Improvement in stability and regenerability of silica supported platinum-tin catalysts prepared by surface organometallic chemistry. Effect of the tin addition process

Addition of tin by the organometallic route modifies strongly the stability and regenerability of pure Pt/ SiU2 in the reaction of isobutane dehydrogenation to isobutene. Two routes were used : in the first one, tetra n-butyl reacted on the surface of silica supported platinum particles, leading to surface PtSn alloys of different composition. In the second route, tetra n-butyl tin reacted first on the silica surface, to form (=SiO)2-Snn species ; then, platinum particles were generated on the modified silica surface. The stability of these two kinds of bimetallic catalysts has been studied during the oxidation-reduction processes used to regenerate the catalysts. The modification of the structure and texture of the solids was followed by electron microscopy (CTEM and EDAX), or oxygen and hydrogen chemisorption.