DE1961919C - Process for the joint production of aliphatic carboxylic acids and aromatic carboxylic acids - Google Patents

Description

40

It is generally difficult to obtain aliphatic carboxylic acids by oxidative decomposition of the corresponding to produce secondary alcohols. For this purpose nitric acid oxidation is preferred. Oxygen oxidation on the other hand, requires rather severe conditions; the usual procedures only yield low yields.

For example, a process for the preparation of acetic acid by oxidation of the acetic acid ester of butanol- (2) with oxygen in the liquid phase instead of direct oxidation of the alcohol is described in Japanese patent application 9173/66. This process also requires strict conditions, for example a temperature of 190 ^° C. and a pressure of atm.

In the oxidation of aromatic hydrocarbons with two or more oxidizable alkyl groups a group can be relatively easily oxidized to the carboxyl group, while the one thus formed Monocarboxylic acid mostly resists further oxidation to a di- or polycarboxylic acid.

Ks is now known to circumvent this difficulty by using an aromatic monocarboxylic acid converted into their methyl ester and oxidized this methyl ester again, or an aromatic one Hydrocarbon under severe conditions in the presence of a bromine-containing catalyst or a aromatic hydrocarbon in the presence of a

low proportion of an oxidation accelerator

oxidize.

From the Japanese patent application 9654/66 it is known to add butanols as oxidation accelerators, but in a small amount compared to the amount of lower fatty acid used as a solvent. If the method, however, transmitted to the oxidation of p-xylene, the Terephthalsäureausbeute is only 77.6 ° / _0, while the partial pressure of oxygen must be from 7.03 to 70.3 kg / cm ^2, the process in terms of economy and safety makes unfavorable. Furthermore, it was confirmed by experiments that under the reaction conditions according to the claims of the above-mentioned patents, the butanol- (2) added to the reaction system is consumed during the reaction.

There has now been a process for the joint production of aliphatic and aromatic carboxylic acids by oxidation of alkyl aromatics mixed with a secondary, aliphatic alcohol with an oxygen-containing gas in the presence of a cobalt salt as a catalyst and optionally found in the presence of an aliphatic monocarboxylic acid, which is characterized in that one to the oxidation at a temperature of 100 to 160 ° C and at a molar ratio of alkyl aromatic aliphatic, secondary alcohol to aliphatic carboxylic acid such as 1: 2 to 4: ~ 2 to 12.

The advantages of the method according to the invention are as follows:

1. By the simultaneous oxidation of an aliphatic secondary alcohol and an alkyl-substituted one aromatic hydrocarbon, the oxidation reaction can be carried out under such mild conditions as in the Oxidation of the individual components is difficult to carry out in practice and can be done industrially valuable aliphatic carboxylic acids, such as acetic acid or propionic acid, and aromatic ones Carboxylic acids, such as benzoic acid, terephthalic acid, isophthalic acid, or phthalic acid, in high yields can be obtained.

2. The carboxylic acid is obtained in such a purity that a further purification process is mostly not necessary.

3. It is technically advantageous that an aliphatic carboxylic acid and an aromatic carboxylic acid can be formed simultaneously.

4. Since the oxidation process according to the invention is carried out under mild conditions, the reaction conditions can be regulated easily, and the implementation can be very safe be performed.

Examples of aliphatic secondary alcohols which can be used in the process according to the invention are isopropanol, Butanol- (2) or pentanol- (2), examples of alkyl-substituted ones which can be used in the context of the invention aromatic hydrocarbons are toluene, ethylbenzene, cumene, o-xylene, m-xylene, p-xylene, o-ethyltoluene, m-ethyltoluene, p-ethyltoluene, o-cymene, m-cymene, p-cymene, o-diisopropylbenzene, m-diisopropylbenzene, p-diisopropylbenzene, mesitylene and other polyalkylbenzenes. Furthermore, of course alkyl-substituted aromatic carboxylic acids, such as o-, m- and p-toluic acid and their derivatives, both

for example esters, can be used in the context of the invention.

In the process of the invention, by varying the feed ratio of alkyl-substituted aromatic hydrocarbon to aliphatic! secondary alcohol the ratio of aromatic carboxylic acid formed to the aliphatic carboxylic acid formed in desired Way can be varied. The preferred charge ratio of alkyl substituted aromatic car- ίο The acidic acid to the aliphatic secondary alcohol is 0.05 to 1 in weight ratio. If that Charge ratio is higher than 1, the yield of aromatic carboxylic acid is reduced, and the yield of aliphatic carboxylic acid also drops extremely. On the other hand, if the charging ratio is lower than 0.05, it becomes difficult to to effect the implementation in a sufficient manner.

Each value plays a role in the method according to the invention the presence of the alkylsubstiiuierien art> mutischen Hydrocarbons play an important role in the oxidation of the aliphatic secondary alcohol; when the alkyl-substituted aromatic hydrocarbon is absent from the reaction system, oxidation proceeds of the secondary alcohol hardly drops, as can be seen from »5 from Comparative Example 1 below. This is advantageous in the presence of the alkyl-substituted The main oxidizable aromatic hydrocarbons are the aliphatic secondary alcohols; ;; lls the secondary alcohol to the reaction system 3 » is added as an ester of an aliphatic acid, the aliphatic carboxylic acid is not obtained or only with an extremely low yield, and the yield of aromatic carboxylic acid is also low. These facts emerge from Comparative Example 2 below.

The method of the present invention can be effectively carried out without using any solvent however, it is preferred to use that aliphatic carboxylic acid as the solvent carried out, which arises as one of the products of the process according to the invention.

In the method according to the harvest, a Cobalt compound used as a catalyst. Preferred cobalt compounds are those in Reaction liquid-soluble compounds such as cobalt acetate, cobalt toluylate or cobalt naphthenate are used, however, other cobalt compounds can also be used.

D: The reaction can be carried out at normal pressure or at 5 <> increased pressure. The partial pressure of the oxygen is from 0.01 to 30 kg / cm ² , but the process according to the invention can also be carried out with a sufficiently high reaction rate even at a low partial pressure of the oxygen, which facilitates the regulation of the reaction conditions and provides a high level of safety offers. Taking these points into account, the preferred partial pressure of oxygen is less than 3 kg / cm ² . Although the reaction proceeds with a high yield even at the partial pressure of oxygen higher than 3 kg / cm ^{2 of} course, if the partial pressure of oxygen ^{becomes higher than 3 kg / cm a} , the mild reaction at the beginning is followed by a violent reaction which the Removal of the heat of reaction and the regulation of the reaction temperature made more difficult. Also could.! in this case, side reactions occur. Furthermore, the use of a high partial pressure of oxygen is accompanied by the disadvantage that the composition of the vapor phase in the reaction system is difficult to keep out of the explosive range, which increases the danger of the explosion along with the occurrence of the violent reaction. On the other hand, although there is no particular limitation on the lower limit of the partial pressure of oxygen, it is preferably higher than 0.01 kg / cm ² . The most preferred partial pressure is 0.1 to 3 kg / cm *.

The reaction temperature is in the inventive method between 100 and 16O ⁰ C. If the temperature is lower than 100 ⁰ C, the reaction proceeds slowly, thereby making the process industrially disadvantageous. On the other hand, if the reaction ^{temperature is higher than 160 °} C., side reactions occur, so that the yield of the carboxylic acids is reduced and the quality of the products is deteriorated.

The most advantageous combination of reaction temperature and partial pressure of oxygen is 100 to 160 "C with regard to the reaction temperature and less than 3 kg / cm ² with regard to the partial pressure of the oxygen. Under these conditions, the rate of absorption of oxygen is practically constant during the entire reaction and the reaction runs with a sufficiently high reaction speed.

Therefore, in the process according to the invention, the dissipation of the heat of reaction and the regulation the reaction temperature can be carried out fairly easily, the carboxylic acids can be in high yield using a relatively small reaction vessel and the process can be carried out safely be performed.

A highly enriched oxygen gas can be used as the oxygen-containing gas in the process according to the invention or a gas mixture of oxygen and an inert gas such as nitrogen or carbon dioxide is used however, air is generally preferred.

In the process according to the invention, the aliphatic carboxylic acid can be derived from the aromatic carboxylic acid formed Carboxylic acid can be separated off by filtration or distillation after the reaction has ended, the on Carboxylic acids produced in this way have a high degree of purity.

Furthermore, those remaining after the carboxylic acids have been separated off from the reaction mixture can be used Residues can be adjusted to a suitable composition and reused in the oxidation will.

This can result in repeated use of the unreacted substances or the lower oxidation products the yields continue to improve.

The process according to the invention can be carried out individually or continuously.

The following examples serve to further illustrate the invention.

example 1

In a flask equipped with a scrambled egg, a thermometer, an oxygen gas inlet, and a reflux condenser were charged 42.5 g of p-xylene, 59.3 g of bulanol- (2), 288 g of acetic acid and 9.96 g of cobalt acetate tetrahydrate. The flask was immersed in an oil bath of 100 ⁰ C and an oxygen

containing gas in an amount of 5 1 / hour. blown in, introduced. The autoclave was placed in an oil bath of

with stirring. After the start of blowing in the 12O ⁰ C immersed and an oxygen-containing gas

Oxygen gas was absorbed immediately with stirring up to a pressure of 30 kg / cm ^2.

of oxygen, and the absorption was afterwards. The oxygen gas was then poured into the

Finished 25 hours; the amount of the absorbed 5 system introduced so that the partial pressure of the acid

Oxygen was 52 I. substance was always kept at 30 kg / cm ² . To

After the reaction mixture had cooled down for 3 hours, the absorption of oxygen ceased.

the solid product formed is filtered off, with acetic acid The absorption properties of oxygen in

and further washed with ether, 61.0 g of this example being graphically in the drawing

Terephthalic acid shown as a pure white powder in an aus io.

91.8% were obtained. After cooling the reaction mixture, the filtrate became

2.5 g of p-toluic acid were recovered. Filtered on the solid product formed with acetic acid

Based on the analysis of the mother liquor, it was washed and dried, with 12.68 g of terephthalic

total acetic acid content of the liquid 328.2 g. The acid was obtained as a pure white powder. the

Conversion of 2-butanol was 61.3% and the total amount of acetic acid in the mother liquor was

Selectivity for the formation of acetic acid 80.1 g, and the selectivity for acetic acid, based

68%. on the converted butanol- (2) was 82.1%.

Comparative example 1

Example5
The procedure was as in Example 1, but 20

no p-xylene added; There was no absorption in the same reaction vessel as in Example 4.

of oxygen observed even after 8 hours. were 17.24 g of p-xylene, 31.97 g of bufanol- (2), 52.23 g

For example 2 acetic acid and 2.00 g cobalt acetate were introduced and

^e then the same procedure as in Example 4 while

The procedure was as in Example 1, but felt through for 35,190 minutes. By the operator, 92.9 g of butyl (2) acetal used in place of the alcohol was terephthalic acid in a yield of 94.5% and the amount of acetic acid was changed to 240 g. receive. The conversion of butanol (2) was. After 32 hours, the absorption of oxygen ceased to be 88.9% and the selectivity of acetic acid ceased. By processing the products, as in the case of -86.0%.
game 1, 53 g of terephthalic acid were obtained. The 30th

The amount of butyl (2) acetate was 15%, and Comparative Examples 3 and 4 were used

no acetic acid was obtained.

"· · L, The same procedure as in Example 4 was followed.

^p repeated, with 17.24 g of p-xylene. 52.23 g acetic acid

In the same flask as in Example 1, 35 and 2.00 g of cobalt acetate in Comparative Example 3 and 42.5 g of p-xylene, 118.6 g of butanol- (2), 240 g of acetic acid, 17.24 g of p-xylene, 7 , 99 g of butanol (2), 52.23 g of acetic acid and 7.1 g of anhydrous cobalt acetate were introduced. The cobalt acetate and 2.00 g in Comparative Example 4 was verKolben immersed in an oil bath of 100 ⁰ C were spent. The oxidation was 180 minutes and oxygen gas in the mass in an amount of in Comparative Example 3 and 210 minutes in Ver-5 i / h. blown in with stirring. The absorption 40 same example 4 carried out. In the first case, the oxygen was complete after 51 hours, and the yield of terephthalic acid was 30.2% and in the case of working up the product, as in Example 1., the second case was 66.6%. In the second case, 60.5 g of terephthalic acid were also obtained as a white powder with conversion of butanol- (2) SS.9%, while that of a yield of 91%. The total amount of selectivity for acetic acid was only 5.0%.
of acetic acid in the reaction product liquid 45
was 335.9 g. B is ρ ie 1 6

The conversion of butanol- (2) was 67.0%

and the selectivity to acetic acid 70.5%. into an autoclave of the stirring type of 200 m

Capacity with inlet for oxygen

B e i s ρ i e 1 3 5 <> and reflux condenser were £ 8.60

p-xylene, 24.0 g butanol- (2), 52.2 g acetic acid unc

Introduced into an autoclave of 300 ml of Rührlyp lampholder 2.00 g Kobaltacetattetralivdrat and dei assets, 8.6 g p-xylene, 16.0 g butanol (2), g autoclave in a ge at a temperature of 130 ⁰ C 10.4 acetic acid , 6.0 g cobalt naphthenate and 50 ml holding oil bath submerged. Introduced under vigorous stirrer benzene and the system at 130 ⁰ C under 55 was at an oxygen pressure of 30 kg / cm ² that the total pressure at 2 kg / cm ^{2 G.} geerhitzt stirring introduced the oxygen gas into the autoclave so on. After 10 hours the autoclave was shut off. On the other hand, the gas was cooled in the deir and the reaction product was filtered, whereby 9.7 g of the autoclave was discharged through the reflux condenser in an amount of terephthalic acid obtained in a yield of 79% from 3.5 l / min (at 25 ^° C. and 1 am). Afterwards. The conversion of butanol-2 was 80% after the introduction of the oxygen gas had started and the selectivity for acetic acid was 58%. the oxygen was absorbed immediately

1.3 g of p-toluic acid were obtained from the filtrate. substance was 4.6 l / sid. (at 25 "C and 1 atm) practical Example 4 throughout the process. This behavior

65 is shown graphically in the drawing. Nacl

It was cooled in an autoclave of the stirring type made of stainless steel for 5 hours, the oxidation product steel were Kr> 2 μ p-xylene, 23.98 g Bulanol- (2), removed, washed thoroughly with acetic acid and 52.23 y I ssipsiiiue and 2.0; ■ Cobalt acetate lctrahydral pel rock m: l, with 12.54 g of terephthalic acid as leii

white powder obtained in a yield of 93.2% Example 9

became.

The analytical results of the Mutlerlauge showed that the same procedures as in the example were used

that the conversion of butanol- (2) was 85.4%. but 31.1 g of acetic acid instead of 52.2 g and the selectivity to acetic acid was 81.8%. 5 used. The apparent absorption rate

speed of oxygen was 5.91 / hour. during the

Example 7 of the entire reaction period. The oxygen content

in the vented gas was 5 to 8 volume percent.

It has 6 was the reaction product after 5 hours Umwiedcrholt, wherein the total pressure at 5 kg / cm ² worked up the same method as in Example io reduction as in Example 6, to obtain pressure was changed, but the Anfangssauer- terephthalic acid in a yield of 94, 3%. The material absorption is only 2.6 1 / hour. and the rate of conversion of butanol- (2) was 84.5%, and the rate gradually to 17.6 l / hr. was increased. This selectivity to acetic acid was 85.8%.
Behavior is shown in the drawing. By up

processing of the reaction product as in Example 6 15 '

The same procedure as in Example 8 was obtained in the yield of terephthalic acid

92.5% received. The conversion of butanol- (2) is repeated, but the amount of butanol- (2) increases

was 88.3%, and the selectivity for acetic acid 16.0 g and the amount of acetic acid to 33.1 1: ge

was 75 8%. changes. The apparent absorption velocity '; "wedge

π · ■ ι ο ^{20 of} the oxygen was 6.21 / h, and the Sauer-L, ff ·

^Example content in the discharged gas was 4 to 7Vo-m-

The same procedure as in Example 6 became percent. If the product was repeated after 5 hours iv, but using air instead of oxygen gas as in Example 6, the result was obtained. 'r used, the total pressure in the system at 10 kg / cm ^2, the terephthalic acid kept with a yield of 95 ₀ overpressure and the gas in the autoclave in a 25 The conversion of butanol (2) was 88.9%. 't amount of 30.2 1 / hour. drained. The apparent selectivity for acetic acid was 82.2%.
Rate of absorption of oxygen

4.3 l / h during the entire reaction period. »C 1 s ρ 1 e 1 11

Analysis of the vented gas showed that the working procedure of Examples \\ i-. "

Oxygen content was 8 to 9 percent by volume. 30 fetches, but 8.65 g of m-xylene and 24.1 g of Pcntaiu -

After the reaction has been carried out, it is used for 5 hours. The apparent absorption velocity.
the reaction product was added as in Example 6, the oxygen during the reaction was 4.81
is working. The yield of terephthalic acid was equal to that of the oxygen content of the vented gas
93.1%, the conversion of the butanol- (2) was 7 to 8%. After a reaction time
S4.8%! and the selectivity to acetic acid was 80.8%. ^{For 5 hours} the product was as in Example 6

When 1 g of the terephthalic acid obtained in this way worked, isophthalic acid was in an Ausl
acid obtained in 25 ml of a 14% aqueous ammonia of 95.2%. The analysis of the reaction solution
^ _e l _{est wur (} each and the optical density of the solution at resulted in a conversion of pentanol- (2) of S6.0 moo
a wavelength of 380 Γημ and a cell length cent, acetic acid of 6S, 8 mol percent, based
was measured from 5 cm, the optical density was 4 ° the introduced pentanol (2). and propionic acid
^ λλτ, 60.4 mole percent.

1 sheet of drawings

Claims (5)

Patent claims: 1. A process for the joint production of aliphatic and aromatic carboxylic acids by oxidation of alkyl aromatics in a mixture with a secondary, aliphatic alcohol with an oxygen-containing gas in the presence of a cobalt salt as a catalyst and optionally in the presence of an aliphatic monocarboxylic acid, characterized in that the oxidation is carried out at a Temperature of 100 to 160 ^° C. and with a molar ratio of alkyl aromatic to aliphatic secondary alcohol to aliphatic carboxylic acid such as 1: 2 to 4: ~ 2 to 12. 2. The method according to claim 1, characterized in that the oxidation is also used of butanol- (2) or pentanol- (2) as an aliphatic secondary alcohol. ao 3. The method according to claim 1 or 2, characterized in that the oxidation under Use of p-xylene or m-xylene as alkyl substituted aromatic hydrocarbon and butanol- (2) as an aliphatic secondary alcohol performs. 4. The method according to claim 1 to 3, characterized in that the oxidation is carried out at an oxygen partial pressure of less than 3 kg / cm ² . 5. The method according to claim 1 to 4, characterized in that the oxidation using the same aliphatic carboxylic acid as produced by the reaction as Solvent carries out.