Cogelation: an effective sol-gel method to produce sinter-proof finely dispersed metal catalysts supported on highly porous oxides

Image analysis of X-ray microtomograms of Pd?Ag/SiO2 xerogel catalysts supported on Al2O3 foams

“…To a suspension containing 0.121 g of insoluble palladium acetylacetonate powder (Pd(acac) 2 , Aldrich 20, 901-5) and 0.131 g of insoluble silver acetate powder (AgOAc, Aldrich 20, 437-4) in 13.03 ml of ethanol denaturized with 0.5% of diethyl phthalate (DEP), 0.51 ml of [3-(2-aminoethyl)aminopropyl]trimethoxysilane (EDAS, ABCR 1760-24-3, industrial grade) is added. This mixture is stirred at ambient temperature in a closed vessel during 1 h to allow EDAS to form complexes with Pd and Ag [1].…”

“…Previously, the synthesis by cogelation, the characterization and the catalytic properties of Pd-Ag/SiO2 xerogel catalysts have been reported [1,2]. This cogelled catalyst is devoted to the selective hydrodechlorination of chlorinated alkanes into alkenes.…”

CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

“…The catalysts were prepared using the sol-gel method and dried under conditions with supercritical ethanol at 260 • C. This synthesis method described in a previous study [26] ensured the synthesis of well-dispersed Pd nanoparticles on a silica support. The silica gel was impregnated with metal ions before the drying step to replace the pores previously filled with the solvents used in the synthesis, which leads to hierarchical porosity.…”

“…The presence of a large number of smaller Pd particles (2-5 nm) in the framework (marked by yellow arrows) located inside the mesoporous framework of SiO 2 aerogels homogeneously dispersed within the SiO 2 network and a few large surface particles (20-40 nm) (marked by magenta arrows). This unique texture is believed to occur due in the samples prepared by the sol-gel synthesis resulting in a better catalytic activity and effectively hindering the sintering of Pd particles [26]. The average size estimated from over 200 particles shows a mean size of the Pd particles in as-synthesized particles as 6.1 nm.…”

Assessment of the 3D Localization of Metallic Nanoparticles in Pd/SiO2 Cogelled Catalysts by Electron Tomography

“…7 Interestingly, it seems from TEM that the metallic crystallites in these materials are buried inside the silica skeleton, 1,2,[7][8][9][10][11] which seems also to be compatible with some preliminary XPS analysis. 12 Notwithstanding their localization, the crystallites are accessible, as demonstrated by the chemisorption measurements and by the high catalytic activity. For higher metal loadings, a significant amount of metal is also present outside of the silica skeleton, under the form of a large crystallite with a width of a few tens of nanometers (e.g., ref 7).…”