Process for hydroformylation of diisobutylene and C4 to C7 olefins

Abstract

The present invention provides a process for the hydroformylation of diisobutylene and C4 to C7 olefins in a common reaction zone. The hydroformylation is carried out with synthesis gas in the presence of a homogeneous catalyst system comprising at least Co or Rh and optionally a phosphorus-containing ligand.

Description

[0001] The present invention relates to a process for the hydroformylation of diisobutylene and C4 to C7 olefins in a common reaction zone. The hydroformylation is carried out with synthesis gas in the presence of a homogeneous catalyst system comprising at least Co or Rh and optionally a phosphorus-containing ligand.

[0002] Diisobutene is an industrially relevant product obtained by dimerization of isobutene. Diisobutene consists of the isomers 2,4,4-trimethylpent-1-ene (2,4,4-trimethylpent-1-ene) (hereinafter also referred to as: TMP1) and 2,4,4-trimethylpent-2-ene (2,4,4-trimethylpent-2-ene) (hereinafter also referred to as: TMP2), the mass distribution of TMP1:TMP2 being about 78:22 to 81:19 (equilibrium distribution). Industrial mixtures containing C4 olefins are light petroleum fractions from refineries, C4 fractions from FC crackers or steam crackers, mixtures from Fischer-Tropsch synthesis, mixtures from butane dehydrogenation, and mixtures produced by metathesis or other industrial processes. C5 olefins, i.e. pentenes, are present in light petroleum fractions from refineries or crackers. Higher olefins can be obtained in particular by oligomerization. Both diisobutylene and C4 to C7 olefins can be converted by hydroformylation into valuable products, such as esters formed in the hydroformylation.

[0003] The problem of this method is that special production equipment must be obtained or built, and these equipment must be operated under the cost incurred thereby. Because the market of petrochemical products is quite changeable in some cases, it is almost impossible to economically operate the special production equipment of each kind of described olefin. Another shortcoming is that because all equipment all need maintenance, it is almost impossible for the resource efficient operation of multiple production equipment. This not only requires economic and personnel costs, but also requires a certain amount of energy, such as electricity or heat transfer medium.

[0004] It was therefore an object of the present invention to provide a process which does not exhibit the abovementioned problems. In particular, diisobutene and C4 to C7 olefins can be converted into valuable products via hydroformylation in a more resource-efficient manner.

[0005] The basic object is achieved by the method according to claim 1. Preferred embodiments are specified in the dependent claims.

[0006] According to the present invention, the process for the hydroformylation of diisobutylene and C4 to C7 olefins comprises at least the following steps:

[0007] a. providing a diisobutylene stream containing 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, and providing an olefin stream containing the C4 to C7 olefins;

[0008] b. in a reaction zone, diisobutylene and C4 to C7 olefins are hydroformylated with synthesis gas in the presence of a homogeneous catalyst system comprising at least Co or Rh and optionally a phosphorus-containing ligand to obtain a preferably liquid product mixture comprising at least the aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes formed by the hydroformylation, the homogeneous catalyst system and unreacted olefins, i.e. unreacted diisobutylene and unreacted C4 to C7 olefins;

[0009] c. removing the homogeneous catalyst system from the preferably liquid product mixture to obtain a crude product mixture comprising at least the aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes formed by the hydroformylation, and the unreacted olefins; and

[0010] d. treating the crude product mixture by distillation in at least one distillation column to remove the unreacted olefins, thereby obtaining an aldehyde mixture containing the aldehyde 3,5,5-trimethylhexanal formed and C5 to C8 aldehydes, wherein the unreacted olefins are preferably removed and recycled to the hydroformylation in step b.

[0011] Thus, the process according to the invention involves the simultaneous reaction of diisobutylene and C4 to C7 olefins in a single common reaction zone. This procedure has a number of advantages.

[0012] The method allows a flexible response to the market, in particular to small production volumes. In addition, only one production plant is required, which can be operated more efficiently and therefore in a more resource-saving manner even when market demand fluctuates. The specific boiling sequence also allows the resulting products of the various olefins employed to be separated, while the reactants can be returned directly to the reaction or after further treatment.

[0013] The diisobutene stream provided in step a comprises 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene. In a preferred embodiment, the proportion of 2,4,4-trimethylpent-1-ene in the diisobutene stream is at least 60 mol%, preferably at least 70 mol%, based on the total diisobutene stream. This stream can be, for example, a diisobutene stream produced by dimerization of isobutene or an isobutene-containing hydrocarbon mixture according to the process disclosed in EP 1 360 160 B1. In addition, the diisobutene stream to be employed here can be obtained as an unreacted residual stream in a carbonylation process such as alkoxycarbonylation or hydroformylation.

[0014] Step a comprises providing not only a diisobutylene stream, but also an olefin stream containing C4 to C7 olefins used in the process according to the invention. In a preferred embodiment, the present invention employs an olefin stream comprising C4 olefins, particularly preferably a C4 olefin stream. The corresponding streams are known to those skilled in the art and can be obtained on a large industrial scale.

[0015] Olefin streams comprising C4 olefins include, for example, light petroleum fractions from an oil refinery, C4 fractions from a FC cracker or steam cracker, mixtures from Fischer-Tropsch synthesis, mixtures from butane dehydrogenation, or streams produced by metathesis or other industrial processes. For example, C4 olefin streams suitable for use in the method according to the invention can be obtained from the C4 fraction of a steam cracker. C5 olefins, i.e. pentenes, are present in light petroleum fractions from an oil refinery or cracker. C6 olefins can be obtained, for example, by dimerization of propylene. C7 olefins can be obtained, for example, by dimerization of propylene and butenes.

[0016] The feed stream provided in step a, i.e., a diisobutylene feed stream and a C4 to C7 olefin feed stream, is sent to the hydroformylation in step b. The feed stream can be sent to the hydroformylation in step b or premixed individually and separately. Preferably, before the hydroformylation in step b, the diisobutylene feed stream and the C4 to C7 olefin feed stream are mixed. A particularly preferred embodiment of the present invention actually provides that before the hydroformylation in step b, the diisobutylene feed stream, the C4 to C7 olefin feed stream and the homogeneous catalyst system are mixed, particularly in a suitable mixing vessel. If there is a recycle stream that is recycled to the reaction, i.e., for example, by recycling the catalyst system, the recycle stream can be sent to the mixing vessel equally.

[0017] Step b comprises reacting diisobutylene, i.e. 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, with synthesis gas (a mixture of carbon monoxide (CO) and hydrogen (H2)) to obtain aldehydes. Thus, the number of carbon atoms in the aldehyde increases by 1 carbon atom compared to the diisobutylene used. Diisobutylene (8 carbon atoms) correspondingly produces an aldehyde having 9 carbon atoms, i.e. 3,5,5-trimethylhexanal. Thus, the hydroformylation according to the present invention converts C4 to C7 olefins into C5 to C8 aldehydes.

[0018] The synthesis gas used in the process according to the invention can be used in different mixing ratios of carbon monoxide and hydrogen. The molar ratio between the synthesis gas and the hydrocarbon stream used containing the olefins to be hydroformylated should be 6:1 to 1:1, preferably 3:1 to 1:1, particularly preferably 2:1 to 1:1.

[0019] The hydroformylation can optionally be carried out in the presence of further solvents known to those skilled in the art, although preference is given to using no further solvents and the olefin employed serves as solvent in the hydroformylation.

[0020] Homogeneous catalyst systems that can be used for the hydroformylation contain Co or Rh, preferably Rh, and optionally phosphorus-containing ligands. Corresponding catalyst systems are familiar to those skilled in the art. Preferably, phosphorus-containing ligands are used.

[0021] In a particularly preferred embodiment, the homogeneous catalyst system comprises Rh and a phosphorus-containing ligand or is composed of Rh and a phosphorus-containing ligand. Suitable ligands for the catalyst system according to the present invention are known to those skilled in the art. The phosphorus-containing ligand for the catalyst system according to the present invention is preferably a phosphine (e.g. TPP (triphenylphosphine)), a monophosphite (e.g. Alkanox 240 (tris (2,4-di-tert-butylphenyl) phosphite) or a bisphosphite (e.g. biphephos). A mixture of ligands may also be used.

[0022] The temperature during the homogeneously catalyzed hydroformylation is preferably 80 to 250° C., further preferably 90 to 225° C., particularly preferably 100 to 210° C. The pressure during the homogeneously catalyzed hydroformylation is preferably 100 to 350 bar, further preferably 175 to 325 bar, particularly preferably 200 to 300 bar.

[0023] The pressure during the hydroformylation generally corresponds to the total gas pressure. In the context of the present invention, the total gas pressure is understood to mean the sum of the prevailing pressures of all gaseous substances present, i.e. the pressure of the (total) gas phase. In the present process, this corresponds in particular to the sum of the partial pressures of CO and H, i.e. the total gas pressure is the synthesis gas pressure.

[0024] Homogeneous catalysis hydroformylation can be operated as a liquid output method ("liquid recycle") or as a gas output method ("gas recycle"). These two method variants are known to those skilled in the art and are described in many textbooks. In the context of the present invention, there is no need to particularly select such a method, because the method can be carried out in two ways in principle. In homogeneous catalysis, it is important in any case to separate the catalyst system from the reaction output. In the case of liquid output, this can be achieved, for example, via a flash process or membrane separation. In the case of gaseous output, for example, by condensation / or washing. This is also known to those skilled in the art and does not require a comprehensive explanation. The further post-treatment of the reaction output, in particular the separation of the reaction products, is also familiar to those skilled in the art and can be carried out, for example, by means of thermal separation methods such as distillation. In the context of the present invention, thermal separation / thermal separation methods are understood to refer to separation methods in which separation is achieved by means of boiling point.

[0025] The hydroformylation in step b takes place in a suitable reaction zone. The reaction zone for the reaction comprises at least one reactor, but may also consist of two or more reactors arranged in parallel or in series. The at least one reactor may in particular be selected from a stirred tank reactor, a loop reactor, a jet loop reactor, a bubble column reactor or a combination thereof. If more than one reactor is used, the reactors may be identical or different.

[0026] The hydroformylation in step b gives a preferably liquid product mixture which comprises at least the aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes formed by the hydroformylation, the homogeneous catalyst system and unreacted olefins, namely diisobutylene and C4 to C7 olefins.

[0027] The product mixture thus obtained, preferably in a liquid state, is supplied to a subsequent step c to remove the homogeneous catalyst system from the product mixture. Before supplying the product mixture, low-boiling components, such as low-boiling by-products, can be removed, for example, by thermal separation (flash, distillation, etc.), for which reason it may be necessary to reduce the pressure on the high-pressure product mixture.

[0028] A preferred embodiment of the present invention also includes cooling the product mixture to a temperature of 40° C. to 100° C., preferably 50° C. to 95° C., particularly preferably 60° C. to 90° C., before the separation in step c. This requires suitable cooling equipment. The cooling is carried out in particular in an output cooler. Apparatus that has proven suitable includes, for example, a tube bundle heat exchanger, in which the reaction mixture is preferably passed through the tubes and the cooling medium is preferably passed through the shell of the heat exchanger.

[0029] The cooling of the product mixture ensures a reduction in the catalyst metal usage factor. The problem is that during the hydroformylation and the subsequent separation, a small part of the metal, in particular rhodium, is always lost in one way or another. Due to the high price of the metal to be employed, in particular the metal, this increases the process costs, since the losses must be compensated by replenishment. However, the cooling according to the invention has the effect of reducing the utilization factor, i.e. less catalyst metal, in particular rhodium, is lost, and therefore less replenishment is required. This therefore makes it possible to significantly reduce the process costs.

[0030] Removal of the homogeneous catalyst system in step c to obtain a crude product mixture can be achieved by means of various separation methods, such as by thermal separation and / or by membrane separation. Suitable methods are familiar to those skilled in the art. Preferably, thermal separation is first performed, such as evaporation, followed by membrane separation. In evaporation, mainly product aldehydes (trimethylhexanal and C5 to C8 aldehydes) and unconverted diisobutylene and C4 to C7 olefins are obtained as a crude product mixture at the top of the tower. A high-boiling phase containing a homogeneous catalyst, trimethylhexanal and in some cases C5 to C8 aldehydes and any high-boiling substances formed is obtained at the bottom. Then the high-boiling phase can be subjected to membrane separation to discharge any high-boiling substances. As is well known, membrane separation produces a retentate and a permeate. The catalyst system will accumulate in the retentate. The permeate can be sent for further treatment.

[0031] The retentate here contains a homogeneous catalyst system. According to the present invention, the retentate is preferably recycled to the hydroformylation in step b / the reaction zone for carrying out the hydroformylation. This allows the catalyst system to be reused. In the preferred continuous execution of the claimed method, this produces a catalyst cycle, wherein only the smaller catalyst losses associated with the method need to be compensated at most. If, according to a preferred embodiment, before the hydroformylation in step b, a diisobutylene stream, C4 to C7 olefins and a homogeneous catalyst system are mixed, in particular in a suitable mixing vessel, the retentate is sent to the mixing vessel.

[0032] Any suitable membrane material can be used for membrane separation. Preferably, an OSN (organic solvent nanofiltration) membrane material is used in the membrane separation after evaporation in the method of the present invention. Such a membrane material preferably consists of at least a separation active layer (also referred to as an active separation layer) and a substructure on which the separation active layer is present. The membrane material of the present invention preferably consists of at least a separation active layer and a substructure.

[0033] The substructure preferably has a porous structure, which is permeable to the permeate that has passed through the separation active layer. The substructure has a stabilizing function and is used as a support for the separation active layer. The substructure can be composed of any suitable porous material in principle. Suitable materials are familiar to those skilled in the art. However, the prerequisite is that the material is stable for acid and alkali. The substructure can be composed of the same material as the separation active layer. The preferred material for the substructure includes plastics, such as polypropylene (PP), polyethylene (PE) or non-condensation polymers that are not easily hydrolyzed or alcoholyzed, such as polysulfone, polytetrafluoroethylene (PTFE), polyethersulfone (PES), polyvinylidene fluoride (PVDF) or polyacrylonitrile (PAN).

[0034] The separation active layer according to the invention preferably consists of a PAEK (polyaryletherketone) polymer. PAEK has a specific feature that in the repeating unit, the aromatic groups are alternately connected via ether functions and ketone functions. The separation active layer preferably according to the invention consists of PEEK (polyetheretherketone). As the separation active layer, it is particularly preferred to use a PEEK polymer with a sulfonation degree of less than 20%, particularly preferably a sulfonation degree of less than 10%. The corresponding PEEK polymers and their production are described in WO 2015 / 110843 A1.

[0035] The membrane separation in step c is preferably carried out at a temperature of 25° C. to 100° C., further preferably 30° C. to 80° C., particularly preferably 40° C. to 70° C. In order to bring the product mixture to the preferred main temperature for membrane separation, the product mixture can be cooled. In addition to active cooling using a coolant, cooling can also be achieved via a heat exchanger, in which thermal energy is transferred to another stream, thereby cooling the product mixture and heating the other stream.

[0036] In the membrane separation in step c, the transmembrane pressure (transmembrane pressure) (TMP) is preferably 10 bar to 60 bar, further preferably 15 bar to 55 bar, particularly preferably 40 bar to 50 bar. The permeate side pressure here can be higher than atmospheric pressure, preferably up to 15 bar, preferably 2 bar to 7 bar. The difference between TMP and the permeate side pressure produces the retentate side pressure. In a preferred embodiment, particularly in the case of pressure ratio and permeate side pressure, care should be taken to ensure that the set pressure is avoided to evaporate after passing through the membrane. Evaporation may cause unstable operation.

[0037] In the subsequent step d, the crude product mixture is treated by distillation in at least one distillation column to remove unreacted olefins (diisobutylene and C4 to C7 olefins). This gives an aldehyde mixture comprising the aldehyde 3,5,5-trimethylhexanal formed and C5 to C8 aldehydes.

[0038] In the distillation treatment of the crude product mixture in step d, unreacted olefins, i.e. unreacted diisobutylene and unreacted C4 to C7 olefins, are obtained at the top of at least one distillation column. The mixture of aldehydes thus formed accumulates at the bottom of at least one distillation column. The top stream containing unreacted olefins can be recycled to the hydroformylation / reaction zone in step b. If the components used have undergone mixing before hydroformylation, the top stream is supplied to the mixing according to definition. This allows the method of the present invention to be operated continuously with the highest possible yield. A purge can be taken out from the recycled top stream to discharge low-boiling by-products from the method.

[0039] The distillation treatment for removing unreacted olefins in step d can be carried out in a distillation column. It is conceivable to carry out the distillation treatment for removing unreacted olefins in step d in two or more distillation columns. However, this will require significantly higher equipment costs. Therefore, it is preferred to carry out the distillation treatment in step d in a single distillation column.

[0040] In the distillation treatment in step d, the pressure in the distillation column is preferably 0.3 bar to 2 bar, more preferably 0.4 bar to 1 bar, particularly preferably 0.5 bar to 0.7 bar. In the distillation treatment in step d, the temperature in the bottom of the distillation column is preferably 80° C. to 160° C. In the distillation treatment in step d, the temperature at the top of the distillation column is preferably 30° C. to 80° C. In addition, it is preferred that the reflux ratio in the distillation column is 1 to 2. The distillation column used for the removal in step d preferably comprises 10 to 30 theoretical plates. The distillation column may contain a high-performance structured packing. Suitable high-performance structured packings are known to those skilled in the art.

[0041] As mentioned above, the distillation process obtains an aldehyde mixture comprising aldehydes formed from diisobutylene and C4 to C7 olefins. In order to obtain the two aldehydes in the highest possible purity, a further distillation step can be carried out to separate the aldehydes from each other. The aldehydes from the C4 to C7 olefins will be obtained at the top of the distillation column, while the aldehydes from the diisobutylene will be obtained at the bottom of the distillation column. It is also conceivable to use dividing wall columns to obtain the aldehydes as pure components at different points in the column. Suitable technical configurations of dividing wall columns are familiar to those skilled in the art and can be obtained on a large industrial scale.

[0042] The present process is particularly suitable for the hydroformylation of diisobutylene and C4 to C7 olefins. In the context of the present invention, certain combinations of olefins are particularly preferred:

[0043] In a preferred embodiment, the process involves the hydroformylation of diisobutylene and C4 olefins (i.e. 1-butene, cis- and / or trans-2-butene, isobutylene or mixtures thereof). The aldehyde formed from diisobutylene is 3,5,5-trimethylhexanal. Valeraldehyde, 2-methylbutanal or 3-methylbutanal are formed from C4 olefins. Thus, with a mixture of butenes, a mixture of the aldehydes is also obtained.

[0044] In a particularly preferred embodiment, the process involves the hydroformylation of diisobutylene and isobutylene. The aldehyde formed from diisobutylene is 3,5,5-trimethylhexanal. 3-Methylbutyraldehyde is formed from isobutylene.

[0045] The present invention is explained below with reference to Examples. The Examples relate to preferred embodiments and should not be construed as limiting the present invention.

Claims

1. A process for the hydroformylation of diisobutylene and C4 to C7 olefins, wherein the process comprises at least the following steps: a. providing a diisobutylene stream containing 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, and providing an olefin stream containing the C4 to C7 olefins; b. hydroformylating diisobutylene and C4 to C7 olefins with synthesis gas in the presence of a homogeneous catalyst system comprising at least Co or Rh and optionally a phosphorus-containing ligand in a reaction zone to obtain a preferably liquid product mixture comprising at least the aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes formed by the hydroformylation, the homogeneous catalyst system and unreacted olefins; c. removing the homogeneous catalyst system from the preferably liquid product mixture to obtain a crude product mixture comprising at least the aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes formed by the hydroformylation, and the unreacted olefins; and d. treating the crude product mixture by distillation in at least one distillation column to remove the unreacted olefins, thereby obtaining an aldehyde mixture containing the formed aldehyde 3,5,5-trimethylhexanal and C5 to C8 aldehydes.

2. The process according to claim 1, wherein the hydroformylation in step b is carried out at a temperature of 90 to 250°C, preferably 120 to 200°C, particularly preferably 120 to 170°C.

3. The process according to claim 1 or 2, wherein the hydroformylation in step b is carried out at a pressure of 100 bar to 350 bar, preferably 175 bar to 325 bar, particularly preferably 200 bar to 300 bar.

4. The process according to claim 1, wherein the proportion of 2,4,4-trimethylpent-1-ene in the diisobutene stream is at least 60 mol %, preferably at least 70 mol %.

5. The process according to any one of the preceding claims, wherein the removal of the homogeneous catalyst system in step c is achieved by thermal separation and / or membrane separation.

6. The process according to any one of the preceding claims, wherein the removal of the homogeneous catalyst system in step c is achieved by evaporation and subsequent membrane separation.

7. The process according to any one of claims 1 to 5, wherein the removal of the homogeneous catalyst system in step c is achieved by membrane separation.

8. The process of claim 7, wherein the homogeneous catalyst system accumulates in the retentate.

9. The process according to any one of the preceding claims, wherein the diisobutylene stream, the C4 to C7 olefin stream and the homogeneous catalyst system are preliminarily mixed in a mixing vessel before being sent to the reaction zone.

10. The process according to any one of the preceding claims, wherein the distillation treatment in step d. is carried out in a single distillation column. 11 . The process according to claim 10 , wherein the pressure in the distillation column is 0.3 bar to 2 bar, preferably 0.4 bar to 1 bar, particularly preferably 0.5 bar to 0.7 bar.

12. The process according to claim 10 or 11, wherein the temperature in the bottom of the distillation column is 80 to 160°C.

13. The method according to any one of claims 10 to 12, wherein the temperature at the top of the distillation column is 30°C to 80°C.

14. The process according to any one of the preceding claims, wherein in step d, the unreacted olefin is removed and recycled to the hydroformylation step b.

15. The process according to any one of the preceding claims, wherein C4 olefins are used, preferably isobutene, as a result of which the aldehyde mixture obtained is a mixture of 3,5,5-trimethylhexanal and valeraldehyde, 2-methylbutanal or 3-methylbutanal, preferably 3-methylbutanal.