Process for producing pyridine carboxylic acids
Disclosed herein cost effective and ecofriendly large scale process for producing pyridine carboxylic acid with high purity and yield at industrial scale.
1. A process for preparing pyridine carboxylic acid, the process comprising:
oxidizing alkyl pyridine with oxygen and/or air in presence of water and a vanadia based catalyst, and
isolating the pyridine carboxylic acid,
wherein the said catalyst comprises pellets of an oxide of vanadium with oxide of titanium as a support and oxide of metalloid as an additive and wherein the said catalyst pellets are packed in a reactor in a multilayer arrangement, wherein the catalyst includes pellets having x(V 2 O 5 )-y(TiO 2 )-z(M a O b ), where x=5-40% by weight, y=95-60% by weight, z=1-10% by weight and M is the metalloid additive.
2. The process according to claim 1 , wherein the oxide of vanadium to oxide of titanium to oxide of metalloid additive is having a mole ratio of 1:5-15:0.1-0.5.
3. The process according to claim 1 , wherein the packing of catalyst bed is done with a compound selected from the group comprising silica, alumina, silicon carbide, titanium oxide, diatomaceous earth, zeolite and mixtures thereof.
4. The process according to claim 1 , wherein the packing of catalyst bed is done with inert alumina mixed with the catalyst and arranged in the multilavers, wherein each layer has a different proportion of the catalyst pellets and inert alumina.
5. The process according to claim 1 , wherein the metalloid additive is selected from the group comprising boron, silicon, germanium, arsenic, antimony, tellurium, polonium and mixtures thereof.
6. The process according to claim 1 , wherein the oxidation is carried out in the temperature range of 240 to 380° C.
7. The process according to claim 1 , wherein the mole ratio of oxygen and alkyl pyridine is in the range of 10-40:1.
8. The process according to claim 1 , wherein the mole ratio of water: alkyl pyridine is in the range of 20-80:1.
9. The process according to claim 1 , wherein the catalyst support has a specific surface area greater than 100m 2 /g.
10. The process according to claim 1 , wherein the catalyst has a specific surface area in the range 20-50 m 2 /g.
11. The process according to claim 1 , wherein the oxidation is carried out at a weight hour space velocity (WHSV) of 0.01 to 2.0 hr −1 .
12. The process according to claim 1 , wherein the amount of vanadium oxide is in the range of 5-40% by weight.
13. The process according to claim 1 , wherein the pyridine carboxylic acid is isolated by scrubbing or by extraction.
14. The process according to claim 13 , wherein the scrubbing or extraction is carried out with solvent selected from water, methanol, ethanol, n-propanol, isopropanol, n-butanol, acetone, pyridine, tetrahydrofuran, furfuryl alcohol, tetrahydrofurfuryl alcohol, acetic acid, formic acid and mixtures thereof.
15. The process according to claim 1 , wherein the isolation is performed in the temperature range of 5-120° C. under atmospheric or super atmospheric or low pressure condition.
16. The process according to claim 1 , wherein the alkyl pyridine is β-picoline and the pyridine carboxylic acid is nicotinic acid, wherein the alkyl pyridine is γ-picoline and the pyridine carboxylic acid is isonicotinic acid or wherein the alkyl pyridine is α-picoline and the pyridine carboxylic acid is picolinic acid.
17. The process according to claim 1 , the process comprising:
preparing pyridine carboxylic acid by oxidizing alkyl pyridine with oxygen and/or air in presence of water to obtain product gases;
scrubbing the resultant product gases in a primary absorber;
optionally scrubbing unscrubbed gases in a secondary absorber;
desirably treating a resultant pyridine carboxylic acid solution with activated carbon to obtain a mass;
filtering the resultant mass;
optionally crystallizing the resultant mass, and
drying the filtered mass or crystallized mass to obtain pyridine carboxylic acid.
18. The process according to claim 17 , wherein the scrubbing in primary absorber is performed at a temperature range of 5-120° C. under atmospheric or super atmospheric or low pressure condition.
19. The process according to claim 17 , wherein the pyridine carboxylic acid is dried at a temperature range of about 80-120° C.
20. The process according to claim 17 , wherein flue gases from the absorber, scrubbed liquid and mother liquor obtained in the process are recycled.
21. The process according to claim 17 , wherein the alkyl pyridine is β-picoline and the pyridine carboxylic acid is nicotinic acid, wherein the alkyl pyridine is γ-picoline and the pyridine carboxylic acid is isonicotinic acid or wherein the alkyl pyridine is α-picoline and the pyridine carboxylic acid is picolinic acid.
22. The process according to claim 4 , wherein the inert alumina and catalyst relative proportion ranges from about 25% to about 100% being the catalyst.