Title of Invention	"PROCESS FOR PRODUCING CYANOPYRAZINE"
Abstract	Disclosed is a process for producing 2-cyanopyrazine by ammoxidation of 2-methylpyrazine employing a novel catalyst comprising of an active component consisting of metal oxides of molybdenum, chromium and antimony loaded on alumina.

Full Text

1. Field of the Invention The present invention relates to a process for producing 2-cyanopyrazine by ammoxidation of 2-methylpyrazine employing a novel catalyst comprising of an active component consisting of metal oxides of molybdenum, chromium and antimony loaded on alumina. 2. Background of the Invention 2-cyanopyrazine and their derivatives have acquired tremendous importance since they form the starting materials for a number of valuable pharmaceutical intermediates and anti-tubercular drugs. For catalyzing ammoxidation of an alkyl substituted heteroaromatic compounds such as alkylpyrazines, several catalysts comprising vanadium oxide have been used. However, conventional catalysts possess very strong catalytic activity rendering them unsuitable for the ammoxidation of alkylpyrazines. As a result of the strong catalytic activity of conventional catalysts, dealkylation or cleavage of the heteroaromatic ring occurs thereby resulting in low yields and selectivity of the desired nitriles. It is therefore, essential to develop a catalyst for the ammoxidation of alkyl substituted pyrazine compounds, which provides good yield and selectivity for the desired nitriles. Several processes are reported in the known arts for the catalytic ammoxidation of 2-methylpyrazine and their derivatives to their corresponding nitriles. United States Patent No. 4,931,561 to Shimizu, et al., discloses molybdenum-ceria oxide based catalyst for ammoxidation of alkylated pyrazines to corresponding nitriles, conversion and yields were reported to be approximately 30-40% at a temperature of 400°C, with mole ratios of 2,5-dimethylpyrazine: ammonia: air and steam # 1: 20: 10: 5. The lower conversion, yields and higher mole ratio of ammonia render this process unattractive and unsuitable from the industrial production point of view. United States Patent No. 5,786,478 to Lee, et al., discloses the ammoxidation of 2-methylpyrazine over molybdenum-phosphorus oxide based catalyst for production of cyanopyrazine. In this process quantity of byproducts formed was more such as pyrazinamide and others. It is the main disadvantage of this process. European Patent No.: 0253360 to Shimizu, et al., discloses the vanadium-phosporus oxide catalyst for the production of heteroaromatic nitriles. Production of 2-cyanopyrazine over above catalyst used mole ratios were 1: 25: 15: 2 for 2-methylpyrazine: ammonia: air and steam. Higher mole ratio of ammonia renders this process unattractive and unsuitable. Indian Patent No.: 178283 to Gupta, et al., discloses molybdenum-vanadium oxide catalyst for the production of 2-cyanopyrazine from 2-methylpyrazine over above-mentioned catalyst used mole ratios were 1:15-20:20-25:20 for 2-methylpyrazine: ammonia: air: water at a temperature of 350-400°C and obtained yield and selectivity was 60-70% and conversion was 93-98% respectively. Higher mole ratio of ammonia renders this process unattractive and unsuitable. European Patent No.: 0037123 to Isatsugu, et al., discloses ammoxidation of alkyl heteroaromatic compound over a catalyst comprising of vanadium, antimony and uranium or chromium oxides mixed with fine powdered alumina. The catalyst needs a calcination temparature of 800°C, rendering the process of catalyst preparation unattractive. The reference also recommends a very high mole ratio of air about 90 mole % per mole of alkyl substituted heteroaromatic compound. This is also another disadvantage since it results in very high uncondensable gaseous effluents. Therefore, there is a need to devise an improved process for producing 2-cyanopyrazine by the ammoxidation of 2-methylpyrazine, which ensures higher yield and selectivity at lower mole ratio of ammonia and obviates the formation of byproducts such as, pyrazine, pyrazinamide and pyrazine mono carboxylic acid, at the time of production. The invention disclosed herein demonstrates a better way of ammoxidation of 2-methylpyrazine to produce 2-cyanopyrazine by using a novel catalyst, which results in higher yield and selectivity and also prevent the formation of by product. 3. Summary of the Invention It is the principal aspect of the present invention to devise an improved process for the production of 2-cyanopyrazine comprising reacting 2-methylpyrazine with ammonia and oxygen source over a novel catalyst with the object of achieving better yield, selectivity and lower requirement of ammonia of the title compound. The present invention relates to a process for producing 2-cyanopyrazine by reacting 2-methylpyrazine with ammonia and an oxygen source in a vapour phase employing a novel catalyst, wherein the catalyst comprises of an active component consisting of metal oxides of molybdenum, chromium and antimony coated on catalyst support material. In one embodiment, the present invention provides for a process for producing 2-cyanopyrazine by reacting 2-methylpyrazine with ammonia and air in a vapor phase, wherein the molar ratio of 2-methylpyrazine to ammonia is in the range of 1:1 to 10 preferably 1:2 to 8 and most preferably 1:2 to 5 and the molar ratio of 2-methylpyrazine to air is in the range of 1:10 to 80 preferably 1:20 to 70 and most preferably 1:20 to 60. In another embodiment, the present invention provides for a process for producing 2-cyanopyrazine by reacting 2-methylpyrazine with ammonia and oxygen, wherein the oxygen source comprises of air. In one another embodiment, the present invention provides for a process for producing 2-cyanopyrazine from 2-methylpyrazine which comprises of contacting with ammonia and oxygen source in the presence of a catalyst, wherein the catalyst comprises of an active component consisting of metal oxides of molybdenum, chromium and antimony loaded on alumina. In still another embodiment, the present invention provides for a process for producing 2-cyanopyrazine from 2-methylpyrazine which comprises of contacting with ammonia and oxygen source in the presence of a catalyst, wherein the active component of the metal mixed oxides is repeatedly coated on the catalyst support and the loading of active material on the catalyst support is in the range of 10-20%. In yet another embodiment, the present invention provides for a process for producing 2-cyanopyrazine from 2-methylpyrazine comprising a novel catalyst consisting of metal oxides of molybdenum, chromium and antimony, wherein the molar ratios of molybdenum : antimony : chromium are in the range of 1-9 : 0-8 : 1-18 and the said active component being supported on alumina. In yet still another embodiment, the present invention provides for a process for producing 2-cyanopyrazine by ammoxidation of 2-methylpyrazine employing a novel catalyst, wherein the catalyst support material comprises alpha alumina of surface area less than 10 sq.m/g.In an embodiment, the present invention provides for a process for producing 2-cyanopyrazine from 2-methylpyrazine comprising reacting 2-methylpyrazine with ammonia and air employing a novel catalyst, wherein the catalyst is provided in the form of a fixed catalyst bed and the bed temperature is in the range of 380-450°C. In one embodiment, the present invention provides for a process for producing 2-cyanopyrazine by ammoxidation of 2-methylpyrazine employing a novel catalyst, wherein the catalyst is prepared by the process comprising, preparing a solution of weak organic acid in water, adding a molybdenum source to the solution, heating the same upto 60-90°C and mixing the solution thoroughly, then adding chromium oxide and antimony oxide to the resulting solution and again heating and mixing the solution to obtain slurry, adding a catalyst support material in the required shape and size till a final coated mass is obtained and drying the mass and calcining the dried mass at a temperature range of 500-550°C. In yet another preferred embodiment, there is provided a process for producing a novel catalyst, wherein molar ratio of said weak organic acid to the solution of molybdenum is in the range of 1 : 1 to 4 by weight. In another embodiment, there is provided a process for producing a novel catalyst, wherein the molybdenum source is selected from ammonium molybdate, the antimony source is selected from antimony pentoxide and chromium source is selected from chromium trioxide respectively. 4. Detailed Description of the Invention: Preferred embodiments of the present invention disclose the process for producing 2-cyanopyrizine by reacting 2-methylpyrazine with ammonia and air in vapor phase employing a novel catalyst. The disclosed processes comprises lower mole ratio of ammonia and obviates the formation of byproducts. After extensive study and analysis, it was found that in the preparation of 2-cyanopyrazine by the ammoxidation of 2-methylpyrazine, the reaction conditions can be milder and obtained selectivity could be high for 2-cyanopyrazine when the catalyst of the present invention is used carefully selected active metal oxides and their composition i.e., molar ratios of active metal oxides, The catalyst of the present invention comprises of active metal oxides of molybdenum, chromium and antimony. The catalyst of the present invention also has good resistance to heat and reduction and is safe in operation. When the molar ratio of air and ammonia is used and molybdenum chromium and antimony oxides as disclosed herein are used as catalyst in the preparation of 2-cyanopyrazine by the ammoxidation of 2-methylpyrazine, abnormal reaction conditions are suppressed and 2-cyanopyrazine is obtained in good yield and selectivity. The catalyst of the invention also has a good resistance to heat and reduction and is safe in operation. Process for the production of 2-cyanopyrazine disclosed herein comprises contacting the ammonia and air with a catalyst bed temperature maintained in the range of 350 to 450°C. The 2-methylpyrazine is preferably in the form of vapors when contacted with the catalyst bed. The molar ratio of the 2-methylpyrazine to ammonia is in the range of 1:1-10 preferably 1:2-8 and most preferably 1:2-5. The molar ratio of the 2-methylpyrazine to air is in the range of 1:20-80 and preferably 1:20-70 and most preferably 1:20-60. A novel catalyst disclosed herein prevents the formation of byproducts such as, pyrazine, pyrazinamide and pyrazine mono carboxylic acid. Catalyst of the present invention include molybdenum: antimony: chromium oxides and their molar ratios are 1-9:0-8:1-18 and the catalyst support material comprises of alumina, surface area of less than 10 sq.m/g. The active component may be repeatedly coated on the catalyst support to obtain the desired percentage of loading. The loading of the active material on the catalyst support should preferably be in the range of 10-20%. Preferred embodiments are further illustrated in the following examples: Process for preparing of the Catalyst Example 1 Oxalic acid 35 g was taken in 300 g of DM water in a SS vessel with a mechanical stirrer. Ammonia molybdate 68 g was added under stirring. Heating was slowly started and reached to 70-80°C, chromium trioxide 48 g was added and the mixture was heated to concentrate the solution till thick slurry was obtained. The support material 300 g in the form of 3-4 mm pellets was added to the above slurry under constant agitation and heating was continued. The coated thick mass obtained was carefully dried at 120-130°C for about 2-3 hrs. The dried mass was then calcined in a muffle furnace at 500-550°C for about 5-6 hrs. The calcined mass was sieved to remove the powder and loosely held active material present on the support. If desired, repeated coatings can be carried out to ensure necessary percentage loading on the support material of the active ingredients. The coated mass thus obtained was between 15-20% by weight of the support. The molar ratio of the active material was 1:9 for molybdenum and chromium oxides. Example 2 Oxalic acid 35 g was taken in 300 g of DM water in a SS vessel with a mechanical stirrer. Ammonia molybdate 68 g was added under stirring. Heating was slowly started and reached to 70-80°C, chromium trioxide 48 g was added and the mixture was heated to concentrate the solution till thick slurry was obtained. The support material 300 g in the form of 3-4 mm pellets was added to the above slurry under constant agitation and heating was continued. The coated thick mass obtained was carefully dried at 120-130°C for about 2-3 hrs. The dried mass was then calcined in a muffle furnace at 500-550°C for about 5-6 hrs. The calcined mass was sieved to remove the powder and loosely held active material present on the support. If desired, repeated coatings can be carried out to ensure necessary percentage loading on the support material of the active ingredients. The coated mass thus obtained was between 10-15% by weight of the support. The molar ratio of the active material was 1:9 for molybdenum and chromium oxides. Example 3 Oxalic acid 35 g was taken in 300 g of DM water in a SS vessel with a mechanical stirrer. Ammonia molybdate 68 g was added under stirring. Heating was slowly started and reached to 70-80°C, chromium trioxide 48 g was added and the mixture was heated to concentrate the solution till thick slurry was obtained. The support material 300 g in the form of 3-4 mm pellets was added to the above slurry under constant agitation and heating was continued. The coated thick mass obtained was carefully dried at 120-130°C for about 2-3 hrs. The dried mass was then calcined in a muffle furnace at 500-550°C for about 5-6 hrs. The calcined mass was sieved to remove the powder and loosely held active material present on the support. If desired, repeated coatings can be carried out to ensure necessary percentage loading on the support material of the active ingredients. The coated mass thus obtained was between 10-15% by weight of the support. The molar ratio of the active material was 9:1 for molybdenum and chromium oxides. Example 4 The same procedure as in example 1 was followed by adding antimony pentoxide also to the example 1 catalyst and maintained molar ratio was 1:4: 9 for molybdenum : antimony : chromium. Example 5 The same procedure as in example 1 was followed by adding antimony pentoxide also to the example 1 catalyst and maintained molar ratio was 1:8:18 for molybdenum : antimony : chromium. The catalysts prepared in the above mentioned examples were individually used in the preparation of 2-cyanopyrazine from 2-methylpyrazine and better results were obtained. The following procedure was adopted for evaluating the catalyst and optimizing the process parameters. 2-methylpyrazine was vaporized at 275-375 C in a preheater and the superheated vapors were allowed to pass over a catalyst bed maintained at a temperature in the range of 350-425°C. Ammonia and air are allowed to enter and mix with the 2-methylpyrazine above the catalyst bed. The reaction is carried out in a steel reactor with 1-meter length and 23 mm ID mounted in a vertical zone tubular furnace. Above the catalyst bed, packing of inert material such as porcelain or glass beads was placed to ensure proper distribution of the reactants. The reactor tube is heated and the temperature is maintained as per the requirement. The feeder line is provided with three attachments, first for air, second for ammonia and third for 2-methylpyrazine. The first zone of the reactor tube packed with inert acts as a vaporizer and super heater. Condenser traps and heater scrubbers are attached to the bottom outlet of the reactor in order to quench the product, as soon as they exit the catalyst bed. Temperature of these condensers is maintained below 10°C by the circulation of chilled brine. The process for producing the 2-cvanopvrazine: Example 6 A run was carried out over 75 cc of example 1 catalyst and followed the procedure described above, keeping the molar ratio of 2-methylpyrazine : air = 1:60 at 425°C and varying the mole ratio of ammonia. Results are tabulated in Table 1. Example 7 The same procedure as in example 6 was followed except keeping the molar ratio of 2-methylpyrazine : ammonia = 1:3 at 425°C and varying the mole ratio of air and results are represented in Table 2. Example 8 The same procedure as in example 6 was followed except keeping the molar ratio of 2-methylpyrazine : ammonia : air = 1:3:60 and varying the temperature and results are provided in Table 3. Example 9 A run was carried out over 75 cc of example 2 catalyst and following the procedure described in example 5 and keeping the molar ratio of 2-methylpyrazine : ammonia : air = 1:3:60 at 425°C. Yield, conversion and selectivity were 35.5%, 48% and 74% respectively. Example 10 The same procedure as in example 9 was followed except that the catalyst used was as used in example 3 and obtained yield, conversion and selectivity were 24%, 51% and 47% respectively. Example 11 The same procedure as in example 9 was followed except that the catalyst used was as used in example 4 and obtained yield, conversion and selectivity were 55%, 65% and 90% respectively. Example 12 The same procedure as in example 9 was followed except that the catalyst used was as used in example 5 and obtained yield, conversion and selectivity were 36%, 47% and 76% respectively. Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims Table 1 Table 2 Table 3 (Table Removed) We Claim: 1. A process for producing 2-cyanopyrazine consisting essentially of: reacting 2-methylpyrazine with ammonia in a molar ratio of 1:2-5 and an oxygen source in a molar ratio of 1:20-80 in a vapour phase employing a novel catalyst in the form of catalyst bed, wherein the catalyst comprises of an active component consisting of metal oxides of molybdenum, chromium and antimony coated on catalyst support material in the range of 10 to 20% by weight. 2. The process according to claim 1, wherein the preferred molar ratio of 2-methylpyrazine to ammonia is 1:2-3. 3. The process according to claim 1, wherein the said oxygen source is air. 4. The process according to claim 1, wherein the preferred molar ratio of 2-methylpyrazine to oxygen source is in the range of 1:20-60. 5. The process according to claim 1, wherein said 2-methylpyrazine is in vapor form when contacted with the catalyst. 6. The process according to claim 1, wherein the catalyst bed is maintained at a temperature ranging between 380-450°C. 7. The process according to claim 1, wherein said catalyst support material comprises alpha alumina with a surface area less than 10 sq.m/gm. 8. The process for producing 2-cyanopyrazine according to claim 1, wherein said catalyst bed is provided by adding a molybdenum source to a solution of oxalic acid in water, heating and mixing the solution thoroughly, adding a chromium source and an antimony source to the resulting solution, heating the resultant solution and mixing the same to obtain a slurry, adding a catalyst support material alpha alumina of surface area less then 10 sq.m/gm in the range of 10 to 20% by weight to the slurry until a final coated mass is obtained, drying the mass and calcining the dried mass to obtain the catalyst bed and employing the same for producing 2-cyanopyrazine. 9. The process according to claim 8, wherein the temperature sufficient to form said slurry is in the range of 60-90°C. 10. The process according to claim 8, wherein said dried mass is calcined at a temperature in the range of 500-550°C. 11. The process according to claim 8, wherein said molybdenum source is ammonium molybdate. 12. The process according to claim 8, wherein said chromium source is chromium trioxide 13. The process according to claim 8, wherein said antimony source is antimony pentoxide. 14. The process according to claim 8, wherein the adding catalyst support material is in the range of 15 to 20% by weight. 15. The process according to claim 8, wherein the ratio of chromium is higher than that of molybdenum and antimony. 16. The process according to claim 8, wherein the molar ratio of molybdenum: antimony and chromium is in the range of 1-9:0-8:1-18. 17. The process for producing 2-cyanopyrazine substantially as hereinbefore described with reference to the examples.

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673-del-2004-abstract.pdf

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673-del-2004-correspondence-others.pdf

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673-del-2004-form-2.pdf

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