wt% maleic anhydride. Maleic anhydride is produced from n-butane (purity greater than 95 wt%) by various commercial technologies using fixed and fluidized bed reactors. As an example, the use of a catalyst such as vanadyl pyrophosphate (VO)2P2O7 with trimethyl phosphate as a promoter can produce 90 wt.% MA, and 1.1 to 1.2 tons of n-butane will be consumed per ton of MA. The reaction is oxidative and exothermic, requiring heat to be removed from the reactor.

[0040] Reaction formula: C4H8+3.5O2→C4H2O3+H2O

[0041] C4H8+6.5O2→4CO2+5H2O

[0042] C4H8+4.5O2→4CO+5H2O

[0043] The effluent from the reactor contains gaseous maleic anhydride, water, acrylic acid, acetic acid, CO, CO2, O2, N2 and unreacted n-butane, which is cooled to 120°C in a series exchanger. The cooled mixture is then sent to a solvent absorption system to absorb MA. Exemplary suitable solvents include dialkyl phthalates, dimethyl benzophenone and dichlorodiphenyl ether. MA is then separated from the absorption liquid to obtain crude MA. The solvent extraction system recovers 90-96wt% of maleic anhydride with a purity of >99wt% from the waste gas effluent.

[0044] The gas and liquid streams from the feed preparation unit are sent to a steam cracker where they react under thermal conditions to produce olefins and other products.

[0045] refer to Figure 1 , describes a system 100 for producing MTBE. The system 100 may include a feed separation unit 102, a steam cracking unit 104, a butadiene recovery unit 117, a selective hydrogenation, MTBE, 1-butene unit 111, a deisobutanizer unit 106, an isobutane dehydrogenation unit 109, a polyethylene unit 125, and a full hydrogenation unit 120. Crude oil 101 enters the feed separation unit 102, producing a steam cracker feed 115 and fuel and asphalt 130. A first fresh C4 stream 103 combined with hydrogenated C4 from the full hydrogenation unit 120 is fed to the deisobutanizer 106 and the steam cracker, where the exhaust stream 108 is enriched in C3. The overhead liquid streams 141 and 142 containing rich isobutane (iC4), the second stream (side draw) 107 containing rich n-butane, and the third stream 105 containing C5+ hydrocarbons are sent to the steam cracker 104. The first stream containing isobutane is fed to the isobutane dehydrogenation unit 109, where the isobutane reacts with the catalyst to form the isobutylene (iC4=) product 110. The isobutylene product from the butadiene recovery unit 109 is fed to the MTBE synthesis unit 111 in combination with the Raff-1 from the butadiene recovery unit 117 unit and is mixed with methanol from the methanol stream 112, which is fed to the MTBE synthesis unit under conditions sufficient to produce MTBE. The 1-butene product is produced from the raffinate stream of the MTBE unit. The Raff-3 stream 114 from the MTBE synthesis unit 111 is fully hydrogenated in the full hydrogenation unit 120 to produce a saturated C4 stream 121 which is recycled to the deisobutanizer 106 .

[0046] MTBE and 1-butene are separated from unreacted isobutylene, 1-butene, 2-butene and other paraffinic C4 hydrocarbons to form MTBE and 1-butene product stream 113, with the remainder leaving the MTBE unit as MTBE effluent stream 114 (Raff-3).

[0047] Gas and liquid stream 115 contains hydrocarbons other than C4 hydrocarbons and is fed to steam cracker 104 where the feed is thermally cracked to produce olefins and other products. Olefins and other steam cracker products are recovered in stream 116. Crude C4 hydrocarbon stream 119 from steam cracker 104 may be fed to butadiene recovery unit 117 where 1,3 butadiene product is separated as product stream 118 and combined with olefin product stream 116 and preferably collected for use. After butadiene recovery, Raff-1 stream 122 is combined with isobutylene-rich stream 110 from unit 109 to unit 111 where MTBE and 1-butene products are produced 113.

[0048] The first stream 140 from the deisobutanizer may be split into stream 141 and stream 142 , with stream 141 being sent to the isobutane dehydrogenation unit 109 and a small portion 140 being sent as product stream 142 to the polymer plant (PE).

[0049] The second stream 107 from the deisobutanizer is enriched in nC4 as product.

[0050] Crude oil 101 can be the oil of unrefined form extracted from geological formation.Term crude oil can also include the oil that has been subjected to water-oil separation and / or gas-oil separation and / or desalting and / or stabilization.Non-limiting examples of crude oil include Arabian heavy, Arabian light, other Gulf crude oil, Brent crude oil, North Sea crude oil, North Africa and West Africa crude oil, Indonesian crude oil, Chinese crude oil, West Texas crude oil and mixture thereof, and also include shale oil, asphalt sand, gas condensate and bio-based oil.The crude oil used as the feed of the inventive method is preferably conventional oil with a specific gravity greater than 20 ° API measured by API according to ASTM D287 standard.On the one hand, the crude oil used for the inventive method is a light crude oil with an API specific gravity greater than 30 ° API.On the other hand, the crude oil used for the inventive method can include Arabian light crude oil.Arabian light crude oil usually has an API gravity of 32 ° -36 ° API and a sulfur content of 1.5-4.5wt.%.

[0051] refer to Figure 2 , shows an alternative process where a crude C4 stream 119 is fed directly to a hydrogenation unit 120, and a saturated C4's stream 121 leaves the hydrogenation unit 120 via a hydrogen stream 123 and is combined with a fresh C4 stream 103. In this example, methanol is combined with an isobutylene stream 110, and this combined isobutylene / methanol stream 201 is fed to a MTBE synthesis unit 111 where it reacts to produce MTBE.

[0052] Figure 3 Similar to Figure 1, except that the second feed stream 107 containing n-butane is fed to the maleic anhydride synthesis unit 301 to produce the maleic anhydride product 302.

[0053] Figure 4 Similar to Figure 2 , except that the second feed stream 107 containing n-butane is fed to the maleic anhydride synthesis unit 301 to produce the maleic anhydride product 302.

[0054] Figure 5 Similar to Figure 1 , except that the second stream 107 containing n-butane is combined with the C5+ stream 105 and the C3's stream 108 to form a mixed steam cracker feed stream 501, which is fed to the steam cracker 104. The gas and liquid stream 115 may be combined with the mixed steam cracker feed stream 501 before entering the steam cracker 104.

[0055] Figure 6 Similar to Figure 2 , except that the second stream 107 containing n-butane is combined with the C5+ stream 105 and the C3's stream 108 to form a mixed steam cracker feed stream 501, which is fed to the steam cracker 104. The gas and liquid stream 115 can be combined with the mixed steam cracker feed stream 501 before entering the steam cracker 104.

[0056] The hydrogenation reaction is carried out at a pressure of 22-32 bara and a temperature of 58-125°C. The hydrogen to feed ratio is 0.01-0.03 wt. / wt. A portion of H2 is separated from the cold box separator flash tank. Another portion of H2 and methane can be separated from the demethanizer unit.

[0057] The first stream containing isobutane is fed to an isobutane dehydrogenation unit 109 where the isobutane reacts with a catalyst to form an isobutylene (iC4=) product 110. The isobutylene product from 109 is combined with Raff-1 from unit 117 and fed to an MTBE synthesis unit 111 and mixed with methanol from a methanol stream 112 which is fed to the MTBE synthesis unit under conditions sufficient to produce MTBE. The 1-butene product is produced from the raffinate stream of the MTBE unit. The Raff-3 stream 114 from unit 111 is fully hydrogenated in 120 to produce a saturated C4's stream 121 which is recycled to the deisobutanizer.

[0058] The dehydrogenation reaction is an equilibrium reaction that prefers low pressure. The reaction is highly endothermic and requires a large amount of heat to be supplied to a radial flow moving bed reactor in series or a fixed bed with a stable heterogeneous catalyst. The isobutane dehydrogenation reaction is carried out at a pressure of 0.5-15 psia and a temperature of 550-700°C. The conversion of isobutane is 45-65wt.%, and the selectivity is 87-95wt.%. The following reactions occur in the dehydrogenation of isobutane:

[0059] iGO 10 →iC4H8+H2

[0060] MTBE and 1-butene are separated from unreacted isobutylene, 1-butene, 2-butene and other paraffinic C4 to form MTBE and 1-butene product stream 113, with the remainder leaving the MTBE unit as MTBE effluent stream 114 (Raff-3). Typical components of the Raff-3 stream are provided in the following table:

[0061]

[0062]

[0063] The gas and liquid stream 115 free of C4's is fed to the steam cracker 104 where the feed is thermally cracked to produce olefins and other products. Olefins and other steam cracker products are recovered in stream 116. The crude C4 hydrocarbon stream 119 from the steam cracker 104 may be fed to a butadiene recovery unit 117 where the 1,3 butadiene product is separated as product stream 118 and combined with the olefin product stream 116 and collected for use. After butadiene recovery, the Raff-1 stream 122 is combined with the isobutylene-rich stream 110 from unit 109 to unit 111 where MTBE and 1-butene products are produced 113. The Raff-1 stream may comprise, for example, preferably 45 wt.% to 58 wt.% isobutylene, 12 wt.% to 27 wt.% 1-butene, 5 wt.% to 16 wt.% 2-butene (both cis- and trans-2-butene), 5 wt.% to 12 wt.% isobutane, 2 wt.% to 8 wt.% n-butane, and <1% 1,3-butadiene.

[0064] In the steam cracking process, saturated hydrocarbons are broken down into smaller, usually unsaturated hydrocarbons, such as ethylene, propylene, 1,3-butadiene, butenes, cracked gases, etc., by diluting a mixed hydrocarbon feed with steam and heating the mixture in a furnace in the absence of oxygen. The steam cracking reaction may have a residence time of 50-1000 milliseconds. The steam cracker effluent is separated via a downstream separation section (not shown), where the steam cracking products are separated from the unreacted components. These fractionation / separation units are well known in the art.

[0065] In the separation unit downstream of the steam cracker, the steam cracker effluent is cooled from 850°C to 180°C via a series of transfer line exchanges, where high-pressure steam is produced. The cooled effluent is sent to a quench oil or primary fractionation system to recover fuel oil. The overhead stream of the primary fractionator is sent to a quench water tower, where the effluent is further cooled by direct contact with water. The overhead stream of the quench tower contains hydrocarbons with a boiling point of about 30°C-45°C, while the bottom stream contains cracked gas related components with a boiling point of about 70°C-85°C. The bottom of the quench section contains a settler to separate the cracked gas from the water. Water is used as a heating medium and is recycled back to the quench tower.

[0066] The top effluent is sent to the cracked gas compressor where it is compressed to 30bar-45bar. After passing through the third stage compressor, CO2 and H2S can be separated in the caustic tower, CO and other are impurity grade components. The remaining stream can be sent to the fourth and fifth stages of the compressor to reach pressure.

[0067] After compression, the effluent is dried in a dryer and cooled by exchanging heat with various streams. A portion of the H2 can be separated with a cold box separator flash tank. The remaining H2 and methane are separated from the top of the demethanizer.

[0068] The demethanizer bottoms stream is sent to a deethanizer unit where the C2 hydrocarbons are separated into acetylene, ethylene and ethane. The bottoms stream of the deethanizer unit contains C3+ hydrocarbons and can be sent to a depropanizer unit. The C2 stream from the deethanizer can be sent to C2 acetylene which is converted into ethylene and ethane in an acetylene reactor, where ethylene is recovered in a C2 splitter column and the bottoms of the C2 splitter are ethane which is recycled back to the steam cracker.

[0069] The depropanizer overheads sent to the MAPD can be converted to propane and propylene in a C3 acetylene reactor. Propylene can be recovered as a product via a C3 splitter, and the bottoms stream of the C3 splitter contains propane and can be recycled back to the steam cracker.

[0070] The bottom of the depropanizer can be fed to a debutanizer unit to separate the C4 stream from the C5+. The debutanizer top contains a crude C4 stream containing limited C3, C5's and C4 acetylenes and most of 1,3-butadiene, isobutylene, 1-butene, 2-butene (cis and trans), n-C4 and iC4. This stream is called a crude C4 stream.

[0071] The C5+ stream, called cracked gas, is hydrogenated in a gasoline hydrogenation unit and sent to a depentanizer unit to separate the C5 hydrocarbons from the C6 stream. The overhead stream of the depentanizer unit is mainly C5 paraffins (nC5 and isoC5) which are recycled back to the steam cracker.

[0072] The C6+ stream is further processed in a hydrodealkylation unit to convert other C6+ components into benzene in the presence of hydrogen. The final benzene product can be recovered from the hydrodealkylation unit.

[0073] Fuel oil or gas oil product may be recovered from the bottom of the quench oil and quench water towers.

[0074] C9+ hydrocarbons can be recovered from benzene plants.

[0075] The first stream 140 from the deisobutanizer may be split into stream 141 and stream 142 , with stream 141 being sent to the isobutane dehydrogenation unit 109 and a small portion 140 being sent as product stream 142 to the polymer plant (PE).

[0076] Aspects also relate to a process for preparing methyl tert-butyl ether (MTBE), the process comprising the steps of: separating a gaseous stream having a boiling point of less than 200° C., a bottoms stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream comprises normal butane and isobutane; feeding the gaseous stream to a steam cracker, and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising C4 olefins and unreacted C4 paraffins; separating the C4 olefins and unreacted C4 paraffins from the reaction product to form a crude steam cracked C4 stream containing C4 olefins and unreacted C4 paraffins, feeding the crude steam cracked C4 stream to a hydrogenation unit; hydrogenating the crude steam cracked C4 stream in the hydrogenation unit to hydrogenate the C4 olefins to form C4 paraffins and produce hydrogen containing isobutane and normal butane; The invention relates to a process for preparing a C4 stream by a steam cracker. The process comprises: preparing a C4 stream by a hydrogenation step; combining the hydrogenated C4 stream with a crude C4 hydrocarbon stream to form a combined C4 paraffin stream; feeding the combined C4 paraffin stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butane, and a bottoms stream comprising C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture comprising isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to an MTBE synthesis unit; and reacting isobutene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of the distillate stream, the unreacted portion comprising isobutane and 1-butene; combining the n-butane stream and the bottoms stream comprising C5+ hydrocarbons to form a combined C4 / C5+ stream and feeding the combined C4 / C5+ stream to a steam cracker. Preferably, the hydrocarbon feed is crude oil. The reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550° C. to 700° C. The conversion of isobutane is 45-65 wt.%, and the selectivity is 87-95 wt.%.

[0077] Various aspects provide a method for preparing methyl tert-butyl ether (MTBE), the method comprising the steps of: separating a gaseous stream having a boiling point of less than 200° C., a bottom stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream comprises normal butane and isobutane; feeding the gaseous stream to a steam cracker, and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising olefins, wherein the olefins include C4 olefins; separating the C4 olefins to form a C4 olefin stream and feeding the C4 olefin stream to a hydrogenation unit; hydrogenating the C4 olefin stream with hydrogen under conditions such that the C4 olefins are hydrogenated to form C4 paraffins comprising isobutane and normal butane; The present invention relates to a process for preparing a C4 hydrocarbon synthesis unit comprising: combining alkanes with a fresh C4 hydrocarbon stream to form a combined C4 stream; feeding the combined C4 hydrocarbon stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butane, and a bottoms stream containing C5+ hydrocarbons; feeding the isobutane stream to the isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture containing isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to an MTBE synthesis unit; and reacting the isobutene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of the distillate stream, the unreacted portion comprising isobutane and 1-butene; combining the n-butane stream and the bottoms stream containing C5+ hydrocarbons to form a combined C4 / C5+ stream and the combined C4 / The C5+ stream is fed to the steam cracker. Preferably, the hydrocarbon feed is crude oil. The reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550°C-700°C. The reaction conditions during hydrogenation include a pressure of 22-32 bara and a temperature of 50-125°C. The ratio of hydrogen to feed is 0.01-0.03 wt. / wt.

[0078] Non-limiting examples of the present invention will now be described. Example 1 is a method for preparing methyl tert-butyl ether (MTBE). The method comprises the following steps: separating a gaseous stream having a boiling point of less than 200°C, a bottom stream containing fuel and asphalt, and a crude C4 hydrocarbon stream containing C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream contains n-butane and isobutane; feeding the gaseous stream to a steam cracker, and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product containing C4 olefins and unreacted C4 paraffins; separating C4 olefins and unreacted C4 paraffins from the reaction product to form a crude steam-cracked C4 stream containing C4 olefins and unreacted C4 paraffins, and feeding the crude steam-cracked C4 stream to a hydrogenation unit; hydrogenating the crude steam-cracked C4 stream in the hydrogenation unit to hydrogenate the C4 olefins to form C4 paraffins and A hydrogenated C4 stream containing isobutane and normal butane is produced; the hydrogenated C4 stream is combined with a crude C4 hydrocarbon stream to form a combined C4 paraffin stream; the combined C4 paraffin stream is fed to a deisobutanizer unit to form an isobutane stream, an normal butane stream containing normal C4 butane, and optionally a bottoms stream containing C5+ hydrocarbons; the isobutane stream is fed to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture containing isobutene and unreacted C4 hydrocarbons; the C4 hydrocarbon mixture is fed to an MTBE synthesis unit; and isobutene is reacted with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; methyl tert-butyl ether is separated from the unreacted portion of the distillate stream, the unreacted portion containing isobutane and 1-butene. Example 2 is the method of Example 1, wherein the normal butane stream is fed to a maleic anhydride unit. Example 3 is the method of Example 1, wherein the hydrocarbon feed is crude oil. Example 4 is the process of Example 1, wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550° C.-700° C. Example 5 is the process of Example 1, wherein the reaction conditions during hydrogenation include a pressure in the range of 22-32 bara and a temperature of 50-125° C. The ratio of hydrogen to feed is 0.01-0.03 wt. / wt.Embodiment 6 is a method for preparing methyl tert-butyl ether (MTBE), which comprises the following steps: separating a gaseous stream having a boiling point of less than 200° C., a bottom stream containing fuel and asphalt, and a crude C4 hydrocarbon stream containing C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream contains normal butane and isobutane; feeding the gaseous stream to a steam cracker, and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product containing olefins, wherein the olefins contain C4 olefins; separating the C4 olefins to form a C4 olefin stream and feeding the C4 olefin stream to a hydrogenation unit; hydrogenating the C4 olefins with hydrogen under conditions that hydrogenate the C4 olefins to form C4 paraffins containing isobutane and normal butane; Hydrogenating a C4 olefin stream; combining C4 paraffins with a fresh C4 hydrocarbon stream to form a combined C4 stream; feeding the combined C4 hydrocarbon stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butane, and a bottoms stream containing C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture containing isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to an MTBE synthesis unit; reacting isobutene with methanol in the presence of a catalyst in an MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of the distillate stream, the unreacted portion containing isobutane and 1-butene. Example 7 is the method of Example 2, wherein the n-butane stream is fed to a maleic anhydride unit. Example 8 is the method of Example 2, wherein the hydrocarbon feed is crude oil. Embodiment 9 is the process of embodiment 2, wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550° C.-700° C. Embodiment 10 is the process of embodiment 2, wherein the reaction conditions during hydrogenation include a pressure of 22-32 bara and a temperature of 50-125° C. The ratio of hydrogen to feed is 0.01 to 0.03 wt. / wt.Embodiment 11 is a method for preparing methyl tert-butyl ether (MTBE), which comprises the following steps: separating a gaseous stream having a boiling point of less than 200° C., a bottom stream containing fuel and asphalt, and a crude C4 hydrocarbon stream containing C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream contains normal butane and isobutane; feeding the gaseous stream to a steam cracker and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product containing C4 olefins and unreacted C4 paraffins; separating C4 olefins and unreacted C4 paraffins from the reaction product to form a crude steam-cracked C4 stream containing C4 olefins and unreacted C4 paraffins, and feeding the crude steam-cracked C4 stream to a hydrogenation unit; hydrogenating the crude steam-cracked C4 stream in the hydrogenation unit to hydrogenate the C4 olefins to form C4 paraffins and produce a hydrogenated C4 stream containing isobutane and normal butane. stream; combining the hydrogenated C4 stream with a crude C4 hydrocarbon stream to form a combined C4 paraffin stream; feeding the combined C4 paraffin stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butane, and a bottoms stream containing C5+ hydrocarbons; feeding the isobutane stream to the isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture containing isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to an MTBE synthesis unit; and reacting isobutene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of the distillate stream, the unreacted portion containing isobutane and 1-butene; combining the n-butane stream and the bottoms stream containing C5+ hydrocarbons to form a combined C4 / C5+ stream and feeding the combined C4 / C5+ stream to a steam cracker. Embodiment 12 is the process of embodiment 11, wherein the hydrocarbon feed is crude oil. Embodiment 13 is the process of embodiment 11, wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5 psia to 15 psia and a temperature of 550° C. to 700° C. Embodiment 14 is the process of embodiment 11, wherein the reaction conditions during hydrogenation include a pressure of 22-32 bara and a temperature of 50-125° C. The ratio of hydrogen to feed is 0.01-0.03 wt. / wt.Embodiment 15 is a method for preparing methyl tert-butyl ether (MTBE), which comprises the following steps: separating a gaseous stream having a boiling point of less than 200° C., a bottom stream containing fuel and asphalt, and a crude C4 hydrocarbon stream containing C4 hydrocarbons from a hydrocarbon feed, wherein the crude C4 hydrocarbon stream contains normal butane and isobutane; feeding the gaseous stream to a steam cracker, and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product containing olefins, wherein the olefins contain C4 olefins; separating the C4 olefins to form a C4 olefin stream and feeding the C4 olefin stream to a hydrogenation unit; hydrogenating the C4 olefin stream with hydrogen under conditions such that the C4 olefins are hydrogenated to form C4 paraffins containing isobutane and normal butane; combining the C4 paraffins with a fresh C4 hydrocarbon stream to form a combined C4 stream; feeding the combined C4 hydrocarbon stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butane, and a bottoms stream containing C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture containing isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to an MTBE synthesis unit; and reacting isobutene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of the distillate stream, the unreacted portion containing isobutane and 1-butene; combining the n-butane stream and the bottoms stream containing C5+ hydrocarbons to form a combined C4 / C5+ stream and feeding the combined C4 / C5+ stream to a steam cracker. Example 16 is the method of Example 15, wherein the hydrocarbon feed is crude oil. Embodiment 17 is the method of embodiment 15, wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5 psia to 15 psia and a temperature of 550° C. to 700° C. Embodiment 18 is the method of embodiment 15, wherein the reaction conditions during hydrogenation include a pressure of 22-32 bar and a temperature of 50-125° C. The ratio of hydrogen to feed is 0.01 to 0.03 wt. / wt. Embodiment 19 is the method of any of the preceding embodiments, wherein the maleic anhydride unit temperature is 375° C. to 425° C.

[0079] *****

[0080] Although the embodiments and advantages of the present application have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the concept and scope of the embodiments defined by the appended claims. In addition, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, material compositions, means, methods and steps described in the specification. As will be easily understood by those of ordinary skill in the art from the above disclosure, the processes, machines, manufactures, material compositions, devices, methods or steps that currently exist or are developed later to perform functions substantially the same as the corresponding embodiments described herein or to achieve results substantially the same as the corresponding embodiments described herein can be utilized. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, means, methods or steps within their scope.

Claims

1. A method for preparing methyl tert-butyl ether, characterized in that: The method comprises the following steps: Separating from the hydrocarbon feed a gaseous stream having a boiling point of less than 200° C., a bottoms stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons, wherein the crude C4 hydrocarbon stream comprises n-butane and isobutane; feeding the gaseous stream to a steam cracker and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising C4 olefins and unreacted C4 paraffins; separating the C4 olefins and the unreacted C4 paraffins from the reaction product to form a crude steam cracked C4 stream containing the C4 olefins and the unreacted C4 paraffins, and feeding the crude steam cracked C4 stream to a hydrogenation unit; hydrogenating the crude steam cracked C4 stream in the hydrogenation unit to hydrogenate the C4 olefins to form C4 paraffins and produce a hydrogenated C4 stream comprising isobutane and normal butane; combining the hydrogenated C4 feed stream with the crude C4 hydrocarbon stream to form a combined C4 paraffin stream; feeding the combined C4 paraffin stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butanes, and optionally a bottoms stream comprising C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture comprising isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to a MTBE synthesis unit; and reacting the isobutylene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; and The methyl tert-butyl ether is separated from the unreacted portion of the distillate stream, which comprises isobutane and 1-butene.

2. The method according to claim 1, characterized in that: Wherein the n-butane stream is fed to a maleic anhydride unit.

3. The method according to claim 1, characterized in that Wherein the hydrocarbon feed is crude oil.

4. The method according to claim 1, characterized in that: The reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550°C-700°C.

5. The method according to claim 1, characterized in that The reaction conditions during hydrogenation include a pressure of 22-32 bar and a temperature of 50-125° C., and a ratio of hydrogen to feed of 0.01-0.03 wt. / wt.

6. A method for preparing methyl tert-butyl ether, characterized in that: The method comprises the following steps: Separating from the hydrocarbon feed a gaseous stream having a boiling point of less than 200° C., a bottoms stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons, wherein the crude C4 hydrocarbon stream comprises n-butane and isobutane; feeding the gaseous stream to a steam cracker and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising olefins, wherein the olefins comprise C4 olefins; separating the C4 olefins to form a C4 olefin stream and feeding the C4 olefin stream to a hydrogenation unit; hydrogenating the C4 olefin stream with hydrogen under conditions such that the C4 olefins are hydrogenated to form C4 paraffins comprising isobutane and normal butane; combining the C4 paraffins with a fresh C4 hydrocarbon stream to form a combined C4 stream; feeding the combined C4 hydrocarbon stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butanes, and a bottoms stream comprising C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture comprising isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to a MTBE synthesis unit; and reacting the isobutylene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; and The methyl tert-butyl ether is separated from the unreacted portion of the distillate stream, which comprises isobutane and 1-butene.

7. The method according to claim 2, characterized in that: wherein the n-butane stream is fed to a maleic anhydride unit, and / or wherein the hydrocarbon feed is crude oil, and / or wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 50° C.-700° C., and / or Wherein the reaction conditions during hydrogenation include a pressure of 22-32 bara and a temperature of 50-125° C. and / or a hydrogen to feed ratio of 0.01-0.03 wt. / wt.

8. A method for preparing methyl tert-butyl ether, characterized in that: The method comprises the following steps: Separating from the hydrocarbon feed a gaseous stream having a boiling point of less than 200° C., a bottom stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons, wherein the crude C4 hydrocarbon stream comprises n-butane and isobutane; feeding the gaseous stream to a steam cracker and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising C4 olefins and unreacted C4 paraffins; separating C4 olefins and unreacted C4 paraffins from the reaction product to form a crude steam cracked C4 stream containing C4 olefins and unreacted C4 paraffins, and feeding the crude steam cracked C4 stream to a hydrogenation unit; hydrogenating the crude steam cracked C4 stream in the hydrogenation unit to hydrogenate the C4 olefins to form C4 paraffins and produce a hydrogenated C4 stream comprising isobutane and normal butane; combining the hydrogenated C4 feed stream with a crude C4 hydrocarbon stream to form a combined C4 paraffin stream; Feeding the combined C4 paraffin stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butanes, and a bottoms stream comprising C5+ hydrocarbons; feeding the isobutane stream to an isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture comprising isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to a MTBE synthesis unit; and reacting the isobutylene with methanol in the presence of a catalyst in the MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of a distillate stream, the unreacted portion comprising isobutane and 1-butene; The n-butane stream and the bottoms stream comprising C5+ hydrocarbons are combined to form a combined C4 / C5+ stream and the combined C4 / The C5+ stream is fed to the steam cracker.

9. The method according to claim 8, characterized in that wherein the hydrocarbon feed is crude oil and / or The reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550°C-700°C.

10. The method according to claim 8, characterized in that Wherein the reaction conditions during the hydrogenation include a pressure of 22-32 bara and a temperature of 50-125° C., and the ratio of hydrogen to feed is 0.01 to 0.03 wt %.

11. A method for preparing methyl tert-butyl ether (MTBE), characterized in that: The method comprises the following steps: Separating from the hydrocarbon feed a gaseous stream having a boiling point of less than 200° C., a bottom stream comprising fuel and asphalt, and a crude C4 hydrocarbon stream comprising C4 hydrocarbons, wherein the crude C4 hydrocarbon stream comprises n-butane and isobutane; feeding the gaseous stream to a steam cracker and reacting the gaseous stream with a steam cracking catalyst in the steam cracker to form a reaction product comprising olefins, wherein the olefins comprise C4 olefins; separating the C4 olefins to form a C4 olefin stream and feeding the C4 olefin stream to a hydrogenation unit; hydrogenating the C4 olefin stream with hydrogen under conditions such that the C4 olefins are hydrogenated to form C4 paraffins comprising isobutane and n-butane; combining the C4 paraffins with a fresh C4 hydrocarbon stream to form a combined C4 stream; feeding the combined C4 hydrocarbon stream to a deisobutanizer unit to form an isobutane stream, an n-butane stream containing n-C4 butanes, and a bottoms stream comprising C5+ hydrocarbons; feeding the isobutane stream to the isobutane dehydrogenation unit under process conditions sufficient to dehydrogenate the isobutane to form a C4 hydrocarbon mixture comprising isobutene and unreacted C4 hydrocarbons; feeding the C4 hydrocarbon mixture to a MTBE synthesis unit; and reacting isobutylene with methanol in the presence of a catalyst in an MTBE synthesis unit to form MTBE; separating methyl tert-butyl ether from an unreacted portion of a distillate stream, the unreacted portion comprising isobutane and 1-butene; and The n-butane stream and the bottoms stream comprising C5+ hydrocarbons are combined to form a combined C4 / C5+ stream and the combined C4 / C5+ stream is fed to a steam cracker.

12. The method according to claim 11, characterized in that wherein the hydrocarbon feed is crude oil and / or Wherein the reaction conditions in the isobutane dehydrogenation unit include a pressure of 0.5-15 psia and a temperature of 550°C-700°C.

13. The method according to claim 15, characterized in that The reaction conditions during hydrogenation include a pressure in the range of 22-32 bara and a temperature of 50-125° C., with a hydrogen to feed ratio of 0.01-0.03 wt. / wt.

14. The method according to any one of the preceding claims, characterized in that The temperature of the maleic anhydride unit is 375°C to 425°C.

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