Process for sulphur recovery with concurrent hydrogen production from NH
Disclosed is a method for the production of hydrogen from a H 2 S-containing gas stream also containing ammonia, comprising subjecting both gas stream to catalytic oxidative cracking of both the H 2 S and the NH 3 , so as to form H 2 , S 2 and N 2 . In this method, preferably, an additional amount of oxygen is added as compared to the amount used for H2S catalytic oxidative cracking. Also, preferably, the contact time of the gas stream with the catalyst is increased. The catalyst preferably is provided as a single bed, and then preferably comprises iron and molybdenum supported by a carrier comprising aluminum. The preferred carrier is alumina. The iron and molybdenum preferably are in the form of sulfides.
1. A method for the production of hydrogen from a H 2 S-containing gas stream, which gas stream also contains ammonia, comprising combining the gas stream with an oxygen containing gas stream to form a reactant mixture and subjecting said reactant mixture to catalytic oxidative cracking of both the H 2 S and the NH 3 , substantially autothermally at a temperature of from 900° C.-1500° C. so as to form H z , S z , and N 2 ,
wherein said catalytic oxidative cracking forms H 2 and S 2 according to the reactions:
H 2 S↔H 2 +0.5S 2 (dissociation or cracking reaction) (4)
4H 2 S+O 2 ↔2H 2 +2 H 2 O+2S 2 (H 2 formation reaction) (5); and
said catalytic oxidative cracking forms nitrogen and water from NH 3 according to the reaction
2NH 3 +1.5O 2 →N 2 +3H 2 O.
2. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted with a molar ratio H 2 S/O 2 in the feedstock higher than 2:1, and additional oxygen to provide a molar ratio NH 3 /O 2 ranging between 0.9 and 1.5.
3. A method according to claim 2 , wherein the ratio H 2 S/O 2 is 3:1-5:1.
4. A method according to claim 2 , wherein said catalytic oxidative cracking is performed so that the ratio between the volume of catalytic material in said catalytic oxidative cracking and the total volumetric feed flow rate is between 0.05 seconds and 5 seconds.
5. A method according to claim 1 , wherein the oxygen-containing gas-stream comprises at least 40% oxygen.
6. A method according to claim 5 , wherein the oxygen-containing gas-stream is oxygen having a purity of from 90%-100%.
7. A method according to claim 5 , wherein the oxygen-containing gas-stream comprises at least 60% oxygen.
8. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted under the influence of a single catalyst selected from the group consisting of Pt, Rh, Ru, Ir, Pd, Co, Mo, Ni, Fe, W, Cu, Cd and the corresponding sulphides.
9. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted under the influence of an oxidation catalyst and a different cracking catalyst.
10. A method according to claim 9 , wherein the oxidation catalyst is selected from the group consisting of one or more active components selected from Group VIII metals and the cracking catalyst is selected from the group consisting of metal sulphides.
11. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted over a single catalytic bed.
12. A method according to claim 11 , wherein the catalyst comprises iron and molybdenum, supported by a carrier comprising aluminum.
13. A method according to claim 12 , wherein the catalyst comprises both iron and molybdenum in the form of their respective sulfides.
14. A method according to claim 13 , wherein the oxygen-containing gas-stream is oxygen having a purity of from 90%-100%.
15. A method according to claim 12 , wherein the carrier is made up of Al 2 O 3 .
16. A method according to claim 12 , wherein the iron is present in the catalyst in a range of from 1 to 50% by weight.
17. A method according to claim 16 , wherein the iron is present in the catalyst in a range of 2% by weight.
18. A method according to claim 12 , wherein the molybdenum is present in the catalyst in a range of from 1 to 50% by weight.
19. A method according to claim 18 , wherein the molybdenum is present in the catalyst in a range of 6% by weight.
20. A method according to claim 1 , wherein the catalytic oxidative cracking is conducted substantially autothermally at a temperature of from 900° C.-1200° C.
21. A method according to claim 20 , wherein the catalytic oxidative cracking is conducted substantially autothermally at a temperature of about 1100° C.