DE2107813A1 - Process for the selective oxidation of straight-chain paraffinic compounds - Google Patents

Description

dr. W. Schalk dipl.-ing. P. Wirth · dipl.-ing.G. Dannenberg DR. V. SCHMIED-KOWARZIK · DR. P. WEIN HOLD · DR. D. GUDEL

SK / SK Cas 57

6 FRANKFURTAM MAIN CR. ESCHENHEIMER STRASSE 39

Labofina SA 33 rue da la Loi 1040 Brussels, Belgium

Process for the selective oxidation of straight-chain paraffinic compounds

The present invention relates to a method for selective Oxidation of straight-chain paraffinic compounds of the general formula:

CH ₃ -CH ₂ - (CH ₂ ) _n -CH-CH ₂ Y ² ^

Y ¹

in which η stands for an integer from 1 to 16, Y ¹ and Y ² each stand for a hydrogen atom and / or a substituent, in a liquid phase with preferably images of monoketones of the general formula:

CHo-C- (CH ₅ ) ,, - CH-CH ₀ Y ² (il)

Il * · ^Π I «^

Oy ¹

12th
in which n, Y and Y have the above meaning.

For the sake of simplicity, the methyl group at the end of the chain that corresponds to that with Y ¹

and Y is opposite the substituted end (or either of the two methyl

1 2

groups, when Y and Y are each hydrogen) referred to below as "terminal methyl group"; the term "methyl ketone" refers corresponding to a compound of the general formula, (il), even if

12th
Y and Y represent functional groups.

Ί09849 / 1846

Numerous works have been directed to the oxidation of paraffinic compounds, in particular straight-chain paraffinic hydrocarbons, by molecular oxygen in the liquid phase in the presence of catalysts or without them. With these hydrocarbons, the temperatures required are usually between 100-200 ° C., and a mixture of fatty acids with a lower number of carbon numbers than the starting hydrocarbons and various neutral products such as ketones, alcohols, esters, peroxides, and hydrogen peroxides are obtained. During these reactions, the "hydrocarbon chain" is severely broken, which means that the yield of any particular product is low. The conclusion from the known work was that straight-chain paraffinic hydrocarbons are almost

sti
finally oxidized in a static manner without selectivity on the methylene groups within the chain; this conclusion is consistent with those drawn from chlorination, nitration and other substitution reactions.

For paraffinic compounds that are already substituted with a functional group, some orientation has been observed in these reactions: with most substituents, such as CH ₂ Cl, CCl ₃₁ CN, COX, "COOR (where X for a halogen atom and R for hydrogen or a hydrocarbon radical), the carbon atom in the (position with respect to the substituent is strongly deactivated, and the substitution is preferably carried out on the β-carbon atom.

For industrial purposes, however, it is particularly advantageous to use oxidation paraffinic compounds to direct the preferential formation of compounds of one species, and in particular to a compound that is near the end of the carbon chain, e.g. in the «(position with respect to the terminal chain defined above Methyl group, is oxidized.

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The aim of the present invention is therefore a method that duplicates this Selectivity meets and brings the following advantages

- the oxidation of the paraffinic compounds takes place with. selective education of monoketones with the same number of carbon atoms as the starting compound;

- The carbonyl function is preferably in the o ( position with respect to the terminal methyl group;

- both selectivities take place within a wide temperature range,

thereby adjusting the response rate by adjusting j the temperature is possible;

- the cobalt salt is easily regenerated for reuse;

~ The oxidation products can easily be obtained from the reaction mixture will.

The inventive method for the oxidation of straight-chain paraffinic Compounds of the general formula:

GH ₃ -CH ₂ - (CH ₂ ) _n -CH-CH ₂ Y ² (i)

Ϋ ¹

in which η stands for an integer from 1 to 16, Y stands for a hydrogen atom or a substituent such as X, CN, COOR, OCOR, where X is a halogen atom and R is a hydrocarbon radical with 1-6 carbon atoms

2 1 1

and Y is Y ₁ CHX ₂ or CX ₃ , where Y is a hydrogen atom,

if Y is CX ₃ , or Y is X, if Y ^{2 is} CX ₃ or CHX ₃ , in the liquid phase in the presence of a cobalt salt for the selective formation of monoketones of the general formula:

CH ₃ -C- (CH ₂ ) _n -CH-CH ₂ Y ² (11)

0 γ ¹

12 '

in which n, Y and Y have the above meanings, with the same number of

1.09849 / 1846

Carbon atoms like the starting compound, characterized in that the paraffinic compounds with a cobalt salt that has a ratio of trivalent cobalt to total cobalt between 0.5 and 1.0, based on metallic cobalt, the cobalt salt in a concentration of van at least 0.05 mole is present per liter of reaction mixture, at a temperature between 20-120 C. and in the presence of molecular oxygen in Brings touch. The oxidation can take place at a partial pressure between 0.1 and 50, preferably 1 to 10, atm. be performed.

• The cobalt salt used can be a salt of a carboxylic acid with 2-4 carbon atoms be.

It was found that under these conditions the oxidation of the paraffinic compound is not only aimed at the formation of carbonyl ketones, but that the rate continues by varying the reaction temperature and cannot be regulated by adding activator without a disadvantageous change in selectivity.

The inventive method can be used for any paraffinic compound Formula (i) above may be applied, and it has been found that is Oxidation selectivity at the o (position with respect to the terminal methyl group regardless of the chain length of the starting compound.

According to the invention it is not always essential to use a solvent in order to carry out the process according to the invention in the liquid phase. In some Cases the cobalt salt is soluble in the paraffinic substrate and the reaction can take place in the solution thus obtained. But where the cobalt salt is not very soluble in the substrate, a solvent is preferably used in which both the substrate and the cobalt salt are soluble

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are, the solvent against oxidation under the reaction conditions is practically inert. Lower fatty acids with 2-4 carbon atoms and their mixtures can be used for this purpose. Of these Acetic acid is particularly preferred for solvents.

The process according to the invention can also be used when the reaction mixture comprises two phases, on the one hand the liquid, paraffinic compound to be oxidized and on the other hand a solution of the cobalt salt in a solvent in which the paraffinic compound is not completely soluble. Thus, the paraffinic compound, for example, may be emulsified with an aqueous solution of the cobalt salt, etc., or with a solution of the salt in a mixed solvent of water and a lower fatty acid. With such a system, the paraffinic substrate can be used to extract the reaction products, which are protected against subsequent decomposition.

Of the cobalt salts to be used according to the invention, those of the carboxylic acids are used particularly preferred because they are sufficiently soluble in both organic and aqueous media. Although the cobalt salt of every carboxylic acid Salts of the lower fatty acids with 2-4 carbons can be used Substance atoms are particularly preferred because their cobalt form is easily different from the corresponding Cobalt shape is produced. So you can, for example, cobalt acetate through produce joint oxidation of cobalt acetate and acetaldehyde in acetic acid in the presence of oxygen.

To an effective and selective oxidation by the method according to the invention ensure that the cobalt salt is used in a relatively high concentration, i. at least 0.05 moles per 1 with a ratio of trivalent cobalt to total cobalt, i.e. K = Co (III) / Co (III) + CO (II), over 0.5, based on metallic cobalt is used. Is the concentration of the cobalt salt

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below this limit, the reaction rate is practical for Purposes too few. Although the unique selectivity of the process according to the invention for methyl ketones even at cobalt concentrations of only 0.01 mol per 1 can be determined, the best results will be with a cobalt concentration of at least 0.05 mol per 1, in particular at least 0.1 mol per 1, obtained. It will be apparent to those skilled in the art that in each The cobalt concentration to be used in the particular case is determined by practical and economic considerations, the upper concentration limit being that at which the reaction mixture is saturated.

In the course of the reaction, the cobalt content of the cobalt salt becomes progressively in the cobalt form is reduced, so that both types are always present in the reaction mixture are present. It has been found - and this is an important feature of the present invention - that when the cobalt salt is used in the The relatively high concentration given above has its oxidative effectiveness is clearer when the K ratio is higher, with this effectiveness * becomes almost insignificant when both forms of cobalt are present in equivalent amounts. In this case, i.e., when K is almost 0.5 or less, not only will The rate of reaction is drastically reduced, and the process is No longer suitable for industrial purposes, but loses the reaction their selectivity, i.e. the formation of the ketones, is in favor of a nonselective one Production of acids diminished. If the temperature is increased to accelerate the reaction rate, so will the loss increased selectivity. To achieve high methyl ketone yields, the K ratio should therefore be kept between 0.5 and 1, preferably between 0.6 and 1 will. In order to meet these conditions, the cobalto salt formed during the reaction has to be reoxidized continuously. To this end

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various known methods can be used. So can it Cobalt salt e.g. by anodic oxidation or by chemical measures, E.g. co-oxidation in the presence of oxygen with an easily oxidizable compound, v; oe acetaldehyde, benzaldehyde or methyl ethyl ketone, is oxidized will. A particularly convenient method is the continuous introduction of acetaldehyde into the reaction mixture.

An important and unexpected feature of the present invention lies in the finding that, under the conditions given above, the unique selectivity of the process is also observed at temperatures of up to 120 ° C., ie at temperatures close to those common in many, nonselective ones Process temperatures used. This feature is extremely beneficial because you can the optimal temperature for carrying out the desired oxidation in a relatively wide range, ie between 20-120 ⁰ C., according to the reactivity of the substrate, its solubility in the reaction medium "and select other factors. In the however, in most cases the optimal temperature is between 30 ~ 100 ° G. and more often

ο.

between 50-70 C.

For the inventive selective formation of methyl ketones, it is necessary to work% in the presence of a gas phase molecular oxygen-containing phase and stir vigorously for rapid diffusion of the oxygen in the liquid phase. The gaseous phase can consist of pure oxygen or a mixture of oxygen with other gases which are inert under the reaction conditions; for example air can be used; The partial pressure of oxygen can be between 0.1-50 atm. lie. In special cases it is possible to use Drur ¹ 'outside this range. For example, a pressure below 0.1 atm. sufficient if one stirs sufficiently effectively. On the other hand you can too

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-B-

Pressures over 50 atm. be applied; however, this does not lead to any improvement, which would justify the additional cost of the facility. Usually an oxygen pressure of 1-10 is required to achieve a high proportion of ketones Atm. applied.

The products made according to the invention have many industrial uses. The ketones are used as solvents, plasticizers and flavorings. After hydrogenation they are converted into secondary alcohols, used in the manufacture of surfactants. Through further oxidation, they provide fatty acids with a wide range of uses. the Oxidation products obtained from already substituted paraffinic compounds can be used to prepare difunctional derivatives such as diacids and Amino acids, in turn, are used in the manufacture of polyamides are suitable.

The following examples illustrate the present invention without limiting it.
Example 1

This example shows the oxidation of n-heptane to monoketones, in particular to 2-heptanone.

A solution with 0.33 mol / l cobalt acetate in acetic acid and with a K ratio from 0.93 was heated to 60 C., then heptane was up to one Final concentration of 0.80 mol / l added. The obtained solution was the same Temperature stirred in the presence of oxygen at atmospheric pressure. After 30 minutes the reaction was stopped by reducing the cobalt i- ions interrupted with an aqueous solution of a ferrous salt.

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The reaction products were extracted with ether and then treated the extract is fractionated with alkali into acidic and non-acidic components; the fractions obtained were separated by vapor phase chromatography analyzed.

It was found that 2.9% of the starting heptane had been converted to the formation of the following products, the ratios of which are given in mol: Heptanones: 63% (isomeric 2: 79%, 3: 15%; 4: 6 %)

Heptanols: 15% (isomeric 1: 0%; 2: 70%; 3: 22%; ^: 8%) j

Acids: 17%
other connections: 5%

As can be seen, heptane is produced by working with the present invention Conditions mainly in monoketones with selective formation of 2-heptanone converted. It is noteworthy that, due to statistical oxidation of the methylene groups, the relative proportion of 2-heptanone is only 40% instead of 79%

of the present example should be.

Example 2 ""

This example shows the oxidation of n-hpetane in the presence of another J.

Solvent than acetic acid.

Example 1 was repeated using propionic acid instead of acetic acid.

The reaction products were mainly monoketones with a 2-heptanone. share of 81%. .

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Example 3

This example shows the oxidation of n-heptane in a two-phase system.

83 cc of a solution of 0.75 mol / l cobalt acetate in a mixed solvent from water (40 vol.%) and acetic acid (60 vol.%) and with a K ratio from 0.97 was heated to 60 C. Then 17 ecm • Heptane added, most of which remained as a separate phase. the obtained two-phase mixture was vigorously stirred at the same temperature in the presence of oxygen at atmospheric pressure. After 6 hours the reaction mixture was treated as in Example 1 and analyzed.

It was found that 54% of the oxidation products consisted of monoketones, the proportion of 2-heptanone being 77%.

Example 4

This example shows the oxidation of a paraffinic compound with a

- carboxylic acid salt of cobalt in the absence of a solvent, f

A solution with 0.30 mol / l cobalt pelargonate in pure n-heptane and with a K ratio of 0.80 was added with stirring in the presence of oxygen Maintained φ atmospheric pressure at 60 C. After 3 hours, the reaction mixture was treated as in Example 1 and analyzed.

It was found that the heptane was mainly converted into monoketones, whereby the proportion of 2-heptanone was 79%.

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_ 11 _

Example 5

This example shows the oxidation of n-decane to monoketones, in particular in 2-oecanone.

A solution with 0.22 mol / l cobalt acetate in acetic acid and with an ratio of 0.91 was heated to 60 ° C., then decane was added to a final concentration of 0.5 mol / l , whereupon the further procedure was followed from Example 1 repeated.

According to analysis, 3.7% of the starting decane was used in the following products ,

converts, the relative proportions of which are given in MoI-p / o: ™

Decanones: 54% (isomeric 2: 63%; 3: 12 ° />; 4 + 5: 25 ■} &) Decanols: 15% (isomeric 2: 53%; 3: 13 p, 4 + 5: 34 ⁰ J ₀ ) acids: 24%

other connections 7 ⁰ Yes.

The relative proportion of 2-uecanone be only 25% instead of the 63% obtained in the present example .

Example 6. j

This example shows the shows the selective oxidation of the methyl ester of Enanthic acid in oxo derivatives, especially in 6-Cxoönanthate.

A solution of 0.39 mol / l cobalt acetate in acetic acid with a K ratio of 0.91 was heated to 60 ° C., then methyl enanthate was added to a final concentration of 1 mol / l ; then the procedure was as in Example 1.

1 09849/1846

According to analysis, 2.6% of the starting ester had been converted into the following products, the relative proportions of which are given in MoI-JJO: Oxo-enanthates: $ 75 (isomer 6: 72%; 5; 16%; 4: 11%; 3 + 2: 1%) Hydroxyönanthate: 9 i (isomeric 6: 85%; 5: 15%; 4 + 3 + 2: 0%) acids: - 7 ■) &
other connections: 9%

By static oxidation of the methylene groups, the relative proportion of 6-oxoonanthate should be only 20% instead of the 72% in the present example. Example 7

This example shows the selective oxidation of various straight-chain paraffinic compounds of the formula:

₄ -CH-CH ₂ Y Y ¹

These compounds were oxidized under the conditions of Example 6 and in each case mainly converted into monoketones (oxo derivatives), their relative proportions are given in the following table:

Y ¹ Y ² räati
C.
7th ve to
C.
6th share
C.
5 the
C.
4th Oxo derivatives
C CY ¹
3 2 2 16 1 - CY ²
1 H Cl _ 75 16 5 C. 16 2 _ Cl H 74 17th 8th - - H OCOCH ₃ - 69 13th - OCOCH ₃ H . - 74 18th 7th - H CSN - 74 10 -

As can be seen, the proportion of the 6-oxoisomer is usually more than 3-fold higher than calculated from the static oxidation of the methylene groups.

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Be is ρ ie 1 8

This example shows the selective oxidation of the methyl ester of pelargonic acid Oxo derivatives, especially the 8-oxo derivative. Terms and procedures were as in Example 6. It was found to be 2.2% of the starting ester were converted into the following products, the relative proportions of which in MqI-% ' are specified.

Oxopelargonate: 75% (isomeric 8: 58%; 7: 11%; 6: 10%; 5 + 4: 19%

Hydroxypelargonate: 16% (isomeric 8: 54%; 6 + 7: 33%; 4 + 5; 13%

. 3 + 2: OP / ₀ JI

Acids: 6%

other connections: 3%

By static oxidation of the methylene groups, the relative proportion of 8-oxopelargonate should be only 14% instead of the 50% in the present example. Example 9 ,

This example shows the effect of temperature on the selectivity of oxidation of n-heptane and n-decane.

Unless otherwise stated, the procedure was as in Example 1.

The results are shown in Table I. They show that with both hydrocarbons the selectivity of the oxidation in the ^ position with respect to the terminal methyl group remains decidedly higher than the static value (40% for heptane and 25% for decane), even at a temperature of up to 120 ^° C.

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Hydrocarbon temp.

C.

n-heptane

n-decane

Concentration of hydrocarbon cobalt mol / lg / l

Table I.

Reaction monoketones; relative "jo of the isomers: time; min" _ _Λ _

40

60

80

100

120

40

60

100

1.12
1.12
1.12
1.12
1.12

0.50

0.50
0.50

0.33 0.33 0.33 0.33 0.33

81 79 78 76 66

65 63 59

13th

15th

15 '

17th

24

12 12 15

6 6 7 7

10

23 25 26

Example 10

This example shows the influence of the cobalt concentration on speed and selectivity of the oxidation of n-heptane.

Various tests were carried out with cobalt solutions of different concentrations and each with a K ratio of 0.95. The general The procedure was as in Example 1, but the temperature 100 C. and the Reaction time was 180 minutes. The results were as follows:

Co concentration

g / l 0.01 0.02 0.05 0.1 '0.2 0.3 0.5 j

Heptane conversion

in oxidation 0.4 0.70 1.1 1.8 3.2 3.8 6.2

Products; %

relative share of

2-isomers in the 58 58 61 66 67 69 71

Heptanones; ° / a

These data clearly show that both speed and selectivity the reaction are strongly dependent on the cobalt concentration, with the best results being achieved with the higher cobalt concentrations.

Example 1_

This example shows the influence of the K ratio on the rate of reaction and the selective formation of ketones from n-heptane.

Experiments were carried out with cobalt solutions with different K ratios. However, the concentration of trivalent cobalt was in each case equal (about 0.28 u / 1). Unless otherwise stated, the procedure was as in Example 1 worked. The results are shown in Table H

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Table H.
Temp .; C. 60. . 100

original 0.93 0.60 0.50 0.50 0.50 0.96 0.60 0.50 0.50 K ratio

Response time ^ _{5 Q> 5 Q> 5 ß 1fl} ^ _{25 Q} ^ ₅ ^ _{35 g}

Heptane converter

in Oxydat.pro- 2.9 0.5 0 0.3 0.9 3.1 1.7 0.6 3.7 ducts; %

i «« 0 * 41 «■ * i 3D 19

^ω relative share

2 ^ d.2 isomers 79 78 0 80 78 76 75. 72 71 I.

Z ^ in the hepta-

_p »nons; ^c / a σ>

+ - Mol-Jji, monoketones in oxidation products

These results show that there is a decrease in the K ratio

(1) causes a decrease in the rate of reaction, which becomes more noticeable, as the ratio approaches 0.5. For example, at 100 G. with a K ratio of 0.6, the reaction rate is three times faster than with a K ratio of 0.5 ;;

(2) a decrease in the formation of monoketones, especially 2-heptanone, which becomes more noticeable as the ratio drops below 0.6 and approaches 0.5,

cause.

Example 12 '|

This example describes a practical procedure for maintaining a high K ratio during the reaction by continuous introduction of acetaldehyde in the reaction mixture.

A 1-1 stainless steel autoclave, equipped with a mechanical stirrer, heating mantle, cooling coil, gas inlet tube, exhaust valve and means for introducing and withdrawing liquids, was charged with 500 ecm of an acetic acid solution of cobalt acetate with a cobalt concentration of 0.60 mol / l and a K ratio of 0.95. After a pressure of 10 kg / cm ^{2 had been set} , the mixture was heated to 50 ° C. with stirring, air being introduced at a rate of 100 1 / hour. After a temperature of 50 ° C. was reached, cobalt acetate and heptane (both dissolved in acetic acid) were introduced separately into the autoclave. This flowing mixture of solutions contained 0.50 mol / l cobalt acetate with a K ratio of 0.95 and 0.75 mol / l n-heptane. Its flow rate was adjusted so that a watering time of 30 minutes resulted in the reactor, the volume in the reactor being kept at 500 ecm by continuously withdrawing the reaction mixture through a control valve. After reaching equilibrium conditions

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Samples of the effluent were taken and as in Example 1 treated and analyzed.

Another experiment was carried out under the same conditions, but with acetaldehyde in the inflowing mixture at a concentration of 0.21 mol / l was present.

The test results are compared in Table III.

Table III

Acetaldehyde - +

K ratio in the outflow 0.82 0.98

Heptane conversion into oxidation products; ⁰ J ₀ 2.8-8.2

Yield of heptanones * 73 67

relative proportion of the 2-isomer in the ""

Heptanones; ° / o ^{/ b}

* β MoI- ^ monoketones in the oxidation products

Claims (7)

- 19 claims Y ¹
in which η is an integer from 1 to 16, Y is a hydrogen atom or a substituent such as X, CN, COOR, OCOR, where X is a halogen atom and R is a hydrocarbon radical having 1-6 carbon atoms, and Y ^{2 is} Y ¹ , CHX ₂ or CX ₃ , where Y is a hydrogen atom when A Y ^{2 is} CX ₃ , or YX is when Y is CX ₃ or CHX ₃ , in the liquid phase in the presence of a cobalt salt with selective formation of monoketones with the same number of carbon atoms as the starting compound, where the monoketones have the following general formula: ^w 11 * - "1 0 Y ¹ 1 2 in which n, Y and Y have the meaning given above, characterized in that that the paraffinic compounds with a cobalt salt, that is a ratio of trivalent cobalt to total cobalt between j 0.5 and 1.0, based on metallic cobalt, and in a concentration of at least 0.05 mol per 1 reaction mixture is present, at a temperature between 20-120 ° C. and in the presence of molecular oxygen brings in touch. 2.- The method according to claim 1, characterized in that the oxidation at a partial pressure between 0.1-50, preferably between 1-10, atm. is carried out. 846 3.- The method according to claim 1 and 2, characterized in that the concentration of the cobalt salt is at least 0.1 mol / l. 4.- The method according to claim 1 to 3, characterized in that the cobalt salt is a salt of a carboxylic acid having 2-4 carbon atoms. 5, - Method according to claim 4, characterized in that the salt is the Is the cobalt salt of acetic acid. 6.- The method according to claim 1 to 5, characterized in that the oxidation is carried out in the presence of a lower fatty acid having 2-4 carbon atoms or a mixture of these acids as a solvent. 7.- The method according to claim 6, characterized in that the solvent Acetic acid is used. The patent attorney: -j . ,. </ ι 846