SO2 adsorption on alumina and sulfation with SO2 + O-2 have been investigated by IR spectroscopy and thermogravimetric measurements at temperatures quite similar to Claus process plant operating conditions (280-350 degrees C), The sulfation was studied under various P(SO2) and P(O-2) pressures. The results allow a kinetic model for alumina sulfation to be proposed, The elementary steps of the mechanism involve two types of surface site. The same site contributes to SO2 adsorption as sulfite and to sulfate formation. Another catalytic site leads to oxygen dissociation, On pure alumina the number of this last site is very low. The model enables the weight gain due to the fixation of SO2 and O-2 to be expressed as a function of time, Kinetic constants were calculated from various sulfation experiments and the theoretical expression so obtained fits the experimental curves.