HUT76437A - Process for oxidative ammonolysis of alkylpyridines - Google Patents

Description

The present invention relates to a process for the preparation of a highly selective catalyst for the production of cyanopyridines by oxidative ammonolysis of alkylpyridines and to a process for the preparation of cyanopyridines.

The present invention is particularly directed to the preparation of 3-cyanopyridine and cyanopyridine derivatives which are important precursors of nicotinic acid and nicotinic acid amide. Nicotinic acid and nicotinic acid amide are essential vitamins of the vitamin B complex.

Oxidative ammonolysis of alkylpyridines is well known in the art. A wide variety of catalyst systems and processes have been described, but there is no known process that satisfies the requirements of a commercially viable process on an industrial scale.

Reference is made to British Patent No. 1,317,064, which discloses a mixed oxide catalyst containing vanadium oxide and titanium dioxide in a molar ratio of 1: 0.6 to 1:32 for the oxidative ammonolysis of alkylpyridines. Conversion of 3-methylpyridine yields a maximum of 89% yield of cyanopyridine (Example 42; V ₂ O ₅ : TiO ₂ = 1: 16), while conversion of 2-methyl-5-ethylpyridine yields a maximum of 61%. (Example 54; V ₂ O ₅ : TiO ₂ = 1: 4).

In particular, the results obtained by this known process are unsatisfactory in terms of selectivity, yield and feed rate of alkylpyridines.

Accordingly, it is an object of the present invention to provide a highly selective ammonoxidation catalyst and to provide an improved process for the conversion of alkylpyrrhphins by oxidative ammonolysis.

The disadvantages can be overcome by the highly active catalyst of claim 1 and the oxidative ammonolysis process of claim 7.

THE

V is _a catalyst composition defined by the formula Ti _b Zr _c O _x - wherein a is 1; b is 7.5-8; c is from 0 to 0.5; and x represents the number of oxygen atoms required to satisfy the valence requirement of the elements present, according to claim 1, comprising the steps of: co-precipitating (coprecipitate) an aqueous solution of a V ⁵⁺ and Ti ⁴⁺ and optionally Zr ⁴⁺ with aqueous ammonia; thereafter, the resulting precipitate is subjected to drying and heat treatment; and then converting the catalyst composition into a suitable catalyst form.

Suitable sources of the titanium component are preferably water soluble Ti ⁴⁺ compounds such as titanium chloride, titanium bromide, titanium nitrate; and organic titanium compounds such as tetraalkyl titanium compounds.

Suitable sources of the vanadium component include water soluble V ⁵⁺ compounds, such as ammonium metavanadate.

A suitable source of the zirconium component is preferably a water-soluble Zr ⁴⁺ compound such as zirconium oxychloride.

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Co-precipitation is carried out by mixing the dissolved catalyst components simultaneously with the aqueous ammonia solution so that the pH of the liquid after co-precipitation is between 8 and 9.

The precipitate thus formed may be isolated in a known manner and then dried first, preferably in an air stream at a temperature of 120 ° C to 140 ° C; or directly subjected to heat treatment at a temperature between 360 ° C and 400 ° C, preferably in the presence of air. This may be followed by a common forming step to form the appropriate catalyst.

Preferably tablets are formed which are further subjected to a further heat treatment at a temperature of 740 ° C to 850 ° C in the presence of air.

The ready-to-use catalyst composition can then be fed to the reactor where, after the activation phase under the reaction conditions, its excellent activity and selectivity, as well as its long lifetime, can be demonstrated with large batches of alkylpyridine.

Preferred catalyst compositions include:

VTi ₈ O _x ;

VTi ₇ ςΖΓθ ^ Οχΐ es

VTi _{7 5} Zr _{0 125} O _X , where x is as defined above.

The most preferred catalyst composition is:

VTi ₈ O _x , where x is as defined above.

The process of the present invention for the conversion of alkyl pyridines having a very diverse structure to cyanopyridines has the following characteristics:

- 5 can be applied. Examples of suitable alkylpyridines are 3-methylpyridine, 3-ethylpyridine, 2-methyl-5-ethylpyridine, 2,5-dimethylpyridine and 2-methyl-5-vinylpyridine. The most preferred alkylpyridines are 3-methylpyridine and 2-methyl-5-ethylpyridine.

The following circumstances of the procedure proved to be the most appropriate.

The feed gas consists of the corresponding alkyl pyridine, oxygen-containing gas, ammonia and water vapor.

Air is generally used as the oxygen-containing gas. The use of air has the advantage of containing oxygen diluted with inert components.

When converting 3-methylpyridine to 3-cyanopyridine, the feed gas is preferably 3-methylpyridine, air (calculated as O ₂ ), ammonia, and water vapor, preferably from 1: 7: 3: 3 to 1:

: 40: 10: 45 molar ratio.

The ratio is preferably in the range of 1: 10: 4: 10 to 1: 30: 7: 30.

In the conversion of 2-methyl-5-ethylpyridine to 3-cyanopyridine, and depending on the reaction conditions, to 2,5-dicyanopyridine, the feed gas is 2-methyl-5-ethylpyridine, air (O _2). ), ammonia and water vapor are preferably present in a molar ratio of 1: 15: 5: 20 to 1: 70: 40: 140.

The temperature in the reaction zone of the catalyst is generally 330 ° C to 440 ° C, preferably 350 ° C to 410 ° C.

Due to the stable characteristics of the catalyst, such as its service life, the process according to the invention can be applied on a large scale for a long period of time.

• · ·

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The highest molar yields available are about 95-97% for the conversion of 3-methylpyridine and about 75% for the conversion of 2-methyl-5-ethylpyridine.

The resulting cyanopyridines, i.e. 3-cyanopyridine and / or 2,5-dicyanopyridine, can be directly converted to nicotinic acid by conventional basic hydrolysis. Nicotinic acid can be obtained in up to 95% yield with respect to 3-methylpyridines.

EXAMPLES OF MANUFACTURING CATALYSTS

(a) VTi ₈ O _x catalyst

Titanium chloride (690.4 g, 3.64 moles) is slowly added to 400 ml of water at a temperature of about 60-65 ° C, and water is added to make up to a total volume of 800 ml.

In another vessel, 53.19 g (0.45 mol) of ammonium metavanadate were dissolved in 850 ml of water and 300 ml of aqueous ammonia solution at reflux. Meanwhile, ammonia was introduced into the solution.

The solution containing the vanadium compound is added to the titanium solution at about 80-85 ° C and then made up to 4 liters with water.

In a cylindrical reactor, 670 ml of titanium vanadium solution (temperature 80-85 ° C) was stirred with 670 ml of 5.2% aqueous ammonia solution. The coprecipitate thus formed is filtered, washed with water and dried in an air stream at 120-140 ° C.

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The powder thus obtained is then treated in a furnace in the presence of air at 360 ° C for 2 hours, then milled in a ball mill, finally moistened with water and formed into 4 x 4 mm tablets. The tablets were exposed to air at 740 ° C for 2 hours in a bag oven.

The freshly prepared catalyst is activated with 3-methylpyridine under oxidative ammonolysis conditions.

b) VTi _{7 5} Zr _{0 5} O _X catalyst

The vanadium-titanium solution is prepared by the method a) above.

In a separate vessel was dissolved 73.27 g (0.23 mol) of zirconium oxychloride klorid.8H ₂ O in 600 ml water at 40-45 ° C.

The coprecipitation is prepared by the appropriate method described in a) above by mixing 625 ml of titanium vanadium solution, 100 ml of zirconium solution and 725 ml of the corresponding aqueous ammonia solution. Further processing of the resulting precipitate is also carried out according to process a) above.

VTi _{7 5} Zr _{0 12} 5θχ catalyst

Procedure b) is repeated except that 625 ml of titanium vanadium solution, 25 ml of zirconium solution and 650 ml of the corresponding aqueous ammonia solution are co-precipitated.

• · · • ·

- 8 EXAMPLES OF PROCEDURES

Example 1

220 ml of activated VTi ₈ O _x catalyst is charged into a stainless steel tubular reactor (20 mm internal diameter and 1200 mm long).

A gaseous mixture of reagents, i.e. 3-methylpyridine (briefly 3-MP), air, ammonia, and water vapor, was passed through the catalyst bed for 150 hours at 385 ° C with a feed rate of 103.6 g / g. liters / hour 3-MP, 2727 liters / liter / hour air, 113.8 g / liter = hour ammonia, and 336.4 g / liter / hour steam. The molar ratio of feed: 3-MP: air (O ₂ ):: NH ₃ : H ₂ O = 1: 22.9: 6.0: 16.8.

114 g of 3-MP are converted in 5 hours. Then the conversion is complete. 119.5 g of 3-cyanopyridine are obtained, corresponding to a yield of 93.7%. Accordingly, the output is 108 g / l / h of 3-cyanopyridine.

Hydrolysis with potassium hydroxide at reflux for 2 hours gives 143.2 g (95%) of nicotinic acid.

Example 2

The catalyst described in Example 1 was used.

A mixture of 2-methyl-5-ethylpyridine (MEP), air, ammonia and water vapor as reagents was passed through the catalyst bed at 395 ° C. Mole ratio of feed:

MEP: air (O ₂ ): NH ₃ : H ₂ O = 1: 25: 19: 67. In ten hours

155 g of MEP are converted to give 93.2 g of 3-cyanopyridine, m.p.

- 9 corresponds to a yield of 70.5%. Accordingly, the performance was 42.8 g / l / h 3-cyanopyridine.

Hydrolysis with potassium hydroxide gives nicotinic acid in 72% yield.

Example 3

140 ml of the catalyst described in Example 1 were used.

The reagents described in Example 2 were passed through the catalyst bed at 400 ° C.

Mole ratio of feed:

MEP: Air (O ₂ ): NH ₃ : H ₂ O = 1: 16: 14: 30. This gives 53.2 g of MEP in 5 hours and 19.7 g (34.8% yield) of 2.5 of dicyanopyridine and 3-cyanopyridine (23.0 g, 50.3%).

Hydrolysis with potassium hydroxide gives nicotinic acid in 85.4% yield.

Example 4

The tube reactor mentioned in Example 1 is charged with 100 ml of activated _{VTi7 5} Zr ₀₁₅ O _x catalyst. The gas mixture of 3-methylpyridine, air, ammonia and water vapor was passed through the catalyst bed at 375 ° C with a feed rate of 225 g / l / h 3-MP, 344.1 g / l / h air, 111 g / l / h of _NH3 and 980 g / l / h of H ₂ O. thus 112.3 3-MP during 5 hours 92.1 g (73.2%) of 3-cyanopyridine and 21.8 g of nicotinic acid amide (g 14.8%).

By hydrolysis with potassium hydroxide, 138.7 g (93.3 g

%) yields nicotinic acid.

• · «» · · ·

Example 5

The catalyst described in Example 4 was used, but the feed gas contained MEP instead of 3-MP. The temperature of the catalyst layer was 370 ° C. Feed rate: 80 g / l / h MEP, 1225 L air, 180 g NH ₃ and 1130 g H ₂ O.

MEP is converted in 6 hours to give 3.6 g of 2,5-dicyanopyridine (7%) and 28.9 g (70%) of 3-cyanopyridine.

Hydrolysis with potassium hydroxide yields nicotinic acid in 79.9% yield.

Example 6

100 ml of activated VTi _{7 5} Zr _{0 12 S} O _X catalyst were used as described in Example 4. 112.5 g of 3-MP are converted in 5 hours to give 100.8 g (80.1%) of 3-cyanopyridine and 17 g (11.4%) of nicotinic acid amide.

Hydrolysis with potassium hydroxide gives 139 g (93.3%) of nicotinic acid.

Example 7

100 ml of the catalyst described in Example 1 were used, and the feed gas mixture contained 3-ethylpyridine (3-EP). The temperature of the catalyst layer is 380 ° C. Feed rate: 150 g / l / h 3-EP, 3600 l / l / h air, 167 g / l / h NH _3, and 252 g / l / h H ₂ O, thus 75 g 3-EP in 5 hours and 66.5 g (91.2%) of 3-cyanopyridine are obtained.

Example 8

100 ml of the catalyst described in Example 1 were used; the feed-11 • ···································································································• , 5-dimethylpyridine (hereinafter: 2,5-DMP). The catalyst bed temperature is 400 ° C and the feed rate is 102 g / l / h with 2,5-DMP, 2095 l / l / h with air, 227 g / l / h with NH ₃ and 650 g / l / h with H ₂ O.

2.5 g of D-DMP are converted in 5 hours to give 18.8 g of 2,5-dicyanopyridine (i.e. 30.6% yield) and 28.8 g (58.1%) of 3-cyanopyridine .

Hydrolysis with NH _{3 in} an autoclave yields nicotinic acid in 87.9% yield.

Example 9

100 ml of the catalyst described in Example 1 were used; the feed gas mixture is 2-methyl-5-vinylpyridine (hereinafter briefly:

2- MVP). The catalyst temperature is 400 ° C. Feed rate: 113.4 g / l / h 2-MVP, 2095 l / l / h air, 227 g / l / h NH _3, and 750 g / l / h H ₂ O.

g 2-MVP is converted in 5 hours; this gives 23.4 g (37.9%) of 2,5-dicyanopyridine and 24.4 g (48.9%) of 3-cyanopyridine.

Hydrolysis with NH _{3 in} an autoclave yields nicotinic acid (86.3%).

Example 10

710 ml of the catalyst described in Example 1 was charged into a stainless steel tube reactor (21 mm inside diameter, 3 m in length).

On the catalyst bed for 1350 hours at 385 ° C

3-methylpyridine (3-MP), air, ammonia, and water vapor as re- • • • • · ·························································· 9 ·

- A mixture of 12 agents is passed through 100 to 150 g / l / hr 3-MP feed! speed. The molar ratio of the feed gas mixture, ie 3-MP: air (O ₂ ):

: ammonia: water ratio ranges from 1: 5.2: 10: 13 to 1: 5.2: 16: 15. 107 kg of 3-MP is converted to 108 kg of 3-cyanopyridine. The conversion was 97%, the molar yield 91% and the selectivity 93.5%.

Example 11

The VTi ₈ O _x catalyst was prepared according to process a) above, except that the tablets were cured at 850 ° C for 2 hours.

140 ml of activated catalyst were charged into the tubular reactor of Example 1. A gas mixture of 2-methyl-5-ethylpyridine (MEP), air, ammonia and water vapor was passed through the catalyst bed at 375 ° C. The molar ratio of feed to MEP: air (O ₂ ): NH ₃ : H ₂ O = 1: 34: 10: 41. 53.2 g of MEP is converted in 5 hours to 22.8 g (40.2%). 2,5-Dicyanopyridine and 22.5 g (39.7%) of 3-cyanopyridine are obtained.

Hydrolysis with potassium hydroxide gives nicotinic acid in 90.2% yield.

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Claims (14)

Claims 1. Procedure a V is _a catalyst composition defined by the formula Ti _b Zr _c O _x - wherein a is 1; b is 7.5-8; c is from 0 to 0.5; and x represents the number of oxygen atoms required to satisfy the valence requirement of the elements present, characterized by co-precipitation (coprecipitation) from an aqueous solution of a compound V ⁵ * and Ti ⁴⁺ , and optionally Zr ⁴⁺ ; the resulting precipitate is then subjected to drying and heat treatment; and then converting the catalyst composition into a suitable catalyst form. Process according to claim 1, characterized in that the precipitate formed is first dried in an air stream at a temperature of 120 ° C to 140 ° C or subjected to a direct heat treatment at a temperature of 360 ° C to 400 ° C and subsequently and then subjected to heat treatment at temperatures ranging from 740 ° C to 850 ° C. The catalyst composition obtained by the process of claim 1 or claim 2. The catalyst composition according to claim 3 having the general formula VTi ₈ O _x , wherein x is as defined above. - 16th The catalyst composition of claim 3 having the general formula VTi7 ₅ Zr _{0 5} O _x , wherein x is as defined above. 6. A catalyst composition according to claim 3 having the formula VTi _7, filter ₀₁₂₅ O _X, wherein X is as defined above. A process for the preparation of cyanopyridines by oxidative ammonolysis of alkylpyridines, characterized in that a feed gas mixture of alkylpyridine, oxygen-containing gas, ammonia and water vapor is prepared in a coprecipitated catalyst composition according to claim 1 and at 440 ° C. C is passed. 8. The process of claim 7, wherein the catalyst composition of claim 4 is used. The process of claim 7, wherein the catalyst composition of claim 5 is used. 10. The process of claim 7, wherein the catalyst composition of claim 6 is used. 11. The process according to any one of claims 1 to 3, wherein the alkylpyridine is 3-methylpyridine, 3-ethylpyridine, 2-methyl-5-ethylpyridine, 2,5-dimethylpyridine or 2-methyl-5-vinyl- pyridine. 12. The process of claim 11, wherein 3-methylpyridine or 2-methyl-5-ethylpyridine is used. 13. From 7 to 12. A process for the preparation of 3-cyanopyridine by oxidative ammonolysis of 3-methylpyridine according to any one of claims 1 to 3, characterized in that 3-methylpyridine, oxygen-containing gas (calculated as O ₂ ), ammonia and water vapor from 1: 7: 3: 3 to 1: : 40: 10: 45 through the catalyst at a molar ratio. 14. 7 to 12. A process for the preparation of 3-cyanopyridine by oxidative ammonolysis of 2-methyl-5-ethylpyridine according to any one of claims 1 to 3, characterized in that 2-methyl-5-ethylpyridine, the oxygen-containing gas (O ₂ ammonia and water vapor are passed through the catalyst in a 1:15: 5: 20 to 1: 70: 40: 140 molar ratio.