Gas separation process for production of hydrogen by autothermal reforming of natural gas, with carbon dioxide recovery

1. A gas separation process for production of hydrogen by autothermal reforming of natural gas, wherein the process comprises the following steps:

(a) introducing natural gas, steam, and oxygen into an autothermal reformer, to produce a gas mixture comprising carbon dioxide, carbon monoxide, hydrogen, water vapor, and residual natural gas;

(b) cooling the gas mixture to condense out water;

(c) treating the resultant gas mixture to remove hydrogen, to produce a hydrogen product stream and a hydrogen-depleted gas mixture;

(d) providing a membrane having a feed side and a permeate side, wherein the membrane is selective to carbon dioxide over hydrogen, carbon monoxide, and methane;

(e) passing the hydrogen-depleted gas mixture across the feed side;

(f) withdrawing from the permeate side a permeate stream that is enriched in carbon dioxide relative to the hydrogen-depleted gas mixture;

(g) withdrawing from the feed side a residue stream that is depleted in carbon dioxide relative to the hydrogen-depleted gas mixture; and

(h) passing the residue stream as a recycle stream back to the autothermal reformer as feedstock.

2. A process in accordance with claim 1 , wherein the residue stream is treated to remove inerts prior to being passed as a recycle stream back to the autothermal reformer in step (h).

3. A process in accordance with claim 1 , wherein step (c) comprises a pressure swing adsorption step.

4. A process in accordance with claim 1 , wherein step (c) comprises a membrane-based separation step using membranes that are selectively permeable to hydrogen over carbon dioxide.

5. A process in accordance with claim 1 , wherein the membrane has a selectivity to carbon dioxide over hydrogen of at least 6.

6. A process in accordance with claim 5 , wherein the membrane has a selectivity to carbon dioxide over hydrogen of at least 10.

7. A process in accordance with claim 1 , wherein the membrane has a carbon dioxide permeance of at least about 200 gpu.

8. A process in accordance with claim 1 , wherein the hydrogen-depleted gas mixture is compressed and condensed to produce high-purity carbon dioxide prior to being passed across the feed side of the membrane.

9. A process in accordance with claim 1 , wherein the carbon dioxide-enriched permeate stream is compressed and condensed to produce high-purity carbon dioxide.

10. A process in accordance with claim 1 , wherein the process results in the production of at least 20% more hydrogen than a conventional autothermal reforming process.

11. A gas separation process for production of hydrogen by autothermal reforming of natural gas, wherein the process comprises the following steps:

(a) introducing natural gas, steam, and oxygen into an autothermal reformer, to produce a gas mixture comprising carbon dioxide, carbon monoxide, hydrogen, water vapor, and residual natural gas;

(b) cooling the gas mixture to condense out water;

(c) providing a membrane having a feed side and a permeate side, wherein the membrane is selective to carbon dioxide over hydrogen;

(d) passing the gas mixture across the feed side;

(e) withdrawing from the permeate side a permeate stream that is enriched in carbon dioxide relative to the gas mixture;

(f) withdrawing from the feed side a residue stream that is depleted in carbon dioxide relative to the gas mixture;

(g) treating the residue stream to remove hydrogen, to produce a hydrogen product stream and a hydrogen-depleted gas stream; and

(h) passing the hydrogen-depleted gas stream as a recycle stream back to the autothermal reformer as feedstock.

12. A process in accordance with claim 11 , wherein the hydrogen-depleted gas stream is treated to remove inerts prior to being passed as a recycle stream back to the autothermal reformer in step (h).

13. A process in accordance with claim 11 , wherein step (g) comprises a pressure swing adsorption step.

14. A process in accordance with claim 11 , wherein step (g) comprises a membrane-based separation step using membranes that are selectively permeable to hydrogen over carbon dioxide.

15. A process in accordance with claim 11 , wherein the membrane has a selectivity to carbon dioxide over hydrogen of at least 6.

16. A process in accordance with claim 15 , wherein the membrane has a selectivity to carbon dioxide over hydrogen of at least 10.

17. A process in accordance with claim 11 , wherein the membrane has a carbon dioxide permeance of at least about 200 gpu.

18. A process in accordance with claim 11 , wherein the gas mixture is compressed and condensed to produce high-purity carbon dioxide prior to being passed across the feed side of the membrane.

19. A process in accordance with claim 11 , wherein the carbon dioxide-enriched permeate stream is compressed and condensed to produce high-purity carbon dioxide.

20. A process in accordance with claim 11 , wherein the process results in the production of at least 20% more hydrogen than a conventional autothermal reforming process.