The effect of intraparticle diffusion of catalyst has been investigated in a flow-recirculation glass reactor. The reaction of oxidative dehydrogenation of butene-2 occurred in the kinetic regime over 30-40 mesh Mo3.0 Bi0.9Ce1.1/ SiO2 catalyst. When the particle size of catalyst increased to 5-14 mesh

the reaction of oxidative dehydrogenation of butene-2 occurred in the regime of intraparticle diffusion. The effect of intraparticle diffusion of catalyst increased with the rise of reaction temperature. At 753K

the measured value of catalytic effectiveness factor was 0. 20. The effects of intraparticle diffusion on activation energies of reduction of catalyst by butene-2 and reoxidation of reduced catalyst were measured experimentally. The value of activation energy for butene-2 when intraparticle diffusion controls

is equal to the mean of the activation energy in both the kinetic and the diffusion regime. The effects of intraparticle diffusion on the selectivity of butadiene were investigated. An empirecal equation was set up to represent the effects of intraparticla diffusion on the selectivity of butadiene.