Process for producing high-purity 1-butene and high-purity isobutane

Abstract

To provide a process and an apparatus for producing high-purity 1-butene and high-purity isobutene from two C4 hydrocarbon streams, in which the two C4 hydrocarbon streams are in part processed together.SOLUTION: Provided is a process for producing high-purity 1-butene and high-purity isobutene from two C4 hydrocarbon streams, in which the two C4 hydrocarbon streams are in part processed together.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention provides a method for partially co-processing two C4 hydrocarbon streams to produce high-purity 1-butene and high-purity isobutene from the two C4 hydrocarbon streams. The present invention also relates to an apparatus for carrying out the method according to the invention. [Background technology]

[0002] Processes for producing high-purity 1-butene and high-purity isobutane are known and are described, for example, in Patent Document 1. These processes are characterized in particular by the initial removal of isobutene and butadiene from the C4 hydrocarbon stream used. Isobutene can be removed, for example, by conversion to MTBE or isobutene dimer and then separating the resulting products. Butadiene can be removed by extraction and, if necessary, by selective hydrogenation. Further workup to obtain high-purity 1-butene and isobutane streams is usually carried out by distillation.

[0003] A drawback of the method disclosed in Patent Document 1 is that two separate production lines must be operated to process the two C4 hydrocarbon streams used. However, this involves high capital and operating costs. Furthermore, operating two separate production lines requires a large amount of energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 071815 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the underlying objective of the present invention was to provide a method and apparatus that does not suffer from these problems. In order to save capital costs and energy, as few production plants as possible should be operated in parallel. Nevertheless, the method must be able to produce a high-purity 1-butene stream and a high-purity isobutane stream. Therefore, the savings must not be at the expense of the purity of the 1-butene and isobutane streams. [Means for solving the problem]

[0006] This object is achieved by the method for producing high-purity 1-butene and high-purity isobutane according to claim 1. Preferred configurations are set out in the dependent claims. This object has been achieved by the process according to the invention as defined in claim 1. Preferred embodiments are defined in the dependent claims. The process according to the invention is a process for producing high-purity 1-butene and high-purity isobutane, comprising the steps of: (a) providing a first C4 hydrocarbon stream A and a second C4 hydrocarbon stream B, wherein the two streams A and B each contain at least 1,3-butadiene, isobutene, isobutane, 1-butene, and 2-butene, and the concentration of isobutane in stream A is greater than the concentration of isobutane in stream B; (b) feeding said stream A to an isobutane separation unit, wherein at least a portion of the isobutane present in said stream A is separated to form an isobutane-depleted stream; (c) separating a portion of said isobutane-depleted stream and combining this portion with said stream B to obtain stream C; (d) feeding said stream C to a reaction unit with an alcohol, preferably methanol or ethanol, particularly preferably methanol, in order to convert at least a portion of the isobutene present in said stream C into ATBE (alkyl tert-butyl ether), preferably MTBE (methyl tert-butyl ether) or ETBE (ethyl tert-butyl ether), particularly preferably MTBE (methyl tert-butyl ether) and / or isobutene dimer, to obtain a reaction effluent, which is subjected to product separation to produce a residue stream comprising at least said alcohol, preferably methanol or ethanol, particularly preferably methanol, 1,3-butadiene, 1-butene, 2-butene and isobutane, and a product stream comprising at least said ATBE, preferably MTBE or ETBE, particularly preferably MTBE and / or isobutene dimer; (e) feeding the residue stream to a first separation unit to obtain in the first separation unit a low-boiling stream containing at least 1,3-butadiene, 1-butene, 2-butene and isobutane, and an aqueous stream containing at least the alcohol, preferably methanol or ethanol, particularly preferably methanol and water; (f) feeding the aqueous stream to a recovery unit for at least partially separating the alcohol, preferably methanol and ethanol, particularly preferably methanol, from water and recycling at least a portion of the obtained alcohol, preferably methanol and ethanol, particularly preferably methanol, to the reaction unit; (g) feeding said low boiling stream to a hydrogenation unit to hydrogenate at least a portion of the 1,3-butadiene present thereby obtaining a hydrogenated low boiling stream; (h) feeding the hydrogenated low-boiling stream to a second separation unit to obtain in the second separation unit a stream D comprising at least isobutane and 1-butene, and a stream E comprising at least n-butane and 2-butene; (i) feeding said stream D to a third separation unit, wherein said third separation unit provides a crude isobutane stream and a high purity 1-butene stream; and (j) feeding the crude isobutane stream to a fourth separation unit, and obtaining an off-gas stream and a high purity isobutane stream in the fourth separation unit; Includes. [Effects of the Invention]

[0007] The process according to the invention has the advantage that the majority of two C4 hydrocarbon streams can be processed in one production plant. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a flow diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The first step (a) of the process according to the invention for producing high purity 1-butene and high purity isobutane comprises providing a first C4 hydrocarbon stream A and a second C4 hydrocarbon stream B, wherein the two streams A and B each contain at least 1,3-butadiene, isobutene, isobutane, 1-butene and 2-butene, and the concentration of isobutane in stream A is greater than the concentration of isobutane in stream B.

[0010] In the process according to the invention, all commonly available C4 hydrocarbon mixtures can be used. Suitable C4 hydrocarbon streams are, for example, light petroleum fractions from refineries, C4 fractions from crackers (e.g. steam crackers (also: crack C4 (cracked C4 fraction)), hydrocrackers, fluid cathodic crackers (FCC-C4)), mixtures from Fischer-Tropsch synthesis, mixtures from butane dehydrogenation, mixtures from skeletal isomerization of normal butenes, and mixtures formed by olefin metathesis. These techniques are described in the technical literature. The C4 hydrocarbon streams A and B used can in principle be produced by the same method or process, but the isobutane content of the streams differs. However, this process is particularly aimed at simultaneously producing a high-purity 1-butene stream and an isobutane stream from C4 hydrocarbon streams produced or obtained by two different methods. In a particularly preferred embodiment of the present invention, stream A is an FCC-C4 stream, i.e., a C4 hydrocarbon stream from a fluid cathodic cracker. Stream B is particularly preferably a cracked C4 fraction stream, i.e., a C4 hydrocarbon stream from a steam cracker or raffinate I.

[0011] These upstream processes for the production of C4 hydrocarbon streams produce similar chemical compounds, but result in streams that differ in the composition of the C4 compounds present. The composition of the C4 hydrocarbon stream used in the process according to the invention is preferably as follows: Table 1: Typical composition of cracked C4 fraction (cracked C4), raffinate I and FCC-C4

[0012] [Table 1] is. Therefore, C4 hydrocarbon streams contain different amounts of isobutene depending on the cracking process. Other major components are 1,3-butadiene, 1-butene, 2-butene (cis and trans), n-butane, and isobutane. Typical isobutene content in C4 fractions is 10%-35% by mass for cracked C4 fractions and 10%-20% by mass for FCC-C4 fractions.

[0013] In the process according to the invention, it is advantageous to largely remove polyunsaturated hydrocarbons, such as 1,3-butadiene, from the feed mixture. This results in the production of raffinate I. Therefore, when using a cracked C4 fraction in the process according to the invention, it is necessary to at least partially remove 1,3-butadiene before step a). This can be achieved by known methods, such as extraction, extractive distillation, or complexation. Instead of separating the polyunsaturated hydrocarbons, selective chemical conversion can be performed. For example, 1,3-butadiene can be selectively hydrogenated to linear butenes, as described, for example, in European Patent Application No. 0 523 482. 1,3-butadiene can also be at least partially removed by selective reactions of 1,3-butadiene, such as dimerization to cyclooctadiene, trimerization to cyclododecadiene, polymerization, or telomerization.

[0014] Process (b) The C4 hydrocarbon stream A obtained in step (a) is fed to an isobutane separation step in step (b), where at least a portion of the isobutane present in stream A is separated to form an isobutane-depleted stream. The concentration of isobutane in stream A is preferably reduced to a value of less than 5% by weight by a distillation step, and at the same time, low boilers present in the mixture (e.g., C3 hydrocarbons, light oxygen, nitrogen-containing compounds and sulfur-containing compounds) are also at least partially removed. In a preferred embodiment, the isobutane-depleted stream from step (b) may be fed to a step for removing high boilers and / or nitrogen-containing impurities and / or nitrogen-containing impurities and / or oxygen-containing impurities before being fed to step (c).

[0015] High boiling point removal The removal of high boilers is preferably carried out by distillation. In this case, "high boilers" refers to, for example, C5 hydrocarbons. Thioethers can also be separated by removing high boilers. Thioethers can be produced by thioetherification of mercaptans. Thioetherification is used to remove mercaptans. Such a method is disclosed, for example, in WO 2014 / 009148. The distillative removal of high boilers, such as C5 hydrocarbons, and optionally thioethers, is carried out in at least one distillation column. The high boilers are obtained at the bottom of the column. A stream depleted in isobutane is thus obtained at the top of the distillation column. The distillation column preferably used in this step has preferably 40 to 150 theoretical plates, more preferably 40 to 100, and particularly preferably 50 to 80 theoretical plates. The reflux ratio is preferably 0.5 to 5, particularly preferably 1 to 2.5, depending on the number of plates used, the composition of the column feed and the required purity of the distillate and bottom product of the column. The reflux ratio is defined here as the mass flow rate of the reflux divided by the mass flow rate of the distillate. The column is preferably operated at an operating pressure of 0.1 to 2.0 MPa (absolute), preferably 0.5 to 1.2 MPa (absolute). The column can be heated, for example, with steam. Depending on the selected operating pressure, condensation can be carried out with cooled brine, cooling water, or air. However, the overhead vapor from the column can also be thermally integrated with other columns in the process, such as a column for separating isobutane. In this case, the condenser of the column simultaneously serves as an evaporator for the low-boiling component column. The bottom product can be recycled or used as a feedstock for other processes, such as a synthesis gas plant. Various processes can be used to separate the nitrogen-, sulfur- and / or oxygen-containing impurities.

[0016] Water wash The water wash can completely or partially remove hydrophilic components, such as nitrogen compounds, from the isobutane-reduced stream. Examples of nitrogen compounds include acetonitrile or N-methylpyrrolidone (e.g., from the extractive distillation of 1,3-butadiene). Oxygen compounds (e.g., acetone from an FCC unit) can also be partially removed by the water wash. After the water wash, the isobutane-reduced stream is saturated with water. To avoid two-phase separation in downstream processes of the reactor, the reaction temperature should be about 10°C higher than the water wash temperature.

[0017] Adsorbent Adsorbents are used to remove impurities from the isobutane-reduced stream. This is advantageous, for example, when a precious metal catalyst is used in one of the process steps. Nitrogen or sulfur compounds are often removed via an upstream adsorbent. Examples of adsorbents include aluminum oxide, molecular sieves, zeolites, activated carbon, and metal-impregnated alumina. Adsorbents are commercially available from a variety of companies, such as Alcoa (Selexsorb®).

[0018] Drying Water present in the isobutane-depleted stream, e.g., from a water wash, can be removed by known drying processes. Suitable processes include, for example, distillation of the water as an azeotrope. Azeotropes containing C4 hydrocarbons are often available, or an azeotroping agent can be added.

[0019] Process (c) In step (c), a portion of the isobutane-depleted stream obtained in step (b) is separated. The isobutane-depleted stream is then separated. The separation of at least a portion of the isobutane-depleted stream or the separation of the stream in step (c) can be carried out, for example, via a flow control valve. Corresponding equipment and structures are well known to those skilled in the art. The separated isobutane-depleted portion of the stream is then mixed with stream B to obtain stream C, which is then fed to step (c) for further processing. The other portion of the isobutane-depleted stream is treated independently of stream C, for example, fed to a separate isobutene conversion unit to form ATBE, preferably MTBE or ETBE, or to form isobutene dimers.

[0020] Process (d) After mixing the two streams in step (c) to obtain stream C, stream C and an alcohol, preferably methanol or ethanol, particularly preferably methanol, are fed to a reaction unit in which at least a portion of the isobutene present in stream C is converted into ATBE (alkyl tert-butyl ether), preferably MTBE (methyl tert-butyl ether) or ETBE (ethyl tert-butyl ether), particularly preferably MTBE (methyl tert-butyl ether) and / or isobutene dimer, to obtain a reaction effluent, which is subjected to product separation to produce a residue stream comprising at least an alcohol, preferably methanol or ethanol, particularly preferably methanol, 1,3-butadiene, 1-butene, 2-butene and isobutane, and a product stream comprising at least ATBE, preferably MTBE or ETBE, particularly preferably MTBE and / or isobutene dimer. The conversions in step (d) are carried out in one or more reactors suitable for each conversion. When multiple reactors are present, these reactors can be connected in parallel or in series. Thus, various configurations are possible. For example, the conversions can be carried out in a fixed-bed reactor in series or in a series of fixed-bed reactors, and may include an intermediate separation stage for removing a portion of the product (ATBE or isobutene dimer). In some embodiments, the upstream reaction effluent can be fed to a final reactor, which may be a reactive distillation reactor, thereby simultaneously reacting at least a portion of the residual isobutene and separating the dimer or ATBE from the remaining C4 components, including n-butane, isobutane, 1-butene, and 2-butene. In this case, the reactive distillation also corresponds to the product separation.

[0021] In a preferred embodiment of the present invention, the conversion in step (d) is carried out in at least two reaction stages, at least the last of which is carried out as a reactive distillation. The conversion of ATBE in this stage is preferably at least 70%, particularly preferably at least 90%. The alcohol used in the conversion of step (d) is preferably methanol or ethanol, particularly preferably methanol, and can act as a reactant (in the case of the production of ATBE or MTBE or ETBE) or as a moderator (in the case of the selective dimerization to isobutene dimer), the two options being explained in more detail below.

[0022] Production of ATBE, preferably MTBE or ETBE When ATBE, MTBE, or ETBE is produced in step (d), the ATBE production is preferably carried out in two stages. The first stage of the ATBE synthesis in step (d) according to the present invention is preferably carried out in a fixed-bed reactor, and the second stage of the reaction is preferably carried out by reactive distillation. In this context, reactive distillation simultaneously refers to product separation. The first stage of the ATBE synthesis is preferably carried out in at least two, particularly preferably three, fixed-bed reactors. Conventional fixed-bed reactors (tube bundle furnaces, adiabatic fixed-bed furnaces, recycle furnaces) can be used as reactors for reacting alcohol, preferably methanol or ethanol, particularly preferably methanol, with isobutene in a state close to thermodynamic equilibrium. The two-stage ATBE synthesis can, in particular, reduce the residual isobutene concentration in the reaction effluent to less than 1000 ppm by mass, preferably 800 ppm by mass, particularly preferably less than 500 ppm by mass, based on the C4 mixture in the distillate. In the first stage, isobutene is preferably converted until thermodynamic equilibrium is reached between ATBE, an alcohol, preferably methanol or ethanol, particularly preferably methanol, and isobutene, the conversion of isobutene being preferably greater than 94%, particularly preferably greater than 96%. The first stage reactor is preferably operated at a temperature of 20 to 110°C, preferably 25 to 70°C, and a pressure of 0.5 to 5 MPa, preferably 0.7 to 2 MPa.

[0023] Since the thermodynamic equilibrium between alcohol / isobutene and ether is predominantly on the ether side at low temperatures, it is preferable to operate the first reactor at a higher temperature than subsequent reactors in order to take advantage of the equilibrium and achieve a higher reaction rate. The molar ratio of alcohol to isobutene (alcohol:isobutene) in the feedstock supplied to the first reactor of the first stage is preferably in the range of 10:1 to 1:1, particularly preferably in the range of 5:1 to 1.1:1, and particularly preferably in the range of 1.8:1 to 1.2:1.

[0024] The second stage of ATBE synthesis is preferably carried out in a reactive distillation column. In addition to further converting isobutene to ATBE, the reactive distillation also separates the product into a residue stream containing at least alcohol, preferably methanol or ethanol, particularly preferably methanol, 1,3-butadiene, 1-butene, 2-butene, and isobutane, and a product stream containing at least ATBE and / or isobutene dimer. The residue stream thus separated is further treated in step (e) according to the present invention. The second stage of ATBE synthesis is more preferably carried out in a reactive distillation column operated with an acidic ion exchange resin at a gauge pressure ranging from 0.5 to 1.5 MPa, preferably 0.75 to 1.0 MPa, a reaction zone temperature ranging from 50 to 90°C, preferably 55 to 70°C, and a reflux ratio ranging from 0.5 to 1.5, preferably 0.7 to 0.9. The reflux ratio is defined as the ratio of the reflux stream entering the column to the distillate stream leaving the column. The temperature of the column feed is preferably 50 to 90°C, preferably 60 to 75°C, regardless of its composition, the reaction pressure in the column, and the throughput.

[0025] The feed to the reactive distillation column can be fed above or below the catalyst zone, but is preferably fed below the catalyst zone. The feed to the reactive distillation column is preferably located below the reaction packing, preferably 3 to 13 theoretical plates below the reaction packing, and particularly preferably 4 to 10 theoretical plates below the reaction packing. If desired, additional alcohol, preferably methanol or ethanol, particularly preferably methanol, can be fed to the second stage together with the feed from the first stage or at one or more points within the reactive distillation column, for example at the top of the column and / or above, between and / or below the catalyst beds.

[0026] The reactive distillation column preferably contains a catalyst in a rectification column, preferably with separating trays or distillation packings arranged above and below the catalyst packing. The catalyst can be integrated into packings such as KataMax® packings, KataPak® packings, or MultiPak® packings, or polymerized on shaped bodies. KataMax® packings are preferably used. The reactive distillation column preferably has a zone above the catalyst packing where separation by distillation is carried out. The zone above the catalyst packing preferably has 5 to 20, particularly 10 to 15, separating plates. The separation zone below the catalyst preferably has 12 to 36, particularly 20 to 30, separating plates. The catalyst zone is estimated to have a distillation effect of 1 to 5 theoretical plates per meter of packing height. The height of the catalyst zone / reaction zone can be determined by simple preliminary tests depending on the desired isobutene conversion. The amount of catalyst is preferably selected so that the isobutene conversion is 75 to 99%, preferably 85 to 98%, particularly preferably 95 to 97%, based on the isobutene content in the feedstock to the reactive distillation.

[0027] A solid acidic ion exchange resin having sulfonic acid groups is preferably used as a catalyst in the ATBE synthesis in step (d). Suitable ion exchange resins include those prepared by sulfonation of phenol / aldehyde condensates or aromatic vinyl compound cooligomers. Examples of aromatic vinyl compounds for the preparation of cooligomers include styrene, vinyltoluene, vinylnaphthalene, vinylethylbenzene, methylstyrene, vinylchlorobenzene, vinylxylene, and divinylbenzene. In particular, cooligomers formed by the reaction of styrene with divinylbenzene are used as precursors for the preparation of sulfonic acid group-containing ion exchange resins. Resins can be prepared in gel, macroporous, or sponge-like forms. The properties of these resins, particularly the specific surface area, porosity, stability, swelling or shrinkage, and exchange capacity, can be varied by the preparation process.

[0028] In the process according to the invention, ion exchange resins can be used in the H form. Strongly acidic resins of the styrene-divinylbenzene type are used and are sold under the following trade names: Duolite® C20, Duolite® C26, Amberlyst® 15, Amberlyst® 35, Amberlite® IR-120, Amberlite® 200, Dowex® 50, Lewatit® SPC 118, Lewatit® SPC 108, K2611, K2621, OC 1501. Preferred ion exchange resins are Amberlyst® 15, Amberlyst® 35 or Lewatit® K2621.

[0029] ATBE, obtained as the bottom product of the second stage of ATBE synthesis, preferably the reactive distillation column, can be used for a variety of applications. Because the content of alkyl sec-butyl ether (ASBE) is extremely low, cracking of alkyl sec-butyl ethers produces almost no linear butenes, making it suitable for the production of high-purity isobutene by cracking. Because the ATBE obtained by this method contains only a small amount of by-products (ASBE and C8 olefins), it can be used as an analytical solvent or a solvent for organic synthesis after separation from residual alcohols. It can also be used as a component of gasoline.

[0030] The ATBE synthesis in step (d) of the process according to the invention is preferably carried out in a second stage such that product streams are obtained as an overhead product comprising an alcohol, preferably methanol or ethanol, particularly preferably methanol, and a C4-hydrocarbon mixture (1,3-butadiene, 1-butene, 2-butene and isobutane), with an isobutene content of less than 1000 ppm by mass, based on the C4-hydrocarbon mixture, and a bottom product comprising ATBE.

[0031] Production of isobutene dimer Alternatively, in step (d) of the process according to the invention, isobutene is converted into isobutene dimers (diisobutenes). The production of isobutene dimers in step (d) can in principle be carried out using a homogeneous catalyst, i.e., a catalyst that is soluble in the reaction mixture, or a heterogeneous catalyst, i.e., a catalyst that is insoluble in the reaction mixture. The production of isobutene dimers in step (d) is preferably carried out on a solid heterogeneous catalyst, more preferably arranged in a fixed bed, thereby eliminating the need for complex catalyst removal.

[0032] As solid catalysts, acidic substances insoluble in the reaction effluent / product mixture can be used. Most of these catalysts belong to the following group: a) inorganic acids (e.g., sulfuric acid or phosphoric acid) on a support (e.g., aluminum oxide or silicon dioxide) b) Zeolites or other aluminosilicates, doped or not doped with other metals (especially transition metals), or c) acidic ion exchange resins, especially acidic cation exchange resins It belongs to one of the following. Acidic ion exchange resins are preferred as catalysts because of their high selectivity for the production of isobutene oligomers and the formation of minimal by-products. Suitable ion exchange resins include those produced by the sulfonation of phenol / aldehyde condensates or aromatic vinyl compound cooligomers. Examples of aromatic vinyl compounds used to produce cooligomers include styrene, vinyltoluene, vinylnaphthalene, vinylethylbenzene, methylstyrene, vinylchlorobenzene, vinylxylene, and divinylbenzene. In particular, cooligomers produced by the reaction of styrene and divinylbenzene are used as precursors in the production of sulfonic ion exchange resins. The properties of these resins, particularly their specific surface area, porosity, stability, swelling / shrinkage, and exchange capacity, can be varied by the manufacturing process. Resins can be produced in gel, macroporous, or sponge-like forms. Strongly acidic resins of the styrene-divinylbenzene type are sold especially under the following trade names: Purolite® CT 151, Amberlyst® 15, Amberlyst® 35, Amberlite® IR-120, Amberlite® 200, Dowex® M-31, K2611, K2431.

[0033] The acidic ion exchange resin is preferably adjusted to have an activity that oligomerizes isobutene but hardly catalyzes the co-oligomerization of isobutene and normal butene, the oligomerization of normal butene, and the isomerization of normal butene. Furthermore, the heat generation amount in the reactor is adjusted to a technically manageable value.

[0034] The desired catalytic activity can be adjusted using moderators. These substances are passed over the catalyst together with the reaction effluent. The moderators used are alcohols, either pure or in mixture, preferably methanol or ethanol, particularly preferably ethanol. Therefore, the production of isobutene dimers is preferably carried out in the presence of these moderators. When a moderator is used, the molar ratio of moderator per mole of isobutene is preferably set to 0.01 to 5, preferably 0.01 to 1, and in particular 0.01 to 0.7 mol.

[0035] The reactors in the process according to the invention may contain a mixture of ion exchange resins of different reactivity. The reactors may contain catalysts of different activities, arranged, for example, in layers. When multiple reactors are used, the individual reactors may be filled with catalysts of the same or different activities. Reactors used in industrial processes can be operated adiabatically, polytropically, or substantially isothermally. Substantially isothermal means that the temperature at any point within the reactor is not more than 10°C higher than the temperature at the reactor inlet. When a reactor is operated adiabatically, it is usually desirable to connect multiple reactors in series, preferably with cooling between the reactors. Examples of reactors suitable for polytropic or substantially isothermal operation include tube bundle reactors, water-cooled tubular reactors (with a shell-side cooling system), stirred tank reactors, and loop reactors. Multiple reactors can be combined or of different designs. Reactors can also be operated with product recycle. In a preferred embodiment of the present invention, the production of isobutene dimer is carried out in at least two reactors connected in series, with intermediate dimer separation between each reactor. The temperature in the production of isobutene dimer in step (d) is preferably in the range of 15 to 160°C, and more preferably in the range of 40 to 110°C.

[0036] The conversion can be carried out with or without the addition of an additional solvent. As the solvent, preferably a saturated hydrocarbon, in particular a C4, C8 or C12 hydrocarbon, is used. When a solvent is added, its proportion is 0% to 60% by mass, preferably 0% to 30% by mass.

[0037] The conversion according to the invention can be carried out at a pressure equal to or greater than the vapor pressure of stream C at the respective reaction temperature, preferably less than 40 bar. That is, stream C is present entirely or partly in the liquid phase during the dimerization. If the reaction is carried out entirely in the liquid phase, the pressure may be preferably 2 to 4 bar higher than the vapor pressure of the reaction mixture in order to avoid evaporation problems in the reactor. When the reaction is carried out at a pressure where the reaction mixture is not completely liquid (e.g., reactive distillation), the oligomerization according to the process of the present invention is still carried out in the liquid phase, i.e., over a "wet" catalyst, i.e., a catalyst wetted with a liquid.

[0038] The total conversion of isobutene to dimers can be adjusted by the type and amount of catalyst used, reaction conditions, and the number of reactors. In the process of the present invention, 30% to 95%, preferably 50% to 80%, particularly preferably 55% to 70% of the isobutene present in the reaction effluent is converted (converted). The dimerization reaction mixture can be prepared in a variety of ways. The products are preferably separated by distillation. Reactive distillation may also be used. Product separation results in a residue stream containing at least methanol, 1,3-butadiene, 1-butene, 2-butene, and isobutane, and a product stream containing at least isobutene dimer.

[0039] The distillation is preferably carried out at a pressure of 1 to 10 bara (bara = absolute pressure), particularly preferably at a pressure of 4 to 7 bara. The temperature at the bottom is preferably 120 to 220°C, particularly preferably 170 to 200°C. The reflux ratio is preferably set at a value of 0.1 to 1.5, preferably 0.3 to 1.0. The distillation is preferably carried out in a column with 20 to 40 plates, preferably 25 to 35 plates. The residue stream thus separated is further treated in step (e) according to the invention.

[0040] The separated product stream contains mainly isobutene dimers (C8 hydrocarbons) and, if necessary, a portion of the moderator used. In addition to diisobutene, it may also contain co-dimers and higher oligomers (C12, C16+, etc.). The proportion of co-oligomers is preferably less than 25% by mass. The product stream can be separated in further distillation steps. For example, a fraction containing high-purity diisobutene can be separated and used elsewhere, for example in chemical synthesis. For use as a fuel component in gasoline engines, it may be necessary to separate high-boiling components (preferably with a boiling point >220°C).

[0041] The oligomers or dimers can also be fully or partially hydrogenated. Methods for hydrogenating the oligomerized products to the corresponding paraffins are well known to those skilled in the art. In a preferred embodiment, the hydrogenation is carried out in the liquid phase using a solid catalyst insoluble in the hydrogenated product. The hydrogenation catalyst is preferably a supported catalyst made of an inorganic support containing platinum, palladium, and / or nickel as the active metal. The hydrogenation temperature is preferably 10 to 250°C, and the pressure is preferably 1 to 100 bar.

[0042] After hydrogenation, further fractions can be obtained by distillation. These fractions can be mixed with the unhydrogenated fraction to obtain fuel additives with specific properties. Additionally, some fractions can be used as solvents.

[0043] Process (e) In a subsequent step (e), the residual stream from step (d) is fed to a first separation unit, where a low-boiling stream comprising at least 1,3-butadiene, 1-butene, 2-butene and isobutane and an aqueous stream comprising at least alcohol, preferably methanol or ethanol, particularly preferably methanol and water, are obtained. Step (e) therefore particularly relates to the separation of alcohol, preferably methanol or ethanol, particularly preferably methanol, from C4-hydrocarbons.

[0044] The separation of the alcohol, preferably methanol or ethanol, particularly preferably methanol, from the residue stream is carried out by extraction, in particular with water or an aqueous solution as the washing medium. The alcohol, preferably methanol or ethanol, is therefore preferably washed from the residue stream in an extraction step with water or an aqueous solution. Preferably, an aqueous solution having a pH of 8 or higher, preferably between 8 and 12, is used. The pH can be adjusted, for example, by adding sodium hydroxide solution and / or sulfuric acid. This extraction can be carried out according to standard industrial processes, for example in an extraction column or in a cascade of mixers and separators. This extraction has various advantages, such as low investment costs and low operating costs. The separation yields an aqueous stream containing at least an alcohol, preferably methanol or ethanol, particularly preferably methanol and water, and a low-boiling stream containing at least 1,3-butadiene, 1-butene, 2-butene, and isobutane. The residual alcohol content in the low-boiling stream is preferably less than 0.2% by mass, particularly preferably less than 500 ppm by mass, and most preferably less than 50 ppm by mass.

[0045] The first separation unit for extracting alcohol, preferably methanol or ethanol, particularly preferably methanol, preferably comprises at least one extraction column. The at least one extraction column preferably has 2 to 25, particularly preferably 5 to 15, theoretical plates and is preferably operated at a temperature of 10 to 90°C and at a pressure of at least 0.1 MPa above the vapor pressure of C4-hydrocarbons. The mass ratio of the washing medium to the supplied residue stream is preferably 1:5 to 1:40. Preferably, the residue stream is transferred to an extraction column and fed countercurrently with the extractant through an inlet located at the top, with the extractant being charged with a water-containing stream which can be removed through an outlet at the bottom of the extraction column. The alcohol-containing wash water from the extraction, i.e., the aqueous stream, is reprocessed in step (f) and then at least partially recycled to the extraction.

[0046] Process (f) In step (f), the aqueous stream is fed to a recovery unit for at least partial separation of the alcohol, preferably methanol or ethanol, particularly preferably methanol, from the water, and at least a portion of the alcohol, preferably methanol or ethanol, particularly preferably methanol, thus obtained is recycled to the reaction unit of step (d). The water-containing stream can be treated in a recovery unit, for example by distillation, to obtain a substantially alcohol-free water fraction as a bottom product and methanol as an overhead product. The distillation is preferably carried out at pressures above atmospheric, for example, in the range of 1.1 to 1.5°C. The temperature at the bottom is preferably 110 to 140°C. The temperature at the top is 80 to 95°C. Separation of alcohol, preferably methanol or ethanol, from water is generally known to those skilled in the art. The alcohol, preferably methanol or ethanol, can be recycled to the ATBE synthesis or isobutene dimer production in step (d). The water fraction from the bottom can be recycled to the first separation unit in step (e) for reuse.

[0047] Process (g) The low-boiling stream is hydrogenated in step (g) to obtain a hydrogenated low-boiling stream in which at least a portion of the 1,3-butadiene contained therein has been hydrogenated. If trace amounts of butadiene have not already been removed prior to step (g), they can be removed from the residual stream by selective hydrogenation (SHP). The hydrogenation in step (g) can be carried out in the liquid phase over a palladium-containing fixed-bed catalyst using hydrogen with the addition of carbon monoxide as a moderator, where the hydrogen and carbon monoxide are completely dissolved in the hydrocarbon mixture. The amount of hydrogen added is equal to or greater than the amount stoichiometrically required to hydrogenate the polyunsaturated compounds to simple olefins, which can be calculated from the composition of the low-boiling stream to be hydrogenated. The amount of CO added relative to the mass of the low-boiling stream is at least 0.05 to 100 ppm by mass. Amounts above 20 ppm generally do not result in further improvement of the hydrogenation result, so amounts of 0.05 to 10 ppm by mass are preferred. The optimum amount of CO added for a given process can easily be determined experimentally, as described in German Patent No. 31 43 647.

[0048] The catalyst contains 0.1 to 2 mass% of palladium and / or platinum supported on a carrier. Examples of such carriers include alumina (aluminum oxide), silica gel, aluminosilicate, and activated carbon. It is preferable to use a hydrocarbon amount in the range of 5 to 300 liters per liter of catalyst used. The temperature at which the hydrogenation is carried out is between 0 and 75° C. Advantageously, the hydrogenation is carried out at a higher temperature than the extraction in process step (e), in order to avoid the formation of free water.

[0049] The process pressure must be high enough to maintain the liquid phase at the desired temperature and to dissolve sufficient amounts of hydrogen and carbon monoxide. The reaction pressure is less than 20 MPa, preferably less than 6 MPa, and preferably less than 2 MPa. A typical reaction pressure is 1.5 MPa.

[0050] The hydrogenation can be carried out in a single or multi-stage manner. Single stage means that only a single reactor is used. Multi-stage means that multiple reactors are present. For cost reasons, a single-stage design is preferred. Alternatively, the hydrogenation can be carried out in multiple stages, preferably two stages. Hydrogen is fed upstream of each reactor, and carbon monoxide is preferably fed to the first reactor. The reactors can be operated with product recycle. In a preferred embodiment, at least a portion of the 1,3-butadiene is hydrogenated in at least two reaction stages, with at least the last reaction stage being carried out in the presence of 0.05 to 100 ppm by weight of CO.

[0051] Process (h) The hydrogenated low-boiling stream obtained in step (g) contains at least n-butane, isobutane, 1-butene, and 2-butene (cis and trans), with only minor amounts of 1,3-butadiene and / or isobutene, if any, at the ppm level. The hydrogenated low-boiling stream is then sent to a second separation unit in step (h), where a stream D containing at least isobutane and 1-butene and a stream E containing at least n-butane and 2-butene are obtained. The separation into streams D and E is preferably carried out by distillation.

[0052] Isobutane and 1-butene can be completely or partially separated by distillation from the hydrogenated low-boiling stream, also referred to in the literature as raffinate II, as stream D. A further stream E, also referred to as raffinate III, usually contains mainly 2-butene, n-butane and any amount of 1-butene. Stream E leaves the process and can be used, for example, as a feed mixture for oligomerization. The distillative separation can be carried out in equipment typically used for the separation of such hydrocarbon mixtures, for example in distillation or fractionation columns.

[0053] In a preferred embodiment, the distillation separation is carried out in an ultra-fractionation column. The feed to this ultra-fractionation column is preferably carried out in the lower half, preferably the lower third, of the ultra-fractionation column. Due to the narrow boiling point range of the mixtures to be separated, step (h) is preferably carried out in an ultra-fractionation column with more than 100 plates, preferably more than 125 plates, particularly preferably more than 150 plates, and particularly preferably 150 to 200 theoretical plates. The ultra-fractionation column can be designed as a packed column or a tray column. A tray column is preferred.

[0054] The reflux ratio in the ultrafractionation column (reflux volume vs. distillate removal volume) is preferably not more than 20, preferably less than 14, particularly preferably less than 11, depending on the number of plates used and the operating pressure. Condensation can be carried out against cooling water or air. The condensation energy can be utilized, for example, by vapor recompression or a heat pump. The distillation vessel is preferably designed as a liquid separator. This allows the water present in the feed stream to be separated as a second phase in the distillation vessel, resulting in a technically water-free bottom product (stream E). The separation in process step (h) is preferably carried out at an absolute pressure of 0.4 to 1.0 MPa, more preferably 0.5 to 0.7 MPa. The temperature at which the separation is carried out is preferably 35 to 80°C, more preferably 40 to 65°C.

[0055] The column for separating the mixture of substances usually comprises at least one evaporator through which the energy required to accomplish the separation task is introduced. To heat the evaporator of the hyperfractionation column used in step (h), conventional heat transfer media, such as steam or hot water, can be used, preferably waste heat from other processes. In the latter case, it can be advantageous to equip the column with several evaporators. The ultra-fractionation column is preferably configured as a simple column with at least one evaporator and at least one condenser. Due to the high energy consumption and the small temperature difference between the bottom and the top of the column, an energy-saving configuration is a particularly preferred embodiment. By way of example, reference is made here to a vapor recompression process. A particularly preferred further configuration is a double-pressure circuit (double-effect distillation configuration) integrated with a second column. In this case, one column is operated at a high enough pressure that its condensation temperature heats the other column. When columns with different separation tasks are thermally interconnected, in principle, any suitable column of the process according to the invention, as well as columns present at a plant site external to the process according to the invention, can be interconnected with the column of step (h). Particularly preferably, the second column is at least one column of the subsequent step (i). Even more preferably, the pressure of the ultra-fractionation column of this step (h) is higher, since a simpler separation task is achieved here.

[0056] Process (i) Stream D is then fed in step (i) to a third separation unit, where a crude isobutane stream and a high purity 1-butene stream are obtained in the third separation unit. In this step, 1-butene is separated from the isobutane in stream D. The separation is preferably carried out by distillation. The separation in step (i) produces a high purity 1-butene stream having a 1-butene content of at least 99% by mass relative to the total 1-butene stream. In a preferred embodiment, the purity of the 1-butene stream is greater than 99.2% by mass, more preferably greater than 99.3% by mass, even more preferably greater than 99.4% by mass, and particularly preferably greater than 99.5% by mass, based on the total 1-butene stream. More preferably, the 1-butene stream preferably contains less than 5000 ppm by mass, preferably less than 2000 ppm by mass, and particularly preferably less than 1500 ppm by mass of isobutene. In a preferred embodiment, 1-butene is separated in at least one distillation column, which gives highly pure 1-butene as the bottom product, and a crude isobutane stream, optionally containing low boilers (e.g., C3 hydrocarbons), is obtained as the overhead product and fed to step (j).

[0057] The separation in step (i) is preferably carried out in an ultra-fractionation column. The feed to this ultra-fractionation column is preferably fed into the upper half of the column, preferably into the upper half. Due to the narrow boiling range of the mixtures to be separated, the ultra-fractionation column is preferably designed with a theoretical plate number of at least 100 plates, preferably at least 125 plates, particularly preferably at least 150 plates, and particularly preferably between 150 and 200 plates. The ultra-fractionation column can be designed as a packed column or a tray column. Preferably, it is a tray column. The reflux ratio (reflux volume vs. distillate removal volume) is preferably less than 100, preferably less than 70, particularly preferably less than 60, depending on the number of plates used and the operating pressure. The reflux ratio is particularly preferably 30 to 60. Condensation can be carried out against cooling water or air. The distillation vessel is preferably designed as a liquid separator. This allows the water present in the feed stream to separate as a second phase in the distillation vessel, resulting in a technically water-free bottom product.

[0058] A column for separating a mixture of substances usually includes at least one evaporator through which the energy required to accomplish the separation task is introduced. To heat the column's evaporator, a conventional heat transfer medium, such as steam or hot water, or preferably waste heat from other processes, can be used. In the latter case, it may be advantageous to equip the column with multiple evaporators. The ultra-fractionation column is preferably configured as a simple column with at least one evaporator and at least one condenser. Due to the high energy consumption and the small temperature difference between the bottom and the top of the column, an energy-saving configuration is a particularly preferred embodiment. By way of example, reference is made here to vapor recompression processes. A particularly preferred further configuration is a double-pressure circuit (double-effect distillation configuration) integrated with a second column. In this case, one column is operated at a high enough pressure so that its condensation temperature heats the other column. When columns with different separation tasks are thermally interconnected, in principle, any suitable column of the process according to the invention, as well as columns present at a plant site external to the process according to the invention, can be interconnected with the column according to the invention in step (f). Particularly preferably, the ultra-fractionation column of step (i) is the second column, and the column of step (h) is the first column. In this case, one column, preferably the first column, is operated at a high enough pressure so that its condensation temperature heats the other column.

[0059] In this preferred embodiment of process step (i) according to the invention, in the first distillation column, the low boilers present in stream D are first separated off as an overhead product, and a mixture comprising mainly 1-butene and isobutane is obtained at the bottom of the column. In the second column, which can be designed similarly to the hyperfractionation column described above, this bottom mixture can be separated into 1-butene, which is obtained as a bottom product, and an isobutane-rich fraction (overhead product).

[0060] The high-purity 1-butene produced by the process according to the invention is a sought-after intermediate. For example, it can be used as a comonomer in the production of polyethylene (LLDPE or HDPE) and ethylene-propylene copolymers. It is also used as an alkylating agent and is a starting material for the production of butan-2-ol, butene oxide, and valeraldehyde. A further use of the substantially isobutene-free 1-butene produced according to the invention is in the production of n-butene oligomers, particularly by the Octol process. In another embodiment, step (i) can be followed by hydrogenation to hydrogenate trace olefins to the corresponding alkanes. This hydrogenation of trace olefins is known to those skilled in the art.

[0061] Process (j) The crude isobutane stream separated in step (i) is fed to a fourth separation unit, which produces an off-gas stream and a high-purity isobutane stream. Preferably, the isobutane obtained during the workup has an isobutane purity of at least 95% by mass, more preferably greater than 95.2% by mass, even more preferably greater than 95.3% by mass, even more preferably greater than 95.4% by mass, particularly preferably greater than 95.5% by mass, and a total butane content (n-+isobutane) of at least 99.5% by mass, preferably 99.6% by mass, particularly preferably 99.7% by mass. The high-purity isobutane stream further preferably contains less than 1000 ppm by mass, particularly preferably less than 200 ppm by mass, of olefins. The high-purity isobutane stream further preferably contains less than 100 ppm by mass, particularly preferably less than 10 ppm by mass, of oxygenates such as dimethyl ether or methanol. The distillation is preferably carried out at positive pressure, preferably in the range of 8 to 12 bar. The temperature at the bottom of the distillation column is preferably in the range of 65 to 85°C. The temperature at the top of the distillation column is preferably in the range of 60 to 80°C.

[0062] A further aspect of the invention is an apparatus for carrying out the process according to the invention for producing high-purity 1-butene and high-purity isobutane, comprising an isobutane separation unit (12) comprising at least one distillation column for separating at least a portion of the isobutane present in stream A; a reaction unit (14) comprising at least one reactor in which at least a portion of the isobutene present in stream C is converted to MTBE and / or isobutene dimer; a first separation unit (15) comprising at least one distillation column in which a low-boiling stream comprising at least 1,3-butadiene, 1-butene, 2-butene and isobutane is separated. a recovery unit (17) for recovering methanol; a hydrogenation unit (18) comprising at least one hydrogenation reactor, in which at least a portion of the 1,3-butadiene present in the low-boiling stream is selectively hydrogenated; a second separation unit (20) comprising at least one distillation column for separating a stream D comprising at least isobutane and 1-butene; a third separation unit (22) comprising at least one distillation column for separating high-purity 1-butene; and a fourth separation unit (24) comprising at least one distillation column for separating high-purity isobutane.

[0063] The present invention will be described with reference to the flow diagram of Figure 1. However, the representations shown in this figure should be understood as illustrative rather than limiting. Figure 1 shows a flow diagram of the present invention. A first C4 hydrocarbon stream (A) is fed to an isobutane separation unit (12), where at least a portion of the isobutane present in stream A is separated to form an isobutane-reduced stream. The isobutane-reduced stream is mixed with a second C4 hydrocarbon stream (B) to obtain stream (C), which is fed to a reaction unit (14). The isobutene present is at least partially reacted with an alcohol, preferably methanol or ethanol, particularly preferably methanol, to produce ATBE (alkyl tert-butyl ether), preferably MTBE (methyl tert-butyl ether) or ETBE (ethyl tert-butyl ether), particularly preferably MTBE (methyl tert-butyl ether) and / or isobutene dimer. The reaction unit (14) also comprises a product separation unit (not shown). The reaction effluent is subjected to product separation to obtain a residue stream containing at least alcohol, preferably methanol or ethanol, particularly preferably methanol, 1,3-butadiene, 1-butene, 2-butene, and isobutane, and a product stream containing at least MTBE and / or isobutene dimer. The product stream is discharged, and the residue stream is sent to a first separation unit (16) to obtain a low-boiling stream containing at least 1,3-butadiene, 1-butene, 2-butene, and isobutane, and an aqueous stream containing at least alcohol, preferably methanol or ethanol, particularly preferably methanol and water. In a recovery unit (17), the alcohol, preferably methanol and ethanol, particularly preferably methanol, is at least partially separated from the water, and at least a portion of the resulting alcohol, preferably methanol or ethanol, particularly preferably methanol, is recycled to the reaction unit (14). Water can be recycled to the first separation unit (16), as indicated by the dashed line. The low boiling stream from the first separation unit (16) is fed to a hydrogenation unit (18) where the 1,3-butadiene is selectively hydrogenated to provide a hydrogenated low boiling stream.The hydrogenated low-boiling stream is then fed to a second separation unit (20), which produces a stream D containing at least isobutane and 1-butene, and a stream E containing at least n-butane and 2-butene. Stream E is discharged, and stream D is fed to a third separation unit (22), which produces a crude isobutane stream and a high-purity 1-butene stream. The crude isobutane stream is processed in a fourth separation unit (24), which produces a waste gas stream and a high-purity isobutane stream.

Claims

1. A method for producing high-purity 1-butene and high-purity isobutane, comprising: (a) providing a first C4 hydrocarbon stream A and a second C4 hydrocarbon stream B, wherein the two streams A and B each contain at least 1,3-butadiene, isobutene, isobutane, 1-butene, and 2-butene, and the concentration of isobutane in said stream A is greater than the concentration of isobutane in said stream B; (b) feeding said stream A to an isobutane separation unit, wherein at least a portion of the isobutane present in said stream A is separated to form an isobutane-depleted stream; (c) separating a portion of said isobutane-depleted stream and combining this portion with said stream B to obtain stream C; (d) providing said stream C to a reaction unit to feed alcohol, alternatively methanol or ethanol, to convert at least a portion of the isobutene present in said stream C to ATBE (alkyl tert-butyl ether), MTBE (methyl tert-butyl ether) or ETBE (ethyl tert-butyl ether) and / or isobutene dimer, and obtaining a reaction effluent, wherein said reaction effluent is subjected to product separation to produce a residue stream comprising at least alcohol, alternatively methanol or ethanol, 1,3-butadiene, 1-butene, 2-butene, and isobutane, and a product stream comprising at least ATBE (alkyl tert-butyl ether), MTBE (methyl tert-butyl ether) or ETBE (ethyl tert-butyl ether) and / or isobutene dimer; (e) feeding the residue stream to a first separation unit, and obtaining in the first separation unit a low-boiling stream containing at least 1,3-butadiene, 1-butene, 2-butene, and isobutane, and an aqueous stream containing at least the alcohol, or methanol or ethanol, and water; (f) feeding the aqueous stream to a recovery unit to at least partially separate the alcohol, or methanol or ethanol, from water, and recycling at least a portion of the resulting alcohol, or methanol or ethanol, to the reaction unit; (g) feeding said low boiling stream to a hydrogenation unit to hydrogenate at least a portion of the 1,3-butadiene present thereby obtaining a hydrogenated low boiling stream; (h) feeding the hydrogenated low-boiling stream to a second separation unit to obtain in the second separation unit a stream D comprising at least isobutane and 1-butene, and a stream E comprising at least n-butane and 2-butene; (i) feeding said stream D to a third separation unit, wherein said third separation unit provides a crude isobutane stream and a high purity 1-butene stream; and (j) feeding the crude isobutane stream to a fourth separation unit, and obtaining an off-gas stream and a high purity isobutane stream in the fourth separation unit; A method comprising:

2. 2. The process of claim 1, wherein the isobutane-depleted stream from (b) is subjected to removal of high boilers and / or removal of nitrogen-containing impurities and / or sulfur-containing impurities and / or oxygen-containing impurities before being fed to (c).

3. 3. The method of claim 1 or 2, wherein separating at least a portion of the isobutane-depleted stream in (c) is performed via a flow control valve.

4. 4. The process according to claim 1, wherein the conversion in (d) is carried out in at least two reaction stages, with at least the last reaction stage being carried out as a reactive distillation.

5. 5. The method of claim 1, wherein in (e), methanol is washed out of the residue stream by extraction with water or an aqueous solution.

6. 6. The method according to claim 1, wherein the hydrogenation of at least a portion of the 1,3-butadiene in (g) is carried out in at least two reaction stages, with at least the last reaction stage being carried out in the presence of 0.05 to 100 ppm by weight of CO.

7. The process according to any one of claims 1 to 6, wherein the conversion of isobutene in (d) is greater than 70%, or greater than 90%.

8. The method according to any one of claims 1 to 7, wherein an ion exchange resin is used as a catalyst for the conversion of isobutene in (d).

9. The method according to any one of claims 1 to 8, wherein the purity of the high-purity 1-butene obtained in (i) is at least 99%.

10. The method according to any one of claims 1 to 9, wherein the high-purity 1-butene obtained in (i) contains less than 5000 ppm by mass of isobutene.

11. The method according to any one of claims 1 to 10, wherein the purity of the high-purity isobutane obtained in (j) is at least 99%.

12. The method according to any one of claims 1 to 11, wherein the high-purity 1-butene obtained in (i) contains less than 1000 ppm by mass of olefins.

13. The process according to any one of claims 1 to 12, wherein the first separation unit and / or the third separation unit and / or the fourth separation unit comprises at least one distillation column.

14. An apparatus for carrying out the method according to any one of claims 1 to 13, comprising: an isobutane separation unit (1) comprising at least one distillation column for separating at least a portion of the isobutane present in said stream A; a reaction unit (2) comprising at least one reactor in which at least a portion of the isobutene present in stream C is converted into MTBE and / or isobutene dimer; a first separation unit (3) comprising at least one distillation column in which a low-boiling stream comprising at least 1,3-butadiene, 1-butene, 2-butene and isobutane is separated; a recovery unit (4) for recovering methanol; a hydrogenation unit (5) comprising at least one hydrogenation reactor, in which at least a portion of the 1,3-butadiene present in said low-boiling stream is selectively hydrogenated; a second separation unit (6) comprising at least one distillation column for separating stream D comprising at least isobutane and 1-butene; a third separation unit (7) for separating high-purity 1-butene, comprising at least one distillation column; and a fourth separation unit (8) comprising at least one distillation column for separating high purity isobutane; 1. An apparatus comprising:

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