FT-IR and FT-FIR studies of vanadium,molybdenum and tungsten oxides supported on different carriers

In the far IR region at low molybdenum loadings, Mo-SiO₂ catalysts present a pseudomolybdate or a polymolybdate species, while bulk-like MoO₃ appears at loadings close to the geometrical monolayer coverage. W-SiO₂ and V-SiO₂ spectra show bands close to those observed on the corresponding bulk oxides.In the case of TiO₂, Al₂O₃, ZrO₂ supported catalysts, a band is observed near 1000 cm^–1 which is assigned to the Mo=O stretching vibration of coordinatively unsaturated Mo ⁿ⁺ ions showing a stronger interaction with the support than one observed on silica.     

Existence results for bellman equations and maximum principles in unbounded domains

The purpose of this paper is to extend known existence results for Hamilton-Jacobi-Bellman equations. The classical results give existence, uniqueness and Holder regularity when all elliptic operators involved have nonpositive zero-order term. We want to handle here the more general case where they have principal eigenvalues bounded below by a positive constant. As a motivation for this work, we give an application to the study of the Maximum Principle in infinite cylinders, following a work by Berestycki, Caffarelli and Nirenberg [2]. This is used to extend the cylindrical symmetry result in [2] to a more general class of operators.     

Characterization of Pd-Cu alloy nanoparticles on gamma-Al2O3-supported catalysts

Cu-Pd/Al2O3 bimetallic catalysts have been characterized by XRD, TEM, and EDX techniques. The surface structure has been investigated by FT-IR spectroscopy of low-temperature adsorbed CO in the reduced and in the oxidized state. Evidence has been provided of the formation of Cu-Pd alloy nanoparticles, both of the alpha-phase (disordered fcc) and of the beta-phase (ordered CsCl-type). IR spectra suggest that Cu likely decorates the edges while Pd mostly stays at the main faces. Part of copper disperses as Cu+ on the support even after reduction. The presence of copper seems to modify strongly the sate of oxidized Pd centers in oxidized high-Pd content materials. The redox chemistry of the system, where Pd is reduced more easily than Cu, appears to be very complex.     

Skeletal vibrations of cuprate superconductor-like phases: a comparison of the FT-FIR spectra of La2−x Sr x CuO4, Nd2−x Ce x CuO4 and RBa2 Cu3 O7−x (R=Ln or Y) Powders

Il Nuovo Cimento D - The FT-IR/FT-FIR spectra of powders of Nd2−x Ce x CuO4 and La2−x Sr x CuO4 solid solutions and of RBa2Cu3O7−x with R=Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and...     

Infrared studies of the diatomic molecules O2, N2, NO and H2 adsorbed on Fe2O3

An infrared spectroscopic study of the diatomic molecules O₂, N₂, NO and H₂ adsorbed under different conditions on Fe₂O₃ has been performed.Complex patterns of absorption on both α-Fe₂O₃ and γ-Fe₂O₃ activated in O₂ at high temperature are assigned to vibrations of two different chemisorbed O₂ species.N₂ molecules do not interact with “oxygen rich” α-Fe₂O₃ surfaces, but give N₂O^? and N₂O₂^2? species when chemisorbed on evacuated surfaces.NO molecules give complex patterns of absorption, depending on the gas pressure. Three different types of nitrate structures can be identified, as well as NO, NO^? and cis-N₂O₂ chemisorbed species. Chemisorbed water molecules are formed by contact of H₂ with Fe₂O₃ surfaces even at room temperature.     

Initial steps in the production of H2 from ethanol: A FT-IR study of adsorbed species on Ni/MgO catalyst surface

Reactivity of pure ethanol and acetaldehyde on Ni/MgO catalyst at different reaction temperatures was investigated confirming that hydrogen production is ascribable to a series of consecutive and/or parallel reactions. FT-IR studies on adsorbed dry molecules (ethanol or acetaldehyde) showed that ethanol decomposition occurs on catalyst surface through formation of acetaldehyde, which is converted to acetates and then to carbonates, or decomposes to CO, C and H₂.