EP1485341A2

EP1485341A2 - Method for the hydroformylation of olefins

Info

Publication number: EP1485341A2
Application number: EP03708195A
Authority: EP
Inventors: Walter Tötsch; Detlef Arnoldi; Alfred Kaizik; Martin Trocha
Original assignee: Oxeno Olefinchemie GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2002-03-15
Filing date: 2003-03-08
Publication date: 2004-12-15
Also published as: US20050171389A1; US6960699B2; JP4068064B2; BR0308432A; WO2003078365A3; CN1649815A; CN100503542C; AU2003212316A8; JP2005529853A; WO2003078365A2; AU2003212316A1

Abstract

The invention relates to a method for producing alcohols by the hydroformylation of olefins or olefin mixtures, separation of the catalyst and subsequent hydrogenation. According to said method, an extraction is carried out after the separation of the catalyst and prior to the hydrogenation of the aldehydes.

Description

Process for the hydroformylation of olefins

The invention relates to a process for the preparation of alcohols by hydroformylation of olefins or olefin mixtures in the presence of a cobalt catalyst, removal of the catalyst and subsequent hydrogenation, an extraction being carried out to remove residual catalyst contents before the hydrogenation.

Higher alcohols, in particular those having 7 to 25 carbon atoms, can be prepared, as is known, by catalytic hydroformylation (also referred to as oxo reaction) of the olefins poorer by one carbon atom and by subsequent hydrogenation of the aldehydes formed. The alcohols can be used as solvents or as precursors for detergents or plasticizers.

A large number of processes for the hydroformylation of olefins are known in the literature.

EP 0 562 451 and EP 0 646 563 describe the hydroformylation of mixtures containing 1- and 2-butene, in the first stage the 1-butene in a heterogeneous reaction, ie in a multi-phase system, optionally with the addition of a phase transfer reagent or solubilizer is implemented and in the second stage a homogeneously dissolved catalyst is used. According to EP 0 562 451, rhodium catalysts are used in both stages, while according to EP 0646 563, rhodium catalysts are used in the first stage and cobalt catalysts in the second stage. According to EP 0 562 451, the unreacted olefin, predominantly 2-butene, is hydroformylated in a second stage in a homogeneous phase and in the presence of rhodium as a catalyst. EP 0 646 563 specifies this procedure to the effect that the olefins which have not been converted in the first stage leave the reactor in gaseous form, together with carbon monoxide, hydrogen and butane formed by hydrogenation. H. an intermediate separation of the olefins is carried out. The separated gas is led into the second hydroformylation stage, optionally after compression.

GB 1 387 657 describes a two-stage hydroformylation in which the reaction product of the first stage is discharged in gaseous form and after the condensation Aldehydes or alcohols the exhaust gas of the first stage, which contains unreacted olefins, is partly returned to the first stage and the other part is passed to a second reactor.

Another variant of a two-stage hydroformylation is described in DE 32 32 557. In the first stage, the olefins are hydroformylated using a cobalt catalyst with conversions of 50 to 90%, the cobalt catalyst is separated from the reaction mixture and the aldehydes formed are introduced into a second hydroformylation stage together with the unreacted olefins. The ligand-modified cobalt catalyst used here not only effects the hydroformylation of the olefins, but also a hydrogenation of the aldehydes to the alcohols.

DE 100 34 360.0 describes a process for the multistage cobalt- or rhodium-catalyzed hydroformylation of olefins having 6 to 24 carbon atoms to alcohols and / or aldehydes, the olefins a) being hydroformylated in a hydroformylation step up to a conversion of 20 to 98% b) the catalyst is removed from the liquid reactor discharge thus obtained, c) the liquid hydroformylation mixture thus obtained is separated into a low boiler fraction containing olefins and paraffins and a bottom fraction containing aldehydes and / or alcohols, d) those contained in the low boiler fraction Olefins in further process steps, comprising process steps a, b and c, and the bottom fractions of process steps c) of all process steps are combined.

This process is preferably carried out in such a way that the liquid reactor discharge from the hydroformylation steps a) is a homogeneous liquid phase. The cobalt or rhodium catalysts are preferably used in such a way that they are homogeneously dissolved in the liquid reactor discharge from the hydroformylation steps a).

DE 198 42 368 AI describes a process for the preparation of higher oxo alcohols from mixtures of isomeric olefins having 5 to 24 carbon atoms by two stages Hydroformylation in the presence of a cobalt or rhodium catalyst at elevated temperature and pressure is described, in which the reaction mixture of the first hydroformylation stage is selectively hydrogenated, the hydrogenation mixture is separated by distillation in crude alcohol and low boilers consisting predominantly of olefins, these in the second hydroformylation stage leads, the reaction mixture of the second hydroformylation stage again selectively hydrogenated, the hydrogenation mixture mixture is separated into crude alcohol and low boilers in a distillation, the crude alcohol is worked up by distillation to pure alcohol and at least some of the low boilers are removed to remove saturated hydrocarbons.

The residual amount of cobalt catalyst remaining in the organic phase is generally less than 5 ppm cobalt (calculated as metal). These residual amounts of cobalt can have a negative impact on both the hydrogenation and the distillative workup over the course of the operating time.

It was found that the hydrogenation catalysts used are deactivated with the operating time by the residual cobalt content in the organic phase. Cobalt deposits were observed on the catalyst surface, especially during extended operation.

In addition to deactivating the catalyst, the cobalt deposits also impair the hydrodynamics and the mass and / or heat transport in the hydrogenation reactor.

EP 1 057 803 discloses a two-stage process for the preparation of alcohols from olefins or olefin mixtures. In the first reaction stage, the feed olefin is hydroformylated to 50 to 90% in the presence of a cobalt catalyst. After the catalyst has been separated off, the unreacted olefins are removed from the reaction discharge by distillation and the separated olefins are reacted in the second hydroformylation reactor. The hydroformylation products from both stages can be hydrogenated to the corresponding alcohols. In both reaction stages, Co ₂ (CO) ₈ or HCo (CO) _{4 is} used as the catalyst, which is generated outside the hydroformylation reactors. Before further processing by extraction with a base, the cobalt catalyst is removed from the reaction mixture of the hydroformylation. In most cobalt-catalyzed hydroformylation processes known from the literature, the cobalt catalyst (HCo (CO) ₄ or Co ₂ (CO) ₈ ) is oxidatively destroyed after the hydroformylation step. This is usually done by reacting the hydroformylation discharge with air in the presence of an aqueous phase, the cobalt II salts thus produced being extracted into the aqueous phase. The aqueous phase is separated off, for. B. by decanting in a phase separation container or in other suitable facilities. After separation from the aqueous phase, the organic phase is fed to a catalytic hydrogenation.

It was therefore the task of the present invention to reduce the cobalt content of the organic phase which is fed to the final hydrogenation within a hydroformylation process of olefins.

Surprisingly, the cobalt content of the aldehyde-containing fraction, which is hydrogenated to the desired alcohol, could be reduced to an almost harmless, low residual content by a simple extraction step with a water-containing liquid.

The present invention therefore relates to a process for the preparation of aliphatic alcohols having 7 to 17 carbon atoms by one or more reaction stages, each comprising the steps a) cobalt-catalyzed hydroformylation of olefins having 6 to 16 carbon atoms, b) treatment of the hydroformylation mixture with oxygen gases in the presence of acidic, aqueous cobalt (II) salt solutions, c) separation of the mixture from b) into an aqueous phase containing cobalt salts and an organic phase containing the aliphatic aldehydes, d) hydrogenation of the aldehyde-containing organic phase, characterized in that that e) the organic phase is extracted from c) with a liquid containing water.

In a process variant, at least one further step f) is carried out, with a complete or partial separation of the organic phase from b) into a by distillation

Low boiler fraction containing unreacted olefins and one containing aldehyde

Bottom fraction, wherein in step e) the organic phase and / or the aldehyde-containing Swamp fraction is extracted with a liquid containing water.

The method according to the invention can comprise one or more stages, each of steps a), b), c), d) and e) or steps a), b), c) and e) with a common method step d), include. Optionally step f) takes place in each stage or together for all stages.

If the process according to the invention is carried out in one step, the organic phase separated off in step c) can be carried out in whole or in part either in process step d) or f). The organic phase is preferably only partially continued in order to create an outlet for the otherwise enriching aliphatic compounds.

In these process variants, the process according to the invention is preferably carried out with 2, 3 or 4 stages.

The process according to the invention can be carried out continuously or batchwise with respect to each process step and each process step. All process steps are preferably carried out continuously. Several process variants are possible.

Version 1:

In this process variant, at least two reaction stages are run through, the low boiler fraction separated off in step f) being passed to step a) of the following reaction stage and the aldehyde-containing bottom fractions separated off in step f) of all reaction stages being hydrogenated in a common step d). In this process variant, steps a), b), c) and f) are therefore carried out successively and only the hydrogenation of the aldehyde fraction d) takes place together for all reaction stages.

The method according to variant 1 is shown as a block diagram in FIG. 1. In the first hydroformylation reactor 1, the olefin mixture 3, the synthesis gas 2 (carbon monoxide and hydrogen) and an aqueous solution of a cobalt compound or cobalt catalyst and water are fed. The hydroformylation mixture 5 thus obtained is let down, and the relaxed hydroformylation mixture is freed from cobalt compounds 4 in the first catalyst separation 8 after the decobalization 7 carried out with aqueous, acidic cobalt (II) salt solution and air. The expansion gas, ie synthesis gas not consumed, is drawn off via line 6 before the catalyst separation 8. The aqueous phase containing cobalt salts is returned to the first hydroformylation reactor 1, if appropriate after discharging a small substream and after supplementing it with fresh catalyst. With catalyst here are precursors of catalysts such. B. cobalt (II) salt solutions. The organic phase 9, which has been freed from the catalyst, is separated in a separation stage 10 into a hydrocarbon fraction 11, which mainly consists of unreacted olefins, and crude aldehyde 12. The low boilers 11, synthesis gas 13 and an aqueous solution of a cobalt compound or an already formed cobalt catalyst and water 16 are introduced into the second hydroformylation reactor 12. The hydroformylation mixture 14 from the second hydroformylation reactor 12 is again expanded, and the expansion gas 17 is drawn off after decobbing 18. The relaxed hydroformylation mixture 14 is freed from the catalyst in the second catalyst separation 19 after the second decobbing stage 18, which in turn is returned to the second hydroformylation reactor 12, if appropriate after discharging a small substream and after adding fresh catalyst (16). The decatalyzed hydroformylation mixture 19 can be separated in the separation stage 20 into a hydrocarbon fraction 21, which mainly consists of saturated hydrocarbons, and crude aldehyde 22. If necessary, part of the hydrocarbon fraction 21 can be returned to the reactor 12. (Line not shown in Fig. 1).

A further embodiment of this process variant is that the decobtained hydroformylation mixture 19 is fed to the hydrogenation 23 without separation in the separation stage 20 together with the crude aldehyde 12 from the first hydroformylation stage (line 25). The crude aldehydes 12 and 22 or 12 and 25 are hydrogenated in the hydrogenation reactor 23 to give the crude alcohol 24, which can optionally be worked up to pure alcohol in a distillation (not shown).

The extraction of the organic phases or the aldehyde-containing fractions according to the invention is possible at one or more points in this process variant. 1. Between the first catalyst separation (8) and the first distillation (10) in the extraction column 26.

2. After the first distillation (10) and the hydrogenation stage (23) in the extraction column (28).

3. Between the second catalyst separation (19) and the second distillation (20) in the extraction reactor (30) and / or

4. after the second distillation (20) and the hydrogenation stage (23) in the extraction reactor (32).

The extraction agent is supplied through lines (27), (29), (31) and / or (33).

The cobalt-containing extraction liquids obtained by the extraction process can be discharged (34) or, if necessary after concentration, returned to the catalyst circuit (35). 1 shows the further processing of the cobalt-containing extraction liquid as an example at the extraction stage 26. An analogous return is also possible for the extraction stages 28, 30 and / or 32.

In this embodiment of the invention, each process stage has a hydroformylation step a), a decobalting b), a catalyst separation step c) and a separation step f), with the proviso that the catalyst separated in c) is used directly or after working up in the hydroformylation step a) respective process stage is returned.

Optionally, this process variant can also be carried out in such a way that the last process stage has no separation step f).

Variant 2

In this process variant, two reaction stages are run through, the low boilers separated off in step f) of the first reaction stage being passed to step a) of the second reaction stage and the organic discharge from steps c) of both stages being passed to step f) of the first reaction stage. Here each reaction stage has a hydroformylation step a), a decobbing step b) and a catalyst separation step c), the separated catalyst phase in the respective Hydroformylation step is returned. The separated organic phase is separated in a separation step f) common to both reaction stages into a low boiler fraction and an aldehyde-containing subfraction. The low boiler fraction obtained in this way is passed into the hydroformylation step a) of the second reaction stage, the separated bottom fraction in a common hydrogenation step d).

The block diagram of this process variant is shown in FIG. 2. In the first hydroformylation reactor 1, the olefin mixture 3, the synthesis gas 2 (carbon monoxide and hydrogen) and an aqueous solution of a cobalt compound or cobalt catalyst are fed in together with water. The hydroformylation mixture 5 thus obtained is decompressed, and the decompressed hydroformylation mixture is freed of cobalt compounds 4 in the first catalyst separation 8 after the decobalization 7 carried out with aqueous, acidic cobalt (II) salt solution and air. The expansion gas, ie synthesis gas not consumed, is drawn off via line 6 before the catalyst separation 8. The aqueous phase containing cobalt salts is returned to the first hydroformylation reactor 1, if appropriate after discharging a small substream and after supplementing it with fresh catalyst. The decobtained organic phase 9 is passed into the separation stage 10. There, it is separated from the second hydroformylation reactor 14 together with the decobtained hydroformylation mixture 20 into a fraction 11, which contains the unreacted olefins and inert paraffins, and crude aldehyde 21. After a partial stream 12 has been discharged to remove saturated hydrocarbons (paraffins) and other non-olefinic compounds, the hydrocarbon fraction 11 is fed into the second hydroformylation reactor 14 together with synthesis gas 13 and an aqueous solution of a cobalt compound or a mixture of cobalt catalyst and water 19. The hydroformylation mixture 15 obtained in this way is depressurized, the flash gas 16 is drawn off after decobbing 17, and the decompressed hydroformylation mixture is freed from catalyst 19 in the second catalyst separation 18 in the second catalyst separation 18, which, if appropriate after discharging a small substream and supplementing it with fresh catalyst, is returned to the second hydroformylation reactor 14. The decobolded second hydroformylation mixture 20 is fed into the separation stage 10 with the hydroformylation mixture 9 of the first stage, as already mentioned. The crude aldehyde 21 will be hydrogenated with hydrogen to the crude alcohol 23 in the hydrogenation unit 22. This Alcohol can be worked up to the pure alcohol in a distillation (not shown).

In this process variant, the additional extraction of reaction step e) between the first catalyst separation (8) and the distillative separation (10) in the extractor (24) with the feed (25) and / or after the distillation stage (10) and before the hydrogenation stage ( 22) in the extractor (26) with the inlet (27) possible.

In this variant too, the extraction water containing cobalt can either be discharged from the extraction stages (28) or returned to the catalyst circuit (29). 2 shows this as an example for the extraction stage 24.

This embodiment of the invention has for each process step a hydroformylation step a), a decobalization step b) and a catalyst separation step c), the combined liquid hydroformylation mixtures being separated in a common distillation step f) into low boiler and bottom fractions, with the proviso that the catalyst separated in steps b) and c) is recycled directly or after working up to the hydroformylation step a) of the respective process stage.

Variant 3

In a further variant of the process according to the invention, two reaction stages are carried out, the low boilers separated off in step f) of the first reaction stage being passed into step a) of the second reaction stage and steps b), c) and d) being carried out together for both reaction stages. Here the hydroformylation steps a) of both reaction stages are worked up in common steps b, c and d.

This variant of the method according to the invention is shown in FIG. 3. The olefin mixture 3, the synthesis gas 2 (carbon monoxide and hydrogen) and an aqueous solution of a cobalt compound or a mixture of cobalt catalyst and partial stream 4 are fed into the first hydroformylation reactor 1. The hydroformylation mixture 5 thus obtained is expanded together with the hydroformylation mixture 18 from the second hydroformylation reactor 17 as combined hydroformylation outputs, and that Flash gas 7 (not used synthesis gas) after decobbing 7 is withdrawn. After decobbing stage 7, the organic phase in catalyst separation 8 is freed from catalyst 9. A mixture 10 is obtained which contains the aldehydes, alcohols and unreacted olefins formed. The catalytic converter 9 is divided into the two sub-streams 4 and 16, if appropriate after a partial quantity has been discharged and fresh catalyst has been added. Partial stream 4 is returned to the first hydroformylation reactor 1 and partial stream 16 to the second hydroformylation reactor 17. The decobtained hydroformylation discharge 10 is separated into the hydrocarbon fraction 12 and the crude aldehyde 14 in the separation stage 11. The hydrocarbon fraction 12, which contains the unreacted olefins, is optionally in the second, together with synthesis gas 15 and aqueous solution of a cobalt compound or a mixture of cobalt catalyst and water 16 after removal of a portion 13 for the separation of saturated hydrocarbons or other non-olefinic compounds Hydroforaiylierungsreaktor 17 initiated. The crude aldehyde 14 will be hydrogenated with hydrogen to the crude alcohol 20 in the hydrogenation unit 19. This can in turn be worked up to pure alcohol in a distillation (not shown).

In this process variant, the extraction e) can take place between the catalyst separation 8 and the distillative workup 11 in the reactor 21 with the feed 22, and / or between the distillative workup 11 and the hydrogenation stage 19 in the extraction reactor 23 with the water feed 24. The latter variant is preferably carried out.

In variant 3 it is also possible to discharge saturated hydrocarbons by separately working up a partial stream of the hydroformylation mixture 18, for example by separating off the low boilers by distillation.

As with variants 1 and 2, the cobalt-containing extraction solution can either be discharged (25) or returned to the catalyst circuit (26).

This embodiment of the process according to the invention is characterized in that the combined reactor discharges of all hydroformylation steps a) only one decobalting step b) and one catalyst separation step c) and one olefin separation step f) run through, with the proviso that the catalyst separated off in process steps b) and c) is divided up directly or after working up and the hydroformylation steps a) of the individual process steps are recycled.

The extraction e) can be carried out at various points in the method according to the invention. The reaction steps a) - d) are first explained in more detail below.

a) Hydroformylation Reaction The reactors in which the hydroformylation is carried out can be the same or different in all process stages. Examples of reactor types that can be used are bubble columns, loop reactors, jet nozzle reactors, stirred reactors and tubular reactors, some of which can be cascaded and / or provided with internals.

The starting materials for the process according to the invention are olefins or mixtures of olefins having 6 to 16 carbon atoms, advantageously having 8 to 16 carbon atoms, in particular having 8 to 12 carbon atoms and having terminal or internal CC double bonds. The mixtures can consist of olefins of the same, similar (+ 2) or significantly different (> + 2) carbon number. Examples of olefins which can be used either in pure form, in an isomer mixture or in a mixture with other olefins having a different C number as starting material are: 1-, 2- or 3-hexene, 1-heptene, linear heptenes with internal double bond (2-heptene, 3-heptene etc.), mixtures of linear heptenes, 2- or 3-methyl-1-hexene, 1-octene, linear octenes with internal double bond, mixtures of linear octenes, 2- or 3-methylheptene, 1-nonen, linear nonenes with an internal double bond, mixtures of linear nonenes, 2-, 3- or 4-methyloctenes, 1-, 2-, 3-, 4- or 5-decene, 2-ethyl-l-octene, 1- Dodecene, linear dodecenes with internal double bond, mixtures of linear dodecenes, 1-tetradecene, linear tetradecenes with internal double bond, mixtures of linear tetradecenes, 1-hexadecene, linear hexadecenes with internal double bond, mixtures of linear hexadecenes. Suitable starting materials are also the mixture of isomeric hexenes (dipropen) obtained in the dimerization of propene, the mixture of isomeric octenes (dibutene) obtained in the dimerization of butenes, the mixture of isomeric nonenes obtained in the trimerization of propene (Tripropen), the mixture of isomeric dodecenes (tetrapropene or tributes) obtained in the tetramerization of propene or the trimerization of butenes, the mixture of hexadecene (tetrabutene) obtained in the tetramerization of butenes and by cooligomerization of olefins with different C numbers (preferred 2 to 4) prepared olefin mixtures, optionally after separation by distillation into fractions with the same or similar (+2) C number. Furthermore, olefins or olefin mixtures which have been produced by Fischer-Tropsch synthesis can be used. In addition, olefins produced by olefin metathesis or by other technical processes can be used. Preferred starting materials are mixtures of isomeric octene, nonenes, dodecenes or hexadecenes, ie oligomers of lower olefins, such as n-butenes, isobutene or propene. Other educts which are also very suitable are oligomers of C ₅ olefins.

In principle, there are three process variants for the oligomerization of butenes to mixtures essentially containing C ₈ olefins. The oligomerization on acidic catalysts has long been known. B. zeolites or phosphoric acid can be used on supports. This gives isomer mixtures of branched olefins, which are essentially dimethylhexenes (WO 92/13818). Another process which is carried out worldwide is oligomerization with soluble Ni complexes, known as the DIMERSOL process (see J. Schulze, M. Homann, "C ₄ Hydrocarbons and Derviates", Springer-Verlag, Berlin, Heidelberg 1989, p. 69 and B. CORNILS, WA HERRMANN, "Applied Homogeneous Catalysis with Organic Metallic Compounds"; Vol. 1 & 2, VCH, Weinheim, New York 1996). The third process variant is the oligomerization on nickel fixed bed catalysts; one of these methods is the OCTOL process (Hydrocarbon Process., Int. Ed. (1986) 65 (2. Sect.l) pages 31-33).

A C ₈ -olefin mixture which has been obtained from linear butenes by the OCTOL process is preferably used for the production of a C-alcohol mixture according to the invention, which is particularly suitable for the preparation of plasticizers.

The hydroformylation of the olefins takes place in the process according to the invention in the presence of cobalt catalysts, preferably unmodified catalysts such as HCo (CO) and / or Co ₂ (CO) ₄ and water. It can be either preformed or a catalyst Catalyst precursors, such as a cobalt compound, from which the actual catalyst is formed in the reactor, are fed into the hydroformylation reactor.

When the finished active catalyst (e.g. HCo (CO) ₄ and / or Co ₂ (CO) ₄ ) is used, water, olefin, catalyst and synthesis gas are fed to the reactor. Water can be dispersed in the olefin before the reactor, for example by using a static mixer. However, it is also possible to mix all the components in the reactor first.

The amount of water in the hydroformylation reactor can be varied within a wide range. By adjusting the quantitative ratio of water and olefin and the reaction parameters, for example temperature, water can be homogeneously dissolved or additionally dispersed in the liquid hydroformylation discharge.

In the process according to the invention, the formation of the catalyst (HCo (CO) ₄ and / or Co ₂ (CO) ₄ ) in the hydroformylation reactor is preferred. For example, such a process is described in DE 196 54 340. According to this process, the starting materials, such as the cobalt salt solution, the organic phase and the synthesis gas, are introduced simultaneously, preferably with the aid of a mixing nozzle, in cocurrent from below into the reactor.

Cobalt salts such as formates, acetates or salts of carboxylic acids which are water-soluble are preferably used as cobalt compounds. Cobalt acetate, which is used as an aqueous solution with a cobalt content of 0.5 to 3 mass%, preferably 0.8 to 1.8 mass%, calculated as metal, has proven particularly useful. Another preferred feed solution for the preparation of the catalyst is the aqueous cobalt salt solution which is obtained in separation step c).

The amount of water desired in the hydroformylation reactor can be introduced with the cobalt salt solution, the concentration of which can be varied within a wide range. However, it is also possible to feed in additional water in addition to the cobalt salt solution.

Of particular importance is the dosing of the cobalt-catalyzed process Starting materials added to the reactor. The metering device must ensure good phase mixing and the generation of the largest possible phase exchange area. It is also advantageous to divide the reactor space of the hydroformylation reactors by installing 1 to 10, preferably 2 to 4, perforated plates arranged perpendicular to the flow direction of the reactant and product stream. The cascading of the reactor greatly reduces backmixing compared to the simple bubble column and the flow behavior approximates that of a tubular reactor. The result of this procedural measure is that both the yield and the selectivity of the hydroformylation are improved.

Precise information on hydroformylation steps can be found in DE 199 39 491 AI and DE 101 35 906.3.

According to DE 199 39 491, a partial stream of the liquid mixed phase (aqueous cobalt salt solution / organic phase) is drawn off from the lower part of the reactor and fed in at a higher point in the reactor.

According to DE 101 35 906.3, the level of an aqueous phase is kept constant in the hydroformylation reactor, the concentration of cobalt compounds (calculated as metallic cobalt) in this aqueous bottom phase being in the range from 0.4 to 1.7% by mass.

The same or different conditions can be set in the hydroformylation steps, temperatures from 100 to 250 ° C. and pressures from 100 to 400 bar are preferred. Temperatures of 140 to 210 ° C and syngas pressures of 200 to 300 bar have proven particularly useful. The volume ratio of carbon monoxide to hydrogen in the synthesis gas is generally between 2: 1 and 1: 2, in particular in the volume ratio of 1: 1.5. The synthesis gas is advantageously used in excess, for example up to three times the stoichiometric amount.

In the case of multi-stage process variants, the hydroformylation is advantageously carried out in the first process stage, in which the more reactive olefins are reacted, at temperatures between

140 to 195 ° C, preferably at 160 to 185 ° C. In this process stage, olefin conversions between 20 and 95%, preferably between 50 and 80% sought.

In the liquid hydroformylation discharge, the concentration of cobalt compounds (calculated as metallic cobalt) is 0.01 to 0.5% by mass, in particular 0.02 to 0.08% by mass (based on the sum of the organic and aqueous phases).

Due to the different possibilities of adding water, the water content in the entry of the hydroformylation reactor is difficult to determine. In the following, information is therefore given about the discharge from the reactor, the water content in the reactor discharge being practically synonymous with the water content of the liquid phase during the reaction.

The water concentrations in the liquid hydroformylation outputs can be between 0.1 and 10 mass%, in particular between 0.5 and 5 mass%. The water contents of the hydroformylation outputs from the individual stages are the same or different. The water is preferably dissolved homogeneously in the liquid hydroformylation outputs.

b) catalyst separation

After leaving the hydroformylation reactors, the product discharges are let down to 10 to 15 bar and passed into the respective separation stage c), including decobolding b). In decobbing step b), the product question (liquid organic phase) of the hydroformylation reaction a) in the presence of acidic, aqueous cobalt (II) salt solutions (“process water”) with oxygen-containing gases, in particular air or oxygen, at temperatures from 90 to 160 ° C implemented and thus oxidatively freed from cobalt-carbonyl complexes. The hydroformylation-active cobalt carbonyl complexes are destroyed to form cobalt (II) salts. The decobalization methods are well known and detailed in the literature, e.g. B by J. FALBE, in "New Syntheses with Carbon Monoxide", Springer Verlag (1980), Berlin, Heidelberg, New York, page 158 ff.

The solution used has a pH of 1.5 to 4.5 and a cobalt content as in the hydroformylation step, preferably between 0.8 to 2.0% by mass.

The decobalting b) is preferably carried out in a container with packing such as Raschig rings, filled pressure vessel in which the largest possible phase exchange area is generated. The practically cobalt-free organic product phase is separated from the aqueous phase in a downstream separation container, ie the actual separation stage c). The aqueous phase, the "process water", which contains the back-extracted cobalt recovered from the organic phase in the form of cobalt acetate / formate, is returned entirely or after a small amount has been discharged into the oxo-reactor of the respective process stage and preferably as a starting material for the in-situ preparation of the cobalt-catalyst complexes used.

Optionally, part of the excess formic acid can be removed before the process water is returned to the hydroformylation reactor. This can be done for example by distillation. Another possibility is to decompose part of the formic acid, for example catalytically, as described in DE 100 09 207. It is also possible to prepare the actual hydroformylation catalyst (Co (CO) ₈ and / or HCo (CO) ₄ ) from the cobalt salt solution obtained in the decobalization by precarbonylation and to return it to the hydroformylation reactor.

c) Distillative separation

The organic reaction product which is obtained after the hydroformylation step and the decobalization contains unreacted olefins, aldehydes, alcohols, formic acid esters and high boilers and traces of cobalt compounds. This discharge is fed to a material separation (step f), in which the low boilers, preferably the unreacted olefins, are separated from the valuable products (aldehyde, alcohol, formates).

The olefins can be separated from the hydroformylation products, for example by distillation or steam distillation.

The low boiler fraction (top fraction) contains the unreacted olefins, the paraffins formed by hydrogenation of olefins, water and possibly small amounts of valuable products. It is passed into the hydroformylation step of the next reaction stage or optionally the last reaction stage. Optionally, the water is e.g. B. separated in a settier and returned to the decoblocating stages or the extraction stages. d) hydrogenation

The fractions obtained after the unreacted olefins have been separated off with the hydroformylation products of each hydroformylation stage can be hydrogenated separately or together (step d).

Optionally, it is possible to hydrogenate the decarburized hydroformylation mixture of the last stage without removing the olefins. Step f) is omitted in this process variant, at least in the last stage.

You can z. B. use copper, nickel, copper / nickel, copper / chrome, copper / chrome / nickel, zinc / chrome, nickel / molybdenum catalysts. The catalysts can be unsupported, or the hydrogenation-active substances or their precursors can be applied to supports, for example aluminum oxide or silicon dioxide.

Preferred catalysts, on which the hydroformylation mixtures are hydrogenated, each contain 0.3 to 15% by mass of copper and nickel, and as activators 0.05 to 3.5% by mass of chromium and advantageously 0.01 to 1.6% by mass , preferably 0.02 to 1.2 mass% of an alkali component on a support material, preferably aluminum oxide and silicon dioxide. The quantities given relate to the catalyst which has not yet been reduced. The alkali component is optional.

The catalysts are advantageously used in a form in which they offer low flow resistance, e.g. B. in the form of granules, pellets or moldings, such as tablets, cylinders, extrudates or rings. They are appropriately activated before use, e.g. B. by heating in a hydrogen stream.

The hydrogenation, preferably a liquid phase hydrogenation, is generally carried out under a total pressure of 5 to 100 bar, in particular between 15 and 50 bar. Hydrogenation in the gas phase can also be carried out at lower pressures, with correspondingly large gas volumes. If several hydrogenation reactors are used, the total pressures in the individual reactors can be the same or different within the pressure limits mentioned. The reaction temperatures for hydrogenation in the liquid or gaseous phase are generally between 120 and 220 ° C., in particular between 140 and 180 ° C. Examples of such hydrogenations are described in patent applications DE 198 42 369 and DE 198 42 370.

In the process according to the invention, the hydrogenation is optionally carried out in the presence of water. The water required can be contained in the reactor feed. However, it is also possible to feed water into the hydrogenation apparatus at a suitable point. In the case of gas phase hydrogenation, water is expediently supplied in the form of water vapor. A preferred hydrogenation process is liquid phase hydrogenation with the addition of water, as described for example in DE 100 62448.0.

The hydrogenation is preferably carried out at a water content of 0.05 to 10% by mass, in particular 0.5 to 5% by mass, very particularly 1 to 2.5% by mass. The water content is determined on the hydrogenation discharge.

e) extraction

In order to remove traces of cobalt compounds, it is expedient to remove the streams fed to the hydrogenation, i. H. subject the organic phases from separation step c) or the aldehyde-containing bottom fractions from step f) separately or together to one or more extractions with a water-containing liquid.

The extractions e) can take place before and / or after the separation or separations f). Only one extraction is expediently carried out directly before the hydrogenation stage d).

The residual cobalt contents in the organic phase are usually between 1 and 5 ppm cobalt. In the event of a malfunction, e.g. B. with a phase separation that is not working optimally, the residual amounts of cobalt in the organic phase can also assume significantly higher values.

The extraction according to the invention removes the residual content of cobalt compounds from the organic phases to such an extent that their content of cobalt compounds (calculated as cobalt) is below 0.5 mass ppm, in particular below 0.2 mass ppm, very particularly is reduced below 0.1 mass ppm. As a result, the specific consumption of the overall process of cobalt compounds can be reduced and the decrease in the activity of the hydrogenation catalyst by deposition of cobalt or cobalt compounds can be reduced, as a result of which longer catalyst service lives are achieved.

Without the additional extraction step according to the invention, the typical catalyst service lives are approximately 2 to 3 years. These downtimes can increase residual cobalt contents, e.g. B. caused by operational disruptions can be reduced to half a year.

According to previous experience, the life of the catalyst can be significantly extended by extracting the residual cobalt contents according to the invention, i. H. at least doubled.

For the extraction of the cobalt compounds from the aldehyde-containing mixtures which are fed to the hydrogenation, the extraction apparatus known to the person skilled in the art, such as, for example, simple extraction columns, sieve plate columns, packed columns or columns with moving internals, can be used. Examples of extractors with moving internals are u. a. the turntable extractor and the Scheibel column. Another apparatus that is used for extraction in particular at high throughputs is the so-called mixer-settler-extractor. Two or more extractors of the same or different types can also be combined with one another.

In the process according to the invention, the extraction of the cobalt compounds is preferably carried out as countercurrent extraction. A sieve plate or packed column, very particularly preferably a sieve plate column, is preferably used as the extractor. The extractant (receiver phase) is fed as the heavier phase near the top and the cobalt-containing organic aldehyde-containing phase (donor phase) as the lighter phase near the bottom of the column

The receiver phase is preferred in a straight pass or with recirculation (Circular procedure) fed to the extraction column. The cobalt concentration (calculated as cobalt) in the extract (column leaving exiting phase) is below 2% by mass, in particular below 1% by mass, very particularly below 0.5% by mass.

In the cycle mode, e.g. B. in mixer-separator extraction, the cobalt concentrations of the receiver phase are accordingly limited such that the above-mentioned cobalt values in the extract are not exceeded.

The throughput ratio (mass / mass) between organic phase and fresh aqueous phase is between 200/1 and 5/1, preferably between 100/1 and 25/1. The

Extraction column is preferably operated in such a way that the organic phase is the dispersed phase. For this purpose, it may be expedient to use special inlet devices which cause the organic phase in the form of small droplets to enter the

Extraction column is introduced. The extraction is carried out at temperatures between 10 and 180 ° C, in particular between 15 and

110 ° C, especially between 40 and 90 ° C. At higher temperatures (approx.

100 ° C), so that the two phases, in particular water, are in liquid form, are operated under pressure.

In addition to (pure) water as the extraction agent, aqueous solutions or mixtures with water such as water-acid mixtures, preferably mineral acids or carboxylic acids such as formic acid or acetic acid-water mixtures, in particular aqueous formic acid mixtures, can be used as the water-containing liquid for the extraction of the cobalt compounds , The acid concentration of the aqueous solutions is between 0.1 and 5% by mass, in particular between 0.5 and 1.5% by mass.

In order to avoid loss of aldehydes due to oxidation, the extraction is preferably carried out in the absence of oxygen.

The pH of the extractant is preferably <7. It is also possible to use a mixture or a solution of water and an organic solvent, in particular the alcohol to be prepared. The extraction e) can, as shown in variants 1-3, be carried out at various points in the process. The extraction e) is preferably carried out once in each process stage or after the last stage, either before or after the separation by distillation f), very particularly preferably directly before the hydrogenation d).

Processes are also possible in which the olefin-containing discharges from the separation by distillation are selectively hydrogenated or dehydrogenated. Here, too, an extraction stage e) can be added.

The extracts loaded with cobalt compounds can be returned to suitable points in the process. For example, the extracts can be fed into one or more decobalization stages. Another possibility is to introduce the extracts into one or more hydroformylation reactors. Furthermore, the extracts can be introduced both in one or more decobalization stages and in one or more hydroformylation reactors. Alternatively, the extracts can be returned to separation stages c).

By recycling the extracts, the amounts of cobalt and water that have been discharged with the organic phases from upstream stages can be compensated. If the extracts contain more water than is used in the upstream stages, the extracts can be concentrated before recycling, for example by distilling off water.

The aldehyde-containing fractions freed from traces of cobalt compounds are finally passed into one or more hydrogenation stages.

The hydrogenation product or products are worked up in one or more distillations to give the pure alcohols. In the case of high-boiling alcohols, distillation under reduced pressure is preferred.

The alcohols prepared by the process according to the invention can be used, for example, as solvents or as precursors for plasticizers. B. as phthalic acid esters or detergents be used.

The following example is intended to explain the invention without restricting the scope which results from the description and the patent claims.

Examples: Extraction of cobalt with water in a pilot plant extractor

A starting material for the extraction experiments was a cobalt-containing hydroformylation mixture from the cobalt-catalyzed dibutene hydroformylation with residual cobalt contents of 5 ppm. The hydroformylation mixture contained 6.5% by weight of C8 hydrocarbons, 35.6% by weight of C9 aldehydes, 49.7% of C9 alcohols, 3.5% by weight of isononyl formates and 4.5% by weight of high boilers ,

In a pilot plant extractor made of stainless steel (8000 mm long, 50 mm diameter) with 20 sieve trays, 50 kg of the hydroformylation mixture (organic phase) were fed to the extractor sump every hour. In countercurrent to the organic phase, 0.5 kg of water were fed in as an extractant at the extractor head every hour.

The extraction experiments were carried out at a temperature of 85 ° C and a pressure of 5 bar.

After reaching the steady-state operating state, the aqueous phase in the extractor sump and the organic phase at the reactor head were examined for cobalt contents.

Under the selected conditions, cobalt contents of 492 ppm (± 10 ppm) were determined in the aqueous phase. The organic phase leaving the extractor contained on average 0.075 ppm (+ 0.005 ppm) cobalt. According to this result, the residual cobalt contents in the organic phase can be reduced by around 98% by countercurrent extraction with water.

Claims

claims:

1. Process for the preparation of aliphatic alcohols with 7 to 17 carbon atoms by one or more reaction stages, each comprising the steps a) cobalt-catalyzed hydroformylation of olefins with 6 to 16 carbon atoms, b) treatment of the hydroformylation mixture with oxygen-containing gases in the presence of acidic, aqueous cobalt (II) salt solutions, c) separation of the mixture from b) into an aqueous phase containing cobalt salts and an organic phase containing the aliphatic aldehydes, d) hydrogenation of the aldehyde-containing organic phase, characterized in that e) the organic phase from c) is extracted with a liquid containing water.

2. The method according to claim 1, comprising a further step f) complete or partial separation by distillation of the organic phase from b) into a low boiler fraction containing unreacted olefins and an aldehyde-containing bottom fraction, in step e) the organic phase from c ) and / or the aldehyde-containing bottom fraction from f) is extracted with a liquid containing water.

3. The method according to claim 1 or 2, characterized in that the extraction (step e) is carried out with pure water.

4. The method according to claim 1 or 2, characterized in that the extraction is carried out with an aqueous solution or mixture of water with a mineral acid, a carboxylic acid and / or an organic solvent.

5. The method according to any one of claims 1 to 4, characterized in that the pH of the liquid containing water is less than or equal to 7.

6. The method according to any one of claims 1 to 5, characterized in that at least two reaction stages are run through, the organic phase separated in step c) being passed completely or partially into step a) of the following reaction stage.

7. The method according to any one of claims 2 to 6, characterized in that the low boiler fraction separated in step f) is wholly or partly recycled in step a).

8. The method according to any one of claims 2 to 6, characterized in that at least two reaction stages are run through, wherein the low boiler fraction separated in step f) is passed into step a) of the following reaction stage.

9. The method according to any one of claims 2 to 6, characterized in that at least two reaction stages are run through, the low boiler fraction separated in step f) passed into step a) of the following reaction stage, and the bottom fractions separated off in step f) of all reaction stages are hydrogenated in a common step d).

10. The method according to any one of claims 2 to 6, characterized in that two reaction stages are run through, the first in step f)

Reaction stage separated low boilers in step a) of the second reaction stage and the organic phase of steps b) of both stages in step c) of the first Reaction stage are passed.

11. The method according to any one of claims 2 to 6, characterized in that two reaction stages are run through, the low boilers separated off in step f) of the first reaction stage being passed into step a) of the second reaction stage and steps b), c) and d ) are carried out together for both reaction stages.