THE OXIDATIVE SPECIES ON A VANADYL PYROPHOSPHATE SURFACE - A MODEL FOR SOME STEPS IN THE MALEIC-ANHYDRIDE SYNTHESIS

The electronic structure of different types of adsorbed oxygen species on a vanadyl pyrophosphate surface is analyzed from a frontier orbital point of view and used in a discussion of the oxidation of 1,3-butadiene to adsorbed 2.5-dihydrofuran. The further oxidation of 2,5-dihydrofuran to an asymmetric lactone and to the final product, maleic anhydride is also presented. Two different types of oxygen species on the surface are analyzed: One is the vanadyl oxygen which is suggested to be responsible for the oxidation of 1,3-butadiene to 2,5-dihydrofuran. The other oxygen type is adsorbed molecular oxygen which is proposed to be responsible for the oxidation of the adsorbed 2,5-dihydrofurans to a 2-hydroxy derivative of dihydrofuran followed by an oxidation to the asymmetric lactone. The 5-position is suggested to become oxidized in a similar way.