COMBINED DESOX DENOX REACTIONS ON A COPPER ON ALUMINA SORBENT CATALYST .2. KINETICS OF THE DESOX REACTION

The kinetics Of SO2 removal from flue gas and adsorption in the form of regenerable surface sulfate species on a copper on alumina sorbent-catalyst were analyzed according to spectroscopic evidence showing the formation of two sulfate species linked to Cu or Al species, respectively. Various kinetic reaction networks, with parallel or consecutive first- or second-order reactions are compared. The best fit of the results was found for a reaction model involving a first step of oxidation of chemisorbed SO2 to chemisorbed SO3 on copper followed by further reaction of the chemisorbed SO3 (i) with a second neighboring copper species to form a sulfate species linked to copper or (ii) a surface transfer to neighboring Al species to form sulfate species linked to Al, leaving a reduced copper site that is rapidly regenerated by gaseous oxygen. This reaction model is in good agreement with reactivity and spectroscopic evidence on the reaction mechanism.