Authors: B. Schimmoeller, H. Schulz, S.E. Pratsinis, A. Bareiss, A. Reitzmann and B. Kraushaar-Czanetzki
Affilation: Swiss Federal Institute of Technology (ETH-Zurich), Switzerland
Pages: 222 - 225
Keywords: flame-spray pyrolysis, direct deposition, ceramic foam/sponge, partial oxidation, o-xylene, vanadia/titania, Raman spectroscopy
Flame-made airborne V2O5/TiO2 nanoparticles were deposited directly onto mullite foam supports making ready-to-use catalysts for the o-xylene conversion to phthalic anhydride. These particles containing 10 wt.% V2O5 were made by combustion of liquid precursor sprays and characterized by transmission electron microscopy, nitrogen adsorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and Raman spectroscopy. V2O5/TiO2 nanoparticles were produced in single step by flame spray pyrolysis having a sub-monolayer, monomeric V2O5 on the titania surface. The specific surface area, the ti-tania and vanadia composition were thermally stable up to 450°C. For higher sinter tem-peratures the SSA decreased drastically by TiO2 phase transformation and grain growth. Catalyst structure was controlled in situ during deposition through the pressure drop across the foam resulting in homogeneous to patchy V2O5/TiO2 coatings. The produced foam catalysts needed no subsequent treatment like calcination as for common wet-made catalysts and could be installed in the reactor for the catalytic evaluation. The coated-foam catalyst revealed higher catalytic activity and similar selectivity to phthalic anhy-dride at high o-xylene conversion compared to a wet-made catalyst. The high vanadia distribution and its monomeric composition on the open foam structure facilitated vana-dia accessibility. Directly coated foam catalysts combine high accessibility, high catalytic yield with favorable support structures (low pressure drop, enhanced heat transfer) and fast production routes, making them attractive for catalytic reactions.