SOLVATED METAL ATOM DISPERSED CATALYSTS

Synthetically useful amounts of solvated metal atoms can be prepared by metal evaporation and low-temperature solvent trapping. When these solvates are warmed metal atom nucleation takes place followed by particle growth. In the presence of a high surface area catalyst support, such as SiO2 or Al2O3, metal atom nucleation takes place at surface -OH groups, followed by particle growth. This procedure serves as an effective method for the preparation of very highly dispersed metallic heterogeneous catalysts, (solvated metal atom dispersed (SMAD) catalysts). Unusual particle structure and high dispersion allow these materials to be extremely active in many catalytic schemes. In addition, the SMAD procedure can be used to prepare new bimetallic particles that are not possible to prepare by conventional procedures. For example, layered bimetallic structures can be obtained whereby the more oxophilic metal reacts with the support - OH groups first, in a sacrifical way, followed by deposition and growth of the second, less oxophilic metal (e.g., Co-Mn/Al2O3). Catalytic properties are altered significantly by the effect of one metal on another, due to this layered structure. In other examples, highly dispersed alloy particles can be prepared by the SMAD procedure (e.g., Pt-Sn). The SMAD procedure represents a new approach to the direct preparation of supported small metal particles and allows the possibility of preparing hitherto unknown layered structures and metastable alloy particles.