Molecular modelling study of solid acidity in molybdenum oxide supported on silica-alumina
| Autor: | J F Richardson, R Miranda, S Ramani |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
inorganic chemicals
chemistry.chemical_classification Materials science Infrared Catalyst support Inorganic chemistry chemistry.chemical_element Condensed Matter Physics Computer Science Applications Catalysis Acid strength chemistry Mechanics of Materials Molybdenum Modeling and Simulation General Materials Science Redistribution (chemistry) Molecular orbital Chemical composition |
| Zdroj: | Modelling and Simulation in Materials Science and Engineering. 7:459-478 |
| ISSN: | 1361-651X 0965-0393 |
| Popis: | Factors influencing the solid acidity in molybdenum oxides supported on silica-alumina were studied theoretically by means of self-consistent Hartree-Fock (HF), electron-correlated Moller-Plesset (MP2) and local density functional (LDF) quantum mechanical calculations of acid site models. This work was aimed at elucidating relationships between the chemical composition, surface geometry and the electronic properties of the solid acid catalysts. Local structures of unsupported and supported molybdenum oxide inferred from earlier experimental results were studied using cluster models. Relationships between the structural transformations in the molybdenum oxide tetrahedra and the changes in Bronsted-Lewis acidity were identified. The experimentally observed effect of the catalyst support composition on the acid strength of the supported molybdenum oxide catalyst was interpreted in terms of the calculated charge redistribution and molecular orbital energies. An acid site structure is proposed to explain the effect of Mo loading on the Bronsted acidity. The calculated changes in infrared vibration frequencies agree with the measured ones and support the mechanism proposed for the acidity changes on Mo loading. |
| Databáze: | OpenAIRE |
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