Alloying Effect in Low Loaded Rh Catalysts Supported on High Surface Area Alumina on Their Activity in CH4 and NO Decomposition

In the alloys of transition metals (TM) and main group ones (MGM) the valence electrons from MGM can fill the d band of the TMs entirely and slightly increase the number of electrons in their s band (Azaroff, 1960; Kittel, 2005). Such Rh atoms enriched in electrons, present in Al-Rh alloys, were found to be very active electron donors (Pietraszek et al., 2007). It was revealed that they transfer the electrons to the antibonding Л orbital of adsorbed nitric oxide molecules causing NO decomposition to dinitrogen and dioxygen (Pietraszek et al., 2007). Due to the great difference in the Al and Rh electro-negativity, the alloys are sometimes considered as nonstoichiometric chemical compounds. Because of the large range of nonstoichiometry those compounds should rather be estimated as intermediate phases (IP) (Azaroff, 1960). The presence of the Al-Rh alloy nanocrystallites isostructural with Al9Rh2 (Bostrom et al., 2005) was earlier revealed in the freshly prepared Rh/δAl2O3 catalysts containing 0.06 and 1.5 wt.% Rh (Pietraszek et al., 2007; Zimowska et al., 2006)..

Hydrogen production from oxidative steam-reforming of n-propanol over Ni/Y 2O 3-ZrO 2 catalysts

Oxidative steam reforming (OSR) of n-propanol was studied over new Ni catalysts (ca. 7% Ni wt/wt) supported on Y 2O 3-ZrO 2 oxides with different yttrium content (2-41 % Y 2O 3 wt/wt). Materials were characterized by X-ray diffraction, temperature-programmed reduction, X-ray photoelectron and Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis and high resolution transmission electron microscopy. Samples were used in calcined form and tested in the temperature range 673-773 K using a reactant feed of n-propanol/water/O 2 at a molar ratio 1/9/0.5. Hydrogen production is related with the support composition and Ni dispersion. Copyrigh

H2 production from oxidative steam reforming of 1-propanol and propylene glycol over yttria-stabilized supported bimetallic Ni-M (M = Pt, Ru, Ir) catalysts

This paper reports hydrogen production from oxidative steam reforming of 1-propanol and propylene glycol over Ni-M/Y2O3-ZrO 2 (10% wt/wt Y2O3; M = Ir, Pt, Ru) bimetallic catalysts promoted with K. The results are compared with those obtained over the corresponding monometallic catalyst. The catalytic performance of the calcined catalysts was analyzed in the temperature range 723-773 K, adjusting the total composition of the reactants to O/C = 4 and S/C = 3.2-3.1 (molar ratios). The bimetallic catalysts showed higher hydrogen selectivity and lower selectivity of byproducts than the monometallic catalyst, especially at 723 K. Ni-Ir performed best in the oxidative steam reforming of both 1-propanol and propylene glycol. The presence of the noble metal favours the reduction of the NiO and the partial reduction of the support. The NiO crystalline phase present in the calcined catalysts was transformed to Ni during oxidative steam reforming. The adsorption and subsequent reactivity of both 1-propanol and propylene glycol over Ni-Ir and Ni catalysts were followed by FTIR; C-C bond cleavage was found to occur at a lower temperature in propylene glycol than in 1-propanol