A procedure to prepare metallic nanoparticles homogeneously dispersed on a support by making said support contact a metallic precursor, and characterized in that the support is a powder with a particle size smaller than 44μm of at least one clay possessing a silicate network, selected from rheologic grade sepiolite and rheologic grade atapulgite; and the metallic precursor is a hydrosoluble salt selected from chlorides, nitrates and sulfates of a metallic element selected from Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt, Au, and combinations thereof, that are metallic elements susceptible to reduction at temperatures below the destruction temperature of the clay's silicate network; and characterized in that the procedure additionally comprises: - a deposition stage in which the precursor deposits on the support, said deposition stage comprising: · dissolving the hydrosoluble salt of the metallic element in water to obtain a dissolution of the hydrosoluble salt, · dispersing the support in the dissolution of the hydrosoluble salt of the metallic element to obtain a precursor/support dispersion, · precipitating the precursor on the support by raising the pH of the support/precursor dispersion by means of controlled addition of a base, and · drying the dispersion to obtain dried particles of the support having the precursor precipitated thereon; - a thermal decomposition stage, that is carried out under controlled atmosphere conditions and in which the dried particles are subjected to a decomposition treatment where the precursor precipitated on the support is transformed into an oxide of the metallic element, provided the precursor deposited over the clay is not said oxide, and - a thermal reduction stage carried out under controlled conditions in which the oxide of the metallic element is subjected to a reduction process to obtain nanoparticles of the metallic element deposited on the support, wherein the procedure is carried out at temperatures below the destruction temperature of the clay's silicate network. - a deposition stage in which the precursor deposits on the support, said deposition stage comprising: · dissolving the hydrosoluble salt of the metallic element in water to obtain a dissolution of the hydrosoluble salt, · dispersing the support in the dissolution of the hydrosoluble salt of the metallic element to obtain a precursor/support dispersion, · precipitating the precursor on the support by raising the pH of the support/precursor dispersion by means of controlled addition of a base, and · drying the dispersion to obtain dried particles of the support having the precursor precipitated thereon; · dissolving the hydrosoluble salt of the metallic element in water to obtain a dissolution of the hydrosoluble salt, · dispersing the support in the dissolution of the hydrosoluble salt of the metallic element to obtain a precursor/support dispersion, · precipitating the precursor on the support by raising the pH of the support/precursor dispersion by means of controlled addition of a base, and · drying the dispersion to obtain dried particles of the support having the precursor precipitated thereon; - a thermal decomposition stage, that is carried out under controlled atmosphere conditions and in which the dried particles are subjected to a decomposition treatment where the precursor precipitated on the support is transformed into an oxide of the metallic element, provided the precursor deposited over the clay is not said oxide, and - a thermal reduction stage carried out under controlled conditions in which the oxide of the metallic element is subjected to a reduction process to obtain nanoparticles of the metallic element deposited on the support,