Un contributo all'utilizzo di idrogeno molecolare in processi ecocompatibili: sintesi diretta di H2O2

Hydrogen peroxide, which annual world production is estimated in 3.5 mil tons/year, is prevalently used in paper industry, chemical synthesis and textile industry. The use of the green oxidant H2O2 is strongly recommended because of the high content of active oxygen and the formation of water as the only oxidation by-product. However, H2O2 is rather expensive, and today its wide employment is unfortunately far. The reaction of direct synthesis of hydrogen peroxide is know from 1914 and it can be considered as a possible strategic solution to obtain in an economic way diluite hydrogen peroxide solution. The Research Group where I carry out this Thesis work has a long experience in the activation of molecular hydrogen and oxygen upon using size controlled metal nanoclusters supported on cross-linked functional polymers. These type of catalysts, were synthesized, characterized by TEM, EXAFS, a-XRD and tested in the direct synthesis of hydrogen peroxide. With Pd°/K2621 catalysts, yields greater than 50% (respect the limiting reagent H2) after 90 minutes were obtained. A very promising catalyst was obtain upon generation of Pd° nanoclusters inside Nafion Sac-13. The support is a super acidic commercial material, obtained by dispersion of the perfluorinated polymer Nafion (13% w/w) on silica. This catalyst showed in the direct synthesis of hydrogen peroxide a very high selectivity (higher than 90%), respect to the limiting reagent H2.