The preparation of a metal foam support of Pt/Al 2O 3 for combustion of hydrogen

Abstract

A catalyst bed is an essential component of a passive autocatalytic recombiner (PAR) used to remove hydrogen that is accidentally released during a meltdown of a nuclear reactor power plant. Metal foam was selected as a catalytic support in this study, due to its excellent thermal conductivity and its high surface-to-volume ratio. The support surface area was additionally increased by the application of an Al 2O 3 washcoat. An investigation of optimum coating conditions of the Pt/Al 2O 3-coated metal foam was performed with respect to the hydrogen conversion rate and the thermal behavior, with the goal of achieving high hydrogen removal rates. The experimental results showed that the hydrogen conversion rates were affected by washcoat weights and platinum weights, and the majority of the experimental conditions of the Pt/Al 2O 3-coated metal foam showed hydrogen conversion rates over 95%. For cost-effective fabrication, the optimum conditions are an Al 2O 3 washcoat weight of 45 wt.%, and a platinum weight of 3 wt.%. These will lead to a complete removal of the hydrogen at a hydrogen concentration of 4 vol.%. Furthermore, since a region of high hydrogen concentrations has a temperature lower than about 560 °C, which is the ignition limit at a hydrogen concentration of 4 vol.% and ambient pressure, the hydrogen risk can be avoided using the metal foam support.