Catalytic Reforming of Higher Hydrocarbon Fuels to Hydrogen: Process Investigations with Regard to Auxiliary Power Units

This thesis discusses the investigation of the catalytic partial oxidation on rhodium-coated honeycomb catalysts with respect to the conversion of a model surrogate fuel and commercial diesel fuel into hydrogen for the use in auxiliary power units. Furthermore, the influence of simulated tail-gas recycling was investigated

Catalytic Partial Oxidation of Isooctane to Hydrogen on Rhodium Catalysts: Effect of Tail-Gas Recycling

Catalytic partial oxidation (CPOX) is a promising technology for reforming of liquid hydrocarbon fuels to hydrogen or synthesis gas for use in fuel cells. The addition of a certain amount of the tail gas of the fuel cell stack to the reformer inlet feed can increase overall efficiency and lead to higher H₂ and CO selectivities and reduce coke formation. The effect of carbon dioxide or steam addition (1, 5, 10, 20, and 30 vol% of the total flow) on the performance of a CPOX reformer operated with isooctane as fuel surrogate is systematically studied over a wide range of C/O feed ratios (0.72–1.79) using a Rh/alumina honeycomb catalyst. The specific impact of the coreactants H₂O and CO₂ on reformer behavior can be interpreted by the water gas shift (WGS) chemistry. Production of H₂ and CO₂ increases with H₂O addition at the expense of CO and H₂O. Opposite trends are observed in case of CO₂ addition. Tail gas recycling reduces formation of soot precursors up to 50% compared to the corresponding fuel feed without coreactants. However, tail-gas recycling shifts the formation of soot precursors toward lower C/O ratios