Hydrocarbon fuels direct oxidation fuel cells

Direct Hydrocarbon Solid Oxide Fuel Cells... 

Steven McIntosh was born in Dundee, Scotland in 1977. He received his Batchelor of Engineering in Chemical Engineering from the University of Edinburgh in 1999. He is currently completing his Ph.D. degree at the University of Pennsylvania. The focus of his thesis is the development and characterization of direct-hydrocarbon solid oxide fuel cells. After a postdoctoral year, he will start as an Assistant Professor in Chemical Engineering at the University of Virginia in 2005. 

There are many chemically reacting flow situations in which a reactive stream flows interior to a channel or duct. Two such examples are illustrated in Figs. 1.4 and 1.6, which consider flow in a catalytic-combustion monolith [28,156,168,259,322] and in the channels of a solid-oxide fuel cell. Other examples include the catalytic converters in automobiles. Certainly there are many industrial chemical processes that involve reactive flow tubular reactors. Innovative new short-contact-time processes use flow in catalytic monoliths to convert raw hydrocarbons to higher-value chemical feedstocks [37,99,100,173,184,436, 447]. Certain types of chemical-vapor-deposition reactors use a channel to direct flow over a wafer where a thin film is grown or deposited [219]. Flow reactors used in the laboratory to study gas-phase chemical kinetics usually strive to achieve plug-flow conditions and to minimize wall-chemistry effects. Nevertheless, boundary-layer simulations can be used to verify the flow condition or to account for non-ideal behavior [147]. 

A single-chamber solid oxide fuel cell (SC-SOFC), which operates using a mixture of fuel and oxidant gases, provides several advantages over the conventional double-chamber SOFC, such as simplified cell structure with no sealing required and direct use of hydrocarbon fuel [1, 2], The oxygen activity at the electrodes of the SC-SOFC is not fixed and one electrode (anode) has a higher electrocatalytic activity for the oxidation of the fuel than the other (cathode). Oxidation reactions of a hydrocarbon fuel can... 

Park S etal., 2001, Tape Cast Solid Oxide Fuel Cells for the Direct Oxidation of Hydrocarbons. Journal of the Electrochemical Society, 148, A443. 

McIntosh, S. and Gorte, R.J. Direct hydrocarbon sohd oxide fuel cells. Chemical Reviews, 2004, 104 (10), 4845. 

Besides IT-SOFC, low-temperature (300-600°Q solid oxide fuel cells (LTSOFCs) have also demonstrated promising high performances for different fuels other than only hydrogen. For instance, liquid hydrocarbon fuels, e.g., methanol can be easily thermally decomposed to H2 and CO that can be directly used for fuel cell operation without an external reformer thus leading to a simple system and highly efficient operation [48]. 

An alternative to the use of H2 as fuel is methanol, which is a liquid fuel and easy to handle. This can be directly transformed to electrical current in a DMFC (direct methanol fuel cell). The DMFC allows a simple system design. However, presently achieved performance data of DMFC is not satisfactory and material costs are too high. As another alternative, methanol or hydrocarbons (e.g. natural gas, biogas) can be transformed to hydrogen on board the electric vehicle by a reformation reaction. This allows use of the H2-PEFC cell, which has a higher level of development. The reformate feed gas may contain up to 2.5% carbon monoxide (CO) by volume, which can be reduced to about 50ppm CO using a selective oxidizer (Wilkinson et al. [1997]). 

Solid Oxide Fuel Cells, Direct Hydrocarbon Type, Fig. 1 Coking rai-coking boundaries plotted on a C-H-O cranpositirai triangle, along with the positions of several relevant compounds (From Ref. [21])... 

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