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

摘要

Addition of tin by the organometallic route mofifies strongly the stability and regenerability of pure Pt/SiO_2 in the reaction of isobutane dehydrogenation to isobutene. Two routes were sued: in the first one, tetra n-butyl reacted on the surface of silica supported platinum particles, leading to surface PtSn alloys of differnt composition. In the second route, tetra nb-utyl tin reacted first on the silica surface, to frm (ident toSiO)_2-Sn~II species; then, platinum particles were generated on teh modified silica surface. The stability of these two kinds of bimetallic catalysts has been studied during the oxidation-reductionprocesses 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.