Olefin reaction process with pre-separated feed stream

Abstract

The invention relates to an olefin reaction process in which a feed stream is separated in advance. The invention relates to a method for reacting olefins having 4 to 20 carbon atoms, in which first a feed stream used containing at least linear olefins and branched olefins is separated into two streams A and B. The stream A is distilled prior to the reaction and only the high-boiling phase obtained in the distillation is reacted, i.e. Heterogeneous catalytic hydroformylation, homogeneously catalytic hydroformylation or homogeneously catalytic alkoxycarbonylation.

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 the feed stream used, which contains linear and branched olefins, is first separated into two streams A and B. Stream A is distilled before the reaction, and only the high-boiling phase obtained in this distillation is reacted, namely in a multiphase catalytic hydroformylation, a homogeneous catalytic hydroformylation or a homogeneous catalytic alkoxycarbonylation. Background Art

[0002] In the context of the present invention, the term "reaction" is to be understood as meaning three different reactions: multiphase catalytic hydroformylation, homogeneous catalytic hydroformylation and homogeneous catalytic alkoxycarbonylation, in which the feed stream used containing olefins having 4 to 20 carbon atoms is reacted. These three reaction types are organic chemical processes known 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 the presence of a suitable homogeneous catalyst system to form the corresponding aldehyde. Hydroformylation is an industrial process operated in factories, in which several thousand to several hundred thousand tons (kt) of aldehyde can be produced annually. 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 multiphase 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 multiphase form on a monolithic support made of a porous ceramic material is used. The multiphase 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 ester thus obtained. 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) (such as palladium) or their compounds, phosphorus-containing ligands and an acid as a cocatalyst.

[0006] The above reaction processes, namely 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 reaction conversion and / or selectivity for the desired product (aldehyde in the case of hydroformylation or ester in the case of alkoxycarbonylation), are not impaired, so the advantage of a higher reaction rate is not reversed.

[0007] In the case of a high mass flow rate of the feed stream, there is another problem. To be able to handle these, large reaction and distillation units are required to be able to handle the high mass flow rate. However, large reaction and distillation units are associated with high investment costs. On the other hand, some reaction and distillation units can be designed large enough to be able to handle the high mass flow rate. Summary of the Invention

[0008] Accordingly, it is an object of the present invention to provide a process for the reaction of olefins by means of which a higher reaction rate can be achieved while the reaction conversion and / or the selectivity for the desired product (aldehyde in the case of hydroformylation or ester in the case of alkoxycarbonylation) are not significantly impaired. In addition, it should also be possible to handle a large feed stream.

[0009] This object is achieved by the process according to the claims. Preferred embodiments are given in the dependent claims. The process according to the invention is a process for reacting olefins having 4 - 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) dividing the feed stream provided in step a) into at least two streams, namely stream A and stream B;

[0012] c) distilling stream A in at least one distillation column to obtain at least one low - boiling phase and one high - boiling phase, wherein 1 wt% to less than 50 wt% of the distilled feed stream is obtained as the low - boiling phase, and wherein the proportion of linear olefins in the low - boiling phase is less than the proportion of linear olefins in the high - boiling phase; and

[0013] d) supplying the high - boiling phase from step c) to a reaction unit comprising one or more reactors and carrying out a reaction in the reaction unit, wherein the reaction is heterogeneous catalytic hydroformylation in the presence of synthesis gas, homogeneous catalytic hydroformylation in the presence of synthesis gas, or homogeneous catalytic alkoxycarbonylation in the presence of carbon monoxide and a C1 - C6 alcohol.

[0014] One of the key method steps is the separation in step b). This involves separating the feed stream used into at least two streams A and B. The separation ensures that a single larger feed stream is divided into several smaller streams. This makes it easier to handle these smaller streams.

[0015] Another key method step here is step c), the distillation of the feed stream and the use of only the high-boiling phase for the reaction in step d). The advantage of the method according to the invention is that the reaction rate of the reaction in step d) is higher than in the case of known methods without such distillation. The reason may be that relatively inert isomers and / or reaction-inhibiting substances tend to be separated from the feed stream together with the low-boiling phase during the distillation and thus are not supplied 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 very particularly preferably comprising an olefin having 8 and / or 12 carbon atoms is used. The feed stream used is generally an industrially available hydrocarbon stream containing at least different isomers of the respective olefin. These feed streams contain at least linear 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 so that the reaction in step d) can 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 mixture of linear butenes 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 the light petroleum fractions produced by refineries or crackers.

[0018] Higher olefins can in particular be obtained by oligomerization (e.g., 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 being separated by distillation 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 methods can also be used.

[0019] The feedstream provided in step a) may have been previously subjected to one or more additional processing steps to convert certain components in the feedstream or remove them from the stream. An example is the removal of impurities that may be harmful to the catalyst, such as substances or compounds containing oxygen, nitrogen or sulfur. 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 many times.

[0020] The feedstream provided in step a) is divided in step b) into at least two streams, namely stream A and stream B. In principle, the feedstream can also be divided into more than two streams. Then additional streams will be designated by subsequent capital letters C, D, etc. In this context, "division" means separating the total stream into two or more individual streams having the same composition. Thus, the division is not achieved by thermal separation (e.g., distillation), but rather, for example, by a distributor in a pipeline. This is known to the person skilled in the art. The division can also be adjusted based on predetermined parameters (mass flow rate, quantity, etc.) and thus optionally carried out automatically. Suitable for this purpose are, for example, a proportional regulator with split range or a stepper motor with position feedback.

[0021] The stream A obtained from step b) is distilled in step c), where a high-boiling phase and a low-boiling phase are obtained. The distillation in step c) 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 c) is preferably 50 to 400 mbar, particularly preferably 80 to 350 mbar. The bottom temperature of the distillation in step c) is preferably 60 °C to 150 °C, particularly preferably 70 °C to 140 °C. The bottom pressure of the distillation in step c) is preferably 70 to 500 mbar, particularly preferably 90 to 450 mbar. It is known that the temperature required for a specific separation task or the temperature present during distillation depends on the pressure. A person 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.

[0022] In the 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 d) can proceed at a relatively high reaction rate. In the distillation of step c), 1 wt% to less than 50 wt%, preferably 5 wt% to 40 wt%, particularly preferably 10 wt% to 30 wt% of the distilled feed stream is obtained as the low-boiling phase. Here, the removal of the low-boiling phase in the distillation can be carried out in different ways, which are in principle familiar to a person skilled in the art. For example, the removal of a specific amount of the low-boiling phase can thus be achieved by the separation sharpness of the distillation, which can be influenced based on the reflux ratio and / or temperature. The removal 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 internal component. Alternatively, the proportion or amount of the feed stream removed as one or more low-boiling phases in the distillation of step c) can also be set based on other parameters.

[0023] As a result of the distillation in step c), the proportion of the straight-chain isomers of the olefins used in the low-boiling phase is less than the proportion of the straight-chain 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 low-boiling and are transferred to the low-boiling phase in a larger proportion. Since in the context of the present invention, the olefins used are usually mixtures of isomeric olefins, it is almost impossible to prevent the straight-chain 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 straight-chain isomers in the high-boiling phase is higher.

[0024] The distillation in step c) is carried out in at least one distillation column, i.e., it can be carried out in one or more distillation columns. If there is only a single distillation column, the stream required for the reaction in step d) will be taken out as the bottom stream from the distillation column. If there are multiple distillation columns, only the high-boiling phase from the first distillation column is supplied to the next distillation column, and the low-boiling phase from the last distillation column is supplied to the reaction in step d).

[0025] In principle, all known distillation columns are suitable for the distillation in step c) according to the present invention. These distillation columns generally have internal components for improving the separation sharpness. Suitable internal components 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 bulk packing beds. The bulk packings used are usually Raschig rings, Pall rings, saddle packings, SuperRinge / SuperRinge Plus or saddle packings. For example, structured packings sold by Sulzer company under the trade name . In addition to the internal components mentioned, other suitable internal components are also known to those skilled in the art and can also be used. In a preferred embodiment, at least one distillation column in step c) comprises 10 to 100 trays, preferably 15 to 80 trays.

[0026] The distillation conditions depend on the feed composition and can vary within a wide range. For a very pure stream containing only a small amount or no compounds with more or fewer carbon atoms, single-stage distillation is usually sufficient. Then, in the distillation, more linear isomers to be reacted in step d) are obtained at the bottom. More branched isomers to be removed are obtained at the top of the single-stage distillation. If the feed stream used contains a significant amount of compounds with long-chain carbon atoms, multi-stage distillation can be advantageous, where the stream required for step c) is removed as the top stream from the second or last distillation column.

[0027] Then, the high-boiling phase obtained by distillation in step c) is fed to the reaction in the reaction unit in step d). The reaction unit for the reaction in step d) can consist of one or more reactors. The (one or more) reactors can particularly 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.

[0028] If the reaction is a homogeneous catalytic reaction, the following process conditions are preferred:

[0029] The olefins used in the process are hydroformylated 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.

[0030] Homogeneous catalyst systems 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 systems 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).

[0031] The phosphorus-containing ligand for the catalyst systems 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.

[0032] 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.

[0033] 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.

[0034] Homogeneous catalytic hydroformylation can be operated as a liquid discharge process ("liquid recycle") or a gas discharge process ("gas recycle"). Both of these 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.

[0035] If the reaction is a heterogeneous catalytic hydroformylation, the following process conditions are preferred:

[0036] 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 a solid support material.

[0037] Heterogeneous catalytic hydroformylation is characterized in particular in that the high-boiling phase from step c) passes in gaseous form over a support composed 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.

[0038] 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.

[0039] 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.

[0040] The stabilizer is preferably an organic amine compound, particularly preferably an organic amine compound containing at least one 2,2,6,6-tetramethylpiperidine unit.

[0041] The organophosphorus ligand for the catalyst system according to the invention preferably has the general formula (I)

[0042] R'-A-R”-A-R”'(I)

[0043] wherein R', R” and R”' are each an organic residue, and A is 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.

[0044] 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, and / or preferably C1-C5 alkoxy groups, particularly preferably methoxy. 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)).

[0045] 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.

[0046] 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.

[0047] According to the present invention, the support is made 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).

[0048] 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 silicon oxide. 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 generate 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 (optionally also as a precursor) of the washcoat. 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.

[0049] In principle, the reaction product 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.

[0050] If the reaction is a homogeneous catalytic alkoxycarbonylation, the following process conditions are preferred:

[0051] 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.

[0052] 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.

[0053] 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 d) 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Suitable Bronsted 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 Bronsted acid is preferably added in a molar ratio of Bronsted acid: ligand of 1:1 to 15:1, preferably 2:1 to 10:1, particularly preferably 3:1 to 5:1.

[0059] The Bronsted 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.

[0060] 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.

[0061] 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 any 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.

[0062] 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.

[0063] Likewise, the stream B obtained in the separation in step b) and any other stream obtained in this separation can be distilled before the reaction to remove low-boiling or highly branched isomers. The conditions here can be the same as those proposed above for stream A. It is readily understood that the distillation is then carried out in its own distillation unit and not in the same distillation unit as the distillation of stream A. In principle, stream B can also be separated again and only at least a part thereof is supplied to the subsequent method steps.

[0064] According to the present invention, at least a part of stream B is preferably introduced into a reaction unit comprising one or more reactors and undergoes a reaction therein, wherein the reaction is a heterogeneous catalytic hydroformylation in the presence of syngas, a homogeneous catalytic hydroformylation in the presence of syngas, a homogeneous catalytic alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol, or hydrogenation.

[0065] The heterogeneous catalytic hydroformylation in the presence of syngas, the homogeneous catalytic hydroformylation in the presence of syngas, and the homogeneous catalytic alkoxycarbonylation in the presence of carbon monoxide and a C1 to C6 alcohol can have the same characteristics as those already described in the reaction with the high-boiling fraction in step d) previously.

[0066] If the reaction undergone by at least a part of stream B is hydrogenation, the olefins present are hydrogenated 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 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 connected to each other 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%.

[0067] The hydrogenation of at least a part of stream B can be carried out on a suitable and known supported catalyst. The suitable supported catalyst comprises at least one transition metal selected from palladium, platinum, rhodium, ruthenium, nickel, or a mixture thereof and a support material selected from alumina, silica, titania, magnesia, or a mixture 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 in an optional step.

[0068] 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.

[0069] It has been mentioned that the separation in step b) is controlled. A viable parameter that can be used to control the separation is the market demand for the different reaction products. For example, if there is a large demand for alkanes or alkane mixtures, the separation in step b) can be controlled such that a larger proportion of the feed stream is sent to hydrogenation. Conversely, if there is a large demand for the hydroformylation or alkoxycarbonylation products, the separation in step b) can be controlled such that a larger proportion of the feed stream is sent to these reactions. Therefore, it is preferred that the separation in step b) varies in such a way that the proportion obtained as stream A in the feed stream changes during the course of the process.

[0070] In a preferred embodiment of the invention, the light-boiling phase obtained in the distillation of step c) 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 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 connected to each other by overflow. The advantage of this is that no pumps are 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%.

[0071] 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, titanium dioxide, magnesium oxide or mixtures thereof. In a preferred embodiment of the invention, a supported catalyst containing palladium or nickel as the transition metal is used in the hydrogenation of the optional step.

[0072] 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

[0073] Figure 1 Shows an overview of the GC fractions of a tributene stream. Detailed Description

[0074] Examples

[0075] Hydroformylation of Tributene

[0076] 49 kg of tributene (feed) was 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% was removed from the tributene used as distillate (= low boilers). The remaining 75% to 80% remained in the bottoms and were thus high boilers.

[0077] The composition of three different tributene feed streams, distillates, and bottoms was studied. Due to the large number of isomers of tributene, it was difficult to identify individual isomers, so the proportions of different fractions in the tributene streams were studied using gas chromatography (GC capillary column, Petrocol, DH 150). For simplicity, they are thus identified below based on their retention times (see also Figure 1 ):

[0078] - highly branched isomers with a retention time of 70 to 109 minutes,

[0079] - moderately branched isomers with a retention time of 109 to 134 minutes, and

[0080] - less branched isomers with a retention time of 134 to 180 minutes

[0081] An overview of the proportions of the above - mentioned fractions in the tributene streams is given in Table 1.

[0082] Table 1: Proportions of fractions in each tributene stream (mass %)

[0083]

[0084] From the analysis of the feed, distillate, and bottoms, it can be seen that distillation mainly removes highly branched tributene isomers from the feed and ultimately into the distillate. The proportion of less branched isomers in the bottoms is significantly higher than in the feed or distillate.

[0085] Hydroformylation was carried out in a 100 ml autoclave using three different tributene feeds, the distillate, and the bottoms, respectively. The catalyst used here was rhodium (Rh at 40 ppm), and the ligand (Alkanox 240) was in a 5-fold molar excess (ratio of total phosphorus to rhodium). The temperature was 130 °C to 150 °C. In addition, in each case, the hydroformylation was carried out at a syngas pressure of 235 to 250 bar (CO / H2 ratio = 1:1 (vol%)) and 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 the hydroformylation are shown in Table 2.

[0086] Table 2: Reaction conversion in hydroformylation

[0087]

[0088] As can be seen from Table 2, a significant acceleration of the reaction can be achieved by pre-distillation. The conversion in each case was about 5% higher when using the bottoms stream compared to the feed.

[0089] Hydroformylation of dibutene

[0090] 21.5 t / h of dibutene (feed) was distilled in a distillation column with 42 trays, with a top temperature of 58 °C and a bottom temperature of 62 °C, and the corresponding top pressure of 0.1 bar and bottom pressure of 0.15 bar. Approximately 20% (4.44 t / h) of the dibutene used was separated as the distillate (= low boilers). The remaining 80% was taken out in the bottoms stream and was thus the high boilers.

[0091] The composition of the dibutene feed stream and the bottoms stream was studied using GC (gas chromatography). An overview is shown in Table 3:

[0092] Table 3: Proportion of different isomer groups in each dibutene stream

[0093] Feedstock (before distillation) Bottoms (high boilers) Dimethylhexene 19％ 8％ Methylheptene 65％ 72％ Octene 16％ 20％

[0094] The linearity of dibutene is described by the ISO index, which 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:

[0095]

[0096] Thus, the dimer mixture with an ISO index of 1.0 has exactly one degree of methyl branching per dimer molecule on average.

[0097] The ISO index of the feed is 1.03, and the ISO index of the bottoms is 0.88. It can be seen that the bottoms contain a higher proportion of linear isomers.

[0098] Hydroformylation was carried out in a 100 mL autoclave using the feed and the bottoms, respectively. The catalyst used here is rhodium (20 ppm of Rh), and a 5-fold molar excess (ratio of total phosphorus to rhodium) of the 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 (volume%)). 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.

[0099] Table 4: Reaction conversion in the hydroformylation of the butadiene stream

[0100]

[0101] As can be seen from Table 4, a significant acceleration of the reaction can be achieved by pre-distillation. Compared with the feed, the conversion is up to 20% higher in each case when using the bottoms stream.

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) dividing the feed stream provided in step a) into at least two streams, stream A and stream B; c) distilling stream A 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; as well as d) supplying the high boiler phase from step c) 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 at least a portion of stream B is fed to a reaction unit comprising one or more reactors and reacted in said reaction unit, wherein said 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 or a hydrogenation.

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

4. The process according to any one of the preceding claims, wherein the homogeneous catalyst system in the hydroformylation comprises Co or Rh and preferably comprises a phosphorus-containing ligand.

5. The process according to any one of the preceding claims, wherein the homogeneous catalyst system in the alkoxycarbonylation comprises a metal from Groups 8 to 10 of the Periodic Table of Elements (PSE) or a compound thereof, a phosphorus-containing ligand and an acid as promoter.

6. The process according to claim 1, wherein the low boiler phase obtained in step c) is subjected to a hydrogenation.

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

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

9. The process according to claim 6 , 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.

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

11. The process according to any one of the preceding claims, wherein the top pressure in the distillation of step b) is from 50 to 250 mbar, preferably from 80 to 150 mbar.

12. The process according to any one of the preceding claims, wherein the bottom temperature in the distillation of step c) is from 60 to 150°C, preferably from 70 to 140°C.

13. The process according to claim 1, wherein the separation in step b) is varied in such a way that the proportion of the feed stream which is obtained as stream A changes during the process.

14. The process according to any one of the preceding claims, wherein the at least one distillation column comprises internals, wherein the internals are trays, non-structured packing (random packing) or structured packing.

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

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