A comparative study Of V2O5/AC and V2O5/Al2O3 catalysts for the selective catalytic reduction of NO by NH3

The influence of two different washcoats deposited on ceramic honeycombs (alumina and carbon) on the catalytic and mechanical properties of catalysts are examined in this work. A series of carbon and alumina washcoated samples was prepared through a dip-coating method and subsequently cured and treated to reach a suitable chemistry surface. Carbon-coated monoliths present a high washcoat homogeneity, high integrity and a suitable chemistry surface that favour NO reduction at low temperatures. The carbon washcoat was bonded perfectly to the ceramic monoliths. The high adherence between both materials, checked by vibrational tests, provides higher resistance indexes against axial compression and prevents crack propagation. Both facts are a consequence of the high mechanical strength of the catalyst. On the other hand, alumina coatings present better temperature resistance, although their adherence to ceramic monoliths is not as good as in carbon-coated samples. The properties of alumina coatings are strongly dependent on the slurry viscosities, which influence the integrity of the washcoat, mechanical properties and even NO conversion. Both series of catalysts have shown a good NO conversion under on-board conditions, although the key parameters of each washcoat are completely different. (C) 2008 Elsevier B.V. All rights reserved.