Partial Oxidation of o-Xylene to Phthalic Anhydride: Effects of K, Sn and W

Using the grafting method state of the art VOx monolayer on TiO2 catalysts have been prepared and promoted with potassium, tin and tungsten by impregnation, with varied loadings. All catalysts where characterised through Raman spectroscopy, 1H Solid State NMR spectroscopy using several probe molecules, PXRD and more. A plant was set up for catalytic measurements at 350°C and 1.5vol% o-xylene in air at varied space velocities. Through a comparison of catalytic results of promoted and unprompted catalysts it was found that potassium and tungsten lead to higher phthalic anhydride selectivity. At all loadings tin promoted catalysts showed worse performance that the unprompted catalyst. A comparison of published kinetic models showed the Skryzpek model as superior. Simulation of potassium promoted catalytic results showed the shift to a more direct reaction route to phthalic anhydride.