Preparación y actividad catalítica de sistemas cromo-arcilla y níquel-arcilla

[EN]The preparation and catalytic activity of Cr-clay and Ni-clay systems are reported in this Thesis. The Cr-clay solids were prepared by two methods, the intercalation of Cr-polycations (or cointercalation of Cr- and Al-polycations), and the impregnation of aluminum-pillared clay with chromium salts, namely Cr(II) acetate, Cr(III) nitrate and acetylacetonate, and ammonium chromate. Yunclillos-Cabañas saponite was the clay used in all cases. For the Ni-clay system, as this element does not form polycations, the solids were prepared by impregnation, using the same support that in the previous system, and Ni(II) chloride, nitrate and acetylacetonate as precursor salts. Besides, the preparation of synthetic saponites containing Ni(II) in octahedral positions was tried by sol-gel and co-precipitation methods; saponite was not synthesized but nickel phases over amorphous aluminosilicates were prepared, with interesting catalytic properties. All the solids were characterized by several techniques, including chemical analyses, X-ray diffraction, FT-IR and UV-Vis spectroscopies, thermal analyses, nitrogen adsorption-desorption, temperature-programmed reduction and electronic microscopy. These catalysts have been used in the oxidation of propene with NOx and oxygen, finding a different behavior depending on the oxidant used and on the reaction conditions. The catalyst were also used in the oxidation of hydrocarbons, namely the oxidation of (Z)-cyclooctene to form the corresponding epoxide, and the oxidation of cyclohexane to obtain the cylohexanone + cyclohexanol mixture (K-A oil). The oxidants were iodosylbenzene, for gaining more information on the catalytic behavior, and H2O2 as example of green oxidant. Selectivity to cycloocteneoxide was complete in the first case, while in the second case, with conversions even higher of 30%, high-valent species or radical mechanisms were observed depending on the catalyst. In all cases, the catalytic behavior is discussed considering the nature of the solids, allowing to reach important conclusions on the influence of the preparation methods on the catalytic performance of these systems.

Author

• Mata Ortiz, Guiomar

• Tesis y disertaciones académicas
• Universidad de Salamanca (España)
• Tesis Doctoral
• Academic dissertations
• Tecnología de catalisis
• Química inorgánica
• Productos de arcilla
• Procesos químicos
• Chemical processes
• Inorganic chemistry
• Catalysis technology
• Clay products

Identifier

hdl:10366/121384

OAI identifier oai:identifier

oai:gredos.usal.es:10366/121384