Hydrogen Ambassadors International Competition

Online Vote has completed:
All Hydrogen Ambassador Teams have won!

Meet Our Winners! Congratulations to the winning teams of the 2006 Hydrogen Ambassadors Competition fully sponsored by Arno A. Evers and the FAIR-PR Team!

Team USA II:
Production of hydrogen and electricity in methane SOFC

Booth Number:
H81/5

Scott Barnett (51) Manoj Pillai (34) Ilwon Kim (37) Northwestern University, Department of Materials Science and Engineering Functional Coating Technology, LLC, Evanston, IL, USA

Scott Barnett	Manoj Pillai	Ilwon Kim

Methane reforming is typically used to produce syngas (H2+CO), an important feedstock for the production of various chemicals including methanol and liquid hydrocarbons. Syngas can also be converted to H2, another important industrial feedstock and a potential fuel. This paper describes a method, electrochemical partial oxidation, where syngas and electricity are co-produced in a solid oxide fuel cell (SOFC) that operates with methane as the fuel. Due to the high value of the electricity produced, this approach has the potential to produce hydrogen/syngas more cost effectively than other methods.

In methane electrochemical partial oxidation (EPOx), a SOFC is operated with the natural gas (i.e. methane) flow rate and total stack current adjusted such that there are ? 1 oxygen ions (O2-) pumped across the cell per methane molecule, the stoichiometry of partial oxidation:
CH4 + O2- = CO + 2H2 + 2e-. (1)
Under appropriate conditions, the SOFC produces both syngas (H2+CO) and electricity. This is quite different from conventional fuel cells, where the fuel is almost fully oxidized. For the case of a direct-methane SOFC, for example, the methane feed rate would be 3-4 times lower, such that the reaction is closer to complete oxidation:
(1/4)CH4 + O2- = (1/4)CO2 + (1/2)H2O + 2e-. (2)
Comparison of reactions 1 and 2 shows that for a given sized SOFC, the same amount of electricity (2e-) is produced, but the products are different.

EPOx provides two key advantages. First, the SOFC provides pure oxygen such that there is no dilution of the syngas by nitrogen, different than partial oxidation with air. Second, the co-production of electricity and syngas improves the economics of both syngas production and fuel cell electricity production. In particular, when SOFC costs drop below ?$400 per kilowatt, they are expected to become commercially viable. For an EPOx SOFC, this means that there is no additional cost for the production of syngas/hydrogen, other than the cost of the additional feedstock natural gas. Thus, EPOx can produce syngas/hydrogen at a lower cost than any other technology. This is critical for alternative fuels such as hydrogen and gas-to-liquids fuels (where natural gas is converted via syngas to clean synthetic liquid fuels) to reach a competitive cost level.

The implementation of EPOx has been limited because direct methane operation often leads to fouling of the anodes with deposited carbon. Thus, non-standard SOFC materials, e.g. Pt for the anode, have been used in order to avoid coking, but are too expensive for practical devices. To date, SOFC power densities and syngas production rates were relatively low, and coking was often observed. In this paper, we demonstrate stable methane EPOx operation of SOFCs without coking, yielding both high electrical power densities and high syngas production rates. We also present results of thermodynamic calculations that provide estimates of expected EPOx operating conditions and productivity. Taken together, these results demonstrate the feasibility of EPOx SOFCs.