Platinum–Vanadium Oxide Nanotube Hybrids

The present contribution reports on the features of platinum-based systems supported on vanadium oxide nanotubes. The synthesis of nanotubes was carried out using a commercial vanadium pentoxide via hydrothermal route. The nanostructured hybrid materials were prepared by wet impregnation using two different platinum precursors. The formation of platinum nanoparticles was evaluated by applying distinct reduction procedures. All nanostructured samples were essentially analysed by X-ray diffraction and transmission electron microscopy. After reduction, transmission electron microscopy also made it possible to estimate particle size distribution and mean diameter calculations. It could be seen that all reduction procedures did not affect the nanostructure of the supports and that the formation of metallic nanoparticles is quite efficient with an indistinct distribution along the nanotubes. Nevertheless, the reduction procedure determined the diameter, dispersion and shape of the metallic particles. It could be concluded that the use of H2PtCl6 is more suitable and that the use of hydrogen as reducing agent leads to a nanomaterial with unagglomerated round-shaped metallic particles with mean size of 6–7 nm

Growth of copper nanoparticles within VOx nanotubes

The synthesis of new Cu-VOx nanotubes has been achieved by exchanging a Cu(II) salt against the protonated template in the parent dodecylamine-VOx nanotubes. The intercalation of Cu(II) species induces some significant morphological and structural changes within the material, but the tubular shape is still well preserved. Controlled thermolysis under nitrogen of the Cu(II) species initially dispersed within the multiwalls induces the growth and sintering of copper nanoparticles, which are formed without destroying the tubular morphology of the host carrier. (C) 2002 Elsevier Science B.V. All rights reserved

Trapping of CH3I by silver-exchanged faujasite zeolites: a mechanistic study using operando spectroscopies

International audienc

Trapping of CH3I by silver-exchanged faujasite zeolites: a mechanistic study using operando spectroscopies

International audienc

Modification of Y Faujasite zeolites for the trapping and elimination of a propene-toluene-decane mixture in the context of cold-start

International audienceThe modification of a HY zeolite (with Si/Al ratio = 2.5) by impregnation with a platinum salt or ion exchange with Cu2+ cations was carried out in order to evaluate the potential interest of the obtained materials as hydrocarbon traps for cold-start application. Textural, structural and chemical characterizations were carried out using N-2 adsorption isotherms at -196 degrees C, XRD and DRIFTS of adsorbed CO and NO. Acidic properties of the parent H/Y and Cu- and Pt-modified zeolites were determined using FTIR of adsorbed pyridine. The methodology used to investigate the adsorption behaviour of the parent and modified HY zeolites consisted in: (i) analysing qualitatively and quantitatively the breakthrough curves obtained at 35 degrees C during the adsorption of a ternary hydrocarbon mixture (propene, toluene, decane) as well as the data from subsequent temperature-programmed experiments (TPD under He or TPSR in presence of 10%O-2 or 10%O-2/0.2%NO) (ii) establishing relationships between adsorption/reactivity data and the structural, textural and chemical properties of the modified zeolites. Namely, the introduction of copper and platinum species considerably improves the adsorption of unsaturated hydrocarbons, such as propene or toluene, at the expense of decane. This results in a more adequate balance between all the hydrocarbons adsorbed, which is required for cold-start application. In addition, Cu/Y and Pt/Y zeolites were also found to be efficient for the removal of NOx or HC total oxidation, respectively

A Combined DRIFTS and DR-UV-Vis Spectroscopic in Situ Study on the Trapping of CH3I by Silver-Exchanged Faujasite Zeolite

International audienceThe mechanism of CH3I adsorption and thermal decomposition by a Ag/Y sorbent with 23 wt % of silver and a Si/Al ratio of 2.5 was investigated using two different spectroscopic techniques. On the one hand, DR-UV-vis spectroscopy was used to monitor the evolution of silver species and their transformation to silver iodide AgI clusters during increasing exposure to gaseous methyl iodide and upon heating under dry and wet atmospheres. On the other hand, the evolution of adsorbed organic species was investigated under similar conditions by DRIFTS. The latter data were correlated with the evolution of gaseous products to elucidate the mechanistic pathways involved in the trapping and catalytic decomposition of CH3I. © 2016 American Chemical Society