WO2002068371A1

WO2002068371A1 - Method for producing aldehydes

Info

Publication number: WO2002068371A1
Application number: PCT/EP2002/001379
Authority: WO
Inventors: Hans Bohnen; Jürgen HERWIG
Original assignee: Celanese Chemicals Europe Gmbh
Priority date: 2001-02-22
Filing date: 2002-02-09
Publication date: 2002-09-06
Also published as: DE10108475A1

Abstract

The invention relates to a two-step hydro formylation method, wherein the first step is carried out in a homogenous manner using a dissolved rhodium complex catalystors and the waste gas is introduced to a second hydro formylation step, wherein the olefinically unsaturated compounds contained in the waste gas are hydro formulated in a homogenous reaction system in the presence of xanthene skeleton based diphosphines.

Description

Process for the preparation of aldehydes

The invention relates to an improved process for the hydroformylation of olefinically unsaturated compounds in using the unreacted olefins escaping from the hydroformylation zone with the exhaust gas.

It is known to react compounds containing olefinic double bonds with carbon monoxide and hydrogen to form aldehydes (oxosynthesis). The process is not limited to the use of olefinic hydrocarbons, but also extends to starting materials which, in addition to the double bond, also have functional groups, predominantly those which remain unchanged under the reaction conditions.

Classic oxosynthesis works with cobalt as a catalyst. Its effectiveness is based on the formation of cobalt carbonyl compounds under the

/ Exposure to hydrogen and carbon monoxide at pressures above 20

MPa and temperatures of about 120 ° C and more on metallic cobalt or cobalt compounds.

In the course of the further development of oxo synthesis, cobalt was increasingly replaced by rhodium as the catalyst metal. Rhodium is used as a complex compound which, in addition to carbon monoxide, preferably contains phosphines as ligands. Rhodium as a metal makes it possible to work at low pressures, moreover, higher yields are achieved and the unbranched products which are more valuable for further processing are preferably formed when starting from straight-chain terminal olefins.

Such a process is known from US-A-3,527,809 under the name low pressure rhodium process. An improvement on this process discloses US-A-4, 148,830. According to this procedure, the catalyst life and the yield of linear aldehydes can be increased if the high-boiling condensation products of the aldehydes formed are used as solvents for the catalyst and the excess phosphine. The deposition of insoluble rhodium compounds can be avoided and the dissolved catalyst can be reused over many catalytic cycles without a decrease in activity being observed. The process known from US-A-4, 148,830 is also referred to as "hydroformylation process with liquid recycling".

For reasons of process economy, in particular in order to avoid large reactors or long reaction times, the reaction is not carried out until the olefinically unsaturated compounds are completely consumed, but is often satisfied with the conversion of only 60 to 95% of the starting material to the desired end compound. In addition to excess carbon monoxide and hydrogen, the exhaust gas leaving the hydroformylation zone therefore contains unreacted olefinic feedstock which can be converted into valuable materials by differently designed processes.

The implementation of the olefinically unsaturated compounds contained in the exhaust gas of a first hydroformylation zone in a downstream second hydroformylation zone is known from EP-A1-0 188 246. In the first stage, olefin, carbon monoxide and hydrogen are reacted with the return of liquid or gas in the presence of a soluble rhodium-phosphorus complex catalyst, free phosphorus ligand and higher-boiling aldehyde condensation by-products. The exhaust gas, which contains olefin, optionally aldehyde, furthermore hydrogen, carbon monoxide and alkane by-product, is fed to a decoupled, ie separately operated, secondary rhodium-catalyzed hydroformylation process in which the exhaust gas is recirculated with liquid or gas together with added carbon monoxide and hydrogen for reaction brought. The known method also allows the reaction of olefins, which are available as a mixture of terminal and internal olefinic compounds, such as. B. a mixture of isomeric butenes. In the first reaction stage, mainly the terminal olefins contained in the exhaust gas are reacted and in the second reaction stage.

Such a process variant is particularly important, in which the second reaction stage is carried out under those reaction conditions under which the internal olefins are converted into the straight-chain aldehydes with high selectivity. The conversion of internal olefins into the straight-chain aldehydes with high selectivity is known from EP-B1-0 213 639, in which special diphosphites are used as ligands.

However, the widespread use of diphosphite ligands is restricted by their lower stability compared to conventional phosphine ligands and their greater sensitivity to hydrolysis and traces of hydrolysis, and the phosphonous acids formed during the continuously operated hydroformylation process adversely affect the catalyst life and have to be removed from the process at great expense be, e.g. by treating the catalyst-containing solution with an alkaline ion exchanger before returning it to the hydroformylation process.

The processes known from the prior art allow a high conversion of the olefinically unsaturated compounds used to the aldehydes. However, since the straight-chain unbranched aldehydes are generally preferred, there is a need for a process for the hydroformylation of olefinically unsaturated compounds with high conversion and at the same time high selectivity to the straight-chain unbranched aldehydes. The known diphosphite ligands allow the hydroformylation of internal olefins to give straight-chain aldehydes with high selectivity, but due to their known sensitivity to hydrolysis, diphosphite ligands tend to form phosphonous acids, which can have a detrimental effect on the rhodium complex catalyst and thus lead to a shortening of the catalyst life.

The object was therefore to develop a process which, under economically justifiable conditions, allows olefinic compounds containing in the exhaust gas of a hydroformylation reaction to be converted with high selectivity to the straight-chain carbonyl compounds, the process to be provided being supposed to show an advantageously long catalyst life.

The invention therefore consists in a process for the hydroformylation of olefinically unsaturated compounds, the reaction in a first reaction stage in a homogeneous reaction system using organic phosphorus (III) compounds in complex bonds containing rhodium compounds as catalysts at pressures of 0.2 to 20 , 0 MPa and exhaust gas is bidet. It is characterized in that the offgas is fed to the first reaction stage of a second reaction stage in which amounts of the olefinically unsaturated compounds present in the offgas are present in a homogeneous reaction system in the presence of complex compounds of rhodium and diphosphines of the general formula (I)

(I)

in which R ¹ and R ^{2 are} each the same or different (C ¹ -C ₁₈ ) alkyl radicals, (C ₆ -C ₄ ) aryl radicals, (C ₇ -C ₂ ) aralkyl radicals or (C ₇ - C ₂ ) -Alkylaryl radicals, R ^{3 represents} hydrogen or a -CHR ^a R ^b radical in which R ^a and R ^{b are} each the same or different hydrogen, (Ci-Ci ₈ ) alkyl-, (Cι-Ca) -Alkoxy radicals, unsubstituted or substituted with (Cι-Cιo) alkyl and / or (Cι-C ₁₀ ) alkoxy radicals (C ₆ -Cι ₄ ) aryl radicals or (C ₇ -C ₂₄ ) - Aralkyl radicals, and R ⁴ (d-Cιo) alkyl radicals, (C ₆ -C ₄ ) aryl radicals, (C ₇ -C ₂₄ ) aralkyl radicals or (C ₇ -C ₂₄ ) - Represent alkylar l residues, are implemented at pressures of 0.2 to 20 MPa.

These diphosphines are derived from the xanthene scaffold as the base and attached oxaphosphine. The diphosphines of the general formula I and their production process are the subject of a patent application filed on the same day, which is hereby expressly incorporated by reference (“incorporated by reference”).

Among the diphosphines of the general formula I, those diphosphines in which R ¹ and R ^{2 are} each the same or different are particularly suitable (Cι-C ₁₂₎ -alkyl radicals, (C ₆ -C ₁₀₎ -aryl residues, (C ₇ -Cι ₀₎ aralkyl radicals or (C ₇ - Cιo) alkylaryl radicals,

R ^{3 represents} hydrogen or a radical -CHR ^a R ^b , in which R ^a and R ^{b are} each identical or different hydrogen, (-CC ₂ ) alkyl-, (CrC ₄ ) -alkoxy radicals, unsubstituted or with (Cι -C ₈ ) alkyl and / or (-C-C ₄ ) alkoxy radicals are substituted (C ₆ -C ₁₀ ) aryl radicals or (C ₇ -Cι ₀ ) aralkyl radicals, and R ⁴ ( d- C ₈ ) alkyl radicals, (C ₆ -C ₁₀ ) aryl radicals, (C ₇ -C ₁₀ ) aralkyl radicals or (C ₇ -C ₁₀ ) alkylaryl radicals.

The aryl radical is preferably in each case the phenyl or naphthyl radical, and the benzyl radical is preferably used as the aralkyl radical.

For example, R ¹ and R ^{2 are} identical or different and are methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, tertiary butyl, n-pentyl, i-pentyl, n-hexyl, i-hexyl , n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, phenyl, naphthyl, tolyl or benzyl.

R ³ stands for example for methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, n-pentyl, i-pentyl, 3,3-dimethylbutyl, n-hexyl, i-hexyl, n-heptyl, i -Heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, phenyl, naphthyl, tolyl or benzyl. R ⁴ stands for example for methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, tertiary butyl, n-pentyl, i-pentyl, 3,3-dimethylbutyl, n-hexyl, i-hexyl, n- Heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, phenyl, naphthyl, tolyl or benzyl.

The new process ensures that the majority of the olefinic compounds not converted in the exhaust gas in the first stage are hydroformylated to give straight-chain aldehydes.

The starting material for the overall process is not only limited to olefinically unsaturated compounds with terminal double bonds. The process according to the invention is also suitable for the hydroformylation of those starting olefins in which the terminal and internal Double bond is present in a molecule or are available in the art as a mixture of olefins with terminal and internal double bonds. Such a mixture is, for example, a mixture of isomeric butenes.

In particular, the new process succeeds in converting the olefinically unsaturated compounds contained in the exhaust gas with internal double bonds, which only react to a minor extent in the first stage, to linear aldehydes. In this way, based on the overall process, in addition to excellent conversions of the olefinically unsaturated compounds to the carbonyl compounds, high selectivities to the desired straight-chain carbonyl compounds can also be achieved.

The high efficiency of the process according to the invention could not be predicted. On the one hand, it should be noted that the olefinically unsaturated compounds in the exhaust gas are in considerable dilution and that their contents can be between 20 and 65% by weight, depending on the olefin used. Despite the low initial concentration of olefinically unsaturated compounds, the second hydroformylation stage can be carried out with a high conversion.

Surprisingly, the diphosphine ligands of the general formula (I) used according to the invention in the second hydroformylation stage prove to be very stable. It is therefore possible to run the entire process over many catalytic cycles without a decrease in activity and selectivity. A frequent and expensive catalyst work-up after only a few catalytic cycles is therefore not necessary.

The first reaction stage of the new process is carried out in a homogeneous reaction system. The term homogeneous reaction system stands for a homogeneous solution composed essentially of solvent, catalyst, olefinically unsaturated compound and reaction product. The higher-boiling solvents have proven to be particularly effective solvents. the condensation compounds of the aldehydes to be prepared, in particular the trimers of the aldehydes to be prepared, which are obtained as by-products in the hydroformylation, and their mixtures with the aldehydes to be prepared, so that a further addition of solvent is not absolutely necessary. In some cases, however, the addition of a solvent may prove useful. Organic compounds in which the starting material, reaction product and catalyst system are soluble are used as solvents. Examples of such compounds are aromatic hydrocarbons, such as benzene and toluene or the isomeric xylenes and mesitylene. Other common solvents are paraffin oil, cyclohexane, n-hexane, n-heptane or n-octane, ethers such as tetrahydrofuran, ketones or Texanol® from Eastman. The proportion of solvent in the reaction medium can be varied over a wide range and is usually between 20 and 90% by weight, preferably 50 to 80% by weight, based on the reaction mixture.

Rhodium complex compounds are used as catalysts, which contain organic Pho ^ pho ^ ll compounds as ligands. Such complexy compounds and their preparation are known (for example from US-A-3,527,809, US-A-4,148,830, US-A-4,247,486, US-A-4,283,562). They can be used as uniform complex compounds or as a mixture of different complex compounds. The rhodium concentration in the reaction medium extends over a range from about 1 to about 1000 ppm by weight and is preferably 10 to 700 ppm by weight. In particular, rhodium is used in concentrations of 25 to 500 ppm by weight, based in each case on the homogeneous reaction mixture. The stoichiometrically composed rhodium complex compound can be used as a catalyst. However, it has proven expedient to carry out the hydroformylation in the presence of a catalyst system composed of rhodium-phosphorus complex compound and free, ie excess phosphorus ligand which no longer forms a complex compound with rhodium. The free phosphorus ligand can be the same as in the rhodium Complex compound, but ligands different from this can also be used. The free ligand can be a single compound or consist of a mixture of different organophosphorus compounds. Examples of rhodium-phosphorus complex compounds which can be used as catalysts are described in US Pat. No. 3,527,809. The preferred ligands in the rhodium complex catalysts include e.g. B. triarylphosphines such as triphenylphosphine, trialkylphosphines such as tri (n-octyl) phosphine, trilaurylphosphine, tri (cyclohexyl) phosphine, alkylphenylphosphines, cycloalkylphenylphosphines and organic diphosphites. Because of its easy accessibility, triphenylphosphine is used particularly frequently.

The molar ratio of rhodium to phosphorus is usually 1: 1 to 1: 1000 in the homogeneous reaction mixture, but the molar proportion of phosphorus in the form of organic phosphorus compounds can also be higher. Rhodium and organically bound phosphorus are preferably used in molar ratios of 1: 3 to 1: 500. When using trarylphosphines, rhodium to phosphorus molar ratios of 1:50 to 1: 300 have proven particularly useful. If trialkylphosphines are used as ligands, the molar ratio of rhodium to phosphorus is preferably 1: 3 to 1: 100.

The conditions under which the reaction takes place in the first reaction stage can vary within wide limits and can be adapted to the individual circumstances. They depend, among other things, on the feedstock, the catalyst system selected and the degree of conversion aimed for. The hydroformylation of the starting materials is usually carried out at from 50 to 160.degree. Temperatures of from 60 to 150 ° C. and in particular from 75 to 140 ° C. are preferred. The total pressure extends over a range from 0.2 to 20.0 MPa, preferably 1 to 12 MPa and in particular 1 to 7 MPa. The molar ratio of hydrogen to carbon monoxide usually ranges between 1:10 and 10: 1, Mixtures which contain hydrogen and carbon monoxide in a molar ratio of 3: 1 to 1: 3, in particular about 1: 1, are particularly suitable.

The catalyst is usually formed from the components rhodium or rhodium compound, organic phosphorus compound and synthesis gas under the conditions of the hydroformylation reaction in the reaction mixture. However, it is also possible to first preform the catalyst and then to feed it to the actual hydroformylation stage. The preforming conditions generally correspond to the hydroformylation conditions.

The reaction conditions in the first stage can be selected so that the olefinically unsaturated compounds with terminal double bonds are reacted in a targeted manner. The reaction conditions are expediently set so that the conversion to the straight-chain aldehydes takes place with the highest possible selectivity. The selectivities to be achieved for the straight-chain aldehydes are, however, particularly influenced by the ligands containing phosphorus.

Influence Even if, in individual cases, the first stage also works towards a more or less large partial conversion, depending on the phosphine ligand used, an aldehyde mixture with a fairly high proportion of branched aldehydes can be obtained in the first stage. If one wishes to work specifically towards an aldehyde mixture with a high content of straight-chain aldehydes, those known phosphite ligands, for example triaryl phosphites, which are known to preferably give linear aldehydes, should be selected.

If one uses a mixture of olefins with terminal and internal double bond, e.g. B. a mixture of isomeric butenes, one expediently selects those reaction conditions under which the

Olefins with a terminal double bond are preferably implemented. The unreacted olefins, mostly those with an internal double bond, are therefore enriched in the exhaust gas of the first reaction stage.

The reaction product of the first reaction stage is separated off from the catalyst, for example distilled off. The residue containing the catalyst after removal of the aldehyde is returned to the reaction zone, if appropriate after addition of fresh catalyst and removal of part of the aldehyde condensation products formed in the course of the reaction.

The waste gas escaping from the first reaction stage (waste gas stream) is composed of the waste gas which is taken directly from the reactor (reactor waste gas) in order to avoid an accumulation of inert substances in the circulated gas mixture and the gaseous components which are present in the separation of catalyst and crude reaction product, e.g. in the distillation of the aldehyde from the reaction product. (Product gas). The exhaust gas stream essentially consists of unreacted olefinic compound, carbon monoxide, carbon dioxide, hydrogen and the hydrogenation products of the olefin. If olefinically unsaturated compounds with terminal double bonds are used as the starting olefin for the overall process, the exhaust gas stream only contains residual amounts of olefinically unsaturated compound, depending on whether partial conversion or almost complete conversion is aimed for in the first stage. If the starting material for the process according to the invention contains olefins with internal double bonds, these are only converted to a minor extent in the first stage and are therefore enriched in the exhaust gas stream.

The exhaust gas stream is generally without further intermediate treatment, in particular without purification, but if necessary after admixing

Hydrogen alone or in a mixture with carbon monoxide as a feed of a second hydroformylation step. In separate cases However, it may prove expedient to clean the exhaust gas stream before use in the second hydroformylation stage.

The second hydroformylation stage is decoupled, i.e. operated independently of the first hydroformylation stage with a catalyst different from the first hydroformylation stage. As in the first reaction stage, the amounts of olefinically unsaturated compounds present in the exhaust gas stream are also reacted in a homogeneous reaction system with carbon monoxide and hydrogen. Those solvents are used as solvents which have also proven themselves in the first reaction stage.

Rhodium complex compounds which contain diphosphines of the general formula (I) as ligands are used as catalysts.

Among the diphosphines of the general formula I, those diphosphines are particularly suitable as ligands which, on the one hand, are readily soluble in the reaction mixture, so that there are no precipitations of the diphosphine itself under process conditions, even over many catalytic cycles. On the other hand, the diphosphines and the rhodium complex compounds derived from them must have high long-term stability under the hydroformylation conditions and thus ensure homogeneous reaction control even over many catalytic cycles. An indication of a high long-term stability is the constant homogeneity of the organic catalyst solution over many catalytic cycles, since the decomposition products of the rhodium-containing complex compounds and the ligands generally have only a low solubility in the organic solvent and fail.

The following diphosphines are particularly suitable: 2,7-bis (3,3-dimethylbutyl) -9,9-dimethyl-4,5-bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (II), 2, 7,9-trimethyl-9-n-nonyl-4,5-bis (2J-dimethyl-10-phenoxaphos- phino) xanthene (III), 2,7-di-n-decyl-9,9-dimethyl-4,5-bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (IV), 2,7-di- n-hexyl-9,9-dimethyl-4,5-bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (V), 2,7- (3,3-dimethylbutyl) -9,9-dime - thyl-4,5-bis [2,7-di (3,3-dimethylbutyl) -10-phenoxaphosphino] xanthene (VI), 2,7-dimethyl-9,9-dimethyl-4,5-bis [2nd , 7-di (3,3-dimethylbutyl) -10-phenoxaphosphino-xanthene (VII).

III

IV

V

VI

VII Of particular importance is the sufficient solubility of the diphosphines of the general formula I in the reaction mixture, which is so high that no precipitation of the ligand occurs under process conditions even over many catalytic cycles.

The solubility of the individual ligands does not follow any easily understandable laws. Surprisingly, it was found that the radicals R ³ on the two aromatic carbon rings of the xanthene skeleton in the general formula I can have a particularly strong influence on the solubility, while the introduction of the substituents R ⁴ on the phenoxaphosphine radical on its own only shows very little influence on solubility.

The increase in carbon atoms is not a criterion by which the solubility behavior can be read off. Furthermore, the solubility of the xanthene skeleton without phenoxaphosphine substituents does not indicate the solubility behavior of the ligand with phenoxaphosphine substituents.

The solubility behavior of the diphosphines of the general formula I and of the diphosphines (II) to (VII) which are particularly suitable for the process according to the invention is dealt with in the patent application filed on the same day, to which reference is hereby expressly incorporated (“incorporated by reference”).

It has surprisingly been found that when the diphosphines of the general formula I and in particular the diphosphines of the formulas II to VII are used, a concentration of diphosphine in the reaction solution which is sufficient for the continuous reaction in the hydroformylation can be set. In particular, the diphosphines II, IV, V and VI have excellent solubility in the reaction mixture. The complex compounds obtained from rhodium and diphosphines of the general formula I can be used as uniform complex compounds or as a mixture of different complex compounds. The rhodium concentration ranges from 1 to 1000 ppm by weight and is preferably 50 to 500 ppm by weight. In particular, rhodium is used in concentrations of 100 to 300 ppm by weight, based in each case on the homogeneous reaction mixture. Due to their solubility, the phosphorus (HO concentration in the form of the diphosphines can be adjusted to a value of 4 mol P (III) per kilogram of homogeneous reaction solution. The phosphorus (III) content in the reaction mixture usually ranges from 10 to 400 mmol P (III), preferably 10-100 mmol P (III) and in particular 10-50 mmol P (III) per kilogram of reaction mixture.

As in the first stage of the reaction, the stoichiometrically composed rhodium complex compound can be used as the catalyst. However, it has proven to be expedient to carry out the hydroformylation in the presence of a catalyst system composed of rhodium-diphosphine complex compounds and free diphosphine, ie excess diphosphine, which no longer forms a complex compound with rhodium. The free diphosphine can be the same as in the rhodium complex compound, but diphosphines other than this can also be used as ligands. The free ligand can be a single compound or consist of a mixture of different diphosphines. Preferably 1 to 20 mol of phosphorus is used per mol of rhodium in the form of the diphosphines, but the molar proportion of the phosphorus can also be higher. Due to the good solubility of the diphosphines used according to the invention, a higher molar ratio of up to 80 mol phosphorus per mol rhodium can also be set. However, it is expedient to work with lower molar ratios of up to 20 mol of phosphorus per mol of rhodium. When using

a molar ratio of rhodium to phosphorus of 1:15 has proven itself as ligand.

The reaction pressure in the second stage of the overall process is in the range of 0.2 to 20.0 MPa. It has proven particularly useful to maintain pressures between 1 and 12 MPa and in particular between 1 and 5 MPa. The composition of the synthesis gas for the second hydroformylation stage can vary over a wide range. In general, the molar ratio of carbon monoxide to hydrogen is between 1:10 and 10: 1. Mixtures containing carbon monoxide and hydrogen in a molar ratio of 1: 2 and 2: 1 are particularly suitable. In particular, it has proven to be advantageous to use synthesis gas with a slight excess of hydrogen.

The reaction temperatures in the second stage of the new process are 50 to 160 ° C. Temperatures of 60 to 150 ° C and in particular 75 to - 140 ° C are preferred.

Rhodium is used either as a metal or as a compound. In metallic form, it is used either as finely divided particles or deposited in a thin layer on a support such as activated carbon, calcium carbonate, aluminum silicate, alumina. Suitable rhodium compounds are salts of aliphatic mono- and polycarboxylic acids, such as rhodium 2-ethylhexanoate, rhodium acetate, rhodium oxalate, rhodium propionate or rhodium malonate. Rhodium salts of inorganic hydrogen and oxygen acids, such as rhodium nitrate or rhodium sulfate, the various rhodium oxides or rhodium carbonyl compounds such as Rh ₃ (CO) ι ₂ or Rh ₆ (CO) ι ₆ or complex compounds of rhodium, for example cyclopentadienylrhodium compounds or rhodium acetylacetonate, can also be used , Rhodium halogen compounds are less suitable because of their corrosive behavior of the halide ions.

Rhodium oxide and in particular rhodium acetate and rhodium 2-ethylhexanoate are preferred. Rhodium metal and the rhodium compounds suitable for catalyst production for the second reaction stage can also be used for catalyst production in the first reaction stage.

/ The catalyst is usually formed from the components rhodium or rhodium compound, the diphosphine or the diphosphines of the general formula I and synthesis gas under the conditions of the hydroformylation reaction in the reaction mixture. However, it is also possible to first preform the catalyst and then to feed it to the actual hydroformylation stage. The preforming conditions generally correspond to the hydroformylation conditions.

According to a tried and tested embodiment, the crude aldehyde of the first reaction stage is passed in countercurrent to a fresh synthesis gas in a stripping column. Here, heat is transferred from the aldehyde to the synthesis gas and the olefinic compound dissolved in the aldehyde is expelled from the crude product and returned to the reaction together with the heated synthesis gas. The implementation can be carried out batchwise or continuously. The reaction product of the second reaction stage is distilled off from the catalyst. It can be combined with the product of the first stage and further processed, for example distilled. The remaining after the separation of the aldehyde, the catalyst-containing distillation residue of the second stage, optionally after addition of fresh catalyst and removal of part of the aldehyde condensation products formed in the course of the reaction, is returned to the second hydroformylation stage.

The reaction of the olefinically unsaturated compounds contained in the exhaust gas stream in the second reaction stage in the presence of the rhodium-diphosphine complex compounds according to the invention gives the desired linear aldehydes with excellent selectivity. Furthermore, the catalyst system used according to the invention in the second hydroformylation stage is distinguished by a long catalyst service life.

The second stage is generally carried out to a partial conversion in order to ensure a high selectivity for the straight-chain aldehydes and to avoid excessive damage to the catalyst and excess ligand.

In terms of the overall process, the new process makes it possible to convert olefinically unsaturated compounds into the linear aldehydes with high selectivity and excellent selectivity.

By choosing the reaction conditions in the first and second stages, which control the conversion and selectivity, for example by choosing the organic phosphine or phosphite ligand in the first stage, the new process opens up the possibility of the proportions of n- and iso-compounds adapt to the respective requirements in the reaction product via the overall process. According to a further embodiment of the invention Process, the ratio of n- and iso compound in the overall process can also be influenced by the addition of olefin to the exhaust gas mixture which is fed to the second hydroformylation stage.

The process according to the invention can be applied to olefinically unsaturated compounds of any structure. Accordingly, suitable starting materials are both olefins having an internal and also a terminal double bond, and straight-chain and branched olefins. In addition, the olefins can also contain functional groups, in particular those which are not changed in the course of the reaction. Polyunsaturated compounds, such as 1, 3-butadiene or 1, 3 pentadiene, are also suitable as starting materials. Mixtures of olefinically unsaturated compounds with terminal and internal double bonds are also suitable. In particular, the mixture of butene-1 and butene-2 available in the art, also referred to as raffinate II, a butene-1-depleted raffinate II, which is also referred to as raffinate III, or an octene-2 and / or octene C ₈ -olefin mixture containing 3 can be used as starting compound in the process according to the invention. The process according to the invention is particularly suitable for the hydroformylation of olefinically unsaturated hydrocarbons having 4 to 12 carbon atoms. Suitable olefinically unsaturated compounds are, for example, butene-2, mixtures containing butene-2 and butene-1, octene-3, undecene-3, hexene-2, heptene-3, dimeric butenes, trimerpropylene, technically available olefin mixtures such as Dimersol® or Octol®.

The aldehyde mixtures obtained from the first and second reaction stages are separated off and combined, optionally purified, and further processed. Depending on the subsequent processes, it is also possible to continue to implement the crude aldehyde mixture directly, ie without an additional purification step. A further embodiment of the present invention relates to a process for the preparation of carboxylic acids, alcohols or amines from olefinically unsaturated compounds, the olefinically unsaturated compounds being hydroformylated by the process according to the invention and the aldehydes thus obtained being oxidized to carboxylic acids in a manner known per se, to give alcohols reduced or reductively aminated to amines.

The oxidation of the aldehydes obtained according to the invention from olefinically unsaturated compounds can be carried out in a conventional manner, for example by the oxidation of the aldehydes with atmospheric oxygen or oxygen in accordance with the methods, as described, for example, in Ullmann ^'s Encyclopedia of Industrial Chemistry, δ. , Vol. A5, p. 239, VCH Verlagsgesellschaft, Weinheim, 1986.

The catalytic hydrogenation of the aldehydes obtained from olefinically unsaturated compounds by the process according to the invention to alcohols can be carried out in a manner known per se, for example by the processes of Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, vol. A1, p. 279, VCH publishing company, Weinheim, 1985 or GH Ludwig, Hydrocarbon Processing, March 1993, p.67.

The reductive amination of the aldehydes obtained from olefinically unsaturated compounds by the process according to the invention can be carried out in a manner known per se, for example according to 1985 from Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, vol. A2, S1, VCH Verlagsgesellschaft, Weinheim , Ammonia, primary CrC ₂ o-amines or secondary C ₂ -C ₂ o-amines can be used as starting compounds for the production of amines.

The new process is particularly suitable for the hydroformylation of mixtures containing butene-1 and butene-2, which are used as refinery by-products in the manufacture of automotive fuels and in the manufacture of ethylene by thermal decomposition of higher hydrocarbons inevitably arise in considerable quantities. They are obtained from the C - crack cuts of the pyrolysis product by extraction of the butadiene with a selective solvent and subsequent separation of the isobutene, preferably by conversion to methyl tert-butyl ether. The pyrolysis product freed from butadiene is referred to as raffinate 1. If isobutene is also removed, this is referred to as raffinate II. Instead of extracting the butadiene, it can also be partially hydrogenated to butenes in the C-crack cut. After the isobutene has been separated off, a butene-1 / butene-2 mixture is obtained, which can be converted into n-valeraldehyde with high selectivity by the new process. The first homogeneous hydroformylation stage is operated under conditions in which the butene-1 contained in the butene mixture is converted as far as possible to give n-valeraldehyde while the i-valeraldehyde formation is still largely absent. Depending on the reaction parameters chosen, the butene-1 conversion can be up to 95%, the valeraldehyde obtained after the first stage containing 90% and more n-valeraldehyde, while the rest is i-valeraldehyde. In the first stage, unreacted olefin, which mainly consists of butene-2 and which is often also referred to as raffinate III, is reacted in a homogeneous manner in the second stage in accordance with the new process. Depending on the reaction conditions, the olefin conversions are up to 90%, the resulting aldehyde mixture containing up to 90% by weight of n-valeraldehyde. In general, only a partial conversion of olefin is aimed for in the second stage in order to avoid excessive thermal stress on the reaction mixture and to suppress an increased formation of i-valeraldehyde. Seen over the entire process, the butene conversion is up to 95% with selectivities to n-valeraldehyde of up to 90%.

A further embodiment of the process according to the invention consists in the production of C ₁₀ -carboxylic acids and C-io alcohols from a butene Mixture containing 1 and butene-2, which is converted to Cs-aldehydes by the process according to the invention.

The combined Cs-aldehyde mixture of the first and second hydroformylation stages is first aldolized in a conventional manner in the presence of basic catalysts. A pretreatment of the aldehydes, eg a special cleaning, is not necessary. Alkali carbonates or alkali metal hydroxides, in particular compounds of sodium or potassium and amines, preferably tertiary amines, such as triethylamine, tri-n-propylamine, tri-n-butylamine, are used as catalysts. One works at temperatures from 60 to 160 ° C, in particular 80 to 130 ° C and at normal pressure or at up to about 1 MPa increased pressure. The reaction time is from a few minutes to several hours and is particularly dependent on the type of catalyst and the reaction temperature. Due to its higher reaction rate, mainly n-valeraldehyde aldolizes with itself or with isomeric valeraldehydes to decenals, but condensation of 2-methylbutanal or isoveraldehyde with each other completely disappears into the background. _/

Depending on the hydrogenation conditions chosen, the aldehyde mixture obtained by condensation can either be partially reduced to decanal or completely to decyl alcohol. The partial hydrogenation to the decanal and the subsequent oxidation with air or atmospheric oxygen to the decan carboxylic acid takes place in a known manner, for example analogously to the process for the preparation of 2-, known from Ulimann's Encyclopedia of Industrial Chemistry, 4th edition 1975, volume 9, p. ethylhexanoic. The decan carboxylic acid obtained has a high content of 2-propylheptanoic acid.

For the complete hydrogen addition to the decenal to decyl alcohol, conventional hydrogenation catalysts, such as, for example, catalysts based on nickel, chromium or copper, are used in a manner known per se. customary Liche the hydrogenation temperature is between 100 and 180 ° C and the pressure between 1 and 10 MPa. Due to its high content of 2-propylheptanol, the decyl alcohol mixture obtained after purification by distillation is particularly suitable as an alcohol component in phthalic esters, which are used as plasticizers. Plasticizers based on the decyl alcohol mixture obtained by the process according to the invention are notable for excellent low-temperature properties.

The preparation of phthalic acid is known, for example, from Ullmann, Encyclopä- der der Technische Chemie, 1979, Vol. 18, page 536 ff. It is expedient to react phthalic anhydride with the decyl alcohol mixture in a molar ratio of 1: 2 in one step. The reaction rate can be increased by catalysts and / or by increasing the reaction temperature. In order to shift the equilibrium in the direction of the ester formation, it is necessary to remove the water formed from the reaction mixture.

The invention is explained in more detail in the examples below, but is not restricted to the described embodiments.

Example 1 :

1st stage:

Hydroformylation of raffinate II with a composition of 8.8 vol.% Butanes, 66.2 vol.% 1-butene and 22.2 vol.% Ice and trans 2-butenes with a homogeneous rhodium / TPP catalyst solution

An 11 stainless steel autoclave equipped with a stirrer was fed 130 g / h of raffinate II of the above-mentioned composition and 110 Nl / h of CO / H ₂ mixture consisting of equal parts by volume in such a way that 10 Nl / h of exhaust gas could be removed from the reactor [Nl / h means 1 Liters of exhaust gas in standard condition (20 ° C and 1at) per hour]. At the same time, 165 g of TPP dissolved in 830 g of a mixture of n-valeraldehyde and 2-propylheptenal (weight ratio 2: 1) were passed through the reactor in a circle. 134 ml of rhodium 2-ethylhexanoate in 2-ethylhexanol were placed in the reactor. The hydroformation was carried out continuously over 168 hours. The further reaction parameters as well as conversion and selectivities are shown in Table 1.

Table 1: Raffinate-II hydroformylation with an organic Rh / TPP solution (1st stage)

* Based on 2nd level butenes used:

Reaction of the exhaust gas resulting from the first stage (hereinafter referred to as raffinate III) with a composition of 38.8% by volume of butanes, 3.9% by volume of 1-butene and 57% by volume of ice and trans 2-butenes 2,7- bis (3,3-dimethyl-butyl) -9,9-dimethyl-4,5-bis- (2,7-dimethyl-10-phenoxa-phosphino) xanthene (II) as a diphosphine ligand

An 11 stainless steel autoclave equipped with a stirrer was fed 80 g / h of raffinate III of the above-mentioned composition and 60 Nl / h of CO / H ₂ mixture consisting of equal parts by volume in such a way that 10 Nl / h of waste gas could be removed from the reactor. At the same time, 1000 g of the catalyst solution were circulated through the reactor per hour. The rhodium 2-ethylhexanoate used and 2,7-bis (3,3-dimethylbutyl) - 9,9-dimethyl-4,5-bis- (2,7-dimethyl-10-phenoxa-phosphino) xanthene were previously dissolved in 1000g Texanol® from Eastman and 500g valeraldehyde and placed in the reactor. The hydroformation was also carried out continuously over 168 hours. The further reaction parameters as well as conversion and selectivities are shown in Table 2.

Table 2: Hydroformylation of the reaction offgas of the 1st stage in the presence of the diphosphine (II) (2nd stage)

Based on butenes used

Comparative Example 1

In the first stage, raffinate II was hydroformylated analogously to the first stage of example 1 according to the invention. The resulting exhaust gas with a composition of 38% by volume of butanes, 3.9% by volume of 1-butene and 57% by volume of ice and trans 2-butenes was then batch-processed in the second stage under unmodified high-pressure conditions at 250 bar and hydroformylated at 160 ° C. Rhodium 2-ethylhexanoate served as the rhodium source and was pumped into the system as a concentrated solution (rhodium content approx. 5000 ppm in 2-ethylhexanol). The concentration of rhodium, based on the olefin used, was 5 ppm. The reaction was run until complete conversion and the resulting aldehyde worked up by distillation. With a conversion of 98%, a C ₅ - aldehyde mixture with an n: i ratio of 45:55 resulted.

The combination of the hydroformylation products from Comparative Example 1 gave a pentanal mixture with an n: i ratio of 76:24.

As the comparison of the results of the process according to the invention with the results of the comparative examples proves, a butene-II mixture can be converted to the straight-chain aldehydes by the two-stage procedure according to the invention with a significantly higher selectivity than by the known procedure in which the second stage works under the known unmodified process under high pressure. The diphosphines used according to the invention are also characterized by a long catalyst life.

Claims

claims

1. A process for the hydroformylation of olefinically unsaturated compounds, the reaction in a first reaction stage in a homogeneous reaction system using organic phosphorus (III) compounds in complex bonds containing rhodium compounds as catalysts at pressures of 0.2 to 20.0 MPa and exhaust gas is formed, characterized in that the exhaust gas is fed to the first reaction stage of a second reaction stage, in which amounts of the olefinically unsaturated compounds present in the exhaust gas in a homogeneous reaction system in the presence of complex compounds of rhodium and diphosphines of the general formula (I)

(I)

in which R ¹ and R ^{2 are} each the same or different (CrCι ₈ ) alkyl radicals, (C ₆ - C ₁₄ ) aryl radicals, (C ₇ -C ₂₄ ) aralkyl radicals or (C ₇ -C ₂₄ ) Alkylaryl radicals, R ^{3 represents} hydrogen or a radical -CHR ^a R ^b , in which R ^a and R ^{b are} each identical or different hydrogen, (Ci-CisJ-alkyl, (-C-C ₈ ) alkoxy radicals, unsubstituted or with (Cι -C ₁₀ ) alkyl and / or (-C-Cι ₀ ) alkoxy radicals are substituted (C ₆ -Cι ₄ ) aryl radicals or (C -C ₂ ) aralkyl radicals, and R ⁴ (Ci - Cιo) alkyl residues, (C ₆ -C ₄ ) aryl residues, (C ₇ -C ₂₄ ) aralkyl residues or (C ₇ -C ₂₄ ) - alkylaryl residues, at pressures of 0, 2 to 20 MPa can be implemented.

2. The method according to claim 1, characterized in that in the general formula IR ¹ and R ^{2 in} each case the same or different (-C 1 -C ₂ ) alkyl radicals, (C ₆ -CIO) aryl radicals (C _7th Are -C ₁₀ ) aralkyl radicals or (C ₇ -C ₁₀ ) alkylaryl radicals,

R ^{3 represents} hydrogen or a radical -CHR ^a R ^b , in which R ^a and R ^{b are} each identical or different hydrogen, (-Cι-Cι ₂ ) -alkyl, (CrC ₄ ) -alkoxy radicals, unsubstituted or with (Cι -C ₃ ) alkyl and / or (CrC ₄ ) alkoxy radicals are substituted (C6-Cιo) aryl radicals or (C ₇ -Cι ₀ ) aralkyl radicals, and R ⁴ (Ci-C ₃ ) Alkyl radicals, (C ₆ -C ₁₀ ) aryl radicals, (C ₇ -Cιo) aralkyl radicals or (C ₇ -Cι ₀ ) - alkylaryl radicals.

3. The method according to claim 1 or 2, characterized in that the aryl radical is in each case the phenyl or the naphthyl radical and the aralkyl radical is the benzyl radical.

4. The method according to one or more of claims 1 to 3, characterized in that R ¹ and R ^{2 are the} same or different and methyl, ethyl,

Propyl, i-propyl, n-butyl, i-butyl, tertiary butyl, n-pentyl, i-pentyl, n-hexyl, i-

Hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl,

Phenyl, naphthyl, tolyl or benzyl mean that

R ³ for methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, n-pentyl, i-pentyl, 3,3-dimethylbutyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl , n-octyl, i-octyl, n-nonyl, i-

Nonyl, n-decyl, i-decyl, phenyl, naphthyl, tolyl or benzyl and that R ^{4 is} methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, tertiary butyl, n-pentyl, i-pentyl, 3,3-dimethylbutyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, phenyl, naphthyl, tolyl or benzyl.

5. The method according to any one of claims 1 or 2, characterized in that the diphosphines 2,7-bis (3,3-dimethylbutyl) -9.9-dimethyl-4,5-bis (2,7-dimethyl-10- phenoxaphosphino) xanthene (II), 2,7,9-trimethyl-9-n-nonyl-4,5- bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (III), 2,7-di-n- decyl-9,9-dimethyl-4,5-bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (IV), 2,7-di-n-hexyl-9,9-dimethyl-4,5 -bis (2,7-dimethyl-10-phenoxaphosphino) xanthene (V), 2,7- (3,3-dimethylbutyl) -9,9-dimethyl-4,5-bis [2,7-di (3, 3-dimethylbutyl) -10-phenoxaphosphino] xanthene (VI), 2,7-dimethyl-9,9-dimethyl-4,5-bis [2,7-di (3,3-dimethylbutyl) -10-phenoxaphosphino] xanthene (VII) used.

IV

10 V

VI

VII

6. The method according to one or more of claims 1 to 5, characterized in that the hydroformylation in the first reaction stage at temperatures of 50 to 160 ° C and a rhodium concentration of 1 to 1000 ppm by weight, based on the homogeneous reaction mixture and the molar ratio of rhodium to phosphorus in the homogeneous reaction mixture is 1: 1 to 1: 1000.

7. The method according to one or more of claims 1 to 6, characterized in that the pressure in the first reaction stage is 1 to 12 MPa, preferably 1 to 7 MPa.

8. The method according to one or more of claims 1 to 7, characterized in that the temperature in the first reaction stage is 60 to 150 ° C and in particular 75 to 140 ° C.

9. The method according to one or more of claims 1 to 8, characterized in that the concentration of rhodium in the homogeneous reaction mixture is 10 to 700 ppm by weight and in particular 25 to 500 ppm by weight.

10. The method according to one or more of claims 1 to 9, characterized in that the molar ratio of rhodium to phosphorus in the homogeneous reaction mixture is 1: 3 to 1: 500, preferably 1:50 to 1: 300.

11. The method according to one or more of claims 1 to 10, characterized in that aliphatic, arornatic or mixed aliphatic-aromatic phosphines, diphosphines or phosphites are used as organic phosphorus (III) compounds.

12. The method according to one or more of claims 1 to 11, characterized in that the hydroformyation reaction in the second reaction stage at temperatures of 50 to 160 ° C and a rhodium concentration of 1 to 1000 ppm by weight, based on the homogeneous reaction mix, carried out and the molar ratio of rhodium to phosphorus in the reaction mixture is 1: 1 to 1:80.

13. The method according to one or more of claims 1 to 12, characterized in that the pressure in the second reaction stage is 1 to 12 MPa, in particular 1 to 5 MPa.

14. The method according to one or more of claims 1 to 13, characterized in that the temperature in the second reaction stage is 60 to 150 ° C and in particular 75 to 140 ° C.

15. The method according to one or more of claims 1 to 14, characterized in that the rhodium concentration in the second reaction stage is 50 to 500 ppm by weight and in particular 100 to 300 ppm by weight, based on the homogeneous reaction mixture.

16. The method according to one or more of claims 1 to 15, characterized in that in the second reaction stage the molar ratio of rhodium to phosphorus in the reaction mixture is 1: 1 to 1:20.

17. The method according to one or more of claims 1 to 16, characterized in that one carries out the first and second hydroformylation stage in a solvent, the solvent used being paraffin oil, aromatic hydrocarbons, ethers, aldehydes, ketones or higher-boiling condensation products of aldehydes, in particular Trimers of aldehydes used.

18. The method according to one or more of claims 1 to 17, characterized in that one uses as olefinically unsaturated compounds olefinically unsaturated compounds with internal double bonds or mixtures containing olefinically unsaturated compounds with internal double bonds.

19. The method according to claim 18, characterized in that one uses olefinically unsaturated compounds having 4 to 12 carbon atoms.

20. The method according to claim 19, characterized in that the olefinically unsaturated compound is a mixture containing butene-1 and butene-2.

21. A process for the preparation of carboxylic acids from olefinically unsaturated compounds, characterized in that the olefinically unsaturated compound according to one or more of claims 1 to 20 is hydroformylated, the aldehyde mixtures obtained are separated from the hydroformylation stages and combined and subsequently in a manner known per se to give carboxylic acids oxidized.

22. A process for the preparation of alcohols from olefinically unsaturated compounds, characterized in that the olefinically unsaturated compound is hydroformylated according to one or more of claims 1 to 20, the aldehyde mixtures obtained are separated from the hydroformylation stages and combined and subsequently in a manner known per se to give the alcohol reduced or hydrated.

23. A process for the preparation of amines from olefinically unsaturated compounds, characterized in that the olefinically unsaturated compound according to one or more of claims 1 to 20 is hydroformylated, the aldehyde mixtures obtained are separated from the hydroformylation stages and combined and subsequently in the presence of an amination catalyst and Hydrogenated with ammonia, a primary or secondary amine in a manner known per se.

24. A process for the preparation of mixtures of isomeric decyl alcohols from mixtures containing butene-1 and butene-2, characterized in that the mixture containing butene-1 and butene-2 is hydroformylated according to one or more of claims 1 to 17, the aldehyde mixtures obtained the hydroformylation stages are separated and combined, the combined aldehyde mixtures are condensed to form an aldol mixture, the aldol mixture is separated off and hydrogenated to a mixture of isomeric decyl alcohols.

25. A process for the preparation of didecyl phthalate from mixtures containing butene-1 and butene-2, characterized in that the mixture containing butene-1 and butene-2 is hydroformylated according to one or more of claims 1 to 17, the aldehyde mixtures obtained from the hydroformylation stages separated and combined, the combined aldehyde mixtures condensed to form an aldol mixture, the aldol mixture is separated and hydrogenated to a mixture of isomeric decyl alcohols and the mixture of isomeric decyl alcohols is esterified with phthalic acid or phthalic anhydride.

26. A process for the preparation of mixtures of isomeric decane carboxylic acids from mixtures containing butene-1 and butene-2, characterized in that the mixture containing butene-1 and butene-2 is hydroformylated according to one or more of claims 1 to 17, the aldehyde mixtures obtained separated and combined from the hydroformylation stages, the combined aldehyde mixtures condensed to form an aldol mixture, the aldol mixture separated, partially hydrogenated to a mixture of isomeric decanals and then oxidized to a mixture of isomeric decanecarboxylic acids.