Selective oxidation of pentane on 12-molybdovanadophosphoric acids

The selective oxidn. of n-pentane on 12-molybdovanadophosphoric acids with 0, 1, 2, and 3 V atoms was studied and compared with the behavior of vanadyl pyrophosphate. Catalysts were characterized before and after the catalytic test by ESR, FTIR spectroscopy, SEM, DSC, Kr BET surface area, and visible diffuse reflectance spectroscopy. The activity in the n-pentane conversion process increased linearly with increasing no. of V atoms, except for the H6PMo9V3O40 sample, for which physico-chem. characterization suggested partial surface degrdn. during the catalytic tests. A turnover frequency of ∼5 × 10-4 mols. of n-pentane transformed per atom of V and per s for both 12-molybdovanadophosphoric acids and vanadyl pyrophosphate was calcd. Oxidn. of n-pentane on heteropoly compds. formed only maleic anhydride and the selectivity increased linearly with increasing no. of V atoms present in the Keggin unit. In contrast, under the same reaction conditions both maleic and phthalic anhydride were formed on vanadyl pyrophosphate. [on SciFinder(R)]