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1. (WO2018226635) OXYDES MIXTES FAVORISÉS POUR OXYDATION PARTIELLE DE MÉTHANE "BASSE TEMPÉRATURE" EN L'ABSENCE D'OXYDANTS GAZEUX
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

We claim:

1. A redox catalyst comprising a perovskite, double perovskite, or layered perovskite (Ruddlesden-Popper, Aurivillius, and Dion-Jacobson phases) having a formula selected from the group consisting of (A/AVi(B/B')n03n+i-a,


(S /A) (F /M /B) 0 and a combination thereof

wherein each occurrence of A is independently an alkali-earth, rare-earth, or alkali metal or a combination thereof,

wherein each occurrence of B is independently selected from the group consisting of Fe, or a combination thereof,


wherein each occurrence of x is independently about 0.0 to 1 ,

wherein each occurrence of y is independently about 0.0 to 1 , and

wherein each occurrence of z is independently about 0.0 to 1 , and

wherein each occurrence of a is independently about 0.0 to 2, and

wherein the perovskite has an outer surface comprising about 5 wt. % or less of a platinum-group metal based upon a total weight of the redox catalyst.

2. The redox catalyst according to claim 1 , wherein each occurrence of A is independently selected from the group consisting of Sr, Ba, Ca, La, Pr, Sm, Dy, and a combination thereof.

3. The redox catalyst according to claim 1 or claim 2, wherein the platinum-group metal is Rhodium, Platinum, Osmium, Iridium, Ruthenium, Palladium, and mixture thereof.

4. The redox catalyst according to claim 1 or claim 2, wherein the platinum-group metal is present in an amount from about 0.005 wt. % to about 2.0 wt. % by weight based upon the total weight of the redox catalyst.

5. A method of converting methane to syngas, the method comprising contacting the methane with a redox catalyst according to any one of claims 1-4 to produce the syngas.

6. The method according to claim 5, wherein the methane is contacted with the redox catalyst at a temperature of about 400°C to about 950°C.

7. The method according to claim 5 or claim 6, wherein the redox catalyst is in a circulating fluidized bed or moving bed reactor.

8. The method according to claim 5 or claim 6, further comprising regenerating the redox catalyst by contacting the redox catalyst with air or an oxygen containing gas to regenerate the redox catalyst.

9. The method according to claim 5 or claim 6, further comprising regenerating the redox catalyst by contacting the redox catalyst with water and carbon dioxide in the presence of an external energy source.

10. The method according to claim 9, wherein the external energy source is solar thermal radiation or industrial waste heat or combination thereof.

11. The method according to claim 10, wherein the regeneration step produces H2, CO, or a mixture thereof.

12. The method according to claim 5 or claim 6, wherein the redox catalyst is in a fixed bed reactor.

13. The method according to claim 12, wherein the redox catalyst is in multiple coupled fixed-bed reactors, and the method further comprises alternating feed streams between

(1) a first feed stream comprising the methane, and

(2) a second feed stream comprising air, carbon dioxide, water, or a mixture thereof.

14. The method according to claim 13, wherein contacting the redox catalyst with the second feed stream regenerates the redox catalyst.

15. The method according to claim 14, wherein contacting the redox catalyst with the second feed stream produces H2, CO, or a mixture thereof.

16. The method according to claim 5 or claim 6, wherein redox catalyst is mixed with a phase change material (PCM) to maintain stable operating temperatures throughout the reactors.

17. The method according to claim 16, wherein the PCM material is an alloy containing aluminum encapsulated in an alumina containing shell.

18. The method according to claim 14, wherein the redox catalyst is in sequential or mixed bed of redox catalyst with a heterogamous methane reforming catalyst.

19. The method according to claim 18, wherein the reforming catalyst is a nickel or platinum group metal supported on a refractory support material such as alumina, silica, or spinel.

20. The method according to claim 12, wherein the fixed bed reactor comprises a reverse flow reactor having a first end and a second end;

wherein the redox catalyst nearest the first end is initially at a first high average oxidation state for the cation(s) and the redox catalyst nearest the second end is initially at a second low average oxidation state lower than the first high average oxidation state, and

wherein the method comprises:

(1 ) introducing methane into the reactor near the first end for a first period of time;

wherein the methane contacts the redox catalyst in the first high average oxidation state near the first end of the reactor to produce a first amount of C02 and a first amount of H20;

wherein at least some of the first amount of C02 contacts the redox catalyst in the second low average oxidation state near the second end of the reactor to produce a first amount of CO;

wherein at least some of the first amount of H20 contacts the redox catalyst in the second low average oxidation state near the second end of the reactor to produce H2; and

wherein after the first period of time the redox catalyst nearest the first end is in a third low average oxidation state;

(2) introducing a first amount of oxidizing gas into the reactor near the second end for a second period of time; wherein the first amount of oxidizing gas contacts the redox catalyst near the second end of the reactor to oxidize the redox catalyst near the second end of the reactor; and

wherein after the second period of time the redox catalyst near the second end is in a fourth high average oxidation state higher than the third low average oxidation state;

(3) introducing methane into the reactor near the second end for a third period of time; wherein the methane contacts the redox catalyst in the fourth high average oxidation state near the second end of the reactor to produce a second amount of C02 and a second amount of H20;

wherein at least some of the second amount of C02 contacts the redox catalyst in the third low average oxidation state near the first end of the reactor to produce a second mount of CO;

wherein at least some of the second amount of H20 contacts the redox catalyst in the third low average oxidation state near the first end of the reactor to produce a second amount of H2; and

wherein after the third period of time the redox catalyst nearest the second end is in a fifth low average oxidation state; and

(4) introducing a second amount of oxidizing gas into the reactor near the first end for a fourth period of time; wherein the second amount of oxidizing gas contacts the redox catalyst near the first end of the reactor to oxidize the redox catalyst near the first end of the reactor; and wherein after the fourth period of time the redox catalyst near the first end is in a sixth high average oxidation state higher than the fifth low average oxidation state.

21. The method according to claim 20, wherein the first high average oxidation state, the fourth high average oxidation state, and the sixth high average oxidation state are substantially the same average oxidation state.

22. The method according to claim 20, wherein the second low average oxidation state, the third low average oxidation state, and the fifth low average oxidation state are substantially the same average oxidation state.

23. A method according to claim 20, wherein the redox catalyst is integrated with

heterogeneous reforming catalyst particles in either mixed form or layered form.

24. A method according to claim 20, where the redox catalyst comprises a mixture of a first redox catalyst having a first chemical formula and a second redox catalyst having a second chemical formula different from the first chemical formula; and

wherein the first redox catalyst and the second redox catalyst comprise a redox catalyst according to claim 1.

25. The method according to claim 20, further comprising purging the reactor between steps (1) and (2), between steps (2) and (3), between steps (3) and (4), or any combination thereof; wherein the purging comprises introducing an inert gas, a steam, or a combination thereof into the reactor.

26. The method according to any one of claims 20-25 wherein steps (1)-(4) are repeated to convert additional methane.