Mesostructural material, for use as catalyst, has specific BET surface, and is based on oxide of cerium, zirconium or titanium linked together by mineral matrix

摘要

Nanometric particles (p) based on an oxide of cerium, zirconium or titanium are linked together by a mineral matrix (m) with a silica base containing cations of a metal (M) which is aluminum or titanium. At least some of the cations are in tetrahedric positions in the silica structure. The global molar ratio M/Si of the material is greater than or equal to 5%, preferably 10% and at least 10% (preferably 15%) by mole of the metal (M) is in the form of cations in tetrahedric positions in the silica structure. The metal cations in the silica structure are spread throughout the mineral with a concentration gradient decreasing from the surface to the core. The particles (p) in the structure of the material have a partially accessible surface. If the metal is aluminum, at least 20% of the aluminum present is in the form of cations in tetrahedric positions in the silica lattice and the molar ratio of the total quantity of aluminum to the total quantity of silica is 5-50%. If the metal is titanium, at least 10% of the titanium present is in the form of cations in tetrahedric positions in the silica lattice and the molar ratio of the total quantity of titanium to the total quantity of silica is between 5 and 80%. The material can contain a mixture of aluminum and titanium cations. The material is thermally stable and contains at one local position one or more mesostructures chosen from mesoporous structures with 3-dimensional hexagonal symmetry P63/mmc, 2-dimensional hexagonal symmetry la3d.lm3m or Pn3m, vesicular or lamellar mesostructures or vermicular mesostructures. The particles are spherical or isotropic in shape with at least 50% of the population having a mean diameter of 1-10 nm. The molar ratio SiO2/(CeO2+ZrO2+TiO2) in the material lattice is 20:80 - 99.5:0.5. The particles are 30-100% crystalline. An Independent claim is included for a method for manufacturing the above material, by making the mineral mesostructure such that the silica matrix does not completely cover the metal oxide particles, introducing the metal M into the structure and subjecting the mesostructure to 300-1000 degreesC. The mineral mesostructure is made by forming an initial medium comprising a textural agent and an amphiphilic tensioactive component to form micelles in the reaction medium; adding a colloidal dispersion of the nanometric particles to the mixture, adding a silica alkali or alkoxide mineral precursor to form the mesostructure containing the particles and eliminating the textural agent by heat treatment or solvent.