The adsorption and selective oxidation reaction of C4 hydrocarbon (%n%-butane

1-butene and 1

3-butadiene) to Maleic Anhydride on a commercial VPO catalyst have been investigated by in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) with High Temperature/High Pressure chamber (HTHP) under steady-state conditions. The Catalyst was exposed to the flow of 50 mL/min of 1.5 moL% C4 in air mixture at different temperatures ranged from 50 to 400 ℃ in the HTHP chamber. Spectroscopic investigations show that the adsorption of C4 hydrocarbon on the VPO catalyst surface is very weak; Selective oxidation products (MA) and combustion products (CO

CO-2 and H-2O) could be confirmed on the catalyst surfaces. C4 hydrocarbon reacts with oxygen on the surface of the VPO catalyst according to Rideal mechanism. Adsorbed Maleic acid and activated olefin were detected as surface intermediates; this suggests that olefins and maleic acid could be intermediates in paraffin selective oxidation.