DE2123836A1 - - Google Patents

Description

(Pate-ntaruüoldung P 18 öy 795.S ~ 'i2)

u.z. G 160 C (j / Bz / k) P03-23338

JAPAN GAS-CHEHICAL COMPANY, INC.,
Tokyo, Japan

"Process for the manufacture of flavored nitriles and catalyst "

Priority: May 14, 1970, Japan, No. 40 510/70

There are already various processes for producing aromatic ones Nitriles known by ammoxidation of alkyl aromatics in the gas phase over a catalyst. Most of the catalysts are based on the vanadium oxide system. Catalysts that contain only vanadium oxide as a catalyst component,

triles are too active and the yields of aromatic YIi- 'obtained are relatively low. To overcome these disadvantages, catalysts containing various metal oxides have been developed. With some of these catalysts, aromatic nitriles are obtained in considerably high yields. The disadvantage here is that the properties of these catalysts are very dependent on the production conditions. These catalysts therefore have a low degree of reproducibility,

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and the yield of aromatic nitrile decreases with little Changes in the reaction conditions, e.g. the reaction temperature and the residence time, decrease significantly. Also occur in the implementation Side reactions, e.g. colored products, Hydrocyanic acid, carbon dioxide and carbon monoxide are produced. Because of the colored products, the reaction product is also colored. This makes the subsequent purification of the reaction product more difficult and expensive. Furthermore, these catalysts have the Disadvantage that hot spots occur in the catalyst bed, as a result of which ammonia is often decomposed to a considerable extent.

In the German patent application P 18 09 795.5 is a method for the production of aromatic Mitrile using catalysts described, the a yanadium oxide, a chromium oxide and contain a boron oxide »With the aid of these catalysts, the disadvantages described above can be overcome. Furthermore, considerably increased yields of aromatic nitrile are obtained by this process. The atomic ratio of

V: Cr: B of these catalysts is from 1: 0.5: 0.01 to W 1: 2: 0.5. The vanadium oxide content of these catalysts is 2 to 10 percent by weight, calculated as VoO ₅ . These values correspond to a total oxide content of the oxides applied to a carrier, calculated as VgOj-f Gr _p 0 ₇ and B2 ° 3 " ^{from 2} > ⁸ ^ to 28.6 percent by weight"

It has now been found that when silicon dioxide is used as an embossing agent, the boron content ranges in an atomic ratio of

V: Cr: B and the total oxide content of the oxides applied to the carrier can be selected to be greater than in the case of the

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named catalysts. The present invention "is based on this plague.

The invention thus relates to a process for dividing aromatic nitriles by reacting a gas mixture containing an alkyl aromatic, ammonia and oxygen or a gas containing free oxygen on a catalyst containing vanadium oxide, chromium oxide and boron oxide, applied to a support, at temperatures from 300 to 500 ⁰ C, which is characterized in that the reaction is carried out on a catalyst, the silicon dioxide as support and vanadium oxide, chromium oxide and boron oxide in an atomic ratio of V: Cr: B of 1: 0.5: 0.1 up to 1: 2: 1.2 and its total oxide content of the oxides applied to the support, calculated as V ₂ O ₅ , Cr ₂ O., and B ₂ O ^, is 20 to 80 percent by weight.

In the method according to the invention is compared to that in the German Patent application P 18 09 795.5 described method

considerably facilitates the temperature control of the catalyst bed, the The occurrence of side reactions is reduced and the temperature range of the reaction is extended. Furthermore, the Invention obtained a several percent higher yield of aromatic nitrile than in the aforementioned process.

The process of the invention is preferably carried out with a catalyst carried out, its atomic ratio V: Cr: B from 1: 0.7: 0.3 to 1: 1.5: 1.0 and its total oxide content of oxides applied to the support 30 to 60 percent by weight

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"amounts to.

Although the valence levels of the metals of the oxides applied to the carrier in the finished catalyst are not known, in the present application the total oxide content of the oxides applied to the carrier is given in percent by weight on the basis of V ₂ Oc, Cr ₂ O ₇ and B ₂ O ₇ calculated.

Vanadium, chromium and boron oxides can be used to produce the catalysts according to the invention. Furthermore can Vanadium, chromium and boron compounds are vei-wenueu that can easily be converted into the corresponding oxides during the preparation of the catalysts, e.g. by heating. Such connections are e.g. ammonium metavanadate, vanadyl sulfate, Vanadyl oxalate, vanadyl tartrate, chromic acid, chromium nitrate, ammonium chromate, Chromium oxalate, chromium tartrate, boric acid and ammonium borate.

For the preparation of the catalysts according to the invention, the Silica serving as a carrier in the form of a silica sol can be used.

The catalysts of the invention can be prepared by known methods. For example, an aqueous solution of Add boric acid to vanadium oxide and chromium oxide and then

,,, πα. ι · Silica sol. ,. send the mixture obtained exn / add, whereby a suspension is obtained. For the production of a fluidized bed catalyst the suspension obtained is spray-dried. This product is in a calciner for a few hours at 200 to

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250 ⁰ C and then calcined at higher temperatures. To produce a fixed bed catalyst, the suspension obtained is evaporated to dryness. This product is subjected to a few hours a temperature of about 10O ⁰ C and subsequently calcined. The calcination is a few hours' at 450 Ms 65O ⁰ O, preferably "at 500 to 600 ⁰ C, carried out in air.

In the process of the invention, for example, toluene, Ethylbenzene, xylene, diethyl "benzene, mesitylene, diisopropylbenzene, Cymol and methylnaphthalene are used.

If air is used as the gas containing free oxygen, the reaction is preferably carried out with a gas mixture, which contains 0.5 Ms 4 percent by volume of an alkyl aromatic.

'The theoretically required amount of ammonia is 1 molecule of ammonia per alkyl radical of the alkyl aromatic compound used. Preferably If the reaction is carried out with more than the theoretically required amount of ammonia, as this results in a somewhat increased yield of aromatic nitrile is obtained. In particular, the implementation carried out with about two to ten times the theoretically required amount of ammonia. This area is proving to be cheap regarding the recovery of the unreacted ammonia.

The reaction is preferably carried out with an oxygen content of the gas mixture which is at least 1.5 times that theoretically required amount of oxygen. In particular, will

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the reaction with about off the three to five times the theoretically "required Säuerst quantitative carried out. Preferably, in the method of the invention as a free-oxygen containing gas, air is used. The free-oxygen containing gas, an inert diluent, for example nitrogen ₉ carbon dioxide or Wasserdampfj be admixed.

The reaction is carried out in the process of the invention at temperatures of 300 "to 50O ⁰ C. The reaction is preferably carried out at temperatures of 330 Ms 450 ° C.

At temperatures below 330 G, the rate of conversion of the alkyl aromatic into the corresponding aromatic ITitrile is slow. In Heaktionstemperaturen about 500 ⁰ C as a result of ITebenreaktionen the formation of carbon dioxide, hydrogen cyanide and other by-products increases, decreases the yield of aromatic nitrile. The optimum reaction temperature depends on the type and concentration of the alkyl aromatic and on the residence time. The optimum reaction temperature must therefore correspond to the gas mixture used and the other reaction conditions

k can be carefully selected from the above range.

The residence time of the gas mixture on the catalyst can be within vary over a wide range. The dwell time is preferably in the range from about 0.5 to about 30 seconds.

During the ammoxidation of alkyl aromatics in the gas phase, considerable amounts of heat are released. For this reason, the dissipation of the heat of reaction is of particular importance. Bureh the catalyst used in the process according to the invention is this pro

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blem has been significantly reduced. It will, by itself, "if you use it." a fixed bed catalyst, a more even temperature distribution reached in the catalyst tray. In terms of discharge the heat of reaction, however, a fluidized bed or a fluidized bed catalyst offers particular advantages Catalysts are used in the fluidized bed process in particular an excellent abrasion resistance and excellent flow properties.

The process according to the invention is generally carried out at atmospheric pressure carried out, but can also be carried out at reduced or increased pressure.

The reaction product can be separated off by customary methods, for example with the aid of a cooling device, such as an air cooler or one containing water or another coolant Cooler, or by washing out with water or inorganic acids.

The examples illustrate the invention.

example 1

618 g of oxalic acid, (COOH) ₂ ^ HgO, are added to 500 ml of water at a temperature of 80 to 90 C and dissolved by heating on a water bath. 247 g of vanadium pentoxide are slowly added to this solution while stirring, an aqueous solution of vanadyl oxalate being obtained.

1018 g of oxalic acid are added to 900 ml of water. This mixture

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272 g of chromium trioxide are slowly added with stirring and heating on a water bath, an aqueous solution of Chromium oxalate is obtained.

83.9 g of boric acid are added to 5 1 of water and dissolved by heating the mixture to 60 to 7O ⁰ C.

The solutions prepared above are combined. The combined solution is added to 1670 g of an aqueous, weakly alkaline silica sol with a silicon dioxide content of 30 percent. The suspension is stirred and then sap-dried. The temperature at the outlet of the drying device is about 180 ^° C. The spray-dried product is calcined in a calcining furnace at 250 ^° C. for about 12 hours and then at 550 ° C. for 12 hours. The size of the catalyst particles obtained in this way is 30 to 250 / rev. The atomic ratio of V: Cr: B "is 1 i 1: 0.5, and the total oxide content of the oxides applied to the support is 50 percent by weight.

40 ml of this catalyst are placed in a stainless steel reactor (inner diameter: 21 mm). After the reactor has been heated in a molten salt, a gas mixture consisting of 1.17 percent m-xylene, 13.9 percent ammonia and 84.9 percent air is passed ^{through the catalyst bed at a temperature of 400 °} C. and a space velocity of 716 / hour. 82.8 mol percent isophthalonitrile and 3.4 mol percent m-tolunitrile, based on the m-xylene fed in, are obtained.

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example

A gas mixture consisting of 1.20 percent toluene, 6.0 percent ammonia and 92.8 percent air is passed ^{through the catalyst bed described in Example 1 at a temperature of 595 °} C. and a space velocity of 689 / hour. 2 mol percent benzonitrile, based on the toluene fed in.

Example 3

298 g of oxalic acid, (COOH) ₂ * 2H ₂ O, are dissolved in 300 ml of water at a temperature of 80 to 90 '
Vanadium pentoxide dissolved.

Temperature of 80 to 9O ⁰ C dissolved. In this solution, 119 g

(. NH) 165 g of ammonium bichromate, 0Cr ₂ O _7, v; ground dissolved in 4OO ml water having a temperature of 50 to 60 ⁰ C.

56.7 g of boric acid are dissolved in 5 liters of water with heating.

The solutions prepared above are combined. The combined solution becomes 835 g of an aqueous, 30 percent silica containing sols. The suspension obtained is stirred and treated according to the method described in Example 1. The atomic ratio V: Cr: B of the catalyst thus obtained is 1: 1: 0.7, and the total oxide content of the oxides applied to the support is 50 percent by weight.

40 ml of the catalyst are introduced into the reactor described in Example 1. One made from 1.21 percent m-xylene, 14.8 percent Ammonia and 83.97 percent air are used as a gas mixture

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a temperature of 385 ⁰ C and a space velocity of 683 / hour passed through the catalyst. 82.3 mol percent isophthalonitrile and 0.9 mol percent m-tolunitrile, based on the m-xylene fed in, are obtained.

Example4

A p-xylene from 1.19 percent, 14 _f 3 percent ammonia and 84.5 percent air gas mixture consisting / v ird conducted at a temperature of 400 ⁰ C and a space velocity of 690 / hour by the procedure described in Example 1 catalyst bed. 82.4 mol percent of terephthalonitrile and 1.5 mol percent of p-tolunitrile, based on the p-xylene fed in, are obtained.

Example 5

61.8 g of oxalic acid, (COOH) ₂ * 2HpO are dissolved in 50 ml water with a temperature of 80 to 9O ⁰ C. 24.7 g of vanadium pentoxide are slowly added to this solution while stirring. The vanadium pentoxide is dissolved.

101.8 g of oxalic acid are added to 90 ml of water and dissolved by heating to 80 to 90.degree. This solution is then slowly mixed with 27.2 g of anhydrous chromic acid, an aqueous solution of chromium oxalate being obtained.

5.25 g of boric acid are dissolved in 50 ml water with a temperature of 80 to 90 ⁰ C.

The solutions prepared above are combined. The unite

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The third solution is added to 350 g of an aqueous sol containing 30 percent silica. The suspension obtained is stirred. The suspension is then evaporated to dryness on a water bath. The dried product is finely pulverized and sieved through a sieve with a mesh size of 1.19 to 2.38 mm. The sieved powder is calcined in a CAI cihierofen 15 hours at 55O ⁰ C. The atomic ratio of V: Cr: B of the catalyst obtained in this way is 1: 1: 0.3, and the total oxide content of the oxides applied to the support is 30.8 weight s "or ο7. Ent.

13 ml of the catalyst prepared above are in a heat-resistant Glass reactor (inner diameter: 10 mm) filled. The glass reactor is heated in a molten salt. One off 0.60 percent m-xylene, 5.96 percent ammonia and 93.44 percent air The gas mixture passes through the catalyst bed at a temperature of 403 ° C. and a space velocity of 1210 / hour directed. There are 81.2 mol percent isophthaionitrile and 2.5 mol percent m-Iolunitril, based on the fed m-xylene, obtain.

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Claims (10)

Patent claims: 2173836 / Ί. .Process for the production of aromatic nitriles by reaction of a gas mixture which contains an alkyl aromatic, ammonia and oxygen or a gas containing free oxygen on a catalyst which is applied to a support and contains a vanadium oxide, a chromium oxide and a boron oxide "at temperatures from 300 to 500 ⁰ C, characterized in that the reaction is carried out on a catalyst containing silicon dioxide as the carrier and vanadium oxide, chromium oxide and boron oxide in an atomic ratio of V: Cr: B of 1: 0.5: 0.1 to 1 : 2: 1.2 and its total oxide content of the oxides applied to the support, calculated as VpOf-, Cr ₂ O _7. And BpO ,, is 20 to 80 percent by weight. 2. The method according to claim 1, characterized in that the reaction is carried out over a catalyst whose atomic ratio V: Cr: B from 1: 0.7: 0.3 to 1: 1.5: 1.0 and its total oxide content that applied to the support Oxide is 30 to 60 percent by weight. 3. The method according to claim 1 and 2, characterized in that the reaction with toluene, ethylbenzene, xylene, Diethylbenzene, mesitylene, diisopropylbenzene, cymene or Performs methylnaphthalene as alkyl aromatics. 109849/1992 21? 3836 . Method according to claim 1 to 3, characterized in that that the reaction is carried out with a gas mixture that is 0.5 "to Contains 4 percent by volume of an alkyl aromatic, if Air is used as the gas containing free oxygen. 5. The method according to claim 1 "to 4, characterized in that that the reaction is carried out with more than the "theoretically required" amount of ammonia. 6. The method according to claim 1 "to 5, characterized in that that the implementation with at least 1.5 times the theoretically required. Sauer st off quantity carries out. 7. The method according to claim 1 "to 6, characterized in that the reaction is carried out" at temperatures of 330 "to 45O ⁰ O" 8. The method according to claim 1 "to 7, characterized in that that the reaction is carried out with residence times of the gas mixture on the catalyst of 0.5 "to 30 seconds. 9. The method according to claim 1 to 8, characterized in that the reaction is carried out with air as the free oxygen Gas carries out. 10. Catalyst for carrying out the process according to claim 1 to 9 »containing silicon dioxide as a carrier and vanadium oxide, Chromium oxide and boron oxide in an atomic ratio of V: Cr: B from 1: 0.5: 0.1 to 1: 2: 1.2 and a total oxide content 10 9 8 4 9/1992 of the oxides applied to the support, calculated as V ₂ O ₅ , Cr ₂ O ₃ and B ₂ O, _f from 20 to 80 percent by weight. 109849/1992