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 at least 10 mol % nitrous oxide (N 2 O);
converting the N 2 O present in the offgas to nitrogen oxide (NO x ) (x=1 or 2) in a yield of greater than 15% by passing the offgas through a reactor operating at a temperature of 2400° F. or greater and wherein the reactor operates at a pressure of 15 psig of less;
converting the NO x to nitric acid; and
optionally recycling the nitric acid to produce additional adipic acid.
2. The process according to claim 1 , wherein the reactor operates at a temperature range of 2400 to 3500° F.
3. The process according to claim 1 , wherein the offgas prior to passing through the reactor comprises 15 to 90 mol % N 2 O.
4. The process according to claim 1 , wherein the offgas prior to passing through the reactor further comprises less than 2 mol % water.
5. The process according to claim 1 , wherein the reactor has a length to diameter ratio (L/D) of 3 to 30.
6. The process according to claim 1 , wherein the offgas passes through the reactor at a rate of greater than 1000 pph.
7. The process according to claim 1 , wherein the offgas prior to passing through the reactor further comprises less than 2 mol % NO x .
8. The process according to claim 1 , wherein the offgas prior to passing through the reactor is preheated to greater than 900° F.
9. The process according to claim 1 , wherein the offgas prior to passing through the reactor is treated to reduce an amount of at least one of water and NO x present in the offgas.
10. A self-sustaining process for preparing nitrogen oxide (NO x ) (x=1 or 2) from nitrous oxide (N 2 O), comprising:
preheating a reactor to a temperature of greater than 1600° F.;
passing a feedgas comprising N 2 O through the reactor operating at a temperature of 2400 to 3500° F. and wherein the reactor operates at a pressure of 15 psig of less;
wherein heat generated by reaction of the N 2 O in the reactor is used to preheat the feedgas to a temperature between 900 and 1600° F. prior to entry of the feedgas into the reactor at a rate that does not require application of an external heat source to sustain the conversion, and
wherein the N 2 O is converted to NO x in a yield of greater than 15%.
11. The self-sustaining process according to claim 10 , wherein the feedgas prior to passing through the reactor comprises 30 to 80 mol % N 2 O.
12. The self-sustaining process according to claim 10 , wherein the feedgas prior to passing through the reactor comprises less than 2 mol % water.
13. A process for converting nitrous oxide (N 2 O) to nitrogen oxide (NO x ) x=1 or 2), comprising:
obtaining a feedgas containing N 2 O;
optionally subjecting the feedgas to conditions sufficient to increase the concentration of the N 2 O in the feedgas;
optionally treating the feedgas to reduce the amount of one or more components present in the feedgas having a negative impact on conversion of the N 2 O to NO x ;
converting the N 2 O in the feedgas to NO by passing the feedgas through a reactor operating at a temperature of 2400 to 3500° F. and wherein the reactor operates at a pressure of 15 psig of less; and
optionally converting the NO x to a different compound or material,
wherein the N 2 O is converted to NO x in a yield of greater than 15%.
14. The process according to claim 13 , wherein the feedgas prior to passing through the reactor comprises 40 to 80 mol % N 2 O.
15. The process according to claim 13 , wherein the one or more components present in the feedgas having a negative impact on conversion of the N 2 O to NO x include water, NO and NO 2 .