JPH0749419B2 - Method for producing heteroaromatic nitriles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a heteroaromatic nitrile by subjecting an alkyl-substituted heteroaromatic compound to a gas phase catalytic reaction with ammonia and molecular oxygen.

Heteroaromatic nitriles are useful as raw materials for medicine and agricultural chemicals.

Problems to be Solved by the Prior Art and the Present Invention As catalysts for synthesizing heteroaromatic nitriles by ammoxidation using an alkyl-substituted aromatic compound as a raw material, many catalysts mainly containing vanadium oxide have been proposed. However, in the case of ammoxidation of an alkyl-substituted heteroaromatic compound, these catalysts have too strong activity to cause a dealkylation reaction or an abnormal reaction such as cleavage of the heteroaromatic ring, resulting in the desired product heteroaromatic nitriles. However, the selectivity and the yield were low.

As an ammoxidation catalyst for an alkyl-substituted heteroaromatic compound, Japanese Patent Publication No. 57-19706 discloses at least one element selected from the group consisting of oxides of antimony and vanadium and iron, copper, titanium, cobalt, manganese and nickel. Catalysts containing the oxides of Although it has a relatively high selectivity, it has a drawback that its activity is likely to decrease due to the reduction of ammonia, and is not necessarily a catalyst that is industrially satisfactory.

As a result of intensive investigations by the present inventors, in producing heteroaromatic nitriles by ammoxidizing an alkyl-substituted heteroaromatic compound, the molar ratio of molecular oxygen and ammonia is specified, and vanadium- By using phosphorus oxides, it is possible to produce heteroaromatic nitriles with high yield and high selectivity, with which abnormal reactions are unlikely to occur, and in addition, this catalyst has heat resistance and reduction resistance, and is safe in operation. Was found to be high, and completed the present invention.

Means for Solving the Problems The present invention provides a method for producing heteroaromatic nitriles by subjecting an alkyl-substituted heteroaromatic compound to a gas-phase catalytic reaction with ammonia and molecular oxygen to obtain a molar ratio of molecular oxygen and ammonia. And 1.6 or less, and in the formula (I) VP _a O _b (I) (wherein a and b represent the atomic ratio of phosphorus and oxygen to vanadium, respectively, a is 0.5 to 3 and b is another element). It is a value obtained from the valence.) A method for producing heteroaromatic nitriles characterized by using a catalyst containing vanadium and phosphorus oxide represented by the formula:

The catalyst in the present invention may be any catalyst containing the oxide of the formula (I). As the oxide of vanadium and phosphorus, either an amorphous or crystalline complex oxide can be used as the catalyst of the present invention.

If the vanadium and phosphorus oxides are amorphous,
The atomic ratio of vanadium to phosphorus is not particularly limited, but the preferred ratio is 1: 0.5 to 3. As the crystalline complex oxide of vanadium and phosphorus, the atomic ratio of vanadium and phosphorus is known to be 1, 2, 3, etc., but in the present invention, the atomic ratio of 1 and / or its crystalline complex oxide. A complex oxide of vanadium and phosphorus, which is produced by reducing hydrogen, is effective. The crystalline complex oxide referred to here is generally represented by the formula (I
It has the structure shown in I).

Formula (II) (VO) _n P _n O _4n-1 · XH ₂ O (II) (wherein n is from ∽ to 2, X is an integer of 0 or 1 or more) In formula (II), the valence of vanadium is 4 ~ 5.

Typical examples of the compound represented by the formula (II) include α-vanadyl phosphate (α-VOPO ₄ ), α-vanadyl phosphate dihydrate (α-VOPO ₄ · 2H ₂ O), β- Vanadyl phosphate (β
-VOPO ₄ ), divanadyl pyrophosphate, ((VO) ₂ P ₂ O ₇ ) and divanadyl pyrophosphate dihydrate ((VO) ₂ H ₄ P ₂ O ₉ or (VO) ₂ P ₂ O ₇ -2H ₂ O) and its X-ray diffraction pattern is shown in Table 1. Further, the vanadium-phosphorus composite oxide produced by reducing these generally has weak crystallinity.
This may be due to lattice defects or shear (shear) structure generation.

For the preparation of the catalyst containing vanadium and phosphorus oxides in the present invention, generally known methods for preparing vanadium and phosphorus oxides can be applied. For example, when the oxides of vanadium and phosphorus are amorphous, it can be prepared by a method of reacting ethanolamine aqueous solution in which ammonium metavanadate is dissolved with phosphoric acid to evaporate to dryness, and then firing in the presence of air. Further, for example, when the oxide of vanadium and phosphorus is crystalline, a method of reacting vanadium pentoxide and phosphoric acid, evaporating to dryness and then firing in the presence of air, reacting ammonium metavanadate with phosphoric acid,
Prepare by evaporating to dryness and then baking in the presence of air, or by reacting vanadium pentoxide, oxalic acid and ammonium dihydrogen phosphate to dryness, and then baking in a nitrogen stream. You can

Further, a composite oxide produced by reducing the crystalline composite oxide thus obtained with a reducing gas such as hydrogen, ammonia, or hydrocarbon can also be used as the catalyst of the method of the present invention. For example, as the reduction treatment with ammonia, a method of treating the crystalline complex oxide with ammonia or a gas obtained by diluting ammonia at a temperature of 300 to 600 ° C. is preferable.

The compounds of various elements used when preparing the catalyst are not limited to special ones, and any of the compounds usually used can be used. As the vanadium compound, ammonium metavanadate, vanadium pentoxide, vanadium phosphate and the like can be used, and as the phosphorus compound, phosphoric acid, metaphosphoric acid, phosphorous acid, phosphate (for example, ammonium phosphates) and the like can be used.

A carrier may be used for the catalyst in the present invention, and silica, alumina, silica-alumina, silicon carbide, titanium oxide, diatomaceous earth and zeolite are particularly preferable.

Examples of the alkyl-substituted heteroaromatic compound in the present invention include 2-methylpyridine, 3-methylpyridine,
4-methylpyridine, 2,3-dimethylpyridine, 2,4-dimethylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine, 3,4-dimethylpyridine, 3,5-dimethylpyridine, 2-methyl -5-ethylpyridine, 2,4,6-trimethylpyridine, 2,3,4-trimethylpyridine, 2,3,5
-Trimethylpyridine, 2,3,6-trimethylpyridine,
Such as alkyl-substituted pyridines, methylpyrazine, ethylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2-methyl-5-ethylpyrazine, 2-methyl-6-ethyl Examples thereof include alkyl-substituted pyrazines such as pyrazine.

The concentration of the alkyl-substituted heteroaromatic compound in the reaction feed gas is usually 0.15 to 7 mol%.

The molar ratio of molecular oxygen and ammonia in the reaction feed gas is
It should be 1.6 or less, preferably 1.3 or less. If the molar ratio is higher than this value, reactions such as complete combustion of the alkyl-substituted heteroaromatic compound and ammonia occur, and the yield of the desired nitriles is significantly reduced.

Air is usually used as the molecular oxygen in the present invention, but pure oxygen or a mixture thereof with air can also be used. In the present invention, the alkyl-substituted heteroaromatic compound, the molecular oxygen and the raw material supply gas of ammonia,
The reaction can be performed by diluting with an inert gas such as steam or nitrogen. The reaction temperature in the present invention is 300 to 6
The temperature is 50 ° C, preferably 350 to 600 ° C. The space velocity (hereinafter referred to as SV) is 200 to 50,000 Hr ^-1 , preferably 300 to 20,000 Hr ^-1 . The reaction is usually carried out at normal pressure, but it can also be carried out under reduced pressure or increased pressure. A solid bed type reactor is usually used, but a fluidized bed type reactor can also be used.

EFFECTS OF THE INVENTION By carrying out the present invention, an abnormal reaction is unlikely to occur, heteroaromatic nitriles can be produced with high yield and high selectivity, and furthermore, the present catalyst has heat resistance and reduction resistance, The safety of is improved.

Next, the present invention will be described with reference to examples. The reaction rate and yield were calculated according to the following definitions.

Example-1 146.5 g of ammonium metavanadate was dissolved in 1250 g of distilled water at 60 ° C. with stirring, 144 g of 85% phosphoric acid was added, and the mixture was reacted for 2 hours to obtain a reaction solution in which a yellow precipitate was deposited. The reaction solution was concentrated, dried at 110 ° C. for 8 hours, and then calcined at 500 ° C. for 4 hours in the presence of air. The obtained catalyst was β-vanadyl phosphate (β-VOPO ₄ ), and the X-ray diffraction pattern was in agreement with Table-1. 10 cc of this catalyst was packed in a Pyrex reaction tube with an inner diameter of 12.6 mmφ, and the catalyst filling part of the reaction tube
While maintaining the temperature at 0 ° C, a gas in which the molar ratio of 4-methylpyridine, ammonia, air and steam was mixed at 1: 15: 75: 10 was passed through SV3,000Hr ^-1 , and the reaction gas was absorbed in water for 20 minutes. When collected and analyzed by gas chromatography, the reaction rate was 99.4% and the 4-cyanopyridine yield was 81.5%.

Example-2 Example-2 except that the reactor temperature was set to 400 ° C. and a gas obtained by mixing 4-methylpyridine, ammonia, air and steam at a molar ratio of 1: 10: 10: 15 was flowed at SV2,000Hr ^−1. When reacted in the same manner as in 1, the reaction rate was 99.5% and the yield of 4-cyanopyridine was 94.0%.

Comparative Example-1 Reaction was conducted in the same manner as in Example-1 except that the molar ratio of 4-methylpyridine, ammonia, air and water vapor was mixed at 1: 2: 75: 10 and the reaction rate was 99.3%, 4 -Cyanopyridine yield was 4.2%.

Comparative Example-2 A reaction was performed in the same manner as in Example-1 except that a gas obtained by mixing 4-methylpyridine, ammonia, air and water vapor at a molar ratio of 1: 8: 75: 10 was flowed at SV2,000Hr- ^1. Reaction rate 99.4
% 4-Cyanopyridine yield was 9.6%.

Example-3 When 63 g of 85% phosphoric acid was heated to 95 to 100 ° C., 50 g of vanadium pentoxide was added to obtain a reaction liquid in which a yellow precipitate was deposited. The reaction solution was concentrated, dried at 110 ° C. for 8 hours, and then calcined in the presence of air at 500 ° C. for 6 hours and further at 700 ° C. for 4 hours. The resulting catalyst was α-vanadis phosphate (α-VOPO ₄ ), and X
The line diffraction pattern was in agreement with Table-1. This catalyst was mixed with carbonized diatom in a volume ratio of 1, and 100 cc was filled in a Pyrex reaction tube having an inner diameter of 12.6 mm. Hold the catalyst-filled part at 450 ° C,
Gas mixed with a molar ratio of 2-methylpyridine, ammonia, air and water vapor at 1: 10: 10: 10 was passed through SV3,000Hr ^-1 , and the reaction solution 10 hours after the start of the reaction was analyzed by gas chromatography. The reaction rate was 93.8%, and the yield of 2-cyanopyridine was 76.3%.

Example-4 To 600 cc of distilled water, 252.8 g of 85% phosphoric acid was added with stirring, and after heating to 95 ° C, 200 g of vanadium pentoxide was added,
After reacting for 30 minutes and further adding 132 g of silica, the mixture was mixed for 1 hour and concentrated. The obtained precipitate was dried at 110 ° C. for 8 hours, and calcined in the presence of air at 500 ° C. for 6 hours and further at 700 ° C. for 4 hours. In this way vanadyl phosphate / silica (VOPO
A catalyst which is ₄ / SiO ₂ ) was obtained. This vanadyl phosphate is β
-VOPO ₄ , and the X-ray diffraction pattern was as shown in Table 1. This catalyst was placed in a reaction tube similar to that in Example-1.
cc filling, keeping the catalyst filling part at 430 ℃, ammonia 100
After reducing by flowing cc / min for 20 hours, gas SV1,000Hr ^-1 mixed with the molar ratio of methylpyrazine, ammonia, air and water vapor at 1: 20: 11: 1 was used for reaction, and the reaction solution was subjected to gas chromatography. The reaction rate was 94.8% and the cyanopyrazine yield was 81.5%. The reaction rate after 1,000 hours was 91.5%, and the cyanopyrazine yield was 81.2%.

Example-5 In 750 cc of distilled water, 315 g of oxalic acid was dissolved with stirring, and after heating to 80 ° C., 90.5 g of vanadium pentoxide and 115 g of ammonium dihydrogen phosphate were added and concentrated to dryness.
The obtained solid was baked at 550 ° C. for 5 hours under a nitrogen stream.
The resulting catalyst is divanadyl pyrophosphate ((VO) ₂ P ₂ O ₇ ).
And the X-ray diffraction pattern was in agreement with Table-1. Using this catalyst, the reaction was carried out by the method shown in Example 2 except that the raw materials were 3-methylpyridine and SV1000Hr ^-1 . As a result, the reaction rate was 90.3% and the 3-cyanopyridine yield was 81.1%.

Example 6 146.5 g of ammonium metavanadate was dissolved in 1500 g of a 10 wt% aqueous solution of stirred monoethanolamine, and then 85%
144.0 g of phosphoric acid was added and reacted for 30 minutes, the solution was concentrated to dryness, and the obtained solid was calcined at 550 ° C. for 5 hours in the presence of air to obtain vanadium and phosphorus oxide (VPO ₅ ). It was The oxide of vanadium and phosphorus was amorphous as a result of X-ray diffraction. As a result of carrying out the reaction by the same method as in Example-2 except that the temperature of the reactor was 510 ° C. using this catalyst,
The reaction rate of 4-methylpyridine was 96.5%, and the yield of 4-cyanopyridine was 85.1%. The reaction rate of 4-methylpyridine and the yield of 4-cyanopyridine 500 hours after the start of the reaction were 95.4% and 84.7%, respectively.

Examples-7 to 9 A catalyst having the composition shown in Table-2 was prepared in the same manner as in Example-6, and the reaction was carried out in the same manner as in Example-2. The results are shown in Table-2.

Examples-10 to 13 By using β-VOPO ₄ / 3SIO ₂ prepared in the same manner as in Example 4 as a catalyst, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, and methylpyrazine were prepared. When the reaction was performed under the conditions shown in Table 3, the results shown in Table 3 were obtained.

Example-14 Using the catalyst prepared in Example-4, using a mixture of 3-methylpyridine 65 mol% and 4-methylpyridine 35 mol% as a raw material, the SV and the reactor temperature were 1,200 Hr ^-1 and 430, respectively. The reaction was carried out under the conditions shown in Table 4 except that the temperature was changed to
The results shown in 4 were obtained.

Example-15 A reactor temperature was set to 420 ° C., and a gas obtained by mixing 3,5-dimethylpyridine, ammonia and air at a molar ratio of 1:40:40 was mixed with SV.
When reacted in the same manner as in Example 4 except that 1,500 Hr ⁻¹ was used, the reaction rate was 100%, the yield of 5-cyano-3-methylpyridine was 32.5%, and the yield of 3,5-dicyanopyridine was 44.0%. .

Claims (7)

[Claims] 1. When a heteroaromatic nitrile is produced by subjecting an alkyl-substituted heteroaromatic compound to a gas phase catalytic reaction with ammonium and molecular oxygen, the molar ratio of molecular oxygen and ammonia is set to 1.6 or less, and (I) VP _a O _b (I) (In the formula, a and b represent atomic ratios of phosphorus and oxygen to vanadium, respectively. A is 0.5 to 3, and b is a value obtained from the valences of other elements. A method for producing heteroaromatic nitriles, which comprises using a catalyst containing vanadium and phosphorus oxide represented by. 2. A vanadium-phosphorus composite oxide having a vanadium-phosphorus atomic ratio of 1 and / or a vanadium-phosphorus composite oxide produced by reducing the crystalline composite oxide. The manufacturing method according to claim 1. 3. A crystalline complex oxide of vanadium and phosphorus has the formula (II) (VO) _n P _n O _4n- 1.XH ₂ O (II) (wherein n is from ∽ to 2 and X is 0 or 1). It is the above integer.) The production method according to claim 2, which is an oxide shown. 4. A crystalline complex oxide of vanadium and phosphorus,
alpha-vanadyl (α-VOPO _4), α- vanadyl dihydrate _{(α-VOPO 4 · 2H 2} O), β- vanadyl (β-VOPO _4), divanadyl pyrophosphate ((VO ) ₂ P
₂ O ₇ ), or divanadyl pyrophosphate, dihydrate ((V
O) ₂ H ₄ P ₂ O ₄ or (VO) ₂ P ₂ O ₇ · 2H ₂ O). 5. The method according to claim 1 or 2, wherein the catalyst is a catalyst supported on silica, alumina, silica-alumina, silicon carbide, titanium oxide, diatomaceous earth or zeolite. 6. The vanadium-phosphorus composite oxide produced by reducing the crystalline composite oxide is 300
The production method according to claim 2, which is an oxide produced by reduction treatment with ammonia or a gas containing ammonia at a temperature of up to 600 ° C. 7. The method according to claim 1 or 2, wherein the alkyl-substituted heteroaromatic compound is alkyl-substituted pyridines or alkyl-substituted pyrazines.