Study of the reaction mechanisms between Sn-(n-C4H9)4 and alumina surface sites: Application to the controlled preparation of PtSn/Al2O3 catalysts

The reaction mechanisms between Sn-(n-C4H9)4 and several specific types of surface sites on alumina are studied. A surface treatment is described allowing the complete elimination of reactive surface sites and avoiding the anchoring of Sn-(n-C4H9)4 on the support. This surface deactivation is applied to the preparation of bimetallic PtSn/Al2O3 catalysts by controlled selective decomposition of Sn-(n-C4H9)4 on the reduced metallic particles of a Pt/Al2O3 catalyst. The resulting bimetallic particles are analysed by 119Sn Mössbauer spectroscopy at different stages of the preparation procedure. The tin anchoring sites on the platinum particles are identified on the basis of their specific Mössbauer hyperfine parameters. Tin atoms in contact with the support or with platinum are distinguished from those enclosed in bulk-SnO2-like agglomerates. A structural model is proposed describing at an atomic scale the morphology of the bimetallic particles and their evolution under various heat treatments. The results are compared with those of a catalyst prepared by conventional impregnation methods on a not specifically pretreated support.

Graphical abstractThe reaction mechanisms between Sn-(n-C4H9)4 and several specific types of alumina surface sites are studied. A new preparation method for the controlled synthesis of bimetallic PtSn/Al2O3 catalysts is presented avoiding undesired anchoring of tin on the support. The bimetallic particles are analysed by 119Sn Mössbauer spectroscopy and a structural model of the particles is proposed. Figure optionsDownload full-size imageDownload as PowerPoint slide