DE19740895A1 - Production of propene and 1-butene - Google Patents

Abstract

Production of propene and 1-butene comprises reading 2-pentene with ethene in the presence of a metathesis catalyst containing a VIb, VIIb or VIIIb metal. An apparatus for carrying out the process is also claimed comprising a metathesis reactor (R1) to react 1-butene with 2-butene, connected to a distillation column (D1) to separate 2-3C light boiling, 4C middle boiling and 5C high boiling phases. The light boiling outlet loads to a column (D3) for separating ethene and propene, the middle boiling outlet leads to the reactor (R1) or is discharged, and the high boiling outlet leads to a reactor (R2) for reacting 2-pentene with ethene, whose outlet leads into a column (D1). The ethene outlet from the column (D3) and an ethene feed are led to the reactor (R2).

Description

The invention relates to a process for the production of propene by Me tathesis of olefins.

In its simplest form, olefin metathesis (disproportionation) describes the reversible, metal-catalyzed transalkylidation of olefins by breaking and reforming C = C double bonds. For example, olefins of the formulas R ¹ CH-CH-R ² and R ³ -CH-CH R ^{4 are} reversibly converted to olefins of the formulas R ¹ CH-CH-R ³ and R ² -CH-CH R ⁴ . In the metathesis of acyclic olefins, a distinction is made between self-metathesis, in which an olefin merges into a mixture of two olefins with different molar masses, and cross or co-metathesis, in which two different olefins react. An example of a self-metathesis is the conversion of two molecules of propene to ethene and 2-butene, as is carried out, for example, using the Phillips triolefin method, see Hydrocarbon Processing, Volume 46, No. 11, November 1967, p. 232. An example of a cross metathesis is the conversion of propene and 1-butene to ethene and 2-pentene. If one of the reactants is ethene, this is usually referred to as ethenolysis.

The metathesis reactions take place in the presence of catalysts. For this in principle, homogeneous and heterogeneous transition metal compounds are suitable, especially those of subgroup VI to VIII of the periodic table  of the elements, as well as homogeneous and heterogeneous catalyst systems, in de NEN these compounds are included.

From DE-A-19 40 433 the metathesis of 1-butene with 2-butene to propene and 2-pentene is known, wherein Re ₂ O ₇ / Al ₂ O _{3 is used} as a catalyst. The 2-pentene formed is further reacted with sodium hydride on potassium carbonate and ethene to form heptenes.

The methathesis of 1-butene and 2-butene to propene and 2-pentene is described in K.L. Anderson, T.D. Brown, Hydrocarbon Processing, Vol. 55, No. 8, Au gust 1976, pp. 119-122 as a side reaction in the synthesis of isoamylene guided.

EP-A-0 304 515 describes a metathesis process for converting 1-butene with 2-butene to propene and pentenes, which can be carried out in a reactive distillation apparatus using Re ₂ O ₇ / Al ₂ O ₃ as a catalyst.

The metathesis of 1-butene with 2-butene to propene and pentene is known from US Pat. No. 3,526,676. It is carried out on MoO ₃ and CoO on Al ₂ O ₃ .

From US 3,785,957 a method for producing fuel with high octane number is known. In this case, an olefinic fuel is disproportionated to ethylene and the effluent separated into a stream of propylene, a butene stream, a C ₅ - or C ₅ - ₆ olefin stream and a C ₆ - or C _{7 +} - fuel stream. The C ₅ or C ₅₆ olefin stream is disproportionated with ethene over a fixed bed WO ₃ / SiO ₂ catalyst to obtain propylene and butenes. The propylene obtained is disproportionated to ethylene and butene and the butenes are alkylated with isobutane.

A process for increasing the octane number of fuel is known from US Pat. No. 3,767,565, a C _{5 section of} an olefinic fuel being reacted with ethylene in the presence of a catalyst composed of WO ₃ / SiO ₂ and MgO to give ethylene, propylene, n-butenes and isobutenes. The propylene obtained is disproportionated and the n-butenes obtained are alkylated with isobutane.

EP-A1-0 691 318 discloses an olefin metathesis process in which C ₅ olefins and ethylene are converted to mixed C ₄ olefins and propene in the presence of a catalyst. So 2-methyl-2-butene is reacted with ethene to give isobutene and propene. A mixture of 2-pentenes and 2-methyl-2-butene is converted to a mixture of 1-butene, isobutene and propene.

A process for the production of propene in high yield by conversion The production of 1-butene and 2-butene is not known.

A process for the production of propene in high yield from 2-butene without using an excess of ethene is not known.

An object of the invention is to provide a method for manufacturing Provision of propene in high yield from 1-butene and 2-butene.

Another object of the present invention is to provide a Process for the production of propene from 2-butene, in which not with egg excess ethene must be worked.

Another object of the present invention is to provide a process for the production of propene from low-butene C ₄ streams with as little ethene requirement as possible.

Another object of the present invention is to provide a Process for the production of propene and 1-butene from 2-pentene.

According to the invention, the objects are achieved by a method for manufacturing Provision of propene and 1-butene by reacting 2-pentene with ethene in the presence of a metathesis catalyst containing at least one compound a metal of VIb, VIIb or VIII subgroup of the periodic table of Contains items.

The 2-pentene is preferably obtained by reacting 1-butene and 2-butene to propene and 2-pentene in the presence of the above metathesis catalyst and separation of the 2-pentene obtained.

The method according to the invention comprises 2 metathesis steps. In the first Step 1-butene and 2-butene are converted to propene and 2-pentene. In A second step then turns 2-pentene with ethene to 1-butene and propene implemented. The 1-butene is according to an embodiment of the invention thereby returned to the first reaction step.

The net reaction is the conversion of 2-butene with ethene to 2 molecules of propene. When implementing 2-pentene with ethene according to one embodiment of the invention, formally only equimolar amounts of input materials needed to produce the products with high yield reach. Thus, in contrast to the reverse trio-olefin process the amount of ethene used is kept low.

Both metathesis steps can be carried out as reactive distillation, such as it is described below.  

1-butene and 2-butene can be used in the reaction as pure substances according to one embodiment of the invention. According to another embodiment of the invention, the butenes are used in the form of a C ₄ stream which originates, for example, from a cracker, in particular a steam cracker, or from a refining. The C ₄ stream can contain in addition to the butenes C ₄ alkanes. According to one embodiment of the invention, a C ₄ stream is used which consists of raffinate II. Raffinate II is a fraction of 1-butene, cis / trans-2-butene, isobutene and n-butane and isobutane. For example, raffinate II can contain 80-85% by weight of olefins and 15-20% by weight of butanes, with for example 25-50% by weight of 1-butene, 30 to 55% by weight of 2-butene, a maximum of 1- 2% by weight of isobutene. According to one embodiment of the invention, the C ₄ stream used has a butenes content of 20 to 100, preferably 50 to 90, in particular 70 to 90% by weight. The ratio of 1-butene to 2-butene is 10: 1 to 1:10, preferably 3: 1 to 1: 3, in particular 2: 1 to 1: 2. According to one embodiment of the invention, the C ₄ flow can be low Contain quantities of other hydrocarbons.

According to one embodiment of the invention, everyone can be used as starting material Electricity can be used that contains 1-butene and 2-butene. According to one Embodiment of the invention can 1-butene from the Invention according to the synthesis itself and mixed with supplied 2-butene become.

The C ₄ feed stream used is preferably pre-cleaned before use in the process according to the invention in order to remove any traces of water, oxygen or oxygenates, sulfur or sulfur-containing compounds, nitrogen, phosphorus or halogen, especially chlorides. The removal is preferably carried out by passing the C ₄ feed stream over absorber materials, such as zeolites and zeolite-analogous phosphates, high-surface oxides of silicon, aluminum, titanium, zirconia, bleaching agents, clays, hydrotalcites, high-surface phosphates, activated carbon and carbon molecular sieves, and also organic polymers and Ion exchange resins, preferably NaX molecular sieve. The absorber materials are preferably in the form of a protective bed.

Applicable methods for adsorption and adsorptive purification are described for example in W. Kast, adsorption from the gas phase, VCH, Weinheim (1988). The use of zeolitic adsorbents is explained in DW Breck, Zeolite Molecular Sieves, Wiley, New York (1974). The removal of specifically acetaldehyde from C ₃ to C ₁₅ hydrocarbons in the liquid phase is described in EP-A-0 582 901. The methods listed in the above literature can be used in the present case. For example, the educt stream is preferably brought into contact with the adsorbents in the gaseous, liquid or supercritical phase.

In addition to the conversion of 1-butene and 2-butene to propene and 2-pentene can receive a small amount of 3-hexene and ethene as a by-product become. In addition, small amounts of higher-boiling compounds can also be used available.

The small amounts of by-products according to one embodiment of the invention 1 to 20 wt .-%, preferably 1 to 5 wt .-%, based make up the amount of 2-pentene formed, interfere with the successor not sufficient implementation, so that according to one embodiment of the inven no cleaning of the 2-pentene from these by-products before further implementation is required. According to one embodiment of the Er the 2-pentene is used in pure form in the second implementation puts.  

Such mixtures are thus also used under the expression "2-pentene" stood, in addition to 2-pentene small amounts of hexenes, in particular 3-hexene, and other higher-boiling compounds.

Accordingly, the term "butenes" such as "1-butene" and "2-butene" is also understood to mean a mixture which, in addition to the butene or the butenes, contains C ₄ alkanes, in particular butanes.

Several embodiments of the invention are described below with reference to the Drawing explained in the

Fig. 1 shows a schematic representation of one embodiment of the process OF INVENTION dungsgemaßen,

Fig. 2 shows a further embodiment of the method according to the invention and

Fig. 3 shows a further embodiment of the method according to the invention.

The abbreviations used in the figures mean the following:
1-Bu: 1-butene
2-Bu: 2-butene
Bu: butanes
Et: Ethen
Pr: propene
2-pe: 2-pentene
3-He: 3-witches
H: high boiler
II: Raffinate II
C4: C4 olefins
C5⁺: olefins with 5 or more carbon atoms
R1: reactor
R2: reactor
D1: distillation column (if a vertical line is provided under D1, it is a dividing wall column)
D2: column (if a vertical line is provided under D2, it is a dividing wall column)
D3: distillation column.

An embodiment of the method according to the invention is described below, comprising

• a) Conversion of 1-butene and 2-butene to propene and 2-pentene in counter were a metathesis catalyst that has at least one compound of a Metals VIb, VIIb or VIII subgroup of the periodic table of the Ele contains elements,
• b) subsequent separation of the propene and 2-pentene formed,
• c) subsequent reaction of the 2-pentene with ethene to propene and 1-Bu ten in the presence of a metathesis catalyst which has at least one ver Binding of a metal from subgroup VIb, VIIb or VIII of Perio contains the system of the elements,
• d) subsequent separation of the propene and 1-butene formed,
• e) subsequent recycling of the 1-butene formed in step a).

This embodiment is shown in FIG. 1.

In a first reactor R1, 1-butene and 2-butene are converted to propene and 2-pentene in the presence of the metathesis catalyst according to the invention. For this purpose, a raffinate II stream is fed into the reactor. The reactor is followed by a distillation column D1, at the top of which propene and ethene formed as a by-product are removed. Unreacted raffinate II is removed in the middle deduction. It can also be partially returned to the reactor R1 (not shown in FIG. 1). 2-pentene and by-product 3-hexene and high boilers are removed from the bottom of D1. The sump is then fed together with fed ethene to a reactor R2, which in turn contains a metathesis catalyst according to the invention. The reaction of 2-pentene with ethene to 1-butene and propene takes place in this reactor R2. The discharge from reactor R2 is fed to a distillation column D2, at the top of which propene and unreacted ethene are removed. Formed 1-butene is discharged in the center draw and preferably at least partially returned to the reactor R1. Unreacted 2-pentene and 3-hexene and high boilers are obtained as by-products in the bottom of D2. These are preferably returned to the reactor R2. The mixtures of propene and by-product ethene removed at the top from D1 and D2 are separated in a further distillation column D3. At the top of D3, ethene is obtained, which is preferably led into the reactor R2 (back) (not shown in FIG. 1), or is discharged as a co-crack feed. The propene obtained in the bottom of D3 is the desired implementation product of the process according to the invention. D1 and D2 are laid out so that a low-boiling phase, in particular a C _2/3 phase, which contains ethene and propene, is removed at the top of the column. C ₄ streams, in particular butenes and butanes, are discharged as medium boiler. C _{≧ 5} hydrocarbons are discharged in the bottom phase.

Reactors R1 and R2 can be any suitable reactor. she can be used for the continuous or discontinuous reaction. Thus, according to one embodiment, they can be pressure vessels, such as pressure glass vessels, according to a further embodiment, be tubular reactors.

According to one embodiment of the invention, the total turnover is in R1 20 to 90, preferably 50 to 80%.

According to one embodiment of the invention, the total turnover is in R2 20 to 100, preferably 60 to 90%.

The reaction in R1 preferably takes place in the liquid phase. Here pressure and temperature are chosen so that the reactants in the liquid phase remain.

According to one embodiment of the invention, the temperature is in R1 0 to 150 ° C, preferably 20 to 80 ° C. According to one Embodiment of the invention 2 to 200 bar, preferably 5 to 20 bar. The implementation in R2 (ethenolysis) is carried out according to one embodiment of the Invention at temperatures from 0 to 150 ° C, preferably 20 to 80 ° C. under an ethene pressure of 5 to 200 bar, preferably 30 to 80 bar carried out. Ethene can be replenished continuously so that a constant pressure is maintained.

The implementations in R1 and R2 can last for a time of one second up to 10 hours, preferably 1 to 60 minutes.

The distillation columns D1 and D2 are, according to one embodiment of the invention, those columns which allow a hydrocarbon stream to be separated into C _2/3 streams, C ₄ streams and C ₅ streams. The columns can be designed as dividing wall columns. According to one embodiment of the invention, D3 is a column which allows the separation of ethene and propene. According to one embodiment of the invention, the reactor R1 is combined with the distillation column D1 to form a reactive distillation device. The reaction takes place directly in the distillation column. The catalyst is present in the reaction column, so that the distillation is carried out simultaneously with the reaction or immediately afterwards. A corresponding method is known under the designation "reactive distillation".

According to one embodiment, reactor R2 and distillation column are D2 combined into a reactive distillation device, during the implementation and distillation are combined according to that described above Reactive distillation.

According to one embodiment of the invention, both implement reaction cracks tion in reactive distillation devices. In both implementations han it is about equilibrium reactions, so that according to an execution form of the invention the process products to achieve a possible high sales are removed from the balance as quickly as possible. This is particularly the case when using reactive distillation devices possible.

Instead of a normal distillation column D1, a dividing wall column can be provided. Such a method is shown in FIG. 2. The illustrated method is also modified compared to the method shown in FIG. 1.

As in the embodiment described above, a metathesis is carried out on a heterogeneous metathesis catalyst in the reactor R1, raffinate II being used. The distillation column D1 is used to separate the reaction products formed in the metathesis. The distillation column D3 is used to separate ethene and propene. The reactor R2 is used to convert C ₅ ⁺ high boilers with ethene.

In contrast to the above embodiment, the distillation column D1 is designed as a dividing wall column. In addition, the medium boiler discharge from D1, which contains C ₄ -olefins and butanes, is partly returned to the feed stream of raffinate II. Since the distillation columns D1 and D2 have to deal with the same separation task, only one such distillation column D1 was provided in this embodiment. This can reduce the outlay on equipment. The reaction scheme was adapted accordingly: the high boiler discharge from D1 is fed into the reactor R2 or partially discharged. The discharge from the reactor R2 is fed into the distillation column D1. The reactor R2 is charged with ethene, on the one hand, from the low boiler discharge from the distillation column D3, and, on the other hand, by additionally introduced ethene. Propene as the main product and also C ₄ olefins and C ₅ ⁺ olefins are removed from the process.

FIG. 3 shows an embodiment of the method according to the invention which largely corresponds to the embodiment shown in FIG. 1. Column D2, like column D1, is designed as a dividing wall column.

In contrast to the process according to FIG. 1, the medium boiler discharge from D1, which contains C ₄ olefins and butanes, is partially discharged or combined with the medium boiler discharge from column D2 and returned to the reactor R1. The ethene obtained from the distillation column D3 is fed into the reactor R2 by the reaction with the C ₅ ⁺ fraction. In turn, propene as the main product and parts of the C ₄ olefin fraction and butanes as well as the C ₅ Fraktion fraction are removed from the distillation column D2 (also as a co-crack feed).

CATALYST

All suitable metathesis catalysts can be used in the process of the invention sensors are used.

According to one embodiment of the invention, the catalyst is a hetero gener catalyst, especially a supported catalyst. According to one embodiment Form of the invention, the catalyst contains at least one compound a metal of VIb, VIIb or VIII subgroup of the periodic table of Elements. The catalyst preferably contains a ruthenium compound and / or rhenium compound.

According to one embodiment of the invention, the metal Connection around a metal oxide, partial oxide with additional orga present African residues or a carbonyl compound.

According to one embodiment of the invention, a homogeneous catalyst used. The catalyst is at least one compound of a Me talls of VIb, VIIb or VIII subgroup of the Periodic Table of the Elemen te. Rhenium or ruthenium is preferably used in the metal ver bonds.

According to one embodiment of the invention, ruthenium compounds used as described in WO 93/20111 and WO 96/04289.

According to a preferred embodiment of the invention RuX ₂ (CHR) (PR _{'3) 2 is} used, where the radicals R and R' are C _1-12 alkyl, preferably, C _{1- 6} -alkyl or C _6-12 -aryl radicals, R ^{1 is} particularly preferred to be a C ₃ -C ₈ -cycloalkyl radical, in particular C ₅ - or C ₆ -cycloalkyl radical, and X is a halide, such as chloride, bromide or iodide.

In particular, RuCl ₂ (= CHPh) (PCy ₃ ) _{2 is} used according to the invention, according to one embodiment of the invention as a solution, for example in methylene chloride.

The metal compound is preferably an oxide of rhenium, in particular Re ₂ O ₇ .

CARRIER

According to one embodiment of the invention, the catalysts according to the invention contain a support. In particular, inorganic carriers such as Al ₂ O ₃ , in particular γ-Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ , or mixtures thereof, such as SiO ₂ / Al ₂ O ₃ , B ₂ O _3, are used as carriers / SiO ₂ / Al ₂ O ₃ or Fe ₂ O ₃ / Al ₂ O ₃ .

According to one embodiment, the metal oxide content on the carrier is form of the invention 1 to 20 wt .-%, preferably 3 to 15 wt .-%, in particular 8 to 12 wt .-%, based on the total weight of the carrier catalyst.

Re ₂ O ₇ on Al ₂ O ₃ , SiO ₂ / Al ₂ O ₃ , SiO ₂ / Al ₂ O ₃ / Fe ₂ O ₃ or B ₂ O ₃ / Al ₂ O ₃ is preferably used as the catalyst. The proportion of metal oxide is preferably 1 to 20% by weight, particularly preferably 3 to 10% by weight. According to one embodiment of the invention, MeReO _{3 is used} instead of Re ₂ O ₇ or in a mixture with it.

Re ₂ O ₇ on Al ₂ O ₃ is particularly preferably used according to the invention.

According to one embodiment of the invention, the catalysts become fresh used calcined, with no further activation, for example  through alkylating agents. Deactivated catalysts can be invented according to by burning off coke residues, for example 550 ° C in the air stream and cooling under argon.

The reactions according to the invention can in the presence of a Lö solution, for example a hydrocarbon solvent become. According to a preferred embodiment of the invention the reactions carried out without added solvent.

The invention also relates to devices for carrying out the method described. . An apparatus for performing the method according to Figure 2 comprises a metathesis reactor (R1) for reacting 1-butene with 2-butene at the output of a distillation column (D1) for separating C _2/3 low-boiling, C ₄ - Medium boiler and C ₅ ⁺ high boiler phases are connected, which can be designed as a dividing wall column, the low boiler outlet into a column (D3) leading to the separation of ethene and propene, the middle boiler outlet leading to the reactor (R1) or to the discharge and the high boiler outlet into a reactor (R2) for the reaction of 2-pentene with ethene, the outlet of which leads to the column (D1), or the discharge, the ethene outlet leading from the column (D3) and an ethene feed into the reactor (R2).

. An apparatus for performing the method according to Figure 3 comprises a metathesis reactor (R1) for reacting 1-butene with 2-butene at the output of a distillation column (D1) for separating C _2/3 - low-boiling, C ₄ - Excludes medium boiler and C ₅ ⁺ high boiler phases, which can be designed as a dividing wall column, the low boiler outlet into a column (D3) leading to the separation of ethene and propene, the medium boiler outlet leading to the reactor (R1) or discharge, and the high boiler outlet leads into a reactor (R2) for the reaction of 2-pentene with ethene, at the output of which there is a distillation column (D2) for the separation of C _2/3 low-boilers, C ₄ -middles and C ₅ ⁺ high-boiling phases, which can be designed as a dividing wall column, the low boiler outlet leading to the column (D3), the middle boiler outlet leading together with the middle boiler outlet from (D1) to the reactor (R1) and the high boiler outlet leading to the discharge leads, the ethene exit from the column (D3) and an ethene feed into the reactor (R2).

The invention is explained in more detail below with the aid of examples.

EXAMPLES 1 TO 6 Batch synthesis of propene from raffinate II

50 ml of raffinate II (with egg ratio of 1-butene to 2-butene of 1: 2) with 10 g of a freshly cal cininated heterogeneous catalyst stirred at 60 ° C and 7 bar. The turned set catalysts are listed in Table 1 below. In Samples were taken at 5 minute intervals and gaschromato graphically examined. Below are those in the blend composition after 15 minutes of 1-butene conversions and Propene selectivities listed.  

TABLE

For all catalysts, propene selectivities with respect to 1-butene are at least 88%. In particular, the 3% Re ₂ O ₇ on Al ₂ O ₃ catalyst showed a selectivity of 93%. The conversion of 1-butene ranged from 38 to 85%.

EXAMPLE 7 Homogeneously catalyzed synthesis of propene from raffinate II

In a 100 ml pressure vessel, 50 ml of raffinate II (with a 1-butene-to-2-butene ratio of 1: 2) were mixed at room temperature with a solution of 31 mg (0.04 mmol) RuCl ₂ (= CHPh ) (PCy ₃ ) ₂ in 5 ml of methylene chloride. Samples were taken at intervals of 2 min and examined by gas chromatography. The 1-butene conversion after 10 minutes was 81%, the propene selectivity 90%.

EXAMPLE 8

The reaction mixtures obtained according to Examples 1 to 7 were separated by distillation, 2-pentene with 3-hexene being obtained as a by-product as a high-boiler discharge in the bottom. In a 100 ml pressure vessel, 50 ml of this high boiler discharge were treated with 50 bar ethene in the presence of 10 g of the 3% Re ₂ O ₇ / Al ₂ O ₃ catalyst from Example 2. The pressure was maintained by continuously repressing ethene at a temperature of 60 ° C. Samples were taken at intervals of 2 minutes and examined by gas chromatography. After 20 minutes, a mixture composition was established with

Conversion (2-pentene and 3-hexene) = 64%
Selectivity (1-butene and propene) = 96%.

From the above results it can be seen that the invention The process is very suitable for the production of propene from raffinate II Stream (2-butene and 1-butene).

EXAMPLE 9 Continuous synthesis of propene from raffinate II

Raffinate II was passed continuously at a temperature of 60 ° C. and a pressure of 10 bar at different dwell times over a flow tube equipped with a Re ₂ O ₇ / Al ₂ O ₃ heterogeneous contact. The catalyst from Example 1 was used. The reaction discharge was examined by gas chromatography after the expansion. The results are shown in the table below.

The space-time yields achieved are in the range around 200-2000 g Propene / 1 h.

EXAMPLE 10

The procedures according to Examples 1 to 9 were repeated, however the feed used contained about 40 to 50 ppm water and 60 to 80 ppm oxygenates. The feed was directly converted in a process variant sets, in a further process variant before the reaction in gaseous form passed over molecular sieve 13 × (Nax zeolite), water and oxygenates have been removed. The service life of the metathesis catalyst was when driving of the feed via molecular sieve 13 × by a factor of 10 to 20 compared to the first Process variant extended.

Claims (12)

1. Process for the production of propene and 1-butene by reaction of 2-pentene with ethene in the presence of a metathesis catalyst that at least one compound of a metal of VIb, VIIb or VIII Ne ben group of the periodic table of the elements contains. 2. The method of claim 1, wherein the 2-pentene is obtained by Conversion of 1-butene and 2-butene to propene and 2-pentene in counter were the metathesis catalyst defined in claim 1 and subsequently separating the 2-pentene. 3. Process for the production of propene

• a) converting 1-butene and 2-butene to propene and 2-pentene in the presence of a metathesis catalyst which contains at least one compound of a metal VIb, VIIb or VIII subgroup of the periodic system of the elements,
• b) subsequent separation of the propene and 2-pentene formed,
• c) subsequent reaction of the 2-pentene with ethene to propene and 1-butene in the presence of a metathesis catalyst which contains at least one compound of a metal from the VIb, VIIb or VIII subgroup of the Periodic Table of the Elements,
• d) subsequent separation of the propene and 1-butene formed,
• e) subsequent recycling of the 1-butene formed in step a).

4. The method according to claim 3, wherein step b) is a distillation which can be carried out in a dividing wall column in which a low-boiling phase containing propene, optionally a middle-boiling phase containing butenes and a bottom phase containing 2-pentene are obtained,
and or
wherein step d) is a distillation which can be carried out in a dividing wall column in which a propylene-containing low-boiling phase, a 1-butene-containing middle boiler phase and optionally a 2-pentene bottom phase are obtained, steps b) and d) in one Distillation column can be carried out. 5. The method according to claim 3 or 4, wherein the reaction in steps a) and / or c) is not carried out completely and in step b) and / or d) a C _2/3 containing low boiler phase, a C ₄ medium boiler phase and a C. _{≧ 5} sump phase are obtained,
the optionally combined low-boiling phases are separated by distillation into C ₂ and C ₃ phases and the C ₂ phase is returned in step c),
the possibly combined medium-boiling phases are at least partially returned in step a) and the optionally combined bottom phases are at least partially returned in step c). 6. The method according to any one of claims 2 to 5, wherein 1-butene and 2-butene are used as a mixture of a C ₄ stream, preferably from a cracker or a refinery, in particular as raffinate II, the C ₄ stream before the implementation for cleaning and removing traces of water, oxygen, sulfur, nitrogen, phosphorus or halogens can be passed over absorber materials. 7. The method of claim 6, wherein the ratio of mole fraction 1-Bu to the mole fraction of 2-butene, 10: 1 to 1:10. 8. The method according to any one of the preceding claims, wherein a homogeneous ner or heterogeneous metathesis catalyst is used, the Rhe contains nium or ruthenium compound, preferably a rhenium oxide on an inorganic carrier. 9. The method according to claim 8, wherein the metathesis catalyst contains Re ₂ O ₇ on an Al ₂ O _{3 support} or consists thereof, the rhenium oxide content being 1 to 20% by weight, preferably 3 to 10% by weight, based on the total weight of the catalyst. 10. The method according to any one of the preceding claims, wherein the implementation tion of 1-butene and 2-butene and / or the implementation of 2-pentene be carried out with ethene as a reactive distillation. 11. An apparatus for performing a method according to any one of claims 1 to 10, comprising a methathesis reactor (R1) for the implementation of 1-butene with 2 butene, at the output of which is a distillation column (D1) for separating C _2/3 -Lichttsieder-, C ₄ -Midsels- and C ₅ ⁺ high-boiling phases, which can be laid out as a dividing wall column, the low-boiler outlet leading to a column (D3) for the separation of ethene and propene, the medium boiler outlet to the reactor (R1) or leads to the discharge and the high boiler outlet into a reactor (R2) for the reaction of 2-pentene with ethene, the outlet of which leads to the column (D1), or to the discharge, the ethene outlet from the column (D3) and an ethene feed into the Run the reactor (R2). 12. An apparatus for performing a method according to any one of claims 1 to 10, comprising a methathesis reactor (R1) for the implementation of 1-butene with 2-butene, at the output of which is a distillation column (D1) for separating C _{2 /} Excludes ₃ low-boilers, C ₄ medium-boilers and C ₅ ⁺ high-boiling phases, which can be laid out as a dividing wall column, the low-boiler outlet leading to a column (D3) for separating ethene and propene, the middle boiler outlet to the reactor (R1) or leads to discharge, and the high boiler outlet leads to a reactor (R2) for the reaction of 2-pentene with ethene, at the outlet of which there is a distillation column (D2) for the separation of C _2/3 low-boilers, C ₄ medium-boilers and C ₅ ⁺ high boiler phases, which can be designed as a dividing wall column, the low boiler output leading to the column (D3), the middle boiler outlet together with the middle boiler outlet from (D1) to the reactor (R1) and the high boiler leads to the discharge, the ethene exit from the column (D3) and an ethene feed into the reactor (R2).