Energy efficient process for the oligomerization of olefins

Abstract

The invention relates to a process for the oligomerization of C2 to C8 olefins in at least two reaction stages, each comprising at least one reactor and at least one distillation column, and a separation stage comprising at least one distillation column, wherein the reaction heat and / or condensation energy is utilized by means of a heat transfer medium.

Description

[0001] The subject of this invention is a method for oligomerizing C2 to C8 olefins in at least two reaction stages and a subsequent separation stage, wherein each reaction stage comprises at least one reactor and at least one distillation column, and the separation stage comprises at least one distillation column, wherein reaction heat and / or condensation energy are utilized by means of a heat transfer medium.

[0002] Oligomerization typically refers to the reaction of unsaturated hydrocarbons with themselves to form correspondingly longer-chain hydrocarbons, known as oligomers. For example, an olefin containing six carbon atoms (hexene) can be formed by the oligomerization of two olefins containing three carbon atoms (propylene). The oligomerization of two molecules with each other is also called dimerization.

[0003] The resulting oligomers are intermediates, which are used, for example, in the preparation of aldehydes, carboxylic acids, and alcohols. Oligomerization of olefins is carried out on a large industrial scale in a homogeneous manner on a dissolved catalyst, heterogeneously on a solid catalyst, or through a two-phase catalyst system.

[0004] Oligomerization of olefins is well-known in existing technologies and is used on a large industrial scale. In Germany alone, annual production reaches thousands of tons. To achieve the highest possible conversion rate and the most continuous operation possible, industrial equipment typically comprises not just one, but multiple reaction stages in series, each containing at least one reactor. This allows the oligomerization process to continue operating even if one reaction stage fails.

[0005] The reaction stage also includes at least one distillation column to separate the oligomers formed from the olefins used. The feed stream containing the feed olefins is discharged from the top as distillate, and the oligomers depleted from the feed olefins are output from the bottom. The separation of the resulting oligomers after the reaction requires a significant energy input to the industrial equipment, such as heating steam, to heat the distillation column. In addition to the high cost of providing heating steam, this process control results in substantial CO2 emissions. Furthermore, several issues may arise when it is necessary to increase the reaction conversion rate. To improve the conversion rate and sustainably utilize the feed stream, the stream of depleted oligomers taken from the top of the distillation column could be at least partially returned to the first reaction stage. However, this stream must be processed again within the column after the reaction, resulting in additional energy usage in the form of heating steam.

[0006] The object of this invention is to provide a method for oligomerizing olefins that does not suffer from the aforementioned problems. This method should be able to operate cost-effectively and with reduced CO2 emissions, and operate resource-efficiently among possible measures to improve conversion rates.

[0007] The objective can be achieved by the method of the present invention for oligomerizing C2 to C8 olefins as described in claim 1. Preferred embodiments are shown in the dependent claims.

[0008] The method of the present invention is a method for oligomerizing C2 to C8 olefins in at least two reaction stages R1 and RL and a separation stage A1 following RL, wherein each reaction stage comprises at least one reactor and at least one distillation column, and the separation stage comprises at least one distillation column DKA1, wherein A feed mixture containing at least C2 to C8 olefins as reactant olefins is oligomerized in at least one reactor in the first reaction stage R1 using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKR1 in the first reaction stage R1 to obtain a residual stream RS1 containing at least unconverted reactant olefins and an oligomer product O1 containing at least the formed oligomers. RS1 is fed at least partially into the reactor for the subsequent reaction stage; The residual stream from the previous reaction stage is oligomerized in at least one reactor of the final reaction stage RL using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKRL of the final reaction stage RL to obtain a residual stream RSL containing at least unconverted reactant olefins and an oligomer product OL containing at least the oligomers formed. At least a portion of OL is fed into the distillation column DKA1 of the subsequent separation stage A1 and distilled there to obtain a dimer stream D1 consisting of at least 90% by weight of dimers of the reactant olefins used and a bottom stream S1 containing at least trimers and higher oligomers of the reactant olefins used. A dimer stream D1 is obtained at the top of DKA1, which is then condensed and partially returned to DKA1 as reflux, while a portion is discharged from the process. The energy generated during the condensation of the dimer stream D1 and the heat generated in at least one reactor of the first reaction stage R1 are at least partially transferred to the liquid or gaseous heat transfer medium W1 to form a heated heat transfer medium W1.1; and Energy from a heated heat transfer medium W1.1 is transferred to another liquid or gaseous heat transfer medium W2 to form a heated heat transfer medium W2.1, which is first compressed and / or heated, and then used to generate a vapor stream for heating at least distillation columns DKA1 and DKR1 through single-stage or multi-stage compression.

[0009] In this invention, the term "reaction stage" refers to a section of equipment that includes at least one reactor and at least one distillation column. Therefore, a reaction stage may include one or more reactors and one or more distillation columns located after said one or more reactors. In a preferred embodiment, each reaction stage has only one distillation column located after the reactor. More preferably, at least two reactors are arranged in the reaction stage, and particularly preferably exactly two reactors. These reactors may be connected in parallel or in series.

[0010] In the distillation columns of their respective reaction stages, the oligomers generated are separated from the remaining feed stream from the reactor (which, for example, contains alkanes and unconverted olefins). The oligomers, with boiling points higher than the unconverted olefins and other substances present in the reactor feed stream, are thus enriched at the bottom of the distillation column; while the unconverted olefins with lower boiling points and, optionally, similar alkanes present in the feed stream, are discharged through the top of the distillation column and enriched in the distillate.

[0011] The advantage of the method of the present invention is that, by using a heat transfer medium according to claim 1 or a preferred embodiment, a significant amount of external input energy, primarily in the form of heating steam, can be saved. Thus, the method can operate in a more cost-effective manner and with reduced CO2 emissions.

[0012] The feed mixture of the method of the present invention contains at least C2 to C8 olefins, preferably C3 to C6 olefins, more preferably C3 to C5 olefins, and particularly preferably C4 olefins and similar alkanes. Suitable olefins include, in particular, α-olefins, n-olefins and cycloolefins, preferably n-olefins. In a preferred embodiment, the olefin is n-butene.

[0013] Olefins are typically not used as reactants in pure form, but rather as industrially available mixtures. Therefore, the term "starter mixture" as used herein should be understood to refer to various types of mixtures containing the respective olefin to be oligomerized in an amount that allows for economical and efficient oligomerization. The starter mixtures used according to the invention preferably contain virtually no other unsaturated or polyunsaturated compounds, such as dienes or acetylene derivatives. Preferably, starter mixtures containing less than 5% by weight, particularly less than 2% by weight, of branched olefins are used, based on the olefin content.

[0014] Propylene is a readily available basic chemical produced on a large industrial scale through naphtha cracking. C5 olefins are contained in light petroleum fractions from refineries or cracking units. Industrial mixtures containing straight-chain C4 olefins include light petroleum fractions from refineries, C4 fractions from FC cracking units or steam cracking units, mixtures from Fischer-Tropsch synthesis, mixtures from butane dehydrogenation, and mixtures formed by metathesis or other industrial processes. For example, a straight-chain butene mixture suitable for the method of the present invention can be obtained from the C4 fraction of a steam cracking unit. Here, butadiene is removed in the first step. This is achieved either by extraction (extractive distillation) of butadiene or by its selective hydrogenation. In both cases, a C4 fraction almost free of butadiene is obtained, known as raffinate I. In the second step, isobutene is removed from the C4 stream, for example by reacting with methanol to prepare MTBE. The C4 fraction at this point, free of both isobutene and butadiene, known as raffinate II, contains straight-chain butene and optionally butane. If at least a portion of the contained 1-butene is also separated from it, the so-called raffinate III is obtained.

[0015] In a preferred embodiment, the method of the present invention inputs a feed stream containing C4 olefins as a feed mixture. Suitable C4 olefin mixtures particularly include raffinate I, raffinate II, and raffinate III.

[0016] A particularly preferred method for obtaining butene using a C4 olefin mixture as a feed stream is as follows: a method for oligomerizing butene in at least two reaction stages R1 and RL and a separation stage A1 following RL, wherein each reaction stage comprises at least one reactor and at least one distillation column, and the separation stage comprises at least one distillation column DKA1, wherein... A feed mixture containing at least butene as a reactant olefin is oligomerized in at least one reactor in the first reaction stage R1 using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column in the first reaction stage R1 to obtain a residual stream RS1 containing at least unconverted butene and an oligomer product O1 containing at least the formed oligomers. RS1 is fed at least partially into the reactor for the subsequent reaction stage; The residual stream from the previous reaction stage is oligomerized in at least one reactor of the final reaction stage RL using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column of the final reaction stage RL to obtain a residual stream RSL containing at least unconverted butene and an oligomer product OL containing at least the oligomers formed. At least a portion of OL is fed into the distillation column DKA1 of the subsequent separation stage A1 and distilled there to obtain a dimer stream D1 consisting of at least 90% by weight of C8 oligomers and a bottom stream S1 containing at least the butene used and higher oligomers. A dimer stream D1 is obtained at the top of DKA1, which is then condensed and partially returned to DKA1 as reflux, while a portion is discharged from the process. The energy generated during the condensation of the dimer stream D1 and the heat generated in at least one reactor of the first reaction stage R1 are at least partially transferred to the heat transfer medium W1 to form a heated heat transfer medium W1.1; and Energy from a heated heat transfer medium W1.1 is transferred to another heat transfer medium W2 to form a heated heat transfer medium W2.1, which is first compressed and / or heated, and then used to generate a steam feed stream for at least heating distillation columns DKA1 and DKR1 through single-stage or multi-stage compression.

[0017] The method of the present invention includes at least two reaction stages R1 and RL. Reaction stage R1 is the first reaction stage, and RL refers to the final reaction stage. In a preferred embodiment of the invention, at least one other reaction stage is arranged between reaction stage R1 and reaction stage RL, which also includes at least one reactor and at least one distillation column. In another preferred embodiment of the invention, at least two other reaction stages exist between reaction stage R1 and reaction stage RL, each including at least one reactor and at least one distillation column. In a particularly preferred embodiment, the oligomerization method includes up to five reaction stages; that is, at least three other reaction stages exist between reaction stage R1 and reaction stage RL, each including at least one reactor and at least one distillation column. In all cases, one of the reaction stages may include multiple reactors, while only one reactor exists in the preceding or following reaction stage.

[0018] Therefore, the method of the present invention can be carried out in at least one other reaction stage R2, wherein reaction stage R2 includes at least one reactor and at least one distillation column DKR2. Preferably, the vapor stream used to heat distillation columns DKA1 and DKR1 is also used to heat distillation column DKR2. Thus, it is not necessary to use additional externally obtained energy.

[0019] In the above scenario, residual stream RS2 and oligomer product O2 are generated in DKR2. Residual stream RS2 contains at least unconverted reactant olefins, and oligomer product O2 contains at least the formed oligomers. RS2 can then be at least partially returned to subsequent reaction stages, optionally at least partially returned to the at least one reactor in the at least one reaction stage R2. Oligomer product O2 can be fed to distillation column DKRL in the final reaction stage RL and / or distillation column DKA1 in the subsequent separation stage A1; preferably, the oligomer product is fed to distillation column DKRL in the final reaction stage RL.

[0020] In addition to reaction stage R2, other reaction stages R3 may exist. In this case, the method of the present invention is carried out in at least one other reaction stage R3, wherein reaction stage R3 includes at least one reactor and at least one distillation column DKR3. Preferably, the steam feed streams used to heat distillation columns DKA1, DKR1, and DKR2 are also used to heat distillation column DKR3. Thus, it is not necessary to use additional externally obtained energy.

[0021] In the above scenario, residual stream RS3 and oligomer product O3 are generated in DKR3. Residual stream RS3 contains at least unconverted reactant olefins, and oligomer product O3 contains at least the formed oligomers. RS3 can then be at least partially returned to subsequent reaction stages, optionally back to the at least one reactor in the at least one reaction stage R3. Oligomer product O3 can be fed to distillation column DKRL in the final reaction stage RL and / or distillation column DKA1 in the subsequent separation stage A1.

[0022] Oligomerization of olefins is an exothermic reaction, meaning it releases heat. The heat released during butene oligomerization is primarily generated during the isomerization of 1-butene to cis- or trans-2-butene. The one or more reactors in each reaction stage of the method of the present invention can be operated isothermally or adiabatically, preferably isothermally. In a preferred embodiment, only the one or more reactors in the final reaction stage are adiabatically operated, while all other reactors in the preceding one or more reaction stages are isothermally operated, particularly actively cooled. Cooling media known to those skilled in the art, such as cooling water, can be used here. In this invention, isotherm means that despite cooling, the temperature rise within the reactor does not exceed 10 K. This corresponds to an isothermal operating mode for the reactor. Based on the assumption that the cooling capacity of the one or more reactors in the first reaction stage is 100%, the cooling capacity of the one or more reactors in subsequent reaction stages is less than 100%, but not 0% except in the final reaction stage.

[0023] According to the present invention, a mixture of feedstocks containing at least the olefins used is subjected to oligomerization in at least one reactor in the first reaction stage R1 using a heterogeneous catalyst.

[0024] The at least one reactor used in the first reaction stage R1 can be any reactor known to those skilled in the art suitable for oligomerization, such as a tubular reactor, fixed-bed reactor, tube bundle reactor, settling-rise tube reactor, or slurry reactor. Tubular reactors and / or tube bundle reactors are preferred. If the reaction stage comprises multiple reactors, these reactors can be identical or different from each other. The reactors in the reaction stage can also differ in their structure or configuration. For example, the volume of the first reactor in the reaction stage can be larger than that of subsequent reactors in the same reaction stage. Similarly, the reactors in each reaction stage can also be identical or different from each other. Here, the reactors in each reaction stage can differ in their structure or configuration. The volume of the reactor in the first reaction stage can, for example, be larger than that of one or all reactors in the subsequent reaction stages.

[0025] According to a preferred embodiment of the invention, reaction stage R1 includes at least one other reactor connected in parallel or in series with the first reactor, preferably in series. The effluent from the first reactor preferably enters the second reactor directly without prior separation of the oligomers. Therefore, preferably, complete conversion of the reactant olefins does not occur in the first reactor. The heat of reaction generated during oligomerization in the second reactor is also preferably transferred to the heat transfer medium W1.

[0026] The one or more reactors in reaction stage R1 each contain a heterogeneous catalyst for oligomerization. In principle, various catalysts suitable for oligomerization can be used. Suitable catalysts are known to those skilled in the art from the literature. The catalysts used are particularly in granular, extruded, or flake form.

[0027] The heterogeneous catalyst in the at least one reactor R1 preferably comprises a nickel compound, preferably nickel oxide, supported on an aluminosilicate carrier material. More preferably, the heterogeneous catalyst comprises less than 0.5% by weight, more preferably less than 0.1% by weight, and particularly preferably less than 0.01% by weight of titanium dioxide and / or zirconium dioxide, based on the total composition of the oligomeric catalyst. The carrier material can be an amorphous mesoporous aluminosilicate, a crystalline microporous aluminosilicate, or an aluminosilicate having both an amorphous and a crystalline phase. In this invention, "amorphous" refers to a property of a solid that, unlike crystalline solids, lacks a crystalline structure, i.e., lacks long-range order.

[0028] The heterogeneous catalyst preferably comprises 15 to 40 wt%, more preferably 15 to 30 wt%, NiO, 5 to 30 wt%, Al₂O₃, 55 to 80 wt%, SiO₂, and 0.01 to 2.5 wt%, preferably 0.05 to 2 wt%, of an alkali metal oxide, preferably sodium oxide. These values ​​are based on a total composition of 100 wt%. The oligomerizing catalyst is preferably substantially free of titanium dioxide and zirconium dioxide; in particular, the oligomerizing catalyst contains less than 0.5 wt%, preferably less than 0.1 wt%, more preferably less than 0.01 wt%, of titanium dioxide and zirconium dioxide in its total composition.

[0029] Oligopolymer catalysts can be prepared by known impregnation or coprecipitation methods, in which a solution of a transition metal compound (especially a nickel compound) is applied to a support material followed by calcination; in the coprecipitation method, the entire catalyst composition is precipitated from a single solution (usually an aqueous solution). Oligopolymer catalysts can also be prepared by other methods familiar to those skilled in the art. Hydrothermal treatment can also be performed in these preparations, wherein the still-wet catalyst is held at an elevated temperature and then dried.

[0030] The oligomerization can be carried out in one or all reactors of the final reaction stage RL at a temperature of 50°C to 200°C, preferably 60°C to 180°C, and more preferably 60°C to 130°C. The pressure of each existing reaction stage can be 10 to 70 bar, preferably 20 to 55 bar. In a preferred embodiment of the invention, the oligomerization is carried out in the liquid phase in each reaction stage. If the oligomerization is to be carried out in the liquid phase, the pressure and temperature parameters must be selected so that the feedstock mixture (the olefin or olefin mixture used) is present in the liquid phase.

[0031] A reaction mixture is generated during the oligomerization process in at least one reactor in reaction stage R1, and this reaction mixture is withdrawn from the at least one reactor. The reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKR1 in the first reaction stage R1 to obtain a residual feed stream RS1 containing at least unconverted olefins and an oligomer product O1 containing at least the generated oligomers. Thus, at least a portion of the generated oligomers is separated from the unconverted olefins by this distillation. The energy required to separate the reaction mixture is introduced here, in particular, via at least one reboiler.

[0032] According to the invention, a reboiler is an evaporator used to heat the bottom of a distillation column. Such reboilers are typically located outside the respective distillation column. Because energy (particularly heat) is transferred from one feed stream to another within the reboiler, they are heat transfer devices. The feed stream to be evaporated is drawn out through an outlet at the bottom of the distillation column and fed into the reboiler. The evaporated feed stream (optionally containing a liquid residue) is returned to the bottom region of the respective distillation column through at least one inlet.

[0033] Suitable evaporators that can be used as reboilers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin film evaporators. In natural circulation and forced circulation evaporators, the heat transfer device commonly used for the evaporator is a tube bundle or plate device. However, in addition to the above, any other evaporator construction type known to those skilled in the art for use in distillation columns may also be used.

[0034] According to a preferred embodiment of the invention, the reaction mixture is preheated before being introduced into the distillation column DKR1. This has the advantage of eliminating the need to introduce all the energy through the at least one reboiler. Furthermore, preheating also increases processing capacity due to the reduced hydraulic load within the distillation column.

[0035] Preheating of the reaction mixture is preferably carried out in a heat exchanger. Preheating can be performed using heat exchangers known to those skilled in the art. Suitable evaporators that can be used as heat exchangers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin-film evaporators. However, in addition to the above, any other evaporator configuration known to those skilled in the art suitable for the required preheating can also be used.

[0036] The at least one distillation column DKR1 used for distilling the reaction mixture can be any distillation column known to those skilled in the art. Preferably, the distillation column for the first reaction stage R1 includes internals. Suitable internals include, for example, trays, irregular packing (random packing), or structured packing. Commonly used trays include bubble cap trays, sieve trays, valve trays with fixed or movable valves, tunnel cap trays, or slotted trays. Irregular packing is typically a random packing bed. Commonly used random packing includes Raschig rings, Pall rings, Bell saddle packing, superring / superring reinforced packing, or Intalox® saddle packing. Structured packing is, for example, sold by Sulzer under the trade name Mellapak®. In addition to the internals described above, other suitable internals known to those skilled in the art can also be used.

[0037] Preferred internals have a low specific pressure drop per theoretical plate. For example, structured packing and loose packing have significantly lower pressure drops per theoretical plate compared to trays. The advantage of this is that the pressure drop in the distillation column during the first reaction stage R1 is kept as low as possible.

[0038] In a particularly preferred embodiment of the invention, the distillation column of the first reaction stage R1 includes a plurality of trays, preferably 5 to 100 trays, more preferably 10 to 50 trays.

[0039] Distillation conditions, such as temperature and pressure, are typically determined by the structure (column height, number of trays, tray or packing type, spacing, etc.). The separation performance of the distillation can also be controlled during operation by temperature distribution and / or heating within the column, as well as reflux in the distillate. Separation performance can also be adjusted within a certain range by changing the pressure. Therefore, the precise settings cannot override, nor be independent of, the structure of the distillation column. This is known to those skilled in the art. In a preferred embodiment, the pressure during distillation is 1 to 6 bar absolute, more preferably 2 to 5 bar absolute. Furthermore, the top temperature of the distillation column is preferably 15°C to 60°C, more preferably 25°C to 50°C.

[0040] Distillation of the reaction mixture yields a residual stream RS1 containing at least unconverted olefins and an oligomer product O1 containing at least the formed oligomers. The residual stream RS1 is typically obtained at the top of distillation column DKR1. The oligomer product O1 is obtained at the bottom of distillation column DKR1.

[0041] The residual feed stream RS1 is at least partially fed into the reactor of a subsequent reaction stage. This subsequent reaction stage can be reaction stage RL. In this case, there are only two reaction stages in total. However, the subsequent reaction stage can also be a reaction stage located between reaction stage R1 and reaction stage RL. In this case, there are at least three reaction stages. Furthermore, embodiments in which more than two reaction stages exist between reaction stage R1 and reaction stage RL are also feasible. According to a preferred embodiment of the invention, at least one additional reaction stage exists between reaction stage R1 and reaction stage RL, which comprises at least one reactor and at least one distillation column.

[0042] More preferably, the residual feed stream RS1 is at least partially returned to the at least one reactor in reaction stage R1. The return of the residual feed stream can dilute the feed mixture.

[0043] In a preferred embodiment of the invention, the residual feed stream RS1 is divided into at least two sub-streams RS1a and RS1b. Sub-stream RS1b can then be returned to the reactor of the first reaction stage R1. More preferably, sub-stream RS1a is compressed, thereby forming a compressed feed stream VR1 relative to the residual feed stream RS1, and the energy from the compressed feed stream VR1 is used to preheat the reaction mixture upstream of DKR1 and / or preheat the feedstock mixture upstream of the oligomer. Therefore, preheating can also be achieved by thermal integration measures (here, vapor compression), which eliminates the need for an external energy supply in the form of heating steam. Only electrical energy is required for compression.

[0044] The compression of the sub-feed stream RS1a can be performed in any manner known to those skilled in the art. For example, compression can be performed mechanically and in a single-stage or multi-stage manner. In this context, single-stage means compression from one pressure level to another. Multi-stage means compression first to pressure level X and then from X to pressure level Y. Multiple compressors of the same or different construction types can be used in multi-stage compression. Multi-stage compression can be accomplished using one or more compressors. Whether to use single-stage or multi-stage compression depends on the compression ratio, and therefore also on the pressure to which the sub-feed stream RS1a should be compressed.

[0045] The compressors particularly suitable for compressing the feed stream RS1a in the method of this invention are any type of compressor known to those skilled in the art, preferably mechanical compressors, which can also be used to compress airflows. Suitable compressors include, for example, single-stage or multi-stage geared turbine compressors, piston compressors, screw compressors, centrifugal compressors, or axial compressors.

[0046] As previously mentioned, in a preferred embodiment, the method includes at least one second reaction stage R2, in which a reaction mixture is generated in the at least one reactor and separated in a distillation column DKR2. Particularly preferably, the energy of the compressed feed stream VR1 is also used to preheat the reaction mixture upstream of DKR2.

[0047] After preheating, the sub-feed stream RS1a can be at least partially condensed and then at least partially fed as a feed mixture into the at least one reactor of the second reaction stage R2.

[0048] Oligomer O1 comprises the oligomers formed. In a preferred embodiment, oligomer O1 is at least partially, preferably completely, fed into the distillation column of the final reaction stage RL. All oligomers can be collected here and subsequently fed together into separation stage A1. Residues of unconverted olefins can also be separated here.

[0049] Regardless of the number of reaction stages, the residual stream from the previous reaction stage is sent to the final reaction stage RL. This can be part of the residual stream RS1 from the first reaction stage R1, or other residual streams, provided there is at least one other reaction stage between R1 and RL. Therefore, the residual stream from the previous reaction stage is sent to at least one reactor in the final reaction stage RL. If there are no other reaction stages between two reaction stages R1 and RL, the residual stream can be residual stream RS1. If there is at least one reaction stage between reaction stage R1 and reaction stage RL, the residual stream from one of these reaction stages, i.e., the penultimate reaction stage, is sent to the final reaction stage RL.

[0050] According to the invention, the supplied residual stream undergoes oligomerization in at least one reactor of the final reaction stage RL using a heterogeneous catalyst.

[0051] The at least one reactor used in the first reaction stage RL can be any reactor known to those skilled in the art suitable for oligomerization, such as a tubular reactor, fixed-bed reactor, tube bundle reactor, settling-rise tube reactor, or slurry reactor. Tubular reactors and / or tube bundle reactors are preferred. If the reaction stage comprises multiple reactors, these reactors can be identical or different from each other. The reactors in the reaction stage can differ in their structure or configuration. For example, the volume of the first reactor in the reaction stage can be larger than that of subsequent reactors in the same reaction stage. Similarly, the reactors in each reaction stage can also be identical or different from each other. Here, the reactors in each reaction stage can differ in their structure or configuration. For example, the volume of the reactor in the first reaction stage can be larger than that of one or all reactors in subsequent reaction stages.

[0052] According to a preferred embodiment of the invention, reaction stage R1 includes at least one other reactor connected in parallel or in series with the first reactor, preferably in series. The effluent from the first reactor preferably enters the second reactor without prior separation of oligomers. Therefore, preferably, the reactant olefins in the first reactor are not completely converted. The heat of reaction generated in this other reactor can also be integrated via a heat transfer medium, as described above for the first reactor.

[0053] The one or more reactors in the reaction stage RL each contain a heterogeneous catalyst for oligomerization. In principle, various catalysts suitable for oligomerization can be used. Those skilled in the art can learn about suitable catalysts from the literature. The catalysts used are particularly in granular, extruded, or flake form.

[0054] The heterogeneous catalyst in the at least one reactor of the reaction stage RL preferably comprises a nickel compound, preferably nickel oxide, supported on an aluminosilicate support material. However, more preferably, the heterogeneous catalyst comprises less than 0.5% by weight, more preferably less than 0.1% by weight, and particularly preferably less than 0.01% by weight of titanium dioxide and / or zirconium dioxide, based on the total composition of the oligomeric catalyst. The support material can be an amorphous mesoporous aluminosilicate, a crystalline microporous aluminosilicate, or an aluminosilicate having both an amorphous and a crystalline phase. In this invention, "amorphous" refers to a property of a solid that, unlike a crystalline solid, lacks a crystalline structure, i.e., lacks long-range order.

[0055] The heterogeneous catalyst in the at least one reactor of the reaction stage RL preferably comprises 15 to 40 wt%, preferably 15 to 30 wt% NiO, 5 to 30 wt% Al2O3, 55 to 80 wt% SiO2, and 0.01 to 2.5 wt%, preferably 0.05 to 2 wt% alkali metal oxide, preferably sodium oxide. These values ​​are based on a total composition of 100 wt%. The oligomerizing catalyst is preferably substantially free of titanium dioxide and zirconium dioxide; in particular, the oligomerizing catalyst contains less than 0.5 wt%, preferably less than 0.1 wt%, more preferably less than 0.01 wt% of titanium dioxide and zirconium dioxide in its total composition.

[0056] Oligopolymer catalysts can be prepared by known impregnation or coprecipitation methods, in which a solution of a transition metal compound (especially a nickel compound) is applied to a support material followed by calcination; in the coprecipitation method, the entire catalyst composition is precipitated from a single solution (usually an aqueous solution). Oligopolymer catalysts can also be prepared by other methods familiar to those skilled in the art. Hydrothermal treatment can also be performed in these preparations, wherein the still-wet catalyst is held at an elevated temperature and then dried.

[0057] The oligomerization is preferably carried out in one or more reactors of the final reaction stage RL at a temperature of 50°C to 200°C, more preferably 60°C to 180°C, and more preferably 60°C to 130°C. The pressure can be 10 to 70 bar, preferably 20 to 55 bar. In a preferred embodiment of the invention, the oligomerization is carried out in the liquid phase in each reaction stage. If the oligomerization is to be carried out in the liquid phase, then the pressure and temperature parameters must be selected for this purpose so that the feedstock mixture (the olefin or olefin mixture used) is present in the liquid phase.

[0058] A reaction mixture is generated in the oligomers in at least one reactor of the reaction stage RL, and this reaction mixture is withdrawn from the at least one reactor. The reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKRL of the final reaction stage RL to obtain a residual feed stream RSL containing at least unconverted olefins and an oligomer product OL containing at least the generated oligomers. Thus, at least a portion of the generated oligomers is separated from the unconverted olefins by distillation. In addition to the reaction mixture, oligomer products from previous reaction stages, such as oligomer product O1, can also be processed in the distillation column DKRL. The energy required to separate the reaction mixture is introduced, in particular, through at least one reboiler.

[0059] According to the invention, a reboiler is an evaporator used to heat the bottom of a distillation column. Such reboilers are typically located outside the respective distillation column. Because energy (particularly heat) is transferred from one feed stream to another within the reboiler, they are heat transfer devices. The feed stream to be evaporated is drawn out through an outlet at the bottom of the distillation column and fed into the reboiler. The evaporated feed stream (optionally containing a liquid residue) is returned to the bottom region of the respective distillation column through at least one inlet.

[0060] Suitable evaporators that can be used as reboilers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin film evaporators. In natural circulation and forced circulation evaporators, the heat transfer device commonly used for the evaporator is a tube bundle or plate device. However, in addition to the above, any other evaporator construction type known to those skilled in the art for use in distillation columns may also be used.

[0061] According to a preferred embodiment of the invention, the reaction mixture is preheated before being introduced into the distillation column DKRL. The advantage of this is that it eliminates the need to introduce all the energy through the at least one reboiler. Furthermore, preheating also increases processing capacity due to the reduced hydraulic load within the distillation column.

[0062] Preheating of the reaction mixture is preferably carried out in a heat exchanger. Preheating can be performed using heat exchangers known to those skilled in the art. Suitable evaporators that can be used as heat exchangers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin-film evaporators. However, in addition to the above, any other evaporator configuration known to those skilled in the art suitable for the required preheating can also be used.

[0063] The at least one distillation column DKRL used for distilling the reaction mixture from the reactor in the final reaction stage RL can be any distillation column known to those skilled in the art. Preferably, the distillation column DKRL for the final reaction stage RL includes internals. Suitable internals include, for example, trays, irregular packing (random packing), or structured packing. Commonly used trays include bubble cap trays, sieve trays, valve trays with fixed or movable valves, tunnel cap trays, or slotted trays. Irregular packing is typically a random packing bed. Commonly used random packing includes Raschig rings, Pall rings, Bell saddle packing, superring / superring reinforced packing, or Intalox® saddle packing. Structured packing is, for example, sold by Sulzer under the trade name Mellapak®. In addition to the internals described above, other suitable internals known to those skilled in the art can also be used.

[0064] Preferred internals have a low specific pressure drop per theoretical plate. For example, structured packing and loose packing have significantly lower pressure drops per theoretical plate compared to trays. The advantage of this is that the pressure drop in the distillation column of RL during the first reaction stage is kept as low as possible.

[0065] In a particularly preferred embodiment of the invention, the distillation column DKRL comprises a plurality of trays, preferably 5 to 100 trays, more preferably 10 to 50 trays.

[0066] Distillation conditions, such as temperature and pressure, are typically determined by the structure (column height, number of trays, tray or packing type, spacing, etc.). The separation performance of distillation can also be controlled during operation by temperature distribution and / or heating within the column, as well as reflux in the distillate. Separation performance can also be adjusted within a certain range by varying the pressure. Therefore, the precise settings cannot override, nor be independent of, the structure of the distillation column. This is known to those skilled in the art. The pressure during distillation is preferably 1 to 6 bar absolute, more preferably 2 to 5 bar absolute.

[0067] By distilling the reaction mixture and optionally the oligomers from the previous stage, a residual stream RSL containing at least unconverted olefins and an oligomer product OL containing at least the generated oligomers are obtained. The residual stream RSL is typically obtained at the top of the distillation column DKRL. The oligomer product OL is obtained at the bottom of the distillation column DKRL.

[0068] The residual feed stream RL can be at least partially returned to one or more reactors in the same reaction stage or one or more previous reaction stages. At least one sub-stream can also be removed as purge material to prevent enrichment of inert alkanes or impurities. If at least one sub-stream is removed as purge material and thus discharged from the method, it can be used as a synthetic feedstock for subsequent processes (e.g., hydroformylation, carbon source for the electric arc in acetylene preparation), as a combustion gas, or as a propellant gas after complete hydrogenation to alkanes, as a cooking gas, etc.

[0069] Oligomer product OL comprises the oligomers formed. The oligomers formed typically include at least dimers, trimers, and tetramers. However, trace amounts of higher oligomers may also be present in the oligomer product. Therefore, the resulting oligomer product is sent to the separation stage A1 for further processing to separate the dimers, trimers, and tetramers from each other.

[0070] The oligomer product OL is at least partially fed into distillation column DKA1 of separation stage A1 and distilled there, thereby obtaining a dimer stream D1 and a bottom stream S1. The dimer stream D1, based on its total weight, consists of at least 90% by weight, preferably at least 95% by weight, and more preferably at least 99% by weight, dimers of the olefin used. The bottom stream S1 contains at least trimers of the olefin used and higher oligomers. Preferably, the oligomer product OL is completely fed into distillation column DKA1 of separation stage A1.

[0071] The bottom stream S1, containing at least the trimer and higher oligomers of the reactant olefins used, can be decomposed into further oligomers in one or more subsequent distillation steps. These oligomers are then converted into high-value products such as aldehydes or alcohols. The oligomers in the dimer stream D1 can be sent to further processing, such as hydroformylation, alkoxycarbonylation, or hydrogenation. Butene dimers, i.e., C8 olefins, can be converted to a mixture of isononal via hydroformylation. This mixture of isononal is oxidized to the corresponding carboxylic acid, or hydrogenated to a mixture of C9 alcohols. C9 carboxylic acids can be used to produce lubricants or desiccants. The C9-alcohol mixture is a precursor for the production of plasticizers, particularly diisononyl phthalate (DINP), DINCH (1,2-diisononyl cyclohexanedicarboxylate), or DINCD (1,4-diisononyl cyclohexanedicarboxylate).

[0072] The energy required to separate the oligomer OL in distillation column DKA1 is introduced here, in particular, through at least one reboiler. According to the invention, a reboiler is an evaporator used to heat the bottom of the distillation column. Such reboilers are typically arranged outside the respective distillation column. Since energy (especially heat) is transferred from one feed stream to another in the reboiler, they are heat transfer devices. The feed stream to be evaporated is drawn out through an outlet at the bottom of the distillation column and fed into the reboiler. The evaporated feed stream (optionally containing a liquid residue) is returned to the bottom region of the respective distillation column through at least one inlet.

[0073] Suitable evaporators that can be used as reboilers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin film evaporators. In natural circulation and forced circulation evaporators, the heat transfer device commonly used for the evaporator is a tube bundle or plate device. However, in addition to the above, any other evaporator construction type known to those skilled in the art for use in distillation columns may also be used.

[0074] The at least one distillation column DKA1 used for distilling the oligomer OL can be any distillation column known to those skilled in the art. Preferably, the distillation column DKA1 for separation stage A1 includes internals. Suitable internals include, for example, trays, irregular packing (random packing) or structured packing. Commonly used trays include bubble cap trays, sieve trays, valve trays with fixed or movable valves, tunnel cap trays, or slotted trays. Irregular packing is typically a random packing bed. Commonly used random packing includes Raschig rings, Pall rings, Bell saddle packing, superring / superring reinforced packing, or Intalox® saddle packing. Structured packing is, for example, sold by Sulzer under the trade name Mellapak®. In addition to the above-mentioned internals, other suitable internals known to those skilled in the art can also be used.

[0075] Preferred internals have a low specific pressure drop per theoretical plate. For example, structured packing and loose packing have significantly lower pressure drops per theoretical plate compared to trays. The advantage of this is that the pressure drop in the distillation column of RL during the first reaction stage is kept as low as possible.

[0076] In a particularly preferred embodiment of the invention, the distillation column DKA1 includes a plurality of trays, preferably 5 to 100 trays, more preferably 10 to 50 trays.

[0077] Distillation conditions, such as temperature and pressure, are typically determined by the structure (column height, number of trays, tray or packing type, spacing, etc.). The separation performance of distillation can also be controlled during operation through temperature distribution and / or heating within the column, as well as reflux in the distillate. Separation performance can also be adjusted within a certain range by varying the pressure. Therefore, the precise settings cannot override, nor can they be independent of, the structure of the distillation column. This is known to those skilled in the art.

[0078] The dimer stream D1 obtained at the top of DKA1 is condensed and then partially returned to DKA1 as reflux, and partially discharged from the method. The energy generated during the condensation of the dimer stream D1 and the heat generated in the at least one reactor of the first reaction stage R1 are at least partially transferred to the heat transfer medium W1, thereby forming the heated heat transfer medium W1.1.

[0079] The condensation of the dimer stream D1 can be carried out in various condensers known to those skilled in the art, configured as heat exchangers to transfer the heat of condensation to the liquid or gaseous heat transfer medium W1. Possible heat exchangers that can be used include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin-film evaporators. In a preferred embodiment, the heat exchanger used is a kettle evaporator, in which the dimer stream D1 condenses within its tubes, and the heat transfer medium is heated in its shell side.

[0080] The heat transfer medium W1 used in the method of this invention can be any working medium familiar to those skilled in the art. The heat transfer medium W1 is preferably selected from: water; alcohol; alcohol-water mixtures; brine solutions; ammonia; mineral oil, such as diesel oil; heat transfer oil, such as silicone oil; bio-oil, such as limonene; and aromatic or aliphatic hydrocarbons, such as dibenzyltoluene. Water, methanol, ethanol, propanol, n-pentane, n-butane, n-hexane, n-propane, or ammonia are preferably used as the heat transfer medium W1. Water is particularly preferred as the heat transfer medium W1.

[0081] If the heat transfer medium W1 is used in liquid phase, i.e., a liquid heat transfer medium W1 is used and energy, preferably thermal energy, is supplied to it, then the heat transfer medium W1 will at least partially evaporate, thereby obtaining a heat transfer medium W1.1 that is at least partially gaseous. If the heat transfer medium W1 is used in gaseous phase, i.e., a gaseous heat transfer medium W1 is used and energy, preferably thermal energy, is supplied to it, then a gaseous heat transfer medium W1.1 is also obtained.

[0082] In a preferred embodiment of the invention, separation stage A1 includes at least one additional distillation column DKA2 for distilling the bottom stream S1, thereby separating the trimer from the higher oligomers. The trimer is obtained as a stream at the top of distillation column DKA2. Correspondingly, the higher oligomers are obtained at the bottom of DKA2.

[0083] The at least one distillation column DKA2 used for distilling the bottom stream S1 can be any distillation column known to those skilled in the art. Preferably, the distillation column DKA2 for separation stage A1 includes internals. Suitable internals include, for example, trays, irregular packing (random packing) or structured packing. Commonly used trays include bubble cap trays, sieve trays, valve trays with fixed or movable valves, tunnel cap trays, or slotted trays. Irregular packing is typically a random packing bed. Commonly used random packing includes Raschig rings, Pall rings, Bell saddle packing, superring / superring reinforced packing, or Intalox® saddle packing. Structured packing is, for example, sold by Sulzer under the trade name Mellapak®. In addition to the above-mentioned internals, other suitable internals known to those skilled in the art can also be used.

[0084] Preferred internals have a low specific pressure drop per theoretical plate. For example, structured packing and loose packing have significantly lower pressure drops per theoretical plate compared to trays. The advantage of this is that the pressure drop in the distillation column of RL during the first reaction stage is kept as low as possible.

[0085] In a particularly preferred embodiment of the invention, the distillation column DKA2 includes a plurality of internals, preferably 5 to 80 trays, more preferably 10 to 40 trays.

[0086] Distillation conditions, such as temperature and pressure, are typically determined by the structure (column height, number of trays, type of trays or packing, spacing, etc.). The separation performance of the distillation process can also be controlled during operation by temperature distribution and / or heating within the column, as well as reflux in the distillate. Separation performance can also be adjusted within a certain range by changing the pressure. Therefore, the precise settings cannot override, nor be independent of, the structure of the distillation column. This is known to those skilled in the art. The pressure during distillation is preferably vacuum, more preferably 100 to 800 mbar, more preferably 200 to 700 mbar, and most preferably 300 to 500 mbar.

[0087] The top stream obtained in DKA2 is preferably condensed, and then preferably partially returned to DKA2 as reflux, and partially discharged from the method. The energy generated during the condensation of the top stream in DKA2 is particularly preferably also at least partially transferred to the heat transfer medium W1.

[0088] Then, the energy from the heated heat transfer medium W1.1 is transferred to another heat transfer medium W2, thereby forming a heated heat transfer medium W2.1, which is first compressed and / or heated, and then used to generate a steam feed stream for at least heating distillation columns DKA1 and DKR1 through single-stage or multi-stage compression.

[0089] Therefore, energy, especially thermal energy, is first transferred from heat transfer medium W1.1 to heat transfer medium W2. The heat transfer medium W2 used in the method of this invention can be any working medium familiar to those skilled in the art. The heat transfer medium W2 is preferably selected from water; alcohols; alcohol-water mixtures; brine solutions; ammonia; mineral oils, such as diesel oil; heat transfer oils, such as silicone oil; bio-oils, such as limonene; and aromatic or aliphatic hydrocarbons, such as dibenzyltoluene. Water, methanol, ethanol, propanol, n-pentane, n-butane, n-hexane, n-propane, or ammonia are preferably used as the heat transfer medium W2. Water and / or methanol are particularly preferred as the heat transfer medium W2.

[0090] If the heat transfer medium W2 is used in liquid phase, i.e., a liquid heat transfer medium W2 is used and energy, preferably thermal energy, is supplied to it, then the heat transfer medium W2 will at least partially evaporate, thereby obtaining a heat transfer medium W2.1 that is at least partially gaseous. If the heat transfer medium W2 is used in gaseous phase, i.e., a gaseous heat transfer medium W2 is used and energy, preferably thermal energy, is supplied to it, then a gaseous heat transfer medium W2.1 is also obtained.

[0091] Energy can be transferred from W1.1 to W2 by methods known to those skilled in the art or by using heat exchangers known to those skilled in the art, such as the aforementioned evaporators. Suitable evaporators that can be used as heat exchangers include, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling film evaporators, or thin film evaporators. In addition to the evaporators described above, any other evaporator construction types known to those skilled in the art can also be used, as long as the required energy transfer is ensured.

[0092] In principle, heat transfer media W1 and W2 can be the same or different from each other. This means that, in principle, heat transfer media W1 and W2 can be the same liquid or the same gas. Similarly, the two heat transfer media W1 and W2 can also be different. The following describes these two process schemes.

[0093] According to the invention, the heated heat transfer medium W2.1 is first compressed and / or heated so that a vapor stream can subsequently be generated using single-stage or multi-stage compression. Heating can be achieved, for example, by the evaporator already described. Compression can be performed in any manner known to those skilled in the art, as described above.

[0094] In a particularly preferred embodiment of the invention, the heat transfer medium W2 used is methanol. By transferring energy from the heated heat transfer medium W1.1, the methanol is raised to a higher pressure and / or a higher temperature (also referred to as W2.1), followed by single-stage or multi-stage, preferably multi-stage, compression. Subsequent compression forms a compressed heat transfer medium W2.2, in this example, methanol.

[0095] For example, the compression of methanol as W2.1 can be mechanical and carried out in single or multi-stage manner. Here, single-stage refers to compression from one pressure level to another. Multi-stage refers to compression first to pressure level X, and then from X to pressure level Y. Multiple compressors of the same or different construction types can be used in multi-stage compression. Multi-stage compression can be achieved by one or more compressors. The choice between single-stage and multi-stage compression depends on the compression ratio, and therefore also on the pressure to which the heat transfer medium W2.1 should be compressed.

[0096] In this case, methanol as W2.1 is compressed in one or more stages to obtain W2.2 at a pressure of 3 to 30 bar, preferably 5 to 20 bar, and more preferably 7 to 15 bar.

[0097] The compressors used in the method of the present invention to compress methanol as a heat transfer medium W2.1 are any type of compressor known to those skilled in the art, preferably mechanical compressors, which can be used to compress gas streams. Suitable compressors include, for example, single-stage or multi-stage geared turbo compressors, piston compressors, screw compressors, centrifugal compressors, or axial compressors.

[0098] In a similarly preferred embodiment of the invention, the heat transfer medium W2 used is water under a slight vacuum of 300 to 800 mbar. Through energy transfer from the heated heat transfer medium W1.1, the water is at least partially evaporated (also referred to as W2.1). Preferably, the partially evaporated water as W2.1 is lifted, i.e. compressed, to a higher pressure by a single-stage or multi-stage, preferably multi-stage, blower and obtained as low-pressure steam. This compression forms a compressed heat transfer medium W2.2, in this example, low-pressure steam. The resulting low-pressure steam is preferably used to heat or preheat the feed stream entering the distillation column.

[0099] Regardless of the heat transfer medium used as heat transfer medium W2, in each case a heated heat transfer medium W2.1 is generated, which is compressed and produced as a compressed heat transfer medium W2.2. In another preferred embodiment of the invention, energy is then transferred from the compressed heat transfer medium W2.2 to another heat transfer medium W3, preferably water, thereby forming a heated heat transfer medium W3.1, which undergoes single-stage or multi-stage compression, preferably multi-stage compression, and is then used as a vapor stream to heat at least distillation columns DKA1 and DKR1, preferably all distillation columns present in the reaction stage and all distillation columns present in the separation stage. Furthermore, the vapor stream generated by the thermal integration described in this invention can also be used to heat distillation column DKA2, if such distillation column exists.

[0100] The heat transfer medium W3, preferably water, undergoes single-stage or multi-stage compression, preferably multi-stage compression. Through this single-stage or multi-stage compression, the pressure of the heat transfer medium W3 reaches 5 to 40 bar, preferably 10 to 30 bar, and more preferably 12 to 25 bar, and it exists as vapor within this pressure range. If multi-stage compression is performed, it is preferable to inject condensate between compression stages to prevent overheating during compression.

[0101] Heat transfer media W1, W2, and W3 are all used to transfer energy, particularly in the form of heat. Due to the respective energy transfer, the temperature and / or pressure decrease, resulting in at least partial condensation. Heat transfer media W1, W2, and W3 preferably form a dedicated loop, i.e., the heat transfer media return after energy transfer so that energy can be collected again.

[0102] During the return process of the heat transfer medium, these heat transfer media can be used to heat the heat transfer medium in the loop before compression. For example, the heat transfer medium W2.2 after energy transfer can also transfer energy to W2.1 before compression. For this purpose, known heat exchangers can be used.

[0103] The invention will be described with reference to the following accompanying drawings. The drawings are merely examples of suitable embodiments and do not limit the scope of the invention.

[0104] Figure 1 A non-inventive circuit diagram illustrating oligomerization and subsequent separation of oligomers is shown. The feed mixture is first fed into a first reaction stage (R1), where oligomerization occurs in reactor (1), followed by separation of the reaction mixture in distillation column DKR1 (2). The residual stream obtained from the top of distillation column DKR1 (2) is at least partially condensed in condenser (3) and then partially returned to reactor (1) and fed into the next reaction stage (RX). In this example, RX is RL in this invention. The oligomer O1 is fed into distillation column DKRX (6). The energy required for separation in distillation column DKR1 (2) is introduced via reboiler (4). The residual stream fed into the next reaction stage RX is converted in reactor (5). The resulting reaction mixture is separated in distillation column DKRX (6). In this example, DKRX corresponds to DKRL. The residual stream obtained from the top of distillation column DKRX (6) is at least partially condensed in condenser (7) and then at least partially returned to reactor (5). The energy required for separation in distillation column DKRX (6) is introduced via reboiler (8). The oligomer OL obtained at the bottom is sent to separation stage A1, where the oligomers are separated in distillation column DKA1 (9). The dimer stream D1 is obtained from the top and is condensed at least partially in heat exchanger (10). The energy required for separation in distillation column DKA1 (9) is introduced via reboiler (11).

[0105] Figure 2The non-inventive circuit diagram of oligomers is also shown. In addition... Figure 1 In addition to the process mode shown, there is an additional vapor compression, in which the residual stream obtained at the top of distillation column DKR1 (2) is compressed in compressor (13) and then used to heat the reaction mixture in preheater (14). During the return process from preheater (14), the stream upstream of compressor (13) is preheated in another preheater (12).

[0106] Figure 3 The non-inventive circuit diagram of oligomers is also shown. In addition... Figure 2 In addition to the process mode shown, the residual feed stream compressed in the compressor (13) is also used to heat the reaction mixture of the reaction stage RX in the preheater (15).

[0107] Figure 4 A circuit diagram of oligomers according to the present invention is shown. In addition... Figure 1 In addition to the process mode shown, there is a thermal integration according to the invention. The condensation heat at the distillation column DKA1 (9) is discharged through the heat exchanger (10), and the reaction heat of the reactor (1) is discharged through the heat exchanger (16) using heat transfer medium A. Using the thus heated heat transfer medium A, another heat transfer medium B is heated in the evaporator (17) and subjected to multi-stage compression in the compressor (19). Then, the compressed heat transfer medium B is used to heat another heat transfer medium C, such as water, in the evaporator (20). During the return of heat transfer medium B, a flash tank (23) can be provided in the middle, where the gas phase obtained is fed between the compression stages of the compressor (19). The liquid output of the flash tank (23) can be used in the heat exchanger (18) to preheat the heat transfer medium B before compression. The heat transfer medium C is also subjected to multi-stage compression in the compressor (21) and then used to heat the reboilers (4 and 11). During the return of the heat transfer medium C, a flash tank (22) can be installed downstream of the reboiler, where the gas phase obtained is fed between the compression stages of the compressor (21). The liquid output from the flash tank (22) is returned to the evaporator (20).

[0108] Figure 5 The circuit diagram of oligomers according to the present invention is also shown. (And...) Figure 4 The process shown differs, involving only two heat transfer media. Heat transfer medium B is heated in the evaporator (17) and then compressed in the compressor (19), which in this example is preferably a blower. The compressed heat transfer medium is fed into the flash tank (24). The vapor phase generated here is fed into another compressor (21) for multi-stage compression and then used to heat the reboilers (4 and 11). The liquid phase from the flash tank is at least partially returned to the evaporator (17) via a pump (25), or it may be fed between compression stages of the compressor (17) or downstream of the compressor (21).

[0109] Figure 6 The circuit diagram of oligomers according to the present invention is also shown. In addition... Figure 5 In addition to the process mode shown, there are two additional preheaters (26 and 27). These preheaters (26, 27) operate directly using the gas phase from the flash tank (24) as their energy source.

[0110] The following examples are intended to illustrate the invention, but do not limit the scope of application defined in the specification and claims. Example

[0111] All listed examples were simulated using Aspen Plus V.10. The kinetic models and material data were validated using running data. All examples were simulated using the same boundary conditions. A feed rate of 40 t / h was considered, with a butene content of 70 wt% (25 wt% 1-butene, 30 wt% trans-butene, and 15 wt% cis-butene). A butane / isobutane content of 30 wt% was considered, where isobutane in the feed was assumed to be 3%. In all cases, the feed temperature during the reaction stage was maintained at 95°C.

[0112] Example 1 (not the present invention) like Figure 1 The circuit diagram shown is used for simulation. Fresh feed is mixed with a 19 t / h circulating feed stream and heated to a feed temperature of 95°C via a heat transfer medium. The feed passes through reaction stage R1 (tubular reactor (1) with catalyst) at an absolute pressure of 25 bar. Reactor (1) is cooled to remove the heat of reaction. A total of 4.2 MW is required to discharge. After the first reaction stage, the reaction mixture is distilled. Distillation column (2) operates at a top pressure of 4.3 bar absolute pressure. The separation of high-boiling-point substances in the distillate of distillation column (2) is preferably less than 1% so as not to excessively inhibit the reaction. The resulting top temperature is 45°C. Consider 13 trays. To achieve this purity, a 16 t / h reflux and 5.1 MW of thermal power are required, which is introduced by 20 bar of steam (purchased externally). The resulting heat of condensation is 5.3 MW, which is discharged via an air cooler or a device (3) operating with circulating cooling water.

[0113] A portion of the liquid distillate is returned to the first reaction stage (19 t / h), while another 20 t / h (of which the mass content of n-butane / isobutane is 60%) is sent to the further final reaction stage RL. This stream is again mixed with the 15 t / h circulating stream and heated to a feed temperature of 95°C. The same reactor (5) as the reactor (1) of the first stage R1 is used. Similarly, the heat of reaction is discharged through a parallel-flow process water loop. 1 MW needs to be discharged. The reaction mixture is also distilled here. The distillation column (6) has 28 trays. The distillate from the second column is required to have a C8 content of less than 0.1% by weight. This requires a 2 t / h reflux and 2 MW of thermal power, which is introduced through external heating steam. 3 MW must be discharged through the condenser (10). The column (9) also operates at 4.3 absolute pressure. The resulting top temperature is 44°C. The distillate stream is separated again. A portion of 15 t / h is returned to the reaction stage, while another portion of 14.5 t / h (containing 82 wt% n-butane / isobutane) can be sent to other process units or storage tank areas. The conversion rate reaches 90%.

[0114] C8 / C12 / C16+ oligomers are obtained at the bottom of distillation column (6) and further separated in separation unit A1. In distillation column (9), the C8 isomers (preferably 1-octene and 2-methylheptene) are separated from the long-chain oligomers under vacuum and a top pressure of 350 mbar. To obtain a purity preferably greater than 99%, a reflux of 14 t / h must be established. The resulting top temperature is 86 °C. A total of 1.4 MW of thermal power (external steam) is required, and 3 MW of condensation heat must be discharged.

[0115] The system discharges a total of 11.3 MW of condensation heat and 5.2 MW of reaction heat (totaling 16.5 MW). A total of 8.5 MW of thermal power needs to be supplied to the system.

[0116] Example 2 (not the present invention): like Figure 2 The circuit diagram shown is for simulation purposes. The description of Example 1 also applies here. Furthermore, vapor compression occurs, where the heat of condensation is utilized at least partially by the compressor (13) and heat exchangers (12, 14). In this example, the feed preheater (14) introduces 1.75 MW into the system. 200 kW of electrical power is required to heat the vapor stream to the desired temperature level. Excessive energy input through the feed evaporator causes a shift in the temperature distribution. High-boiling-point substances boil upwards. More reflux is required. The total thermal power increases to 5.75 MW. However, the external heating requirement at the first distillation column decreases to 4 MW. Therefore, the total external thermal power decreases to 7.2 MW.

[0117] Example 3 (not the present invention): like Figure 3 The circuit diagram shown is for simulation purposes. The descriptions of Examples 1 and 2 also apply here. In addition to the feed preheater (14), the final stage feed preheater (15) also operates via vapor compression. Therefore, an additional 1.2 MW is introduced into the system. The total thermal power of the final stage increases to 2.4 MW, but the external thermal power decreases to 1.2 MW. For this, 350 kW of electrical power must be input through the compressor. The total external thermal power is 6.4 MW.

[0118] Example 4 (according to the present invention): like Figure 4 The circuit diagram shown is for simulation purposes. The descriptions of the reaction and separation stages in Example 1 also apply here. Here, the heat of condensation from vacuum distillation and the heat of reaction from the first stage are at least partially transferred to the hot water circuit via heat exchangers (10, 16). The heat in the hot water circuit is then used to evaporate the heat transfer medium (methanol in this example) in the evaporator (17) at 2.0 bar absolute pressure. The methanol is compressed (19) to 10 bar absolute pressure. This requires 1.2 MW of electrical power. Water evaporates in the evaporator (20) at 3 bar absolute pressure via methanol condensation. The steam is compressed (21) to 20 bar absolute pressure. Compression to 20 bar absolute pressure requires 1.6 MW of electrical power. Steam is required to heat the reboilers (4, 8, 11). A total of 8.5 MW of external heat power is replaced by 2.8 MW of electrical power. No external heating medium (steam) is required.

[0119] Example 5 (according to the present invention): like Figure 5 The circuit diagram shown is for simulation purposes. The descriptions of the reaction and separation stages in Example 1 and the further descriptions in Example 4 also apply here. The circuit diagram is the same as in Example 4. Water is used here as the heat transfer medium instead of methanol. The water is evaporated under a light vacuum (550 mbar) and compressed to an absolute pressure of 3 bar in a compressor (19). This process requires more electrical power. A total of 3.1 MW of electrical power is required to replace 8.5 MW of external heating power (steam).

[0120] Example 6 (according to the present invention): like Figure 5 The circuit diagram shown is for simulation purposes. The descriptions of the reaction and separation stages in Example 1 and the further descriptions in Example 5 also apply here. An optimization of Example 5 is shown. The concept of feed evaporators (26, 27) is used again here (see Examples 2 and 3). In this example, the feed preheaters (26, 27) operate using the generated 3 bar absolute pressure steam, so that less of the maximum pressure level needs to be reached. The electrical power is also reduced to 2.2 MW.

[0121] Table 1 summarizes the results of Examples 1 through 6: Table 1: Comparison of energy values ​​for all embodiments Example 1 2 3 4 5 6 External heating steam / MW 8.5 7.2 6.4 0 0 0 Electric power / MW 0 0.2 0.35 2.8 3.1 2.2 Unused energy discharged / MW 16.5 15 13.9 10.8 11.1 10.2 .

Claims

1. A method for oligomerizing C2 to C8 olefins in at least two reaction stages R1 and RL and a separation stage A1 following RL, wherein each reaction stage comprises at least one reactor and at least one distillation column, and the separation stage comprises at least one distillation column DKA1, wherein A feed mixture containing at least C2 to C8 olefins as reactant olefins is oligomerized in at least one reactor in the first reaction stage R1 using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKR1 in the first reaction stage R1 to obtain a residual stream RS1 containing at least unconverted reactant olefins and an oligomer product O1 containing at least the formed oligomers. RS1 is fed at least partially into the reactor for the subsequent reaction stage; The residual stream from the previous reaction stage is oligomerized in at least one reactor of the final reaction stage RL using a heterogeneous catalyst, and the reaction mixture obtained from the at least one reactor is distilled in at least one distillation column DKRL of the final reaction stage RL to obtain a residual stream RSL containing at least unconverted reactant olefins and an oligomer product OL containing at least the oligomers formed. At least a portion of OL is fed into the distillation column DKA1 of the subsequent separation stage A1 and distilled there to obtain a dimer stream D1 consisting of at least 90% by weight of dimers of the reactant olefins used and a bottom stream S1 containing at least trimers and higher oligomers of the reactant olefins used. A dimer stream D1 is obtained at the top of DKA1, which is then condensed and partially returned to DKA1 as reflux, while a portion is discharged from the process. The energy generated during the condensation of the dimer stream D1 and the heat generated in at least one reactor of the first reaction stage R1 are at least partially transferred to the liquid or gaseous heat transfer medium W1 to form a heated heat transfer medium W1.1; and Energy from a heated heat transfer medium W1.1 is transferred to another liquid or gaseous heat transfer medium W2 to form a heated heat transfer medium W2.1, which is first compressed and / or heated, and then used to generate a vapor stream for heating at least distillation columns DKA1 and DKR1 through single-stage or multi-stage compression.

2. The method of claim 1, wherein RS1 is at least partially returned to the at least one reactor of reaction stage R1.

3. The method according to claim 1 or 2, wherein at least one other reaction stage exists between reaction stage R1 and reaction stage RL, the other reaction stage comprising at least one reactor and at least one distillation column.

4. The method according to any one of the preceding claims, wherein the reaction stage R1 includes at least one other reactor R1.2 connected in parallel or in series with reactor R1.1, preferably connected in series.

5. The method according to claim 4, wherein the energy generated by reactor 2.1 is also at least partially transferred to the heat transfer medium W1.

6. The method according to any one of the preceding claims, wherein the method is carried out in at least one other reaction stage R2, wherein the reaction stage R2 includes at least one reactor R2.1 and at least one distillation column DKR2.

7. The method according to any one of the preceding claims, wherein the generated steam stream is also used to heat the distillation column DKR2.

8. The method according to any one of the preceding claims, wherein the heat transfer medium W1 is selected from: water; alcohol, aqueous alcohol solution; aqueous salt solution; mineral oil, such as diesel oil; heat transfer oil, such as silicone oil; bio-oil, such as limonene; and aromatic hydrocarbons, such as dibenzyltoluene.

9. The method according to any one of the preceding claims, wherein the heat transfer medium W2 is selected from: water; alcohol, aqueous alcohol solution; aqueous salt solution; mineral oil, such as diesel oil; heat transfer oil, such as silicone oil; bio-oil, such as limonene; and aromatic hydrocarbons, such as dibenzyltoluene.

10. The method according to any one of the preceding claims, wherein the heated heat transfer medium W2.1 is compressed and produced as the compressed heat transfer medium W2.

2.

11. The method of claim 10, wherein energy is transferred from the compressed heat transfer medium W2.2 to another heat transfer medium W3 to form a heated heat transfer medium W3.1, which undergoes single-stage or multi-stage, preferably multi-stage, compression, and is subsequently used as a vapor stream to heat all distillation columns present in the reaction stage and all distillation columns present in the separation stage.

12. The method according to claim 11, wherein the heat transfer medium W3.1 is compressed to a pressure of 5 to 40 bar, preferably 10 to 30 bar, and more preferably 12 to 25 bar, through single-stage or multi-stage compression.

13. The method according to any one of the preceding claims, wherein the reaction mixture is preheated before being introduced into the distillation column DKR1.

14. The oligomerization method according to any one of the preceding claims, wherein an oligomerization catalyst is used in the reactor of each reaction stage, the oligomerization catalyst comprising a nickel compound on an aluminosilicate support material, and preferably containing less than 0.5% by weight of titanium dioxide and zirconium dioxide in its total composition.

15. The oligomerization method according to any one of the preceding claims, wherein the method is an oligomerization method for C3 to C6 olefins, preferably an oligomerization method for C3 to C5 olefins, and particularly preferably an oligomerization method for C4 olefins.

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