Search

Novel ZrSn1−xCoxO4−δ catalysts for the direct decomposition of nitrous oxide (N2O) were synthesized using a co‐precipitation method. Metastable ZrSnO4 with an α‐PbO2‐type structure was used as the mother solid because of its interstitial open spaces derived from its lattice distortion that may be effective for N2O adsorption. The doping of Co2+/3+ into the ZrSnO4 lattice improved the N2O decomposition activity, likely owing to the enhancement of the redox properties and the increase in the number of oxygen vacancies. Among the prepared catalysts, Zr1.17Sn0.73Co0.10O4−δ exhibited the highest activity decomposing N2O completely decomposed at 550°C. In addition, the Zr1.17Sn0.73Co0.10O4−δ catalyst showed high durability in the presence of CO2, O2, and H2O vapor. [ABSTRACT FROM AUTHOR]

Effective glyceric acid production from glycerol was demonstrated under mild conditions in an open-air system at room temperature in the absence of base or oxygen gas flow by employing a Pt/CeO2–ZrO2–Fe2O3/Santa Barbara Amorphous No. 16 (SBA-16) catalyst. At a low loading amount of CeO2–ZrO2–Fe2O3 (16 wt%Ce0.64Zr0.16Fe0.20O2−δ/SBA-16), the oxygen release and storage abilities and high acidity of the catalyst afforded a high glyceraldehyde yield, owing to the enhancement of the oxidation ability of the Pt activator and the acceleration of the desorption of glyceraldehyde. The increase in CeO2–ZrO2–Fe2O3 loading amount further improved the oxygen release and storage abilities and lowered the catalyst acidity induced by crystallite growth and particle aggregation. The high oxygen release and storage abilities, as well as the low acidity, contributed to the high glyceric acid yield; the highest activity for glyceric acid production was obtained for the 7 wt%Pt/40 wt%Ce0.64Zr0.16Fe0.20O2−δ/SBA-16 catalyst. The glyceric acid yield increased up to 68.2% after 10 h of reaction in atmospheric air at 30°C. [ABSTRACT FROM AUTHOR]

Novel catalysts of Pt/La1−xBixOF/SBA‐16 (SBA‐16: Santa Barbara Amorphous No. 16) were synthesized, and their catalytic activities for phenol decomposition in the liquid phase were investigated. Lanthanum oxyfluoride (LaOF) was selected as the promoter due to its contribution to the smooth migration of oxygen species in the lattice and the acceleration of phenol adsorption on the catalyst surface. Reducible Bi3+ ions were introduced in the LaOF lattice to provide oxygen supply ability to LaOF. Among the prepared catalysts, the highest activity was obtained for the 7 wt% Pt/16 wt% La0.99Bi0.01OF/SBA‐16 catalyst, which could remove 97% of phenol after 5 h of reaction at 80°C in an open‐air atmosphere. [ABSTRACT FROM AUTHOR]

The size effect of the ZrO2 support on the catalytic activity for the liquid-phase oxidation of phenol was demonstrated over Pt/CeO2-ZrO2-Bi2O3/ZrO2-X catalysts. Here, we selected six types of size-controlled ZrO2-X (X: A–F) (ZrO2-A: 35 nm, ZrO2-B: 22 nm, ZrO2-C: 14 nm, ZrO2-D: 11 nm, ZrO2-E: 9 nm, and ZrO2-F: 2 nm). The surface area of the ZrO2-X support was inversely proportional to the particle size of ZrO2. ZrO2-X (X: A–E) were crystalline phases, while ZrO2-F was amorphous phase. For Pt/CeO2-ZrO2-Bi2O3/ZrO2-X (X: A–E) catalysts, the smaller particle size of the crystalline ZrO2 (X: A–E) support resulted in a larger catalyst surface area, which in turn led to enhanced oxygen release and storage abilities of the CeO2-ZrO2-Bi2O3 promoter, and allowed for the oxidation of Pt0 to Pt2+ with high activity. The highest activity was obtained for the Pt/CeO2-ZrO2-Bi2O3/ZrO2-E catalyst, which had the largest surface area and the highest oxygen release and storage abilities; phenol was completely removed after a reaction time of 10 h at 80°C under atmospheric pressure (0.1 MPa). [ABSTRACT FROM AUTHOR]

The effect of oxygen vacancies on catalytic activity for direct N2O decomposition was demonstrated in Zr1−xYxO2−δ solid solutions with a fluorite-related structure. The fluorite-type structure was formed as samples with a small amount of Y3+ (0.05 ≤ x ≤ 0.19) and a large amount of Y3+ (x ≥ 0.80), leading to the generation of a C-type structure derived from the fluorite-type structure by removing a quarter of the oxide anions. The oxygen vacancies worked as N2O adsorption sites and catalytic active sites, with the highest activity realized by the YO1.5 catalyst with a C-type structure, which contained the largest number of oxygen vacancies in the ZrO2-Y2O3 system. [ABSTRACT FROM AUTHOR]

A Pt/CeO2-ZrO2-SnO2/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalyst was developed for the efficient removal of 1,4-dioxane. Because the catalyst showed synergistic action between the high catalytic activity of Pt and the high oxygen release and storage abilities of CeO2-ZrO2-SnO2, high catalytic efficiency in the liquid phase was obtained in an air atmosphere without the supply of any strongly oxidizing additives or photoirradiation. After reaction at 80°C for 4 h, the residual percentage of 1,4-dioxane reached 31%. Furthermore, the Pt/CeO2-ZrO2-SnO2/SBA-16 catalyst exhibited high reusability and durability and the rate of net decrease in 1,4-dioxane reached 44% at 80°C. [ABSTRACT FROM AUTHOR]

Abstract: Direct decomposition of nitrogen oxides (NO x ), which are the main air pollutants responsible for photochemical smog and acid rain, into N2 and O2 (2NO→N2 +O2) offers the most ideal route for NO x removal by catalysis. Direct decomposition of NO x is versatile and economic because no reductants are required. However, the catalytic activities of conventional catalysts are insufficient, particularly in the presence of other gases such as O2 and CO2. In recent years, however, investigation of different catalyst structures and compositions has led to enhanced catalytic activity. In particular, significant advances have been made in improving the tolerance of the catalyst to coexisting gases. These direct NO decomposition catalysts have been designed with a view to maximizing the cavity space and number of oxide anion vacancies in the crystal lattice. In this review article, recent advances in the direct NO decomposition catalysts are summarized. [Copyright &y& Elsevier]

Catalytic combustion of methane was investigated on Pt and PdO-supported CeO-ZrO-BiO/γ-AlO catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and BET specific surface area measurements. The Pt/CeO-ZrO-BiO/γ-AlO and PdO/CeO-ZrO-BiO/γ-AlO catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO, CO, and H were obtained. The catalytic activities of the PdO/CeO-ZrO-BiO/γ-AlO catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd into PdO based on lattice oxygen supplied from the CeO-ZrO-BiO bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO-ZrO-BiO/γ-AlO catalyst prepared at 400 °C. [ABSTRACT FROM AUTHOR]

Pt/CeO2-ZrO2-Bi2O3-PbO/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalysts were synthesized to produce hydroxypyruvic acid by glycerol oxidation. In the catalysts, the introduction of PbO into CeO2-ZrO2-Bi2O3 improved the oxygen release and storage abilities owing to the synergistic redox reaction of Pb2+/4+ and Ce3+/4+, which facilitated the oxidation ability of Pt. In addition, the oxidation of the secondary OH group in glycerol might be accelerated by the geometric effects of glycerol, Pt, and Bi3+ or Pb2+/4+. Furthermore, the moderate reaction conditions such as room temperature and open-air atmosphere enabled the suppression of further oxidation of hydroxypyruvic acid. The highest catalytic activity was obtained for 7 wt% Pt/16 wt% Ce0.60Zr0.15Bi0.20Pb0.05O2−δ/SBA-16, which provided a hydroxypyruvic acid yield maximum of 24.6%, after the reaction for 6 h at 30 °C in atmospheric air. [ABSTRACT FROM AUTHOR]

A novel Pt/CeO2–ZrO2–Bi2O3catalyst was prepared to realize complete CO oxidation at room temperature or below even in the presence of moisture. Using this catalyst, a high CO oxidation activity and a high stability against moisture have been realized simultaneously. [ABSTRACT FROM AUTHOR]

A Pt/Ce0:64Zr0:16Bi0:20O1:90/γ-Al2O3 catalyst was prepared in order to establish complete oxidation of ethylene at temperatures below 100°C. Ethylene was completely oxidized over the catalyst as low as at 65°C, while over Pt/γ-Al2O3, which has been well known as an active oxidation catalyst, complete oxidation was achieved at 145°C. [ABSTRACT FROM AUTHOR]

Excellent oxidation catalysts, which can completely oxidize volatile organic compounds (VOCs) and methane at moderate temperatures, have been prepared. A new concept based on the design of solid electrolytes has been applied to the preparation of the catalysts. By the synergetic effect of precious metals and rare earth oxides, complete oxidation of VOCs and methane into CO2 and steam at moderate temperatures has been realized for the present catalysts. [ABSTRACT FROM AUTHOR]

C-type cubic (Y0.99-xTbxBa0.01)2O2.99+δ (0 ≤ x le; 0.4) catalysts were prepared by coprecipitation. The NO decomposition activities at 1173 K were higher than that of (Gd0.7Y0.26Ba0.04)2O2.96 reported previously. The highest catalytic activity was obtained for (Y0.69Tb0.3Ba0.01)2O2.99+δ, and 100% NO conversion into N2 and O2 was realized at 1173 K on this catalyst. Furthermore, the conversion ratio was maintained as high as 70.8% even in the presence of 5 vol % oxygen. [ABSTRACT FROM AUTHOR]

• Novel Pt/CeO 2 -ZrO 2 -Fe 2 O 3 /SBA-16 were developed for glycerol oxidation. • Fe 2 O 3 doping into CeO 2 -ZrO 2 /SBA-16 improved oxygen release and storage abilities. • High glyceraldehyde yield was obtained around room temperature in open air system. Pt/CeO 2 -ZrO 2 -Fe 2 O 3 /SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalysts were prepared to produce glyceraldehyde (GLA) from glycerol effectively at around room temperature in an open air system. By introducing Fe3+ ion into CeO 2 -ZrO 2 , the oxygen release and storage abilities were improved, which led to the high oxidation ability of Pt. The highest activity was obtained for 6.7 wt%Pt/15.3 wt%Ce 0.64 Zr 0.15 Fe 0.21 O 2− δ /SBA-16, and the GLA yield reached up to 22.1% under the moderate condition of 30 °C for 4 h in an open air atmosphere. [ABSTRACT FROM AUTHOR]

Pt/CeO 2 –ZrO 2 –SnO 2 /γ-Al 2 O 3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO 2 –ZrO 2 –SnO 2 were successfully dispersed on the γ-Al 2 O 3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4 wt.%)/Ce 0.68 Zr 0.17 Sn 0.15 O 2.0 (16 wt.%)/γ-Al 2 O 3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8 hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4 hr and longer. [ABSTRACT FROM AUTHOR]