The oxidation of o-xylene to phthalic anhydride was carried out in a pilot plant with a tubular reactor in order to investigate the heat transfer properties of different types of catalytic fixed beds through analysis of the temperature profiles arising upon polytropic o-xylene conversion. Ceramic sponges of different materials and pore densities were compared to a packed bed of spheres, all of which were coated with novel flame-made vanadia/titania catalyst nanoparticles. The temperature profiles were smoother and hot spot temperatures were found to be lower when sponges were employed as catalyst supports. The strongest reduction of the hot spot temperature was achieved with a sponge packing made of silicon carbide, showing the potential to significantly improve the productivity of the process.