NZ548652A

NZ548652A - Catalyst for synthesis of 2-and 4-picolines, process for preparing 2- and 4-picoline and process for preparing the catalyst

Info

Publication number: NZ548652A
Application number: NZ548652A
Authority: NZ
Inventors: Pashupati Dutta; Subhash Chandra Roy; Shyam Kishor Roy; Tarun Kanti Goswami
Original assignee: Council Scient Ind Res
Priority date: 2003-12-31
Filing date: 2003-12-31
Publication date: 2009-12-24

Abstract

Provided is the use of a catalyst comprising a heteropoly acid selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid and provided on a support, for the synthesis of 2-and 4-picolines. Further provided are 2- and 4-picolines when prepared by the said process.

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number 548652 ; 548652 WO 2005/063389 , PCMN2003/000467 CATALYST FOR SYNTHESIS OF 2- ASD 4-PXCOL1NES, PROCESS FOR PREPARING 2- AKD 4-PICOIiIEE AMD PROCESS FOR PREPARING THE CATALYST Field of the invention The present invention provides a catalyst composite for the synthesis of 2- and 4-picolines. The present invention also provides a process for the preparation of a catalyst 5 useful for the synthesis of 2- and 4- Pieulines. The present invention also provides a process for the preparation of 2- and 4- picolines using said-novel catalyst. The present invention finds its usage in preparation of various intermediates for pharmaceuticals and agrochemicals. 2-Picoline is one of the main components in manufacture of pesticides. Major outlet for 4-Picoline is for the synthesis of 4-VinylPyridine and Iso-Nicofinic Acid Hydrazide (INH), an 10 anti-tubercular drug. Background of the invention Commercially important sources of pyridine bases are tar and saturated liquor obtained by the carbonization of coal. However, the stringent specifications laid down for these products in pharmaceuticals and agricultural applications cannot be met from natural 15 sources, namely from coal carbonization byproducts. Amongst the various- synthetic routes, • the reaction between acetaldehyde and ammonia is the most common one known in the prior art for making pyridine bases. Acids have been used as catalysts or co-catalysts in a number of reactions. U.S. Patent 2,186,392 reveals that ethanolamines may be produced from ammonia or a primary amine .20 and ethylene oxide and a salt of a weak acid, such as ammonium carbonate, in the presence of an aliphatic radical which is positive with respect to hydrogea German Patent 844,449 (CA 48:1429c) informs tertiary amines with hydroxyalkyl radicals may be made from ammonia, primary or secondary amines and an alkylene oxide at a temperature of from 30°C to 60°C, with improved yields being possible if water or a weak acid is also present. British Patent No. 25 497,093, (CA 36:4131-8) indicates that monoalkanolamines may be made from olefin oxides and ammonia in the presence of Water and an acid. The reaction of acetaldehyde or certain other low molecular weight aldehydes and ammonia either in the absence or presence of methanol and/or formaldehyde to yield pyridine and alkyl derivatives thereof has heretofore been carried out in the presence of amorphous 30 silica-alumina composites containing various promoters. The yields of desired products using the latter catalysts have been poor. ALkylpyridines have also been synthesized, as reported in Advances in Catalysis, Volume 18, page 344 (1968) Academic Press, Inc., New York, N.Y., by passing gaseous acetaldehyde and ammonia over crystalline aluminosilicates, NaX and H-mordenite. While initial conversion utilizing these materials as catalysts was high, catalyst 1 548652 deactivation by coking was rapid, providing a commercially unattractive system, characterized by poor catalytic stability. US Patent 4,220, 783 provides a method for synthesizing pyridine or alkylpyridines by reacting ammonia and a carbonyl reactant which is an aldehyde containing 2 to 4 carbon atoms, 5 a ketone containing 3 to 5 carbon atoms or mixtures of said aldehydes and/or ketones under effective conditions in the presence of a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12 and a constraint index within the approximate range of 1 to 12 and recovering from the resulting reaction mixture, a product containing at least one compound of pyridine or an alkylpyridine. Addition of methanol and/or 10 formaldehyde to the feed improves selectivity to unsubstituted pyridine. The yields of desired products have been poor. Manufacture of pyridine bases by employing the catalyst causes environmental pollution because these routes use toxic Th02 and CdO. The catalyst preparation involves tedious method for the preparation of silica alumina gel. Objects of the invention 15 The rnain object of the invention is to provide a catalyst suitable for the conversion of acetaldehyde and ammonia to 2-and 4-Picolines which obviates the drawbacks as detailed above. Another object of tie invention is to provide a stable catalyst for the conversion of acetaldehyde and ammonia. 20 Still another object of the invention is to provide a catalyst which is highly selective and active. A further object of the invention is to at least provide the public with a useful choice from currently available products, and/or to provide the public with a useful choice from currently available processes. 25 Summary of the invention Accordingly the present invention provides a catalyst useful for synthesis of 2-and 4-Picolines which comprises a heteropoly acid selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid provided on a support. 30 In one embodiment of the invention, the support is selected from the group consisting of silica gel, alumina, silica-alumina, clays and montmorillonite. 2 548652 Hie present invention also provides a process for the preparation of a catalyst useful for the synthesis of 2-and 4-picolines, the process comprising dissolving a heteropoly acid in distilled water; mixing the resulting mixture with desired amount of a binder to obtain a sluny; stirring the sluny till uniform impregnation is achieved; djying the slurry in air at 200- 250°C 5 for a time period in the range of 0.5 to 1.5 hours; further heating the slurry at a 2A 548652 WO 2005/063389 / PC77IN20A3/000467 temperature in the range of 300 to 400°C for time period in the range of 0.5 to 1.5 hours and cooling the resultant product to room temperature in a desiccator to get the desired catalyst. In one embodiment of the invention the heteropoly acid is selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid. In another embodiment of the invention the binder is selected from the group consisting of silica, alumina, silica-alumina, clays and montmorillonite. In an nth pit embodiment of the invention, the heteropoly acid is dissolved in distilled water in a ratio of 0.5:4.5 (w/w). In another embodiment of the invention, the binder comprises silica gel of mesh size 6-14. In yet another embodiment of the invention, the slurry is stirred for a time period in the range of 30-40 minutes. The present invention also provides for a process for the preparation of 2- and 4-picolines which comprises reacting acetaldehyde and ammonia under heat in the presence of a catalyst comprising a composite of a heteropolyacid impregnated on a support, the catalyst being present in an amount in the range of 5 to 15 wt %, and separating the 2- and 4- picoline formed. In one embodiment of the invention, the acetaldehyde and ammonia are taken in a ratio of 0.8 to 1.2 (w/w) and are reacted at a temperature in the range of 3 00 to 500°C. In another embodiment of the invention, the reaction is carried out in a glass reactor. In yet another embodiment of the invention, the weight hourly space velocity of the acetaldehyde and ammonia is maintained in the range of 0.1 to 10 g/g of catalyst (preferably 1 to 3). In yet another embodiment of the invention, the 2- and 4-picolines are separated by fractional distillation. Detailed description of the invention The present invention provides a catalyst useful for synthesis of 2- and 4- Picoiines which is prepared by dissolution of a heteropoly acid in distilled water in a suitable proportion in the range of 0.5:4.5 (w/w). The resulting mixture is then mixed with desired amount of a binder such as silica gel (having mesh size 6-14) and the slurry obtained stirred for a time period in the range of 3 0-40 minutes to get a uniform impregnation. After uniform impregnation is obtained, the slurry is first dried in air at a temperature in the range of 200-2506C for a time period in the range of 0.5 to 1.5 hours and then further heated at temperature 548652 in the range of 300 to 400°C for time period in the range of 0.5 to 1.5 hours. The resulting product is then cooled to room temperature in a desiccator to get the desired catalyst The heteropoly acid is selected from silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid and the binder is from silica, alumina, silica-5 alumina, clays, montmorilonite. The catalyst obtained is useful for the synthesis of 2-and 4-picolines by heating acetaldehyde and ammonia in a ratio of 0.8 to 1.2 (w/w) at a temperature in the range of 300 to 500°C, The amount of the catalyst is in the range of 5 to 15 wt % and the reaction is carried out preferably in a glass reactor. The reaction is carried out by maintaining weight hourly space 10 velocity of the feed, comprising of acetaldehyde and ammonia, between 0.1 to 10 g/g of catalyst (preferably 1 to 3). The pyridine bases and product obtained are analyzed by by known spectrochromatographic methods and the pyridine bases separated from the desired products by conventional fractional distillation. The novelty of the present invention lies in preparing the catalyst for the conversion of 15 acetaldehyde and ammonia to 2-and 4-picolines in an ecofriendly manner. This process avoids environmental pollution in comparison to prior art processes. Throughout this specification unless the context requires otherwise, the words "comprise", "comprising" and the like, are to be construed in an inclusive sense as opposed to an exclusive sense, that is to say, in the sense of "including, but not limited to". 20 The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in New Zealand. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. 25 Example-I Preparation of the Catalyst: Silica gel, mesh size 6-14, was used as the silica support. Phosphotungstic acid (10 g) was dissolved in water (25 ml) and the solution was mixed with silica gel (100 g). The slurry was stirred to get a uniform impregnation, dried in air at 200-250°C for one hr. , then at 400°C for one hour, and finally cooled to room 30 temperature in a desiccator. This catalyst was used for the reaction between acetaldehyde and ammonia. 4 548652 The experiment was carried out in a downward flow glass reactor of internal diameter of 2 cm and of sufBcient length which was kept in a furnace of length 32 cm. In the middle of the reactor was kept the catalyst (10 g) made and heated to 380°C with the help of a tubular electrical furnace. Acetaldehyde was fed at a rate of 9.5 rol/hr and ammonia was fed at a rate 60 5 ml/min. The products formed in 2 hours were condensed in an ice cooled receiver, weighed and analyzed by gas chromatography (fitted with FED using 2 m x 3 mm SS column containing 30 % glycerol on chromosorb-p. The column temperature was maintained at 135°C and nitrogen flow was 30 ml/min.) Pure standard substances were-used for calibration. Conversion of acetaldehyde to picolines was found to be 50-60%. 4A </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 548652 WO 2005/063389 , PCT/IN2003/00046 7 Example-2 Preparation of the Catalyst: Silica gel, mesh size 6-14, was used as the silica support Silicotungstic acid (10 g) was dissolved in water (25 ml) and the solution was mixed with silica gel (100 g). The sluny was stirred to get a uniform impregnation, dried in air at 5 225°C for one hr., then at 400°C for one hour, and finally cooled to room temperature in a desiccator. This catalyst was used for the reaction between acetaldehyde and amrnr.nia The experiment was carried out in a downward flow glass reactor of internal diameter of 2 cm and of sufficient length which was kept in a furnace of length 32 cm. In the middle of the reactor was kept the catalyst (10 g) made and heated to 400oC with the help of a tubular 10 electrical furnace. Acetaldehyde was fed at a rate of 9.5 ml/hr and ammonia was fed at a rate 60 ml/min The products formed in 2 hours were condensed in an ice cooled receiver, weighed and analyzed by gas chromatography (fitted with FID using 2 m x 3 mm stainless • steel column containing 30 % glycerol on chromosorb-p. The column temperature was maintained at 135°C and nitrogen flow was 30 ml/min.) Pure standard substances were used 15 for calibration. Conversion of acetaldehyde to picolines was found to be 55%. Example-3 Preparation of the Catalyst: Silica gel, mesh size 6-14, was used as the silica support. Vanadotungstic acid (10 g) was dissolved in water (25 ml) and the solution was mixed with silica gel (100 g). The slurry was stirred to get a uniform impregnation, dried in air at 20 210°C for one hr.; then at 400°C- for one hour, and finally cooled to room temperature in a desiccator. This catalyst was used for the reaction between acetaldehyde and ammonia. The experiment was carried out in a downward flow glass reactor of internal diameter of 2 cm and of sufficient length which was kept in a furnace of length 32 cm. In the middle of the reactor was kept the catalyst (10 g) made and heated to 370°C with the help of a tubular 25 electrical furnace. Acetaldehyde was fed at a rate of 9.5 ml/hr and ammonia was fed at a rate 60 ml/min The products formed in 2 hours were condensed in an ice cooled receiver, weighed and analyzed by gas chromatography (fitted with FID using 2 m x 3 mm stainless steel column containing 30 % glycerol on chromosorb-p. The column temperature was maintained at 135°C and nitrogen flow was 30 ml/min.) Pure standard substances we used 30 for calibration. Conversion of acetaldehyde to picolines was found to be 70%. The main advantages of the present invention are: 1, The process is very simple and economic.
2. The catalyst preparation avoids tedious methods in comparison to prior art processes 5 301061148 548652 We claim: I. The use of a catalyst comprising a heteropoly acid selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid and provided on a support, for the synthesis of 2-and 4-picolines. 5 2. The use of a catalyst as claimed in claim 1 wherein the support is selected from the group consisting of silica gel, alumina, silica-alumina, clays and montmorillonite.
3. A process for the preparation of a catalyst when used for the synthesis of 2 -and 4-picolines, the process comprising dissolving a heteropoly acid in distilled water; mixing the resulting mixture with desired amount of a support to obtain a slurry; stirring the slurry till uniform 10 impregnation is achieved; drying the slurry in air at 200-250°C for a time period in the range of 0.5 to 1.5 hours; further heating the slurry at a temperature in the range of 300 to 400°G for time period in the range of 0.5 to 1.5 hours and cooling the resultant product to room temperature in a desiccator to get the desired catalyst.
4. A process as claimed in claim 3 wherein the heteropolyacid is selected from the group 15 consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid.
5. A process as claimed in claim 3 wherein the support is selected from the group consisting of silica, alumina, silica-alumina, clays and montmorillonite.
6. A process as claimed in claim 3 wherein the heteropoly acid is dissolved in distilled water 20 in a ratio of 0.5:4.5 (w/w).
7. A process as claimed in claim 3 wherein the support comprises silica gel of mesh size 6-14.
8. A process as claimed in claim 3 wherein the slurry is stirred for a time period in the range of 30-40 minutes. 25
9. A process for the preparation of 2-and 4-picolines which comprises reacting acetaldehyde and ammonia under heat in the presence of a catalyst comprising a composite of a heteropolyacid impregnated on a support, the catalyst being present in an amount in the range of 5 to 15 wt %, and separating the 2-and 4-picoline formed.
10. A process as claimed in claim 9 wherein the acetaldehyde and ammonia are taken in a ratio 30 of 0.8 to 1.2 (w/w) and are reacted at a temperature in the range of 300 to 500°C.
II. A process as claimed in claim 9 wherein the reaction is carried out in a glass reactor. 6 301061148 548652
12. A process as claimed in claim 9 wherein weight hourly space velocity of the acetaldehyde and ammonia is maintained in the range of 0.1 to 10 g/g of catalyst.
13. A process as claimed in claim 12 wherein the weight hourly space velocity of the acetaldehyde and ammonia is maintained in the range of 1 to 3 g/g of the catalyst 5
14. A process as claimed in claim 9 wherein the the 2-and 4-picolines are separated by fractional distillation.
15. A process as claimed in claim 9 wherein the heteropolyacid is selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid and vanadotungstic acid. 10
16. A process as claimed in claim 9 wherein the support is selected from the group consisting of silica, alumina, silica-alumina, clays and montmorillonite.
17. A process as claimed in claim 9 wherein the support comprises silica gel of mesh size 6-
18. The use of a catalyst for the synthesis of 2- and 4-picolines substantially as herein
19. A process for the preparation of a catalyst when used for the synthesis of 2- and 4-picolines substantially as herein described with particular reference to the examples and excluding prior art.
20. A process for the preparation of 2- and 4-picolines substantially as herein described 14. 15 described with particular reference to the examples and excluding prior art. 20 excluding prior art. 25 COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH By Its Attorneys BALDWINS INTELLECTUAL PROPERTY 30 7 </div>