Effect of the aging time of PVP coated palladium nanoparticles colloidal suspensions on their catalytic activity in the preferential oxidation of CO

Palladium nanoparticles protected by polyvinylpyrrolidone (PVP) have been synthesized by the reduction-by-solvent method and deposited onto alumina by the wet impregnation method. The metallic colloid has been left for different times (aging times) at room temperature and under open bench conditions before deposition of the particles on the support. The colloids have been analyzed by TEM, and the catalysts prepared have been characterized by TEM, TG-MS, XPS and IR spectroscopy. The catalytic activity of the nanoparticles has been tested in the preferential oxidation (PrOx) of CO reaction, which consists in CO removal from H2-rich streams. The reaction was conducted up to 200 °C and with a gas composition similar to that coming out from a reformer (2% CO, 2% O2, 30% H2, He). The aging time of the colloidal suspensions, i.e. the time elapsed between colloids preparation and deposition, does not have an influence over the nanoparticles size or shape. However, this parameter has shown a great influence on the catalytic behavior of the metal nanoparticles, affecting both their catalytic activity and selectivity. The catalyst impregnated with the immediately prepared nanoparticles is the one showing the best catalytic properties in this work. The amount of polymer anchored to the particles surface and its interaction with the metal surface has been found to be responsible for these observations.

Palladium nanoparticles protected by polyvinylpyrrolidone (PVP) have been synthesized by the reduction-by-solvent method and deposited onto different supports by impregnation. The catalytic activity of the nanoparticles has been tested in the preferential oxidation of CO reaction. The aging time of the colloidal suspensions, i.e. the time elapsed between colloids preparation and deposition, has shown a great influence on the catalytic behavior of the metal nanoparticles, affecting both their catalytic activity and selectivity. The amount of polymer anchored to the particles surface and its interaction with the metal surface has been found to be responsible for these observations.Figure optionsDownload high-quality image (93 K)Download as PowerPoint slideHighlights
► Phosphotungstates exhibits high catalytic activity for monoterpenes oxidation.
► Lacunary PW11 revealed to be the best of the studied catalyst.
► Phosphotungstates were immobilized onto amine-modified SBA-15.
► Composite materials showed to be active and stable catalysts.