Simultaneous shift-reactive and adsorptive process at moderate temperature to produce pure hydrogen

• US 20040081614A1
• Filed: 10/25/2002
• Published: 04/29/2004
• Est. Priority Date: 10/25/2002
• Status: Active Grant

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Hufton, Jeffrey Raymond, Allam, Rodney John, Nataraj, Shankar, Xu, Jianguo, Ying, David Hon Sing, Dulley, Sarah Jane
• Granted Patent: US 7,354,562 B2
• Time in Patent Office: Days
• US Class Current: 423/656
• CPC Class Codes: B01D 2251/30 Alkali metal compounds
• CPC Class Codes: B01D 2251/40 Alkaline earth metal or magnesium compounds
• CPC Class Codes: B01D 2251/60 Inorganic bases or salts
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2256/22 Carbon dioxide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2258/0208 from fuel cells
• CPC Class Codes: B01D 2259/40001 Methods relating to additional, e.g. intermediate, treatment of process gas
• CPC Class Codes: B01D 2259/402 using two beds
• CPC Class Codes: B01D 2259/4143 arranged as a mixture
• CPC Class Codes: B01D 2259/4146 Contiguous multilayered adsorbents
• CPC Class Codes: B01D 53/04 with stationary adsorbents B01D53/025 takes precedence
• CPC Class Codes: B01D 53/0462 Temperature swing adsorption
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/864 Removing carbon monoxide or hydrocarbons
• CPC Class Codes: C01B 2203/0205 containing a reforming step
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/0425 In-situ adsorption process during hydrogen production
• CPC Class Codes: C01B 2203/043 Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
• CPC Class Codes: C01B 2203/0445 Selective methanation
• CPC Class Codes: C01B 2203/047 : the impurity being carbon monoxide
• CPC Class Codes: C01B 2203/0475 : the impurity being carbon dioxide
• CPC Class Codes: C01B 2203/1011 : Packed bed of catalytic structures, e.g. particles, packing elements
• CPC Class Codes: C01B 2203/1041 : Composition of the catalyst
• CPC Class Codes: C01B 2203/1047 : Group VIII metal catalysts
• CPC Class Codes: C01B 2203/1064 : Platinum group metal catalysts
• CPC Class Codes: C01B 2203/1076 : Copper or zinc-based catalysts
• CPC Class Codes: C01B 3/16 : using catalysts
• CPC Class Codes: C01B 3/56 : by contacting with solids; Regeneration of used solids C01B3/508 takes precedence
• CPC Class Codes: Y02C 20/40 : of CO2
• CPC Class Codes: Y02P 20/151 : Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

A process for producing a high temperature CO_x-lean product gas from a high temperature CO_x-containing feed gas, includes: providing a sorption enhanced reactor containing a first adsorbent, a shift catalyst and a second adsorbent; feeding into the reactor a feed gas containing H₂, H₂O, CO and CO₂; contacting the feed gas with the first adsorbent to provide a CO₂ depleted feed gas; contacting the CO₂ depleted feed gas with the shift catalyst to form a product mixture comprising CO₂ and H₂; and contacting the product mixture with a mixture of second adsorbent and shift catalyst to produce the product gas, which contains at least 50 vol. % H₂, and less than 5 combined vol. % of CO₂ and CO. The adsorbent is a high temperature adsorbent for a Sorption Enhanced Reaction process, such as K₂CO₃ promoted hydrotalcites, modified double-layered hydroxides, spinels, modified spinels, and magnesium oxides.

Claims

1. A process for producing a high temperature CO_x-lean product gas from a high temperature CO_x-containing feed gas, said process comprising:

providing a sorption enhanced reactor containing a first adsorbent, a shift catalyst and a second adsorbent;

feeding the feed gas into the reactor during a reaction step, wherein the feed gas comprises H₂, H₂O, CO and CO₂;

contacting the feed gas with the first adsorbent to adsorb an amount of CO₂ from the feed gas and provide a CO₂ depleted feed gas;

contacting the CO₂ depleted feed gas with the shift catalyst to catalyze a shift reaction of CO and H₂O to form a product mixture comprising CO₂ and H₂;

contacting the product mixture with a mixture of the second adsorbent and the shift catalyst to produce the product gas, wherein the product gas comprises at least 50 vol. % H₂, and less than 5 combined vol. % of CO₂ and CO;

regenerating the first and second adsorbents; and

repressurizing the reactor with a pressurization gas.

2. The process of claim 1, wherein the reactor contains a first bed, an intermediate bed downstream of the first bed and a second bed downstream of the intermediate bed, and wherein the first bed contains the first adsorbent, the second bed contains the mixture of the second adsorbent and the shift catalyst, and the intermediate bed contains the shift catalyst.

3. The process of claim 2, wherein:

(a) the second bed is packed with solid particles;

(b) each of the solid particles comprises both the second adsorbent and the shift catalyst; and

(c) the mixture of the second adsorbent and the shift catalyst in the second bed is provided by packing the second bed with the solid particles without mixing.

4. The process of claim 1, wherein the first and second adsorbents are regenerated by decreasing a gas pressure of the reactor and purging the reactor with a purge gas free of CO₂.

5. The process of claim 1, wherein the pressurization gas comprises at least one of the purge gas and the feed gas.

6. The process of claim 1, wherein the first adsorbent is identical to the second adsorbent.

7. The process of claim 1, wherein the first adsorbent and the second adsorbent are at least one member selected from the group consisting of:

(a) K₂CO₃ promoted hydrotalcites;

(b) modified double layered hydroxides represented by Formula I;

(Mg_(1-X)Al_x(OH)₂)(CO₃)_x/2yH₂OzM¹₂CO₃  

 

(I)

where 0.09≦

x≦

0.40, 0≦

y≦

3.5, 0≦

z≦

3.5, and M¹ is Na or K;

(c) spinels and modified spinels represented by Formula II;

Mg(Al₂)O₄yK₂CO₃  

 

(II)

where 0≦

y≦

3.5; and

(d) magnesium oxide-containing adsorbents represented by Formula III;

{(M₂CO₃)_m(2MHCO₃)_(1-m)}_n(MgCO₃)_p(MgO)_(1-p)xH₂O  

 

(III)

where M is an alkali metal, 0≦

m≦

1, 0≦

n≦

1.3, 0≦

p<

1, and x represents an extent of hydration of the adsorbent, with the proviso that when n equals 0 the MgO is made by dehydration and CO₂ removal of {MgCO₃}_yMg(OH)₂}_(1-y)xH₂O, in which 0.1≦

y≦

0.9, and x indicates an extent of hydration.

8. The process of claim 1, wherein the first adsorbent and the second adsorbent are independently at least one member selected from the group consisting of:

(a) K₂CO₃ promoted hydrotalcites;

(b) modified double layered hydroxides represented by Formula I;

(Mg_(1-X)Al_x(OH)₂)(CO₃)_x/2yH₂OzM¹₂CO₃  

 

(I)

where 0.09≦

x≦

0.40, 0≦

y≦

3.5, 0≦

z≦

3.5, and M¹ is Na or K;

(c) spinels and modified spinels represented by Formula II;

Mg(Al₂)O₄yK₂CO₃  

 

(II)

where 0≦

y≦

3.5; and

(d) magnesium oxide-containing adsorbents represented by Formula III;

{(M₂CO₃)_m(2MHCO₃)_(1-m)}_n(MgCO₃)_p(MgO)_(1-p)xH₂O  

 

(III)

where M is an alkali metal, 0≦

m≦

1, 0≦

n≦

1.3, 0≦

p<

1, and x represents an extent of hydration of the adsorbent, with the proviso that when n equals 0 the MgO is made by dehydration and CO₂ removal of {MgCO₃}_y{Mg(OH)₂}_(1-y)xH₂O, in which 0.1≦

y≦

0.9, and x indicates an extent of hydration.

9. The process of claim 1, wherein the shift catalyst is at least one member selected from the group consisting of CuO/ZnO based shift catalysts, Fe₂O₃/Cr₂O₃ based shift catalysts and shift catalysts containing noble metals.

10. The process of claim 1, wherein the feed gas comprises 25-75 vol. % H₂, 10-50 vol. % H₂O, 1-20 vol. % CO, 1-20 vol. % CO₂, 0-50 vol. % N₂, and 0.1-5 vol. % CH₄

11. The process of claim 1, wherein the feed gas is a syngas effluent from a steam methane reformer, partial oxidation reactor, air-blown autothermal reformer or oxygen-blown autothermal reformer upstream of the reactor.

12. The process of claim 1, wherein the feed gas is a syngas effluent from a high temperature shift reactor, and raw syngas to the high temperature shift reactor is obtained from a steam methane reformer, partial oxidation reactor, air-blown autothermal reformer or oxygen-blown autothermal reformer upstream of the reactor.

13. The process of claim 1, wherein the feed gas is fed into the reactor at a flow rate of 5-50 gmole/hr/cm² and a reactor temperature during the process is maintained between 175°

C. and 550°

C.

14. The process of claim 1, further comprising conveying the product gas to a methanator to reduce the CO concentration in the product gas to less than 50 ppm.

15. The process of claim 1, wherein the purge gas comprises at least one of steam and a steam/H₂ mixture.

16. The process of claim 1, wherein the process is conducted in a series of cycles in more than one said reactor, and one said reactor is being regenerated while another said reactor is being operated in parallel to produce the product gas.

17. The process of claim 1, further comprising conveying the product gas to a pressure swing adsorption unit to increase a hydrogen concentration of the product gas to at least 99 vol. %, wherein purge gas from the pressure swing adsorption unit is used to purge the reactor.

18. The process of claim 1, further comprising countercurrently purging the reactor at feed gas pressure with purge gas before regenerating the first and second adsorbents to yield an effluent stream containing unreacted CO and H₂O, and recycling the effluent stream to the feed gas stream to produce a CO₂ and CO depleted product stream with enhanced hydrogen recovery.

19. The process of claim 1, further comprising cocurrently rinsing the reactor at feed gas pressure with CO₂ product before regenerating the first and second adsorbents to produce a CO₂ and CO depleted product stream with enhanced hydrogen recovery and recover a CO₂-rich byproduct stream during the regenerating.

20. The process of claim 19, where the CO₂ and CO depleted product stream is used to generate power in a gas fired turbine system.

21. An apparatus for performing the process of claim 1, said apparatus comprising:

a first bed comprising the first adsorbent;

a second bed comprising the mixture of the second adsorbent and the shift catalyst;

an intermediate bed between, and in fluid communication with, the first bed and the second bed, wherein the intermediate bed comprises the shift reaction catalyst;

a feed gas inlet at a feed end of the first bed;

a product gas outlet at a product end of the second bed,

wherein the first adsorbent and the second adsorbent are at least one member independently selected from the group consisting of;

(a) K₂CO₃ promoted hydrotalcites;

(b) modified double layered hydroxides represented by Formula I;

(Mg_(1-X)Al_x(OH)₂)(CO₃)_x/2yH₂OzM¹₂CO₃  

 

(I)

where 0.09≦

x≦

0.40, 0≦

y≦

3.5, 0≦

z≦

3.5, and M¹ is Na or K;

(c) spinels and modified spinels represented by Formula II;

Mg(Al₂)O₄yK₂CO₃  

 

(II)

where 0≦

y≦

3.5; and

(d) magnesium oxide-containing adsorbents represented by Formula III;

{(M₂CO₃)_m(2MHCO₃)_(1-m)}_n(MgCO₃)_p(MgO)_(1-p)xH₂O  

 

(III)

where M is an alkali metal, 0≦

m≦

1, 0≦

n≦

1.3, 0≦

p<

1, and x represents an extent of hydration of the adsorbent, with the proviso that when n equals 0 the MgO is made by dehydration and CO₂ removal of {MgCO₃}_y{Mg(OH)₂}_(1-y)xH₂O, in which 0.1≦

y≦

0.9, and x indicates an extent of hydration.

22. The apparatus of claim 21, wherein a volume fraction of the mixture in the second bed varies as a function of location in the second bed such that a shift catalyst concentration gradient is provided.

23. The apparatus of claim 21, wherein the first adsorbent is identical to the second adsorbent.

24. The apparatus of claim 21, wherein:

(a) the second bed is packed with solid particles;

(b) each of the solid particles comprises both the second adsorbent and the shift catalyst; and

(c) the mixture of the second adsorbent and the shift catalyst in the second bed is provided by packing the second bed with the solid particles without mixing.

25. The apparatus of claim 21, wherein the shift catalyst is at least one member selected from the group consisting of CuO/ZnO based shift catalysts, Fe₂O₃/Cr₂O₃ based shift catalysts, and shift catalysts containing noble metals.

26. The apparatus of claim 21, further comprising an adiabatic vessel in which the first bed, the intermediate bed and the second bed are packed as consecutive layers.

27. The apparatus of claim 26, wherein there is more than one said adiabatic vessel adapted to operate in parallel with each other.

28. The apparatus of claim 26, further comprising a steam methane reformer, partial oxidation reactor or autothermal reformer in fluid communication with the feed gas inlet.

29. The apparatus of claim 26, further comprising a high temperature shift reactor in fluid communication with the feed gas inlet and the steam methane reformer, partial oxidation reactor or autothermal reformer.

30. The apparatus of claim 29, further comprising a methanator in fluid communication with the product gas outlet to reduce a CO concentration in the product gas to less than 50 ppm.

31. The apparatus of claim 30, further comprising a hydrogen fuel cell in fluid communication with the methanator.

32. The apparatus of claim 30, further comprising a pressure swing adsorption unit adapted to increase a hydrogen concentration of the product gas to at least 99 vol. %, and to provide purge gas to the reactor.

33. A process for producing a high temperature CO_x-lean product gas from a high temperature CO_x-containing feed gas, said process comprising:

providing a sorption enhanced reactor containing a mixture of an adsorbent and a shift catalyst in a single bed;

feeding the feed gas into the reactor during a reaction step, wherein the feed gas comprises H₂, H₂O, CO and CO₂;

contacting the feed gas with the mixture of the adsorbent and the shift catalyst to produce the product gas, wherein the product gas comprises at least 50 vol. % H₂, and less than 5 combined vol. % of CO₂ and CO;

regenerating the adsorbent; and

repressurizing the reactor with a pressurization gas.

34. The process of claim 33, wherein:

(a) the single bed is packed with solid particles;

(b) each of the solid particles comprises both the adsorbent and the shift catalyst; and

(c) the mixture of the adsorbent and the shift catalyst in the single bed is provided by packing the single bed with the solid particles without mixing.

35. An apparatus for performing the process of claim 33, said apparatus comprising:

a single bed comprising a mixture of the adsorbent and the shift catalyst;

a feed gas inlet at a feed end of the bed;

a product gas outlet at a product end of the bed,

wherein the adsorbent is at least one member independently selected from the group consisting of;

(a) K₂CO₃ promoted hydrotalcites;

(b) modified double layered hydroxides represented by Formula I;

(Mg_(1-X)Al_x(OH)₂)(CO₃)_x/2yH₂OzM¹₂CO₃  

 

(I)

where 0.09≦

x≦

0.40, 0≦

y≦

3.5, 0≦

z≦

3.5, and M¹ is Na or K;

(c) spinels and modified spinels represented by Formula II;

Mg(Al₂)O₄yK₂CO₃  

 

(II)

where 0≦

y≦

3.5; and

(d) magnesium oxide-containing adsorbents represented by Formula III;

{(M₂CO₃)_m(2MHCO₃)_(1-m)}_n(MgCO₃)_p(MgO)_(1-p)xH₂O  

 

(III)

where M is an alkali metal, 0≦

m≦

1, 0≦

n≦

1.3, 0≦

p<

1, and x represents an extent of hydration of the adsorbent, with the proviso that when n equals 0 the MgO is made by dehydration and CO₂ removal of {MgCO₃}_y{Mg(OH)₂}_(1-y)xH₂O, in which 0.1≦

y≦

0.9, and x indicates an extent of hydration.

36. The apparatus of claim 35, wherein:

(a) the single bed is packed with solid particles;

(b) each of the solid particles comprises both the adsorbent and the shift catalyst; and

(c) the mixture of the adsorbent and the shift catalyst in the single bed is provided by packing the single bed with the solid particles without mixing.