DE2641907A1 - PROCESS FOR AMMONOXIDATION - Google Patents

Description

PATENT LAWYERS
SHIP ν. FÜNER STREHL SCHÜBEL-HOPF EBBINGHAUS

MUNICH 9O, MARIAHILFPLATZ 2 & 3 POSTAL ADDRESS: D-8 MÜNCHEN 95, POSTFACH 95 O1 6O

DIPL. CHEM. OR. OTMAR DITTMANN (+1 876) KARL LUDWIQ SCHIFF

DIPL. CHEM. DR. ALEXANDER V. FÜNER

DIPL. INQ. PETER STREHL

DIPL. CHEM. DR. URSULA SCHÜBEL-HOPF DIPL. INQ. DIETER EBBINGHAUS

TELEPHONE (Ο8Θ)

TELEX 6-23S6S AURO D TELEGRAMS AUROMARCPAT MUNICH

September 17, 1976 DA-12 247

SUN VENTURES, INC.

Process for ammoxidation

Addendum to patent

(Patent application P 26 11 560.6)

The invention relates to a process for the preparation of nitriles and in particular dinitriles by ammoxidation a hydrocarbon substituted with lower alkyl groups, in which the hydrocarbon, oxygen and ammonia are passed over an ammoxidation catalyst, by introducing the oxygen used as a reactant at several points on the catalyst bed

according to the main patent (patent application

P 26 11 560.6).

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The vapor phase ammoxidation of organic compounds to nitriles is well known and examples of this process is described in U.S. Patents 2,463,457 and 2,496,661. This method is particularly suitable for the production of nitriles of alkyl-substituted aromatic hydrocarbons, for example to convert toluene into benzonitrile, from xylenes to tolunitriles and phthalonitriles and the like, and it is also generally useful for Conversion of alkyl-substituted aliphatic, aromatic, alicyclic and heterocyclic compounds into the corresponding nitriles.

A catalyst is used to carry out the known process used in a fixed bed system or a fluidized bed or fluidized bed system can, and preferred catalysts are oxides, salts or acids of vanadium, molybdenum, tungsten or their Mixtures known (US Pat. No. 2,496,661). In the prior art it is stated that to start the method the catalyst should be conditioned to initially to achieve maximum catalyst activity, and that this should be done by having the catalyst treated with ammonia, hydrogen, or both substances for a duration which is usual several minutes to several hours. After that, the process is started by taking from the organic Reactant, ammonia, and oxygen (or an oxygen-containing gas) stream the reactant under reaction conditions

30 is passed over the catalyst.

One of the difficulties inherent in an ammoxidation system is the oxygen in the reactant stream contains, as explained above,

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is the undesirable combustion of the organic hydrocarbon reactant and from ammonia to undesirable by-products which are formed in place of the nitriles desired as products. This difficulty of course adds to the process cost because of the formation of a given amount of the nitrile greater amount of reagents is required (i.e., because yields are reduced) and because for preparation larger capital investment is required for industrial-scale equipment. This difficulty The combustion of ammonia and hydrocarbons is particularly acute when using a fixed bed system or a Fluidized bed system is applied under pressure.

It has now been found that the combustion of ammonia and hydrocarbons in fixed bed or fluidized bed ammoxidation systems can be significantly reduced if measures are taken to reduce the exothermic areas that occur within the Reactor beds occur. These exothermic areas are called "hot spots" that are inside and on the Bed occur due to local conditions that cause a very rapid and very high temperature rise to lead.

The invention is therefore based on the object of reducing the problem of these "hot spots" and providing a To cause a far higher ratio of formation of dinitriles to mononitriles, which is particularly desirable is when dinitriles are produced as intermediates for the production of aromatic dicarboxylic acids (for example terephthalic acid from terephthalonitrile) should be used.

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* "26A1907

This task is already partially covered by the main patent (patent application P 26 11 560.6)

through a process for the production of nitriles Ammoxidation of a hydrocarbon substituted with lower alkyl groups, in which the hydrocarbon, Oxygen and ammonia passed in a fixed bed system over an ammoxidation catalyst be solved.

The invention now relates to an ammoxidation process for the production of nitriles, in which the gaseous Reactants consisting of a lower alkyl substituted hydrocarbon, oxygen and Ammonia are made to be passed over an Ammonoxidatxonskatalysator, by introducing the as a reactant used oxygen on several

Place the catalyst bed, according to the main patent

(Patent application P 26 11 560.6), which is characterized in that the catalyst is in the form of a Fluidized bed system or fluidized bed system uses.

According to a general embodiment, an ammoxidation reactor is described according to the invention in which a lower-alkyl-substituted hydrocarbon, ammonia and oxygen (or an oxygen-containing one Gas) under ammonoxidation conditions with an ammoxidation catalyst arranged in a fixed bed or in a fluidized bed be brought into contact. According to the invention devices are provided that it allow the oxygen to be distributed throughout the catalyst bed, such as feeders to the Feeding the oxygen to the fixed bed or fluidized bed reactor at several points within the Catalyst bed. Various procedures for explaining this technique are discussed below

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and it can be seen that whenever in this patent application and the claims of the as Reaction participants used oxygen is mentioned, of course this term also the use an oxygen-containing gas such as air.

The invention is explained in more detail by means of the accompanying drawings.

In these drawings represents

Fig. 1 is a simplified sectional view of a conventional fixed bed ammoxidation reactor.

Fig. 2 is a sectional view of a fixed bed reactor according to the invention, in which oxygen porous walls is introduced.

3 and 4 are sectional views of fixed bed reactors according to the invention, in the oxygen to several Places along the length of the reactor is discharged.

Fig. 5 shows a simplified sectional view of a fluidized bed reactor cylindrical structure in which the Oxygen is introduced at several points along the length of the reactor.

Fig. 6 shows a preferred embodiment of a fluidized bed reactor which is conical in shape.

It can be seen from the drawings that FIG. 1 shows a conventional fixed-bed catalytic reactor is, the container 11 of which is filled with the catalytic converter 12 is. The reactants for ammoxidation (e.g. hydrocarbons, ammonia and oxygen) are introduced into the reactor via feed line 13 and the products of the reaction are derived from the

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264190 '/

Exit opening 14 removed.

In Fig. 2 is an embodiment of the invention Method shown, according to which a double-walled container with a central hollow section is used in which the catalyst 17 around the circumference of the container is arranged between the inner wall 15a and the outer wall 15b. A feeder 18 for the Reactant passes the gaseous reactants over the catalyst 17, while the reacted Gases flow through the outlet opening 19. The wall of the device surrounding the hollow section according to Fig. 2 is porous or permeable. The oxygen or oxygen-containing stream (the air) becomes introduced into the system at opening 20, while the other reactants (e.g. ammonia and Hydrocarbon) introduced through the feed 18 will. The oxygen penetrates through the inner wall 15a and is over the entire length of the Catalyst bed in which the reaction occurs,

20 shares.

In Fig. 3, another embodiment of the invention is shown. In this embodiment, a gaseous Reactants, preferably oxygen, introduced into different levels of the reactor bed.

As shown in the figure, a container 11 is with the Catalyst 12 is filled and the reactants, hydrocarbon and gaseous ammonia, pass over the feeder 21. The oxygen used as a reactant is supplied through various feeds 22a, 22b and 22c are introduced into the reactor bed, which carry the oxygen to various points within the Bring catalyst bed. The oxygen or the air stream may or may be cooled if desired

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can be at room temperature or the reaction temperature may be initiated, depending on the design conditions and the amount of cooling required inside the bed is desirable. Usually the oxygen containing stream is at room temperature held to reaction temperature. The product gases exit through the opening 23.

4 shows an alternative to the one according to the invention Method shown, according to which the oxygen used as a reactant by several lateral feeds (24a to 24g) located at a distance from one another are introduced into the reactor. Like there is shown, the catalyst 12 is filled in a container and the gases to be supplied (for example Hydrocarbon and ammonia) are introduced through the feed 25, while the product gases through the exit 26. It is understood that the inlets (24a to 24g) with valves, not shown may be provided, which is also preferred, so that an exact temperature control within the reactor is made possible.

By using a porous wall or several oxygen streams to be introduced in accordance with those described Embodiments, the temperature of the catalyst bed are moderate and exothermic spots within the bed that lead to excessive combustion of hydrocarbons and ammonia.

FIG. 5 shows the embodiment according to the invention in which a fluidized bed system is used. As Reactant-employed gases, xylene and ammonia, are introduced at the bottom of the reactor as shown and serve to whirl up the catalyst.

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"* ήή 2 6 A Ί 9 U '/

Oxygen or air is introduced into the fluidized bed at various points along the bed, while the products and the unreacted gases above those placed at the top of the reactor Cyclone separator are performed, in which a separation of the catalyst fine particles is effected.

In Figure 6 is a preferred fluidized bed device shown, which is conical in shape, and in which, as described above, the oxygen or the air separate feed openings along the layer is introduced into the system. The conical The shape of the fluidized bed enables the maintenance of a practically constant gas velocity and thus a more favorable level of fluidization in the reactor.

It is also desirable and preferred, when using a fluidized bed system, one with baffles or use conductive plates equipped layer, as described in US Pat. No. 2,893,849, there this results in a more favorable gas residence time distribution achieved and more favorable yields are formed.

The preferred procedure, through which the otherwise usually occurring exothermic points within the catalyst layer are reduced in that all of it is required in the catalyst bed Oxygen is introduced at several points along the bed. In addition, the inventive The method is particularly valuable when it is under a pressure of from about 2 to about 10 atmospheres, preferably about 2 to about 5 atmospheres

30 turns.

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f / ' 264190' /

The inventive method is among the usual Conditions of ammoxidation and carried out with any organic reactants in are usually converted into nitriles by ammoxidation. The for the inventive method suitable organic reactants can therefore be selected from numerous compounds, including alkyl substituted aromatic, aliphatic and alicyclic compounds. To preferred Starting materials include the mono- and polyalkyl-substituted aromatic hydrocarbons of the Benzene and naphthalene series, such as toluene, the xylenes, Ot-methylnaphthalene, polymethylnaphthalenes (for example 2,6-dimethylnaphthalene), monoalkyl and polyalkyl anthracenes, Mesitylene, durene, pseudocumene, methyl tetralin and the like. The preferred alkyl substituent is a methyl group, the substituent can of course also have more than a single carbon atom and therefore the corresponding ethyl and other lower alkyl substituents are also suitable substituted compounds.

Aliphatic compounds which are commonly subjected to ammoxidation include olefinic ones Links. Any olefinic hydrocarbon with at least an alkyl group. Examples of such compounds include propylene, butenes, octenes, methylheptenes, Alkylbutadienes, pentadienes, ethylbutenes, hexadienes, heptadienes and the like, all of which belong to the lead corresponding nitriles. Preferred olefins are compounds containing up to about 10 carbon atoms contain, in particular propylene, butenes and methylbutadienes and cycloolefinic compounds, in particular alkyl-substituted olefin hydrocarbons,

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e.g., 2-methylcyclohexene, 1 ^ -Dxmethylcyclohexene and like that.

Alicyclic compounds with an alkyl substituent, for example, are also suitable as reaction participants Methylcyclopentane, methylcyclohexane and alkyl substituted decalins and the like.

The catalyst used in the process of the invention can be any of the conventional ammoxidation catalysts. For example, the catalyst contains one or more of the elements copper, silver, tin, uranium, thorium, vanadium, chromium, molybdenum, tungsten or one or more of the metals of group VIII of the Mendelejev ¹ see periodic table or one or more compounds, preferably oxides, any of these elements. Catalysts which are used in the process according to the invention can be used with or without a support; however, they are preferably applied to a support containing aluminum oxide or silicon dioxide.

Suitable alumina and silica supports include, for example, alumina gel, activated Alumina, ^ -alumina, silica gel, carborundum, diatomaceous earth, pumice stone, acid clay and Asbestos. The catalysts can be applied to the support by any conventional method, for example by the coprecipitation method or by the immersion method, the Nitrates, chlorides, oxides, hydroxides, salts of organic acids or, if elements are used, the part of an anion, the acid of these metals or the corresponding alkali or ammonium salts of the acid can be used. The one to be placed on the carrier

709850/063 3 OBWNAL ΙΝβΡΒΟΙΗ)

^ "26A1907

Bringing catalyst can contain a single metal or multiple metals, or it can be a mixture of metal compounds, for example of oxides.

According to a preferred embodiment of the invention, a special material known as "vanadium bronze" is preferably applied to an oi. -Aluminium oxide carrier, used as a catalyst. It is known in the art that the addition of an alkali metal compound to vanadium pentoxide when the mixture is heated produces complex materials with abnormal valences known as vanadium bronzes. These materials are described in the literature, for example in the article by P. Hagenmüller "Tungsten Bronzes, Vanadium Bronzes and Related Compounds", in "Comprehensive Inorganic Chemistry", pages 541 to 605, Verlag JCBailar Jr. et al, 1973 Pergamon Press.

The amount of catalyst (e.g., the catalyst load) coated on the carrier is in the range from about 1 to 15% by weight, preferably from about 3 to 8% by weight. The specific surface area of the The preferred catalyst used in the process is generally quite low and is less than

2 2

10 m / g and usually 1 to 5 m / g. The pore volume of the catalyst is chosen so that the predominant Proportion of the pores has a diameter of less than about 1 μm and in the order of magnitude of about 0.2 to 1.0 μm lies.

As already indicated, the process according to the invention is carried out in a fixed bed or fluidized bed system at a temperature between about 350 and about 525.degree. C., preferably between 350 and 500.degree. As a sour

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material source is preferably used air: it is suitable or any other source of oxygen. The amount of oxygen used in the process can vary within a wide range and can contain from about 0.5 to about 10 moles of oxygen per mole of the hydrocarbon be. According to a preferred embodiment, a ratio of oxygen to p-xylene is used of no more than about 3: 1, preferably from 2.5: 1 to 3: 1, with a ratio of about 2: 1 also being used is very suitable. In a corresponding way, the molar ratio of ammonia to hydrocarbon, that is adhered to in the method vary within wide limits and can be about 1 to about 10; according to a preferred embodiment it is about 3: 1 or less, preferably about 2: 1 to 3: 1. In the preferred embodiment is the percentage volume concentration of the reactants corresponding to the preferred ratios given above are also quite high compared to most Ammoxidation process and the feed preferably contains 6 to 7 volume percent p-xylene, 13 to 18 volume percent Oxygen and 10 to 22% by volume ammonia.

It should be emphasized that the residence time of the hydrocarbon reactant on the catalyst can vary within a wide range, usually amounts to it takes about 0.1 to 20 seconds. The residence time or contact time that is observed depends on the catalyst loading or catalyst concentration, the catalyst volume, the temperature and others to the person skilled in the art known parameters, so that no difficulties in choosing a suitable contact time in Dependence on these reaction parameters exist.

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As already explained, the inventive method is of utmost importance when the process is carried out under pressure, because in the operation of a Fixed bed ammoxidation system under pressure reduces the yield of the nitrile product due to the excessive combustion of hydrocarbons and ammonia occurs. The inventive method is therefore preferably used when a pressure of about 1.5 to about 4 atmospheres is applied, since this embodiment enables an effective operation of the method with the lowest possible capital expenditure and equipment Effort made possible.

The method of the present invention becomes the most advantageous using aromatic hydrocarbons substituted with lower alkyl groups Benzene and naphthalene series, e.g. toluene, m-xylene, p-xylene, 2,6-dimethylnaphthalene, 1,4-dimethylnaphthalene and the same.

Both meta- and para-xylene are particularly well suited reactants for the process. if m-xylene is used to obtain isophthalonitrile, however it is preferred to have temperatures on the lower end to comply with the range given above, which is consistent with experience known in the art, that m-xylene is more sensitive to carbon oxide formation than the p-isomer.

It is also understandable that unreacted Hydrocarbons and mononitriles formed as by-products can be returned to the reactor, to increase the effectiveness of the procedure. The recycling of mononitriles is of particular value to the Increase in the conversion of the hydrocarbon to the dinitrile.

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The invention is illustrated by the following examples, in which preferred catalysts and Process conditions are indicated.

Examples 1 to 3

Using the device shown in FIG. 3 and, for carrying out a comparative experiment, one usual fixed bed reactor, as shown in Fig. 1, the ammoxidation of p-xylene with the help of a vanadium oxide catalyst coated on alumina carried out with air as the source of oxygen. In the following The table shows the reaction conditions, namely the molar ratio of the reactants to hydrocarbon (HC), the temperature and the contact time or residence time and the results obtained.

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Table 1

Example ttol ratio
NH ₃ / HC MD ratio
O ₂ / HC Tononoxidation of p-xylene
T ( ⁰ C) residence time
(lake)
CO CO ₀ 5.0 0.6 6, 9 Product distribution,%
BN TN TPN TN + TPN 38.7 53.3 92.0 TPN
TNHTPN -J 1 6.0 a 450 5.0 1.4 9, 8th 0.5 49.9 38.0 87.9 0.579 O 2 3.0 a 450 5.0 3.8 15, 2 0.9 47.9 31.8 79.7 0.432 OO
cn 3 3.0 b 450 5.0 7.6 7, 2 1.3 55.8 26.4 82.2 0.399 O
O Comparative 6.0
attempt 2.7 450 3.0 0.321 Remarks:

a. Oxygen to hydrocarbon = 3: 1 (total ratio; the feed was made half through the oxygen supply line 22a, half through the oxygen Feed lines 22b and 22c (Fig. 3)

b. Oxygen to hydrocarbon = 3: 1 (total ratio); the loading took place 2/3 through the oxygen supply line 22a and 1/3 through the oxygen supply lines 22b and 22c (Fig. 3).

BN = benzonitrile TN = tolunitrile

TPN = terephthalic acid dinitrile

CO

As can be seen from the above data, when the oxygen is combined with the reactants hydrocarbon and ammonia and introduced into the usual reactor together with these, the amount of dinitrile (TPN) formed is significantly less than in the embodiment of the invention according to which the oxygen is introduced into the catalyst layer at various points. It should also be noted that a comparison of Example 1 with the comparative experiment, in which the ratio of NH ₃ to HC, the temperature and the residence time are comparable, shows that in the process according to the invention, the total nitrate (TN + TPN) in one Amount of 92.0% is formed, while the comparison

15 attempt only 82.2% can be achieved.

Examples 4 and 5

A reactor with an outside diameter of 2.54 cm (1 inch) with side inlets for the introduction of air corresponding to the apparatus shown in FIG. 4 is used for the ammoxidation of p-xylene. This reactor contains a 48.3 cm (19 inch) long section filled with sodium vanadium bronze catalyst (8% catalyst loading), before and after sections of quartz chips are placed. The catalyst has the empirical formula Na V ₀ O- (where χ = 0.7 to 1.0) and is applied to oC aluminum oxide. The upper quartz zone, which acts as a preheating zone, is located above the sand level in a fluidized sand bath, so that the temperature can be controlled separately by an electrical winding. The reactor tube has seven equally spaced (6.03 cm = 2 3/8 inches) air inlets along the length of the reactor. The air through each of these air inlets is passed through a separate rotary

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flow meter so that even air flows flow through all feeders. The reactor is equipped with a 0.32 cm thermometer hole and a display thermocouple provided that runs through the entire length of the reactor.

In this reactor, two tests were carried out under a pressure of about 2.11 atmospheres with multiple air introduction (30 psig). The reaction conditions and results are shown in Table 2 below and are compared there with the results of a comparative test with normal air supply (i.e. where all of the air is introduced through a reactor inlet).

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Tabel

Example no. Comparison
example 52 Example 4 Example 5 ι Air supply normal Note: HC = hydrocarbon, PX =
TPN = terephthalic acid dinitrile multiple multiple Sand bath temperature, ⁰ C 400 400 370 Molar ratio O ₂ / HC 2.5 2.5 2.5 _{NH 3} / HC molar ratio 2.5 2.5 2.5 Pressure, atü (psig) 2.11
(30) 2.11
(30) 2.11
(30) PX contact time, see 8th 10.4 10.4 PX conversion,%
(in one go) 14th 68 57 Selectivity,%
(in one go) TN 16 55 55 TPN 1 34 34 O TN + TPN 17th 89 89 § TPN / TN + TPN 0.058 0.382 0.382 Γ ™ Plant TPN yield,% 3 84 82 ω NH2 combustion,%
the NHo charging 16 18th i p-xylene, TN = tolunitrile

It is clear from the above data that the multiple introduction method of the present invention of air the xylene conversion and the dinitrile yield be increased extremely and that the combustion of ammonia is also noticeably reduced, so that the overall process can be carried out more effectively.

Examples 6 to 8

Using the device shown in Fig. 2 with a 0.63 cm thick catalyst bed, the central The area was filled with crushed quartz, the ammoxidation of p-xylene at a pressure of 2.11 atmospheres (30 psig). The catalyst used in Examples 6 and 8 corresponds to that according to Examples 4 and 5. As a catalyst in Example 7, a carrier-free mixture of V-Or, TiO? and B ^ Oo in a weight ratio of 1: 1: 0.125 used. In Table 3 below, the reaction conditions and results are shown. The Tabel-Ie 3 also includes a comparison test in which the oxygen (in the form of air) together with the Hydrocarbon and ammonia in nozzles. Reactor initiated will.

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Table 3

CD 00

O 09

Internal oxidation of p-xylene Iton-
tact-
Time
(lake) MdI-
behaved-
nis
NH ₃ / HC MdI-% Qn-
behaves- wall-
nis funny
O ₂ / HC 37.6 %
CO TN TEN Product distribution TPN % 7th 4.0 1.7 17.4 17.2 38.5 41.4 TN
+
TPN TN + TPN % NH- 7th 4.0 1.7 39.3 37.6 28.1 19.1 79.8 0.518 combustion (Supply of O2 through the porous inner tube) 6th 4.0 2.0 18.3 9.3 46.1 39.2 47.2 0.405 18.1 Example terar
pera-
door 4th 4.0 2.0 64.1 ' 17.1 57.3 15.6 85.3 0.459 35.0 6 400 8th 3.9 2.9 50.6 8.8 46.3 44.5 72.9 0.215 22.0 Compare 400 6th 3.0 3.0 17.2 43.4 37.9 90.8 0.490 50.4 7 425 81.3 0.467 28.4 Compare 425 52.4 8 450 Compare 450

Ko

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Claims (8)

Claims 1. Process for the preparation of nitriles by Ammoxidation of a hydrocarbon substituted with lower alkyl groups, in which • the hydrocarbon, oxygen and ammonia passed over an ammoxidation catalyst by introducing the oxygen used as a reactant to several Place the catalyst bed according to the main patent (patent application P 26 11 560.6), characterized in that the catalyst is in the form of a fluidized bed system begins. 2. The method according to claim 1, characterized It is noted that the ammoxidation is carried out under a pressure of about 2 to about 10 atmospheres. 3. The method according to claim 1 or 2, d a characterized in that the lower alkyl substituted hydrocarbon is an aromatic hydrocarbon the benzene or naphthalene series are used. 4. The method according to any one of claims 1 to 3, characterized in that that a xylene, preferably p-xylene, is used as the hydrocarbon. OftiSiNAL INSPECTED 7 0 9 8 B Π / 0 ß 3 Ί 5. A process for the preparation of an aromatic dinitrile from the benzene or naphthalene series, characterized in that a hydrocarbon of the benzene or naphthalene series substituted with lower alkyl groups is mixed with ammonia and oxygen at a temperature of about 35 to about 525 ⁰ C is subjected to ammoxidation in the presence of a supported vanadium catalyst in a fluidized bed, with a molar ratio of ammonia to hydrocarbon of about 2: 1 to about 3: 1 and a molar ratio of oxygen to hydrocarbon of about 2: 1 to about 3: 1 adhered to and at least a part of the oxygen is introduced through several "feeds, which are arranged along the length of the catalyst bed at a distance from one another. 6. A process for the preparation of terephthalic acid dinitrile, characterized in that that p-xylene with ammonia and oxygen at a temperature between about 390 and about 500 ° C and at a pressure of about 2 to about 10 atmospheres in the presence of one in a fluidized bed arranged vanadium bronze catalyst in a molar ratio of ammonia to p-xylene from about 2: 1 to about 3: 1 and an oxygen to hydrocarbon molar ratio of about 2: 1 converts to about 3: 1, the oxygen being distributed in the layer in such a way that it is by several oxygen spaced apart along the length of the catalyst bed Initiates feedings. 709850/0633 7. The method according to claim 6, characterized characterized in that the catalyst used is sodium vanadium bronze on o (aluminum oxide is used as a carrier and the reaction is carried out at a pressure of about 2 to about 5 atmospheres. 8. The method according to claim 7, characterized in that that the reaction is carried out in a fluidized bed in a conical reactor equipped with guide plates 10 is present. Sn / 063 ';