DE1468824A1 - Oxidation of alkyl aromatic hydrocarbons - Google Patents

Description

PATENT LAWYERS

DR-ING. BY KREISLER DR.-ING. SCHÖNWALD DR.-ING. TH. MEYER DR, FUES

COLOGNE 1, DEICHMANNHAUS

γ · τ V-,,

Cologne, ¹ . ΐ | .7 _β 1965 AvK / Ax

Princeton Chemical Research, Inc., 14 D 8 8 2 4 PO Box 652, Princeton ,. N. J. (V.St.A.).

Oxidation of alkyl aromatic hydrocarbons

The invention "relates to the catalytic oxidation of alkyl aromatic hydrocarbons, especially the catalytic oxidation of alkyl aromatic hydrocarbons with at least 2 adjacent alkyl radicals, which are preferably methyl radicals, to form acid anhydrides. A preferred embodiment of the invention relates to the catalytic oxidation of durol to pyromellitic dianhydrides

It is known that alkyl aromatic hydrocarbons by reaction with oxygen-containing gases, such as air, at elevated oil temperature in the presence of an oxidation catalyst, ZeB. a yanadine oxide supported catalyst, can be catalytically oxidized. If the alkyl aromatic hydrocarbon contains two adjacent alkyl substituents on the ring, which are preferably lower alkyl radicals, the oxidation reaction leads to conversion to the anhydride. If the alkyl aromatic hydrocarbon contains two groups of two adjacent alkyl substituents on the ring, the oxidation leads to the conversion to the dianhydride.

909816/0701

It has already been proposed to catalytically oxidize Durol in this way to pyromellitic dianhydride. However, this catalytic oxidation process ^ proved not to be technically Nooh be economically interesting, and pyromellitic is Z _{0 0} currently manufactured Nooh after expensive, technisoh difficult and dangerous sulfuric acid oxidation process "

The subject of the invention is an "improved and technisoh more interesting and effective process for the catalytic oxidation of alkylaromatic hydrocarbons to the corresponding anhydrides, in particular a process for the catalytic oxidation of Durol to pyromellitic dianhydride.

According to the invention it has been found that alkylaromatic Catalytically oxidizes hydrocarbons with an oxygen-containing gas more effectively and / with higher yield can be achieved when the oxidation is carried out using a vanadium catalyst containing niobium. The ratio of mob to vanadium in the catalyst can be between 0.05 and 1 g atom of niobium per g atom of vanadium and is preferably about 0.1-0.3 g-atom of niobium, each g-atom vanadium.

The catalyst can be in any suitable or customary solid form, e.g. in the form of PeIMa, granules, grains of thread etc, preferably on a solid support such as aluminum oxide, Silicon carbide, magnesium oxide or other known or customary carriers are present · When using a The carrier material is preferably in amounts of 75-99% by weight, in particular 85-95% by weight, of the total catalyst available.

The catalyst is preferably in the form of an ester bed is used and has a particle size for these two oils in the range of 1.6-13 mm, precautionary measures from 3.2-6.4. asu

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The catalyst can also be produced in finely divided form for use as a fluidized bed. The particle size distribution in this case is "for example in the range from 10-400 yes _e

The "preferred catalysts used for the purposes of the invention are prepared by drying a solution containing the vanadium and mob components, or by drying such a solution in the presence of the carrier. For example, the required amounts of the vanadium in the form of vanadium pentoxide and The niobium in the form of niobium oxalate can be dissolved in an oxalic acid solution. Solid granules of the carrier, e.g. pure α-aluminum oxide or silicon carbide or any other carrier are then added to the oxalic acid solution are vanadium-niobium catalyst coats the particles of the carrier "the catalyst may then in air at a temperature of for example between 300 and 55O ⁰ G calcined _e It is also possible to evaporate the solution of oxalic acid in the absence of the carrier to dryness and the obtained To grind catalytic solids, to granulate them - and to use them as such en or to be mixed with the carrier material before granulating ,, Preferably, a carrier material with a small inner surface is used in each case. "

Activators, e.g. alkali metals and alkaline earth oxides and sulfates or phosphates, boron, silver, manganese or phosphorus * Antimony or arsenic can be used as soluble materials Vanadium-niobium-oxalate mixture can be added. The amount of the activator is between 0.1 and 5 $ the amount of Niobium plus vanadium in the catalyst »The ratio of niobium to vanadium can vary so that the g atomic ratio of Nb / V in the catalyst varies between 0.05 and 1, preferably between 0.1 and 0.3 «,

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The exact nature and structure of this way formed catalyst are not known, however assumed that an inorganic polymer is present which contains the vanadium and niobium. Without a commitment is intended to be of a particular shape or structure, the catalyst thus formed is in referred to as fiobvanadate in this specification.

Any known alkyl aromatic hydrocarbons which are catalytically oxidizable can be used as starting materials. The preferred group of alkyl aromatic hydrocarbons is formed by the tetraalkylbenzenes which contain lower alkyl radicals. The catalytically ^ oxidation tetraalkylbenzenes this leads to the formation of the corresponding acid anhydrides "The alkylaromatisohen hydrocarbons preferably have the pairs of alkyl substituents on adjacent carbon atoms of the ring ο Preferably are the lower alkyl radicals, z" B. Methyl residues β

As examples of alkyl aromatic hydrocarbons, which can be oxidized according to the invention may be mentioned: o-xylene, durol, octahydroanthracene »tetraethyl or tetrapropylbenzene, ethyltrimethylbenzene, diethyldimethylbenzene, Propyltrimethylbenzene and in general Compounds of the formula

where R , R ₂ , R ^ and R ^ can be hydrogen, methyl, ethyl or propyl radicals, with the exception that either R ₁ and R ₂ or R ^ and R must be methyl, ethyl or propyl radicals »octahydrophenanthrene ., Anthracene and phenanthrene 'can also be oxidized according to the invention,

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Preferably, Durol is used as the alkyl hydrocarbon to produce pyromellitic dianhydride, Ootahydroanthracene can also be used for this purpose «

Am mixture of the inserted alkylaromatisohen hydrocarbon, Z ₀ B. of durene, and the oxygen-containing gas is passed over the catalyst., While maintaining the temperature between 400 and 600 ⁰ O, preferably between 400 and 500 ° 0 and especially at a substantially lower 5Ö0 ° G is kept within this range. The reaction can be carried out under reduced pressure, normal pressure or elevated pressure. For example, pressures may range be applied "The contact time of the gas stream with the catalyst can vary depending on temperature and pressure between opi and 2 seconds _e are ron about 0.5-30 atm", preferably between 1 and 5 Atm, ""

Air is preferably used as the oxygen-containing gas, however, mixtures of oxygen and any other diluents such as water vapor, Nitrogen or carbon dioxide, can be used. The hydrocarbon used, e.g. Durol, must be in a Amount of about 0.01-1.5 Mo1- $ be present in the gas stream.

The reaction can be carried out in any conventional reactors in which gases are passed over a catalyst and which are provided with suitable temperature control. You can for example in a reaction tube or a chamber in a tubular reactor ο «the like ,, in which the catalyst is arranged, using a heat transfer medium, e.g. a liquid, for temperature control.

The reaction product may be in any known manner, for example, by condensation _e, be isolated and purified with solvents ^ p ^ urch washing, in the usual manner "

909818/0701

For example, pyromellitic dianhydride can by. Condensation, for example _e in a cooler which is kept at a temperature between 20 and 35O ⁰ O, are deposited. Are the pyromellitic dianhydride can then ο by scraping, or the like, "removed from the condenser and in an organic solvent such as p-dioxane, diacetone alcohol, cellosolve acetate, diphenyl ether, 1,2-dimethoxyethane, various ketones like o _e" dissolved, followed by the solution is decolorized with activated charcoal, the activated charcoal is removed, the pyromellitic dianhydride recrystallized by cooling and removed by centrifugation, filtration. The solvent can of course be recovered and recycled. It can also be used for the direct removal of the condensed pyromellitic dianhydride from the cooler by passing it directly through the cooler. With continuous operation, it is useful if there are two or more alternately operated coolers, _etc.

The crude pyromellitic dianhydride can also be prepared by washing with water at a temperature between about 32 and 150 be won,. The water-insoluble products will be removed by filtration or centrifugation, and the aqueous solution is decolorized with activated charcoal. The coal is removed and the solution is left to cool to crystallize the pyromellitic acid, which is then passed through Centrifugation is separated and dehydrated. The crude pyromellitic dianhydride obtained can be obtained by recrystallization further cleaned as described above »

Another, preferred method of obtaining the Reaction products, e.g. pyromellitic dianhydride, from the reaction gases become the residual gases from the reactor cooled to a temperature below the solidification point of the pyromellitic dianhydride and the so formed solid particles of the dianhydride on a filter cloth

909816/0701

H68824

caught and won "

example 1

A catalyst containing niobium vanadate with an Nb / V atomic ratio of 0.18 and aluminum oxide as a carrier was prepared as follows: 60 g of Y ₂ Oc were carefully dissolved in 149 g of oxalic acid in water at about 50 ° C. A solution 63.4 g of niobium oxalate in water were slowly added to the vanadium oxalate solution "Then 150 g of an acid-leached and dried aluminum oxide (alundum) were added", the mixture was evaporated to dryness while being rolled ", the supported catalyst became 1 hour Oaloinated at 500 ^{0 O.} This catalyst was used for the oxidation of durol to pyromellitic dianhydride. 50 ml of the catalyst were placed in a reactor tube with an internal diameter of 19 mm and which had an axial thermocouple pocket. 70 ml of uncoated alundum were placed over the catalyst as a preheating zone «

Over the catalyst were 6.0 ml of Durol and hourly 542 1 air. The following yields were obtained:

Temperature, ⁰ G. Pyromellitic dianhydride (PMDA) t wt .- ^

450 89

500 101

Example 2

A catalyst with the same lib / V ratio as that Catalyst prepared according to Example 1 was prepared in the same manner with the exception that SiO was used as Carrier was used. When the catalyst was tested in the same way, the same yields were achieved «

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Example 3

A. Catalyst with the same Nb / V ratio as the catalyst prepared according to Example 1 was prepared in the same manner except that no carrier was used _o The catalyst solids were ground and granulated and tested in the same manner o The same yields of PMDA were received

Example 4

The experiment described in Example 1 was repeated with catalysts whose Nb / V ratios between Oj and 1.0 varied. The results obtained are shown in the table below.

NbA ratio Temperature, C Example 5 Weight -96 PMDA 0.1 500 101 0.18 500 10t 0.36 500 89 '1.0 525 50

The crude PMDA obtained with the catalyst prepared according to Example 1 was obtained by direct condensation “5.0 g were deposited from the residual gas of the reactor dissolved in 60 g of p-dioxane at the reflux temperature. the hot solution was treated with 0.5 g of charcoal * The charcoal was filtered off. The solution was allowed to cool and obtained white crystals. These crystals were dried under vacuum to obtain 4.1 g of PMDA whose purity was over $ 99 was determined by the neutralization equivalent and vapor phase chromate o— graphics "

Example 6

Raw PMDA was prepared with that according to Example 1 Get the catalyst as follows: «The reactant gases of the reactor were washed with hot water, leaving a dark yellow

909816/0701

_Β solution was obtained after removal of insoluble products through! Filtration, the hot solution with charcoal was treated, filtered hot and allowed to cool · The crude pyromellitic was separated by filtration and dried. According to the neutralization equivalent, it had a purity of $ 96. The crude acid was dehydrated under vacuum at temperatures of 150-25O ⁰ O. There were spots in the crude anhydride that looked charred. The crude anhydride was recrystallized from p-dioxane to give a light colored product has been • obtained, which was identified as virtually pure PMDÄ "By recrystallization of the crude anhydride from methyl isobutyl ketone _t was also obtained a practically pure product"

Example 7

O-xylene is oxidized to phthalic anhydride using the catalysts prepared according to Example 1. The reaction temperatures are 400-600 ⁰ G, preferably ⁰ 425 525 Oe, the contact times are 0.01-20 sec _e, the prints 0.5-30 atm _e, preferably 1-5 atm _e the Molkonientration the o-xylene in air or in a mixture of oxygen and inert gas such as nitrogen, steam or GO2 »is 0.1-1.5 -MoI- ^, The phthalic anhydride is obtained by direct condensation from air on cooled surfaces or by washing in water with subsequent evaporation and dehydration ,

Example 8

The catalyst described in Example 2 was used for the oxidation of o-xylene to phthalic anhydride. The reaction was carried out in a steel reactor with an internal diameter of 19 mm, which was enclosed by a brass block and contained an axial thermocouple pocket. The product was obtained by direct condensation from the Residual gas as well as obtained by washing with water. The analysis of the product was carried out by gas chromatography and

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carried out by Pjj titration. The following yields were obtained;

Amount of gas used, yield of phthalic anhydride,

Y / V - catalyst / hour "$

400 ° C 450 ⁰ C 500 ⁰ O 3,000 66 98 91 12,000 14th 74 94 Example 9

Supported catalysts were made in the manner described in Example 8 ″ with Nb / Y atomic ratios up to 1 and tested. The highest yields are given below.

Fb / V ₁ - atomic ratio phthalic anhydride, wt .- ^ 0.1 94

0.25 98

0.50 75

1.0 66

Example 10

50 ml of an ITiobvanadate catalyst prepared according to Example 2 and having an Nb / V atomic ratio of 0.25 were mixed with 70 ml of silicon carbide granules. The mixture was filled into a reactor with an internal diameter of 23 mm, which was provided with a thermocouple. The reactor tube was provided with a jacket. The reaction temperature was maintained with a heat transfer medium. At a space velocity of the air flow of 9,500 V / v / hr _OJ a Durolkonzentration of 0.28 mol # and an average catalyst bed temperature of 418 ⁰ O A yield of 91 wt .- ^ achieved

Example 11

600 ml of a SiO supported catalyst with an Nb / V ratio of 0.25 was charged into a reactor

909816/0701

The reactor was provided with a jacket and had an internal diameter of 25.4 mm and a length of 1.5 m. The reaction temperature was maintained by passing a eutectic salt mixture through the jacket. Durol at a concentration of 0.24-0.35 times-f ° in air was oxidized to PMDA. The product was obtained by cooling from the residual gas in the reactor and then collecting the solid PMDA particles on a filter cloth. At an average temperature of the catalyst bed of 393 Ο and an air flow rate of 4000 V / V / h, 55 wt _e -. $ PMDA obtained For · a durchschnittlichen.Temperatur of the catalyst bed of 410 ⁰ G (measuring point 433 ° E) and a space velocity of the air of 6000 Y / v / St'd _e was obtained in a yield of 72 wt .- ^ . At an average catalyst bed temperature of 416 ⁰ O (measuring point 451 ⁰ C), and a space air flow rate of 20,000 v / v / h ", the yield was 69 percent, ~ $.

Example 12

A catalyst which contains niobium vanadate at an Nb / V ratio of 0.25 and silicon carbide granules as a carrier is prepared as follows: 30 g of Oc are carefully dissolved in 74.6 g of oxalic acid in water at about 50 ° 0 Vanadinoxalatlösung is slowly added a solution of 27.8 g ITioboxalat in water "supplied while adding 300 g Silioiumcarbidgranulat the mixture is evaporated to dryness while it is rolled. the supported catalyst is calcined for 1 hour at 500 ⁰ g"

50 ml of the catalyst are placed in a reactor tube with an internal diameter of γοη 19 mm, which is provided with an axial thermocouple. 70 ml of uncoated silicon carbide granulate are placed over the catalyst as a preheating zone. Ootahyjdro ^ · is passed anthracen.bei a concentration of 0.1 mol $ in air at 450 ⁵ C over the catalyst. The contact time is 0.5 sec

9 0 9 8 18/0701

direct condensation of Feetstoffe is pyromehitic dianhydride in a yield of 60 G-ew _o - $ obtained

Example 13

Under the conditions mentioned in Example 12, ootahydrophenanthrene becomes the anhydride of 1,2,3j4-benzene tetra-carboxylic acid oxidized. The yield is 54% total.

' Example 14

Under the conditions mentioned in Example 12, 1 lyBis (3 »4-dimethylphenyl) ethane becomes 3> 3% 4} 4» -Benzophenontetraoarbonsäuredianhydrid oxidized · The yield is 62% by weight.

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Claims (8)

H68824 claims 1. Process for the catalytic oxidation of alkyl aromatic hydrocarbons by reaction at elevated temperatures with an oxygen-containing gas in contact with an oxidation catalyst, characterized in that a vanadium oxidation catalyst containing niobium is used as the oxidation catalyst. 2. The method according to claim 1, characterized in that the Catalyst niobium in an amount of 0.5 to 1 g-atom niobium contains vanadium per g atom. 3. The method according to claim 2, characterized in that the catalyst is mounted on an inert support. 4 »Method according to claim 1, characterized in that the Catalyst contains niobium in an amount of about 0.1 to 0.3 g-atom niobium per g-atom vanadium '. 5. The method according to claim 1, characterized in that the Oxygen containing gas is air. 6. Process for the catalytic oxidation of alkylbenzenes containing at least two adjacent lower alkyl substituents contained on the benzene ring to come into contact with an oxygen-containing gas by reaction at elevated temperatures to form an acid anhydride with an oxidation catalyst, characterized in that a Vanadium catalyst, the niobium in amounts of about 0.05 to Contains 1 g atom of niobium per g atom of vanadium. 7. The method according to claim 6, characterized in that as Catalyst a niobium vanadate is used. 909816/0701 • 8. The method according to claim 7 * characterized in that the Niobium vanadate catalyst is mounted on an inert support. 9. The method according to claim 8, characterized in that the Niobium vanadate catalyst 0.1 to 0.3 g-atom niobium per g-atom Contains vanadium. 10. The method according to claim 6, characterized in that the Alkylbenzene is a tetraalkylbenzene. 11. The method according to claim 10, characterized in that the alkyl radicals are methyl radicals. 12. The method according to claim 6, characterized in that the oxygen-containing gas is air. IJ. Process for the catalytic oxidation of durol to pyrornellitic dianhydride by reacting Durol at elevated temperatures with an oxygen-containing gas in contact with an oxidation catalyst, characterized in that the oxidation catalyst is a vanadium oxidation catalyst, containing niobium is used. 14. The method according to claim IJ, characterized in that the Catalyst contains from 0.5 to 1 g atom of niobium per g atom of vanadium. 15. Process for the catalytic oxidation of durol to pyromellitic dianhydride, characterized in that a gas stream containing oxygen and durol with a niobium vanadate catalyst, which contains 0.5 to 1 g-atom of niobium per g-atom of vanadium, at temperatures between about ^ 00 ° to 00 ° C in Is brought into contact and the pyromellitic dianhydride formed is separated off. 909816/0701 Ιό. Process according to Claim 15, characterized in that the niobium vanadate catalyst contains about 0.1 to Q, J> g-atom of niobium per g-atom of vanadium. 17 «Method according to claim 16, characterized in that the Niobium vanadate catalyst contains a carrier, 18. The method according to claim 17, characterized in that the Carrier is silicon carbide. 19. The method according to claim I5, characterized in that the Pyromellitic dianhydride by cooling the reaction gas stream is separated at temperatures below the solidification point of the pyromellitic anhydride and the so formed solid particles of the dianhydride separated from the gas stream on a solid gas-permeable surface will. 20. The method according to claim I5 * characterized in that the Pyromellitic dianhydride is separated off by washing the reaction gas with water. 21. The method according to claim I5, characterized in that the niobium vanadate catalyst is applied to a support which consists of silicon carbide and / or aluminum oxide and contains about 0.1 to 0.5 g atom of niobium per g atom of vanadium, and that the The gas flow is air containing about 0.01 to 1.5 mol- # Durol, and contact with the catalyst at pressures between 0.5 and 150 atmospheres and at temperatures below 500 ° C. for a period of time
2 seconds. doors below 5OO C for a time between 0.01 and 22. Process for the catalytic oxidation of octahydroanthracene to pyromellitic dianhydride by reacting the octahydroanthracene at elevated temperatures with an oxygen-containing gas in contact with an oxidation catalyst, characterized in that a Vaxiadiumoxidationskatalysator containing niobium is used as the oxidation catalyst will. 90 98 16/070 1