Rare earths, rare-earth oxides, and the ocides’ unique character: Application for environmental catalysts

The rare earths series will be comprehensively introduced. The difference among lanthanide, lanthanoid, and rare earths will be also clearly defined. After these lectures, the unique characteristics of rare-earth oxides will be addressed. As one of promising applications of the rare earth oxides, the oxides’ unique character of oxide anion migration in the solids will be also introduced and also for the application as the environmental catalysts. Here, we focused on C-type cubic Gd2O3, and Y2O3 which has relatively strong basicity among rare earth elements, as a fundamental oxide to develop a novel catalyst. The rare earth (R) sites in R2O3 are partially replaced by another rare earth ion and barium to effectively inhibit catalyst poisoning and effectively enhancing NO direct decomposition. Especially, (Y0.69Tb0.30Ba0.01)2O2.99+δ solid solution was succeeded in designing as the novel promising direct NO decomposition catalyst, showing a perfect NO decomposition into N2 and O2

The Reduction of Platinum Consumption in Environmental Catalysts for Complete Oxidation of Volatile Organic Compounds

Pt/Co3O4/CeO2-ZrO2-SnO2/-Al2O3 catalysts were successfully prepared by both conventional co-precipitation and impregnation methods. The catalytic performances for toluene oxidation on these materials indicate that the addition of Co3O4 to the Pt/CeO2-ZrO2-SnO2/-Al2O3 catalyst was significantly effective in reducing the platinum amount without further reduction in its activity. In fact, complete oxidation of toluene was realized by using the 1wt%Pt/11wt%Co3O4/16wt%Ce0.62Zr0.20Sn0.18O2.0/-Al2O3 catalyst at the temperature as low as 160 °C, which was lower than that with the 5wt%Pt/-Al2O3 catalyst (170 °C). Since the oxidation activities of both 1wt%Pt/16wt%Ce0.62Zr0.20Sn0.18O2.0/-Al2O3 and 1wt%Pt/11wt% Co3O4/-Al2O3 were below compared to that of the present 1wt%Pt/11wt%Co3O4/16wt%Ce0.62Zr0.20Sn0.18O2.0/-Al2O3, the main reason for the high toluene oxidation activity in the 1wt%Pt/11wt%Co3O4/16wt%Ce0.62Zr0.20Sn0.18O2.0/-Al2O3 catalyst can be ascribed to the concerted effect of Pt, Co3O4, and Ce0.62Zr0.20Sn0.18O2.0 on -Al2O3. In addition, novel type of refractory and noble Pt metal-free 17wt%La1−xCaxCoO3−x/2/Ce0.76Zr0.19Zn0.05O1.95 (0 ≤ x ≤ 0.15) catalysts was also tested for complete toluene oxidation. The composition was optimized to obtain the optimum toluene oxidation activity. Catalytic tests for toluene oxidation and characterization of oxygen release/storage properties of these materials suggest that the Ca2+ addition in the LaCoO3 lattice was appreciably effective in the enhancement of the toluene oxidation even after high-temperature treatment as high as around 1400 °C. In fact, complete oxidation of toluene was realized at 320 °C by using the 17wt%La0.9Ca0.1CoO2.95/Ce0.76Zr0.19Zn0.05O1.95 catalyst treated at 1400 °C. La0.9Ca0.1CoO2.95 oxide on the Ce0.76Zr0.19Zn0.05O1.95 support promoted toluene oxidation without using any precious platinum metal, and, therefore, the present catalyst has an advanced potential as the novel toluene oxidation catalyst

Novel calcium ion conducting solid electrolyte with NASICON-type structure

Divalent calcium ion conducting solid electrolyte with a three dimensional NASICON-type structure, (CaxHf1−x)4/(4−2x)Nb(PO4)31,was successfully prepared by introducing Ca2+ cations into the HfNb(PO4)3 solid. The existence of three kinds of high valence cation of Hf4+, Nb5+, and P5+ successfully realized the effective reduction of electrostatic interaction toward Ca2+ in the structure. The (Ca0.05Hf0.95)4/3.9Nb(PO4)3 solid possesses considerably higher Ca2+ cation conductivity and also lower activation energy compared with those of previously reported NASICON-type Ca0.5Zr2(PO4)32 solid. Please click Additional Files below to see the full abstract

Catalytic Liquid-Phase Oxidation of Phenolic Compounds Using Ceria-Zirconia Based Catalysts

Catalytic liquid-phase oxidation using a catalyst and oxygen gas (Catalytic wet air oxidation, CWAO) is one of the most promising technology to remove hazardous organic compounds in wastewater. Up to now, various heterogeneous catalysts have been reported for phenolic compounds decomposition. The CeO2-ZrO2 based catalysts have been recently studied, because CeO2-ZrO2 works as a promoter which supplies active oxygen species from inside the lattice to the active sites. Since it is difficult to dissolve oxygen gas into water, the use of the promoter is effective for realizing the high catalytic activity at moderate conditions. Also, CeO2-ZrO2 shows high resistance for the metal leaching during the catalytic reaction in the liquid-phase. This article reviews the studies of the catalytic liquid-phase oxidation of phenolic compounds using CeO2-ZrO2 based catalysts

Novel environment-friendly inorganic red pigments based on (Bi, Er, Y, Fe)2O3 solid solutions

Novel environmental-friendly inorganic red pigments, ((Bi0.72Er0.28−xYx)1−yFey)2O3 (0 < x ≤ 0.28, y = 0.20), were successfully synthesized using a conventional solid-state reaction method in order to further enhance the red hue of a ((Bi0.72Er0.28)0.80Fe0.20)2O3 pigment, which was previously reported by our group. The color of the samples depended on their composition and the most brilliant red hue was obtained for ((Bi0.72Er0.04Y0.24)0.80Fe0.20)2O3. The a* value corresponding to red chromaticity was +33.1 for ((Bi0.72Er0.04Y0.24)0.80Fe0.20)2O3, and it was greater than those of previously reported ((Bi0.72Er0.28)0.80Fe0.20)2O3 (a* = +30.9) and commercial Fe2O3 (a* = +28.9) pigments. Since the ((Bi0.72Er0.04Y0.24)0.80Fe0.20)2O3 pigment is composed of nontoxic elements (Bi, Er, Y, Fe, and O), it should be an attractive alternative to the conventional Fe2O3 pigments

Synthesis and characterization of divalent ion conductors with NASICON-type structures

Divalent ion-conducting solid electrolytes with NASICON-type three-dimensional network structures (MxHf1−x)4/(4−2x)Nb(PO4)3 (M = Ni, Mg, Ca, Sr) were successfully developed by introducing M2+ cations into HfNb(PO4)3 solids. The presence of high-valence cations such as Hf4+, Nb5+, and P5+ in the structures effectively reduced the electrostatic interaction between the conducting M2+ cations and the surrounding oxide anions, enabling the M2+ cations to migrate smoothly in the rigid crystal lattice. The relationship between the cation conductivity in NASICON-type solids and the ionic radius of the migrating divalent cation species was also clarified by taking into account the relative sizes of the conduction pathways in the structures