Preparation and characterization of VOx/TiO2 catalytic coatings on stainless steel plates for structured catalytic reactors

The parameters to be controlled to coat metallic walls by VOx/TiO2 catalysts which are used in the mild oxidation of hydrocarbons and NOx abatement are studied. Stainless steel (316L) was chosen because of its large application in industrial catalytic reactors. TiO2 films on stainless steel were obtained by dip-coating in two steps. Superficially oxidized plates were first dipped in Ti-alkoxide sol-gel to be coated by a very thin layer of TiO2, On this anchoring layer was then deposited a porous film of titania by dipping plates in an aqueous suspension of TiO2 particles. After calcination, VOx species were grafted to TiO2/SS plates and their loading was determined by means of X-ray photoelectron spectroscopy. The chemical and mechanical resistances of films were controlled by several tests. Laser Raman spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize the samples after each step of preparation. The porous texture was deter-mined using a thermobalance. The dispersion and the nature of VOx species and the value of theoretical monolayer of VOx on TiO2/stainless steel are shown to depend on the surface V/Ti ratio, in the same manner as for VOx/TiO2 coating anodised aluminum plates and as for VOx/TiO2 powders. Therefore, we have demonstrated that the shaping of TiO2 has no influence on the characteristics of the active phase, which is of prime importance for catalytic applications in structured reactors. (c) 2006 Elsevier B.V. All rights reserved.