Selective methanation reactor for reducing carbon monoxide in a reformate stream
View Patent ↗A method of operating a methanation reactor to reduce carbon monoxide concentration in a reformate stream in a fuel cell reformer. The reactor includes a flowpath with a noble metal catalyst supported by a ceramic support such that the reactor preferentially converts carbon monoxide via methanation over that of carbon dioxide. The reduced level of carbon monoxide present in the reformate stream after passing through the methanation reactor reduces the likelihood of poisoning of the catalyst used on the fuel cell anode.
1. A method of delivering fuel to a fuel cell system, said method comprising:
providing a fuel processing system comprising:
a reformer to evaporate a mixture of fuel and oxygen coming from said fuel delivery system; and
a single stage methanation reactor for removal of carbon monoxide from a reformate stream produced by said reformer, said reactor comprising:
a porous ceramic support comprising alumina having silica dispersed on a surface of the alumina, said porous ceramic support having a surface acidity greater than that of alumina alone; and
a noble metal catalyst coupled to said support, said noble metal selected from rhodium and ruthenium;
introducing fuel and oxygen to said fuel processing system to create a fuel-oxygen mixture;
heating said fuel-oxygen mixture in said reformer to produce said reformate stream containing CO, CO 2 , H 2 O, and H 2 ;
introducing said reformate stream into said reactor;
methanating said CO in said reactor at a temperature in a range of about 280° C. to about 340° C., said methanation having a selectivity of over 50% at a temperature of up to 340° C., and a CO conversion rate of about 30% at a temperature in a range of about 275° C. to about 300° C. to form a stream having a reduced CO level; and
transporting said stream having said reduced CO level to said fuel cell.
2. A method according to claim 1 , wherein said noble metal is rhodium.
3. The method of claim 1 , wherein the temperature below which carbon monoxide conversion is less than about 1200 ppm is about 275 degrees Celsius.
4. The method of claim 3 , whereupon attainment of about 1200 ppm carbon monoxide conversion, the portion of said reformate stream being delivered to the fuel cell comprises a carbon monoxide content of less than 10 ppm.
5. The method of claim 1 , wherein said support temperature configured to be operated at least 250 degrees Celsius is operated at a temperature of between 270 degrees Celsius and 340 degrees Celsius.
6. The method of claim 1 , wherein said hydrogen is present in said reformate stream prior to said reaction.
7. The method of claim 1 , wherein said receiving said reformate stream into said flowpath comprises receiving said reformate stream from a reformer.
8. The method of claim 7 , wherein said reformer comprises a steam reformer.
9. The method of claim 7 , wherein said reformer comprises a partial oxidation reformer.
10. The method of claim 7 , wherein said reformer comprises an autothermal reformer.
11. The method of claim 7 , wherein said receiving said reformate stream into said flowpath comprises receiving said reformate stream from a water gas shift reactor.
12. The method of claim 7 , wherein said receiving said reformate stream into said flowpath comprises receiving said reformate stream from a reformer and a water gas shift reactor.
13. The method of claim 7 , further comprising sending said reformate stream to a fuel cell.