Process for preparation of nitrogen oxides and nitric acid from nitrous oxide
Described herein is an improved conversion of nitrous oxide (N 2 O) present as a by-product in a chemical process to NO x which can be further converted to a useful compound or material, such as nitric acid.
1. A process for preparing adipic acid, comprising:
reacting at least one of cyclohexanone and cyclohexanol with nitric acid to produce adipic acid and an offgas comprising:
nitrous oxide; and
optionally nitrogen;
converting the nitrous oxide present in the offgas to nitrogen oxide by passing the offgas through a reactor operating at a temperature of 2400° F. or greater and a pressure of 10 psig or less to yield a product composition comprising nitrogen oxide;
compressing the product composition; and
converting nitrogen oxide in the compressed product composition to nitric acid.
2. The process of claim 1 , wherein the compressing comprises: compressing the product composition to a pressure ranging from 15 psig to 150 psig.
3. The process of claim 1 , further comprising further comprising:
quenching the product composition to form a cooled product composition.
4. The process of claim 3 , wherein the cooled product composition has a temperature less than 1600° F.
5. The process of claim 3 , wherein the cooled product composition has a temperature ranging from 900° F. to 1400° F.
6. The process of claim 1 , further comprising:
preheating the offgas prior to the converting.
7. The process of claim 6 , wherein the off gas is preheated to a temperature less than 1800° F.
8. The process of claim 1 , wherein the reactor operates at a temperature greater than 2600° F.
9. The process of claim 1 , wherein the converting step has a yield greater than 15%.
10. A process for preparing adipic acid, comprising:
reacting at least one of cyclohexanone and cyclohexanol with nitric acid to produce adipic acid and an offgas having a temperature less than 800° F. and comprising
nitrous oxide; and
optionally nitrogen;
preheating the offgas in a preheater unit to a temperature less than 1800° F.;
converting the nitrous oxide present in the offgas to nitrogen oxide at a yield of greater than 15% by passing the offgas through a reactor operating at a temperature of 2400° F. or greater and at a pressure of 10 psig or less to yield a product composition comprising nitrogen oxide; and
converting the nitrogen oxide to nitric acid.
11. The process of claim 10 , wherein the preheater unit is separate from the reactor.
12. The process of claim 10 , wherein the off gas leaving the adipic acid production reaction is not treated to remove nitrogen oxide.
13. The process of claim 10 , wherein the preheated offgas is directly fed to the reactor.
14. The process of claim 10 , wherein the preheating comprises:
preheating the offgas in a preheater unit to a temperature ranging from 900° F. to 1500° F.
15. A process for preparing adipic acid, comprising:
reacting at least one of cyclohexanone and cyclohexanol with nitric acid to produce adipic acid and an offgas having a temperature less than 800° F. and comprising
nitrous oxide; and
optionally nitrogen;
preheating the offgas in a preheater unit to a temperature less than 1800° F.;
converting nitrous oxide present in the offgas to nitrogen oxide at a yield of greater than 15% by passing the offgas through a reactor operating at a temperature of 2400° F. or greater and at a pressure of 10 psig or less to yield a product composition comprising nitrogen oxide;
compressing the product composition; and
converting nitrogen oxide present in the compressed product composition to nitric acid;
wherein the reactor has a length to diameter ratio (L/D) of greater than 4; and
wherein no external heat is added to the reactor after start of reaction.
16. The process of claim 15 , wherein the offgas comprises greater than 60 mol % nitrous oxide.
17. The process of claim 15 , wherein the residence time of the feed gas from the preheater to the reactor is less than 30 seconds.
18. The process of claim 15 , further comprising further comprising:
quenching the product composition to form a cooled product composition; and
compressing the cooled product composition.
19. The process of claim 18 , wherein the cooled product composition has a temperature less than 1600° F.