DE1618717B2 - PROCESS FOR PRODUCING AROMATIC CARBONIC ACIDS - Google Patents

Description

The invention relates to a process for the preparation of aromatic carboxylic acids by liquid phase oxidation aromatic compounds with at least one alkyl, aldehyde or alcohol radical as Substituents with molecular oxygen in the presence of a heavy metal and containing bromine Catalyst system, optionally in the presence of a lower fatty acid having 2 to 4 carbon atoms in the molecule under conditions of high temperature and elevated pressure, which is characterized in that the liquid phase oxidation is carried out in the presence of silicone

The silicone, which according to the invention at the same time in the liquid phase reaction system as a promoter in addition to the Heavy metal and bromide should be present as a catalyst, contributes to increasing the reaction rate.

Since the silicone can be used to increase the reaction rate in the invention For the reaction system and method drawn, it is believed that it acts as a promoter for the reaction system and procedure works, but the exact mechanism of its mode of action has not yet been clarified However, a comparison of the results of the present method with those of reactions which were carried out in exactly the same way except that the present Silicone has been omitted, with a view to conversion within a predetermined period of time, the purity and hue of the product and the reproducibility of the reaction show that the through the invention achievable improvement from the industrial From a standpoint, it is extremely valuable

The silicone can also be called a siloxane and has that represented by the following formula Basic structure:

I I

—Si — O — Si—

More precisely, the known silicones include, in addition to the compounds of low molecular weight simple structure, such as B. hexamethyldisiloxane and octamethyltrisiloxane, polysiloxanes with higher molecular weights. Silicones having molecular weights which vary over a considerably wide range can be used in the practice of the invention will. As substituents to be connected to the silicon atom are hydrogen, alkyl radicals, such as. B. Methyl and ethyl radicals, phenyl radicals and halogenated alkyl radicals mentioned among the listed substituents are those that are chemically relatively stable, such as the methyl group or phenyl group, particularly preferred, however, the substituent is not critical. Furthermore, both chain-like siloxanes and cyclic siloxanes can be used. The siloxane compounds used according to the invention are at Room temperature liquid or creamy, and consequently vulcanized silicone rubber and silicone resin are with high molecular weight unsuitable for the purpose

That is, vulcanized silicone rubber and silicone resin fall within the scope of the invention specified »silicone« are excluded.

For the process according to the invention, silicones are used under the reaction temperature and pressure conditions are liquid, including those with molecular weights of normally 400 or above and which are liquid under the reaction temperature and pressure conditions, preferably silicones that to become gaseous under the above conditions can also be used provided a additional means is provided to condense the gaseous evaporated silicones and that Condensate returned to the reaction system.

Specific examples of silicones useful in the invention include octamethyltrisiloxane, Methylhydropolysiloxane, methylalkylpolysiloxane (where the alkyl group has 1 - 10 carbon atoms), Methylphenylpolysiloxane, diethylpolysiloxane and methylfluoroalkylpolysiloxane (wherein the fluoroalkyl group has 1-4 carbon atoms).

According to the invention, the silicone compound is left in the liquid as described above Reaction system simultaneously with the catalyst system in an amount of about 0.0001-2% by weight, preferably 0.001-0.2% by weight, based on the aromatic starting compound. In the Amount below the above lower limit, promoter performance tends to drop, and on the other hand the use of an amount greater than the upper limit in no way contributes to the rate of the reaction to increase. For these reasons, the silicone is used in amounts within the range given above Range applied with satisfactory results

The aromatic starting compounds suitable for the invention include e.g. B. the connections with at least one, preferably 1-3, oxidizable aliphatic substituents. The aromatic ring can be either the benzene or naphthalene ring, with the benzene ring compounds being preferred.

As some of the specific examples of such starting aromatic compounds, the following can be mentioned listed are: alkylbenzene, such as toluene, ethylbenzene, cumene, xylene, diisopropylbenzene and Pseudocumene; aromatic alcohols and aldehydes, such as. B. benzyl alcohol, benzaldehyde, methylbenzyl alcohol and terephthalaldehyde. Examples of compounds · which simultaneously have other substituents that are not on the Participate in oxidation reaction, are aromatic carboxylic acids, such as toluic acid and alkylbenzene derivatives, like chlorotoluene.

Among the compounds listed above as examples are for example toluene, ethylbenzene, cumene, xylene, diisopropylbenzene, pseudocumene and toluic acid the preferred starting materials.

The starting materials listed above can be used either alone or as a mixture of several specific compounds can be used.

The invention can be particularly advantageously applied to the preparation of the corresponding aromatic dicarboxylic acids, for example terephthalic acid, from dialkyl-substituted aromatic compounds, e.g. B. p-xylene, be applied.

The reaction takes place according to the known liquid

phase oxidation method in which the oxidation occurs with the introduction of molecular oxygen into the liquid phase reaction system in the presence of the catalyst system under the high temperature and elevated temperatures Printing conditions progresses

In the following the invention is explained by means of working examples together with control examples for comparative purposes

Examples 1 to 6 and Comparative Examples 1 and 2

In a titanium autoclave equipped with a stirrer, reflux condenser and air inlet tube, p-xylene, acetic acid, the catalyst system and silicone as a promoter were placed. The reaction is carried out by blowing air as molecular oxygen into the liquid phase zone while keeping the above substances under heating. During the reaction, the exhaust gas was drawn off through the cooler in order to keep the pressure in the reaction zone constant at 25 kg / cm ² . By analyzing the oxygen concentration in the withdrawn gas, the

Table I. Completion of the reaction can be determined.

After the completion of the reaction, the air supply was stopped and the reaction system was cooled and filtered to separate the solid reaction product.

The results are in Table I below

listed, in which the results of the comparative tests, which were carried out in exactly the same way as in the Examples are also listed with the exception that no silicone was used.

p-xylene
(G)

Acetic acid (g) catalyst (G)

Promoter (G)

React. Temp.

CQ

example 1 Example 2 Example 3 Example 4 Example 6

Comparative example 2

40

40

40

40

50

50

300

300

300

300

Comparison 40 300 example 1 Example 5 50 200

200

200

Manganese acetate (0.30) methylpolysiloxane (0.04) 220 Cobalt Acetate (0.15) Wt Mol: 5000 Ammonium bromide (0.20)

the same. methylethylpolysiloxane 220

(0.04) Mol Wt: -5000

also methylphenyl-220

polysiloxane (0.04) mole weight: 20000

likewise. Octamethyl-220

trisiloxane (0.40) Mol Wt: -200

the same

the same

desgl. Methylfluoräthyl polysiloxane (0.06) Mol-Gew.:-20000

220

Manganese naphthenate (1.0) diethylpolysiloxane (0.08) 190 cobalt naphthenate (0.50) mole weight: -5000 Tetrabromoethane (0.30)

210

210

Table I (continued)

Air supply Time b. to the Yield to Purity d. receive. APHA color speed Quit d. Terephthalic. Terephthalic acid worth d. he reaction hold Terephthal acid (l / h) (min) (Wt .-%) 350 30th 92 99.9 30th 350 29 91 99.9 33

example 1
Example 2

5 Air supply 16 18 7 17th Yield to 6th APHA color speed Terephthalic. worth d. he
hold continuation Purity d. receive. Terephthal Time b. to the Terephthalic acid acid (I / h) Quit d.
reaction (Wt .-%) 350 91 30th 350 90 34 350 (min) 86 99.9 70 Example 3 350 30th 89 99.8 50 Example 4 350 31 91 99.0 40 Comparative example 1 350 38 85 99.2 80 Example 5 36 99.6 Example 6 33 98.5 Comparative example 2 42

In the table values, the purity of the terephthalic acid was determined by weighing the terephthalic acid as Barium salt determined The APHA color value (APHA - American Public Health Association) of terephthalic acid is determined according to the determination method ASTM-D 1209-54. 2.5 g of terephthalic acid are dissolved in 100 ml of 1N sodium hydroxide solution and then the color of the resulting solution was measured.

Table II

Examples 7-13 and Comparative Examples 3-6

Example 1 was repeated except that the nature of the starting aromatic compound was changed. The results are given in Table II.

Aromat.

Initial

Connection

(G)

Acetic acid catalyst

(G)

(g) promoter

(G)

Reaction temp.

CQ

Example 7 Example 8 Example 9

Comparative example 3

Example 10

Comparative example 4

Example 11 Toluene (100) - ^a ) cobalt naphthenate (1.0)

Manganese naphthenate (2.0) Benzyl bromide (0.5)

Cumene (50) 200 manganese acetate (0.50)

Ammonium bromide (0.40)

Manganese bromide (0.40) cobalt acetate (0.15)

m-xylene (40)

the same

p-diisopropylbenzene (40)

the same

Pseudocumene (40)

200 the same.

300 manganese bromide (0.80)

300 the same

250 cobalt naphthenate (0.50)

'' Manganese naphthenate (1.0) tetrabromoethane (0.40) Methylphenylpolysiloxane (0.08) Mole weight: ~ 20000 methylethylpolysiloxane (0.04) Mol Wt: -5000

Methylphenylpolysiloxane (0.04) Mol Wt: 20000

200

190

220

220

Methylpolysiloxane (0.05) 210 mole weight: -5000

210

Methylpolysiloxane (0.06) 210 mol wt: -5000

Table II (continued)

Air supply speed

(l / h)

Time b. to finish d. reaction

(min)

Yield of carboxylic acid

(Wt .-%)

Purity d. APHA color

receives Carl onwert d. he-

acid

holding carboxylic acid ^b )

Example 7 Example 8

400 400

35 40

Benzoic acid (96) benzoic acid (90) 99.8 98.1

100

continuation

Air supply speed

(I / h)

Time b. to the Hccnd. d. reaction

(min)

Yield; in carboxylic acid

Purity d. receive. Carboxylic acid

Λ PI I Λ color value d. non-toxic carboxylic acid ^b )

Example 9 350 Aromat. 27 Time Isophthalic acid (95) 100 Promoter hold (94) 99.8 (80) 97.8 40 Comparison 350 Initial 34 Isophthalic acid (88) 99.1 Carboxylic acid Terephthalic acid (89) 98.8 70 example 3 Connection Terephthalic acid Example 10 400 (G) 45 Terephthalic acid (75) 96.6 (G) 200 Comparison 400 Fseudocurnol 54 Terephthalic acid (67) 92.3 (%) 350 example 4 (40) Trimellitic acid (84) 93.7 Example 11 350 40 Trimellitic acid (92) 98.6 Terephthalic acid 160 Table II (continued) p-toluic acid Methylpolysiloxane (0.04) (40) catalyst Mol Wt: -5000 Reaction Temp. the same - (G) (C) Comparison p-methylbenzyl Cobait naphthenate (0.50) Methylphenyl poly 210 example 5 alcohol (40) Manganese naphthenate (1.0) siloxane (0.05) Tetrabromoethane (0.40) Mol Wt: -5000 Example 12 Table II (continued) Cobait naphthenate (0.30) 200 acetic acid Manganese acetate (0.30) b. z. Yield of carboxylic acid purity d. he- Ammonium bromide (0.20) Quit, d. Comparison the same reaction 200 example 6 (G) Example 13 250 Cobait naphthenate (1.3) 210 Ammonium bromide (0.30) Comparative example Example 12 250 (min) (wt%) Comparative example 48 APHA color Example 13 24 worth d. he 250 29 hold 38 Carbon 200 acid ^b ) 300 45 Air supply 80 speed 160 (l / h) 5 350 300 6,300 350

^a ) To shorten the introduction time, 5 g of benzoic acid were added.

^b ) The APHA color value (APHA - American Public Health Association) of the carboxylic acid obtained is determined according to the determination method ASTM D-1209-54. 2.5 g of the carboxylic acid are dissolved in 100 ml of aqueous solution containing equivalent amounts of sodium hydroxide, and the color of the solution obtained was then measured.

^c ) Due to the mixture of the catalyst residue, no color value was obtained according to the determination method ASTM D-1209-54.

709 537/21

Claims (1)

Claim: Process for the production of aromatic carboxylic acids by liquid phase oxidation of aromatic compounds with at least one alkyl, aldehyde or alcohol residue as substituents with molecular oxygen in the presence of a heavy metal and bromine containing catalyst system, optionally in the presence of a, ₀ lower fatty acid with 2 to 4 carbon atoms in the molecule under conditions high temperature and elevated pressures, characterized in that the liquid phase oxidation is carried out in the presence of silicone.