The effect of water on the adsorption of NO2 onto a γ-Al2O3 catalyst support surface was investigated using Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). Upon room-temperature exposure of the alumina surface to small amounts of NO2, nitrites and nitrates are formed, and at higher NO2 doses only nitrates are observed. The surface nitrates formed were of bridging monodentate, bridging bidentate, and monodentate configuration. At elevated NO2 pressures, the surface hydroxyls were consumed in their reaction with NO2 giving primarily bridge-bound nitrates. A significant amount of weakly adsorbed N2O3 was seen as well. Exposure of the NO2-saturated γ-Al2O3 surface to H2O resulted in the desorption of some NO2 + NO as H2O interacted with the weakly held N2O3, while the bridging monodentate surface nitrates converted into monodentate nitrates. The conversion of these oxide-bound nitrates to water-solvated nitrates was observed at high water doses when the presence of liquid-like water is expected on the surface. The addition of H2O to the NO2-saturated γ-Al2O3 did not affect the amount of NO x strongly adsorbed on the support surface. In particular, no NO x desorption was observed when the NO2-saturated sample was heated to 573 K prior to room-temperature H2O exposure. The effect of water is completely reversible; i.e., during temperature-programmed desorption (TPD) experiments following NO2 and H2O coadsorption, the same IR spectra were observed at temperatures above that required for H2O desorption as seen for NO2 adsorption only experiments.

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Silver nanoparticles of different morphologies were prepared using the polyol process and then dispersed on alpha-alumina. Catalysts were tested for the selective oxidation of styrene in the gas phase. Activity and selectivity were strongly dependent on the morphology of the silver nanoparticles.

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The effect of water on the morphology of BaO/Al 2 O 3 -based NO x storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO 3 ) 2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO 2 exposure of a H 2 O-containing (wet) BaO/Al 2 O 3 sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO 2 , the nitrites completely convert to bulk nitrates. The amount of NO x taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO 2 exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NO x uptake on similar storage materials.

Catalytic performance of iridium supported on SiO2 was investigated for 5hydroxymethylfurfural (HMF) transformation. Ir/SiO2 catalysts exhibiting different metal loading (1, 3, and 5 wt.%) were tested in the preliminary experiments in the hydrogenation of two probe molecules, e.g. ethyl pyruvate (EP) and ketopantolactone (KP) to evaluate the Ir dispersion on the catalyst activity in C=O hydrogenation. In the transformation of HMF the influence of metal dispersion, iridium precursor and addition of H2SO4 were studied revealing that 2,5-bis-(hydroxymethyl)furan (BHMF) was the main product with 83% selectivity at 70% conversion of HMF over chlorine free Ir/SiO2 together with H2SO4 at 333 K in THF under 10 bar hydrogen. On the other hand, one-pot synthesis of HMF to 2,5dimethylfuran (DMF) was promoted in the presence of chlorine containing Ir/SiO2(Cl) and H2SO4. Both of these products are considered high value-added chemicals from biomassderived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF.

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