Catalytic property of vanadyl pyrophosphates for selective oxidation of n-butane at high n-butane concentrations

Selective oxidation of n-butane to maleic anhydride was studied at high con centrations of n-butane up to 5.0 vol.% using three kinds of (VO)(2)P2O7 ca talysts having differently shaped microcrystallites; rose-petals (catalyst A), plates (catalyst B), and blocks (catalyst C). The catalytic activity fo r maleic anhydride formation per unit surface area greatly depended on the kinds of catalysts at the high concentration of n-butane (5.0 vol.%); catal yst A was much more active, while there was no difference at the low concen trations. That catalyst A gave higher rates of the re-oxidation and reducti on, which was established from the measurements of reduction of the catalys t, aged in the reaction mixture, with n-butane and subsequently re-oxidatio n with O-2. In addition, catalyst A showed a larger reaction order of n-but ane concentration. Therefore, the higher catalytic performance of catalyst A at the high concentration of n-butane is attributed to the higher redox a bility of the catalyst, and this is probably brought about from the structu ral disorder of the surface. (C) 2001 Elsevier Science B.V. All rights rese rved.