Systems and methods for producing MTBE

Abstract

Disclosed are systems and methods for producing MTBE without the use of a catalytic distillation column or superfractionator. An optimal methanol stream volume required to maximize MTBE production and minimize isobutylene loss is fed along with a crude C4 stream to a primary reactor comprising a first and second reactors connected in parallel, configured to produce a maximum final volume of MTBE at a level greater than or equal to a commercial quality specification for a stable purity. The combined effluent from the first and second reactors is split to form a first portion, a second portion, and a third portion. The first portion is fed to a third reactor configured to produce additional MTBE. The second portion is combined with the effluent from the third reactor for further separation. The third portion is recycled to the first and / or second reactors.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from European Patent Application No. 20187063.1, filed on July 21, 2020, the entire contents of which are hereby incorporated herein by reference. Technical Field

[0003] The present invention generally relates to systems and methods for producing methyl tert-butyl ether (MTBE). More specifically, the present invention relates to systems and methods for producing MTBE using a reaction apparatus comprising two MTBE synthesis reactors connected in parallel and a third MTBE synthesis reactor connected in series. Background Art

[0004] MTBE is an organic compound used as an additive to increase the octane rating of gasoline. Since around 1970, MTBE has been synthesized by etherification of isobutylene with methanol in the presence of an acidic catalyst. The isobutylene used in MTBE synthesis can be obtained from C4 hydrocarbon process streams.

[0005] Conventionally, isobutylene and methanol are fed into a fixed bed reactor to generate an effluent containing MTBE. The effluent is then fed into a catalytic distillation column or a reactive distillation column so that the residual isobutylene in the effluent reacts with additional methanol to generate more MTBE. Some other conventional processes also use super fractionators to separate light ends (C4 and methanol) from MTBE. Catalytic distillation columns and / or super fractionators typically require large capital expenditures and operating costs, thereby increasing the production cost of MTBE. Other MTBE production systems use isothermal multitubular reactors as MTBE synthesis reactors, eliminating the need for catalytic distillation columns or reactive distillation columns. However, the capital expenditure of isothermal multitubular reactors is high, and therefore cannot solve the problems associated with high MTBE production costs.

[0006] In summary, while systems and methods exist for producing MTBE, there remains a need for improvement in this area given that conventional systems and methods suffer from at least the aforementioned disadvantages. Summary of the Invention

[0007] A solution to the aforementioned problems associated with systems and methods for producing MTBE from isobutylene and methanol has been discovered. The solution lies in a method for producing MTBE using a system comprising at least three MTBE synthesis reactors. Notably, the first and second MTBE synthesis reactors are operated in parallel, and the third MTBE synthesis reactor is operated in series with the first and second MTBE synthesis reactors. This can advantageously increase at least the overall concentration of MTBE, particularly the MTBE concentration in the product effluent stream from the third MTBE synthesis reactor. Furthermore, the disclosed system does not include a superfractionator, a catalytic distillation column (reactive distillation column), or an isothermal reactor, thereby reducing capital expenditures and / or operating costs for MTBE production compared to conventional MTBE production systems. Overall, in the disclosed method, the optimal methanol feed volume required to maximize MTBE production and minimize isobutylene loss to an acceptable minimum is fed along with a crude C4 feed stream into a primary reactor comprising a first reactor and a second reactor connected in parallel, configured to produce a maximum final MTBE volume at or above a commercial quality specification level of stable purity. Thus, the system and method of the present invention provide a solution to at least some of the problems associated with the conventional systems and methods for producing MTBE described above.

[0008] Embodiments of the present invention include a method for producing methyl tert-butyl ether. The method includes feeding isobutylene and methanol to a first reactor and a second reactor arranged in parallel. The method includes subjecting the isobutylene and methanol, respectively, in the first reactor and the second reactor, to reaction conditions sufficient to react the isobutylene with the methanol to produce a first portion of MTBE in the effluent from the first reactor and in the effluent from the second reactor. The method includes combining the effluent from the first reactor and the effluent from the second reactor to form a combined reactor effluent stream. The combined reactor effluent stream also contains isobutylene. The method includes reacting the isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third reactor connected in series with the first reactor group and the second reactor to produce a third reactor effluent stream containing a second portion of MTBE. The method includes combining the second portion of the combined reactor effluent stream with the third reactor effluent stream to form a mixed intermediate product stream. The method includes recycling a third portion of the combined effluent stream to the first reactor and the second reactor. The process also includes separating the mixed intermediate product stream to form a product stream comprising primarily MTBE, a stream comprising primarily methanol, and a C4 raffinate stream.

[0009] Embodiments of the present invention include a method for producing methyl tert-butyl ether. The method includes mixing a crude C4 feed stream containing isobutylene with methanol to form a feed stream. The method includes splitting the feed stream to form a first feed stream and a second feed stream. The method includes feeding the first feed stream to a first adiabatic fixed bed reactor and feeding the second feed stream to a second adiabatic fixed bed reactor. The method includes subjecting the isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to produce a first portion of MTBE in an effluent from the first adiabatic fixed bed reactor and in an effluent from the second adiabatic fixed bed reactor. The method includes combining the effluent from the first adiabatic fixed bed reactor and the effluent from the second adiabatic fixed bed reactor to form a combined reactor effluent stream. The combined reactor effluent stream also includes isobutylene. The method includes reacting isobutylene contained in a first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first and second adiabatic fixed bed reactors to produce a third adiabatic fixed bed reactor effluent stream containing a second portion of MTBE. The method includes combining the second portion of the combined reactor effluent stream with the third adiabatic fixed bed reactor effluent stream to form a mixed intermediate product stream. The method includes recycling the third portion of the combined effluent stream to the first and second adiabatic fixed bed reactors. The method includes separating the mixed intermediate product stream to form a stream primarily comprising MTBE, a stream primarily comprising methanol, and a C4 raffinate stream.

[0010] Embodiments of the present invention include a method for producing methyl tert-butyl ether. The method includes mixing a crude C4 stream containing isobutylene with methanol to form a feed stream. The method includes splitting the feed stream to form a first feed stream and a second feed stream. The method includes feeding the first feed stream to a first adiabatic fixed-bed reactor and feeding the second feed stream to a second adiabatic fixed-bed reactor. The method includes subjecting the isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in the first and second adiabatic fixed-bed reactors, respectively, to produce a first portion of MTBE in an effluent from the first adiabatic fixed-bed reactor and in an effluent from the second adiabatic fixed-bed reactor. The method includes combining the effluent from the first adiabatic fixed-bed reactor and the effluent from the second adiabatic fixed-bed reactor to form a stream comprising MTBE, water, and isobutylene. The method includes separating water from the stream comprising MTBE, water, and isobutylene to form a combined reactor effluent stream. The method includes reacting isobutylene contained in a first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first and second adiabatic fixed bed reactors to produce a third adiabatic fixed bed reactor effluent stream containing a second portion of MTBE. The method includes mixing the second portion of the combined reactor effluent stream with the third adiabatic fixed bed reactor effluent stream to form a mixed intermediate product stream. The method includes recycling the third portion of the combined effluent stream to the first and second adiabatic fixed bed reactors. The method also includes separating the mixed intermediate product stream to form a stream primarily comprising MTBE, a stream primarily comprising methanol, and a C4 raffinate stream.

[0011] The following include definitions of various terms and expressions used throughout this specification.

[0012] The term "about" or "approximately" is defined as approximate to what one of ordinary skill in the art understands. In a non-limiting embodiment, these terms are defined as within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0013] The terms "wt %," "volume %," or "mole %" refer to the weight, volume, or mole percentage, respectively, of a component based on the total weight, total volume, or total moles of the material in which it is contained. In a non-limiting example, 10 moles of a component out of 100 moles of a material is 10 mole % of the component.

[0014] The term "substantially" and variations thereof are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0015] 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.

[0016] The term "effective" as used in this specification and / or claims means sufficient to achieve a desired, expected, or intended result.

[0017] In the claims or description, when used with “comprises,” “includes,” “contains,” or “has,” the use of “a” or “an” may mean “one,” but also has the meaning of “one or more,” “at least one,” or “one or more than one.”

[0018] The words “comprising,” “having,” “including,” or “containing” are inclusive or open-ended and do not exclude other unlisted elements or method steps.

[0019] The methods of the present invention may "comprise," "consist essentially of," or "consist of" particular ingredients, components, compositions, etc. disclosed throughout the specification.

[0020] As used in this specification and / or claims, the term "predominantly" means greater than any of 50% by weight, 50% by mole, and 50% by volume. For example, "predominantly" may include 50.1% by weight to 100% by weight and all values ​​and ranges therebetween, 50.1% by mole to 100% by mole and all values ​​and ranges therebetween, or 50.1% by volume to 100% by volume and all values ​​and ranges therebetween.

[0021] Other objects, features and advantages of the present invention can be more clearly seen from the following drawings, detailed descriptions and examples. However, it should be understood that although the drawings, detailed descriptions and examples indicate specific embodiments of the present invention, they are only given by way of illustration and are not meant to be limiting. In addition, it is expected that those skilled in the art can more clearly see the changes and modifications within the spirit and scope of the present invention based on this detailed description. In further embodiments, features from specific embodiments can be combined with features from other embodiments. For example, features from one embodiment can be combined with features from any other embodiment. In further embodiments, the specific embodiments described herein can add additional features.

[0022] Brief Description of the Drawings

[0023] For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1is a schematic diagram showing a system for producing MTBE according to an embodiment of the present invention;

[0025] Figure 2 is a schematic flow diagram showing a process for producing MTBE according to an embodiment of the present invention;

[0026] Figure 3A shows the correlation between isobutylene conversion and run time for an MTBE production process when the reactor is operated with and without recycling a portion of the MTBE product back to the reactor;

[0027] Figure 3B shows the correlation between MTBE selectivity and run time for an MTBE production process when the reactor is operated with and without recycling a portion of the MTBE product back to the reactor;

[0028] Figure 4 The correlation between the isobutylene conversion and the operating time of the MTBE production process is shown at different MTBE concentrations in the feed stream to the MTBE synthesis reactor. DETAILED DESCRIPTION

[0029] Currently, MTBE can be produced by reacting isobutylene with methanol in an MTBE reactor and then further performing the MTBE synthesis reaction in a catalytic distillation column or a reactive distillation column. Other MTBE systems use a super fractionator to separate the light ends (C4 and methanol) from the MTBE. As a result, the production capital expenditure and operating costs of MTBE are high, resulting in a high production cost of MTBE. The present invention provides a solution to this problem. The solution is based on a system and method for producing MTBE, including reacting isobutylene and methanol in a first reactor and a second reactor operated in parallel. At least a portion of the combined effluent stream from the first reactor and the second reactor is further subjected to reaction conditions in a third reactor connected in series with the first reactor and the second reactor for producing additional MTBE. The disclosed method and system do not require the operation of a catalytic distillation column, a reactive distillation column, a super fractionator, or an isothermal reactor, reducing capital expenditure and / or operating costs compared to conventional MTBE production systems. These and other non-limiting aspects of the present invention are further discussed in the following sections.

[0030] A. System for producing MTBE

[0031] In an embodiment of the present invention, a system for producing MTBE includes a primary reaction unit operating with a secondary reaction unit. The primary reaction unit may include two reactors operating in parallel. The secondary reaction unit may include a third reactor connected in series with the primary reaction unit. Figure 1, schematically shown is a system 100 configured to produce MTBE from isobutylene and methanol.

[0032] According to an embodiment of the present invention, system 100 includes a primary reaction unit 101, which is configured to react methanol and isobutylene to produce MTBE. In an embodiment of the present invention, primary reaction unit 101 includes a first reactor 111 and a second reactor 112. The first reactor 111 and the second reactor 112 can be operated in parallel. In an embodiment of the present invention, the isobutylene flowing into primary reaction unit 101 comes from a crude C4 stream 11. The methanol flowing into primary reaction unit 101 can come from a crude methanol stream 12. The crude C4 stream 11 can contain isobutylene, 1-butene, 2-butene, n-butane, isobutane, 1,3-butadiene, or a combination thereof. In system 100, the crude C4 stream 11 and the first methanol stream 12 can be combined to form a combined feed stream 13. The combined feed stream 13 can flow into the first reactor 111 and the second reactor 112. In an embodiment of the present invention, system 100 may optionally include a feed preheater configured to heat the combined feed stream 13 to a predetermined feed temperature. The predetermined feed temperature may be in the range of 37°C to 47°C, preferably at 42°C.

[0033] The first reactor 111 and the second reactor 112 can each individually include an adiabatic fixed bed reactor. In an embodiment of the present invention, the first reactor 111 and the second reactor 112 each independently include a downflow reactor. The first reactor 111 and the second reactor 112 can each include a catalyst. The catalyst can be a strongly acidic resin, including a resin based on polystyrene, a resin based on polystyrene divinylbenzene, a sulfonic acid resin, a macroreticular resin, an acidic ion exchange resin, a sulfonated macroporous resin or any combination thereof. In an embodiment of the present invention, the first reactor 111 and / or the second reactor 112 may include a catalyst support grid (such as a Johnson screen), which is configured to provide support to the catalyst and minimize the catalyst residue in the effluent. In an embodiment of the present invention, the effluent from the first reactor 111 and the effluent from the second reactor 112 merge to form a combined stream 14. The combined stream 14 may include MTBE and unreacted isobutylene. Combined stream 14 may also include water, methanol, 1-butene, methyl sec-butyl ether (MSBE), 2,4,4-trimethyl-1-pentene (244TM1P), 2,4,4-trimethyl-2-pentene (244TM2P), isobutane, n-butane, 1,3-butadiene, cis-2-butene, trans-2-butene, 1,3-cyclopentadiene (CD13), 1,3-pentadiene (14PD), or any combination thereof. In an embodiment of the present invention, system 100 may include an aftercooler configured to cool the effluent from first reactor 111 and / or the effluent from second reactor 112 before forming combined stream 14.

[0034] According to an embodiment of the present invention, the outlet of the primary reaction unit 101, including the outlet of the first reactor 111 and the outlet of the second reactor 112, is in fluid communication with the splitter feed tank 113, so that the combined stream 14 flows from the primary reaction unit 101 to the splitter feed tank 113. In an embodiment of the present invention, the splitter feed tank 113 is configured to remove at least some water from the combined stream 14 to form a combined reactor effluent stream 15 comprising MTBE and unreacted isobutylene. The splitter feed tank 113 can be further configured to control the pressure and / or vapor content in the primary reaction unit 101. In an embodiment of the present invention, the splitter feed tank 113 can include a nitrogen blanket configured to control the pressure therein. In an embodiment of the present invention, the combined reactor effluent stream 15 can be split to form a first portion 16, a second portion 17, and / or a third portion 18.

[0035] In an embodiment of the present invention, the outlet of the splitter feed tank 113 may be in fluid communication with the inlet of the third reactor 103, such that the first portion 16 of the combined reactor effluent stream 15 flows from the splitter feed tank 113 to the third reactor 103. The first portion 16 of the combined reactor effluent stream 15 may be combined with the second methanol stream 19 to form a second feed stream 20 for the third reactor 103. In an embodiment of the present invention, the third reactor 103 is configured to react unreacted isobutylene with the methanol of the second feed stream 20 to produce MTBE in the third reactor effluent stream 21. The third reactor 103 may comprise an adiabatic fixed bed reactor. The adiabatic fixed bed reactor may be a downflow reactor. In an embodiment of the present invention, the third reactor 103 may comprise a strong acid catalyst comprising a polystyrene-based resin, a polystyrene divinylbenzene-based resin, a sulfonic acid resin, a macroporous resin, an acidic ion exchange resin, a sulfonated macroporous resin, or any combination thereof. The strong acid catalyst may comprise a sulfonated polystyrene cross-linked resin. Sulfonated polystyrene cross-linking resin catalyst can be Amberlyst from DUPONT (USA) TM Catalysts, including Amberlyst TM 15(A-15), Amberlyst TM 35(A-35), Amberlyst TM 36(A-36), Amberlyst TM 40(A-40), Amberlyst TM 48 (A-48) or a combination thereof. Additional examples of sulfonated polystyrene crosslinked resins may include CT-175, CT-252, CT-275 and a combination thereof (U.S. ).

[0036] In an embodiment of the present invention, the outlet of the splitter feed tank 113 may be in fluid communication with the inlet of the primary reaction unit 101, such that the third portion 18 of the combined reactor effluent stream 15 flows from the splitter feed tank 113 to the primary reaction unit 101. The third portion 18 of the combined reactor effluent stream 15 may be combined with the combined feed stream 13 before flowing into the primary reaction unit 101.

[0037] According to an embodiment of the present invention, the second portion 17 of the combined reactor effluent stream 15 and the third reactor effluent stream 21 can be combined to form a mixed intermediate product stream 22. In an embodiment of the present invention, the system 100 includes a separation column 114 configured to separate the mixed intermediate product stream 22 to form (1) an overhead stream 23 comprising methanol, C4 hydrocarbons, and waste and (2) a product stream 24 primarily comprising MTBE. In an embodiment of the present invention, the separation column 114 may include a distillation column. The separation column 114 may not include a super fractionator. In an embodiment of the present invention, the separation column 114 may include a feed filter configured to filter the mixed intermediate product stream 22 before it flows into the separation column 114. The separation column 114 may further include a heat exchanger configured to use the product stream 24 as a heating medium to heat the mixed intermediate product stream 22 before it flows into the separation column 114. In an embodiment of the present invention, the separation column 114 is configured to utilize medium-pressure steam as the heating medium for its reboiler. In an embodiment of the present invention, the reboiler of the separation column 114 may include a vertical thermosyphon heat exchanger and a reboiler desuperheater configured to desuperheat the intermediate pressure steam before entering the reboiler.

[0038] According to an embodiment of the present invention, the outlet of the separation column 114 is fluidically connected to the methanol scrubber 115, so that the overhead stream 23 flows from the separation column 114 to the methanol scrubber 115. In an embodiment of the present invention, the methanol scrubber 115 is configured to separate the overhead stream 23 to generate a recycled methanol stream 25 mainly comprising methanol, a C4 raffinate stream 26 mainly comprising C4 hydrocarbons, and a waste stream 27. The waste stream 27 can be further treated in a carbon bed to remove total organic carbon (TOC) before being discharged. In an embodiment of the present invention, the methanol scrubber 115 may include a raffinate scrubber and a methanol concentrator. The raffinate scrubber may be configured to extract methanol from the overhead stream 23 using a countercurrent water flow. The methanol concentrator is configured to separate the wash water from the methanol in the bottom stream of the raffinate scrubber. The methanol concentrator may include trays and downcomers. In an embodiment of the present invention, the bottom stream of the methanol concentrator may be pumped back to the raffinate scrubber to compensate for the water loss with some fresh condensate. The overhead stream of the methanol concentration column may be recycled as part of the methanol feed to the system 100 .

[0039] B. Methods for producing MTBE

[0040] A process has been discovered for producing MTBE from isobutylene and methanol at a lower cost than conventional processes. Figure 2 As shown, an embodiment of the present invention includes a process 200 for producing methyl tertiary butyl ether (MTBE). Figure 1 As shown and described above, method 200 may be implemented by system 100 .

[0041] According to an embodiment of the present invention, as shown in block 201, method 200 includes feeding isobutylene and methanol to a first reactor 111 and a second reactor 112 arranged in parallel. In an embodiment of the present invention, at block 201, the isobutylene is supplied from a crude C4 stream 11 comprising isobutylene, 1-butene, 2-butene, n-butane, isobutane, 1,3-butadiene, or a combination thereof. The crude C4 stream 11 may be derived from a C4 raffinate from a steam cracker or a fluid catalytic cracker. In an embodiment of the present invention, the crude C4 stream may comprise 10-40 wt% isobutylene. The first methanol stream may comprise 98-99.9 wt% methanol.

[0042] In an embodiment of the present invention, the feeding at box 201 may include mixing the crude C4 stream 11 with the first methanol stream 12 to form a combined feed stream 13. The mixing at box 201 may be performed at a molar ratio of the first methanol stream to the isobutylene in the crude C4 stream of 1-1.3 and all ranges and values ​​therebetween, including the ranges of 1-1.1, 1.1-1.2, and 1.2-1.3. The combined feed stream 13 may contain an excess of methanol suitable for breaking the azeotropic limit in the overhead of the separation column 114. The feeding at box 201 may further include optionally heating the combined feed stream 13 to a predetermined temperature. The predetermined temperature may be in the range of 35-47°C, preferably about 42°C, and all ranges and values ​​therebetween, including the ranges of 35-37°C, 37-39°C, 39-41°C, 41-43°C, 43-45°C, and 45-47°C. In an embodiment of the present invention, the feeding at block 201 may further include splitting the combined feed stream 13 to generate a first feed stream and a second feed stream. According to an embodiment of the present invention, the feeding at block 201 may further include feeding the first feed stream to the first reactor 111 and feeding the second feed stream to the second reactor 112.

[0043] According to an embodiment of the present invention, as shown at block 202, method 200 includes subjecting isobutylene and methanol to reaction conditions in first reactor 111 and second reactor 112, respectively, sufficient to react the isobutylene with the methanol to produce a first portion of MTBE in the effluent from first reactor 111 and in the effluent from second reactor 112. In an embodiment of the present invention, the reaction conditions in first reactor 111 and / or second reactor 112 include a reaction temperature of 40° C. to 60° C. and all ranges and values ​​therebetween, including ranges of 40° C. to 42° C., 42° C. to 44° C., 44° C. to 46° C., 46° C. to 48° C., 48° C. to 50° C., 50° C. to 52° C., 52° C. to 54° C., 54° C. to 56° C., 56° C. to 58° C., and 58° C. to 60° C. The reaction conditions in the first reactor 111 and / or the second reactor 112 may include an operating pressure of 6-10 bar and all ranges and values ​​therebetween, including the ranges of 6-6.5 bar, 6.5-7.0 bar, 7.0-7.5 bar, 7.5-8.0 bar, 8.0-8.5 bar, 8.5-9.0 bar, 9.0-9.5 bar, 9.5-10 bar. In an embodiment of the present invention, the reaction conditions in the first reactor 111 and / or the second reactor 112 include 3 to 8 hours. -1 Weight hourly space velocity in the range and all ranges and values ​​therebetween, including 3-4h -1 4-5h -1 5-6h -1 , 6-7h -1 and 7-8h -1 According to an embodiment of the present invention, the effluent from the first reactor 111 and / or the effluent from the second reactor 112 contains 16-56 wt% MTBE and 0-4 wt% unreacted isobutylene. The effluent from the first reactor 111 and / or the effluent from the second reactor 112 may contain 60-90 wt% of C4 hydrocarbons other than isobutylene. In an embodiment of the present invention, the first reactor 111 and / or the second reactor 112 are operated so that the primary reaction unit 101 achieves an isobutylene conversion rate of 94%.

[0044] According to an embodiment of the present invention, as shown in block 203, method 200 includes combining the effluent from first reactor 111 and the effluent from second reactor 112 to form a combined reactor effluent stream 15 comprising MTBE and unreacted isobutylene. In an embodiment of the present invention, the effluent from first reactor 111 and / or the effluent from second reactor 112 comprises water, and the combining step at block 203 includes combining the effluent stream from first reactor 111 and the effluent from second reactor 112 to form a combined stream 14 comprising MTBE, water, and isobutylene, and separating the water from the combined stream 14 comprising MTBE, water, and isobutylene in a splitter feed tank 113 to form a combined reactor effluent stream 15. The splitter feed tank can be operated at a temperature of 50-55° C. and a pressure of 4-6 bar.

[0045] According to an embodiment of the present invention, as shown in block 204, the method 200 includes reacting the isobutylene of the first portion 16 of the combined reactor effluent stream with the methanol of the second methanol stream 16 in a third reactor 103 connected in series with the first reactor 111 and the second reactor 112 to produce a third reactor effluent stream 21 comprising a second portion of MTBE. At block 204, the third reactor 103 can be operated at an operating temperature of 40-65°C and all ranges and values ​​therebetween, including the ranges of 40-45°C, 45-50°C, 50-55°C, 55-60°C, and 60-65°C. At block 204, the third reactor 103 can be operated at an operating pressure of 6-10 bar and all ranges and values ​​therebetween, including the ranges of 6-7 bar, 7-8 bar, 8-9 bar, and 9-10 bar. At block 204, the third reactor 103 can be operated at an operating pressure of 3-8 hours. -1 and all ranges and values ​​of weight hourly space velocity therebetween, including 3-4h -1 4-5h -1 5-6h -1 , 6-7h -1 and 7-8h -1In an embodiment of the present invention, the third reactor effluent stream 21 comprises 16-56 wt% MTBE and all ranges and values ​​therebetween, including 16-20 wt%, 20-24 wt%, 24-28 wt%, 28-32 wt%, 32-36 wt%, 36-40 wt%, 40-44 wt%, 44-48 wt%, 48-52 wt%, and 52-56 wt%. In an embodiment of the present invention, the third reactor 103 is operated to convert approximately 6% more isobutylene from the first portion 16 of the combined reactor effluent stream 15. In an embodiment of the present invention, an overall conversion of isobutylene of 97% to 100% can be achieved at block 204. In an embodiment of the present invention, the first reactor 111, the second reactor 112, and the third reactor 103 can be operated under substantially the same or different operating conditions, including operating temperature, operating pressure, weight hourly space velocity, or any combination thereof. In an embodiment of the present invention, the third portion 18 of the combined reactor effluent stream 15 may be cooled to a predetermined temperature before it flows into the third reactor 103. The predetermined temperature of the third portion 18 of the combined reactor effluent stream 15 may be about 45° C. In an embodiment of the present invention, at least some of the fresh crude C4 stream comprising isobutylene is added to the first portion 16 of the combined reactor effluent stream 15 before it flows into the third reactor 103.

[0046] According to an embodiment of the present invention, as shown at block 205, the method 200 includes mixing the second portion 17 of the combined reactor effluent stream 15 with the third reactor effluent stream 21 to form a mixed intermediate product stream 22. According to an embodiment of the present invention, as shown at block 206, the method 200 includes recycling the third portion 18 of the combined reactor effluent stream 15 to the first reactor 111, the second reactor 112, and / or the third reactor 103. The volume ratio between the third portion 18 of the combined reactor effluent stream 15 and the combined feed stream 13 can be in the range of 2-4 (i.e., a recycle / fresh feed ratio of 2-4). At block 206, the third portion 18 of the combined effluent stream 15 can be combined with the combined feed stream 13 before flowing into the first reactor 111 and / or the second reactor 112. The volume ratio of the third portion 18 flowing into the first reactor 111 and the second reactor 112 to the combined feed stream 13 can be about 2.5.

[0047] According to an embodiment of the present invention, as shown in block 207, method 200 includes separating mixed intermediate product stream 22 to form a product stream 24 comprising primarily MTBE, a recycled methanol stream 25 comprising primarily methanol, and a C4 raffinate stream 26 comprising primarily C4 hydrocarbons. Product stream 24 may comprise at least 98 wt% MTBE. In an embodiment of the present invention, the separation at block 207 may include separating mixed intermediate product stream 22 in a separation column 114 to generate an overhead stream 23 comprising methanol and C4 hydrocarbons and a product stream 24 comprising primarily MTBE. Separation column 114 may be operated at a top temperature in the range of 45-60°C and a bottom (or reboiler) temperature in the range of 135-150°C. Separation column 114 may be operated at an operating pressure of 7-8 bar. The separation at box 207 may further include treating the overhead stream 23 in a methanol scrubber 115 to generate a recycled methanol stream 25, a C4 raffinate stream 26, and / or a waste stream 27 comprising wastewater having TOC (total organic carbon). The processing steps in the methanol scrubber 115 may further generate residual methanol, which is recycled to the primary reaction unit 101 and / or the third reactor 103. In an embodiment of the present invention, the raffinate scrubber of the methanol scrubber 115 may be operated at a temperature of 40-45°C and a pressure of 13-15 bar. The methanol concentration column of the methanol scrubber 115 may be operated at a temperature of 80-135°C and an operating pressure of 2-3 bar. In an embodiment of the present invention, the product stream 24 may be cooled in a heat exchanger and / or a product cooler of the separation column 114 to reach the boundary temperature.

[0048] According to an embodiment of the present invention, the presence of MTBE in the feed stream entering the MTBE synthesis reaction unit (e.g., the first reactor 111, the second reactor 112, and / or the third reactor 113) increases the isobutylene conversion rate for MTBE production compared to the absence of MTBE in the feed stream entering the MTBE synthesis reaction unit. In an embodiment of the present invention, the isobutylene conversion rate increases with an increase in the MTBE concentration in the feed stream entering the MTBE synthesis reaction unit. The increase in the isobutylene conversion rate may be due to the effect of MTBE on the catalyst activity, which is caused by structural changes in the catalyst and the optimization of the exothermic properties of the MTBE synthesis reaction. In an embodiment of the present invention, the isobutylene conversion rate and the MTBE concentration in the feed stream entering the MTBE synthesis reaction unit may have a substantially linear correlation.

[0049] Although referenced Figure 2 The blocks of FIG. 1 describe embodiments of the present invention, but it should be understood that the operation of the present invention is not limited to Figure 2 Therefore, embodiments of the present invention may be implemented in different Figure 2 Various blocks are used in an ordered sequence to provide the functionality described herein.

[0050] The systems and processes described herein may also include various devices not shown but known to those skilled in the art of chemical processing, such as controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and similar devices that may not be shown.

[0051] As a part of the disclosure of the present invention, specific examples are included below. These examples are only for illustrative purposes and are not intended to limit the present invention. Those of ordinary skill in the art will readily recognize that parameters that can be changed or modified to produce substantially the same results.

[0052] Example 1

[0053] (Material Balance of MTBE Production System)

[0054] Simulations were conducted using the Pro II platform used for MTBE production in the aforementioned system. As described above, a first methanol stream at approximately 46°C and a C4 raffinate stream at 40°C were fed to the system. The system did not include a catalytic distillation column, reactive distillation column, or superfractionator. The resulting compositions of the process and product streams are shown in Table 1.

[0055] Table 1: Material balance of MTBE production system

[0056]

[0057] The results demonstrate that the system is capable of producing an MTBE product stream comprising greater than 98 wt% MTBE without the use of a catalytic (reactive) distillation column and a super fractionator.

[0058] Example 2

[0059] (Effect of MTBE Recycling on Isobutylene Conversion)

[0060] Experiments were conducted to investigate the effect of MTBE recycle flow on isobutylene conversion and MTBE selectivity in an MTBE synthesis reactor. The reaction conditions used in the experiments included a reaction temperature of 60 °C, a weight hourly space velocity of 72.49 h -1 The C4 raffinate feed was fed into the reactor at a flow rate of 53.8 ml / h. Methanol was fed into the reactor at a flow rate of 0.1 to achieve an isobutylene to methanol molar ratio of about 1:1. About 0.50 g of catalyst was used in the reactor. The correlation between the isobutylene conversion (%) and the run time (reaction time, h) for the reactors operated with and without MTB recycle is shown in Figure 3A The correlation between MTBE selectivity (%) and run time (reaction time, h) for reactors operated with and without MTBE recycle is shown in Figure 3B .

[0061] Results show that an MTBE production process that recycles a portion of the MTBE product stream back to the reactor exhibits an approximately 83% improvement in isobutylene conversion compared to an MTBE production process that does not utilize an MTBE recycle stream. This is attributed to the effect of MTBE on catalyst activity, resulting from structural changes in the catalyst and optimization of the exothermic nature of the MTBE synthesis reaction. However, no difference in MTBE selectivity was observed between the MTBE production process that recycles a portion of the MTBE product stream back to the reactor and the MTBE production process that does not utilize an MTBE recycle stream.

[0062] Example 3

[0063] (Effect of MTBE Concentration in MTBE Feed Stream on Isobutylene Conversion)

[0064] The PRO II platform was used to simulate the composition of the feed stream flowing into the MTBE synthesis reactor. The composition of the feed stream flowing into the MTBE synthesis reactor is shown in Table 2. Experiments were then carried out using the feed stream composition obtained by simulation. For the experiments, the amount of catalyst (A-15) used was approximately 0.5 g. The reaction temperature for MTBE synthesis was 60°C, and the weight hourly space velocity for the MTBE synthesis experiment was approximately 73 h -1 The molar ratio of methanol to isobutylene fed to the system was 1:1. The results of MTBE conversion relative to run time (h) for each feed stream composition are shown in Figure 4 A and Table 3.

[0065] Table 2: Composition of feed streams into the primary reactor for MTBE synthesis

[0066]

[0067] Table 3: Isobutylene conversion at various MTBE concentrations in the feed stream

[0068]

[0069] Figure 4 The results show that the isobutylene conversion increases with increasing MTBE concentration in the feed stream. The results of Table 3 were also analyzed by linear regression. The results show that the isobutylene conversion (y) can be described by the MTBE concentration in the feed stream (x; wt %) as y = 0.5441x + 31.706 (R 2 =0.9854). This is due to the effect of MTBE on the catalyst activity, which is caused by the structural change of the catalyst and the optimization of the exothermic properties of the MTBE synthesis reaction.

[0070] In the context of the present invention, at least the following 18 embodiments are described. Embodiment 1 is a method for producing methyl tert-butyl ether (MTBE). The method includes feeding isobutylene and methanol to a first reactor and a second reactor arranged in parallel, subjecting the isobutylene and methanol in the first reactor and the second reactor, respectively, to reaction conditions sufficient to react the isobutylene with the methanol to produce a first portion of MTBE in the effluent from the first reactor and in the effluent from the second reactor. The method further includes combining the effluent from the first reactor and the effluent from the second reactor to form a combined reactor effluent stream, wherein the combined reactor effluent stream also contains isobutylene. The method further includes reacting the isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third reactor connected in series with the first reactor and the second reactor to produce a third reactor effluent stream containing a second portion of MTBE. The method also includes mixing a second portion of the combined reactor effluent stream with the third reactor effluent stream to form a mixed intermediate product stream, and recycling a third portion of the combined effluent stream to the first reactor and the second reactor. In addition, the method includes separating the mixed intermediate product stream to form a product stream mainly containing MTBE, a stream mainly containing methanol, and a C4 raffinate stream. Embodiment 2 is the method of embodiment 1, wherein the first reactor, the second reactor and / or the third reactor each individually include an adiabatic fixed bed reactor. Embodiment 3 is the method of any one of embodiments 1 or 2, wherein the step of feeding isobutylene and methanol to the first reactor and the second reactor includes mixing a crude C4 stream containing isobutylene with methanol to form a feed stream, and dividing the feed stream into a first feed stream and a second feed stream. The method further includes feeding the first feed stream to the first reactor and feeding the second feed stream to the second reactor. Embodiment 4 is the method of any one of embodiments 1 to 3, wherein the first reactor effluent stream and the second reactor effluent stream also contain the effluent from the first reactor and the effluent from the second reactor to form a stream containing MTBE, water, and isobutylene. The method further comprises separating water from the stream comprising MTBE, water, and isobutylene to form the combined reactor effluent stream. Embodiment 5 is the method of any one of Embodiments 1 to 4, wherein the first reactor and / or the second reactor each individually comprises a downflow reactor. Embodiment 6 is the method of any one of Embodiments 1 to 5, wherein the method does not comprise a separation step utilizing a superfractionator or a catalytic distillation column. Embodiment 7 is the method of any one of Embodiments 1 to 6, wherein the product stream contains at least 98 weight percent MTBE. Embodiment 8 is the method of any one of Embodiments 1 to 7, wherein the third reactor operates at a higher pressure than the first and second reactors.Embodiment 9 is the method of any one of embodiments 1 to 8, wherein the first reactor and the second reactor each comprise a catalyst comprising a polystyrene-based resin, a polystyrene divinylbenzene-based resin, a sulfonic acid resin, a macroreticular resin, an acidic ion exchange resin, a sulfonated macroporous resin, or any combination thereof. Embodiment 10 is the method of any one of embodiments 1 to 9, wherein the first reactor and the second reactor each operate at an operating temperature in the range of 40-60° C. Embodiment 11 is the method of any one of embodiments 1 to 10, wherein the first reactor and the second reactor each operate at an operating pressure in the range of 6-10 bar. Embodiment 12 is the method of any one of embodiments 1 to 11, wherein the effluent from the first reactor and the effluent from the second reactor each contain 16-56 wt % MTBE and 0-4 wt % isobutylene. Embodiment 13 is the method of any one of embodiments 1 to 12, wherein the effluent from the third reactor contains 0-1 wt % isobutylene. Embodiment 14 is the process of any one of embodiments 1 to 13, wherein the third reactor is operated at an operating temperature in the range of 40-65° C. Embodiment 15 is the process of any one of embodiments 1 to 14, wherein the third reactor is operated at an operating pressure in the range of 61-10 bar. Embodiment 16 is the process of any one of embodiments 1 to 15, wherein the MTBE in the first portion of the combined reactor effluent stream flowing into the third reactor and / or the MTBE in the third portion of the combined effluent stream flowing into the first and second reactors is capable of increasing the isobutylene conversion of the MTBE synthesis.

[0071] Embodiment 17 is a method for producing methyl tert-butyl ether (MTBE). The method includes mixing a crude C4 stream containing isobutylene with methanol to form a feed stream, and dividing the feed stream into a first feed stream and a second feed stream. The method also includes feeding the first feed stream to a first adiabatic fixed bed reactor and feeding the second feed stream to a second adiabatic fixed bed reactor. The method further includes subjecting the isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to generate a first portion of MTBE in the effluent from the first adiabatic fixed bed reactor and in the effluent from the second adiabatic fixed bed reactor. The method also includes combining the effluent from the first adiabatic fixed bed reactor and the effluent from the second adiabatic fixed bed reactor to form a combined reactor effluent stream, wherein the combined reactor effluent stream also contains isobutylene. In addition, the method includes reacting isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first and second adiabatic fixed bed reactors to produce a third adiabatic fixed bed reactor effluent stream containing a second portion of MTBE. The method also includes combining the second portion of the combined reactor effluent stream and the third adiabatic fixed bed reactor effluent stream to form a mixed intermediate product stream, recycling the third portion of the combined effluent stream to the first and second adiabatic fixed bed reactors, and separating the mixed intermediate product stream to form a stream primarily containing MTBE, a stream primarily containing methanol, and a C4 raffinate stream.

[0072] Embodiment 18 is a method for producing methyl tert-butyl ether (MTBE). The method includes mixing a crude C4 stream containing isobutylene and methanol to form a feed stream, and separating the feed stream into a first feed stream and a second feed stream. The method further includes feeding the first feed stream to a first adiabatic fixed bed reactor and feeding the second feed stream to a second adiabatic fixed bed reactor, and subjecting the isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to produce a first portion of MTBE in the effluent from the first adiabatic fixed bed reactor and in the effluent from the second adiabatic fixed bed reactor. The method further includes combining the effluent from the first adiabatic fixed bed reactor and the effluent from the second adiabatic fixed bed reactor to form a stream containing MTBE, water, and isobutylene, and separating water from the stream containing MTBE, water, and isobutylene to form a combined reactor effluent stream. The method further includes reacting isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first and second adiabatic fixed bed reactors to produce a third adiabatic fixed bed reactor effluent stream containing a second portion of MTBE. Furthermore, the method includes combining the second portion of the combined reactor effluent stream with the third adiabatic fixed bed reactor effluent stream to form a mixed intermediate product stream, recycling the third portion of the combined effluent stream to the first and second adiabatic fixed bed reactors, and separating the mixed intermediate product stream to form a stream primarily containing MTBE, a stream primarily containing methanol, and a C4 raffinate stream.

[0073] Although the embodiments of the present application and their advantages have been described in detail, it will be understood that various changes, substitutions and adjustments may be made herein without departing from the spirit 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, compositions, tools, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the foregoing disclosure, currently existing or later developed processes, machines, manufactures, compositions, copolymers, methods or steps that perform substantially the same function or achieve substantially the same results as the corresponding embodiments herein may be utilized. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions, tools, methods or steps within the scope of these claims.

Claims

1. A method for producing methyl tert-butyl ether (MTBE), the method comprising: feeding isobutylene and methanol into a first reactor and a second reactor arranged in parallel; subjecting isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in a first reactor and a second reactor, respectively, to produce a first portion of MTBE in an effluent from the first reactor and in an effluent from the second reactor; combining the effluent from the first reactor and the effluent from the second reactor to form a stream, wherein the stream further comprises isobutylene and water; separating water from the stream to produce separated water and a combined reactor effluent stream comprising a first portion of MTBE and isobutylene; reacting isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third reactor connected in series with the first and second reactors to produce a third reactor effluent stream comprising a second portion of MTBE; combining a second portion of the combined reactor effluent stream with the third reactor effluent stream to form a combined intermediate product stream; recycling a third portion of the combined effluent stream to the first reactor and the second reactor; separating the mixed intermediate product stream to form a product stream comprising primarily MTBE, a stream comprising primarily methanol, and a C4 raffinate stream, The method does not include a separation step using a super fractionation column or a catalytic distillation column.

2. The process of claim 1, wherein the first reactor, the second reactor and / or the third reactor each individually comprise an adiabatic fixed bed reactor.

3. The process according to any one of claims 1 and 2, wherein the step of feeding isobutylene and methanol to the first reactor and the second reactor comprises: mixing a crude C4 stream comprising isobutylene with methanol to form a feed stream; dividing the feed stream into a first feed stream and a second feed stream; The first feed stream is fed to the first reactor and the second feed stream is fed to the second reactor.

4. The process according to any one of claims 1 and 2, wherein the first reactor effluent stream and the second reactor effluent stream comprise the water.

5. The process according to any one of claims 1 and 2, wherein the first reactor and / or the second reactor each individually comprises a downflow reactor.

6. The process according to any one of claims 1 and 2, wherein the product stream comprises at least 98% by weight of MTBE.

7. The process according to any one of claims 1 and 2, wherein the third reactor is operated at a higher pressure than the first and second reactors.

8. The process of any one of claims 1 and 2, wherein the first reactor and the second reactor each contain a catalyst comprising a polystyrene-based resin, a polystyrene divinylbenzene-based resin, a sulfonic acid resin, a macroreticular resin, an acidic ion exchange resin, a sulfonated macroporous resin, or any combination thereof.

9. The process according to any one of claims 1 and 2, wherein the first reactor and the second reactor are each operated at an operating temperature in the range of 40-60°C.

10. The process according to any one of claims 1 and 2, wherein the first reactor and the second reactor are each operated at an operating pressure in the range of 6-10 bar.

11. The process according to any one of claims 1 and 2, wherein the effluent from the first reactor and the effluent from the second reactor each contain 16-56% by weight of MTBE and 0-4% by weight of isobutene.

12. The process according to any one of claims 1 and 2, wherein the effluent from the third reactor comprises 0-1 wt% of isobutene.

13. The process according to any one of claims 1 and 2, wherein the third reactor is operated at an operating temperature in the range of 40-65°C.

14. The process according to any one of claims 1 and 2, wherein the third reactor is operated at an operating pressure in the range of 6-10 bar.

15. The process according to any one of claims 1 and 2, wherein the MTBE in the first part of the combined reactor effluent stream flowing into the third reactor and / or the MTBE in the third part of the combined effluent stream flowing into the first and second reactors is capable of increasing the isobutylene conversion in the MTBE synthesis.

16. A method for producing methyl tert-butyl ether (MTBE), the method comprising: mixing a crude C4 stream comprising isobutylene with methanol to form a feed stream; dividing the feed stream into a first feed stream and a second feed stream; feeding a first feed stream to a first adiabatic fixed bed reactor and feeding a second feed stream to a second adiabatic fixed bed reactor; subjecting isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in a first adiabatic fixed bed reactor and a second adiabatic fixed bed reactor, respectively, to produce a first portion of MTBE in an effluent from the first adiabatic fixed bed reactor and in an effluent from the second adiabatic fixed bed reactor; combining the effluent from the first adiabatic fixed bed reactor and the effluent from the second adiabatic fixed bed reactor to form a stream, wherein the stream further comprises isobutylene and water; separating water from the stream to produce separated water and a combined reactor effluent stream comprising a first portion of MTBE and isobutylene; reacting isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor to produce a third adiabatic fixed bed reactor effluent stream comprising a second portion of MTBE; combining a second portion of the combined reactor effluent stream with the third adiabatic fixed bed reactor effluent stream to form a combined intermediate product stream; recycling a third portion of the combined effluent stream to the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor; separating the mixed intermediate product stream to form a stream comprising primarily MTBE, a stream comprising primarily methanol, and a C4 raffinate stream, The method does not include a separation step using a super fractionation column or a catalytic distillation column.

17. A method for producing methyl tert-butyl ether (MTBE), the method comprising: mixing a crude C4 stream comprising isobutylene with methanol to form a feed stream; dividing the feed stream into a first feed stream and a second feed stream; feeding a first feed stream to a first adiabatic fixed bed reactor and feeding a second feed stream to a second adiabatic fixed bed reactor; subjecting isobutylene and methanol to reaction conditions sufficient to react the isobutylene with the methanol in a first adiabatic fixed bed reactor and a second adiabatic fixed bed reactor, respectively, to produce a first portion of MTBE in an effluent from the first adiabatic fixed bed reactor and in an effluent from the second adiabatic fixed bed reactor; combining the effluent from the first adiabatic fixed bed reactor and the effluent from the second adiabatic fixed bed reactor to form a stream comprising MTBE, water, and isobutylene; separating water from the stream comprising MTBE, water, and isobutylene to form a combined reactor effluent stream; reacting isobutylene contained in the first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor connected in series with the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor to produce a third adiabatic fixed bed reactor effluent stream comprising a second portion of MTBE; combining a second portion of the combined reactor effluent stream with the third adiabatic fixed bed reactor effluent stream to form a combined intermediate product stream; recycling a third portion of the combined effluent stream to the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor; separating the mixed intermediate product stream to form a stream comprising primarily MTBE, a stream comprising primarily methanol, and a C4 raffinate stream, The method does not include a separation step using a super fractionation column or a catalytic distillation column.

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