In this work, we describe the synthesis of Ag/SiO2 and Ag/Co3O4 nanocomposites by infiltration of aqueous AgNO3 followed by reduction to metallic Ag using ethylene glycol vapor at 165 °C. The SiO2 monolith templates were synthesized using a sol-gel method. The Co3O4 monoliths were prepared by nanocasting, using the SiO2 monoliths as template. The resulting monoliths were characterized by XRD, BET-SA, and SEM. The monolithic nature of the materials, especially with bicontinuous porosity, has many advantages in heterogeneous catalysis. In heterogeneous catalysis, the monolithic form enables the easy separation of catalyst from the reaction mixture without centrifugation or filtering. The catalytic activity of these monoliths was studied for the hydrogenation of methylene blue (MB) (Scheme 1) and methyl orange (MO) (Scheme 2) dyes in presence of NaBH4 as reducing agent. The catalytic hydrogenation reactions of Ag/SiO2 gave the fastest reduction for MB; Ag/Co3O4 gave the fastest MO reduction. Experiments were performed by varying parameters which helped to understand the overall rate of Ag catalyzed reactions along with the rates of the non-catalyzed reaction and the rates of dye adsorption on the supports and silver nanoparticles.

Synthesis, characterization of Ag/SiO2 and Ag/Co3O4 hierarchically porous monoliths and evaluation for hydrogenation of dyes

249th National Meeting (2015)

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