Surface dynamics of adsorbed species on heterogeneous oxidation catalysts. Evidence from the oxidation of C4 and C5 alkanes on vanadyl pyrophosphate

Steady-state and transient reactivity measurements, Fourier-transform IR studies, and stopped-flow desorption analyses of the selective oxidn. of C4 and C5 alkanes at the vanadyl pyrophosphate surface suggest that the surface dynamics of adsorbed species plays an important role in detg. the selective oxidn. pathways and the nature of the products of selective oxidn. The results indicate the possibility of two different oxidn. pathways in maleic anhydride synthesis from n-butane which involve the intermediate formation of either a lactone or furan and which are characterized by different rates and selectivities. The presence of side Me groups in the formation of similar intermediates from n-pentane decreases their reactivity and favors a parallel surface reaction between intermediates with the final formation of phthalic anhydride from the C5 hydrocarbon. However, when the rate of conversion of the intermediates is increased, thus modifying the surface availability of oxygen, maleic anhydride also becomes the principle product from the C5 alkane. [on SciFinder(R)]