DE1418852C - - Google Patents

Description

3 4

the desired amount of oxygen can be determined so that both carboxylic acids and ketones are formed in the reaction mixture for a certain period of time during the reaction if one is passed. After the reaction is complete, aralkyl compounds containing methyl and carboxylic acids or ketones from the reaction - other alkyl radicals start out,
mixture separated. It is assumed that cobalt, bromine and vinegar are conventional processes. The process according to which acids combine in a specific way and thereby the invention can also be delivered continuously through the novel catalyst of the invention, if both an aralkyl compound is used. The composition adds cobalt-bromine catalyst. On the other hand, it can be so crucial that the replacement of one or a part of the catalyst in one part of the mixture of several constituents for other elements is absent, while in the other part it is neither completely prevented nor significantly added to the reaction partner. So it can be affected. So the catalytic action will be cobalt present in the acetic acid and bromine will be severely restricted if substantial amounts are added with the aralkyl compound. If other elements, which are usually excellent starting liquids for a first reaction in oxidation catalysts, are used during the purification of a subsequent one, action must be present. For example, the reac the catalyst will not have to be replaced; it can be used continuously in the presence of appreciable quantities. Iron, copper or the like almost completely prevented. The term "aralkyl compound" is used in Figure 20. Similarly, the presence of the present invention prevents organic compounds from having significant amounts of certain anions, e.g. B. from, which have an aromatic nucleus, the sulfates, nitrates or chlorates, the effectiveness t is bound to at least one alkyl radical. This one of that peculiar catalyst. Replacing the 'alkyl radicals can methyl, ethyl, propyl, butyl bromine by other halogens, eg. B. by chlorine, or octyl radicals. The expression therefore includes 25 then the catalyst does not contain any noticeably larger aralkyl hydrocarbons, e.g. B. the alkylbenzenes and catalytic effect as the cobalt acetate, which the various alkylnaphthalenes, ie mono-, found use in the known processes. The di- and tri-benzenes containing the alkyl substituents contain significant amounts of iodine, e.g. B. toluene, the three isomeric xylenes, Me- makes the catalyst completely ineffective, sithylenes and mono-, di-, tri-, tetra-diphenyls, 30 If one sets the effect of cobalt and acetic the alkyl substituents, z. B. Diphenyl acid in the oxidation of o-xylene, the dependent methane, mono-, di-, tri-naphthalenes, the alkyl constant of action is equal to one, then chlorine is contained in substituents, for example, methylnaphthalene compound with cobalt and acetic acid as well one or amylnaphthalene. Except for the hydrocarbon-dependent constant of action equal to the unit. In terms of substances, the term also includes aralkyl compounds. In contrast to this, when bromine is used in compounds that contain other elements besides carbon, cobalt and acetic acid contain a hydrogen, z. B. Oxygen, sulfur comfortably high relative constant of action of 275 or bromine. The term embraces the three isomers obtained.

Toluic acids, acetophenones with alkyl substituents, the molar ratio of cobalt to bromine, for a-diphenyl ketones with alkyl substituents, e.g. B. p, p'-di- 40 atomic bromine calculated (Br atomic weight 79.916), methyldiphenyl ketones, diphenyl sulfones with alkyl is important for the reaction rate. The substitutes, e.g. B: ρ, ρ'-dimethyldiphenyl sulfone, etc .; the best reaction rates are achieved, bromotoluene, bromotoluic acid, etc. The expression when cobalt and bromine are present in approximately the same mol-λλ also includes arylmethyl compounds in different proportions (ie 0.9 to 1.1 mol). '/ Alkyl radicals than the methyl radical, e.g. ethyl 45 The rate of reaction decreases rapidly, toluene, the other alkyl radicals of which are usually oxidized to ketones as the ratio of bromine to cobalt increases during the reaction. is and vice versa: is the ratio of bromine The process according to the invention enables the cobalt to be reduced and decreases below the unit production of aromatic carboxylic acids, ζ. B. worth, then the effectiveness is reduced; this reduction in o-phthalic acid from o-xylene and isophthalic acid from m-Xy is less pronounced.
IqI, terephthalic acid from p-xylene, benzoic acid If one takes a ratio of bromine to toluene, "-naphthalenecarboxylic acid from α-methylnaph-cobalt, which corresponds to 1, as a relative active thhalin, polycarboxylic acids from mesitylene- (1,3,5- Tri-constant of 100, in which an increase yields methylbenzene), the p, p'-dicarboxylic acids from the corresponding ratio to 1.2, p, p'-dimethyldiphenyl, p, p'-dimethyl-55 of only 20, and a further increase to diphenyloxide or ρ, ρ'-dimethyldiphenyl ketone, value 2 terminates the reaction. If, however, the ρ, ρ'-dimethyldiphenyl sulfone. It should be noted that the bromine-to-cobalt ratio is reduced to 0.77, so that some carboxylic acids with some do not result in a dependent constant of action of oxidized methyl radicals also during the 80, a decrease to 0.38 results in a constant reaction , e.g. B. o-, m- or p-toluic acid. 60 out of 50, and a further decrease to 0.0077 gives

The method according to the invention enables a constant of 5.

also the production of many aralkyl ketones, e.g. B. The mole ratio of acetic acid to cobalt is

o-Diacetylbenzene from OrDiäthylbenzol, rh-Diacethyl- not limited upwards, so that acetic acid as

benzene from m-diethylbenzene, p-diacethyjbenzene from solvent is used in the reaction.

p-Diethylbenzene, acetophenone from ethylbenzene, 65 Although small amounts of acetic acid

ρ, ρ'-diethyldiphenyl ethers, ρ, ρ'-diethyldiphenylke- can be used to support the reaction,

clays, ρ, ρ'-diethyldiphenylsulfones or α -acetyl- e.g. in a Mor ratio of 2: 1 to cobalt,

naphthalene from α-ethylnaphthalene. It should be emphasized so the use of larger amounts is recommended

5 6

of acetic acid for achieving the best yields The process according to the invention can be used with

and reaction rates, especially towards atmospheric, atmospheric or supra-atmospheric the amount of solvent. spherical pressure. It will

The cobalt content of the catalyst does not, however, provide any particular advantage if divalent or trivalent cobalt compounds, in particular at a pressure other than atmospheric pressure, are used in particular cobalt salts of carboxylic acids and co, since a reaction is carried out with balt bromide. If the reaction is carried out in the presence of a relatively large amount of acetic acid in the presence of a subatmospheric pressure, then moderately cumbersome control equipment is required, the cobalt binds, regardless of its form they have a proportionate acetate. Hence, any cobalt salt of the described costly apparatus for carrying out the type which is soluble in acetic acid for the process is high temperature process. Because the response is appropriate. The preferred cobalt donor is cobalt - at atmospheric pressure in a satisfactory manner acelate tetrahydrate (also known as I) Co (OAc) ₂ · 4 H ₂ 0 «, it does not seem advantageous to use it at increased drawing). Other suitable cobalt catalysts are to allow pressure to take place, although the use of cobalt salts of the lower aliphatic acids and excessive pressure does not result in any special e.g. B. cobalt propionate or cobalt butyrate. In addition, disadvantages, apart from the costs, arise, the cobalt salts of the aromatic carbon The reaction temperature for the process according to

acids, e.g. B. that according to the invention according to the invention is 80 to 115 ° C. The acids produced are preferably used as catalysts, and the reaction should be carried out at the reflux temperature. Cobalt toluate, cobalt reaction mixture can therefore be carried out. When terephthalate or cobalt naphthenate are used. Oxidation of the alkyl side chain to -a carbonyl-cobalt salts with anions that inactivate the catalyst or carboxyl radicals are formed, water as one / - \ four should be avoided; such cobalt salts are the reaction products. It has been found, for example, those that contain sulfate, nitrate, iodide, 35 that the presence of larger amounts of water contain an iodate or chlorate ion. has an adverse effect on the response. Has

The bromine content of the catalyst will usually provide an amount of water greater than 0.05 weight by bromine compounds, the bromine of which will easily divide per part of the acetic acid accumulated, so it can be released from the starting compound. the reaction largely prevented. Therefore, bromocarboxylic acids, for example the aliphatic bromine acids, such as the bromoacetic acids, the bromopropionic acids and a maximum of about 0.05 parts of water per part of the acids or bromobutyric acids, should take place as far as possible with exclusion of water; the cycloaliphatic acetic acid may be present. Insignificant water-carboxylic acids with separable bromine, such as α-bromine quantities, are often desired, since they serve to produce cyclohexanecarboxylic acid; free bromine (Br ₂ ); Bromine- to dissolve the Co (OAc) ₂ , Co (OAc) ^ H ₂ O is slightly hydrocarbons, the bromine bound in the form 35 soluble in acetic acid, while Co (OAc) ₂ have little that it can easily be derived from the starting compound is soluble. Co (OAc) ₂ , on the other hand, is released in hydrogen bromide, e.g. B. bromochloroform; Hydrobromic acid quite soluble. The dehydration during substance or cobalt bromide, it has been found that the reaction can easily be carried out if 1 mole of HBr per mole of cobalt acetate provides a catalyst that is exceptionally effective when the water is formed during its formation. 40 reaction distilled off. The action of the water

The amount of oxygen to be supplied can also be reduced by the reaction is not decisive and can depend on the ratio of aralkyl compound to the desired solution can be varied. Because the oxygen chooses the medium low. Azeotropes, e.g. B. benzene If there were the alkyl radicals of the aralkyl compound or heptane or acetic anhydride, can be equivalent to Oxidizing carbonyl radicals depends on the reactivity for the removal of water from the reaction mixture tion speed can be used to some extent. Besides being great on the amount of oxygen, which at the given time, amounts of water adversely affect the reaction the reaction mixture is present. So it is rivers, they cause a yellowish coloration of the the reaction rate is greater with a larger reaction products. If one leads the reaction under lower oxygen supply than a lower one. If water is excluded from it, the production is started has been able to achieve satisfactory results when supporting colorless products, the reaction mixture between 0.01 and 10, because the reaction proceeds extremely quickly

preferably 0.5 to 5 parts by weight of oxygen per hour and water is one of the reaction products and added per part of the aralkyl compound. a quick dehydration for the regulation of the It should be said that the method 55 has an oxidation rate. Any amount according to the invention not only is pure oxygen as an aralkyl compound in the reaction to form an oxidizing agent can use, but any casual if the water content of the reaction mixture oxygen-containing gas, the other constituents of which are not more than 0.05 part of the solvent, are neutral under the given reaction conditions. When carrying out the Ver-Man according to the invention was therefore able to achieve satisfactory results, 60 drivingly, satisfactory results have been achieved, if air is used in place of oxygen for the if between 0.01 and 0.5 parts by weight of the aralkyl reaction used. The reaction also proceeds in connection with each part of acetic acid in the desired starting point Way if you have used mixes from mix. Preferably contains oxygen and neutral gases, e.g. B. helium, neon, the starting mixture between 0.02 and 0.3 GeXenon, Krypton or argon, as a diluent 65 parts by weight of the aralkyl compound per part acetic acid, added to the oxygen. In the preferred embodiments, it will be understood that the ratio of aralkyl seduction examples For the invention, either binding to acetic acid is formed during the reaction Oxygen or air is used as an oxidizing agent. constantly changing, since the aralkyl compound to

corresponding carboxylic acid or is oxidized to the ketone. It is possible to reduce the water content to reduce the fact that the aralkyl compound is gradually added to the reaction mixture.

As already mentioned, the products are obtained by the oxidation according to the invention of the aralkyl compound to be oxidized dependent. If arylmethyl compounds are oxidized, they become primarily aromatic Carboxylic acids formed. If other aralkyl compounds are oxidized, then predominantly aryl ketones are formed delivered. If the aralkyl compounds contain both methyl and other alkyl radicals, then the resulting products contain both ketones and carboxylic acids.

A feature of the invention is the unusually rapid and peculiar reaction of oxygen to the α-methylene radicals of the aralkyl compounds having more than one carbon atom on the alkyl side chain, so that good yields of aralkyl ketones are provided. For example, ethylbenzene is oxidized according to the invention, one obtains infrequent * least a 80 to 90% 'ge conversion to acetonitrile ■ · * phenone. However, some ketones are more susceptible than others to further oxidation to carboxylic acids. As the length of the alkyl radicals increases, the corresponding ketones are more easily converted into carboxylic acids. For example, in the oxidation of propylbenzene, a lower yield of propiophenone and a better yield of benzoic acid are obtained when this yield is compared with that which ethylbenzene gives with respect to acetophenone and benzoic acid, although acetophenone is stable under the reaction conditions given.

It is sometimes desirable that the formation of carboxylic acids by further oxidation the ketones formed in the reaction is guaranteed. For example, it likes the reaction of the commercial mixtures containing both ethylbenzene and xylenes, the presence of acetophenone may be undesirable because it must be secreted as a harmful component. Man ^ should preferably oxidize other alkylbenzenes or / methylbenzenes to carboxylic acids.

It is possible to promote the further oxidation of the ketones to carboxylic acids by adding ozone introduced simultaneously with oxygen into the reaction mixture. The reaction according to the invention can thus converting aralkyl compounds either to ketones or to carboxylic acids and is therefore more versatile than the known processes. In addition, the method according to the invention is known Process superior in that large yields of carboxylic acids or ketones at high reaction rates can be obtained.

In an embodiment of the invention In the process, a mixture of ozone and oxygen is introduced into the reaction mixture, which thereby is produced by sending oxygen through one of the known ozone generators. The ozone generator usually provides such amounts of ozone from oxygen that the concentration of ozone is between about 12 and 14 percent by weight; the concentration of ozone to oxygen is not decisive. However, such an amount of ozone should be supplied that the desired Conversion of the ketones into carboxylic acids guaranteed. To achieve a full "conversion, at least 1 mole of ozone should be added per alkyl radical of the aralkyl compound.

The exemplary embodiments listed below serve to explain the invention in detail.

Unless expressly stated otherwise, all data relate to units of weight.

The working examples were made according to the below

general procedures given.

ίο An aralkyl compound and a solvent that Containing the catalyst were under vigorous. Stir in the reaction vessel, which on the reaction temperature had been warmed. At the same time, oxygen was introduced into the reaction mixture initiated. The water formed by the oxidation of the aralkyl compound became during the Reaction distilled off if not the reaction at temperatures below about 100 ° C in the presence of acetic anhydride, which drew the water.

Deviations from this method are indicated in the individual exemplary embodiments. In all examples, if not expressly stated, Co (OAc) ₂ · H ₂ O was used as a donor for the cobalt, and hydrogen bromide provided the bromine. Glacial acetic acid was used for the examples. In some cases specifically mentioned, the reaction was carried out in a closed vessel so that the oxygen absorption could be measured accurately.

The products of the invention were separated by the usual methods. Were aromatic Carboxylic acids formed, then the reaction mixture was left after the reaction had ended Cool down to room temperature. The precipitated aromatic carboxylic acid was then filtered off.

Any aromatic carboxylic acids left in the solution became the largest by evaporation Part of the acetic acid, extracting the resulting concentrate with chloroform to separate the Monocarboxylic acids from the dicarboxylic acids in the solution and subsequent evaporation of the chloroform, which supplied the monocarboxylic acids, won. The one remaining after extraction with chloroform The residue was washed with a small amount of aqueous hydrochloric acid, thereby removing the cobalt salts were washed out. The dicarboxylic acids were filtered off.

The ketones were obtained by diluting the reaction mixture with water, extracting the aqueous Solution with ether, whereby carboxylic acids and ketones are removed, extraction of the ethereal solution with a dilute, aqueous solution of sodium carbonate, whereby the carboxylic acids are separated and using the usual methods, e.g. B. Distillation, through the formation of insoluble derivatives, z. B. 2,4-Dinitrophenylhydrozone obtained.

Examples 1 to 15

In the following working examples, the concentration (in moles) of bromine is monatomic Bromine (Br atom weight 79.916) calculated.

The examples listed in Table I show how the various concentrations of cobalt and Bromine in acetic acid affect the rate of oxidation of o-xylene. The speed of response when using acetic acid as a solvent

.. 309 623/106

mean, which represented 0.1 mol in relation to cobalt and bromine, was arbitrarily chosen as a value of 100 and thus created a possibility of comparison. In the implementation of the examples were o-xylene, acetic acid, cobalt and bromine mixed and adjusted to about. 90 to 95 ° C heated during a certain amount of oxygen was introduced. The reaction was carried out in a closed vessel, so that the absorbed oxygen could be measured accurately and the supply to the absorbed oxygen has been adjusted. Since the reaction was carried out at 90 to 95 ° C, was the water is not removed from the reaction mixture; but the resulting amount of water was thereby reduced that the ratio of o-xylene to acetic acid was kept very low, i.e. H. 1.06 to 100 (0.1 mole in acetic acid). The results are shown in Table I.

Table 1
Influence of the catalyst concentration

example Mole concentration of
Catalyst in acetic acid Br dependent
Fast
constant Co 0.077 Iv 0.3 0.2 85 2 * 0.1 0.12 0 3 0.1 , 0.10 20th 4v 0.1 0.092 100 5v 0.1 0.077 95 6> ' 0.1 0.038 80 7v 0.1 0.077 50 8th 0.1 0.00077 17th 9 0.1 0.038 5 10 0.05 0.0154 12th 11th 0.02 0.0077 1 12th 0.01 0

was arbitrarily designated with the value 1. In all examples the cobalt donor was cobalt acetate tetrahydrate (Co (OAc) ₂ · 4 H ₂ O). Concentrated hydrochloric acid (HCl) was the source of the chlorine and hydrogen bromide provided the bromine. In carrying out this example, ethylbenzene, acetic acid and Co (OAc) _{2 · 4H 2} O alone, or in conjunction with HCl or HBr, were mixed and heated to about 90 to 95 ° C while a certain amount

ίο oxygen has been introduced into the system. The reaction was carried out in a closed system so that the oxygen absorption could be accurately determined because the rate of oxidation was dependent on the oxygen absorbed. Since the reactions were carried out at 90 to 95 ^° C., the water did not need to be removed from the reaction mixture; but the amount of water produced was reduced by choosing the ratio of ethylbenzene to acetic acid very low, ie 1.06: 100, 0.1 mol in acetic acid. The results are summarized in table ΓΙ:

Table Il

example catalyst Mole conc
tration of the
Catalyst
in acetic acid dependent
Fast
constant 13th
14th
15th Co (OAc) ₂ · 4H ₂ O
Co (OAc) ₂ · 4H ₂ O
HCl
Co (OAc) ₂ · 4H ₂ O
HBr 0.1
0.1
0.1
0.1
0.1 1
1: 3
275

* CoBr ₂ · 6H ₂ O was the donor of cobalt and bromine. " The amount of oxygen absorbed indicated the complete conversion of o-xylene to o-phthalic acid.

It can be seen from Table I that a catalyst which has a bromine to cobalt ratio of 2 does not exert any appreciable effect. It can also be seen that the most favorable reaction rates are obtained when this ratio is ^{approximately equal to 1} , and that the reaction rate decreases rapidly as this ratio increases. If, on the other hand, the ratio of bromine to cobalt decreases and falls below the value 1, then the catalytic effect also decreases, although this decrease is less pronounced. It can also be seen that slow rates of oxidation occur when the catalyst concentration falls below 0.1 mole.

The exemplary embodiments in Table II show that the rate at which an aralkyl compound having more than one carbon atom on the alkyl side chain, e.g. B. ethylbenzene through the catalyst is oxidized to a ketone according to the invention, in contrast to the result when used cobalt alone or a catalyst in which bromine has been replaced by chlorine. The speed of response when using acetic acid as solvent, which was 0.1 mol of cobalt,

From the dependent rate constants in Table II it can be seen that the catalyst according to the invention is unique in that neither cobalt alone nor a catalyst that replaces bromine a related element, e.g. B. contains chlorine, a significant catalytic effect in the reaction exercises. The fact that only 1 mole of oxygen per mole of ethylbenzene was consumed in Example 15, indicates that the ethylbenzene was converted into acetophenone and that the reaction stopped, when the ketone was formed.

B e i s ρ i e 1 16

This example shows the good yield of δ-phthalic acid, which is held by oxidation of o-xylene, a compound that is differentiated by the well-known Process using a cobalt catalyst only was difficult to oxidize with good yield. This example also describes that the xylene is sequential can be added and that acetic acid as a solvent, which the cobalt-bromine catalyst contains according to the invention, can be used again.

200 parts of acetic acid containing 0.1 mol of cobalt ions were added to a reaction vessel and heated to the reflux temperature, which was about 110 ⁰ C. A solution of 10 parts of o-xylene in 125 parts of acetic acid was added over 90 minutes to the reaction mixture, into which 70 parts of oxygen were passed per hour. The oxygen supply was maintained for a total of 5.5 hours. That by the oxidation of the

Xylene formed water was distilled off during the reaction. After cooling to room temperature the carboxylic acid precipitate was filtered off. . .

The starting liquid was used for a second Process further used, placed in a reaction vessel, heated to reflux temperature and 88 parts of o-xylene in 100 parts of acetic acid within

j of 100 minutes added over 5.5 hours

long oxygen was passed into the reaction mixture, namely 70 parts per hour. After expiration at this time the reaction mixture was left on Cool to room temperature, and 118.5 parts of o-phthalic acid that had precipitated were left filtered off. The starting liquid was evaporated to dryness and the residue with chloroform extracted. 14.7 parts of o-toluic acid were obtained from the chloroform solution by evaporating the solvent

j solvent. The residue yielded after treatment

with a small amount of water and concentrated hydrochloric acid so that the cobalt salts were dissolved.

26.7 parts of o-phthalic acid. From the distillate collected during both processes, became 9 parts. o-xylene recovered. The total yield of o-phthalic acid was 142 parts. the Yield of o-phthalic acid was 83% if the o-xylene that was present in the reaction uses for comparison. The yield of o-toluic acid was 6.2%, the total acid yield 98%

B e i s ρ i e 1 17

This example describes the use of bromochloroform as a donor for the bromine of the Catalyst.

A reaction mixture of 10.6 parts of p-xylene and 200 parts of acetic acid, 0.1 mol in ratio to cobalt and 0.05 mole to bromine (bromochloroform) was added to a reaction vessel heated to reflux. Oxygen (43 parts per hour) was then added to the reaction mixture for 2.3 hours introduced. The water formed by the oxidation of xylene became ι distilled off during the reaction. The reaction mixture was cooled to room temperature, and 13 parts of terephthalic acid (78% xylene used) were separated off. The residue of the Xylene was converted to p-toluic acid, which is soluble in the starting liquid.

B e i s ρ i e 1 18

This example describes the production of aromatic Carboxylic acids and ketones from a mixture of o- and m-xylenes and ethylbenzenes.

A reaction mixture of 10 parts of o-XyloJ, 20 parts of m-xylene and 525 parts of acetic acid, the had a ratio of 0.1 mole to cobalt and bromine, was heated to reflux and acidic substance (68 parts per hour) 2.75 hours tang introduced into the mixture. The water that; through the oxidation formed was distilled off during the reaction. After cooling to room temperature a precipitate of 41 parts of a mixture of phthalic acids was filtered off .. From the Mother liquor was an additional 3.6 parts of a mixture of dibasic acids and 6.2 parts of acetophenone recovered. The yield of phthalic acids was 71% and the yield of acetophenone was 59%.

Example 19

This example describes the oxidation of a bromine-containing aralkyl compound; H. o-bromotoluene. A reaction mixture of 100 parts of o-bromotoluene and 105 parts of acetic acid, which has a molar ratio of 0.80 to cobalt and 0.75 mole to bromine was heated to reflux and air was bubbled into the reaction mixture for 3.7 hours. The water that is oxidized ίο had formed was distilled off during the reaction. After cooling to room temperature, a precipitate consisting of o-bromobenzoic acid formed filtered off. The yield was 39 g.

B e i s ρ i e 1 20

This example describes the use of ozone as a means of increasing the yield aromatic acids and reduction in the yield of ketones in the oxidation of ethylbenzene.

This example also describes the use of acetic anhydride as a dehydrating agent. A reaction mixture of 12.7 parts of ethylbenzene and 210 parts of acetic acid, which has a molar ratio of 0.1 to cobalt and bromine, and 10 parts of acetic anhydride were added to reflux heated without being distilled off. Ozone (1.5 parts per hour) and oxygen (51 parts per hour) were introduced into the reaction mixture for 3.6 hours. After this time, the Products separated to give 8 parts of benzoic acid (55% yield) and 6.2 parts of acetophenone (43% yield), i.e. an overall yield of 98%.

B e i s ρ i e Γ 21

This example describes the oxidation of an oxygen-containing aralkyl compound to a phenyldi-alkyl-ketone.

A reaction mixture of 19.6 parts of p-Äthylacetophenon to cobalt and 100 parts of acetic acid, which had a molar ratio of 0.1 to cobalt and bromine, was heated to 65 ⁰ C. Oxygen (51 parts per hour) was then bubbled into the reaction mixture for 2 hours and 10 minutes. At the end of this time the temperature of the reaction was 30 ^° C. The products were separated and 23 parts of p-diacetylbenzene were obtained, a yield of 71%.

Example 22

This example describes the oxidation of an aralkyl compound with a methyl and an ethyl side chain to a keto carboxylic acid. .
A reaction mixture of 12 parts of p-ethyltoluene and 105 parts of acetic acid, which had a molar ratio of 0.1 to cobalt and bromine, was heated to reflux without being distilled off. Oxygen (51 parts per hour) was bubbled into the reaction mixture for 45 minutes.

A total of 20 parts of acetic anhydride was added dropwise for dehydration during the Reaction added. The reaction mixture was poured into water and p-acetylbenzoic acid

O O

CH ₃ ^ C- _N

-COH

filtered off.

The acids can be esterified and used as plasticizers in synthetic resin compositions, e.g. B. polyvinyl chloride or polyvinyl acetate. Dibasic acids by the process according to the invention can be reacted in a manner known per se with polyhydric alcohols to give polyester resins.

The ketones prepared according to the invention can be used as solvents for various purposes, e.g. B. at Coatings, in vinyl or vinyl derived resins. Besides, they can in the manufacture of various drugs, e.g. B. antihistamines or anti-motion sickness drugs, find use as intermediates. Acetophenone, for example, can be used to manufacture of the drugs listed in the Chemical and Engineering News, Vol. 34, No. 10, p. 1122 (of March 5 1956), can be used.

From the detailed description it appears that a fast, novel and versatile oxidation process is delivered.

Comparative example A.

The aim of the following experimental examples is to show that the essential features of the process according to the invention are quite critical when good reaction rates at low temperatures should be achieved.

In these experiments p-xylene was used as the starting material used because the corresponding carboxylic acid, namely terephthalic acid, essentially is insoluble in the reaction mixture. For this reason it is only possible through observation determine at what point in time a precipitate is first formed, if it is due to oxidation comes to the production of terephthalic acid. In addition, the precipitate can easily be filtered off from the reaction mixture to increase the overall yield of terephthalic acid at a given point in time.

The following experiments were carried out at atmospheric pressure and it became general procedures given below are used. Acetic acid was used as the solvent in these experiments used. When carrying out the experiments, the catalyst concentration was given in gram molecules stated per 1000 grams of the solvent.

Table III Molarity
(Gram molecules

per liter) 0.01 0.02 0.05 0.1

Gram molecules

per 1000 g of the

Solvent

Acetic acid 0.00915 0.0183 0.04575 0.0915

The general procedure was carried out as follows:

A solution containing 25 ml of acetic acid (26.2 g) and 1.06 g of p-xylene (1.2 ml, 0.01 mol) was used as Standard reaction solution used. The required amount of cobalt and bromine was added to this solution added as cobalt acetate tetrahydrate and cobalt bromide hexahydrate. Table II gives the required Weights in grams to make 0.01-0.05 molar solutions in 25 ml of a solution. From it the higher values used can easily be determined, i.e. i.e. 0.1 M is ten times the value for 0.01 M.

Table IV

0.01

2/1 I l / l molarity

0.02
Br-Co ratio

2/1 | 1/1

0.05

2/1

1/1

Cobalt acetate

Cobalt bromide

total weight

Weight calculated as Co-Br ₂

Weight of the XyIoIs, calculated
as Co-Br ₂ *)

0.083 0.083

0.0315 0.0415 0.0730

0.056

5.25 0.166
0.166

0.063
0.083
0 ^ 146

0.111

10.5

*) based on the catalyst concentration as calculated in patent 2,833,816.

0.415 0.415

0.158 0.208 0.366

0.278 26.2

The solutions were placed in a reaction vessel fitted with a thermometer, a reflux condenser and an inlet with a glass frit for oxygen at the bottom of the vessel was. By introducing oxygen in this way, the mixture was mixed well. The reaction vessels were placed in a heating bath which was heated to a constant temperature would. When the reaction mixtures had reached the temperature of the heating bath, one began with the passage of oxygen at a rate of 100 ml per minute. When performing the The maximum temperature of the reaction mixture was tested due to an exothermic Reaction, the time for the first precipitate of terephthalic acid to form, and the total time the reaction is controlled. In those cases where a precipitate was formed, the reaction was continued long enough to give a copious precipitate of terephthalic acid. In the In cases in which no precipitation or no precipitate was obtained, the reaction was via a continued for an additional period of time to make sure that no precipitate formed in an acceptable cell space. The cases when there is no precipitation are in the table with the abbreviation

»K. P. «(no precipitate) stated: The precipitates formed were from the hot solution filtered off, washed with acetic acid at room temperature, dried and weighed. The investigation the melting point of the product produced from various experiments showed that the product Terephthalic acid with a high degree of purity. All reactions were essentially at atmospheric Pressure carried out.

From the values indicated in Table II, it is seen that the percent weight of the catalyst (calculated as cobalt bromide, based on xylene) at 26.2 ° / o ^ue SST> when the catalyst is used in a concentration of 0.05 M . This concentration is the minimum concentration used in the method according to the invention. The value given above is more than 2VjHIaI greater than the maximum concentration and 15 times greater than the most preferred metal bromide concentration, as it is indicated in the cited reference in column 3, lines 37 to 39. Incidentally, the equivalent amount of MnBr ₈ , which is 0.269 g, is 25.35 percent by weight of the xylene. This value is also 2VaHIaI greater than the maximum concentration and 15 times greater than the most preferred concentration, as stated in the cited reference.

Comparative example B

In order to demonstrate how critical the concentration of the catalyst is, reactions were carried out as described under the general procedure given above. The catalyst concentration was varied in steps from 0.01 M to 0.2 M, specifically at temperatures of 90 ^b G. In carrying out this experiment, the bromine-cobalt ratio was kept constant with one atom of bromine per atom of cobalt. The results are summarized in Tables III, IV and V.

Table V

Bath temperature 90 ⁰ C, acetic acid solvent.
(Br / Co-l: l)

Max. Temperature ..
Minute for 1 pcpt.
Total minutes ...

Yield (g)

Yield (%)

Rate,% yield /

Min

*) No precipitate.

Molarity of the catalyst
0.01 I 0.03 I 0.05

kP *)
313
0
0

90
217
237

0.1

0.6

0.003

94
50
68
0.49
29.5

0.43

Catalyst concentrations of 0.2 M were ^{not used at 90 and 120 °} C., since the catalyst is not completely soluble in the reaction mixture at these temperatures. However, it is at 130 ° C.

Comparative Example C

In view of the good results obtained with a catalyst concentration of 0.1 M, these catalyst concentration was used to examine the effect of the bromine to cobalt ratio at 8O ⁰ C and using acetic acid as solvent. The proportions of the reactants and the reaction conditions were described above in the general procedure. The results obtained are summarized in Table V. ·

Table VI
Bath temperature 8O ⁰ C, acetic acid solvent

0.1 / 1 0.5 / 1 Br-Co ratio
1/1 1.2 / 1 2/1 Maximum temperature
Minute for 1 pcpt
Total minute
Yield (κ) 81.5 *
90
122
0.41
24.7
0.20 87
25th
39
0.44
26.5
0.68 92
15.5
46
0.88
53.0
1.15 97
11
24
0.36
21.7
0.90 89
17th
80
0.16
9.6
0.12 Yield (%)
Rate,% yield / min

Table VII

2/1

Bath temperature

90 ⁰ CI ¹⁰⁰ ° ^c

Br-Co ratio
1/1 2/1

Maximum temperature . Minute for 1 pcpt .....

Total minutes

Yield (g) .....

Yield (%) ........

Rate,% yield / min

107
11 41

0.73 44.0

1.07

105 10 50

1.16 69.9

1.40

106 21 51

0.78 47.0

0.92

109.5
14.5
45

1.18 71.1

1.58

, _Λ,, . . ,. . . 5 Patent 2,833,316 are indicated. The used

Comparative Example D Metal compounds were cerium hydroxide (0.62 g)

In this experiment the effectiveness of others and vanadium pentoxide (0.23 g). To comparison

Metailkatalysatören investigated, as they are in the USA. Manganese acetate tetrahydrate (0.61 g)

'309623/106

used. The catalyst concentration was when HBr was used (0.63 ml, 0.322 g / ml). The others

0.1 M and the Br metal ratio at 1: 1. The conditions were as in the general procedure

Bindings were as in Trials 5 and 6 described.

where excellent results at low Table VIII shows the results at 90 ⁰ C, while

Temperatures and using cobalt- 5 rend Table IX those obtained at 133-138 ° C

metal were obtained. Bromine was presented in the form of results.

Table VIII
Bath temperature 90 ⁰ C, acetic acid solvent

manganese Metal in the catalyst
Cerium j nickel 90
(2)
151
0 Vanadium Maximum temperature ( ⁰ C)
Minutes for 1 rainfall
Total minitites 90
(n / a) *)
235
0 90
(D
235
0 90
(3)
151
0 Yield (g) *) No precipitate.

(1) The solution was a little cloudy from the start. At the end, 0.388 g of precipitate was from the Solution filtered off. This precipitate was identified as a catalyst because it does not melt

'still sublimed up to 400 ^{° C.} as

(2) An orange precipitate formed at the beginning of the reaction. At the end of the reaction, 0.157 g of precipitate was filtered off. This was identified as a catalyst because it could neither be brought to melt, nor ^{sublime up to 400 °} C. and was soluble in hot water.

(3) The initial solution was green and contained an orange precipitate. At the end of the reaction, 0.275 g of precipitate was filtered off from the solution. This was identified as a catalyst because it could not be, made to melt even up to 400 ⁰ C sublimated. The weight gain shows that an insoluble salt had formed with acetic acid, presumably a basic acetate.

Table IX
Bath temperatures 133 to 138 ° C, propionic acid solvent

manganese

Metal in the catalyst
Cerium I nickel

Vanadium

Maximum temperature ( ⁰ C)
Minute for 1 rainfall.

Total minutes

Yield (g)

Yield (%)

Rate,% yield / min ...

130
76
153
0.299
18th
0.12

(a) The solution was slightly cloudy and yellow from the start. At the end of the reaction, only a few milligrams of precipitate was obtained as a yellow solid as in the evaluation performed at 90 ⁰ C reaction.

(b) An orange precipitate formed from the start of the reaction. The precipitate (0.179) was filtered from the Reaktionsmischuhg and identified as catalyst because it could not be melted, even up to 400 ⁰ C sublimated.

(c) The solution was initially green with an orange precipitate. The precipitate (0.0967 g) was filtered off from the reaction mixture and identified as catalyst because it could not be caused to melt and not sublimated up to 400 ⁰ C.

It must be pointed out that the metals used in these experiments in column 2, Lines 21 to 24 of U.S. Patent 2,833,816 are mentioned and cited as catalysts

132
(b)

150
0
0
0

133

(C)
150
0
0
0

which should deliver particularly good results. The tested in these experiments metals cerium, nickel and vanadium were completely ineffective at 90 and 130 ^0C. Only manganese showed a very low activity, but only at 130 ^° C.

Comparative example E.

The following procedure was used in the following experiments:

A solution of the specified amounts of paraxylene, acetic acid and the metal bromine catalyst was placed in a reaction vessel fitted with a thermometer, reflux condenser and an inlet provided with a glass frit for the oxygen at the bottom of the vessel was equipped, so that the oxygen introduced ensured that the solution was thoroughly mixed. The reaction vessel was placed in a heating bath kept at a constant temperature. When the reaction mixture the temperature of the heating bath had been reached, was mit'der oxygen supply began. All of the precipitate formed was

19 20

filtered from the hot solution, with acetic acid the temperature of the reaction mixture was 125 Washed at room temperature, dried and kept from up to 129 ° C. After a total reaction time weighed. The experiments were conducted at atmospheric conditions of 90 minutes each time, and no precipitate formed. Printing carried out unless special pressure conditions are specified. 5 Comparative Example H.

A starting mixture was made as in Example 1

of USA.-Patent 2,833,816: In order to increase the combined effect of a

0.85 g of manganese acetate × 4 H _a O (equivalent to 0.6g ^Dru <? Determine ^{ks and "iner} higher temperature

anhydrous manganese acetate) ^{wurd "eme} _u starting mixture as in the first part

0.5 g ammonium bromide ¹⁰ J? ⁸ , ^V f ^suc ^ ^{B v} ™ det, i.e. the mixture is

48 8 s oara-Xvlol manganese-bromine catalyst. The mixture

125 g of acetic acid was placed in a modified reaction vessel,

in which the thermometer is through a thermocouple

The reaction mixture was brought to a reflux and through a thermocouple cup

temperature of about 108 ° C, and oxygen 15 was replaced. Heat was supplied by that

the tube was wrapped with a heating tape for 3 hours by the reaction mixture,

in a flow rate of 600 ccm / min. through- The entire reaction vessel was placed in a tube

directed. After this time, the thick-walled Pyrex glass could be poured into the

The reaction mixture did not form any terephthalate - both ends were closed with metal plates,

Acid can be determined, for example by ao which is sealed with Teflon seals and by

the absence of any precipitation was indicated. Brackets were held. These metal plates

At column 4, line 22 of U.S. Patent 2,833,816 were with a pressure gauge, a throttle valve

it is stated that cobalt bromide instead of and permanently attached openings for oxygen, nitrogen

Manganese acetate can be used. Therefore, fabric and the thermocouple cable were provided. the

the above experiment is repeated with the exception of 35 pressure inside and outside the reaction

that an equimolar amount of cobalt, namely a vessel, was through the open top of the con-

1.13 g of cobalt bformide hexahydrate (CoBr ₂ · 6 H ₂ O) balanced on a capacitor, which in the present case is used as a

Instead of manganese acetate and ammonium bromide, a gas cooling condenser acted. The device

has been used. After 3 hours, 0.1 g was initially pressurized using nitrogen

Obtained terephthalic acid. This means a total of 30 wagered. Oxygen was supplied at a pressure;

yield of about 0.13%. based on xylene. which was higher than the pressure of the reaction mixture

ν 1 · ι, u · ■ ^and d was controlled by means of a manually operated throttle

COMPARATIVE EXAMPLE T _{ventiIs regulated in the first 65} minutes

The general procedure was carried out. the temperature is kept at 150 to 160 ° C and

by using a starting mixture, then for 3s in the last 22 minutes at 160 to 166 ⁰ C.

corresponding to Example 24 of U.S. Patent During this time the pressure was about

2,833,816. This had the following composition: 2.74 kg / cm ^a . After this time, the

Manganese Acetate -4HO. Ig reaction mixture a precipitate in an amount

Njj g _r ² 0 75 ε ^of ® '^ S filtered off. This had a melting

p-xylene 75g ⁴ ° ^{point from} I ^{75 to} 179 ⁰ C. This shows that at least

Acetic acid 150 g ^em large part of which consisted of p-toluic acid

^s (melting point 179.6 ° C). To get the toluic acid from

For 3 hours, oxygen was separated in an amount of terephthalic acid, which could be in the product of 600 ecm per minute through the reaction mixture, the product was passed into hot vinegar while the mixture was suspended at a reflux acid in order to pick up the paratoluic acid temperature of about 108 ° C. It formed The product was filtered while hot, no terephthalic acid. 0.17 g of terephthalic acid were obtained (1.5% yield). The above experiment was repeated, but the results of Comparative Examples A to H were 1 g of cobalt acetate.4H ₂ O instead of Man- are summarized in the tables. It must be ganacetat.4H ₂ O used, according to the case 50 it should be pointed out that the Konzenspiel 27 of US Pat. No. 2,833,816. Even in tration of the catalyst metal in this case, no terephthalic acid was formed. in the particularly preferred concentration ranges _v,. ,. . . . _n , which are mentioned in U.S. Patent 2,833,816 for vergieicnsoeispiei u manganese (column 3, line 39). In order to determine the effect of a higher temperature in the range from 0.5 to 1.7 percent by weight of the reaction yield, the two aromatic starting materials, calculated as starting mixtures used in experiment B, were metal dibromide. The weight ratio is also different in that propionic acid was used in place of the acetic acid solvent and the p-xylene within the acid. In each experiment, particularly preferred ratios, namely with oxygen, were passed through the reaction mixture in a 60 1 to 2.5 parts of the acid solvent per part of the amount of 100 ecm per minute and the aromatic starting material (column 3, line 21).

Claims (1)

1 2 to see. This procedure can be used at low Claim: Temperatures are not carried out. If either arylmethyl or other aralkyl Process for the production of aromatic compounds in the presence of a cobalt catalyst. Carboxylic acids obtained. For example, if either which has two water toluene or ethylbenzene on the carbon atom in the presence of cobalt atoms is oxidized in the liquid state with ion according to the known processes, then any ozone-containing free acid is benzoic acid in both cases. So there are substance at elevated temperature in the presence of a cobalt and a bromine-yielding compound containing all carbon atoms on the alkyl side chain and from acetic acid to the atom that is adjacent to the benzene ring as a solvent, thereby split off . The ketones formed are usually characterized by the fact that the oxidation in a 15 only inconsistent intermediate products.
Temperature of 80 to 115 ° C, an atomic surprisingly one has been able to determine the ratio of bromine to cobalt as 1: 0.5 to 1: 1.2 that aromatic carboxylic acids and / or ketones in the catalyst and a molar concentration with good Yield and extremely high reaction of the cobalt compound in acetic acid from min- ing speed, e. B. in 15 to 60 minutes, at least 0.05 carried out. 20 under moderate reaction conditions with the help of a Process can be produced in which a Aralkyl compound with alkyl side chain in liquid State in the presence of a catalyst composed of cobalt, bromine and a carboxylic acid with free The invention relates to a method for producing 25 oxygen is oxidized. The oxidation of the aryl of aromatic carboxylic acids and / or aryl methyl compounds leads to aromatic carboxylic Alkyl ketones by oxidation of aromatic acids and the. other aralkyl compounds Compounds that have at least one alkyl aralkyl ketone on the ring. The invention therefore relates to a process for having two hydrogen atoms, in the liquid state 30 production of aromatic carboxylic acids and with optionally ozone-containing free acidic or aryl-alkyl ketones by oxidation of substance at elevated temperature in the presence of an aromatic compound that contains at least one cobalt and one bromine-yielding compound on the ring, an alkyl group which has two hydrogen atoms on the carbon-containing catalyst and acetic acid as the material atom, in the liquid solvent. 35 State with optionally ozone-containing free There are already a number of processes for the oxygen at elevated temperature in the presence of oxidation of the alkyl side chains of the aralkyl compounds a cobalt and a bromine-supplying compounds with the aid of oxygen to form a catalyst and dung-containing known from acetic acid of aromatic carboxylic acids. However, all of these conventional processes as solvents, which are characterized in that they are characterized, have the disadvantage that the oxidation is carried out at a temperature of the reaction rate at the currently 80 to 115 ^° C., an atomic ratio of bromine to the reaction conditions used, e.g. . B. low cobalt such as 1: 0.5 to 1: 1.2 in the catalyst and a reaction temperature, atmospheric pressure, molar concentration of the cobalt compound in the addition of catalysts, etc., acetic acid of at least 0.05 performs,
is extremely slow. When using 45 the catalyst for this reaction is so specific, atmospheric pressure, temperatures of about that it is largely ineffective if one leaves out or replaces the constituents with a 100 ° C and small amounts of catalysts. The elimination of 20 to 50 hours or more for the oxidation of bromine or the replacement of other various aralkyl compounds, e.g. B. xylene, required components, z. B. iron for cobalt, chlorine borrowed if you want to achieve good yields. Except for 50 or iodine for bromine, etc., make the catalyst o-, m- ineffective by the known processes. Ethylbenzene does not give acetophenone under the invention and p-alkyl compounds with the same conditions. Unexpected lightness oxidizes. With the aid of the known references, this reaction leads with approximately the same ease, and m- and o-xylene are more easily oxidized than p-xylene in the absence of oxidation of the methyl side chains of the o- speaking carboxylic acid. 55 m- and p-arylmethyl compounds, e.g. B. isomeric The xylenes described in US Pat. No. 2,833,816, to the corresponding carboxylic acids. The off-level process is clearly to be viewed as a high-temperature process - the «-methylene radicals of the alkyl side processes. In addition, since acetic acid is used as the chain of the aralkyl compounds with more than one solvent, the carbon atom on the side chain to a keto end is also a high pressure process, since the 60 group oxidizes instead of a carboxylic acid. If high pressures are required in order to oxidize the acetic acid, i.e. ethylbenzene, according to the invention, the reaction mixtures containing the acetophenone are kept liquid at high temperatures, a yield of at least 80%. The two essentials obtained in place of benzoic acid.
Features of this process, namely the high For carrying out the process according to the reaction temperature and the high reaction pressure, 65 Invention, an aralkyl compound and acetic are perfectly clear from the detailed description acid as a solvent and the catalyst from US Pat. No. 2,833,816 and from US Pat actually cobalt and bromine placed in a reaction vessel lent industrial implementation of this process and heated to the reaction temperature. Then it will be