Link-up of a bench-scale “shift-less” gasoline fuel processor to a polymer electrolyte fuel cell

The rapid development of the polymer electrolyte fuel cell (PEFC) technology in recent years has stimulated research in all areas of fuel processing catalysis for hydrogen generation. A new precious metal catalyst with an improved precious metal utilisation, which allows the low temperature reforming (550–650 °C) of hydrocarbons, was developed. The low temperature reforming results in low carbon monoxide concentrations, in the range of 2–5 vol.%, making it possible to omit the shift units before the preferential oxidation unit (PROX). For the PROX unit a selective catalyst was developed to oxidize the carbon monoxide down to a level acceptable for PEFCs. To demonstrate the “shift-less” fuel processing concept, a test unit was built containing a gasoline reformer and a PROX unit. At GHSV of 3319–19795 h−1 and T = 595–645 °C complete conversion of C2+ was achieved. First, a dual fixed-bed reactor configuration with staged air supply was tested for the PROX. With this configuration hot spots over 280 °C occurred, which made a selective conversion of carbon monoxide impossible. The hot-spot problem was drastically reduced by using an annulus reactor achieving >99.93% carbon monoxide conversion due to the better heat dissipation. The hydrogen conversion in the PROX unit was high at around 27%. This value may be improved by better temperature control of the PROX reactor. Reformate gas with hydrogen concentrations up to 51 vol.% could be produced from sulphur-free gasoline (RON = 95). Reformate gas with 32% H2 and <36 ppmv CO was fed to a 30 cm2 polymer electrolyte fuel cell. A stable cell voltage of 680 mV was obtained at a current density of 500 mA cm−2 for operation with pure O2 as oxidant. Changing the oxidant to air led to a cell voltage decline of 120 mV.