Patent Description:
The present invention generally relates to methods for producing methyl tert-butyl ether (MTBE). More specifically, the present invention relates to a method for producing MTBE using a reaction unit that includes two parallel MTBE synthesis reactors that are in series with a third MTBE synthesis reactor. <CIT> discloses a MTBE process with three reactors in series.

MTBE is an organic compound that is used as an additive to enhance the octane number of gasoline. Since about <NUM>, MTBE has been synthesized by etherification of isobutylene by reaction with methanol in the presence of an acidic catalyst. Isobutylene used for MTBE synthesis can be obtained from C<NUM> hydrocarbon process streams.

Conventionally, isobutylene and methanol are fed into a fixed bed reactor to produce an MTBE containing effluent. The effluent is then fed to a catalytic distillation column or a reactive distillation column to react isobutylene remaining in the effluent with additional methanol to produce more MTBE. Some other conventional processes also use super fractionator for separation of light ends (C<NUM> and methanol) from MTBE. The catalytic distillation column and/or super fractionator generally require a large amount of capital expenditure and operational costs, thereby increasing the production costs for MTBE. Other MTBE production systems use isothermal multi-tubular reactors as the MTBE synthesis reactors to eliminate the need for catalytic distillation columns or reactive distillation columns. However, the isothermal multi-tubular reactors require high capital expenditure, thus, not resolving the issues related to the high production costs for MTBE.

Overall, while systems and methods for producing MTBE exist, the need for improvements in this field persists in light of at least the aforementioned drawbacks for the conventional systems and methods.

A solution to at least the above mentioned problems associated with the systems and methods for producing MTBE from isobutylene and methanol has been discovered. The solution resides in a method for producing MTBE using a system that includes at least three MTBE synthesis reactors. Notably, the first and the second MTBE synthesis reactors are operated in parallel with the third MTBE synthesis reactor operated in series with the first and second MTBE synthesis reactors. This can be beneficial for at least increasing the MTBE concentration overall, specifically the MTBE concentration in the product effluent stream from the third MTBE synthesis reactor. Furthermore, the disclosed system does not include a super fractionator, a catalytic distillation column (reactive distillation column), or isothermal reactors, resulting in reduced capital expenditure and/or operating cost for producing MTBE, compared to conventional MTBE production systems. Overall, in the disclosed methods, an optimum volume of methanol stream required to maximize MTBE production and reduce slippage of isobutylene to minimum acceptable values together with a crude C<NUM> stream are flowed into a primary reaction unit that comprises a first reactor and a second reactor in parallel configured to produce maximum values of final MTBE volumes under higher or equal established purity commercial quality specifications levels. Therefore, the system and method of the present invention provide a technical solution to at least some of the problems associated with the conventional systems and methods for producing MTBE, as mentioned above.

The method according to the invention is defined in the claims. Embodiments of the invention include a method of producing methyl tertiary butyl ether. The method comprises feeding isobutylene and methanol to a first reactor and a second reactor, arranged in parallel. The method comprises subjecting the isobutylene and the methanol, in the first reactor and the second reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first reactor and in effluent from the second reactor. The method comprises 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 further comprises isobutylene. The method comprises reacting the isobutylene comprised in a first portion of the combined reactor effluent stream with methanol in a third reactor that is in series with the first reactor and second reactor, to produce a third reactor effluent stream comprising a second portion of MTBE. The method comprises mixing a second portion of the combined reactor effluent stream with the third reactor effluent stream to form a mixed intermediate product stream. The method comprises recycling a third portion of the combined effluent stream to the first reactor and the second reactor. The method further comprises separating the mixed intermediate product stream to form a product stream comprising primarily MTBE, a stream comprising primarily methanol, and a C<NUM> raffinate stream. In the method according to the invention , 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; splitting the feed stream into a first feed stream and a second feed stream; and
feeding the first feed stream to the first reactor and feeding the second feed stream to the second reactor. The method according to the invention does not include a separation step that utilizes super fractionator column or catalytic distillation column.

Embodiments of the invention include a method of producing methyl tertiary butyl ether. The method includes mixing a crude C<NUM> stream comprising 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 the methanol, in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first adiabatic fixed bed reactor and in 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 further comprises isobutylene. The method includes reacting the isobutylene comprised in a first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor that is in series with the first adiabatic fixed bed reactor and second adiabatic fixed bed reactor, to produce a third adiabatic fixed bed reactor effluent stream comprising a second portion of MTBE. The method includes mixing a 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 a third portion of the combined effluent stream to the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor. The method includes separating the mixed intermediate product stream to form a stream comprising primarily MTBE, a stream comprising primarily methanol, and a C<NUM> raffinate stream.

Embodiments of the invention include a method of producing methyl tertiary butyl ether. The method includes mixing a crude C<NUM> stream comprising 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 the methanol, in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first adiabatic fixed bed reactor and in effluent from the second adiabatic fixed bed reactor. The method includes combining effluent from the first adiabatic fixed bed reactor and effluent from the second adiabatic fixed bed reactor to form a stream comprising MTBE, water, isobutylene. The method includes separating water from the stream comprising MTBE, water, isobutylene to form a combined reactor effluent stream. The method includes reacting the isobutylene comprised in a first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor that is in series with the first adiabatic fixed bed reactor and second adiabatic fixed bed reactor, to produce a third adiabatic fixed bed reactor effluent stream comprising a second portion of MTBE. The method includes mixing a 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 a third portion of the combined effluent stream to the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor. The method further includes separating the mixed intermediate product stream to form a stream comprising primarily MTBE, a stream comprising primarily methanol, and a C<NUM> raffinate stream.

The terms "wt. %" or "mol. %" refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, <NUM> moles of component in <NUM> moles of the material is <NUM> mol. % of component.

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

The term "primarily," as that term is used in the specification and/or claims, means greater than any of <NUM> wt. %, <NUM> mol. %, and <NUM> vol. For example, "primarily" may include <NUM> wt. % to <NUM> wt. % and all values and ranges there between, <NUM> mol. % to <NUM> mol. % and all values and ranges there between, or <NUM> vol. % to <NUM> vol. % and all values and ranges there between.

Features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

Currently, MTBE can be produced by reacting isobutylene with methanol in an MTBE reactor followed by further MTBE synthesis reaction in a catalytic distillation column or a reactive distillation column. Other MTBE systems use super fractionator for separation of light ends (C<NUM> and methanol) from MTBE. Therefore, the capital expenditure and the operating costs for producing MTBE are relatively high, resulting in high production costs for MTBE. The present invention provides a solution to the problem. The solution is premised on a method for producing MTBE that includes reacting isobutylene and methanol in a first reactor and second reactor, which are operated in parallel. At least a portion of the combined effluent stream from the first reactor and second reactor is further subjected to reaction conditions for producing additional MTBE in a third reactor that is in series with the first reactor and the second reactor. 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, resulting in reduced capital expenditure and/or operating costs compared to conventional MTBE production systems. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

In embodiments of the system for producing MTBE according to the method of the invention, the system includes a primary reaction unit operated with a secondary reaction unit. The primary reaction unit can include two reactors operated in parallel. The second reaction unit may include a third reactor in series with the primary reaction unit. With reference to <FIG>, a schematic diagram is shown for system <NUM>, which is configured for producing MTBE using isobutylene and methanol.

According to embodiments of the system, system <NUM> comprises primary reaction unit <NUM> configured to react methanol and isobutylene to produce MTBE. In embodiments of the system, primary reaction unit <NUM> includes first reactor <NUM> and second reactor <NUM>. First reactor <NUM> and second reactor <NUM> may be operated in parallel. In embodiments of the system, isobutylene that is flowed into primary reaction unit <NUM> is from crude C<NUM> stream <NUM>. Methanol that is flowed into primary reaction unit <NUM> may be from crude methanol stream <NUM>. Crude C<NUM> stream <NUM> may comprise isobutylene, <NUM>-butene, <NUM>-butene, n-butane, isobutane, <NUM>,<NUM>-butadiene, or combinations thereof. In system <NUM>, crude C<NUM> stream <NUM> and first methanol stream <NUM> may be combined to form combined feed stream <NUM>. Combined feed stream <NUM> can be flowed into first reactor <NUM> and second reactor <NUM>. In embodiments of the system, system <NUM> can optionally include a feed preheater configured to heat combined feed stream <NUM> to a predetermined feed temperature. The predetermined feed temperature may be in a range of <NUM> to <NUM>, preferably at <NUM>.

First reactor <NUM> and second reactor <NUM> can each individually include an adiabatic fixed bed reactor. In embodiments of the system, first reactor <NUM> and second reactor <NUM> each individually include a down-flow reactor. First reactor <NUM> and second reactor <NUM> may each include a catalyst. The catalyst may be a strongly acidic resin comprising polystyrene based resin, polystyrene divinyl benzene based resin, sulfonic resin, macroreticular resin, acidic ion-exchange resin, sulphonated macroporous resin, or any combination thereof. In embodiments of the system, first reactor <NUM> and/or second reactor <NUM> may include a catalyst support grid (e.g., a Johnson screen) configured to provide support to the catalyst and minimize catalyst carry-over in the effluents. In embodiments of the system, effluent from first reactor <NUM> and effluent from second reactor <NUM> are combined to form combined stream <NUM>. Combined stream <NUM> may comprise MTBE, and unreacted isobutylene. Combined stream <NUM> may further include water, methanol, <NUM>-butene, methyl-secondary butyl ether (MSBE), <NUM>,<NUM>,<NUM>-Trimethyl-<NUM>-pentene (244TM1P), <NUM>,<NUM>,<NUM>-Trimethyl-<NUM>-pentene (244TM2P), isobutane, n-butane, <NUM>,<NUM>-butadiene, cis-<NUM>-butene, trans-<NUM>-butene, <NUM>,<NUM>-Cyclopentadiene (CD13), <NUM>,,<NUM>-Pentadiene (14PD), or any combinations thereof. In embodiments of the system, system <NUM> may include an after-cooler configured to cool the effluent from first reactor <NUM> and/or the effluent from second reactor <NUM> before forming combined stream <NUM>.

According to embodiments of the system, an outlet of primary reaction unit <NUM>, including outlets of first reactor <NUM> and second reactor <NUM>, is in fluid communication with separation column feed drum <NUM> such that combined stream <NUM> flows from primary reaction unit <NUM> to separation column feed drum <NUM>. In embodiments of the system, separation column feed drum <NUM> is configured to remove at least some water from combined stream <NUM> to form combined reactor effluent stream <NUM> comprising MTBE and unreacted isobutylene. Separation column feed drum <NUM> may be further configured to control pressure and/or vapor content in primary reaction unit <NUM>. Separation column feed drum <NUM>, in embodiments of the system, may include a nitrogen blanket configured to control pressure therein. Combined reactor effluent stream <NUM>, in embodiments of the system, can be divided to form first portion <NUM>, second portion <NUM>, and/or third portion <NUM>.

In embodiments of the system, an outlet of separation column feed drum <NUM> may be in fluid communication with an inlet of third reactor <NUM> such that first portion <NUM> of combined reactor effluent stream <NUM> flows from separation column feed drum <NUM> to third reactor <NUM>. First portion <NUM> of combined reactor effluent stream <NUM> may be combined with second methanol stream <NUM> to form second feed stream <NUM> for third reactor <NUM>. In embodiments of the system, third reactor <NUM> is configured to carry out reaction between unreacted isobutylene and methanol of second feed stream <NUM> for producing MTBE in third reactor effluent stream <NUM>. Third reactor <NUM> may include an adiabatic fixed bed reactor. The adiabatic fixed bed reactor can be a down flow reactor. In embodiments of the system, third reactor <NUM> may include a strong-acidic catalyst comprising polystyrene based resin, polystyrene divinyl benzene based resin, sulfonic resin, macroreticular resin, acidic ion-exchange resin, sulphonated macroporous resin, or any combination thereof. The strong acidic catalyst can include a sulfonated polystyrene cross-linked resin. The sulfonated polystyrene cross-linked resin catalyst can be a Amberlyst™ catalyst from DUPONT (USA) including Amberlyst™ <NUM> (A-<NUM>), Amberlyst™ <NUM> (A-<NUM>), Amberlyst™ <NUM> (A-<NUM>), Amberlyst™ <NUM> (A-<NUM>), Amberlyst ™ <NUM> (A-<NUM>), or combinations thereof. Additional examples of the sulfonated polystyrene cross-linked resin can include CT-<NUM>, CT-<NUM>, CT-<NUM>, and combinations thereof (Purolite®, USA).

In embodiments of the system, an outlet of separation column feed drum <NUM> may be in fluid communication with an inlet of primary reaction unit <NUM> such that third portion <NUM> of combined reactor effluent stream <NUM> flows from separation column feed drum <NUM> to primary reaction unit <NUM>. Third portion <NUM> of combined reactor effluent stream <NUM> may be combined with combined feed stream <NUM> before being flowed into primary reaction unit <NUM>.

According to embodiments of the system, second portion <NUM> of combined reactor effluent stream <NUM> and third reactor effluent stream <NUM> can be combined to form mixed intermediate product stream <NUM>. In embodiments of the system, system <NUM> includes separation column <NUM> configured to separate mixed intermediate product stream <NUM> to form (i) top stream <NUM> including methanol, C<NUM> hydrocarbons, and waste, and (ii) product stream <NUM> comprising primarily MTBE. In embodiments of the system, separation column <NUM> can include a distillation column. Separation column <NUM> may not include super fractionator. In embodiments of the system, separation column <NUM> may include a feed filter configured to filter mixed intermediate product stream <NUM> before it is flowed into separation column <NUM>. Separation column <NUM> may further include a heat exchanger configured to heat mixed intermediate product stream <NUM> before it is flowed into separation column <NUM> using product stream <NUM> as a heating medium. In embodiments of the system, separation column <NUM> is configured to utilize medium pressure steam as a heating medium for a reboiler thereof. In embodiments of the system, the reboiler of separation column <NUM> may include a vertical thermosiphon exchanger, and a reboiler de-superheater configured to de-superheat the medium pressure steam before it enters the reboiler.

According to embodiments of thesystem, an outlet of separation column <NUM> is in fluid communication with methanol washing tower <NUM> such that top stream <NUM> flows from separation column <NUM> to methanol washing tower <NUM>. Methanol washing tower <NUM>, in embodiments of the system, is configured to separate top stream <NUM> to produce recycle methanol stream <NUM> comprising primarily methanol, and C<NUM> raffinate stream <NUM> comprising primarily C<NUM> hydrocarbons, and waste stream <NUM>. Waste stream <NUM> may be further processed in carbon bed to remove total organic carbon (TOC) before water discharge. In embodiments of the system, methanol washing tower <NUM> may include a raffinate wash column and a methanol enrichment column. The raffinate wash column can be configured to extract methanol from top stream <NUM> using a countercurrent stream of water. The methanol enrichment column is configured to separate wash water from the methanol of a bottom stream of the raffinate wash column. The methanol enrichment column may comprise trays and downcomers. In embodiments of the system, a bottom stream of the methanol enrichment column can be pumped back to the raffinate wash column with some fresh condensate to make up for water loss. An overhead stream of the methanol enrichment column can be recycled as part of methanol feed for system <NUM>.

Methods for producing MTBE from isobutylene and methanol with a reduced production cost compared to conventional methods have been discovered. As shown in <FIG>, embodiments of the invention include method <NUM> for producing methyl tertiary (tert) butyl ether (MTBE). Method <NUM> may be implemented by system <NUM>, as shown in <FIG>, and described above.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> incudes feeding isobutylene and methanol to first reactor <NUM> and second reactor <NUM>, arranged in parallel. In embodiments of the invention, at block <NUM>, isobutylene is supplied from crude C<NUM> stream <NUM> comprising isobutylene, <NUM>-butene, <NUM>-butene, n-butane, isobutane, <NUM>,<NUM>-butadiene, or combinations thereof. Crude C<NUM> stream <NUM> may be from a C<NUM> raffinate of a steam cracking unit or from a fluid catalytic cracking unit. In embodiments of the invention, crude C<NUM> stream may include <NUM> to <NUM> wt. % isobutylene. First methanol stream may comprise <NUM> to <NUM> wt. % methanol.

In embodiments of the invention, feeding at block <NUM> can include mixing crude C<NUM> stream <NUM> with first methanol stream <NUM> to form combined feed stream <NUM>. Mixing at block <NUM> may be carried out at a molar ratio of first methanol stream to isobutylene in crude C<NUM> stream to first methanol stream in a range of <NUM> to <NUM> and all ranges and values there between including ranges of <NUM> to <NUM>, <NUM> to <NUM>, and <NUM> to <NUM>. Combined feed stream <NUM> may contain an excessive amount of methanol adapted to overcome an azeotropic limit in an overhead of separation column <NUM>. Feeding at block <NUM> can further include optionally heating combined feed stream <NUM> to a predetermined temperature. The predetermined temperature may be in a range of <NUM> to <NUM>, preferably at about <NUM> and all ranges and values there between including ranges of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, and <NUM> to <NUM>. In embodiments of the invention, feeding at block <NUM> may further include splitting combined feed stream <NUM> to produce a first feed stream and a second feed stream. Feeding at block <NUM>, according to embodiments of the invention, may further still include feeding the first feed stream to first reactor <NUM> and feeding the second feed stream to second reactor <NUM>.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes subjecting the isobutylene and the methanol, in first reactor <NUM> and second reactor <NUM>, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from first reactor <NUM> and in effluent from second reactor <NUM>. In embodiments of the invention, reaction conditions in first reactor <NUM> and/or second reactor <NUM> include a reaction temperature of <NUM> to <NUM> and all ranges and values there between including ranges of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, and <NUM> to <NUM>. Reaction conditions in first reactor <NUM> and/or second reactor <NUM> may include an operating pressure of <NUM> to <NUM> bar and all ranges and values there between including ranges of <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, and <NUM> to <NUM> bar. In embodiments of the invention, reaction conditions in first reactor <NUM> and/or second reactor <NUM> include a weight hourly space velocity in a range of <NUM> to <NUM> hr-<NUM> and all ranges and values there between including ranges of <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, and <NUM> to <NUM> hr-<NUM>. According to embodiments of the invention, the effluent from first reactor <NUM> and/or the effluent from second reactor <NUM> comprises <NUM> to <NUM> wt. % MTBE, and <NUM> to <NUM> wt. % unreacted isobutylene. The effluent from first reactor <NUM> and/or the effluent from second reactor <NUM> may comprise <NUM> to <NUM> wt. % C<NUM> hydrocarbons other than isobutylene. In embodiments of the invention, first reactor <NUM> and/or second reactor <NUM> are operated such that an isobutylene conversion rate of <NUM>% is achieved by primary reaction unit <NUM>.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes combining the effluent from first reactor <NUM> and the effluent from second reactor <NUM> to form combined reactor effluent stream <NUM> comprising MTBE and unreacted isobutylene. In embodiments of the invention, the effluent from first reactor <NUM> and/or the effluent from second reactor <NUM> comprises water, and the combining step at block <NUM> comprises combining the effluent stream from first reactor <NUM> and the effluent from second reactor <NUM> to form combined stream <NUM> comprising MTBE, water, and isobutylene, and separating water in separation column feed drum <NUM> from combined stream <NUM> comprising MTBE, water, and isobutylene to form combined reactor effluent stream <NUM>. The separation column feed drum can be operated at a temperature of <NUM> to <NUM> and a pressure of <NUM> to <NUM> bar.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes reacting the isobutylene of first portion <NUM> of combined reactor effluent stream <NUM> with methanol of second methanol stream <NUM> in third reactor <NUM> that is in series with first reactor <NUM> and second reactor <NUM>, to produce third reactor effluent stream <NUM> comprising a second portion of MTBE. At block <NUM>, third reactor <NUM> can be operated at an operating temperature of <NUM> to <NUM> and all ranges and values there between including ranges of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, and <NUM> to <NUM>. At block <NUM>, third reactor <NUM> can be operated at an operating pressure of <NUM> to <NUM> bar and all ranges and values there between including ranges of <NUM> to <NUM> bar, <NUM> to <NUM> bar, <NUM> to <NUM> bar, and <NUM> to <NUM> bar. At block <NUM>, third reactor <NUM> can be operated with a weight hourly space velocity in a ranges of <NUM> to <NUM> hr-<NUM> and all ranges and values there between including ranges of <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, <NUM> to <NUM> hr-<NUM>, and <NUM> to <NUM> hr-<NUM>. In embodiments of the invention, third reactor effluent stream <NUM> comprises <NUM> to <NUM> wt. % MTBE and all ranges and values there between including ranges of <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, <NUM> to <NUM> wt. %, and <NUM> to <NUM> wt. In embodiments of the invention, third reactor <NUM> is operated to convert about <NUM>% more isobutylene from first portion <NUM> of combined reactor effluent stream <NUM>. In embodiments of the invention, an overall conversion rate of <NUM> to <NUM>% for isobutylene can be achieved at block <NUM>. In embodiments of the invention, first reactor <NUM>, second reactor <NUM>, and third reactor <NUM> can be operated under substantially the same, or different operating conditions, which include operating temperature, operating pressure, weight hourly space velocity, or any combinations thereof. In embodiments of the invention, third portion <NUM> of combined reactor effluent stream <NUM> may be cooled to a predetermined temperature before it is flowed into third reactor <NUM>. The predetermined temperature for third portion <NUM> of combined reactor effluent stream <NUM> may be about <NUM>. In embodiments of the invention, at least some of fresh crude C<NUM> stream including isobutylene is added into first portion <NUM> of combined reactor effluent stream <NUM> before it is flowed into third reactor <NUM>.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes mixing second portion <NUM> of combined reactor effluent stream <NUM> with third reactor effluent stream <NUM> to form mixed intermediate product stream <NUM>. According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes recycling third portion <NUM> of combined reactor effluent stream <NUM> to first reactor <NUM>, second reactor <NUM>, and/or third reactor <NUM>. A volumetric ratio between third portion <NUM> of combined reactor effluent stream <NUM> to combined feed stream <NUM> may be in a range of <NUM> to <NUM> (i.e., the recycle/fresh feed ratio is <NUM>-<NUM>. At block <NUM>, third portion <NUM> of combined effluent stream <NUM> may be combined with combined feed stream <NUM> before being flowed into first reactor <NUM> and/or second reactor <NUM>. A volumetric ratio of third portion <NUM> that is flowed into first reactor <NUM> and second reactor <NUM> to combined feed stream <NUM> may be in a range of about <NUM>.

According to embodiments of the invention, as shown in block <NUM>, method <NUM> includes separating mixed intermediate product stream <NUM> to form product stream <NUM> comprising primarily MTBE, recycle methanol stream <NUM> comprising primarily methanol, and C<NUM> raffinate stream <NUM> comprising primarily C<NUM> hydrocarbons. Product stream <NUM> may comprise at least <NUM> wt. In embodiments of the invention, separating at block <NUM> can include separating mixed intermediate product stream <NUM> in separation column <NUM> to produce top stream <NUM> comprising methanol and C<NUM> hydrocarbons, and product stream <NUM> comprising primarily MTBE. Separation column <NUM> may be operated at an overhead temperature range of <NUM> to <NUM> and a bottom (or reboiler) temperature range of <NUM> to <NUM>. Separation column <NUM> may be operated at an operating pressure of <NUM> to <NUM> bar. Separating at block <NUM> may further include processing top stream <NUM> in methanol washing tower <NUM> to produce recycle methanol stream <NUM>, C<NUM> raffinate stream <NUM>, and/or waste stream <NUM> comprising waste water with TOC (total organic carbon). The processing step in methanol washing tower <NUM> may further produce residual methanol, which is recycled to primary reaction unit <NUM> and/or third reactor <NUM>. In embodiments of the invention, the raffinate wash column of methanol washing tower <NUM> can be operated at a temperature of <NUM> to <NUM>, a pressure of <NUM> to <NUM> bar. The methanol enrichment column of methanol washing tower <NUM> can be operated at a temperature of <NUM> to <NUM> and an operating pressure of <NUM> to <NUM> bar. In embodiments of the invention, product stream <NUM> can be cooled in the heat exchanger of separation column <NUM> and/or in a product cooler to achieve a battery limit temperature.

According to embodiments of the invention, including MTBE in a feed stream into an MTBE synthesis reaction unit (e.g., first reactor <NUM>, second reactor <NUM>, and/or third reactor <NUM>) improves conversion rate of isobutylene for MTBE production compared to no MTBE in the feed stream into the MTBE synthesis reaction unit. In embodiments of the invention, the isobutylene conversion rate increases with an increasing MTBE concentration in the feed stream into the MTBE synthesis reaction unit. The improvement of isobutylene conversion rate may be due to impact of MTBE on catalyst activity, which is caused by structural change of the catalyst, and optimization of exothermic nature of the MTBE synthesis reaction. In embodiments of the invention, the isobutylene conversion rate and the MTBE concentration in the feed stream to an MTBE synthesis reaction unit can have a substantially linear correlation.

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

The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

As part of the disclosure of the present invention, specific examples are included below. The examples are for illustrative purposes only and are not intended to limit the invention. The present examples are outside of the scope of present claim <NUM> and are for reference only.

Simulations were conducted in Pro II platform for MTBE production in a system disclosed above. A first methanol stream at about <NUM> and a C<NUM> raffinate stream at <NUM> were fed into the system, as described above. The system did not include a catalytic distillation column, a reactive distillation column, or a super fractionator. Results for the composition of process streams and product stream are shown in Table <NUM>.

The results show that the system was capable of producing an MTBE product stream comprising more than <NUM> wt. % MTBE without using a catalytic (reactive) distillation column and a super fractionator.

Experiments were conducted to investigate effects of MTBE recycle stream on the conversion rate of isobutylene and selectivity of MTBE in an MTBE synthesis reactor. The reaction conditions used in the experiments included a reaction temperature of <NUM>, and a weight hourly space velocity of <NUM> hr-<NUM>. The C<NUM> raffinate feed was flowed into the reactor at a flow rate of <NUM>/hr. Methanol was flowed into the reactor at a flow rate of <NUM> to achieve an isobutene to methanol molar ratio of about <NUM>:<NUM>. The catalyst used in the reactor was about <NUM>. The correlation between isobutylene conversion rate (%) and time on stream (reaction time, hr) was plotted in <FIG> for reactors operated with and without MTBE recycle. The correlation between MTBE selectivity (%) and time on stream (reaction time, hr) was plotted in <FIG> for reactors operated with and without MTBE recycle.

The results indicate that MTBE production processes that include recycling part of MTBE product stream back to the reactor show about <NUM>% improvement in isobutylene conversion rate compared to the conversion rate achieved by MTBE production processes that does not use MTBE recycle stream. This is due to impact of MTBE on catalyst activity, which is caused by structural change of the catalyst, and optimization of exothermic nature of the MTBE synthesis reaction. However, the selectivity of MTBE does not show any difference between MTBE production processes that recycled part of MTBE product stream back to the reactor and MTBE production processes that does not use MTBE recycle stream.

Simulations were conducted using PRO II platform to obtain compositions of a feed stream flowed into a reactor for MTBE synthesis. The compositions of the feed stream flowed into reactor for MTBE synthesis are shown in Table <NUM>. Experiments were then conducted using the feed stream compositions obtained via the simulations. For the experiments, the catalyst (A-<NUM>) quantity used was about <NUM>. The reaction temperature for MTBE synthesis was <NUM> and the weight hourly space velocity used for MTBE synthesis experiments was about <NUM> hr-<NUM>. The methanol to isobutylene molar ratio fed into the system was <NUM>:<NUM>. The results for the MTBE conversion rate against time on stream (hr) for each feed stream composition are shown in FIG. 4A and Table <NUM>.

The results from <FIG> indicate that the isobutylene conversion rate increases with increasing MTBE concentration in feed stream. The results from Table <NUM> were also analyzed via linear regression. The results indicate that the conversion rate for isobutylene (y) can be described by MTBE concentration (x; wt. %) in feed stream as y=<NUM>. 5441x+<NUM> (R<NUM>=<NUM>). This is due to impact of MTBE on catalyst activity, which is caused by structural change of the catalyst, and optimization of exothermic nature of the MTBE synthesis reaction.

In the context of the present invention, at least the following embodiments are described. Embodiment <NUM> is a method of producing methyl tertiary butyl ether (MTBE). The method includes feeding isobutylene and methanol to a first reactor and a second reactor, arranged in parallel and subjecting the isobutylene and the methanol, in the first reactor and the second reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first reactor and in effluent from the second reactor. The method further includes combining effluent from the first reactor and effluent from the second reactor to form a combined reactor effluent stream, wherein the combined reactor effluent stream further contains isobutylene. The method still further includes reacting the isobutylene contained in a first portion of the combined reactor effluent stream with methanol in a third reactor that is in series with the first reactor and 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 containing primarily MTBE, a stream containing primarily methanol, and a C<NUM> raffinate stream. Embodiment <NUM> also comprises the step of feeding isobutylene and methanol to the first reactor and the second reactor includes mixing a crude C<NUM> stream containing isobutylene with methanol to form a feed stream and splitting 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. In embodiment <NUM> , the method does not include a separation step that utilizes a super fractionator column or catalytic distillation column. Embodiment <NUM> is the method of embodiment <NUM>, wherein the first reactor, the second reactor, and/or the third reactor each individually include an adiabatic fixed bed reactor. Embodiment <NUM> is the method of either of embodiments <NUM> or <NUM>, wherein the first reactor includes an adiabatic fixed bed reactor. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the first reactor effluent stream and the second reactor effluent stream further contains includes combining the effluent from the first reactor and the effluent from the second reactor to form a stream containing MTBE, water, isobutylene. The method further includes separating water from the stream containing MTBE, water, isobutylene to form the combined reactor effluent stream. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the first reactor and/or the second reactor each individually include a down flow reactor. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the first reactor and the second reactor each comprise a polystyrene based resin. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the product stream contains at least <NUM> wt. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the third reactor is operated at a higher pressure than the first reactor and the second reactor. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM> and <NUM> to <NUM>, wherein the first reactor and the second reactor each include a catalyst that contains polystyrene based resin, polystyrene divinyl benzene based resin, sulfonic resin, macroreticular resin, acidic ion-exchange resin, sulphonated macroporous resin, or any combination thereof. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the first reactor and the second reactor are each operated at an operating temperature in a range <NUM> to <NUM>. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the first reactor and the second reactor are each operated at an operating pressure in a range of <NUM> to <NUM> bar. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the effluent from the first reactor and the effluent from the second reactor each contains <NUM> to <NUM> wt. % MTBE, and <NUM> to <NUM> wt. % isobutene. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the effluent from the third reactor contains <NUM> to <NUM> wt. % isobutylene. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the third reactor is operated at an operating temperature in a range <NUM> to <NUM>. Embodiment <NUM> is the method of any of embodiments <NUM> to <NUM>, wherein the third reactor is operated at an operating pressure in a range of <NUM> to <NUM> bar. Embodiment <NUM> is the method of any of embodiments of <NUM> to <NUM>, wherein MTBE in the first portion of the combined reactor effluent stream flowed in the third reactor, and/or MTBE in the third portion of the combined effluent stream flowed into the first reactor and the second reactor is capable of improving isobutylene conversion rate for MTBE synthesis.

Embodiment <NUM> is a method of producing methyl tertiary butyl ether (MTBE). The method includes mixing a crude C<NUM> stream containing isobutylene with methanol to form a feed stream and splitting 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. The method still further includes subjecting the isobutylene and the methanol, in the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first adiabatic fixed bed reactor and in effluent from the second adiabatic fixed bed reactor. The method also includes combining effluent from the first adiabatic fixed bed reactor and effluent from the second adiabatic fixed bed reactor to form a combined reactor effluent stream, wherein the combined reactor effluent stream further contains isobutylene. In addition, the method includes reacting the isobutylene contained in a first portion of the combined reactor effluent stream with methanol in a third adiabatic fixed bed reactor that is in series with the first adiabatic fixed bed reactor and second adiabatic fixed bed reactor, to produce a third adiabatic fixed bed reactor effluent stream containing a second portion of MTBE. The method yet further includes mixing a 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 a third portion of the combined effluent stream to the first adiabatic fixed bed reactor and the second adiabatic fixed bed reactor, and separating the mixed intermediate product stream to form a stream containing primarily MTBE, a stream containing primarily methanol, and a C<NUM> raffinate stream.

Claim 1:
A method of producing methyl tertiary butyl ether (MTBE), the method comprising:
feeding isobutylene and methanol to a first reactor and a second reactor, arranged in parallel;
subjecting the isobutylene and the methanol, in the first reactor and the second reactor, respectively, to reaction conditions sufficient to cause the isobutylene to react with the methanol to produce a first portion of MTBE in effluent from the first reactor and in effluent from the second reactor;
combining effluent from the first reactor and effluent from the second reactor to form a combined reactor effluent stream, wherein the combined reactor effluent stream further comprises isobutylene;
reacting the isobutylene comprised in a first portion of the combined reactor effluent stream with methanol in a third reactor that is in series with the first reactor and second reactor, to produce a third reactor effluent stream comprising a second portion of MTBE;
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; and
separating the mixed intermediate product stream to form a product stream comprising primarily MTBE, a stream comprising primarily methanol, and a C4 raffinate stream;
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;
splitting the feed stream into a first feed stream and a second feed stream; and
feeding the first feed stream to the first reactor and feeding the second feed stream to the second reactor;
wherein the method does not include a separation step that utilizes super fractionator column or catalytic distillation column.