DE1593695A1 - Process for the production of benzonitrile - Google Patents

Description

7EB Leuna-Werke "Walter Ulbricht" Leuna, June 16, 1969 Patent department DG.Bo/Ry

L.P. 690

Process for the production of benzonitrile

The invention relates to a Verfahren- for the production of benzonitrile from toluene by oxidation with oxygen in catalytically © form of air in the presence of ammonia at 300 to 500 ⁰ G in the gas phase using a 3 to 10 wt .-% vanadium pentoxide and oxides of the elements the VI. to VIII. Subgroup of the periodic table containing aluminum oxide that "has been annealed ^{at 650 to 900 0 G before the application of the metal oxides.}

Benzonitrile, an important intermediate for organic synthesis, can be produced by various processes will. Two-way methods for the production of benzonitrile are the reaction of benzoic acid or its esters with ammonia over dehydration catalysts and the catalytic one Oxidation of toluene or other monoalkylbenzenes with air in the presence of ammonia, called ammoxidation for short.

It is known to carry out the ammoxidation of toluene at normal pressure or at slightly increased pressure in the temperature range of 300 to 500 ⁰ G. In addition to the reaction temperature, the quantitative ratio of the substances involved in the reaction and the catalyst used have the greatest influence on the yield of benzonitrile.

As catalysts for the ammoxidation of aromatic hydrocarbons, in particular of xylenes, tin and titanium vanadates and catalysts are known, the vanadium pentoxide or Vanadium pentoxide im, mixture with oxides of the elements of VI. until VII. Subgroup of the periodic table on an aluminum oxide carrier contain. Above all, catalysts are described

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whose aluminum oxide support was heated ^{to 1000 Ms 1500 0} O before the production of the catalyst.

When using these catalysts, the surface of which is expressed is limited to 5 to 20 m / g, the use is larger Amount of air required. So has been described, at least to use three moles of oxygen in the form of air per carbon atom of the alkyl group of one mole of hydrocarbon in the reaction. Usually, however, 50 to 100 moles of oxygen are in the form of air per carbon atom of the alkyl group in one mole of hydrocarbon required; are then in the reaction mixture only 1 to 2% by volume hydrocarbon.

The yields of around 80 % given in the patent literature for the conversion of xylenes to the corresponding dinitriles over the catalysts mentioned were, as tests have shown, not achieved in the conversion of toluene to benzonitrile. It is also known from the literature that the above data could not be confirmed for the conversion of xylenes either. , .. ■

It is also known to use catalysts which contain vanadium "pentoxide or a mixture of vanadium pentoxide and chromium oxide" on an aluminum oxide which had been pre-annealed ^{at 800 0 O before the discharge of the metal oxides;} The mixture of hydrocarbons, oxygen and ammonia entering into the reaction, which is passed through a swirling catalyst, must, however, be diluted with larger amounts of nitrogen.

A common feature of the known processes is that only a slight "... loading of the catalyst is possible, that the yields are sometimes low, that working up the reaction mixture causes great difficulties, since the presence of large amounts of inert gas requires special cooling of the reaction mixture or a washing same with solvents is necessary, '., and that durcli' verlorengehenö the inert gas be derived benzonitrile and unreacted QJolüol

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The purpose of the invention is to overcome the disadvantages mentioned so far "known process for the production of benzonitrile from toluene to avoid. -. ■ ■ *

It "was therefore the task to develop a method that the production of benzonitrile from toluene in high yields if the catalyst is heavily loaded, the work-up may be necessary the reaction products allowed in the technical implementation without major difficulties.

'This object is solved in that the production of benzonitrile from toluene by catalytic oxidation with oxygen in the form of air into Ge.genwart-.of ammonia at 300 to 500 ⁰ G in the gas phase using a 3 to 10-wt % Vaiiadine pentoxide and oxides of the elements of VI. to VIII.-Febengruppe of the periodic table containing aluminum oxide, which was vox "the application of the metal oxides at 650 to 900 ⁰ O annealed, is carried out according to the invention so that the toluene with the simple to a maximum of twice the amount of theoretically required oxygen weight in IPorm of air and an amount of ammonia, preferably used in excess, is passed over the catalyst in the presence of steam.

The ammoxidation of toluene is carried out on catalysts composed of 70 to 97% by weight, preferably 85 to 93% by weight, of the aluminum oxides mentioned and of vanadium pentoxide applied to the aluminum oxide or a mixture of vanadium pentoxide and metal oxides applied to the aluminum oxide the elements of the VI. to VIII. Lifting group of the periodic table, preferably chromium oxide, exist. The vanadium pentoxide and the oxides of the elements of VI. to VIII. Nebengrüppe advantageously be enough, by impregnating the alumina carrier with the decision · speaking Metailoxalatlösüngen, followed by drying and heating for 30 hours to 2, at 380 ⁰ O in the air flow applied. The order in which the metal oxalates are impregnated is irrelevant. The weight ratio of the ¹ oxides can vary within wide ranges; as particularly cheap

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A weight ratio of approximately 1: 1 proves, for a total amount of 5% by weight of vanadium pentoxide. An increasing chromium oxide content means that the same results are obtained over a wide temperature range. An optimally acting catalyst contains an aluminum oxide as a support, which was ^{pre-annealed to 800 0} O for 20 hours and has a surface area of 120 m 2 / g. In general, carriers with a

ρ
inner surface from 50 "to 170 m / g.

The catalyst can be arranged in a stationary manner in reaction tubes which can be directly heated electrically. Appropriately However, the reaction tubes become indirect in salt or metal baths heated. It is also possible to use the catalyst with inert diluents, such as, for example, c <-aluminium oxide, glass or porcelain, to be mixed in a ratio of 1: 0.5 to 1: 5

The ammoxidation of the toluene is preferably carried out between 300 and 500 ⁰ C at 350-420 0, at normal pressure or slightly elevated pressure. A temperature difference is established between the salt or metal bath and the actual reaction zone, which can be influenced by the heat dissipation.The temperature difference depends on the load applied and the amount of air, ammonia and water used in the reaction. ■

The reaction proceeds according to the following equation:

O ₂ + HH ₃ m IJ +3

It turned out, however, that it is advantageous to have ammonia in excess to be used, 3 to 6 moles of ammonia per mole of toluene being passed over the catalyst. With less than three moles Inferior conversions and yields are obtained with ammonia, with more than 6 mol of ammonia there is only a slight increase in the Sales and yields achieved.

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Air is used as the oxygen supplying gas. In the presence of the "described catalysts, only enough air is added to the reaction mixture that per mole of toluene only a single to a maximum of twice the amount of oxygen theoretically required is present in the form of air Contains 25 times the theoretically required amount of oxygen, at 4-10 ⁰ O with 78.3 mol% toluene conversion 71.5 Μο1 .-? Δ benzonitrile per toluene feed or 91 mol% benzonitrile per toluene conversion, if in one hour

.O

the following gas quantities over 100 cnr. a catalyst containing 5 wt .-% vanadium pentoxide and 10 wt .-% chromium oxide on aluminum oxide, which was preheated to 800 ⁰ G before the impregnation of the metal oxides, 2.5 normal liters of toluene vapor, 10 formal liters of ammonia vapor, 10 hormone liters of water vapor and 23.5 normal liters of air.

It is possible to adjust the loading per volume of the catalyst on the Increase 15 times without affecting the conversions and .the yields reduce if it is possible to dissipate the heat of reaction.

The addition of water vapor to the incoming reaction Gases not only make it possible to achieve the described reaction conditions to choose, the steam rather has a favorable influence on the conversion of toluene and the yield of benzonitrile. It is appropriate to carry out the reaction under the aforementioned conditions in the presence of a larger amount of water vapor, for example 4 to 50 moles of water vapor per Mole of toluene.

The amount of water vapor to be used depends on the load. Since the reaction does not always take place over the entire catalyst, the loading is expediently not related to the entire volume of the catalyst, but to the cross-sectional area. of the reactor. In the process according to the invention, it is possible, for example, to use up to 70 B of toluene per cm of reactor cross-section per hour (catalyst: oC-AlgOo = 1: 2) with a sufficient length of the catalyst layer in the reaction. ·. * ■ ·

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The reaction is carried out in a manner known per se. The converted substance mixture is preheated to the reaction temperature and then passed through the reactor. The reaction gases are cooled; Benzonitrile, unreacted toluene ■ and water separate after their condensation. The benzonitrile obtained after a simple distillation is 100% pure pure. The unreacted toluene is used again in the reaction. - '

Example 1:

γ-aluminum oxide was ^{heated to 800 0} O for 20 hours. The γ-aluminum oxide was impregnated with solutions of chromium oxalate and vanadyl oxalate. · The catalyst was dried at 120 ⁰ O and heated for 16 hours in air flow to 380 ⁰ O, wherein the oxalates decompose. The solutions of ohromoxalate and vanadyl oxalate were used in such an amount that 5% by weight of vanadium pentoxide and 5 % by weight of chromium oxide in the catalyst

were included. The catalyst had a surface area of 114 m / g (Catalyst 1).

100 cm * of the catalyst with a particle diameter of 2 to 3 nim were in a vertical reaction tube from 25 mm diameter, which is / in an electrically heated Salt bath located, introduced · Inside the reaction tube was a sleeve 11 mm in diameter with thermocouples for temperature measurement · The substances involved in the reaction were converted into vapor form, passed over the catalyst, condensed and cooled down behind the reactor; the gaseous Products were washed with water.

Within one hour, 2.5 normal liters of toluene vapor, 10 normal liters of water vapor, 10 normal liters of ammonia vapor and 23.5 normal liters of air passed over the described catalyst. The amount of oil in the oil corresponded to a load of 0.13 volume per volume of catalyst, and hour (measured in liquid form) or 3 ~ 5 cm of toluene per cm of cross-sectional area of the reactor.

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The following results were obtained:

Temperature ⁰ o 390 410 435 450 Conversion of toluene in mol% 66.8 74.8 73.3 •
72.7 ■ Yield of benzonitrile per
Toluene input in mol% 58.2 66.8 ■ 60.5 60.0 Yield of benzonitrile per.
Toluene conversion in mol% 87.0 89.4 82.5 . 83.0 * Formation of Gp2 and GO pro
Toluene input in mol% 8.5 ^; 6.9 11.2 8, -7

■ In addition, small amounts of benzene and hydrocyanic acid were formed.

Example 2:

At 100 cur of a catalyst as described in Example 1, was produced / but 5% by weight of vanadium pentoxide and 10% by weight Containing chromium oxide (catalyst 2), the following results were obtained under the conditions described in Example 1:

Temperature ⁰ o 390 410 460 Conversion of toluene in mol% 78.6 78.3 76.0 Yield of benzonitrile per
Toluene input in mol% 69.5 71.5 62.8 Yield of benzonitrile per
Toluene conversion in mol - *% ' 89.5 91.0 83.0 Formation of CO2 and CO pro
Toluene input in mol% 7.2 5.8 7.3

Small amounts of benzene and hydrocyanic acid were also formed.

-Example 3:

IC ™ alumina was on for 20 hours. 800 G heated * The £ -aluminium oxide was soaked with solutions of ghromoxalate and vanadyl oxalate. The catalyst was overall at 120 ^{0 G:} dried and heated 16 hours in the air stream to 380 ⁰ G, wherein the oxalates decompose · solutions Ohroinoxalat and vanadyl oxalate were used in an amount such that

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BATH ORIGINAL

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3% by weight of vanadium pentoxide and 5t5 % by weight of chromium oxide were contained in the catalyst. The results shown in the following table were obtained under the conditions described in Example 1 "."

For comparison, two catalysts of the same composition were prepared, but in which the -χ -aluminum oxide had been heated to 600 ⁰ O or to 1100 ⁰ O instead of 800 ^{0 O for 20 hours.} The results obtained on these catalysts not according to the invention are also given in the following table:

■ "■." - ■ " Inventive
according to kata
lyser
y aluminum
oxide on
Annealed 800 ⁰ G Comparative pj
γ- aluminum
³ oxide
600 ⁰ O
annealed ?above
! ^ Alumi
nium oxide
at 1100ftj
annealed Surface of the cata
goals in m <vg 114 160 Conversion of toluene in
Mol%
Yield of benzonitrile
per toluene input in mol%
Yield of benzonitrile per
Toluene conversion in mol%
Formation of 002 and 00 pro
Toluene input in mol% 66.0
57.1
86.5
8.2 60.7
49.6 '
81 * 6
10.0 55.8
81.4
7.8

Example 4:

Over 100 cm ^ of the catalyst 1 according to Example 1, 2.5 normal liters of toluene vapor, 10 normal liters of water vapor, 10 normal liters of ammonia vapor and varying amounts of air were passed under the conditions described in ^{Example 1 at 410 0 O within one hour.}

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The following results were obtained:

Ifornall liters of air / hour 18th ,1 23.5 28 , 0 33 50 Conversion of toluene in mol% 61 , 6 74.8 80 , 0 85.8 86.0 Yield of benzonitrile
per toluene input in mol% 53 , 5 66.8 68 , 0 ■ 70.2 51.4 Yield of benzonitrile per.
Toluene conversion in mol% 81 , 5 89.4 82 ,8th 80.1 59.8 Formation of CO2 and 00 per
Toluene input in mol% 6th 6.9 10 14.5 21.4

Small amounts of benzene and hydrocyanic acid were also formed.

Example 5:

Over 100 cnr of the catalyst 1 according to Example 1 were passed within one hour at 410 ⁰ O 2.5 normal liters of toluene vapor, 10 normal liters of ammonia vapor, 23.5 normal liters of air and varying amounts of water vapor under the conditions described in Example 1 ».

The following results were obtained:

ITormal liters of water vapor / hour 0 5 , 2 1C ) , 20 »5 30th 40 i5 - Conversion of toluene in mol% 82.4 77 , 4 74, 8th 71 , 3 73.3 74 , 3 ' Yield of benzonitrile per
Toluene input in mol% 52.3 61 ,8th 66 8th 63 , 5 61 ₁ 8 61 "8th Yield of benzonitrile per
Toluene conversion in mol% 63.4 71 , 4 89 3 88 "8th 84.3 81 • 6 Formation of OOp and 00 pro
Toluene input in mol% 19.2 10 6, 6th 6.6 9

In addition, small amounts of benzene and hydrogen cyanide were formed "

Example 6s

3 liters were placed in the reaction tubes of a salt bath reactor JCatalyst 1 according to Example 1 in a mixture with 6 liters / aluminum oxide filled. The apparatus cross-section of the reaction tubes

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"was 38 cm. The catalyst consisted of spheres with a Diameter of 5 in,

• At 420 ⁰ O 17 mol of toluene were in one hour over the

• a ρ

Catalyst passed, which corresponds to 48 em ^J toluene per cm cross-sectional area of the reactor. Per mole of toluene, 4 moles of ammonia, 18 moles of water and 2.3 moles of oxygen were passed over the catalyst in the form of air. With a conversion of 63 mol% toluene, a yield of 55 mol% benzonitrile per toluene used, corresponding to a yield per toluene conversion of 87 mol% was obtained »

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Claims (2)

Patent claims: 1. Process for the preparation of benzonitrile from toluene by catalytic oxidation with oxygen. in iform of air in * ■ the presence of ammonia at 300 to 500 ⁰ C in. the gaseous phase - Using a 3 to 10 wt .-% vanadium pentoxide and jDxide of the elements of VI «to YIII. Subgroup of the periodic system containing.Aluminium oxide, which had been annealed before the application of the metal oxides at 650 to 900 ⁰ O, characterized in that the toluene with a single to a maximum of twice the amount of theoretically required oxygen amount in the form of air and preferably The amount of ammonia used in excess is passed over the catalyst in the presence of steam. 2. The method according to claim I _1, characterized in that the · amount of ammonia is 3 to 6 moles per mole of toluene. 00984t / 1072