Liquid phase reforming of oxygenates for hydrogen production
In the liquid phase reforming (LPR) of oxygenated C,H-containing compounds such as alcohols, various strategies are disclosed for managing byproduct CO 2 . Important processing options include those in which electrolyte, consumed in capturing or precipitating the CO 2 generated from LPR, is regenerated or not regenerated, with carbon emissions potentially being avoided in the latter case. With regeneration, different chemistries are possible, such as in the case of a regeneration cycle utilizing hydroxide anions to precipitate a solid, carbonate form of CO 2 that is generated from reforming. Alternatively, a reaction and regeneration system may use carbonate anions to “capture” CO 2 and thereby maintain it as aqueous, solubilized bicarbonate form.
1. A process for reforming an oxygenated C,H-containing compound, the process comprising:
contacting the oxygenated C,H-containing compound with a catalyst in an aqueous solution, said aqueous solution comprising at least one CO 2 -precipitating cation,
wherein said oxygenated C,H-containing compound is reformed by reaction with H 2 O in said aqueous solution, to produce H 2 and a precipitated carbonate form of generated CO 2 and the CO 2 -precipitating cation,
the process further comprising adding, to a post-reforming reactor or post-reforming zone, positioned downstream of a respective reforming reactor or reforming zone in which at least about 90 wt-% of said oxygenated C,H-containing compound is reformed, a further amount of said at least one CO 2 -precipitating cation.
2. The process of claim 1 , wherein the oxygenated C,H-containing compound is an alcohol or an ether.
3. The process of claim 2 , wherein the oxygenated C,H-containing compound is selected from the group consisting of methanol, ethanol, and dimethyl ether.
4. The process of claim 1 , wherein the least one CO 2 -precipitating cation is selected from the group consisting of Ca +2 or Li + , Mg +2 , Sr +2 , Ba +2 , and mixtures thereof.
5. The process of claim 4 , wherein the least one CO 2 -precipitating cation is added to said post-reforming reactor or post-reforming zone as Ca(OH) 2 or LiOH.
6. The process of claim 1 , wherein a pH of the aqueous solution is at least about 12.
7. The process of claim 1 , wherein a concentration of the least one CO 2 -precipitating cation in the aqueous solution is at least about 3 normal (N).
8. The process of claim 1 , further comprising recovering the generated CO 2 by heating the precipitated carbonate form of CO 2 and obtaining an oxide form of the CO 2 -precipitating cation.
9. The process of claim 8 , wherein the oxide form of the CO 2 -precipitating cation is calcined CaO.
10. The process of claim 8 , further comprising hydrolyzing the oxide form of the CO 2 -precipitating cation to obtain a hydroxide form of the CO 2 -precipitating cation.
11. The process of claim 10 , further comprising adding the hydroxide form of the CO 2 -precipitating cation to the aqueous solution.
12. A process for reforming an oxygenated C,H-containing compound, the process comprising:
contacting, in a reforming reactor or reforming zone, the oxygenated C,H-containing compound with a catalyst in an aqueous solution, said aqueous solution comprising at least one CO 2 -precipitating cation and/or at least one CO 2 -capturing cation,
wherein said oxygenated C,H-containing compound is reformed by reaction with H 2 O in said aqueous solution, to produce H 2 and (i) a precipitated carbonate form of generated CO 2 and the CO 2 -precipitating cation and/or (ii) a captured bicarbonate form of generated CO 2 and the CO 2 -capturing cation,
the process further comprising:
modifying, in a post-reforming reactor or post-reforming zone, downstream of said reforming reactor or reforming zone, a condition of said aqueous solution to change solubility of (i) said precipitated carbonate form of generated CO 2 and/or (ii) said captured bicarbonate form of generated CO 2 .
13. The process of claim 12 , wherein said step of modifying comprises converting at least a portion of said captured bicarbonate form of generated CO 2 to said precipitated carbonate form of generated CO 2 .
14. The process of claim 12 , wherein a downstream concentration of the catalyst in said post-reforming reactor or post-reforming zone is less than an upstream concentration of catalyst in said reforming reactor or reforming zone.
15. The process of claim 14 , wherein the catalyst is substantially absent in said post-reforming reactor or post-reforming zone.
16. The process of claim 12 , wherein said step of modifying comprises adding, to the post-reforming reactor or post-reforming zone, a further amount of said at least one CO 2 -precipitating cation, a further amount of said at least one CO 2 -capturing cation, and/or a pH-adjusting anion.
17. The process of claim 12 , further comprising:
withdrawing, from the post-reforming reactor or post-reforming zone, a post-reforming effluent, and
feeding at least a portion of the post-reforming effluent to a solid-liquid separator to separate (i) at least a portion of the precipitated carbonate form of generated CO 2 , from (ii) at least a portion of the captured bicarbonate form of generated CO 2 .
18. The process of claim 17 , wherein said at least a portion of the captured bicarbonate form of generated CO 2 is obtained in an aqueous filtrate, the process further comprising:
recovering the generated CO 2 by contacting at least a portion of the aqueous filtrate with steam in a carbonate regenerator and obtaining a carbonate form of the CO 2 -capturing cation.