On the catalytic performance of open cell structures versus honeycombs

Open-cell foams are increasingly gaining attention as catalytic substrates due to their promising properties of high porosity, high specific surface and tortuous structure resulting in enhanced gas wall interactions. However, due to the foam complex structure and variability of properties, the published data do not clarify weather true advantages of ceramic foam based catalytic converters can be expected; high gas wall interactions may result to increased flow resistance. In the present work, foams are modelled as Kelvin Cells and compared to honeycombs, the state of the art catalyst substrates, in the controlled environment of numerical simulations. A CFD analysis has been performed assuming a mass transfer limited regime and imposing infinitive fast chemistry at the catalytic surface. Our results show that open-cell structures compared to honeycombs have higher mass transfer properties at moderate to high flow rates (u > 2 m/s), allowing more compact reactors. Moreover they can achieve the same conversion with a significantly lower surface, saving an equivalent fraction of noble metal. In order to have the same conversion to pressure drop trade off, foam porosity has to be much higher compared to honeycombs. (C) 2014 Elsevier B.V. All rights reserved.