From materials science to catalysis : influence of the coating of 2D- and 3D-inserts on the catalytic behaviour of VOx/TiO2 in oxidative dehydrogenation of propane

The chemistry of the coating of stainless steel plates and foams with VOx/TiO2 catalyst to be utilised in the oxidative dehydrogenation of propane is described. A primer layer of SiO2 was first deposited by RPECVD, to anchor the active phase, to accommodate the difference of dilatation coefficient with steel and to act as a barrier against diffusion of poisonous steel elements. The coated VOx/TiO2 foams were inserted in a tube that could also be loaded with VOx/TiO2 powders to compare their catalytic performance. Preliminary results showed that the selectivity to propene was higher by 10% on silica-protected (ca. 5 μm thick) VOx/TiO2 foam than in the absence of silica, and higher by more than 20% than VOx/TiO2 powders at any conversion. The better performance was attributed to enhanced heat and mass transfers due to turbulent flow regime and to the high conduction of metallic foam. Hot spots which generate over-oxidation of propene were avoided. The choice of the substrate material, of which depend the mechanical and chemical properties of the active phase coating, and of the reactor configurations vs. the efficiency of heat and mass transfers was also commented.