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Abstract: We prepared Ru catalysts supported on various aluminum oxides with different crystalline phases, viz. α-Al2O3, κ-Al2O3, γ-Al2O3, η-Al2O3, δ-Al2O3 and θ-Al2O3, by the incipient wetness method and applied them to the selective CO oxidation in a hydrogen-rich stream. For comparison, the complete CO oxidation in the absence of H2 was also carried out over the same catalysts. Ru/α-Al2O3 showed the highest CO conversion among the tested catalysts, especially at low temperatures, irrespective of the presence of H2. For all of the catalysts, the catalytic activity for CO oxidation was much suppressed in the absence of H2 compared with that in the presence of H2. Several techniques: N2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), CO chemisorption, temperature-programmed oxidation (TPO), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of CO2 with mass spectroscopy and transmission electron microscopy (TEM) were employed to characterize the catalysts. The least amount of chemisorbed CO and CO2 was obtained at room temperature over Ru/α-Al2O3. The least amount of O2 was chemisorbed during TPO and the oxidized Ru species could be fully reduced in the presence of hydrogen at the lowest temperature over Ru/α-Al2O3 among the Ru/Al2O3 catalysts. Ru/α-Al2O3 can reduce a high inlet concentration of CO to less than 10ppm even in the presence of H2O and CO2 over a wide temperature range. [Copyright &y& Elsevier]

Abstract: We conducted a comparative study for the water-gas shift (WGS) reaction over ceria-promoted Pt catalysts supported on various supports such as γ-Al2O3, SiO2, TiO2 (P-25), CeO2, SiO2-Al2O3, yttria-stabilized zirconia (YSZ) and ZrO2 in a rather severe reaction condition such as 6.7vol.% CO, 6.7vol.% CO2, and 33.2vol.% H2O in H2. Among them, Pt-Ce/TiO2 showed the highest WGS activity especially at low temperatures. The effect of preparation sequences on the catalytic activity was also examined for ceria-promoted Pt supported on TiO2 and Pt-Ce/TiO2 prepared with a single-step co-impregnation method showed the highest water-gas shift activity. The CO chemisorptions, the temperature-programmed reduction (TPR), an inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and a transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX) were conducted to characterize catalysts. The close correlation between the low-temperature water-gas shift activity and the amounts of chemisorbed CO as well as the degree of interaction between Pt and ceria has been observed. This Pt-Ce/TiO2 showed the more stable catalytic activity in the cyclic operation and the start-up/shut-down operation compared with the conventional Pt-Ce/CeO2. [Copyright &y& Elsevier]

Abstract: The gas-phase dehydration of glycerol was conducted over silica–alumina catalysts with different Si/Al molar ratios. For comparison, SiO2 and η-Al2O3 were also examined. A variety of techniques, X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed oxidation (TPO) with mass spectroscopy (MS), infrared spectroscopy (FT-IR) after the adsorption of pyridine or glycerol, solid-state 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS/NMR) spectroscopy, Raman spectroscopy, and CHNS analysis, were employed to characterize the catalysts. The initial glycerol conversion at 315°C was strongly dependent on the total amount of acid sites over the silica–aluminas. The acrolein yield was proportional to the concentration of the Brønsted acid sites, whereas the 1-hydroxyacetone yield was proportional to the concentration of the Lewis acid sites. Among the tested catalysts, Si0.8Al0.2O x showed the highest acrolein selectivity during the initial 2h of the reaction. As long as the molar ratio between water and glycerol was in the range 2–11, the acrolein selectivity increased significantly with the water content of the feed. [Copyright &y& Elsevier]

Abstract: Three catalysts, 1wt.% Pt/Al2O3, 20wt.% Cu/Al2O3, and 1wt.% Pt–20wt.% Cu/Al2O3 were evaluated for the oxidation of NO by O2 and the selective catalytic reduction (SCR) of NO x by NH3 in the absence and presence of H2O. The Pt/Al2O3 catalyst exhibited the largest values in NO oxidation efficiency and NO x removal efficiency among the three catalysts. The presence of H2O caused a drop in the NO oxidation and the SCR activities. The SCR performance was significantly improved when Pt/Al2O3 and Cu/Al2O3 catalysts were employed sequentially in a reactor. The highest SCR performance was achieved using two separate stages: oxidation of NO by O2 over the Pt/Al2O3 catalyst followed by reduction of NO2 by NH3 over the Cu/Al2O3 catalyst. Under the condition with H2O, the two-stage catalyst system showed NO x removal efficiency over 80% at low temperatures below 200°C, which was the highest value among the catalyst systems used in this study. The physical and chemical properties of the catalysts were determined using nitrogen adsorption, XRD, TPR, and pulse CO chemisorption experiments. [Copyright &y& Elsevier]

Highlights: [•] Two-step catalysis of lignin dimer produced high carbon number cyclic hydrocarbons. [•] Isomerization of ether to alcohol without cracking was suggested. [•] Brönsted acids activated the catalytic isomerization of an α-O-4 compound. [•] NH3-TPD, pyridine-FT-IR, and NMR elucidated the active sites. [ABSTRACT FROM AUTHOR]