Method for producing alcohol from hydrocarbons

Abstract

To provide a process for preparing an alcohol by hydrogenating an ester.SOLUTION: The preparing process includes steps of: preparing an ester by alkoxycarbonylating a C2 to C16 hydrocarbon having at least one multiple bond, preferably having at least one olefinic double bond; and hydrogenating the ester with hydrogen in a hydrogenation zone in the presence of a heterogeneous catalyst system to obtain a target alcohol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a process for the production of alcohols by hydrogenation of esters obtained by alkoxycarbonylation of C2-C16 hydrocarbons with at least one multiple bond, preferably at least one olefinic double bond, in which the homogeneous catalyst system used is separated from the liquid product mixture by membrane separation. In one embodiment of the invention, the esters thus formed are converted into other esters by transesterification and then hydrogenated. [Background technology]

[0002] The production of alcohols in large-scale industrial chemistry is mainly achieved by hydroformylation to produce aldehydes, followed by hydrogenation of the aldehydes to alcohols. The production of alcohols by hydroformylation and subsequent hydrogenation is a long-established and proven industrial process, but there is still room for improvement. One of the problems with this synthesis route is the usually high pressures and temperatures of the hydroformylation, i.e. the relatively high technical requirements placed on the plants used, i.e. the plants must be able to withstand both pressures and temperatures.

[0003] Another fundamental problem in the production of alcohols by hydroformylation and subsequent hydrogenation is the high reactivity of the aldehydes formed as intermediates. Aldehydes are very reactive and react further to produce undesirable by-products before the desired hydrogenation can occur. These undesirable by-products are mostly high boiling materials that must be laboriously separated from the reaction mixture and disposed of. Moreover, the formation of high boilers means that aldehydes are lost and can no longer be converted into the desired alcohols. This reduces the selectivity of the overall process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2009 / 012323 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is therefore to provide an alternative synthetic route for the production of alcohols, which requires fewer operations in the carbonylation step. A further important object is that the production process can be carried out on a large industrial scale. The focus is on alternative synthetic techniques to the classical synthesis, which provide the classical hydroformylation products in better quality. Furthermore, the new synthetic route to be established should result in a reduced level of undesired by-products.

[0006] Patent document 1 describes a similar synthesis method. However, the problem with Patent document 1 is that the separation of the ester from the product mixture is carried out by distillation immediately after the preparation of the ester. In Patent document 1, the catalyst-containing product mixture is obviously distilled. However, as a result of the heat treatment, the catalyst may be deactivated or even separated, i.e. it is no longer usable. In particular, the transition metals commonly used must be removed from the reactor and replaced, which entails high costs. Therefore, another fundamental task was to improve the known process by reducing its complexity and costs. [Means for solving the problem]

[0007] This object is achieved by a two-stage process in which in a first stage, a hydrocarbon having at least one multiple bond is reacted with carbon monoxide and an alcohol to form an ester by alkoxycarbonylation, and in a second stage, the ester is reacted with hydrogen to form the desired target alcohol, in which a portion of the alcohol initially used is released again in the second stage of the process.

[0008] According to the present invention, a method for producing a target alcohol comprises the following steps: a) producing an ester by reacting (carbonylation) a C2-C16 hydrocarbon having at least one multiple bond with carbon monoxide and a mono- or polyalcohol (two or more OH groups) having 1 to 50 carbon atoms or a mixture of two or more mono- and / or polyalcohols, alcohol A, used in a molar ratio of 2 to 20 relative to said C2-C16 hydrocarbon (alcohol:C2-C16 hydrocarbon), in the presence of a homogeneous catalyst system comprising at least one metal or compound thereof from groups 8 to 10 of the Periodic Table of the Elements, a phosphorus-containing ligand and an acid, to obtain a liquid product mixture in a reaction zone; b) performing a membrane separation step for separating the homogeneous catalytic system from the liquid product mixture, enriching the homogeneous catalytic system and further unconverted hydrocarbons and / or unconverted alcohol A in a retentate and enriching the ester in the permeate formed in step a), where as membrane material the membrane material used is acid-stable, i.e. stable for at least 300 hours in the presence of the acid of the catalytic system, and is an OSN-based (Organic Solvent Nanofiltration) membrane material comprising at least one separation active layer, and where the retentate is returned to the reaction zone of step a) and the permeate is sent to step c); c) separating the ester formed in step a) from the permeate in at least one separation step selected from thermal separation, e.g. distillation, extraction, crystallization and membrane separation; d) hydrogenating the ester separated in step c) with hydrogen in the presence of a heterogeneous catalytic system in a hydrogenation zone to obtain an alcohol mixture comprising at least the target alcohol, the separated alcohol A and unconverted ester; e) separating the desired alcohol formed in step d) by at least one separation process selected from thermal separation, e.g. distillation, extraction, crystallization, and membrane separation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The hydrocarbons used in the reaction of step a) have at least one multiple bond. Preferably, they are hydrocarbons with at least one olefinic double bond, particularly preferably with one olefinic double bond. In principle, the number of carbon atoms of the compound with at least one multiple bond, preferably with at least one olefinic double bond, is not limited. However, technically, the carbonylation of C2-C20 hydrocarbons with at least one multiple bond, preferably with at least one olefinic double bond, is merely relevant. In a preferred embodiment of the present invention, C3-C16 hydrocarbons, preferably C4-C12 hydrocarbons with at least one multiple bond, preferably with at least one olefinic double bond, may be used. In particular, n-alkenes, isoalkenes, cycloalkenes and aromatic alkenes with 2-20 carbon atoms, preferably with 3-16 carbon atoms, more preferably with 4-12 carbon atoms, may be mentioned.

[0010] The hydrocarbon may contain at least one olefinic double bond and one or more further functional groups. Examples of suitable functional groups are carboxyl, thiocarboxyl, sulfo, sulfinyl, carboxylic anhydride, imide, carboxylate, sulfonate, carbamoyl, sulfamoyl, cyano, carbonyl, carbonothioyl, hydroxyl, sulfhydryl, amino, ether, thioether, aryl, heteroaryl or silyl groups and / or halogen substituents.

[0011] Particularly preferred hydrocarbons used in step a) of the process according to the invention comprise only one olefinic double bond, in particular n-alkenes and isoalkenes with 2 to 20 carbon atoms, preferably with 3 to 16 carbon atoms, more preferably with 4 to 12 carbon atoms. The hydrocarbons used are preferably unsubstituted.

[0012] The hydrocarbons used, which have an olefinic double bond, are reacted in step a) with carbon monoxide (CO) and alcohol to form the corresponding ester. Carbon monoxide can be provided directly as a feed mixture or by adding a carbon monoxide-containing gas selected from synthesis gas, water gas, generation gas and other carbon monoxide-containing gases. The carbon monoxide-containing gas can also be separated into its components in a manner known to those skilled in the art and carbon monoxide can be fed to the reaction zone to provide carbon monoxide. Carbon monoxide may contain a certain proportion of hydrogen or other gases, since complete separation is almost impossible.

[0013] The alcohol used in step a) is a mono- or polyalcohol (2 or more OH groups) with 1 to 50 carbon atoms, preferably with 1 to 15 carbon atoms, more preferably with 1 to 10 carbon atoms, or a mixture of 2 or more monoalcohols and / or polyalcohols. In a preferred embodiment, the polyalcohol is a diol, triol or tetraol, preferably a diol or triol, with the above number of carbon atoms. Suitable alcohols for the reaction in step a) are methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butyl alcohol (tert-Butanol), 3-pentanol, 2-propylheptanol, cyclohexanol, phenol, or mixtures thereof.

[0014] When the alcohol used in step a) is a monoalcohol, the molar ratio to the hydrocarbon used (monoalcohol:hydrocarbon) is 2 to 20, preferably 3 to 10, more preferably 4 to 6. That is, the number of moles of the monoalcohol added is in excess of the hydrocarbon used. That is, the alcohol has both the function of a carbonylation reactant and a solvent. When the alcohol used in step a) is a polyalcohol, the molar ratio to the hydrocarbon used (hydrocarbon:polyalcohol) is 2 to 20, preferably 3 to 10, more preferably 4 to 8. The number of moles of the polyalcohol added is insufficient compared to the hydrocarbon used.

[0015] The inventive reaction of step a) is carried out in the presence of a homogeneous catalytic system, which preferably comprises at least one metal from 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 promoter.

[0016] The metal of PTE Groups 8-10 is preferably palladium. Palladium is preferably used in the form of a precursor compound, as a palladium compound coordinated by a phosphorus-containing ligand. Examples of palladium compounds that can be used as the precursor compound include palladium chloride [PdCl2], acetylacetonatopalladium(II) [Pd(acac)2], palladium(II)-palladium 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], and (cinnamyl)palladium dichloride [Pd(cinnamyl)Cl2]. Preferably, the compounds [Pd(acac)2] or [Pd(OAc)2] are used. The concentration of palladium metal in step a) is preferably 0.01-0.6 mol%, preferably 0.03-0.3 mol%, more preferably 0.04-0.2 mol%, based on the number of moles of the hydrocarbon used.

[0017] Suitable phosphorus-containing ligands of the catalyst system of the present invention preferably have a bidentate structure. Preferred phosphorus-containing ligands for the catalyst system of the present invention are, for example, benzene-based diphosphine compounds as disclosed in EP 3121184. The ligands can be combined with palladium in a pre-reaction, and the palladium-ligand complex is fed to the reaction zone, or added in situ to the reaction and combined there with palladium. The molar ratio of ligand to metal according to the reaction described in step a) can be 1:1 to 10:1, preferably 2:1 to 6:1, more preferably 3:1 to 5:1.

[0018] The homogeneous catalytic system further comprises an acid, in particular a Bronsted acid or a Lewis acid. The Lewis acid may in particular be a Lewis acid with an LAU value of more than 25, preferably a LAU value of 29. The LAU value is a novel method for measuring the strength of Lewis acids (JR Gaffen et al., Chem, Vol. 5, No. 6, p. 1567-1583). As the Lewis acid, preferably aluminum triflate, aluminum chloride, aluminum hydride, trimethylaluminum, tris(pentafluorophenyl)borane, boron trifluoride, boron trichloride, or a mixture thereof is used. Of the above Lewis acids, preferably aluminum triflate is used. The Lewis acid is added in a molar ratio of Lewis acid to ligand of preferably 1:1 to 20:1, preferably 2:1 to 15:1, more preferably 5:1 to 10:1.

[0019] The Brönsted acids used preferably have an acid strength pKa ≦ 5, more preferably an acid strength pKa ≦ 3. The above acid strength pKa means the pKa measured under standard conditions (25 ° C, 1.01325 bar). The acid strength pKa in the context of the present invention due to polyprotic acids relates to the pKa of the first protolysis step. The Brönsted acids are added in a molar ratio of Brönsted acid to ligand of preferably 1:1 to 15:1, preferably 2:1 to 10:1, more preferably 3:1 to 5:1.

[0020] The Bronsted acid may 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.

[0021] The reaction of the hydrocarbons with olefinic double bonds used in step a), i.e. the carbonylation, is preferably carried out at temperatures between 25 and 140° C., more preferably between 80 and 130° C., particularly preferably between 90 and 120° C. The pressure in step a) can be between 5 and 60 bar, preferably between 10 and 40 bar, more preferably between 15 and 30 bar.

[0022] The reaction of step a) is carried out in a suitable reaction zone. The reaction zone for the reaction comprises at least one reactor, but may comprise two or more reactors. The at least one reactor may in particular be selected from the group consisting of stirred tank reactors, loop reactors, jet loop reactors, bubble column reactors, or combinations thereof. When multiple reactors are used, the reactors may be the same or different.

[0023] The above reaction in step a) gives a liquid product mixture comprising at least the ester formed by the reaction, the homogeneous catalytic system, unconverted alcohol A, and possibly further components such as low boilers, e.g. low boiling by-products such as ethers and / or high boilers and / or unconverted hydrocarbons. The liquid product mixture is then fed to a subsequent membrane separation in step b). The reaction in step a) may also remove off-gases (e.g. the above ethers) from the reaction zone, consisting of at least nitrogen, hydrogen and non-reactive impurities such as low boiling by-products. The accumulation of impurities and low boiling by-products and the reduction in the partial pressure of the reaction gas (CO) over time slows down the reaction.

[0024] In the next step b), the liquid product mixture is fed to a membrane separation, and the homogeneous catalytic system is separated from the liquid product mixture. The membrane material of the invention concentrates the homogeneous catalytic system and the unconverted hydrocarbons and / or unconverted alcohols in the retentate, while the esters formed in step a) are concentrated in the permeate. The permeate containing the esters formed is then sent to the next step c). The retentate containing the concentrated homogeneous catalytic system is then recycled to the reaction zone of step a). The recycling of the retentate allows for the additional removal of inert alkanes, low boiling by-products (e.g. ethers), potential decomposition products of the catalytic system or other impurities introduced by the hydrocarbon stream used, e.g. traces of water or nitrogen, from the purge stream, avoiding their accumulation in the reaction zone. The recycling of the retentate ensures that the catalytic system obtained in the membrane separation in the retentate is returned to the reaction. This allows for the catalyst losses due to deposition or deactivation (as occurs, for example, in the case of distillation) to be minimized, leading to lower process costs. Although catalyst losses usually cannot be completely eliminated, the effect of reducing the losses is that less catalyst needs to be replaced with fresh catalyst feed.

[0025] Membrane separation is based on the semi-permeability of the membrane material, which allows certain substances to pass through but not others. The membrane material used in step b) of the method of the present invention is an OSN membrane material (OSN = organic solvent nanofiltration). The membrane material preferably consists of at least a relatively thin active separation layer (active separation layer) and, optionally, a thicker support on which the separation active layer is arranged. The membrane material of the present invention preferably consists of at least a separation active layer and a support. There may be one or more intermediate layers between the separation active layer and the support. In a preferred embodiment, the membrane material consists only of a separation active layer and a support. The membrane material consisting of at least a separation active layer and a support should be acid-stable so that the membrane material is not damaged by acids present as co-catalysts in the liquid product mixture. The term "acid stable" in the context of the present invention means that the membrane material is stable and not destroyed in the presence of acids in the catalyst system for at least 300 hours, in particular Bronsted acids with pKa≦5, more preferably pKa≦3, or Lewis acids with an LAU value of more than 25, preferably an LAU value of 29.

[0026] The support is in particular a porous structure that is permeable to the permeate that has passed through the separation active layer. The support has a stable function and serves as a support for the separation active layer. The support can in principle consist of any suitable porous material. However, there is a prerequisite that the material is stable to acids and bases. The support can also consist of the same material as the separation active layer.

[0027] The separating active layer of the present invention is preferably made of PAEK (polyaryletherketone) polymer. PAEK has the particular feature that the aryl groups in the repeating units are alternately linked via ether and ketone functionalities. A preferred separating active layer of the present invention is made of PEEK (polyetheretherketone). As separating active layer, preferably PEEK polymers having a degree of sulfonation of less than 20%, particularly preferably PEEK polymers having a degree of sulfonation of less than 10% are used. Corresponding PEEK polymers and their preparation are described in WO 2015 / 110843 or J. Da Silva Burgal et al.; Journal of Membrane Science, vol. 479 (2015) pp. 105-116. Surprisingly, it has been found that the material is particularly stable towards acids, in particular as cocatalysts of homogeneous catalytic systems. Moreover, a particular feature of the PEEK material of the present invention, when used as a separating active layer, is that the produced esters are preferentially able to pass through, while even the alcohols used as reactants are at least partially retained, thereby accumulating in the retentate, so that the subsequent treatment of the residual liquid product mixture can be carried out more economically and for longer periods of time, since fewer alcohols have to be removed compared to known membrane materials.

[0028] The membrane separation in step b) is preferably carried out at a temperature of 25 to 100°C, more preferably 30 to 80°C, particularly preferably 40 to 70°C. The product mixture can be cooled to bring the liquid product mixture to the prevailing temperature preferred for the membrane separation. Cooling can be achieved via active cooling with a coolant and via a heat exchanger, by which the other streams of the process of the invention are heated. Optionally, between the reaction zone in step a) and the membrane separation in step b), there is a further degassing step, in which volatile compounds such as carbon monoxide and / or residual inert impurities that are not removed via off-gassing, such as nitrogen, hydrogen, alkanes and low-boiling by-products (e.g. the above-mentioned ethers), are previously removed from the liquid product mixture. The product mixture can first be depressurized below the partial pressure of dissolved components such as carbon monoxide, degassed and then again elevated in pressure and submitted to the membrane separation.

[0029] The transmembrane pressure (TMP) may be 10-60 bar, preferably 15-55 bar, more preferably 20-50 bar (relative) in step b). Here, the permeate pressure may be up to 15 bar, preferably 3-7 bar, above atmospheric pressure, resulting in a support side pressure based on the TMP. In a preferred embodiment, attention should be paid to the pressure ratio and especially the permeate pressure, which is set depending on the hydrocarbon used, the alcohol used and the temperature present, to avoid evaporation after the membrane, which may make the whole operation unstable. The same basically applies to dissolved components such as carbon monoxide, which may be removed in some cases by the above-mentioned degassing step.

[0030] The economics of a membrane separation process may be substantially determined by the service life of the membrane material used, therefore the service life / stability of the membrane may also be a criterion for selecting an appropriate membrane material. A service life of at least half a year is assumed. This may be particularly relevant for processes such as the present one, where the required membrane surface area increases with the total volume of the process and the product is concentrated in the permeate.

[0031] The permeate from the membrane separation (step b)) is then subjected in step c) to a separation process selected from the group consisting of thermal separation, for example distillation, extraction, crystallization or further membrane separation, in order to separate the ester formed in step a) from the remaining permeate. The separation process is preferably distillation. Suitable process conditions are known to the person skilled in the art.

[0032] The separation steps used in step c), in particular the distillation steps, may separate not only the esters formed from the permeate, but also high boilers, such as high boiling by-products, which may be obtained in the reaction of step a). To remove said high boilers, the process according to the invention may comprise a purification step, i.e. a step of purifying the esters formed by separating them from the high boilers contained in the permeate by thermal separation, extraction, crystallization or membrane separation. Preferably, the esters formed are purified using a thermal separation process, more preferably by further distillation. The process conditions are known to those skilled in the art.

[0033] In a preferred embodiment, the permeate, which contains at least unconverted alcohol and / or unconverted hydrocarbons, is largely liberated in step c) from the esters formed in step a) and, in a preferred embodiment, is subjected to a recycling component separation, in which the unconverted alcohol and / or unconverted hydrocarbons are separated from the remaining permeate, in particular the low boilers contained therein, by thermal separation, extraction, crystallization or membrane separation. The unconverted alcohol and / or unconverted hydrocarbons are preferably separated from the remaining permeate by a thermal separation process, more preferably by further distillation. The process conditions are known to those skilled in the art. The unconverted alcohol and / or unconverted hydrocarbons obtained here can then be recycled to the reaction zone.

[0034] The esters formed by the process of the invention can be transesterified in two further process steps c1) and c2), in which a portion of the ester corresponding to the first alcohol A used in step a) is replaced by a second alcohol B. This transesterification can be carried out after the purification step after step c) described above, by the following steps: c1) transesterifying the ester formed in step a) with a second alcohol B, which is different from the alcohol A used in step a) to obtain in a second reaction zone a second liquid product mixture comprising at least an ester with the second alcohol B, comprising separated first alcohol A and unconverted second alcohol B; c2) separating the ester formed with the second alcohol B from the remaining second liquid product mixture, in particular from the first alcohol A by thermal and / or membrane separation, recycling the separated first alcohol A from step a) to the reaction zone and recycling the unconverted alcohol B to the second reaction zone.

[0035] Step c1) is the step in which the actual transesterification reaction is carried out, i.e. the first alcohol A actually bound in step a) is separated and the second alcohol B is bound, and the ester formed in step a) is reacted in the reaction zone with a second alcohol B different from the first alcohol A. In a particularly preferred embodiment, the second alcohol B used in the transesterification reaction has a higher boiling point than the first alcohol A used in step a). Preferably, the second alcohol B is added in excess in the transesterification reaction to promote the transesterification reaction.

[0036] The second alcohol used in the transesterification reaction in step c1) is preferably a mono- or polyalcohol (2 or more OH groups) having 1 to 50 carbon atoms, more preferably a monoalcohol having 1 to 15 carbon atoms, particularly preferably a mixture of 2 or more monoalcohols and / or polyalcohols having 1 to 10 carbon atoms, with the proviso that the first alcohol A and the second alcohol B used in step a) are not identical. In a preferred embodiment, the polyalcohol is a diol, triol or tetraol, preferably a diol or triol having the above number of carbon atoms. Suitable alcohols for the reaction in step a) are methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butyl alcohol, 3-pentanol, 2-propylheptanol, cyclohexanol, phenol, pentaerythritol, neopentyl glycol, trimethylolpropane, dipentaerythritol or mixtures thereof, preferably ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butyl alcohol, 3-pentanol, 2-propylheptanol.

[0037] The transesterification in step c1) is preferably carried out under acid or base catalysis. As the acid, a Bronsted acid or a Lewis acid can be used.

[0038] Suitable Bronsted acids for the transesterification reaction in step c1) are perchloric acid, sulfuric acid, phosphoric acid, methylphosphonic acid or sulfonic acid, such as methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid (pTSA), 2-hydroxypropane-2-sulfonic acid, 2,4,6-trimethylenebenzenesulfonic acid or dodecylsulfonic acid. The Bronsted acid used is preferably sulfuric acid or sulfonic acid, more preferably sulfuric acid. As metals or compounds thereof, for example, tin powder, tin(II) oxide, tin(II) oxalate, titanic acid esters, such as tetraisopropyl orthotitanate or tetrabutyl orthotitanate, and zirconium esters, such as tetrabutyl zirconate, sodium methoxide and potassium methoxide may be used.

[0039] Suitable Lewis acids for the transesterification in step c1) are titanium(IV) isopropoxide, Bu2SnO, BuSn(O)OH or aluminum triflate. Preferably, titanium(IV) isopropoxide and aluminum triflate are used as Lewis acids.

[0040] Suitable bases for the transesterification in step c1) are alkali metals, alkali alkoxides, acetates or oxides of alkali metals or alkaline earth metals, or alkali metal or alkaline earth metal alcoholates, such as NaEtOH or MgEtOH, alkali metal carbonates, such as K2CO3 or Cs2CO3. However, basic ion exchangers or NaOH can also be used. Preferably, Na or Mg alcoholates, such as NaEtOH or MgEtOH, are used.

[0041] The acid-catalyzed transesterification reaction is preferably carried out at 60 to 220° C., more preferably at 100 to 210° C., particularly preferably at 130 to 200° C. Preferably, the temperature of the reaction is higher than the boiling point of the primary alcohol A to be separated, thereby promoting the direct separation of the primary alcohol A from the reaction mixture and a shift of the equilibrium towards the product. The secondary alcohol B is preferably added to the ester formed in step a), preferably in significant excess, for example 30:1.

[0042] The temperature of the transesterification reaction using a base catalyst is preferably 20 to 100°C.

[0043] The transesterification reaction produces a second liquid product mixture that includes at least the ester with the secondary alcohol B, the separated primary alcohol A, and unconverted secondary alcohol B.

[0044] The second ester formed in step c1) is separated from the remaining second liquid product mixture in a subsequent step c2) by thermal separation, preferably by distillation, and / or by membrane separation, in particular using the above-mentioned membrane materials. Suitable process conditions are known to those skilled in the art.

[0045] The separation step used in step c2), in particular the distillation step, allows the separation of the esters formed and any possible high boilers, such as high boiling by-products that may be formed in step c1), from the remaining second liquid product mixture. The process according to the invention may comprise a purification step, i.e. a step of purifying the esters formed in step c), in which the esters are separated from the high boilers present by thermal separation, extraction, crystallization or membrane separation to remove said high boilers. The esters formed are preferably purified using a thermal separation process, more preferably by further distillation. The process conditions are known to the person skilled in the art.

[0046] After being produced in step a) and separated from the permeate in step c), the optionally purified ester is hydrogenated in step d) using hydrogen in the process to cleave the ester group and recover the desired alcohol, alcohol A linked in the ester formation in step a) or alcohol B linked in the transesterification reaction. Thus, the hydrogenation forms an alcohol mixture containing at least the desired alcohol, alcohol A or B and unconverted ester.

[0047] Without being transesterified, the alcohol A recovered in the hydrogenation of step d) can be separated from the alcohol mixture obtained in the next step and recycled to the first reaction zone. In a subsequent process step in which a transesterification reaction is carried out with recovery of the alcohol B in the hydrogenation of step d), it can be separated from the alcohol mixture formed and recycled to the second reaction zone.

[0048] Typical hydrogenation conditions are known to the person skilled in the art and are disclosed, for example, in EP 1 042 260. The hydrogenation according to the invention in step d) is preferably carried out at a pressure of 10 to 300 bar, more preferably at a pressure of 100 to 280 bar, particularly preferably at a pressure of 150 to 270 bar. The hydrogenation temperature is preferably 100° C. to 300° C., preferably 150° C. to 280° C., particularly preferably 180° C. to 220° C. In the hydrogenation, impurities such as low boiling components, for example nitrogen or low boiling by-products, can be removed by further withdrawing off-gas.

[0049] The hydrogenation in step d) is carried out in the presence of a heterogeneous catalyst system. Conventional catalyst systems are known, for example, from EP 1 338 557 A1. The heterogeneous catalyst system preferably comprises a metal from the group consisting of copper, rhodium, ruthenium, rhenium or compounds of these metals. More preferred are copper-chromium oxide-based catalyst systems. Particularly preferred catalyst systems comprise copper and / or zinc as active components, which are applied to a support material. Suitable support materials are porous silica and / or alumina.

[0050] The hydrogen required for the hydrogenation can be supplied directly as a feedstock, or by previously separating a hydrogen-containing gas into its hydrogen components by methods known to those skilled in the art and conveying the hydrogen to the hydrogenation zone. Since complete separation is almost impossible, the hydrogen will still contain a certain proportion of carbon monoxide and other gases.

[0051] In the next step e), the alcohol mixture from the hydrogenation of step d) is sent to at least one separation process step selected from the group consisting of thermal separation, e.g. distillation, extraction, crystallization or further membrane separation, to separate the target alcohol formed in step d) from the remaining alcohol mixture. The separation process is preferably distillation. Suitable process conditions are known to those skilled in the art. Multi-stage distillation is also possible.

[0052] In at least one separate process step, the alcohols A and B used can be further removed and recycled to the first or second reaction zone, respectively. During recycling, a purge stream can be withdrawn to remove hydrogenation by-products, such as inert alkanes, aldehydes, acetals, ethers, ketones or carbon, from the process.

[0053] For the characterization of the permeability or separation performance of a membrane in membrane technology, the retention force R of a membrane for a specific component of a substance mixture is defined by the following formula (1): R=1-W (I)P / W (I)R (1) Here, W (I)P is the mass fraction of the relevant component in the permeate, and W (I)R is the mass fraction of the relevant component in the membrane retentate. Thus, retention can be a value between 0 and 1 and is therefore preferably stated in %. A retention of 0% means that the component permeates unimpeded through the membrane, so that the mass fraction of the component in the retentate is the same as in the permeate. Conversely, a retention of 100% means that the relevant component is completely retained by the membrane, which is hardly possible industrially.

[0054] In addition to the retention, the so-called permeability of the membrane is decisive for determining this property, according to the following formula (2): P = m' / (A * TMP) (2) Here, m' is the mass flow rate of the permeate, A is the surface area of ​​the membrane, and TMP is the transmembrane pressure. Permeability is usually expressed in units of kg / (h * m 2* It is expressed in units of bar and is a standardized index for the membrane surface and the set TMP.

[0055] Regarding the characterization of the membrane stability, the permeability P Rel The relative change in is defined by the following equation (3): P Rel =P t=x / P t=0 (3) Here, P t=x represents the permeability at time t=x, and P t=0 represents the initial permeability at time t = 0 (the reference time may be different as long as t = x > t = y holds). EXAMPLES

[0056] Conversion of diisobutene (DiB) to methyl 3,5,5-trimethylhexanoate (TMH ester) by membrane separation as catalyst recycle DiB is a mixture of two C8 isomers, 2,4,4-trimethylpent-1-ene and 2,4,4-trimethylpent-2-ene, in a ratio of approximately 80:20. The experiments were carried out in a continuous pilot plant with the following settings:

[0057] The plant essentially consists of a 200 ml Büchi glass autoclave (=reactor) (pressure rated up to 10 bar). The autoclave is fed from a glass vessel filled with the reaction solution and covered with argon by a Knauer HPLC pump. Another Knauer HPLC pump feeds a pump from the glass autoclave to a separate high-pressure circuit, which can be pressurized up to 60 bar. The high-pressure circuit of the pilot plant essentially consists of a liquid circuit and a flat membrane test cell, which are operated by a circulation pump, and the necessary sensors (e.g. pressure measurement, temperature measurement). The high-pressure circuit is circulated by a centrifugal pump, which ensures the necessary overflow of the diaphragm. The liquid flow that has passed through the membrane is removed from the membrane module as permeate and collected in an argon-covered glass receiver. The permeate volume is continuously weighed. The excess feed volume (retentate volume) is returned to the glass autoclave. The recirculation is achieved by a mechanical pre-pressure regulator, which is also used to regulate the pre-pressure of the nanofiltration stage. The circuit is heated by a thermostat to ensure a given temperature for the separation.

[0058] The experiments were carried out under the following conditions: active membrane surface area 84.5 cm 2 , membrane pressure 45 bar, separation temperature 25°C.

[0059] Samples may be taken from the feed to the high pressure circuit (feed), from the high pressure circuit (retentate) and from the permeate. For yield analysis, 0.08 g sample and 0.03 g ethylbenzene (internal standard) were weighed and diluted with 0.25 g acetonitrile. Further analysis was performed using GC-FID. Ligand and metal retention was confirmed by ICP-OES after pre-digestion of permeate and retentate samples. Analysis of acid retention was performed using 19 F NMR was used. For all three methods, sample preparation and analysis are known to those skilled in the art.

[0060] The membrane material used was PEEK. The PEEK-acetone membrane of the present invention is produced by the method described in J. da Silva Burgal et al.; Journal of Membrane Science, Vol. 479 (2015), S. 105-116 (see also WO 2015 / 110843).

[0061] The contents of the glass autoclave were stirred to achieve near perfect mixing. The pressure in the glass autoclave was regulated at 10 bar by a mechanical pre-pressure regulator. The glass autoclave was kept at the desired temperature using an oil bath with an external temperature measuring device attached to the glass autoclave.

[0062] First, a glass autoclave and a high-pressure circuit were filled with a basic reaction mixture consisting of 56% by mass MeOH, 40% by mass DiB, 0.5% by mass 1,2-bis((tert-butyl(pyridin-2-yl)phosphanyl)methyl)benzene (ligand), 3.4% by mass aluminum triflate (acid), and 0.1% by mass [Pd(acac)2] (metal), inerted with 10 bar argon, and operated.

[0063] The glass autoclave was then heated to an internal temperature of 100°C and the initial argon flow rate was changed to CO (reaction start). The system was started by pumping the base reaction mixture in circulation for 15 hours. After 15 hours, the DiB in the feed was converted to TMH esters by 99%. After 15 hours, the circulation mode was terminated, the permeate was collected in another glass vessel, and fresh reaction solution (60% by weight MeOH and 40% by weight DiB) was weighed. No new catalyst, ligand, or acid was added during the 105-hour test period. For each test period, the permeability, yield, and retention of the components of the catalyst system were measured using the methods described above. Table 1. Sequential conversion of DiB to TMH esters

[0064] [Table 1] * Yield at the end of the experimental period under consideration in each case ** No pending confirmation (system initiated) From Table 1, it is clear that the membrane separation allows for over 97% of the metal, ligand and acid to be recycled, meaning that the desired ester yield can be achieved for an extended period of time without the need for further addition of fresh catalyst system. Thus, the activity of the catalyst complex is not significantly affected by the process. EXAMPLES

[0065] Hydrogenation of the TMH ester obtained in Example 1 to the TMH alcohol The permeate recovered in Example 1 was separated by fractional distillation. First, after removing methanol and unconverted diisobutene (DiB), 3,5,5-methyl hexanoate methyl (TMH ester) was obtained. Then, the TMH ester was reacted with a catalyst containing 15 wt.% Cu / 1.8 wt.% Cr on a support (Stuttgarter Masse) at 200 °C and 270 bar H2 for 20 h in a 300 ml autoclave. After cooling and decompression, 1 ml of sample was taken, 150 μl of isooctane was added as an internal standard, and the yield and n / iso selectivity were measured by GC analysis. The yield of TMH alcohol was 98% (n / iso: 99:1). EXAMPLES

[0066] The conversion of diisobutene (DiB) to methyl 3,5,5-trimethylhexanoate (TMH ester) was carried out as described in Example 1 with catalyst-recycle (0.15 L of base reaction mixture: 56% by weight MeOH, 40% by weight DiB, 0.5% by weight 1,2-bis((tert-butyl(pyridin-2-yl)phosphanyl)methyl)benzene (ligand), 3.4% by weight aluminum triflate (acid), and 0.1% by weight [Pd(acac)2] (metal).

[0067] After the start of the reaction, samples were taken every 4 hours. For yield analysis, 0.08 g of sample and 0.03 g of ethylbenzene (internal standard) were weighed and diluted with 0.25 g of acetonitrile. Analysis was performed as described in Example 1. After 4 hours, the reaction was stopped, the reaction mixture was cooled, and the reactor was depressurized.

[0068] A vacuum (0.02 bar) was applied to reduce the reaction volume to 0.02 liters, and mainly methanol, unconverted DiB and TMH ester were condensed and recovered, while the catalyst system remained in the glass autoclave. A sample of the reaction mixture remaining in the reactor was analyzed by GC-FID, which showed traces of methanol and unconverted DiB (<2% by weight).

[0069] The glass autoclave was then filled to 0.15 liters and a second reaction was carried out using a base reaction mixture consisting of 60% by weight MeOH and 40% by weight DiB to carry out further reactions.

[0070] After the start of the reaction, samples were taken every 4 hours. To analyze the yield, 0.08 g of sample and 0.03 g of ethylbenzene (internal standard) were weighed and diluted with 0.25 g of acetonitrile. The analysis was carried out as described in Example 1. After 4 hours, the reaction was stopped, the reaction mixture was cooled, and the reactor was depressurized. Table 2 Comparison of the conversion of DiB to TMH esters after distillation

[0071] [Table 2] Table 2 shows that distillation to remove reactants and products from the catalyst clearly reduces the reactivity of the catalyst in the second run. EXAMPLES

[0072] The formulation used in this example was similar to that of Example 1, except that di-n-butene (DnB) was used.

[0073] The permeate recovered in Example 1 was separated by fractional distillation. First, after removing methanol and unconverted di-n-butene (DnB), the resulting ester, methyl isononanoate, was obtained. The resulting ester was then reacted in a 300 ml Paar autoclave with a 15 wt.% Cu / 1.8 wt.% Cr catalyst supported on a Stuttgarter Masse (closed loop control based on internal temperature) at 500 rpm for 20 h at 270 bar H2. After cooling and depressurization, a 1 ml sample was taken and 150 μl of isooctane was added as an internal standard to determine the yield and n / iso selectivity by GC analysis (yield: 94% isononyl alcohol, (n / iso: 69:31)).

Claims

1. 1. A method for producing a target alcohol, comprising the steps of: a) producing an ester by reacting a C2-C16 hydrocarbon having at least one multiple bond with carbon monoxide and a mono- or polyalcohol (two or more OH groups) having 1 to 50 carbon atoms or a mixture of two or more mono- and / or polyalcohols, an alcohol A, used in a molar ratio of 2 to 20 relative to the C2-C16 hydrocarbon (alcohol:C2-C16 hydrocarbon), in the presence of a homogeneous catalyst system comprising at least one metal or compound thereof from Groups 8 to 10 of the Periodic Table of the Elements, a phosphorus-containing ligand and an acid (carbonylation) to obtain a liquid product mixture in a first reaction zone; b) carrying out a membrane separation step for separating the homogeneous catalytic system from the liquid product mixture, enriching the homogeneous catalytic system in a retentate and further unconverted hydrocarbons and / or the unconverted alcohol A, and enriching the ester in the permeate formed in step a), wherein as membrane material the membrane material used is an OSN-based (Organic Solvent Nanofiltration) membrane material that is stable for at least 300 hours in the presence of the acid of the homogeneous catalytic system and comprises at least one separation active layer, and wherein the retentate is returned to the first reaction zone of step a) and the permeate is sent to step c); c) separating the ester formed in step a) from the permeate in at least one separation step selected from the group consisting of thermal separation, distillation, extraction, crystallization and membrane separation; d) hydrogenating the ester separated in step c) with hydrogen in a hydrogenation zone in the presence of a heterogeneous catalytic system to obtain an alcohol mixture comprising at least the target alcohol, the separated alcohol A and unconverted ester; e) separating the target alcohol formed in step d) by at least one separation step selected from the thermal separation steps of distillation, extraction, crystallization and membrane separation; 1. A method comprising: the alcohol A used in step a) is selected from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butyl alcohol, 3-pentanol, 2-propylheptanol, cyclohexanol, phenol, and mixtures thereof; The C2-C16 hydrocarbon having at least one olefinic double bond used in step a) is an n-alkene or an isoalkene having 2 to 16 carbon atoms; The metal or compound thereof from Groups 8 to 10 of the Periodic Table of the Elements of the homogeneous catalytic system in step a) is palladium or a compound thereof; the acid of the catalytic system in step a) is a Bronsted acid or a Lewis acid, wherein the Bronsted acid is perchloric acid, sulfuric acid, phosphoric acid, methylphosphonic acid or sulfonic acid, and wherein the Lewis acid is aluminum triflat, aluminum chloride, aluminum hydride, trimethylaluminum, tris(pentafluorophenyl)borane, boron trifluoride, boron trichloride or a mixture thereof; method.

2. The method of claim 1 , wherein the separating active layer comprises a PAEK polymer.

3. 3. The method of claim 2, wherein the separating active layer is made of PEEK and has a degree of sulfonation of less than 20%, or less than 10%.

4. The method according to any one of claims 1 to 3, wherein the phosphorus-containing ligand of the homogeneous catalytic system has a bidentate structure.

5. The process according to any one of claims 1 to 4, wherein the reaction of step a) is carried out at a pressure of from 5 to 60 bar.

6. 6. The method according to claim 1, wherein the acid of the catalytic system of step a) is a Bronsted acid with a pKa≦5 or pKa≦3 or a Lewis acid with a LAU value of more than 25.

7. 7. The process according to any one of claims 1 to 6, wherein synthesis gas is separated upstream of the first reaction zone, and separated carbon monoxide is sent to the first reaction zone in step a) and separated hydrogen is sent to a hydrogenation zone in step d).

8. After the separation step of step c), the following steps are further performed: c1) transesterification of the ester formed in step a) with a second alcohol B, which is different from the alcohol used in step a), to obtain in a second reaction zone a second liquid product mixture comprising at least the ester with the second alcohol B, the separated first alcohol A and unconverted second alcohol B, wherein the second alcohol B is used in equimolar or excess; c2) separating the ester formed in step c1) and separating the remaining second liquid product mixture by thermal and / or membrane separation, recycling the separated first alcohol A to the first reaction zone and recycling the unconverted second alcohol B to the second reaction zone; wherein the ester formed in step c1) is used in the hydrogenation in step d). The method according to any one of claims 1 to 7.

9. 9. The method of claim 8, wherein the second alcohol B has a higher boiling point than the first alcohol A.

10. 9. The process of claim 8, wherein the separated portion of the first alcohol A has already been removed from the second reaction zone and is recycled to the first reaction zone.

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