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.

Abstract: Desilication of ITQ-4 (IFR code, 1-dimensional 12-MR channel system of 0.62nm×0.72 nm) in aqueous NaOH solutions was practiced in order to produce the zeolite in the hierarchical form, i.e. combining the native micropores with a secondary network of intracrystalline mesopores. The parent material (Si/Al = 32) was synthesized using benzylquinuclidinium as the structure-directing agent in the presence of fluoride anions. The samples were characterized by ICP-OES, XRD, TEM, N2 adsorption, and FTIR spectroscopy. In a representative treatment, the mesopore surface area of the ITQ-4 experienced a sevenfold increase (from 29 to 206m2 g−1) upon optimized NaOH post-treatment, whereas the microporosity was reduced by 70% (from 0.20 to 0.06cm3 g−1). Chemical analysis and infrared spectroscopy of adsorbed pyridine showed that after alkaline treatment the amount of Brønsted acid sites remains practically constant whereas a significant increase in Lewis acid sites was obtained. Infrared studies with adsorbed 2,4,6-collidine concluded that the accessibility of acid sites in the hierarchical zeolite increased substantially due to an increase in the available active sites at the pore mouths of the hierarchical zeolite.