Regenerable sorbent for carbon dioxide removal

• US 9,808,783 B2
• Filed: 07/19/2013
• Issued: 11/07/2017
• Est. Priority Date: 07/19/2012
• Status: Active Grant

• Current Assignee: Research Triangle Institute
• Original Assignee: Research Triangle Institute
• Inventors: Shen, Jian-Ping, Coleman, Luke James Ivor, Lail, Marty Alan, Gupta, Raghubir Prasad, Turk, Brian Scott
• Primary Examiner(s): BERNS, DANIEL J
• Application Number:
  US14/415,283
• Publication Number:
  US 20150190777A1
• Time in Patent Office: 1,572 Days
• Field of Search: None
• CPC Class Codes: B01D 2251/304 of sodium
• CPC Class Codes: B01D 2251/402 of magnesium
• CPC Class Codes: B01D 2251/602 Oxides
• CPC Class Codes: B01D 2251/606 Carbonates
• CPC Class Codes: B01D 2253/1124 Metal oxides
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2258/01 Engine exhaust gases
• CPC Class Codes: B01D 2258/0241 from glass manufacture plants
• CPC Class Codes: B01D 2258/025 from metallurgy plants
• CPC Class Codes: B01D 2258/0283 Flue gases
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01D 53/0462 Temperature swing adsorption
• CPC Class Codes: B01D 53/0476 Vacuum pressure swing adsorption
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01D 53/82 with stationary reactants
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants
• CPC Class Codes: B01J 20/04 comprising compounds of alkali metals, alkaline earth metals or magnesium
• CPC Class Codes: B01J 20/041 Oxides or hydroxides
• CPC Class Codes: B01J 20/043 Carbonates or bicarbonates, e.g. limestone, dolomite, aragonite
• CPC Class Codes: B01J 20/28011 Other properties, e.g. density, crush strength
• CPC Class Codes: B01J 20/3078 : Thermal treatment, e.g. calcining or pyrolizing
• CPC Class Codes: B01J 20/3085 : Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
• CPC Class Codes: B01J 20/3433 : of sorbents or filter aids other than those covered by B01J20/3408 - B01J20/3425
• CPC Class Codes: B01J 20/3483 : by thermal treatment not covered by groups B01J20/3441 - B01J20/3475, e.g. by heating or cooling
• CPC Class Codes: B01J 20/3491 : by pressure treatment
• CPC Class Codes: B01J 2220/42 : Materials comprising a mixture of inorganic materials materials coated or impregnated on a carrier B01J20/32
• CPC Class Codes: C10K 1/005 : Carbon dioxide
• CPC Class Codes: C10K 1/26 : Regeneration of the purifying material contains also apparatus for the regeneration of the purifying material
• CPC Class Codes: Y02C 20/20 : of methane
• 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 mixed salt composition adapted for use as a sorbent for carbon dioxide removal from a gaseous stream is provided, the composition being in solid form and including magnesium oxide, an alkali metal carbonate, and an alkali metal nitrate, wherein the composition has a molar excess of magnesium characterized by a Mg:X atomic ratio of at least about 3:1, wherein X is the alkali metal. A process for preparing the mixed salt is also provided, the process including mixing a magnesium salt with a solution comprising alkali metal ions, carbonate ions, and nitrate ions to form a slurry or colloid including a solid mixed salt including magnesium carbonate; separating the solid mixed salt from the slurry or colloid to form a wet cake; drying the wet cake to form a dry cake including the solid mixed salt; and calcining the dry cake to form a mixed salt sorbent.

Claims

1. A mixed salt composition adapted for use as a sorbent for carbon dioxide removal from a gaseous stream, the composition being in solid form and comprising:

i) magnesium oxide;

ii) an alkali metal carbonate; and

iii) an alkali metal nitrate, wherein the composition has a molar excess of magnesium characterized by a Mg;

X atomic ratio of at least about 1.1;

1, wherein X is the alkali metal.

2. The mixed salt composition of claim 1, wherein the alkali metal comprises sodium.

3. The mixed salt composition of claim 1, wherein the Mg:

X atomic ratio is at least about 4;

1.

4. The mixed salt composition of claim 1, wherein the Mg:

X atomic ratio is at least about 6;

1.

5. The mixed salt composition of claim 1, wherein the alkali metal nitrate is present in an amount of at least about 1% by weight, based on total dry weight of the mixed salt composition.

6. The mixed salt composition of claim 1, comprising the mixture MgO:

Na₂CO₃;

NaNO₃, wherein the atomic ratio of Mg;

Na is at least about 1.1;

1.

7. The mixed salt composition of claim 1, having a crush strength in pellet form, as determined by the Shell method, of at least about 0.3 MPa.

8. A process for preparing a mixed salt composition, comprising:

i) mixing a magnesium salt with a solution comprising alkali metal ions, carbonate ions, and optionally nitrate ions, to form a slurry or colloid comprising a solid mixed salt comprising magnesium carbonate;

ii) separating the solid mixed salt from the slurry or colloid to form a wet cake of the solid mixed salt;

iii) drying the wet cake to form a dry cake comprising the solid mixed salt; and

iv) calcining the dry cake to form a mixed salt composition according to claim 1.

9. The process of claim 8, wherein the mixing step comprises mixing a first solution containing a dissolved alkali metal carbonate and optionally a dissolved alkali metal nitrate, and a second solution containing a dissolved magnesium salt to form the solid mixed salt as a co-precipitate.

10. The process of claim 9, wherein the water solubility of the magnesium salt is at least about 10 g per 100 ml at 25°

C. and one atmosphere.

11. The process of claim 9, wherein the magnesium salt is selected from magnesium nitrate, magnesium acetate, and magnesium chloride.

12. The process of claim 8, wherein the mixing step comprising combining a solid magnesium salt with a solution containing a dissolved alkali metal carbonate and a dissolved alkali metal nitrate to form the solid mixed salt as a colloid.

13. The process of claim 12, wherein the solid magnesium salt is basic magnesium carbonate.

14. The process of claim 8, wherein the carbonate ions in the solution are derived from a precipitating salt comprising a carbonate ion added to the solution.

15. The process of claim 14, wherein the precipitating salt is an alkali metal carbonate or ammonium carbonate.