Passive autocatalytic recombination of hydrogen on a Pt/Al2O3-coated metal foam: Experimental evaluation and CFD modelling

Pt/Al2O3-coated Al foams were tested for the passive autocatalytic recombination of H-2. The characterisation of the washcoat surface confirmed the uniform distribution of Pt and Al2O3 over the entire washcoat surface. Transmission electron microscopy results revealed a slight increase in particle size from 3.8 to 6.2 nm after prolonged reaction. High H-2 conversions of 57-89% are achieved and the catalyst activity is maintained for >480 h on stream. The performance of the foam-based catalyst bed is similar to that of plates but surpasses that of catalyst pellets. Temperatures recorded at the hottest spots on the foam surface reach a maximum of only 393 degrees C at the highest H-2 inflow. Computational fluid dynamics simulations were performed on the actual foam geometry obtained using computed tomography. The simulations demonstrate the importance of thermal radiation in the model. There is good agreement between results of experimental H-2 conversions and maximum combustion temperatures.