ELEMENTARY STAGES IN FREE-RADICAL OXIDATION OF SO2 MOLECULES ON THE SURFACE OF ACTIVATED SILICA - AN EXPERIMENTAL AND THEORETICAL-STUDY OF THE STRUCTURE AND PROPERTIES OF SURFACE INTERMEDIATES

The reactions of SO2 molecules with (=Si-O-)(3)Si-., (=Si-O-)(3)Si-O-. , and (=Si-O-)(3)Si-O-O-. radicals on the SO2 surface are studied. The elementary stages of SO2 chemisorption are analyzed; the structures o f [GRAPHICS] and [GRAPHICS] complexes formed are identified; and the c hemical properties of the complexes are studied. The experimental data are related to quantum-chemical calculations of the electron structur e and geometry of free-radical species modeling surface fragments. A s tage mechanism for free-radical oxidation of SO2 on the silica surface is proposed and discussed.