[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-Caba?as 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.

[es] En esta Tesis Doctoral se describe la preparaci?n y actividad catal?tica de sistemas Cr-arcilla y Ni-arcilla. Los s?lidos Cr-arcilla fueron preparados por dos m?todos, la intercalaci?n con policationes de cromo (o conjunta con policationes de cromo y aluminio) y la impregnaci?n de una arcilla previamente pilareada con aluminio con sales de cromo (acetato de cromo (II), nitrato y acetilacetonato de cromo (III) y cromato am?nico). La arcilla utilizada fue la saponita de Yunclillos-Caba?as. En el caso del sistema Ni-arcilla, dado que este elemento no forma policationes, los s?lidos se prepararon por impregnaci?n, usando el mismo soporte que en el caso anterior, y cloruro, nitrato y acetilacetonato de n?quel(II) como sales precursoras. Adem?s, se intent? la preparaci?n de saponitas sint?ticas con Ni(II) como cati?n octa?drico mediante los m?todos sol-gel y coprecipitaci?n; no se consigui? la s?ntesis de saponita, pero s? de s?lidos con fases de n?quel dispersas sobre aluminosilicatos amorfos, que resultaron ser catal?ticamente activas. Todos los s?lidos fueron caracterizados por diversas t?cnicas, entre ellas an?lisis qu?micos, difracci?n de rayos X, espectroscopias FT-IR y UV-Vis, an?lisis t?rmicos, adsorci?n-desorci?n de nitr?geno, reducci?n a temperatura programada y microscop?a electr?nica. Los catalizadores preparados han sido utilizados en la oxidaci?n de propeno con NOx y ox?geno, encontrando un comportamiento diferente en funci?n del oxidante utilizado y de las condiciones de reacci?n. Tambi?n se aplicaron a la oxidaci?n de hidrocarburos, en concreto, la oxidaci?n de (Z)-cicloocteno para formar el correspondiente ep?xido, y la oxidaci?n de ciclohexano para obtener ciclohexanona + ciclohexanol (mezcla K-A). Los oxidantes fueron yodosilbenceno, para obtener m?s informaci?n sobre el comportamiento de los catalizadores, y H2O2 como ejemplo de oxidante limpio. Las actividades catal?ticas encontradas son muy notables. En el primer caso, la selectividad fue total hacia el per?xido de cicloocteno, mientras en el segundo caso, con conversiones por encima del 30%, se observaron especies de alta valencia o mecanismos radicalarios, dependiendo del catalizador. En todos los casos, los resultados catal?ticos son interpretados, permitiendo alcanzar importantes conclusiones sobre la influencia de los m?todos de preparaci?n de los s?lidos en sus propiedades catal?ticas.