EP2456745A2

EP2456745A2 - Method for the production of decanecarboxylic acids

Info

Publication number: EP2456745A2
Application number: EP10722067A
Authority: EP
Inventors: Michael Grass; Alfred Kaizik; Hans-Gerd Lüken; Wilfried Büschken
Original assignee: Evonik Oxeno GmbH and Co KG
Current assignee: Evonik Operations GmbH
Priority date: 2009-07-23
Filing date: 2010-05-25
Publication date: 2012-05-30
Also published as: US20120172624A1; WO2011009657A2; US8907129B2; ZA201201237B; WO2011009657A3; DE102009027978A1; KR20120038514A; CA2768604A1; SG178071A1; JP5787886B2; MX2012000840A; JP2012533589A; CN102548946A; BR112012001274A2; TW201125845A

Abstract

The invention relates to a method for producing a mixture of isomeric decanecarboxylic acids, in which the following steps are carried out: a) hydroformylation of a hydrocarbon mixture containing linear C4 olefins using a catalyst system that contains rhodium; b) aldol condensation of a mixture of aliphatic C5 aldehydes obtained in step a); c) selective hydrogenation of the mixture of unsaturated C10 aldehydes from step b) to obtain aliphatic C10 aldehydes; d) uncatalyzed oxidation of the mixture of aliphatic C10 aldehydes from step c) to obtain a mixture containing at least 70 percent by weight of 2-propyl heptanoic acid relative to the total amount of isomeric decanecarboxylic acids.

Description

Process for the preparation of decanecarboxylic acids

The present invention relates to the preparation of decanecarboxylic acids, in particular of decanecarboxylic acid mixtures with a high proportion of 2-propylheptanoic acid.

Decanecarboxylic acids can be used, for example, as a precursor for the preparation of peresters, detergents and lubricants. In the patents DE 101 08 474, DE 101 08 475, DE 101 08 476 and DE 102 25 282, the preparation of Pentanalgemischen by

Hydroformylation of a mixture of linear butenes described. All

Patenschriften have in common that in at least one

Hydroformylation step, a rhodium catalyst having a diphosphine ligand having a xanthene skeleton is used. With this catalyst, 2-butenes can be hydroformylated under isomeric conditions. The ratio of n-pentanal to 2-methylbutanal is 85 to 15. DE 101 08 474 and DE 101 08 475 disclose processes in which the

Hydroformylation is carried out in two stages. In the first hydroformylation step, using a catalyst consisting of rhodium and a

Monophosphine as ligand, 1-butene converted in a selectivity of 95% to n-pentanal. The unreacted butenes, mainly 2-butenes, are used in the second hydroformylation step using the above

Rhodium / bisphosphine reacted. The writings DE 101 08 476 and

DE 102 25 282 claim one-step hydroformylation processes. As the use of n-pentanal / 2-methylbutanal mixture u in all four patents. a. the preparation of a mixture of isomers

Decancarboxylic claimed. A synthesis pathway is sketched, which comprises the following steps: Aldol condensation of the pentanal mixture to form a

Decenal mixture, selective hydrogenation of the decene mixture to one

Decanal mixture and its oxidation to a mixture of isomeric

Decancarbonsäuren. Neither the feasibility of this synthesis nor a Execution type is occupied. It is merely referred to that they could be carried out in analogy to the preparation of 2-ethylhexanoic acid from butyraldehyde, in particular the following two references are given. The first place is Ullmann's Encyclopaedia of Industrial Chemistry, 5th Edition,

Volume A1, p. 330. Herein it is stated in one sentence how 2-ethylhexenal can be hydrogenated to 2-ethylhexanal. No reaction conditions are mentioned. There are also no references to literature. The second place is Ullmanns

Encyclopedia of Industrial Chemistry, 4th Edition 1975, Volume 9, page 144. Herein, without disclosing details, 2-ethylhexanoic acid can be prepared by oxidation of 2-ethylhexanal, with additions of

Alkali metal salts of 2-ethylhexanoic acid increase the yields.

Bibliography is also missing. DE 101 08 476 states that the

Depending on the choice of reaction conditions, condensation mixture (decenal) can either be partially hydrogenated to give decanalen in the presence of palladium-containing catalysts or completely to give decanols. Descriptions of

Catalyst and information on Reaktionsbedingunen and reaction execution missing.

Thus, no method for the production of decanecarboxylic acids is so completely disclosed that it is more complicated by a skilled person without implementation

Experiments can be exercised.

The present invention had the object of specifying a method based on a linear C4-olefin-containing hydrocarbon mixture, which additionally contains isobutene, provides decanals in a few steps, which are oxidized with oxygen-containing gases in high yields to the corresponding decanecarboxylic acids, without that neither a

Catalyst still stabilizing additives find use. The invention therefore provides a process for the preparation of a

A mixture of isomeric decanecarboxylic acids, the following steps being carried out: ά a) hydroformylation of a hydrocarbon mixture containing linear C4 olefins using a rhodium-containing catalyst system; b) aldol condensation of a mixture of C5 aliphatic aldehydes,

obtained from step a);

c) Selective hydrogenation of the mixture of unsaturated C10-aldehydes

Step b) to C10 aliphatic aldehydes;

d) uncatalyzed oxidation of the mixture of aliphatic C10 aldehydes

Step c)

obtaining a mixture containing at least 70% by mass

2-propylheptanoic acid based on the total content of the isomers

Decancarbonsäuren.

The process according to the invention has the following advantages: The oxidation is very selective even at very high conversions, so that only small losses of substance occur. Accordingly, even small amounts of by-products, which must be disposed of. Since no catalyst is used, there are no costs for catalyst, separation of the used catalyst or its derivatives and their disposal. In the present invention, the decanal mixture, which has been prepared starting from linear butenes in a three-stage synthesis and based on the Decanalanteil contains at least 80% by mass of 2-propylheptanal, oxidized to the corresponding Decancarbonsäuren. According to the invention, the oxidation is carried out neither with the addition of a catalyst, usually a transition metal compound, nor with the addition of a stabilizer, for example an alkali metal or alkaline earth metal salt of a carboxylic acid.

As the oxidizing agent, oxygen, air or other oxygen-containing gas mixtures can be used. Preferably, oxygen or oxygen / nitrogen mixtures with more than 10% by volume of oxygen are used in the process according to the invention. The oxidation is carried out in the temperature range from 10 to 80 ^° C., in particular in the temperature range from 20 to 50 ^° C., very particularly in the temperature range from 25 to 35 ^° C. The absolute reaction pressure, measured in the gas phase at the top of the reactor, is 0.1 to 1 MPa, in particular 0.1 to 0.5 MPa.

The oxidation is carried out in the liquid / gas mixed phase. The

Decanal mixture and / or the resulting Decancarbonsäuregemisch is present as a continuous liquid phase, in which the oxidizing gas or gas mixture is introduced. Most of the gas mixture is present as a disperse phase.

Reactors which may be used are stirred tanks or bubble column reactors, into which gas is introduced near the bottom by means of a gas distribution device, for example a frit or a nozzle.

In order to avoid the formation of an explosive mixture, so much nitrogen is introduced into the gas space above the liquid level that the content of oxygen in the gas space (exhaust gas) does not exceed 6% by volume.

The oxidation may be carried out continuously or batchwise in one or more reactors. When using multiple reactors, these may be connected in series and / or in parallel.

In batchwise operation, a conversion of aldehydes of 60 to 98%, in particular from 85 to 95% is desired.

In continuous operation, a conversion of aldehydes of 50 to 95%, in particular one of 70 to 90% is desired. Ö

After the oxidation, the reaction mixture consists of decanecarboxylic acids with a content of 2-propylheptanoic acid of at least 70% by mass, unreacted Cio aldehydes, by-products and optionally of substances which were already present in the feed decanal. The content of decanecarboxylic acids in this mixture is in the range of 50 to 98% by mass, in particular in the range of 80 to 93% by mass.

This mixture is preferably separated by distillation. The distillative

Separation can be done at atmospheric pressure or reduced pressure. Preferably, the distillative separation is carried out in vacuo.

The oxidation mixture is preferably separated into the following four fractions: a) A low-boiling fraction which is essentially oxidized

resulting degradation products contains

b) an aldehyde fraction consisting mainly of decanals

c) a product fraction containing virtually only decanecarboxylic acids d) a high boiler fraction

Preferably, the distillative separation is continuous or

carried out semicontinuously in three columns connected in series. In the first column, the low boilers are separated in the second column, the aldehydes and in the third column, the decanecarboxylic acids in each case as the top product. The bottom product of the third column is the high boilers. The separated low boilers and high boilers can be used thermally or used as starting material for a synthesis gas plant. If the high boiler fraction contains a large amount of decanecarboxylic acid ester, it can optionally be worked up to decanecarboxylic acids. The separated aldehyde fraction can be completely or partially recycled to the oxidation state. b

The decanecarboxylic acids obtained can be used, for example, for the production of peresters, siccatives, detergents, plasticizers or lubricants. Starting materials for the process according to the invention are

Hydrocarbon mixtures which have no polyunsaturated compounds and no acetylene compounds and contain at least one of the olefins cis-2-butene, trans-2-butene and 1-butene. In addition, in the

Starting materials up to 5% by mass, in particular up to 1% by mass, very particularly up to 0.2% by mass of isobutene, in each case based on the

C ₄ -Ol efinfraktion, be present.

Technical mixtures containing linear C ₄ olefins are

Refined petroleum fractions from refineries, C ₄ fractions from FC or

Steam crackers, mixtures of Fischer-Tropsch syntheses, mixtures of dehydration of butanes, mixtures formed by metathesis, or mixtures of other technical processes.

For example, suitable mixtures of linear butenes can be obtained from the C ₄ fraction of a steam cracker for the process according to the invention. In the process, butadiene is removed in the first step. This is done either by extraction or extraction distillation of butadiene or its

Selective hydrogenation. In both cases, a virtually butadiene-free C _{4 cut is} obtained, the raffinate I. In the second step isobutene is removed from the C ₄ stream, z. B. by preparation of methyl tert-butyl ether (MTBE) by

Reaction with methanol or preparation of ethyl tert-butyl ether by

Reaction with ethanol. Other possibilities are the conversion of the isobutene from the raffinate I with water to tert-butanol or the acid-catalyzed

Oligomerization of isobutene to diisobutene. The now isobutene-free C _{4 cut} , the raffinate II, contains, as desired, the linear butenes and optionally butanes. Optionally, the 1-butene can be removed by distillation. Both Fractions containing but-1-ene or but-2-ene can be used in the process of the present invention.

Another possibility for producing a suitable educt is raffinate I, raffinate II or a similar composition

To Hydroisomehsieren hydrocarbon mixture in a reactive column. In this case, inter alia, a mixture can be obtained which consists of 2-butenes, small amounts of 1-butene and optionally n-butane and isobutane and isobutene. Another feed mixture for the process according to the invention is the C ₄ mixture remaining from the oligomerization of a mixture of linear olefins (for example raffinate II or raffinate III), butane, optionally from isobutene, 2-butenes and small amounts of 1-butene consists. Preference is given to using hydrocarbon mixtures with preferably at least 15% by mass of linear butenes.

The first step of the process according to the invention is hydroformylation. In order to obtain a content of 2-propylheptanoic acid of more than 80% in the end product, it is necessary that in the hydroformylation of linear butenes n-pentanal is produced in a selectivity greater than 85%. If only 1-butene is to be converted, this can be done, for example, with the aid of a catalyst system consisting of rhodium and a monophosphine, for example triphenylphosphine. If also 2-butenes are to be implemented, the

Hydroformylation be carried out under isomerizing conditions. That is, a catalyst is used which under reaction conditions is able to shift both the double bonds in all linear butenes, i. H. to isomerize, as well as hydroformylate terminally. There are catalysts used, the linear butenes with any ratios of isomers with an n-selectivity (ratio of n-pentanal to sum of all

C ₅ aldehydes) greater than 85% to pentanals implement. As a catalyst for example, in the patents DE 101 08 474, DE 101 08 476, ö

DE 101 08 476 and DE 102 25 282 described bisphosphines can be used. Likewise, rhodium catalysts with bulky

aromatic bisphosphites are used as ligands, as described, for example, in EP 0 213 639.

The second reaction step of the process according to the invention is the

Aldol condensation of C ₅ aldehydes to decenals. The reaction product of the first stage consists after separation of the unreacted hydrocarbons from n-pentanal (valeraldehyde), 2-methylbutanal and small amounts of n-pentanol and 2-methylbutanol. If the feed hydrocarbon mixture contains isobutene, the first stage reaction mixture contains 3-methylbutanal. The aldehyde fraction contains at least 85% by mass of n-pentanal, less than

15% by mass of 2-methylbutanal and less than 5% by mass of 3-methylbutanal, in particular less than 1% by mass, especially less than 0.2% by mass of 3-methylbutanal. A process for the preparation of n-pentanal riches

C5-aldehyde mixtures of mixtures rich in linear C4 olefins is described in DE 102008 002187.3. Becomes a specific one

Isomer composition in Aldolisierungsprodukt desired, it can be obtained for example via a distillation step upstream of the aldolization. In the distillation, n-valeraldehyde and 2-methylbutanal are separated according to the desired composition. If necessary, it can also be distilled sharper and the composition through

subsequent remixing of one of the components can be adjusted. As the catalyst, hydroxides, bicarbonates, carbonates, carboxylates or their mixtures in the form of their alkali metal or alkaline earth metal compounds or tertiary amines can be used in each case as aqueous solutions. As aqueous catalyst solutions, alkali metal alkalis such as, for example, are preferred

Caustic soda is used.

The concentration of the basic catalyst in the aqueous catalyst solution is generally between 0.1 and 10% by mass, in particular between 0.1 and y

3 mass%. Since water is formed during the reaction, the concentration of the catalyst solution in the reactor feed is higher than in the reactor effluent. Due to the as a side reaction proceeding Cannizzaro reaction arise from the starting material and to a lesser extent from the product alcohols and carboxylic acids which accumulate in the catalyst phase in the form of their salts. By discharging a portion of the catalyst solution and replacing it with an equivalent amount of fresh liquor, the concentration of the carboxylic acid salts in the aqueous catalyst solution can be maintained between 5 and 40 mass%. The proportion of the aqueous catalyst solution based on the organic

Educt phase can vary within wide limits. If a tubular reactor is used in the process according to the invention, mass ratios of organic to catalyst phase of at least 1 to 2, preferably greater than 1 to 10, are suitable. The same applies to the use of stirred tanks.

In the specific embodiments of the present invention, the

Concentration of the catalyst solution by Ausschleusungs- or

Control measures. The temperature of the reaction mixture at the reactor outlet is suitably above the boiling point of the aqueous catalyst solution between 80 ⁰ C and 180 ⁰ C, in particular between 120 and 150 ⁰ C. When using a

Rührkessels this corresponds to the temperature of the reaction mixture. in the

Flow tube or tubular reactor is reached at adiabatic reaction this temperature only at the reactor end.

The pressure in the reaction device is due to the vapor pressures of the components in the reaction mixture at the appropriate temperatures. The aldol condensation according to the invention is preferably carried out between 0.1 and 2.0 MPa, more preferably between 0.2 and 0.5 MPa. IU

The reaction apparatus of the aldol condensation can be at least one stirred tank or a stirred tank cascade or at least one tubular reactor or

Be flow tube. In each type of reactor, intensive mixing of the two phases can be provided by means of agitators or static mixers.

In the process according to the invention, the aldol condensation of the C ₅ -aldehydes is preferably carried out in a tube reactor filled with static mixers, as described, for example, in DE 10 2009 001594.9.

The reaction mixture leaving the reaction mixture is separated into the catalyst phase and the organic product phase.

Preferably, the reaction and work up as in

DE 199 56 410.

The reaction mixture leaving the reactor is poured into a

Short-distillation apparatus relaxed, preferably at atmospheric pressure. With high-boiling starting materials, it is possible to relax in a slight vacuum (0.01 to 0.1 MPa).

The short distillation can be flash distillation, as distillation in a

Falling film evaporator, be carried out as a distillation in a thin-film evaporator or as a distillation in a combined falling film / thin film evaporator. The flash distillation described below represents the preferred because technically simplest variant dar. The short distillation is the

Reaction product of the lowest possible thermal and chemical

Exposure to the catalyst and is therefore preferred with

Residence times of a maximum of one minute carried out. Comparable distillations have residence times of over 5 minutes. The short distillation, especially the flash is preferably made adiabatic, thereby the

Temperature of the bottom product lower than that of the inlet. n

The reaction product is largely in a

Overhead product comprising water and C ₅ aldehydes, and a bottom product comprising aldol condensation products, mainly decenals, and aqueous catalyst phase, separated.

In addition to the already mentioned mixture of water and educt, the top product optionally contains other low boilers (eg pentanols) and small amounts of α, β-unsaturated aldehydes (decenals). The bottom product contains, in addition to the mixture of decenals and catalyst phase, optionally higher condensation products, products from the Cannizarro reaction of the starting materials and small amounts of starting materials.

The preferably uncooled bottoms product from the short distillation can in a settling tank into an organic phase (product phase) and an aqueous phase, d. H. the aqueous catalyst phase are separated.

The organic product phase, after leaching of traces of catalyst with water, preferably using the aqueous phase of

Top product of the short distillation, removed from the process. This

Crude product can be used directly for further in the third reaction stage, namely the selective hydrogenation. Optionally, high boilers (higher aldol addition and aldol condensation products) can additionally be separated off and at least partially returned to the condensation reactor. The aqueous catalyst phase is, if appropriate, together with the resulting wash water, returned to the aldol condensation reaction. From the catalyst phase can be discharged to keep the by-product level constant a small part and by an equivalent amount of

Fresh catalyst to be replaced.

The overhead product of the short distillation is at a temperature which is below the boiling point of the water as well as below a minimum azeotrope, condensed. The result is a liquid mixture which can be separated into an organic phase and an aqueous phase.

The organic phase of the top product is optionally pumped back into the aldol condensation reactor, optionally a part is discharged.

A portion of the aqueous lower phase may, for. B. for the washing of the product phase, as already mentioned above, are used. The other part of the aqueous phase of the top product or the entire aqueous phase is used to discharge the water of reaction. In the aqueous phase, organic substances, especially educt, are still dissolved. The wastewater can be added directly to the sewage treatment plant or after pre-treatment. The pre-cleaning can be carried out by steam stripping or by azeotropic distillation of organic substances.

In the condensation of n-pentanal arises as the primary

Aldol condensation product 2-propylheptalene. If 2-methylbutanal is present in C ₅ -aldehyde, 2-propyl-4-methylhex-2-enal is formed by crossed aldol condensation. If 3-methylbutanal in the C ₅ aldehyde mixture is also present, the following unsaturated aldehydes can be formed as further primary aldol condensation products: 2-isopropyl-5-methylhex-2-enal, isopropyl 4-methylhex-2-enal, 2-propyl 5-methylhex-2-enal and 2-isopropyl-hept-2-enal. According to the invention, the proportion of 2-propylhept-2-enal based on the sum of all decenals is more than 90% by mass.

The crude aldol condensation product, which in addition to the decenals mainly contains higher aldol condensates, can be purified before the next step, for example by distillation. Preference is given to using crude decene mixtures in the third stage, selective hydrogenation. Υό

For selective hydrogenation, in which only the olefinic double bond is hydrogenated in decenal, catalysts are used, which may contain palladium, platinum, rhodium and / or nickel as hydrogenation-active component. The metals can be used in pure form, as compounds with oxygen or as alloys. Preferred catalysts are those in which the hydrogenation-active metal is supported on a support. Suitable carrier materials are

Alumina, magnesia, silica, titania and their mixed oxides, and activated carbon. Of these catalysts, particularly preferred

Catalysts palladium on activated carbon and palladium on alumina.

For contacts, which consist of palladium and a carrier, the

Palladium content 0.1 to 5 mass%, preferably 0.2 to 1 mass%.

Particular preference is given to using a catalyst consisting of aluminum oxide, preferably γ-aluminum oxide with a Pd content of 0.3 to 0.7% by mass. The catalyst may optionally contain moderating substances,

For example, alkali components such as sodium compounds in concentrations up to 3% by mass.

The hydrogenation can be carried out continuously or discontinuously and both in the gas phase and in the liquid phase. Hydrogenation in the liquid phase is preferred because the gas phase process requires more energy because of the necessary circulation of large volumes of gas. For continuous liquid phase hydrogenation can

different process variants are selected. It can be performed adiabatically or practically isothermally, ie, with a temperature increase of less than 10 ⁰ C, one or more stages. In the latter case, the reactors may be adiabatic or practically isothermal, or some adiabatic, and the others practically isothermal. Furthermore, it is possible to carry out the selective hydrogenation in a straight pass or with product recirculation. The hydrogenation is in the liquid / gas mixed phase or in the liquid phase in

Three-phase reactors carried out in cocurrent, wherein the hydrogen is dispersed in a known manner in the liquid to be hydrogenated. in the

Interest in a uniform liquid distribution, an improved Reaction heat removal and a high space-time yield at high

Selectivity, the reactors are preferably high

Liquid loads of 15 to 300, in particular from 25 to 150 m ³ per m ² cross-section of the empty reactor and hour operated. A hydrogenation process for the production of decanals is, for example, the liquid-phase hydrogenation in two or more reactors, all of which are product-recycle, as described in US 5,831,135.

When palladium catalysts are used, for example 0.5% by mass of alumina, selective hydrogenation of 2-propylheptenal is added

2-Propylheptanal preferably at temperatures between 120 and 180 ⁰ C, in particular between 140 and 160 ⁰ C and a pressure of 1, 5 to 5 MPa, in particular at 2 to 3 MPa performed. In addition to decenals, the hydrogenation product contains small amounts of decanols formed by overhydrogenation, small amounts of C ₅ aldehydes and C ₅ alcohols and high boilers, mainly higher ones

Aldol condensation products and their hydrogenation products. The content of 2-propylheptanal therein is in excess of the decanal fraction

20 85% by mass.

From the crude Hydheraustrag can be separated before the next reaction step, the oxidation, high boilers and / or low boilers. Preferably, a distillative workup is omitted.

25

The oxidation of the decanal mixture to the corresponding mixture of isomeric carboxylic acids can in principle be carried out in a manner known per se. When

Oxidizing agents can be used oxygen, air or other oxygen-containing gas mixtures. The oxidation can be carried out uncatalyzed or catalyzed. In the latter case, transition metal compounds, especially cobalt and manganese compounds, are used as the catalyst. The oxidation can be carried out at atmospheric pressure or elevated pressure become. The process of the invention, the oxidation is carried out without a catalyst and without further stabilizing additives. The following examples are intended to illustrate the invention.

5 examples

Preparation of 2-propylheptanal (starting material for aldehyde oxidation)

Starting from a mixture of linear C4 olefins was first a

Mixture made with a high content of n-pentanal. Subsequently, lo n-pentanal (n-valeraldehyde) and others, with resulting aliphatic

C5-aldehydes converted by Aldolkondensation in the α, ß-unsaturated Cio-aldehydes in a proportion of at least 80% by mass of 2-Propylheptenal, based on the total amount of Aldolkondensationsprodukten. Subsequently, 2-propylheptenal was converted by selective hydrogenation to the desired product i5 2-propylheptanal.

hydroformylation:

A process for the preparation of n-pentanal-rich C5-aldehyde mixtures from a mixture containing linear C4-olefins is described in DE 10 2008 002187.3 20, which serves as a basis.

aldolization:

In a continuous pilot plant consisting of a tubular reactor filled with static mixing elements from Sulzer (diameter 20 mm,

25 4000 mm in length) was n-valeraldehyde at a rate of 8 l / h in

Presence of an aqueous 2% sodium hydroxide solution as catalyst (flow rate of 80 l / h) at 130 ⁰ C and 0.3 MPa to 2-Propylheptenal implemented. After leaving the reactor, the aqueous catalyst phase was separated in a 5 I separation vessel at 80 ⁰ C from the aldehyde phase and by means of a

30 circulation pump led back into the reactor. The separated organic phase was collected in a 100 liter stainless steel container. The crude product output from the n-valeraldehyde aldolization has the following composition in mass%, according to a GC analysis: 4.93%

n-Valeraldehyde, 0.47% 2-methylbutanol, 0.30% pentanol, 0.51% 2-propyl-4-methyl-hexenal, 91, 81% 2-propylheptenal, and 1.98% residue.

selective:

The discharge of aldolization with crude 2-propylheptenal was in a

Circuit apparatus selectively hydrogenated in the liquid phase on the palladium catalyst H 14535 (0.5% Pd on alumina), obtained from the company. Degussa, at 160 ⁰ C and 2.5 MPa to 2-propylheptanal. For this purpose, 200 ml / h starting material continuously over 400 ml of catalyst, corresponding to a catalyst loading of 0.5 h ^"1 , passed.

The following typical composition in masses. % of the hydrogenation product was determined by GC: 2.80% n-valeraldehyde, 0.15% 2-methylbutanol, 2.14% n-pentanol, 1.09% nonane, 0.12% nonanone, 86.65% 2-propylheptanal, 0.68% 2-propylheptenal, 4.27% 2-propylheptanol and 2.1% high boiler.

example 1

Preparation of 2-propylheptanoic acid / comparative example

The preparation of 2-propylheptanoic acid by liquid phase oxidation of 2-propylheptanal was carried out in a heatable 6 l jacketed stirred tank. As starting material, the hydrogenation product from the previously described

Selective hydrogenation with approx. 86.7 mass% used 2-propylheptanal.

For a reaction batch, 5050 g of liquid educt were initially charged in the reactor. As a reaction gas, a nitrogen-oxygen mixture was used, which was evenly distributed in the lower part of the reactor via a frit into the liquid. In the reactor were a constant nitrogen flow of 30 Nl / h and depending on the consumption by the reaction via an online measurement of the

Oxygen content in the exhaust regulated oxygen flow metered. In the gas space of the reactor in the upper part of the reactor, a constant nitrogen flow of 330 Nl / h was metered. A maximum oxygen content in the exhaust gas of 6% by volume was permitted. The oxidation of the Cio-aldehyde mixture was at M

Reaction temperatures of 50 and 70 ⁰ C and a reaction pressure of 0.3 MPa performed. The progress of the oxidation was through a regular

Sampling and subsequent GC analysis determined.

Under the chosen reaction conditions after 4.5 hours

Obtained raw products whose composition is listed in Table 1, Column 2 and Column 3.

Table 1 Product Composition / Comparative Example

As can be seen from Table 1, the 2-Propylheptanal was almost completely reacted at a reaction temperature of 70 ⁰ C. In addition to the desired value product 2-propylheptanoic acid were at this temperature, a number of by-products, such as the Cg paraffin nonane, the Cg ketone

Nonanon. and the Cg alcohols. The formation of by-products led to a strong reduction in selectivity. By lowering the reaction temperature to 50 ^° C., the selectivity of 2-propylheptanoic acid formation could be improved, but at a significantly lower conversion. 1 ö

Example 2

Preparation of 2-propylheptanoic acid / Inventive According to the experimental procedure described in Example 1, 5100 g of educt with approx. 86.6% by mass of 2-propylheptanal in inventive

Reaction temperatures of 25 and 35 ⁰ C, a reaction pressure of 0.3 MPa and 6 vol .-% oxygen content in the exhaust gas in the liquid phase to

2-Propylheptanoic acid oxidized

Under the chosen reaction conditions, crude products were obtained after 6 hours of trial time, the composition of which is listed in Table 2, column 2 and column 3.

Table 2 Product Composition

As can be seen from Table 2, the selectivity of the

2-Propylheptanal oxidation by lowering the reaction temperatures 35 ⁰ C decisively improved. At a reaction temperature of 25 ⁰ C (Table 2, column 2) no Cg-paraffins, no C ₅ acids are formed and no Cg ketone practical. The selectivity of acid formation is at this

Temperature only reduced by the formation of Cg alcohols. The same behavior applies to the oxidation experiment at 35 ^° C. Again, the selectivity was reduced mainly by the undesirable formation of Cg alcohols

Example 3

Preparation of 2-propylheptanoic acid in the presence of Mn / Cu catalyst / comparative example

The process of the invention, the oxidation of the

Cio-aldehyde mixtures to corresponding Cio-carboxylic acid carried out without catalyst. In the following example, the results of the comparative oxidation of 2-propylheptanal in the presence of Cu and Mn salts as

Catalyst shown.

For this purpose, 5040 g of educt with approx. Dissolved 86.6 wt .-% 2-propylheptanal before oxidation per 250 ppm of copper and manganese in the form of acetates. Thereafter, the reaction mixture was oxidized by the procedure described in Example 1 at 35 ⁰ C, 0.3 MPa reaction pressure and 6 vol .-% oxygen in the exhaust gas. For comparative purposes, the oxidation without catalyst was the same

Conditions performed. After 4 hours of trial time was the

Composition of the product mixture determined by GC analysis. The

Composition of the crude products obtained with and without catalyst is listed in Table 3, columns 2 and 3. ZO

Table 3 Product Composition

As shown in Table 3, the conversion of 2-propylheptanal oxidation in the presence of a homogeneous copper-manganese catalyst was significantly improved compared to the uncatalyzed reaction. The determined residual contents of 2-propylheptanal of approx. 10.42 mass% after 4 hours in the presence of catalyst are lower than the corresponding residual contents of

24.71% by mass of 2-propylheptanal in the uncatalyzed oxidation. The

However, selectivity of the catalyzed oxidation was significantly worse compared to oxidation without a catalyst. As can be seen from Table 3, column 3, the selectivity in the homogeneously catalyzed oxidation by the formation of by-products, such as nonane and nonanone, was reduced. This has the consequence that the yield of isomeric decanecarboxylic acids despite high sales of approx. 55% by mass of 2-propylheptanoic acid is comparable to the yield of uncatalyzed oxidation. Z.Λ

Thus, the experiments show that for the production of 2-propylheptanoic acid in high yield from 2-propylheptanal an uncatalyzed oxidation with oxygen at low temperatures is advantageous.

Claims

£ 1 claims

1. A process for the preparation of a mixture of isomeric decanecarboxylic acids, wherein the following steps are carried out:

5 a) Hydroformylation of a hydrocarbon mixture containing linear

C4 olefins, using a rhodium-containing

Catalyst system;

b) aldol condensation of a mixture of C5 aliphatic aldehydes obtained from step a);

lo c) Selective hydrogenation of the mixture of unsaturated C10 aldehydes

Step b) to C10 aliphatic aldehydes;

d) uncatalyzed oxidation of the mixture of aliphatic C10-aldehydes from step c)

obtaining a mixture with a proportion of at least 70% by mass of 2-l5 propylheptanoic acid based on the total content of the isomers

Decancarbonsäuren.

2. The method according to claim 1, characterized in that the

Hydrocarbon mixture in step a) containing linear C4 olefins, up to 5

20% by mass of isobutene based on the fraction of linear C4 olefins

having.

3. Process according to claims 1 to 2, characterized in that the oxidation of the mixture of aliphatic C10 aldehydes in one

25 temperature range of 25 to 35 ⁰ C takes place.

4. Process according to claims 1 to 3, characterized in that the oxidation of the mixture of aliphatic C10-aldehydes takes place at a pressure between 0.1 to 1 MPa.

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5. Process according to claims 1 to 4, characterized in that the oxidation of the mixture of aliphatic C10 aldehydes at a pressure Zό takes place between 0.1 to 0.5 MPa.