Green synthesis of polypyrrole-supported metal catalysts: application to nitrate removal in water

Pt and Pt/Sn catalysts supported on polypyrrole (PPy) have been prepared using Ar plasma to reduce the metal precursors dispersed on the polymer. The PPy support was synthesized by chemical polymerization of pyrrole with FeCl3·6H2O, this leading to the conducting form of the polymer (conductimetric measurements). The Ar plasma treatment produced a partial reduction of platinum ions, anchored as platinum chloro-complexes to the PPy chain, into metallic platinum. A homogeneous distribution of Pt and Sn nanoparticles was observed by TEM. Activity of the PPy-supported catalysts was evaluated in the reduction of aqueous nitrate with H2 at room temperature. Nitrate concentration in water below the maximum acceptable level of 50 mg L−1 was achieved with all catalysts. However, considering not only efficiency in nitrate reduction, but also minimized concentrations of undesired nitrite and ammonium, the monometallic Pt catalyst seems to be the most promising one.

Influence of peroxometallic intermediaries present on polyoxometalates nanoparticles surface on the adipic acid synthesis

The cyclohexene oxidation by hydrogen peroxide catalysed by polyoxometalates (POM) has been shown as an adequate green route for the adipic acid synthesis. In this study, it has been demonstrated that POM's salts are effective catalysts for this reaction and how peroxopolyoxometalates intermediaries are the truly responsible species of the POM's salts catalytic activity and solubility. However, the latter can be reduced by calcining the catalyst previously. Polyoxomolybdates salts generally present a higher activity than polyoxotungstenates salts. Finally, it must be remarked the positive effect exerted by the acetic acid stabilising the peroxide of hydrogen against its decomposition.