Olefin two-stage reaction process with intermediate distillation

Abstract

The invention relates to a two-stage olefin reaction process with intermediate distillation. The invention relates to a method for reacting olefins having 4 to 20 carbon atoms, in which a feed stream containing at least linear olefins and branched olefins used is distilled between two reaction steps and only the obtained high-boiling phase is subjected to a second reaction, the method comprises the steps of heterogeneous catalytic hydroformylation, homogeneous catalytic hydroformylation or homogeneous catalytic alkoxy carbonylation.

Description

Field of the Invention

[0001] The subject of the present invention is a process for reacting olefins having 4 to 20 carbon atoms, in which at least a feed stream containing linear and branched olefins used is distilled between two reaction steps, and only the resulting high-boiling phase is subjected to a second reaction, namely heterogeneous catalytic hydroformylation, homogeneous catalytic hydroformylation or homogeneous catalytic alkoxycarbonylation. Background Art

[0002] In the context of the present invention, the term "reaction" is to be understood to mean three different reactions: heterogeneous catalytic hydroformylation, homogeneous catalytic hydroformylation and homogeneous catalytic alkoxycarbonylation, in which a feed stream containing olefins having 4 to 20 carbon atoms is reacted. These three reaction types are known organic chemical processes per se, but are described in more detail in the context of the present invention.

[0003] In the hydroformylation process, an olefin reacts with synthesis gas (i.e., a mixture of carbon monoxide (CO) and hydrogen (H2)) in a suitable homogeneous catalyst system to form the corresponding aldehyde. Hydroformylation is an industrial process operated in factories, in which aldehydes can be produced annually on a scale of several thousand to several hundred thousand tons (kt). The catalyst systems commonly used here are homogeneous dissolved catalyst systems and contain transition metal complexes mainly with cobalt or rhodium as the metal and phosphorus-containing ligands. Many examples of them can be found in the patent literature.

[0004] In recent years, there has been a renewed and greater interest in heterogeneous catalytic hydroformylation. EP 3632885 A1 discloses a corresponding example of hydroformylation. In this document, instead of the known homogeneous dissolved catalyst, a catalyst system present in heterogeneous form on a monolithic support composed of a porous ceramic material is used. The heterogeneous catalyst system is in particular a transition metal complex mainly with cobalt or rhodium as the metal and phosphorus-containing ligands known or equivalent in homogeneous catalytic hydroformylation.

[0005] Alkoxycarbonylation is the reaction of an olefin with carbon monoxide and an alcohol to form the resulting ester. This generally involves the use of a metal-ligand complex as a catalyst, which is present in homogeneous solution in the reaction mixture and thus also in the product mixture. For example, EP 3750620 A1 discloses a corresponding process. The catalyst system used particularly contains metals of groups 8 to 10 of the Periodic Table of the Elements (PSE) (e.g., palladium) or their compounds, phosphorus-containing ligands and an acid as a cocatalyst.

[0006] The above reaction methods, i.e., homogeneous catalytic hydroformylation, heterogeneous catalytic hydroformylation or homogeneous catalytic alkoxycarbonylation, can be operated in an economically viable manner depending on various factors. One of these factors is the reaction rate, which should be as high as possible. Ultimately, more product can be produced per unit time compared to a reaction with a lower reaction rate. However, it should be noted here that when the reaction rate increases, other reaction parameters, such as the reaction conversion and / or the selectivity of the desired product, are not impaired, so the advantage of the higher reaction rate is not reversed.

[0007] Problems particularly arise in two-stage reaction methods, where the reaction takes place in a first stage and the residual material stream from the first stage is used in a second stage. Since part of the olefin has reacted in the first stage, the reaction rate may decrease and / or the conversion may decrease in the second stage. Summary of the Invention

[0008] Therefore, the object of the present invention is to provide a reaction method for olefins by means of which a higher reaction rate can be achieved in the second reaction stage, while the reaction conversion and / or the selectivity of the desired product (here aldehyde in the case of hydroformylation or ester in the case of alkoxycarbonylation) are not significantly impaired or even improved.

[0009] This object is achieved by the method according to the claims. Preferred embodiments are given in the dependent claims. The method according to the invention is a method for reacting olefins having 4 to 20 carbon atoms and comprises the following steps:

[0010] a) providing a feed stream comprising at least linear olefins and branched olefins each having the same number of carbon atoms;

[0011] b) feeding the feed stream from step a) to a reaction unit comprising one or more reactors and carrying out the reaction in this reaction unit to obtain a product mixture, where the reaction is heterogeneous catalytic hydroformylation in the presence of syngas, homogeneous catalytic hydroformylation in the presence of syngas or homogeneous catalytic alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol,

[0012] c) separating a residual material stream from the product mixture of step b), where the residual material stream comprises at least unreacted olefins;

[0013] d) distilling the residual material stream from step c) in at least one distillation column to obtain at least one low-boiling phase and one high-boiling phase, where 1 wt% to less than 50 wt% of the distilled feed stream is obtained as the low-boiling phase, and where the proportion of linear olefins in the low-boiling phase is less than the proportion of linear olefins in the high-boiling phase; and

[0014] e) Feeding the high-boiling phase from step d) to a reaction unit comprising one or more reactors and carrying out a reaction in the reaction unit, wherein the reaction is a multiphase catalytic hydroformylation in the presence of syngas, a homogeneous catalytic hydroformylation in the presence of syngas or a homogeneous catalytic alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol.

[0015] The key method steps are step d), the distillation of the feed stream and carrying out the reaction in step e) using only the high-boiling phase. The advantage of the method according to the invention is that the reaction rate of the reaction in step e) is higher than in known methods without such distillation. The reason may be that relatively inactive isomers and / or reaction-inhibiting substances tend to be separated from the feed stream together with the low-boiling phase during distillation and are therefore not fed to the reaction.

[0016] The first step a) of the method according to the invention is to provide a feed stream comprising an olefin having 4 to 20 carbon atoms, preferably an olefin having 7 to 16 carbon atoms, particularly preferably an olefin having 7 to 12 carbon atoms. A feed stream comprising an olefin having 8 and / or 12 carbon atoms is very particularly preferred. The feed streams used are generally industrially available hydrocarbon streams containing at least different isomers of the respective olefins. These feed streams contain at least straight-chain and branched olefins having the same number of carbon atoms each. It is understood that the amount of each olefin in the hydrocarbon stream should be high enough to enable the reaction in step b) to be operated in an economically viable manner; preferably, based on the total weight of the feed stream, the feed stream should contain at least 5% by weight of the relevant olefin.

[0017] A feed stream containing an olefin having 4 carbon atoms, for example a mixture of different isomers of butene (1-butene, 2-butene, isobutene), is usually a light petroleum fraction from a refinery, a C4 fraction from an FC cracker or a steam cracker, a mixture from Fischer-Tropsch synthesis, a mixture from butane dehydrogenation and a mixture formed by metathesis or from other industrial processes, where the concentration of the isomers is partly different. For example, a straight-chain butene mixture suitable for the method according to the invention can be obtained from the C4 fraction of a steam cracker. Olefins having 5 carbon atoms, i.e. pentenes, are present in light petroleum fractions produced by refineries or crackers.

[0018] Higher olefins can in particular be obtained by oligomerization reactions (such as dimerization, trimerization or tetramerization). Suitable hydrocarbon feedstreams are also mixtures of isomeric hexenes (Dipropen) obtained by dimerization of propene, mixtures of isomeric octenes (Dibuten) obtained by dimerization of butene, mixtures of isomeric nonenes (Tripropen) obtained by trimerization of propene, mixtures of isomeric dodecenes (Tetrapropen) or Tributen obtained by tetramerization of propene or trimerization of butene, isomeric hexadecenes (Tetrabuten) obtained by tetramerization of butene, and olefin mixtures prepared by co-oligomerization of olefins having different numbers of carbon atoms (preferably 2 to 4 carbon atoms), optionally after distillative separation into fractions having the same or different numbers of carbon atoms. Olefins or olefin mixtures produced by Fischer-Tropsch synthesis can also be used. Additionally, olefins produced by olefin metathesis or other industrial processes can also be used.

[0019] The feedstream provided in step a) may have been pre-treated by one or more additional processing steps to convert certain components in the feedstream or to remove them from the stream. An example is the removal of impurities that may be harmful to the catalyst, such as oxygen-, nitrogen- or sulfur-containing substances or compounds. One possible method for removing such impurities is to pass the feedstream over an adsorption bed, where the impurities remain attached to the adsorber. These methods are known and have been published several times.

[0020] Feed the feedstream provided in step a) to the reaction in the reaction unit in step b). The reaction unit for the reaction in step b) can consist of one or more reactors. The (one or more) reactors can in particular be selected from stirred tank reactors, loop reactors, jet loop reactors, bubble column reactors or combinations thereof. If there are multiple reactors, these reactors can be the same or different. If there are multiple reactors, they can be connected in parallel or in series, or arranged in a mixed manner of parallel and series connections.

[0021] The reaction in step b) is in particular not carried out to complete conversion. In a preferred embodiment of the present invention, the reaction in step b) is carried out to such an extent that the conversion of the reaction in step b) is at most 95%, preferably at most 92%, more preferably at most 90%, more preferably at most 88%, particularly preferably at most 85%. The lower the conversion, the greater the amount of unreacted olefins available for reaction in the second stage. On the other hand, the conversion must be high enough so that the first stage can be operated in an economically viable manner.

[0022] If the reaction in step b) is a homogeneous catalytic reaction, the following process conditions are preferred:

[0023] In this method, the olefin used undergoes hydroformylation with syngas in the presence of a homogeneously dissolved catalyst system. The molar ratio between the syngas and the feed mixture should be from 6:1 to 1:1, preferably from 3:1 to 1:1, and particularly preferably from 2:1 to 1:1. The hydroformylation can optionally be carried out in the presence of a solvent known to those skilled in the art.

[0024] The homogeneous catalyst system that can be used for hydroformylation can contain Co or Rh, preferably Rh, and preferably a phosphorus-containing ligand. In the case of Co, a phosphorus-containing ligand is not actually absolutely necessary. Suitable catalyst systems are well-known to those skilled in the art. In a particularly preferred embodiment, the homogeneous catalyst system contains Rh and a phosphorus-containing ligand or consists of Rh and a phosphorus-containing ligand. Ligands suitable for the catalyst system according to the present invention are known to those skilled in the art (see, for example, the textbook "Rhodium Catalyzed Hydroformylation" (since 2002), by P.W.N.M. van Leeuwen) or "Hydroformylation – Fundamentals, Processes and Applications in Organic Synthesis" (since 2016), by A. and R. Franke).

[0025] The phosphorus-containing ligand for the catalyst system according to the present invention is preferably a phosphine (such as TPP (triphenylphosphine)), a mono-phosphite (such as Alkanox 240 (tris(2,4-di-tert-butylphenyl) phosphite)) or a bis-phosphite (such as Biphephos). Mixtures of ligands can also be used.

[0026] The temperature in the homogeneous catalytic hydroformylation is preferably in the range of 80 °C to 250 °C, more preferably in the range of 90 °C to 225 °C, and particularly preferably in the range of 100 °C to 210 °C. The pressure in the homogeneous catalytic hydroformylation is preferably in the range of 20 to 350 bar, more preferably in the range of 30 to 325 bar, and particularly preferably in the range of 45 to 300 bar.

[0027] The pressure in the hydroformylation generally corresponds to the total gas pressure. In the context of the present invention, the total gas pressure refers to the sum of the pressures exerted by all gaseous substances present, i.e., the pressure of the (total) gas phase. In this method, this particularly corresponds to the sum of the partial pressures of CO and H2, i.e., the total gas pressure is the syngas pressure.

[0028] Homogeneous catalytic hydroformylation can be operated as a liquid discharge process ("liquid recycle") or a gas discharge process ("gas recycle"). These two process variants are known to the person skilled in the art and are described in many textbooks. In the context of the present invention, it is not necessary to specifically select one such method, since the method can in principle be carried out in both ways. In any case, it remains important in homogeneous catalysis to remove the catalyst system from the reaction effluent. In the case of liquid discharge, this can be achieved, for example, by a flash process or membrane separation. In the case of gaseous discharge, this can be achieved, for example, by condensation and / or washing. This is also known to the person skilled in the art and does not require detailed explanation. The further treatment of the reaction effluent, in particular the separation of the reaction products, is likewise well known to the person skilled in the art and can be carried out, for example, by thermal separation methods such as distillation. In the context of the present invention, thermal separation or thermal separation methods mean separation methods in which separation is based on the boiling point.

[0029] If the reaction is a heterogeneous catalytic hydroformylation, the following process conditions are preferred:

[0030] In the context of the present invention, heterogeneous catalytic hydroformylation is in particular those in which the catalyst system is heterogenized, in particular by being immobilized on a support material (see the introductory discussion in WO 2015 / 028284A1). Thus, the terms heterogenization and immobilization should be understood to mean that the catalyst system is fixedly present by forming a thin liquid film on the surface and / or pores of the solid support material.

[0031] The heterogeneous catalytic hydroformylation reaction is characterized in particular by the fact that the high-boiling phase from step d) passes in gaseous form through a support consisting of a porous ceramic material, on which the catalyst system is present in heterogeneous form and which catalyst system comprises a metal of group 8 or 9 of the Periodic Table, at least one organophosphorus ligand, and a stabilizer.

[0032] The temperature in heterogeneous catalytic hydroformylation can be in the range from 65 °C to 200 °C, preferably from 75 °C to 175 °C, and particularly preferably from 85 °C to 150 °C. The pressure in heterogeneous catalytic hydroformylation should be greater than 0 bar, but in particular not greater than 35 bar, preferably not greater than 30 bar, and particularly preferably not greater than 25 bar. The molar ratio between the synthesis gas and the feed mixture should be from 6:1 to 1:1, preferably from 5:1 to 3:1. Optionally, the feed mixture can be diluted with an inert gas or a solvent (for example, with the alkanes present in an industrial hydrocarbon stream) to control the reaction.

[0033] The catalyst system used in the hydroformylation process according to the invention preferably comprises a transition metal of Group 8 or Group 9 of the Periodic Table of the Elements, in particular iron, ruthenium, iridium, cobalt or rhodium, particularly preferably cobalt and rhodium, at least one organophosphorus ligand, a stabilizer and optionally an ionic liquid.

[0034] The stabilizer is preferably an organic amine compound, particularly preferably an organic amine compound containing at least one 2,2,6,6-tetramethylpiperidine unit.

[0035] The organophosphorus ligand for the catalyst system according to the invention preferably has the general formula (I)

[0036] R'-A-R”-A-R”'(I)

[0037] wherein R', R” and R”' are each an organic residue, and the two A's are each a bridging group -O-P(-O)2-, where two of the three oxygen atoms -O- are each bonded to the residue R' and the residue R”', provided that R' and R”' are two organic residues separated from each other. R' and R”' may be the same or different organic residues. The organic residues R', R” and R”' preferably do not contain terminal trialkoxysilyl groups.

[0038] In a preferred embodiment, R', R” and R”' in the compound of formula (I) are preferably selected from substituted or unsubstituted 1,1'-biphenyl, 1,1'-binaphthyl and o-phenyl, particularly preferably substituted or unsubstituted 1,1'-biphenyl, provided that R' and R”' are not the same. Particularly preferably, the substituted 1,1'-biphenyl has alkyl and / or alkoxy groups at the 3,3' and / or 5,5' positions of the 1,1'-biphenyl basic structure, in particular C1-C4 alkyl groups, particularly preferably tert-butyl and / or methyl groups, and / or preferably C1-C5 alkoxy groups, particularly preferably methoxy groups. An example of a suitable ligand is Biphephos (6,6'-[(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)bis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepine)).

[0039] The porous ceramic material constituting the support is preferably selected from silicate ceramics, oxide ceramics, nitride ceramics, carbide ceramics, silicide ceramics, and mixtures thereof. The silicate ceramics are preferably selected from aluminosilicates, magnesium silicates, and mixtures thereof, such as bentonite. The oxide ceramics are preferably selected from γ-aluminum oxide, α-aluminum oxide, titanium dioxide, beryllium oxide, zirconium oxide, aluminum titanate, barium titanate, zinc oxide, iron oxide (ferrite), and mixtures thereof. The nitride ceramics are preferably selected from silicon nitride, boron nitride, aluminum nitride, and mixtures thereof. The carbide ceramics are preferably selected from silicon carbide, boron carbide, tungsten carbide, or mixtures thereof. Mixtures of carbide and nitride ceramics, so-called carbonitrides, can also be considered. The silicide ceramic is preferably molybdenum disilicide. According to the present invention, the support on which the catalyst system is applied preferably consists of carbide ceramics.

[0040] The support can be a monolith, i.e., the support can consist of a ceramic material block (three-dimensional object). Such a block can be formed in one piece or consist of a plurality (i.e., at least two) separate parts that can be joined together to form the block and / or can be joined to each other in a fixed or detachable manner. The support can also be in the form of granules or pellets. The median particle size (d50) of the support can be from 0.1 mm to 7 mm, preferably from 0.3 to 6 mm, and particularly preferably from 0.5 mm to 5 mm. The median particle size can be determined by imaging methods, in particular by the methods mentioned in standard ISO 13322-1 (version: 2004-12-01) and ISO 13322-2 (version: 2006-11-01). The support can be produced in the form of granules or pellets by methods known to those skilled in the art. This can be done, for example, by mechanically crushing a monolith of carbide material, nitride material, silicide material, or mixtures thereof (e.g., using a jaw crusher) and adjusting the particle size of the resulting crushed particles by sieving.

[0041] According to the present invention, the support is composed of a porous ceramic material, i.e., a ceramic material having pores. Different porosities or pore diameters can in principle be considered. However, the pore diameter is preferably in the range of 0.9 nm to 30 μm, more preferably in the range of 10 nm to 25 μm, and particularly preferably in the range of 70 nm to 20 μm. The pore diameter can be determined by nitrogen adsorption or mercury porosimetry according to DIN 66133 (version: 1993-06).

[0042] It is possible to additionally apply a so-called washcoat on a support made of a ceramic material, which washcoat consists of a ceramic material that is the same as or different from the ceramic material of the support, in particular a ceramic material selected from the above-mentioned ceramic materials, preferably silica. The washcoat itself can be porous or non-porous; the washcoat is preferably non-porous. The particle size of the washcoat is preferably from 5 nm to 3 μm, more preferably from 7 nm to 700 nm. The washcoat is used to introduce or create the desired pore size and / or increase the surface area of the support. In particular, the washcoat can be applied by dipping (dip coating) the support into a washcoat solution containing the ceramic material of the washcoat (optionally also as a precursor). The amount of the washcoat present on the support is ≤20% by weight, preferably ≤15% by weight, particularly preferably ≤10% by weight based on the total amount of the support. Then the catalyst system is applied to the ceramic support provided with the washcoat thus produced. However, preferably, the support does not include a washcoat.

[0043] The reaction effluent obtained in the heterogeneous catalytic hydroformylation does not necessarily have to be free of the catalyst system in principle. Further processing, i.e., for example, the separation of the reaction products, is well known to those skilled in the art and can in principle be carried out by distillation or by another thermal separation method.

[0044] If the reaction is a homogeneous catalytic alkoxycarbonylation, the following process conditions are preferred:

[0045] In alkoxycarbonylation, an olefin reacts with carbon monoxide (CO) and an alcohol (in the present case, a C1 to C6 alcohol) in the presence of a homogeneous catalytic catalyst system to form an ester.

[0046] Carbon monoxide can be provided directly as a feed mixture or by adding a carbon monoxide-containing gas selected from synthesis gas, water gas, producer gas, and other carbon monoxide-containing gases. Carbon monoxide can also be provided by first separating the carbon monoxide-containing gas into its components in a manner known to those skilled in the art and then introducing the carbon monoxide into the reaction zone. A certain proportion of hydrogen or other gases may still be present in the carbon monoxide because complete separation is almost impossible to achieve.

[0047] The alcohol used in alkoxycarbonylation is a monohydric alcohol or a polyhydric alcohol (polyhydric alcohol = two or more OH groups) having 1 to 6 carbon atoms. The alcohols suitable for the reaction in step e) are methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol, or a mixture thereof. Methanol and ethanol are preferably used in alkoxycarbonylation. If methanol is used, the reaction is also called methoxycarbonylation. When ethanol is used, the reaction is also called ethoxycarbonylation.

[0048] The homogeneous catalyst system for alkoxycarbonylation preferably comprises at least one metal or its compound of Groups 8 to 10 of the Periodic Table of the Elements (PSE), a phosphorus-containing ligand, and an acid as a cocatalyst.

[0049] The metals of Groups 8 to 10 of the PSE are preferably palladium. The palladium is preferably used as a palladium compound in the form of a precursor compound, which coordinates with the phosphorus-containing ligand. Examples of palladium compounds that can be used as precursor compounds are palladium chloride [PdCl2], palladium(II) acetylacetonate [Pd(acac)2], palladium(II) acetate [Pd(OAc)2], dichloro(1,5-cyclooctadiene)palladium(II) [Pd(cod)2Cl2], bis(dibenzylideneacetone)palladium(0) [Pd(dba)2], tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3], bis(acetonitrile)dichloropalladium(II) [Pd(CH3CN)2Cl2], (cinnamyl)dichloropalladium [Pd(cinnamyl)Cl2]. Compounds [Pd(acac)2] or [Pd(OAc)2] are preferably used. The metal concentration of palladium in alkoxycarbonylation is preferably 0.01 to 0.6 mol%, preferably 0.03 to 0.3 mol%, particularly preferably 0.04 to 0.2 mol% based on the amount of substance of the hydrocarbon used.

[0050] The suitable phosphorus-containing ligands for the catalyst system according to the invention preferably have a bidentate structure. Preferred phosphorus-containing ligands for the catalyst system according to the invention are benzene-based diphosphine compounds, such as those disclosed in EP 3121184 A2. The ligand can be combined with palladium in a pre-reaction so that the palladium-ligand complex is introduced into the reaction zone, or added in-situ to the reaction and combined with palladium there. In alkoxycarbonylation, the ligand:metal molar ratio can be 1:1 to 10:1, preferably 2:1 to 6:1, particularly preferably 3:1 to 5:1.

[0051] In alkoxycarbonylation, the homogeneous catalyst system further comprises an acid, which can in particular be a Brønsted acid or a Lewis acid. The Lewis acid used can in particular be aluminum trifluoromethanesulfonate, aluminum chloride, aluminum hydride, trimethylaluminum, tris(pentafluorophenyl)borane, boron trifluoride, boron trichloride, or a mixture thereof. Among the above Lewis acids, aluminum trifluoromethanesulfonate is preferably used. The Lewis acid is preferably added in a Lewis acid:ligand molar ratio of 1:1 to 20:1, preferably 2:1 to 15:1, particularly preferably 5:1 to 10:1.

[0052] Suitable Brønsted acids preferably have an acid strength with pKs ≤ 5, particularly preferably an acid strength with pKs ≤ 3. The acid strength pKs relates to the pKs value determined under standard conditions (25 °C, 1.01325 bar). For polybasic acids, in the context of the present invention, the acid strength pKs relates to the pKs of the first proton dissociation step. The Brønsted acid is preferably added in a molar ratio of Brønsted acid: ligand of 1:1 to 15:1, preferably 2:1 to 10:1, particularly preferably 3:1 to 5:1.

[0053] The Brønsted acid used can in particular be perchloric acid, sulfuric acid, phosphoric acid, methylphosphonic acid or sulfonic acid. Suitable sulfonic acids are, for example, methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid (PTSA), 2-hydroxypropane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid and dodecylsulfonic acid. Particularly preferred acids are sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid. The acid is preferably sulfuric acid. In contrast, carboxylic acids are less suitable or not at all suitable.

[0054] Homogeneous catalytic alkoxycarbonylation is preferably carried out at a temperature of 25 °C to 140 °C, more preferably at a temperature of 60 °C to 120 °C, and particularly preferably at a temperature of 70 °C to 110 °C. The pressure can be 5 to 60 bar, preferably 10 to 40 bar, particularly preferably 15 to 30 bar.

[0055] A product mixture is obtained by homogeneous catalytic alkoxycarbonylation, which at least contains the ester formed by the reaction, the homogeneous catalyst system, low boilers (such as low-boiling by-products such as ethers), high boilers, unreacted alcohol and possibly unreacted hydrocarbons. Therefore, the product mixture can be subjected to subsequent catalyst removal. For example, this can be achieved by membrane separation, whereby the homogeneous catalyst system and unreacted hydrocarbons and / or unreacted alcohol are enriched in the retentate, while the ester formed is enriched in the permeate. Then the retentate containing the enriched homogeneous catalyst system can be recycled to the reaction zone.

[0056] Further treatment of the permeate, in particular the separation of the ester as the target product, can be carried out by known methods and is in principle familiar to those skilled in the art. One possible method is a thermal separation method such as distillation.

[0057] In the reaction of step b), a product mixture is formed, which is taken out of the reaction device and sent to the separation in step c). The product mixture will at least contain the reaction product formed and unreacted olefins. In the separation in step c), a residual material stream containing at least unreacted olefins is separated from the product mixture. By the separation in step c), at least a part of the reaction product formed is thus separated from the unreacted olefins. The separation in step c) is preferably carried out by thermal separation.

[0058] The thermal separation in the separation process in step c) can be distillation, thin-film evaporation, falling-film evaporation or a combination of two or more of them. However, those skilled in the art can select a suitable method based on their knowledge in the art according to the requirements of their respective processes. In one embodiment of the present invention, the thermal separation is thin-film evaporation, falling-film evaporation or a combination of thin-film evaporation and falling-film evaporation. Thin-film evaporation and falling-film evaporation can also have a multi-stage configuration, i.e., in a so-called cascaded form. In a particularly preferred embodiment, the thermal separation is multi-stage falling-film evaporation (evaporator cascade). If thin-film evaporation, falling-film evaporation or a combination thereof is used for thermal separation, it must be expanded at low pressure after the first membrane separation step, i.e., the pressure is ≥10 mbar but less than 1 bar. This expansion is preferably carried out in one step.

[0059] Removing the product mixture in step c) gives a residual material stream containing at least unreacted olefins. A product stream containing at least the formed reaction product is additionally obtained. This product stream is no longer relevant to the present invention. The product stream can be sent for further processing and / or further reaction, for example, sent for hydrogenation, in which the aldehyde formed by hydroformylation is converted into the corresponding alcohol.

[0060] The residual material stream separated in step c) is distilled in a subsequent step d), in which a high-boiling phase and a low-boiling phase are obtained. The distillation in step d) is preferably carried out at a top temperature in the range of 40 °C to 100 °C, particularly preferably in the range of 45 °C to 80 °C. The top pressure of the distillation in step d) is preferably 50 to 400 mbar, particularly preferably 80 to 350 mbar. The bottom temperature of the distillation in step d) is preferably 60 °C to 150 °C, particularly preferably 70 °C to 140 °C. The bottom pressure of the distillation in step d) is preferably 70 to 500 mbar, particularly preferably 90 to 450 mbar. It is known that the temperature required or present for a specific separation task during distillation depends on the pressure. Those skilled in the art will be able to select a suitable combination of pressure and temperature parameters based on the separation task to be carried out.

[0061] In distillation, relatively inert isomers and / or reaction-inhibiting substances can be at least partially transferred to the low-boiling phase, whereby the reaction in the high-boiling phase in step e) can proceed at a relatively high reaction rate. In the distillation of step d), a distillate feed stream of 1 wt% to less than 50 wt%, preferably 5 wt% to 40 wt%, particularly preferably 10 wt% to 30 wt% is obtained as the low-boiling phase. Here, the separation of the low-boiling phase in the distillation can be carried out in different ways, which are in principle familiar to those skilled in the art. For example, the separation of a specific amount of the low-boiling phase can thus be achieved by the separation sharpness of the distillation, which can be affected based on the reflux ratio and / or temperature. The separation can also be carried out according to the mass removed, i.e., for example, by a mass flow meter or a similar suitable device or internals. Alternatively, the proportion or amount of the feed stream removed as one or more low-boiling phases in the distillation of step d) can also be set based on other parameters.

[0062] As a result of the distillation in step d), the proportion of the linear isomers of the olefins used in the low-boiling phase is less than the proportion of the linear isomers of the olefins used in the high-boiling phase. This can be checked or determined, for example, by NMR or gas chromatography. Branched isomers are generally of low boiling point and are transferred to the low-boiling phase in a larger proportion. Since in the context of the present invention, the olefins used are generally mixtures of isomeric olefins, it is almost impossible to prevent the linear isomers from also being transferred to the low-boiling phase. However, the distillation should only be carried out under suitable conditions so that the proportion of the linear isomers in the high-boiling phase is higher.

[0063] In principle, all known distillation columns are suitable for the distillation in step d) according to the present invention. These distillation columns generally have internals for increasing the separation sharpness. Suitable internals are, for example, trays, random packings (bulk packings) or structured packings. The trays used are generally bubble-cap trays, sieve trays, valve trays with fixed or movable valves, channel-cap trays or slotted trays. Random packings are generally beds of bulk packings. The bulk packings used are usually Raschig rings, Pall rings, arc saddles, SuperRinge / SuperRinge Plus or saddle packings. For example, structured packings sold by Sulzer under the trade name In addition to the mentioned internals, other suitable internals are also known to those skilled in the art and can equally be used. In a preferred embodiment, at least one distillation column in step c) comprises 10 to 100 trays, preferably 15 to 80 trays.

[0064] The distillation conditions depend on the feed composition and can vary within a wide range. For very pure streams containing only small amounts or no compounds with more or fewer carbon atoms, single-stage distillation is usually sufficient. Then, in the distillation, the more linear isomers to be reacted in step e) are obtained at the bottom. The more branched isomers to be removed are obtained at the top of the single-stage distillation. If the feed stream used contains significant amounts of compounds with long-chain carbon atoms, multi-stage distillation can be advantageous, where the stream required for step e) is removed as the top stream from the second or last distillation column.

[0065] Then, the phases obtained by distillation in step d) are fed to the reaction in the reaction unit in step e). The reaction unit for the reaction in step e) can consist of one or more reactors. The (one or more) reactors can be particularly selected from stirred tank reactors, loop reactors, jet loop reactors, bubble column reactors or combinations thereof. If there are multiple reactors, these reactors can be the same or different. If there are multiple reactors, they can be connected in parallel or in series, or arranged in a mixed manner of parallel and series connections.

[0066] If the reaction is a homogeneous catalytic reaction, the following process conditions are preferred:

[0067] The olefin used in this method undergoes hydroformylation with syngas in the presence of a homogeneously dissolved catalyst system. The molar ratio between the syngas and the feed mixture should be from 6:1 to 1:1, preferably from 3:1 to 1:1, particularly preferably from 2:1 to 1:1. The hydroformylation can optionally be carried out in the presence of a solvent known to those skilled in the art.

[0068] The homogeneous catalyst system that can be used for hydroformylation can contain Co or Rh, preferably Rh, and preferably a phosphorus-containing ligand. In the case of Co, a phosphorus-containing ligand is not actually absolutely necessary. Suitable catalyst systems are well-known to those skilled in the art. In a particularly preferred embodiment, the homogeneous catalyst system contains Rh and a phosphorus-containing ligand or consists of Rh and a phosphorus-containing ligand. The ligands suitable for the catalyst system according to the invention are known to those skilled in the art (see, for example, the textbook "Rhodium Catalyzed Hydroformylation" (since 2002), by P.W.N.M. van Leeuwen) or "Hydroformylation – Fundamentals, Processes and Applications in Organic Synthesis" (since 2016), A. and R. Franke).

[0069] The phosphorus-containing ligand for the catalyst system according to the invention is preferably a phosphine (e.g., TPP (triphenylphosphine)), a mono-phosphite (e.g., Alkanox 240 (tris(2,4-di-tert-butylphenyl) phosphite)) or a bis-phosphite (e.g., Biphephos). Mixtures of ligands can also be used.

[0070] The temperature in homogeneous catalytic hydroformylation is preferably in the range of 80 °C to 250 °C, more preferably in the range of 90 °C to 225 °C, and particularly preferably in the range of 100 °C to 210 °C. The pressure in homogeneous catalytic hydroformylation is preferably in the range of 20 to 350 bar, more preferably in the range of 30 to 325 bar, and particularly preferably in the range of 45 to 300 bar.

[0071] The pressure in hydroformylation generally corresponds to the total gas pressure. In the context of the present invention, the total gas pressure refers to the sum of the pressures exerted by all gaseous substances present, i.e., the pressure of the (total) gas phase. In this process, this particularly corresponds to the sum of the partial pressures of CO and H2, i.e., the total gas pressure is the syngas pressure.

[0072] Homogeneous catalytic hydroformylation can be operated as a liquid discharge process ("liquid recycle") or a gas discharge process ("gas recycle"). These two process variants are known to the person skilled in the art and are described in many textbooks. In the context of the present invention, it is not necessary to specifically select one such method, as the process can in principle be carried out in both ways. In any case, in homogeneous catalysis, it is still important to remove the catalyst system from the reaction effluent. In the case of liquid discharge, this can be achieved, for example, by a flash process or membrane separation. In the case of gaseous discharge, this can be achieved, for example, by condensation and / or washing. This is also known to the person skilled in the art and does not require detailed explanation. The further treatment of the reaction effluent, in particular the separation of the reaction products, is likewise well known to the person skilled in the art and can be carried out, for example, by thermal separation methods such as distillation. In the context of the present invention, thermal separation or thermal separation methods refer to separation methods in which separation is based on boiling points.

[0073] If the reaction is a heterogeneous catalytic hydroformylation, the following process conditions are preferred:

[0074] In the context of the present invention, heterogeneous catalytic hydroformylation is in particular those in which the catalyst system is heterogenized, in particular by being immobilized on a support material (see the introductory discussion in WO 2015 / 028284 A1). Thus, the terms heterogenization and immobilization should be understood to mean that the catalyst system is fixedly present by forming a thin liquid film on the surface and / or pores of a solid support material.

[0075] The characteristics of the heterogeneous catalytic hydroformylation are in particular that the high-boiling phase from step d) passes in gaseous form over a support made of a porous ceramic material, on which a catalyst system is present in heterogeneous form, which catalyst system comprises a metal of Group 8 or 9 of the Periodic Table, at least one organophosphorus ligand, and a stabilizer.

[0076] The temperature in the heterogeneous catalytic hydroformylation can be in the range from 65 °C to 200 °C, preferably from 75 °C to 175 °C, and particularly preferably from 85 °C to 150 °C. The pressure in the heterogeneous catalytic hydroformylation should be greater than 0 bar, but in particular not greater than 35 bar, preferably not greater than 30 bar, and particularly preferably not greater than 25 bar. The molar ratio between the synthesis gas and the feed mixture should be from 6:1 to 1:1, preferably from 5:1 to 3:1. Optionally, the feed mixture can be diluted with an inert gas or a solvent (e.g., with an alkane present in an industrial hydrocarbon stream) to control the reaction.

[0077] The catalyst system used in the hydroformylation process according to the invention preferably comprises a transition metal of Group 8 or 9 of the Periodic Table, in particular iron, ruthenium, iridium, cobalt or rhodium, particularly preferably cobalt and rhodium, at least one organophosphorus ligand, a stabilizer and optionally an ionic liquid.

[0078] The stabilizer is preferably an organic amine compound, particularly preferably an organic amine compound containing at least one 2,2,6,6-tetramethylpiperidine unit.

[0079] The organophosphorus ligand for the catalyst system according to the invention preferably has the general formula (I)

[0080] R'-A-R”-A-R”'(I)

[0081] wherein R', R” and R”' are each an organic residue, and each of the two A is a bridging group -O-P(-O)2-, where two of the three oxygen atoms -O- are each bonded to the residue R' and the residue R”', provided that R' and R”' are not identical. The organic residues R', R” and R”' preferably do not contain terminal trialkoxysilyl groups.

[0082] In a preferred embodiment, R', R” and R”' in the compound of formula (I) are preferably selected from substituted or unsubstituted 1,1'-biphenyl, 1,1'-binaphthyl and o-phenyl, particularly preferably from substituted or unsubstituted 1,1'-biphenyl, provided that R' and R”' are not identical. Particularly preferably, the substituted 1,1'-biphenyl has an alkyl and / or alkoxy group, in particular a C1-C4 alkyl group, particularly preferably a tert-butyl group and / or a methyl group, and / or preferably a C1-C5 alkoxy group, particularly preferably a methoxy group, in the 3,3' and / or 5,5' positions of the 1,1'-biphenyl basic structure.

[0083] The porous ceramic material constituting the support is preferably selected from silicate ceramics, oxide ceramics, nitride ceramics, carbide ceramics, silicide ceramics, and mixtures thereof. The silicate ceramics are preferably selected from aluminosilicates, magnesium silicates, and mixtures thereof, such as bentonite. The oxide ceramics are preferably selected from γ-aluminum oxide, α-aluminum oxide, titanium dioxide, beryllium oxide, zirconium oxide, aluminum titanate, barium titanate, zinc oxide, iron oxide (ferrite), and mixtures thereof. The nitride ceramics are preferably selected from silicon nitride, boron nitride, silicon nitride, aluminum nitride, and mixtures thereof. The carbide ceramics are preferably selected from silicon carbide, boron carbide, tungsten carbide, or mixtures thereof. Mixtures of carbide and nitride ceramics, so-called carbonitrides, can also be considered. The silicide ceramic is preferably molybdenum disilicide. According to the present invention, the support on which the catalyst system is applied preferably consists of carbide ceramics.

[0084] The support can be a monolith, i.e., the support can consist of a ceramic material block (three-dimensional object). Such a block can be formed in one piece or consist of a plurality (i.e., at least two) individual parts that can be joined together to form the block and / or can be joined to each other in a fixed or detachable manner. The support can also be in the form of granules or pellets. The median particle size (d50) of the support can be from 0.1 mm to 7 mm, preferably from 0.3 to 6 mm, and particularly preferably from 0.5 mm to 5 mm. The median particle size can be determined by imaging methods, in particular by the methods mentioned in standard ISO 13322-1 (version: 2004-12-01) and ISO 13322-2 (version: 2006-11-01). The support can be produced in the form of granules or pellets by methods known to those skilled in the art. This can be done, for example, by mechanically crushing a monolith of carbide material, nitride material, silicide material, or mixtures thereof (e.g., using a jaw crusher) and adjusting the particle size of the resulting crushed particles by sieving.

[0085] According to the present invention, the support is composed of a porous ceramic material, i.e., a ceramic material having pores. Different porosities or pore diameters can, in principle, be considered. However, the pore diameter is preferably in the range from 0.9 nm to 30 μm, more preferably in the range from 10 nm to 25 μm, and particularly preferably in the range from 70 nm to 20 μm. The pore diameter can be determined by nitrogen adsorption or mercury porosimetry according to DIN 66133 (version: 1993-06).

[0086] It is possible to additionally apply a so-called washcoat on a support made of ceramic material, which washcoat consists of a ceramic material that is the same as or different from the ceramic material of the support, in particular a ceramic material selected from the above-mentioned ceramic materials, preferably silica. The washcoat itself can be porous or non-porous; the washcoat is preferably non-porous. The particle size of the washcoat is preferably from 5 nm to 3 μm, preferably from 7 nm to 700 nm. The washcoat is used to introduce or create the desired pore size and / or increase the surface area of the support. In particular, the washcoat can be applied by dipping (dip coating) the support into a washcoat solution containing the ceramic material of the washcoat (optionally also as a precursor). The amount of the washcoat present on the support is ≤ 20% by weight, preferably ≤ 15% by weight, particularly preferably ≤ 10% by weight based on the total amount of the support. Then, the catalyst system is applied to the ceramic support provided with the washcoat thus produced. However, preferably, the support does not include a washcoat.

[0087] In principle, the reaction effluent obtained in the heterogeneous catalytic hydroformylation does not have to be free of the catalyst system. Further processing, i.e., for example, the separation of the reaction products, is well known to those skilled in the art and can in principle be carried out by distillation or by another thermal separation method.

[0088] If the reaction is a homogeneous catalytic alkoxycarbonylation, the following process conditions are preferred:

[0089] In alkoxycarbonylation, an olefin reacts with carbon monoxide (CO) and an alcohol (in the present case, a C1 to C6 alcohol) in the presence of a homogeneous catalytic catalyst system to form an ester.

[0090] Carbon monoxide can be provided directly as a feed mixture or by adding a carbon monoxide-containing gas selected from synthesis gas, water gas, producer gas, and other carbon monoxide-containing gases. It is also possible to provide carbon monoxide by first separating the carbon monoxide-containing gas into its components in a manner known to those skilled in the art and then introducing the carbon monoxide into the reaction zone. A certain proportion of hydrogen or other gases may still be present in the carbon monoxide because complete separation is almost impossible to achieve.

[0091] The alcohol used for alkoxycarbonylation is a monohydric alcohol or a polyhydric alcohol (polyhydric alcohol = two or more OH groups) having 1 to 6 carbon atoms. The alcohols suitable for the reaction in step b) or e) are methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, cyclohexanol, phenol, or a mixture thereof. Methanol and ethanol are preferably used in alkoxycarbonylation. If methanol is used, the reaction is also called methoxycarbonylation. When ethanol is used, the reaction is also called ethoxycarbonylation.

[0092] The homogeneous catalyst system for alkoxycarbonylation preferably comprises at least one metal of Groups 8 to 10 of the Periodic Table of the Elements (PSE) or a compound thereof, a phosphorus-containing ligand, and an acid as a cocatalyst.

[0093] The metals of Groups 8 to 10 of the PSE are preferably palladium. The palladium is preferably used as a palladium compound in the form of a precursor compound, which coordinates with the phosphorus-containing ligand. Examples of palladium compounds that can be used as precursor compounds are palladium chloride [PdCl2], palladium(II) acetylacetonate [Pd(acac)2], palladium(II) acetate [Pd(OAc)2], dichloro(1,5-cyclooctadiene)palladium(II) [Pd(cod)2Cl2], bis(dibenzylideneacetone)palladium(0) [Pd(dba)2], tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3], bis(acetonitrile)dichloropalladium(II) [Pd(CH3CN)2Cl2], (cinnamyl)dichloropalladium [Pd(cinnamyl)Cl2]. The compounds [Pd(acac)2] or [Pd(OAc)2] are preferably used. The metal concentration of palladium in alkoxycarbonylation is preferably 0.01 to 0.6 mol%, preferably 0.03 to 0.3 mol%, particularly preferably 0.04 to 0.2 mol% based on the amount of substance of the hydrocarbon used.

[0094] The suitable phosphorus-containing ligand of the catalyst system according to the invention preferably has a bidentate structure. Preferred phosphorus-containing ligands for the catalyst system according to the invention are benzene-based diphosphine compounds, as disclosed, for example, in EP 3121184 A2. The ligand can be combined with palladium in a pre-reaction so that the palladium-ligand complex is introduced into the reaction zone, or added in situ to the reaction and combined with palladium there. In alkoxycarbonylation, the ligand:metal molar ratio can be 1:1 to 10:1, preferably 2:1 to 6:1, particularly preferably 3:1 to 5:1.

[0095] In alkoxycarbonylation, the homogeneous catalyst system further comprises an acid, which can in particular be a Brønsted acid or a Lewis acid. The Lewis acid used can in particular be aluminum trifluoromethanesulfonate, aluminum chloride, aluminum hydride, trimethylaluminum, tris(pentafluorophenyl)borane, boron trifluoride, boron trichloride or a mixture thereof. Among the above Lewis acids, aluminum trifluoromethanesulfonate is preferably used. The Lewis acid is preferably added in a Lewis acid:ligand molar ratio of 1:1 to 20:1, preferably 2:1 to 15:1, particularly preferably 5:1 to 10:1.

[0096] Suitable Brønsted acids preferably have an acid strength with pKs ≤ 5, particularly preferably an acid strength with pKs ≤ 3. The acid strength pKs refers to the pKs value determined under standard conditions (25 °C, 1.01325 bar). For polybasic acids, in the context of the present invention, the acid strength pKs refers to the pKs of the first proton dissociation step. The Brønsted acid is preferably added in a molar ratio of Brønsted acid: ligand of 1:1 to 15:1, preferably 2:1 to 10:1, particularly preferably 3:1 to 5:1.

[0097] The Brønsted acid used can in particular be perchloric acid, sulfuric acid, phosphoric acid, methylphosphonic acid or sulfonic acid. Suitable sulfonic acids are, for example, methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid (PTSA), 2-hydroxypropane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid and dodecylsulfonic acid. Particularly preferred acids are sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid. The acid is preferably sulfuric acid. In contrast, carboxylic acids are less suitable or not suitable at all.

[0098] Homogeneous catalytic alkoxycarbonylation is preferably carried out at a temperature of 25 °C to 140 °C, more preferably at a temperature of 60 °C to 120 °C, and particularly preferably at a temperature of 70 °C to 110 °C. The pressure can be 5 to 60 bar, preferably 10 to 40 bar, particularly preferably 15 to 30 bar.

[0099] A product mixture is obtained by homogeneous catalytic alkoxycarbonylation, which at least contains the ester formed by the reaction, the homogeneous catalyst system, low boilers (such as low-boiling by-products such as ethers), high boilers, unreacted alcohol and possibly unreacted hydrocarbons. Therefore, the product mixture can be subjected to subsequent catalyst removal. For example, this can be achieved by membrane separation, whereby the homogeneous catalyst system and unreacted hydrocarbons and / or unreacted alcohol are enriched in the retentate, while the formed ester is enriched in the permeate. Then the retentate containing the enriched homogeneous catalyst system can be recycled to the reaction zone.

[0100] Further treatment of the permeate, in particular the separation of the ester as the target product, can be carried out by known methods and is in principle familiar to those skilled in the art. One possible method is a thermal separation method such as distillation.

[0101] In a preferred embodiment of the present invention, the light-boiling phase obtained during the distillation in step d) can be hydrogenated. The olefins present in the light-boiling phase are hydrogenated here to form the corresponding alkanes. The hydrogenation is carried out in a hydrogenation unit, which can consist of one or more reactors. The reactors can be operated in a once-through mode or in a recycle mode. In a preferred embodiment of the present invention, the hydrogenation unit comprises at least two reactors. Preferably, the first reactor is operated in a recycle mode and the second reactor is operated in a once-through mode. Here, the first and second reactors can be interconnected by overflow. The advantage of this is that no pump is required between the first and second reactors. In the hydrogenation, hydrogen is preferably used in a stoichiometric excess, particularly preferably in a stoichiometric excess of 5% to 30%.

[0102] The hydrogenation of the light-boiling phase can be carried out on a suitable and known supported catalyst. Suitable supported catalysts comprise at least one transition metal selected from palladium, platinum, rhodium, ruthenium, nickel or mixtures thereof and a support material selected from alumina, silica, titania, magnesia or mixtures thereof. In a preferred embodiment of the present invention, a supported catalyst containing palladium or nickel as the transition metal is used in the hydrogenation of the optional step.

[0103] The hydrogenation is preferably carried out at a temperature of 100 °C to 180 °C, particularly preferably at a temperature of 135 °C to 160 °C. The pressure in the hydrogenation is preferably 5 to 40 bar (gauge pressure), particularly preferably 10 to 30 bar (gauge pressure). The pressure here is particularly generated by the gas phase (i.e., hydrogen). The hydrogenation is preferably carried out in the liquid phase. After the hydrogenation, phase separation known to those skilled in the art can be carried out to separate the gas phase containing unreacted hydrogen and optionally also containing a small amount of hydrocarbons from the liquid phase. Description of the Drawings

[0104] Figure 1 Shows an overview of the GC fractions of a tributene stream. Detailed Description

[0105] Examples

[0106] Hydroformylation of Tributene

[0107] 49 kg of tributene (feed) are distilled in a distillation column (80 l) with multiple packing beds (Montz A3-1000) at a temperature of 70 °C (top) or 110 °C (bottom) and a pressure of 90 mbar (top) or 120 mbar (bottom). 20% to 25% are removed from the tributene used as distillate (= light-boiling substances). The remaining 75% to 80% remain in the bottom product of the column and are thus heavy-boiling substances.

[0108] The compositions of three different tributene feed streams, distillates, and bottoms were studied. Due to the large number of isomers of tributene, it is difficult to identify each isomer. Therefore, the proportions of different fractions in the tributene feed stream were studied using gas chromatography (GC capillary column, Petrocol, DH 150). For simplicity, they are identified below based on their retention times (see also Figure 1 ):

[0109] - highly branched isomers with retention times of 70 to 109 minutes,

[0110] - moderately branched isomers with retention times of 109 to 134 minutes, and

[0111] - less branched isomers with retention times of 134 to 180 minutes

[0112] An overview of the proportions of the above fractions in the tributene feed stream is given in Table 1.

[0113] Table 1: Proportions of the fractions in the tributene feed streams (mass %)

[0114] Feed (before distillation) Distillate (low boilers) Bottoms (high boilers) Highly branched isomers 23.5％ 93.5％ 0％ Moderately branched isomers 61％ 6.5％ 79％ Less branched isomers 15.5％ 0％ 21％

[0115] From the analysis of the feed, distillate, and bottoms, it can be seen that distillation mainly removes the highly branched tributene isomers from the feed and ultimately into the distillate. The proportion of the less branched isomers in the bottoms is significantly higher than that in the feed or distillate.

[0116] Hydroformylation was carried out in a 100 mL autoclave using three different tributene feed streams, distillates, and bottoms, respectively. The catalyst used here is rhodium (40 ppm of Rh), and a 5-fold molar excess (ratio of total phosphorus to rhodium) of ligand (Alkanox 240). The temperature was 130 °C to 150 °C. In addition, in each case, hydroformylation was carried out at a syngas pressure of 235 to 250 bar (CO / H2 ratio = 1:1 (vol %)). The solvent used in each case was 40 to 46 g of toluene. In each case, samples were taken at 10 minutes, 60 minutes, and 180 minutes after the start of the reaction, and the reaction conversion (conversion = amount of substance at time t / amount of substance (at the start of the reaction)) was studied. The results of hydroformylation are shown in Table 2.

[0117] Table 2: Reaction conversions in hydroformylation

[0118]

[0119] As can be seen from Table 2, a significant acceleration of the reaction can be achieved by pre-distillation. The conversion in each case is about 5% higher when using the bottoms stream compared to the feed.

[0120] Hydroformylation of butadiene

[0121] A) One-stage reaction

[0122] 21.5 t / h of butadiene (feed) is distilled in a distillation column with 42 trays, with a top temperature of 58 °C and a bottom temperature of 62 °C, and a corresponding top pressure of 0.1 bar and a bottom pressure of 0.15 bar. Approximately 20% (4.44 t / h) is separated from the butadiene used as the distillate (= low boilers). The remaining 80% is taken out in the bottoms and is thus high boilers.

[0123] The composition of the butadiene feed stream and the bottoms was studied using GC (gas chromatography). An overview is shown in Table 3:

[0124] Table 3: Proportion of different isomer groups in each butadiene stream

[0125]

[0126]

[0127] The linearity of butadiene is described by the ISO index and represents the average number of methyl branches in the dimer. For example (using butene as the reactant), for the ISO index of the C8 fraction, thus n-octene contributes 0, methylheptene contributes 1, and dimethylhexene contributes 2. The lower the ISO index, the more linear the structure of the molecules in the corresponding fraction. The ISO index is calculated according to the following general formula, where the proportion of each dimer fraction is based on the total dimer fraction:

[0128]

[0129] Thus, a dimer mixture with an ISO index of 1.0 has exactly one degree of methyl branching per dimer molecule on average.

[0130] The ISO index of the feed is 1.03 and the ISO index of the bottoms is 0.88. It can be seen from this that the bottoms contain a higher proportion of straight-chain isomers.

[0131] Hydroformylation was carried out separately in a 100 mL autoclave using the feed and bottoms. The catalyst used here was rhodium (Rh at 20 ppm), and a 5-fold molar excess (ratio of total phosphorus to rhodium) of ligand (tris(2,4-di-tert-butylphenyl) phosphite (TDTBPP)). The temperature was about 140 °C. In addition, in each case, the hydroformylation was carried out at a syngas pressure of about 235 bar (CO / H2 ratio = 1:1 (vol%)). The solvent used in each case was 150 mL of toluene. In each case, samples were taken at 10 minutes, 30 minutes, 60 minutes, and 180 minutes after the start of the reaction, and the reaction conversion (conversion = amount of substance at time t / amount of substance (at the start of the reaction)) was studied. The results of the hydroformylation are shown in Table 4.

[0132] Table 4: Reaction conversion in the hydroformylation of the butadiene stream

[0133]

[0134] As can be seen from Table 4, a significant acceleration of the reaction can be achieved by pre-distillation. Compared with the feed, in each case, the conversion using the bottoms stream is up to 20% higher.

[0135] B) Two-stage reaction

[0136] The hydroformylation was carried out as described in A). The difference is that there is a second reactor in which the hydroformylation is carried out.

[0137] Approximately 24% was separated as distillate (= low boilers) from the butadiene used. The remaining 76% was taken out in the bottoms, and thus is high boilers. The composition of the butadiene stream feed, distillate, and bottoms was detected using GC (gas chromatography). An overview is shown in Table 5:

[0138] Table 5: Proportion of different isomer groups in each butadiene stream

[0139] Feed (before distillation) Distillate (low boilers) Bottoms (high boilers) Dimethylhexene 37％ 51％ 30％ Methylheptene 58％ 48％ 64％ Octene 5％ 1％ 6％

[0140] Hydroformylation was carried out with all three streams. The temperature was 180 °C and the syngas pressure was 265 bar. The results of the hydroformylation are shown in Table 6.

[0141] Table 6: Reaction conversion during the second-stage hydroformylation

[0142] Conversion rate / % After 180 minutes Feed (before distillation) 72.9 Distillate (low boilers) 70.7 Bottoms (high boilers) 77.6

[0143] Table 6 shows that the reaction can be significantly accelerated by pre-distillation. Compared with the feed, in each case, the conversion using the bottoms stream can be up to about 5% higher.

Claims

1. A process for reacting olefins having 4 to 20 carbon atoms, comprising the steps of: a) providing a feed stream comprising at least a linear olefin and a branched olefin each having the same number of carbon atoms; b) feeding the feed stream from step a) to a reaction unit comprising one or more reactors and carrying out a reaction in the reaction unit to obtain a product mixture, wherein the reaction is a heterogeneously catalyzed hydroformylation in the presence of synthesis gas, a homogeneously catalyzed hydroformylation in the presence of synthesis gas or a homogeneously catalyzed alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol, c) separating a residue stream from the product mixture of step b), wherein the residue stream comprises at least unreacted olefins; d) distilling the residue stream from step c) in at least one distillation column to obtain at least one low boiler phase and one high boiler phase, wherein 1% by weight to less than 50% by weight of the distilled feed stream is obtained as low boiler phase, and wherein the proportion of linear olefins in the low boiler phase is less than the proportion of linear olefins in the high boiler phase; and e) supplying the high boiler phase from step d) to a reaction unit comprising one or more reactors and carrying out a reaction in said reaction unit, wherein the reaction is a heterogeneously catalyzed hydroformylation in the presence of synthesis gas, a homogeneously catalyzed hydroformylation in the presence of synthesis gas or a homogeneously catalyzed alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol.

2. The process according to claim 1, wherein olefins having 7 to 16 carbon atoms, preferably 7 to 12 carbon atoms, are reacted in the process.

3. The process according to claim 1 or 2, wherein the homogeneous catalyst system in the hydroformylation comprises Co or Rh and preferably comprises a phosphorus-containing ligand.

4. The process according to claim 1 or 2, wherein the homogeneous catalyst system in the alkoxycarbonylation comprises a metal from Group 8 to 10 of the Periodic Table of Elements (PSE) or a compound thereof, a phosphorus-containing ligand and an acid as a promoter. 5 . The process according to claim 1 , wherein the low boiler phase obtained in step d) is subjected to a hydrogenation.

6. The process according to claim 5, wherein the hydrogenation is carried out at a temperature of 100°C to 180°C.

7. The process according to claim 5 or 6, wherein hydrogen is used in a stoichiometric excess, preferably in a stoichiometric excess of 5% to 30%, in the hydrogenation.

8. The process according to claim 5 , wherein a supported catalyst is used in the hydrogenation, the supported catalyst comprising at least one transition metal selected from palladium, platinum, rhodium, ruthenium, nickel or mixtures thereof and a support material selected from aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide or mixtures thereof.

9. The process according to any one of the preceding claims, wherein the distillation in step d) is carried out at a top temperature in the range of 40 to 100°C, preferably in the range of 55 to 80°C.

10. The process according to any one of the preceding claims, wherein the pressure at the top during the distillation in step d) is from 50 to 400 mbar, preferably from 80 to 350 mbar.

11. The process according to any one of the preceding claims, wherein the at least one distillation column in step d) comprises 10 to 100 trays, preferably 15 to 80 trays.

12. The process according to claim 1, wherein in step d), 5 to 40% by weight, preferably 10 to 30% by weight, of the distilled feed stream is obtained as low boiler phase.

13. The process according to any one of the preceding claims, wherein the separation of the residue stream in step c) is carried out by thermal separation, wherein the thermal separation is preferably distillation, thin film evaporation, falling film evaporation or a combination of two or more thereof.

14. The process according to any one of the preceding claims, wherein the conversion of the reaction in step b) is a maximum of 95%, preferably a maximum of 92%, further preferably a maximum of 90%, further preferably a maximum of 88%, particularly preferably a maximum of 85%.

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