Method for obtaining solutions of OTA in a concentrated sulfuric acid medium; said solutions; and method for preparing ONTA
View Patent ↗A method for obtaining solutions that contain 1,2,4-triazole-5-one (OTA) in concentrated sulphuric acid, includes using 3-amino-1,2,4-triazole (ATA) as a precursor of OTA. There is also provided a method for preparing 3-nitro-1,2,4-triazole-5-one (4) (ONTA) from the solutions.
1. A process for the preparation of 3-nitro-1,2,4-triazol-5-one, the process comprising:
producing a solution of 1,2,4-triazol-5-one in concentrated sulfuric acid, said producing comprising
preparing, in concentrated sulfuric acid, diazonium hydrogensulfate of formula:
by reaction, under cold conditions, in concentrated sulfuric acid, of at least one nitrite with 3-amino-1,2,4-triazole;
heating the reaction medium including said diazonium hydrogensulfate in order to produce said solution of 1,2,4-triazol-5-one; and
nitrating said 1,2,4-triazol-5-one by addition of concentrated nitric acid to said solution.
2. The process as claimed in claim 1 , wherein said concentrated sulfuric acid includes at least 75% by weight of sulfuric acid.
3. The process as claimed in claim 1 wherein the concentration of said 3-amino-1,2,4-triazole in the concentrated sulfuric acid is between 0.3 and 2 mol/l.
4. The process as claimed in claim 1 , wherein said at least one nitrite is chosen from organic nitrites, alkali metal nitrites and alkaline earth metal nitrites.
5. The process as claimed in claim 1 , wherein the nitrite(s)/3-amino-1,2,4-triazole molar ratio is between 1 and 2.
6. The process as claimed in claim 1 , wherein said at least one nitrite is reacted with said 3-amino-1,2,4-triazole at a temperature between 0° C. and 10° C.
7. The process as claimed in claim 1 , wherein said heating comprises two phases:
a first phase of rise in temperature, carried out with control of the release of gas, so as to prevent any overflowing, up to a temperature T of at least 50° C., and
a second phase of maintaining at said temperature T.
8. The process as claimed in claim 7 , wherein the rise in temperature of the first phase is carried out according to a gradient of 9° C./h to 16° C./h.
9. The process as claimed in claim 1 , wherein said concentrated nitric acid includes at least 75% by weight of nitric acid.
10. The process as claimed in claim 1 , wherein said concentrated nitric acid is added in an HNO 3 /1,2,4-triazol-5-one molar ratio of between 1.9 and 2.5.
11. The process as claimed in claim 1 , wherein from 10 to 20% by weight of water (H 2 O) is added to said solution, before said addition of concentrated nitric acid.
12. The process as claimed in claim 1 , wherein the producing and nitrating occur in a same reactor.
13. The process as claimed in claim 1 , further comprising recovering the 3-nitro-1,2,4-triazol-5-one, said recovering comprising a precipitation of the latter by cooling the reaction medium obtained on conclusion of the nitration.
14. The process as claimed in claim 13 , wherein the cooling is carried out to a temperature of between 8 and 12° C.
15. The process as claimed in claim 1 , wherein said concentrated sulfuric acid includes at least 95% by weight of sulfuric acid.
16. The process as claimed in claim 1 , wherein the concentration of said 3-amino-1,2,4-triazole in the concentrated sulfuric acid is between 1.3 and 1.6 mol/l.
17. The process as claimed in claim 1 , wherein said at least one nitrite consists of sodium nitrite (NaNO 2 ).
18. The process as claimed in claim 7 , wherein the temperature T is below 120° C.
19. The process as claimed in claim 1 , wherein said concentrated nitric acid includes at least 95% by weight of nitric acid.
20. The process as claimed in claim 10 , wherein said concentrated nitric acid is added in an HNO 3 /1,2,4-triazol-5-one molar ratio of between 1.95 and 2.2.
21. The process as claimed in claim 13 , wherein from 8 to 15% by weight of water (H 2 O) are added to said cooled reaction medium for selective precipitation of said 3-nitro-1,2,4-triazol-5-one.