Process for hydroformylating olefins in a homogeneous phase

Abstract

The present invention relates to a process for producing aldehydes by hydroformylation of olefins with synthesis gas over a transition metal complex catalyst, comprising: in a first process step, reacting the olefins with a water-soluble transition metal complex catalyst composed of a metal and a ligand bonded thereto in the presence of a water-miscible solvent, and controlling the pressure, temperature, and the quantitative ratio of the solvent and the aqueous catalyst solution so that the hydroformylation takes place in a homogeneous single-phase reaction solution; and in a second reaction step, converting the homogeneous reaction solution obtained from the first reaction step into a two-phase process solution by reducing the temperature and / or the pressure, and separating at least a portion of the organic phase from the aqueous phase.

Description

[Technical Field]

[0001] The present invention relates to a process for producing aldehydes by hydroformylation of olefins with synthesis gas over a transition metal complex catalyst, comprising: reacting the olefins in a first process step with a water-soluble transition metal complex catalyst consisting of a metal and a ligand bonded thereto in the presence of a water-miscible solvent, and controlling the pressure, temperature, and the quantitative ratio of the solvent and the aqueous catalyst solution so that the hydroformylation takes place in a homogeneous single-phase reaction solution; and converting the homogeneous reaction solution obtained from the first reaction step into a two-phase process solution by reducing the temperature and / or pressure, and separating at least a portion of the organic phase from the aqueous phase. [Background technology]

[0002] Further functionalization of olefins by hydroformylation using synthesis gas in the presence of a metal catalyst has been known for some time. The main conversion products are aldehydes with a higher number of carbon atoms than the starting olefins. These aldehydes can be used as they are or, preferably, can themselves be used as further raw materials for the production of numerous useful secondary products. Important industrial secondary products of hydroformylation are alcohols, such as butanol or 2-ethylhexanol, obtained from these aldehydes, for example, by hydrogenation, which can be obtained from propene as the olefin raw material via the aldehyde intermediate. The final hydroformylation products are used in a variety of ways, such as as solvents, detergents and cleaning agents, lubricants, or as intermediates for the production of plasticizers for plastics.

[0003] While the fundamental relationships for the conversion of olefins to aldehydes are known, large-scale processes still require numerous optimization strategies, as the overall process economics are shaped by the complex interrelationships of reaction conditions, feed conversion, desired selectivity, and catalyst life and recovery. In particular, in this matrix, the catalyst and its effective use are particularly important, since the cost of the metals typically used greatly exceeds the cost of the other reactants.

[0004] With this in mind, many different large scale process options have been developed, and various process designs for these can be found in numerous patent documents.

[0005] WO2004024661A1 (Patent Document 1) discloses a method for catalytically hydroformylating an olefinically unsaturated compound having 3 to 24 carbon atoms, in which an unmodified catalyst having at least one metal of Groups 8 to 10 of the Periodic Table of Elements is used as the catalyst, and the hydroformylation is carried out according to the following formula:

[0006] [ka] [R 1 , R 2 , R 3 , R 4 are the same or different and each represents H, a substituted or unsubstituted aliphatic, alicyclic, aromatic, aliphatic-alicyclic, aliphatic-aromatic, or alicyclic-aromatic hydrocarbon residue having 1 to 27 carbon atoms, n is 0 to 5, X is a divalent, substituted or unsubstituted aliphatic, alicyclic, aromatic, aliphatic-alicyclic, or aliphatic-aromatic hydrocarbon residue having 1 to 27 carbon atoms. in the presence of a cyclic carbonate, the proportion of which is at least 1% by weight of the reaction mixture.

[0007] Yet another patent document, EP1529771A1 (Patent Document 2), discloses that dicyclopentadiene is hydroformylated in a heterogeneous reaction system using an aqueous solution to give 8(9)-formyl-tricyclo[5.2.1.0]. 2.6 A method for producing dec-3-ene is disclosed, in which a transition metal compound of Group VIII of the Periodic Table containing a water-soluble organophosphorus(III) compound in a complex bond state is converted with synthesis gas at a temperature of 70-150°C and a pressure of 0.5-10 MPa, in which special sulfonated triarylphosphines are used as the water-soluble organophosphorus(III) compound.

[0008] Yet another possibility for the conversion of cyclic compounds having multiple double bonds is disclosed in DE 102006004318 A1 (Patent Document 3), which discloses a process for the preparation of 3(4),7(8)-dihydroxymethyl-bicyclo[4.3.0]nonane by hydroformylation and subsequent hydrogenation of bicyclo[4.3.0]nona-3,7-diene, in which bicyclo[4.3.0]nona-3,7-diene is reacted with synthesis gas in a homogeneous organic phase in the presence of a transition metal compound of Group VIII of the Periodic Table, containing an organophosphorus compound in a complexed state, and an excess of the organophosphorus compound, at temperatures of 70 to 160 °C and pressures of 5 to 35 MPa, and the 3(4),7(8)-bisformyl-bicyclo[4.3.0]nonane thus obtained is then hydrogenated to give 3(4),7(8)-dihydroxymethyl-bicyclo[4.3.0]nonane.

[0009] Such solutions known from the prior art may still leave room for improvement, in particular with regard to the possible efficiency of the conversion, the simplicity of separating the reaction mixture as well as the reusability of the catalyst materials used. Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to at least partially overcome the drawbacks known from the prior art, in particular to provide a process which allows for the efficient conversion of even difficult-to-hydroformylate olefins, and which also allows for a simple and efficient separation of the reaction solution with improved reusability of the catalyst. [Means for solving the problem]

[0011] The solution to this problem is achieved by the features of the independent claims of the method invention. Preferred embodiments of the invention are set out in the subclaims, the description or the drawings, whereby further features set out or shown in the subclaims or the description or the drawings may, alone or in any combination, constitute the subject matter of the invention, unless the context clearly indicates otherwise.

[0012] According to the present invention, the above-mentioned object is achieved by a process for producing aldehydes by hydroformylation of olefins with synthesis gas over a transition metal complex catalyst, comprising: in a first process step, reacting the olefins with a water-soluble transition metal complex catalyst composed of a metal and a ligand bonded thereto in the presence of a water-miscible solvent, and controlling the pressure, temperature, and the quantitative ratio of the solvent and the aqueous catalyst solution so that the hydroformylation takes place in a homogeneous single-phase reaction solution; and in a second reaction step, converting the homogeneous reaction solution obtained from the first reaction step into a two-phase process solution by reducing the temperature and / or pressure, and separating at least a part of the organic phase from the aqueous phase.

[0013] Surprisingly, it has been found that the process of the present invention allows for the conversion of many different olefins to the corresponding aldehydes with high selectivity in a controlled, monophasic reaction environment containing an aqueous catalyst component, with high conversion rates being achieved within short process times, even when using difficult-to-convert olefin feedstocks containing one or more double bonds and / or one or more ring structures. In addition to the highly efficient conversion within the reaction environment, the controlled composition of the reaction environment also significantly simplifies the workup of the reaction solution after the reaction is complete. This offers the advantage of simple and thermally gentle separation of the desired organic product and the catalyst solution, which allows for easy workup and reuse of cost-intensive catalysts without significant loss of reactivity and materials. Without being bound by theory, the monophasic reaction environment under given reaction conditions appears to protect the catalyst, or more specifically, the organic ligands of the catalyst complex, from premature decomposition. Furthermore, the controlled transition of the reaction solution to a two-phase system consisting of an organic product phase and an aqueous catalyst phase in the second process step appears to prevent significant loss of the catalyst system during the workup process, resulting in higher recoverable amounts and higher catalyst activity compared to other catalyst workup methods. This is particularly true when compared to conversion in a purely organic phase, where recovery of the water-insoluble catalyst is difficult. The water-soluble catalyst is separated after conversion by mechanically separating the aqueous catalyst phase from the organic product phase. Therefore, the water-soluble catalyst system is not subjected to a heat load, unlike separation by distillation during conversion in a purely organic phase. High and sustained heat load on the catalyst often leads to its deactivation. In this regard, the coupling of both process steps according to the present invention provides a synergistic effect that promotes highly efficient and catalyst-protective conversion in a large-scale environment.

[0014] The process of the present invention is a method for producing aldehydes by hydroformylation of olefins using synthesis gas over a transition metal complex catalyst. The starting material can be an olefin or a mixture of olefins having 4 to 24 carbon atoms, preferably 6 to 20 carbon atoms, and particularly preferably 8 to 20 carbon atoms. The mixture can contain olefins with one or more terminal and / or internal C-C double bonds. The mixture can contain or consist of olefins with the same, similar (±2) or significantly different (>±2) carbon atom numbers (C numbers). The olefins can be linear, branched, or cyclic. The olefins can be aliphatic olefins with no cyclic structure or one or more cyclic structures. For example, the olefins can have one, two, three, or more rings in the molecule, and the double bond can be present in or on the cyclic structure. Typically, these olefins are only incompletely converted by conventional hydroformylation processes. These olefins are reacted with synthesis gas, i.e., hydrogen and carbon monoxide, to produce aldehydes (HC=O), and the carbon number of the olefin increases by one through this reaction.

[0015] In the hydroformylation step of the first process step, a synthesis gas consisting of carbon monoxide and hydrogen is preferably used, with the molar ratio of carbon monoxide to hydrogen being preferably 1:4 to 4:1, particularly preferably 1:2 to 2:1, and especially preferably 1:1.2 to 1.2:1. In particular, a synthesis gas in which carbon monoxide and hydrogen are present in an approximately stoichiometric ratio can be used.

[0016] In the first process step, olefins are converted using a water-soluble transition metal complex catalyst composed of a metal and a ligand bound thereto. Usable hydroformylation catalysts include a metal and one or more ligands coordinated to the metal. The catalyst can be added to the reaction environment in its preformed state, or an active catalyst can be formed in situ in the reaction zone under reaction conditions from other metal sources, such as metal salts. The latter can be achieved, for example, by the addition or exchange of ligands present in the reaction zone, such as CO, hydrogen, or organic complexing ligands. Preferably, the transition metal complex catalyst is a metal from subgroups 8 to 10 of the periodic table, particularly Co, Ru, Rh, Pd, Pt, Os, or Ir, and more particularly Rh, Co, Ir, or Ru. The water solubility of the catalyst complex is essentially determined simultaneously through the selection of the ligand; a catalyst is water-soluble in the present invention if its solubility in water at 20° C. is 100 g / L or more. Solubility can be determined, for example, according to the OECD method (OECD Guidelines for the Testing of Chemicals, "Water Solubility", edition of July 27, 1995). The ligand can be an inorganic counterion, such as a halogen, or a more complex organic molecule, such as acetate or an aromatic complex ligand with one or more heteroatoms.

[0017] In the first process step, the feedstock is reacted in the presence of a water-miscible solvent. The hydroformylation of olefins to aldehydes via the addition of synthesis gas is carried out in the presence of a solvent other than water. Preferably, the solvent is a fluid that has at least some solubility in water. The solubility of the solvent in water can be, for example, 20 g / L or more at 20°C. Suitable solvents within this group can be, for example, lower monoalcohols or diols. The solvent is preferably also completely miscible with water. The use of a solvent with this solubility ratio to water can contribute to the formation of a particularly solid single-phase region, which can reliably compensate for any pressure and / or temperature fluctuations that may occur. Additionally, the use of this class of solvents can contribute to the fact that large changes in composition can be offset by the formation of products. Furthermore, the proportion of solvent can be kept sufficiently low, which facilitates the separation of the resulting mixture and reduces the energy costs for the separation.

[0018] In the first process step, the pressure, temperature, and quantitative ratios of the solvent and aqueous catalyst solution are controlled so that the hydroformylation occurs in a homogeneous, single-phase reaction solution. The presence of the aqueous catalyst solution, the water-insoluble olefinic feedstock, and the poorly water-soluble aldehyde product forms a biphasic solution in the reaction zone under the reaction conditions, without further measures, which is counter to efficient feedstock conversion. By adding additional solvent, either a single-phase or a two-phase range can exist in the phase diagram under the reaction conditions, depending on the amount of aqueous catalyst, the amount of solvent, the amount of feedstock, or the amount of product / intermediate product. The transition between the single-phase and two-phase ranges can be controlled, particularly through the use of aqueous catalyst and solvent amounts, so that the reaction always proceeds in the single-phase range under given pressure and temperature conditions. By using the appropriate quantitative ratio of the aqueous catalyst solution and solvent, combined with the appropriate solubility or miscibility of the solvent with water, the reaction can proceed in the single-phase range even if the proportions of intermediate and final products change or increase. This control can be achieved, for example, by presetting the required quantitative ratio of solvent and aqueous catalyst solution at the start of the reaction. However, it is also possible to adapt the amounts of one or the other components during the course of the reaction so that the reaction always proceeds in the single-phase region of the phase diagram. The latter approach can be achieved, for example, by controlled addition of solvent in the reaction zone, which is adapted, for example, to the amount of product formed. The phase ranges of the principle single-phase or two-phase systems in the phase diagram can be found in the literature, calculated (see Figure 1), or determined with considerable effort by orientation experiments using varying compositions of selected aqueous catalyst, solvent, and raw materials / products under the reaction conditions.

[0019] In the second process step, the homogeneous reaction solution obtained from the first reaction step is converted into a two-phase process solution by reducing the temperature and / or pressure, and at least a portion of the organic phase is separated from the aqueous phase. From the possible amounts of single-phase compositions consisting of the aqueous catalyst solution, solvent, and olefinic feedstock / product under selected reaction conditions, simple orientation tests can be used to determine the possible fractions of compositions that undergo a change in the phase diagram due to a change in temperature and / or pressure. These compositions are suitable and capable of transitioning to a two-phase state after conversion is complete by a simple change in reaction conditions, and thus resulting in a simple separation between the organic and aqueous phases. This fraction of the single-phase region is usually near the phase boundary between the single-phase and two-phase ranges, and phase separation as a function of pressure and / or temperature conditions can be tracked, for example, visually. Separation of the two phases can be achieved, for example, by a purely mechanical step, such as decantation. However, the two phases can also be separated from each other via a purely thermal, rather than mechanical, separation method. The biphasic nature of the reaction solution also makes the thermal separation operation easier and more resource-efficient. Of course, for workup purposes, the mechanical separation operation can also be combined with the thermal separation operation, in which case the heat load on the catalyst system is lower due to the low boiling point of the solvent selected in the process of the present invention.

[0020] In one preferred embodiment of the method, the temperature and pressure during the conversion can be maintained constant, and the monophasic nature of the reaction solution can be adjusted via the mass ratio of the solvent to the aqueous catalyst solution. Additionally, for efficient process operation, it has been found advantageous to essentially adjust the phase range of the desired single-phase system during the reaction via the mass ratio between the aqueous catalyst solution and the solvent. In this case, a "certain" phase range can be adjusted, thereby reliably offsetting composition changes during the reaction due to the formation of intermediate and / or final products and higher molecular weight by-products. Additionally, by selecting an appropriate solvent and its amount relative to the aqueous catalyst solution, possible temperature and / or pressure fluctuations during the reaction can also be offset. Through this determination, the reaction can be reliably maintained in the single-phase range overall. More preferably, this control can be established through the selection of the amounts of solvent and aqueous catalyst solution at the start of the reaction.

[0021] In a preferred embodiment of the method, the first process step can be carried out at a pressure of 0.5 MPa to 10 MPa and a temperature of 70°C to 150°C. Due to the enhanced reactivity with synthesis gas achieved by operating in the single-phase range, the aforementioned temperature range has proven particularly advantageous. This range provides particularly rapid and selective conversions, with a particularly low proportion of high boilers produced. In addition, the catalyst life is significantly increased, likely due to reduced ligand decomposition in the reaction solution. Furthermore, surprisingly, it has been found that within this temperature range, particularly low pressures are sufficient for the conversion of difficult feedstocks. This is particularly true for double conversions involving sterically challenging feedstocks or diolefin feedstocks. In such conversions, the aqueous components in the single-phase region do not appear to impede the inflow of synthesis gas, and as a result, sufficient gas introduction into the reaction solution can be ensured even at relatively low pressures overall.

[0022] In yet another preferred aspect of the process, the olefin can have at least two non-conjugated double bonds. The process according to the present invention is particularly suitable for converting difficult feedstocks, for example, which may have two or more isolated double bonds. It has been found that the conversion of two double bonds is also possible in a single-phase reaction. This is surprising, since reactions carried out in a two-phase system usually only allow the conversion of one double bond. In addition, the conversion can be carried out faster, more selectively, and with less high-boiling by-products than in a two-phase system. The double bonds of the diene can be present in the aliphatic chain and / or ring. Preferably, short- or medium-chain aliphatic diolefins or higher olefins can be converted. For example, olefins with two or more unsaturated bonds having a molecular weight of 50 g / mol or more and 500 g / mol or less can be converted.

[0023] Within the scope of a preferred feature of the process, the olefin may have at least one aliphatic ring. Additionally, within the scope of the single-phase process of the present invention, sterically difficult olefin feedstocks with rigid aliphatic ring structures can also be converted. These olefins are typically significantly less reactive in catalyst solutions than short-chain aliphatic olefins, or, in the case of multiple double bonds, terminate at an intermediate product stage. The feedstock can be monocyclic or polycyclic. Single-phase conversions in purely organic solvents and in purely organic phases are certainly possible, but present greater challenges in purifying the resulting products. Furthermore, the latter conversions present problems with catalyst recovery and their service life. For example, in purely organic solvents, unmodified (without ligand conversion) metal catalysts are also used for the conversion of diolefins described herein, but they require large amounts of catalyst and are not recycled. When ligand-metal complexes are used as catalysts, the desired activity is often not achieved in the hydroformylation of polycyclic diolefins. The monocyclic, bicyclic, or tricyclic olefins contain two or three closed non-aromatic rings and, further, preferably have a molecular weight of at least 60 g / mol and at most 450 g / mol.

[0024] In yet another preferred embodiment of the method, the molar ratio of water to catalyst metal in the aqueous catalyst solution used, expressed as moles of water divided by moles of catalyst metal, can be greater than or equal to 5,000 and less than or equal to 60,000. This water-to-catalyst ratio has been found to be particularly advantageous, despite the fact that the accessibility of the organic feedstock to the catalyst is improved by the organic environment. This water ratio ensures complete conversion of the diene feedstock to dialdehyde and allows the process to be designed to be single-phase. Additionally, fluctuations in reaction conditions can be reliably offset without departing from the single-phase region. This water-to-catalyst metal ratio also appears to be suitable for ensuring a reliable and complete separation of the aqueous catalyst phase in the second process step. This water ratio adequately protects both the catalyst and its ligands during the single-phase conversion. Furthermore, a sufficiently aqueous environment can be maintained even after changing reaction conditions and decomposing the single-phase system into a two-phase system, which promotes the reusability of the catalyst solution.

[0025] In yet another preferred embodiment of the process, the metal of the water-soluble transition metal complex catalyst can be rhodium, and the ligand can include a water-soluble diphosphine or triarylphosphine. The catalyst used or the resulting catalyst system in the reaction solution contains the transition metal rhodium. This metal allows for exceptionally fast reaction rates in single-phase solutions and can convert even sterically difficult polyenes or olefins with rigid ring structures. In addition to the metal, the catalyst contains at least one diphosphine ligand containing two phosphorus atoms or one or more organic triarylphosphine ligands containing one phosphorus atom in its coordination sphere or coordinates these in the reaction solution under reaction conditions. The catalytically active system is further formed under reaction conditions by the further access of hydrogen and carbon monoxide in the reaction vessel, with synthesis gas components forming coordination complexes with the metal. However, it is also possible to first preform the catalyst and then feed it to the actual hydroformylation step. In this case, the preformation conditions generally correspond to the hydroformylation conditions.

[0026] The triarylphosphines can correspond, for example, to the following general formula:

[0027] [ka] In the formula, Ar1, Ar2 and Ar3 represent the same or different aryl groups having 6 to 14 carbon atoms. The substituents Y1, Y2 and Y3 represent the same or different linear or branched alkyl or alkoxy residues having 1 to 4 carbon atoms, chlorine, bromine, hydroxyl, cyanide or nitro groups, and further represent groups of the formula NR 1 R 2 represents an amino group represented by the formula: 1 and R 2 may be the same or different and represent hydrogen or a linear or branched alkyl group having 1 to 4 carbon atoms. The counter cation M may represent lithium, sodium, potassium, magnesium, calcium, or barium, where m1, m2, and m3 may be the same or different and represent integers of 0 to 5, and n1, n2, and n3 may be the same or different and represent integers of 0 to 3, with at least one of the numbers n1, n2, and n3 being 1 or greater. When the solubility of the complex in water at 20°C is 100 g / L or greater, the triarylphosphine-complex catalyst is a water-soluble triarylphosphine complex catalyst.

[0028] Water-soluble triarylphosphines of the formula described above preferably include those in which Ar1, Ar2, and Ar3 are phenyl groups; and Y1, Y2, and Y3 are methyl, ethyl, methoxy, ethoxy, and / or chlorine atoms. The cationic residue M of the inorganic cation can preferably be sodium, potassium, calcium, or barium. Particularly suitable are water-soluble triarylphosphines in which Ar1, Ar2, and Ar3 are each phenyl groups; m1, m2, and m3 are 0; n1, n2, and n3 are 0 or 1; and n1 + n2 + n3 totals 1 to 3, with the sulfonate group preferably in the meta position. The ligands can be used alone or in mixtures. Suitable examples of water-soluble triarylphosphine ligands include (sulfophenyl)diphenylphosphine, di(sulfophenyl)phenylphosphine, and tri(sulfophenylphosphine). In the prior art, (sulfophenyl)diphenylphosphine is abbreviated as TPPMS, di(sulfophenyl)phenylphosphine as TPPDS, and tri(sulfophenyl)phosphine as TPPTS. These ligands may contribute to the sufficient water solubility of the catalyst complex and are stable in both the single-phase and two-phase regimes.

[0029] Likewise suitable as water-soluble diphosphines are the sulfonated diphosphines of the following general formulae (III) and (IV):

[0030] [ka] In (III), n4 and n5 each independently represent 0 or 1, and the compound of formula (III) can contain up to six -SO3M groups.

[0031] In (IV), n6, n7, n8 and n9 each independently represent 0 or 1, and the compound of formula (IV) contains four to eight -SO3M groups.

[0032] In formulas (III) and (IV), M represents ammonium, a monovalent metal or a polyvalent metal equivalent, particularly sodium, potassium, calcium or barium.

[0033] In one preferred embodiment of the method, the mass ratio of the aqueous catalyst solution to the solvent, expressed as the mass of the catalyst solution divided by the mass of the solvent, can be 0.25 or more and 4 or less. This mass ratio has been found to be particularly reliable and advantageous for single-phase reaction solutions. This mass ratio can reliably compensate for inevitable fluctuations in pressure and temperature caused by the process, as well as changes in composition due to product formation. Furthermore, advantageously, the amount of solvent added can be relatively small, 0.5 or more and 2 or less, particularly preferably 0.75 or more and 1.5 or less, based on the mass of the catalyst solution. This small amount of solvent added can contribute to more efficient workup of the reaction solution after the reaction is complete.

[0034] In yet another preferred aspect of the method, the water-miscible solvent can have a solubility of 20 g / L or more in water at 20°C. That is, it has been found that a solvent having a water miscibility within the above range is particularly suitable for obtaining a single-phase range that is as stable as possible with as little solvent added as possible. Such a single-phase reaction solution can be stable against changes in the reaction environment due to the addition of products and against possible changes in the reaction parameters of pressure and temperature, and can also cause particularly advantageous phase separation of the organic and aqueous phases after the reaction is completed. In particular, this group of solvents can increase the proportion of catalyst that can be recovered after the reaction is completed. In yet another preferred embodiment, the solubility of the solvent can be 60 g / L or more, more preferably 70 g / L or more, and even more preferably 80 g / L or more at 20°C. In yet another preferred embodiment, the solvent can be completely miscible with water at 20°C.

[0035] In one preferred feature of the process, the solvent can be selected from the group consisting of linear or branched C2-C5 alcohols or a mixture of at least two alcohols from this group. It has been found that short-chain alcohols are particularly suitable for achieving particularly efficient conversions in the single-phase region. By using these solvents, even difficult-to-hydroformylate feedstocks can be converted very selectively over water-soluble catalysts within very short process times. The catalyst's life can also be significantly extended by this solvent selection. These solvents exhibit a lower binding affinity for the metal compared to the ligand. However, at the same time, they can act to stabilize the ligand and therefore protect it from decomposition. Another advantage is that a very robust single-phase region can be achieved with only a small mass proportion of solvent, which reduces the costs of workup and separation of the desired product. Additionally, the choice of solvent can contribute to a very rapid and complete transition from one phase to two phases in the second process step, allowing a large portion of the catalyst to be recovered and, if necessary, recycled back into the reaction cycle. Additionally, a low boiling point of the selected solvent is advantageous, allowing the solvent to be easily separated from the product or from the catalyst system, if desired.

[0036] In yet another preferred aspect of the process, the solvent can be isopropanol. The use of isopropanol for the single-phase conversion of olefins in the context of hydroformylation has proven particularly advantageous. By adding isopropanol, even olefin feedstocks that are difficult to hydroformylate can be converted highly selectively over a water-soluble catalyst within a very short process time. The solvent also significantly extends the catalyst's life. A further advantage is that even with only a small proportion of isopropanol, a very solid single-phase region is formed, which reduces the costs of workup and separation of the desired product. In addition, the physical difference between isopropanol and the aldehyde product allows for particularly simple and complete separation after the reaction is complete. This can particularly increase the reusability of the catalyst.

[0037] In yet another preferred embodiment of the process, at least one ligand of the water-soluble transition metal complex catalyst can comprise triphenylphosphine-3,3',3"-trisulfonic acid sodium salt. The use of these triphenylphosphine ligands has proven particularly advantageous for operation in the single-phase range. In addition to a highly selective conversion of the olefins used, particularly low amounts of high boilers are formed, even over long reaction periods. This is particularly the case when isopropanol is used as the solvent, in which case decomposition of the organic ligands is particularly low. In addition, catalyst complexes having these ligands can be particularly efficiently recycled from the reaction mixture, for example, by returning them to the reaction cycle in a continuous reaction. In addition, decomposition of these ligands appears to be particularly low in a single-phase reaction environment. In yet another preferred embodiment, triphenylphosphine-3,3',3"-trisulfonic acid sodium salt can be the only aromatic complex ligand in the conversion.

[0038] In yet another preferred embodiment of the method, the water-soluble transition metal complex catalyst can comprise a triarylphosphine ligand and a catalytic metal, wherein the molar ratio of the triarylphosphine ligand to the catalytic metal, expressed as the number of moles of triarylphosphine ligand divided by the number of moles of catalytic metal, is greater than or equal to 3 and less than 15. It has been found that maintaining a narrow range of the organic ligand to catalytic metal ratio is advantageous for monolayer conversion. Within this ratio, conversion is highly reproducible and highly selective. This is likely possible because the relatively low ligand concentration allows for higher catalyst activity. At the same time, decomposition of the organic ligand in the monolayer solution can be delayed or even completely prevented. This approach can therefore contribute to more frequent and longer catalyst use. In addition, this ratio strongly contributes to protecting the catalyst during workup, thereby improving the recoverability of the catalyst after separation of the reaction products. More preferably, the ratio is 5 or more and 12 or less, and particularly preferably 7 or more and 10 or less.

[0039] In yet another preferred embodiment of the method, the molar ratio of catalyst metal to olefin, expressed as moles of catalyst metal divided by moles of olefin, can be 0.05% or more and 0.75% or less. The single-phase process allows for very efficient use of particularly low ratios of catalyst to olefin feedstock. Complete conversion to dialdehyde is achieved within a short reaction time, and catalyst life can be longer than with prior art approaches. The ratio can more preferably be 0.15% or more and 0.65% or less, and particularly preferably 0.3% or more and 0.5% or less.

[0040] In a preferred embodiment of the method, in the second process step, the homogeneous reaction solution obtained from the first reaction step can be converted into a two-phase process solution by lowering the temperature, and the product aldehyde can be separated. In the second process step of the method according to the invention, after the conversion of the olefin to the aldehyde, the reaction pressure and / or the reaction temperature can be lowered. Thus, the homogeneous reaction solution obtained in the first reaction step is forced to separate into two phases. One phase contains the aqueous catalyst, while the second phase contains the product aldehyde. Separation of the two phases primarily via temperature allows for gentle mechanical separation of the product from the catalyst. For this purpose, a significant change in pressure is only made after the temperature has been changed by at least 50°C from the temperature of the reaction zone. A significant change in reaction pressure occurs when the reaction pressure deviates by at least 10%. It is particularly advantageous that a purely thermal separation in the form of distillation, which would primarily produce high boilers and potentially deactivate the catalyst system, is not performed. This is a method that is carried out under mild conditions.

[0041] In yet another embodiment of the method, the pH value of the aqueous catalyst solution can be greater than or equal to pH 4 and less than or equal to pH 10. It has been found that by adjusting the pH value to the above-mentioned preferred range, a catalyst composed of a transition metal and a water-soluble organophosphorus ligand exhibits very high activity and high selectivity with respect to product formation. This adjustment can be carried out by adding known adjusters, such as inorganic acids or bases, to the used catalyst solution. However, it is also possible and advantageous to maintain the homogeneous phase formed with the used aqueous catalyst solution within the above-mentioned pH range. Furthermore, it has been observed that the above-mentioned preferred pH value adjustment results in less catalyst decomposition. In yet another preferred embodiment, the pH value can be adjusted between greater than or equal to pH 5 and less than or equal to pH 8, more preferably between greater than or equal to pH 5.5 and less than or equal to pH 7.

[0042] In one preferred embodiment of the process, the olefin used can be a polycyclic aliphatic diolefin selected from the group consisting of bicyclic or tricyclic dienes or mixtures thereof. It has been found particularly advantageous in the practice of the process according to the invention to convert sterically difficult cyclic diene feedstocks containing internal double bonds, which, due to their rigid ring structure, are significantly less reactive in solutions containing the catalyst complex than, for example, short aliphatic chains. These polycyclic olefinic aliphatics can only be converted very incompletely in conventional processes in the two-phase region. While single-phase conversion in purely organic solvents is certainly possible, purification of the resulting product presents significant problems. Furthermore, the latter conversion presents problems with catalyst recovery and its lifetime. For example, in purely organic solvents, unmodified (without ligand conversion) metal catalysts are also used for the diolefin conversions described herein, but this requires high catalyst loadings and the catalyst is not recycled. When ligand-metal complexes are used as catalysts, the desired activity is often not achieved in the hydroformylation of polycyclic diolefins. The bicyclic or tricyclic dienes convertible according to the present invention contain two or three closed non-aromatic rings and, furthermore, preferably have a molecular weight of at least 60 g / mol and at most 450 g / mol.

[0043] In yet another preferred embodiment of the method, the olefin can be a cycloaliphatic diolefin selected from the group consisting of dicyclopentadiene and norbornadiene. The conversion method of the present invention can effectively convert particularly sterically difficult and poorly water-soluble polycyclic aliphatic olefins, such as tricyclo[5.2.1.02,6]deca-3,8-diene and bicyclo[2.2.1]hepta-2,5-diene. High conversion rates are achieved with high selectivity, and the catalyst system can also have a particularly long life and improved recoverability. [Example]

[0044] In the hydroformylation according to the present invention, dicyclopentadiene DCDP is converted to the corresponding dialdehyde in a homogeneous reaction solution using an organically modified rhodium complex catalyst according to the following reaction scheme:

[0045] [ka] The catalyst used is a water-soluble complex catalyst containing a phosphorus organic TPPTS ligand of the formula:

[0046] [ka] Isopropanol is used as the solvent to achieve a monophasic reaction system. The conversion is carried out in a stirred reactor (800 rpm) at 130 °C and a pressure of 5 MPa within a reaction time of 3 hours.

[0047] The amounts of raw materials used are as follows:

[0048] [Table 1]

[0049] An aqueous catalyst solution was prepared from rhodium and the ligand. Rh(OAc)2 was used as the rhodium source. This solution was added to the reactor together with the above amount of isopropanol. Dicyclopentadiene was metered in and the reaction was carried out for 3 hours at 5 MPa synthesis gas pressure and 130°C. After cooling and releasing the pressure in the autoclave, isopropanol was removed from the reaction mixture at 100 mbar and 40°C. The residue was then added to a phase separator, which allowed the separation of the catalyst and product phases. The product phase was examined by GC. The following composition (determined by GC) was obtained:

[0050] [Table 2]

[0051] The above results were obtained without considering the solvent ratio. The results show that nearly 100% conversion was achieved using a very low catalyst concentration of 0.45 mol% based on diolefin. In addition, about 90% TCD dial selectivity was obtained.

[0052] The conversion of DCPD to TCD was repeated by adding isopropanol in the monophasic range of the reaction solution. The test conditions were as follows: -30g of DCPD per test - 350 ppm Rh(OAc)2 based on a total mass of 300 g - P / Rh ratio = 10 / 1, equivalent to 18.38g of TPPTS in 135g of water -135g isopropanol Reaction temperature: 130°C -Reaction pressure: 50bar -Reaction time: 3 hours

[0053] The conversion and selectivity of each conversion correspond, within the error range, to the results given above. After the reaction was completed, isopropanol was removed from the reaction solution via a rotary evaporator at 100 mbar and 40°C, and the residue was weighed. The remaining residue was then transferred to a phase separator, and phase separation was carried out at room temperature. The organic phase consisting of the reaction product was removed, weighed, and sampled for rhodium content and product ratio. The upper aqueous catalyst phase was similarly discharged, weighed, and recombined with the previously removed isopropanol. Fresh DCPD was added to this combined catalyst phase, and the mixture was reacted again in the reactor at 130°C and 50 bar synthesis gas pressure for 3 hours. This process was repeated five times.

[0054] The weights of the individual organic phases and their compositions, especially those of TCD dial and TCD monoenal, are constant over the five tests. The proportion of rhodium in the organic phase is also constant and low. The proportion of rhodium in the organic phase is about 3.2 ppm±0.8 ppm% per test, based on the total rhodium used. Therefore, it can be shown that polycyclic diolefins that are difficult to hydroformylate can also be successfully converted, and that the method of the present invention allows for very efficient and simple recovery and reuse of the catalyst. [Brief explanation of the drawings]

[0055] Figure 1 shows the calculated phase behavior of the ternary mixture as a function of composition at a temperature of 120°C. The components include an aqueous solution of the Rh-TPPTS complex catalyst (lower left), isopropanol as the solvent (upper), and TCD-dial as the final product (lower right). The shaded area contains the mass fraction of the ternary composition present in a two-phase system at this temperature. The upper unshaded triangular area represents compositions that are single-phase under the pressure and temperature conditions. Because the solubility of the olefin feedstock is not significantly different from that of the intermediate and final products, this phase diagram is representative of the entire conversion as the feedstock / product ratio varies.

[0056] Further tests were carried out using other solvents and raw materials. The test conditions for these tests were as follows:

[0057] [Table 3]

[0058] The only difference from the previously described reaction conditions was the use of n-propanol instead of isopropanol. Without optimizing the test conditions for the use of n-propanol, a TCD-dial product rate of 61.3% and an olefin conversion of 99.9% were obtained for the conversion of dicyclopentadiene. This indicates that this reaction can also be carried out in unbranched alcohols as solvents.

[0059] This reaction was repeated under the same process conditions as above, except that an additional 20 g of methylcyclohexane (MCH) was added as the solvent. Without optimizing the test conditions for this solvent mixture, a TCD-dial product rate of 69.15% and an olefin conversion of 99.5% were obtained, demonstrating that this reaction can also be carried out with a solvent mixture.

[0060] This reaction was repeated under the same process conditions as above. The difference from the previous reaction was that instead of dicyclopentadiene, 1-octene was used as the olefin component. Without optimizing the test conditions for the use of other olefins, a yield of 83.6% of the C9-aldehyde target component and a 98% olefin conversion were obtained. This indicates that this reaction can also be carried out using acyclic monoolefins.

Claims

1. 1. A process for producing aldehydes by hydroformylating olefins using synthesis gas over a transition metal complex catalyst, comprising: - in a first process step, reacting the olefin with a water-soluble transition metal complex catalyst composed of a metal and a ligand bonded thereto in the presence of a water-miscible solvent, wherein the pressure, temperature, and the ratio of the amount of the solvent and the amount of the aqueous catalyst solution are controlled so that the hydroformylation takes place in a homogeneous single-phase reaction solution; and - in a second process step, by reducing the temperature and / or the pressure, the homogeneous reaction solution obtained from the first reaction step is transformed into a two-phase process solution and at least a portion of the organic phase is separated from the aqueous phase; The method.

2. 10. The process of claim 1, wherein the temperature and pressure are maintained constant during the conversion, and the monophasic nature of the reaction solution is controlled via the mass ratio of solvent to aqueous catalyst solution.

3. 3. The method according to claim 1 or 2, wherein the first process step is carried out at a pressure of ≧0.5 MPa and ≦10 MPa and at a temperature of ≧70° C. and ≦150° C.

4. 4. The method according to claim 1, wherein the olefin has at least two non-conjugated double bonds.

5. 5. The method according to claim 1, wherein the olefin has at least one aliphatic ring.

6. 6. The process according to claim 1, wherein the molar ratio of water in the aqueous catalytic solution used to catalytic metal, expressed as moles of water divided by moles of catalytic metal, is greater than or equal to 5,000 and less than or equal to 60,000.

7. The method of any one of claims 1 to 6, wherein the metal of the water-soluble transition metal complex catalyst is rhodium and the ligand comprises a water-soluble diphosphine or triarylphosphine.

8. 8. The method of claim 1, wherein the weight ratio of aqueous catalyst solution to solvent, expressed as the weight of catalyst solution divided by the weight of solvent, is 0.25 or more and 4 or less.

9. The method according to any one of claims 1 to 8, wherein the water-miscible solvent has a solubility in water at 20°C of 20 g / L or more.

10. 10. The process according to any one of claims 1 to 9, wherein the solvent is selected from the group consisting of linear or branched C2 to C5 alcohols or a mixture of at least two alcohols from this group.

11. The method according to any one of claims 1 to 10, wherein the solvent is isopropanol.

12. The method of any one of claims 1 to 11, wherein at least one ligand of the water-soluble transition metal complex catalyst comprises triphenylphosphine-3,3',3''-trisulfonic acid sodium salt.

13. 13. The method of any one of claims 1 to 12, wherein the water-soluble transition metal complex catalyst comprises a triarylphosphine ligand and a catalytic metal, wherein the molar ratio of triarylphosphine ligand used to catalytic metal, expressed as moles of triarylphosphine ligand divided by moles of catalytic metal, is 3 or more and 15 or less.

14. 14. The process of any one of claims 1 to 13, wherein the molar ratio of catalytic metal to olefin, expressed as moles of catalytic metal divided by moles of olefin, is 0.05% or more and 0.75% or less.

15. The method according to any one of claims 1 to 14, wherein the pH value of the aqueous catalyst solution is greater than or equal to pH 4 and less than or equal to pH 10.

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