Abstract: Colloid impregnation and ion-exchange methods for the preparation of platinum-containing zeolites offer two distinct types of catalysts. The former leads to the stabilization of platinum nanoparticles on the outer surface of the zeolite, while the latter introduces Pt inside the micropores. The active sites are consequently confined in two different locations, as shown by two-dimensional pressure jump of adsorbed species infrared (2D-PJAS-IR) spectroscopy, and the activity in CO oxidation is found to be lower when Pt is in the pores. After ageing in air, both catalysts undergo a partial oxidative redispersion and Pt atoms are then found both on the external surface and in the pores. The presence of electron-deficient Pt species entrapped in the micropores is also evidenced by operando FTIR spectroscopy, through adsorbed dicarbonyl complexes, and chemometrics. Such particular species vanished at 475 K during the CO oxidation reaction and gave rise to metallic nanoparticles located in the pores.

Abstract: A Low Pressure Glow Discharge Reactor has been designed to allow time resolved infrared spectroscopic investigation of the discharge zone in practical conditions. The benefits of such reactor are demonstrated through the study of the evolution in the IR spectra of air / CO2 gas mixture at the microsecond time–scale. It has been shown that the spectra are greatly affected by the electrical discharge in the 2400–2200 cm–1 region, where the asymmetric stretch mode of CO2 falls. The CO2 molecules are excited through a collision with excited N2 molecules, where the transfer of energy occurs by a resonant effect. The mechanisms involved are reversible and following plasma pulses.

Abstract: Four sets of Rh-Ge/TiO2 bimetallic catalysts were prepared by surface redox reaction (i.e., catalytic reduction method) between hydrogen activated on a Rh parent catalyst and a Ge salt dissolved in aqueous solution. The four sets of catalysts differ depending on the presence or absence of chloride ions in the Rh and Ge precursor salts used (i.e. RhCl3 vs Rh(NO3)3, GeCl4 vs GeO2). Samples were reduced at either a lower temperature (300°C) or at a temperature chosen to induce a strong metal-support interaction (SMSI) effect (500°C). Catalysts were characterized by elemental analysis, transmission electronic microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy of adsorbed CO, and evaluated for their activity for the gas phase dehydrogenation of cyclohexane and selective hydrogenation of citral. Regardless of the nature of the Rh and Ge precursor salts, the catalytic reduction method causes the Ge to be in intimate contact with the Rh particles, favoring the citral hydrogenation toward unsaturated alcohols (UA: nerol and geraniol). For low Ge loadings, the bimetallic effect can be combined with the SMSI effect. It was observed that the UA selectivity is directly correlated to the ratio R (R = ∑A(COads on oxidized Rh≥1+ species) / ∑A(COads on total exposed Rh species)) determined by FTIR. A better UA selectivity is obtained when bimetallic catalysts possess a surface in a predominantly oxidized state, a situation that is enhanced when chlorinated rhodium and germanium precursors are used.

Abstract: The interaction of phenol, anisole and guaiacol, representatives of oxygenate functions
present in pyrolysis bio-oils, with oxides as silica, alumina (pure or doped with K or F), and
silica-alumina is investigated by infrared spectroscopy. While phenolic-type compounds
mainly interact via H-bonding with silica, chemisorption is their main mode of adsorption on
alumina. Besides, guaiacol interacts very strongly by forming doubly-anchored phenates
instead of mono-anchored ones with phenol and anisole. At temperatures typical of HDO
operating conditions (~673 K), the phenate-type species cover 2/3 of the alumina surface.
This study clearly indicates that substantial carbon deposition could take place on alumina
supported HDO catalysts. Hence, this suggests that silica-based supports should be considered
as potential candidates to design HDO catalyst with better stability.

Abstract: The present paper investigates the development of Ir-based catalysts supported on tungstated aluminas for the ring-opening reaction of naphthenic molecules using methylcyclohexane(MCH) as a model compound. A series of tungstated aluminas WOx/Al2O3 containing up to 6.0 at W/nm2 was prepared. Ir-based catalysts containing 1.2 wt % were obtained by impregnation of these solids. The performance of Ir/WO3/Al2O3 catalysts for methylcyclohexane ring opening was found to be similar to that observed over the corresponding zirconia-based system indicating that the metal-acid balance (and not the nature of the support) is the key parameter for optimum performance.