Showing papers on "Mixed oxide published in 2005"
TL;DR: The solubility of a range of metal oxides in a eutectic mixture of urea/choline chloride is quantified, and it is shown that the dissolved metals can be reclaimed from a mixed metal oxide matrix using electrodeposition.
Abstract: The solubility of a range of metal oxides in a eutectic mixture of urea/choline chloride is quantified, and it is shown that the dissolved metals can be reclaimed from a mixed metal oxide matrix using electrodeposition.
304 citations
TL;DR: In this paper, a series of nano-sized Ni/Al2O3 and Ni/La-Al 2O3 catalysts that possess high activities for NH3 decomposition have been successfully synthesized by coprecipitation method.
Abstract: A series of nano-sized Ni/Al2O3 and Ni/La-Al2O3 catalysts that possess high activities for NH3 decomposition have been successfully synthesized by a coprecipitation method. The catalytic performance was investigated under the atmospheric conditions and a significant enhancement in the activity after the introduction of La was observed. Aiming to study the influence of La promoter on the physicochemical properties, we characterized the catalysts by N-2 adsorption/desorption, XRD, H-2-TPR, chemisorption and TEM techniques. Physisorption results suggested a high specific surface area and XRD spectra showed that nickel particles are in a highly dispersed state. A combination of XRD, TEM and chemisorption showed that Ni-0 particles with the average size lower, than 5.0 nm are always obtained even though the Ni loading ranged widely from 4 to 63 %. Compared with the Ni/Al2O3 catalysts, the Ni/La-Al2O3 ones with an appropriate amount of promoter enjoy a more open mesoporous structure and higher dispersion of Ni. Reduction kinetic studies of prepared catalysts were investigated by temperature-programmed reduction (TPR) method and the fact that La additive partially destroyed the metastable Ni-Al mixed oxide phase was detailed. (c) 2005 Elsevier B.V. All rights reserved.
243 citations
TL;DR: The results show that under specific anodization conditions self-organized porous oxide structures can be grown on the alloy surface, and represent a simple surface treatment for Ti alloys that has high potential for biomedical applications.
Abstract: The present work reports the fabrication of self-organized porous oxide-nanotube layers on the biomedical titanium alloys Ti-6Al-7Nb and Ti-6Al-4V by a simple electrochemical treatment. These two-phase alloys were anodized in 1M (NH(4))(2)SO(4) electrolytes containing 0.5 wt % of NH(4)F. The results show that under specific anodization conditions self-organized porous oxide structures can be grown on the alloy surface. SEM images revealed that the porous layers consist of arrays of single nanotubes with a diameter of 100 nm and a spacing of 150 nm. For the V-containing alloy enhanced etching of the beta phase is observed, leading to selective dissolution and an inhomogeneous pore formation. For the Nb-containing alloy an almost ideal coverage of both phases is obtained. According to XPS measurements the tubes are a mixed oxide with an almost stoichiometric oxide composition, and can be grown to thicknesses of several hundreds of nanometers. These findings represent a simple surface treatment for Ti alloys that has high potential for biomedical applications.
239 citations
TL;DR: Reconstructed materials with small crystallites, produced by exfoliation during mechanical stirring, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity, and support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions.
Abstract: Two different rehydration procedures in the liquid or gas phase have been applied to reconstruct mixed oxides derived from calcined hydrotalcite-like materials to be used as catalysts for aldol condensation reactions. The as-synthesized hydrotalcite, its decomposition product, as well as the reconstructed solids upon rehydration were characterized by XRD, N(2) adsorption, He pycnometry, FTIR, SEM, TEM, (27)Al MAS-NMR and CO(2)-TPD (TPD=temperature-programmed desorption). Compared to the Mg-Al mixed oxide rehydrated in the gas phase (HT-rg), that rehydrated in the liquid phase (HT-rl) exhibits a superior catalytic performance with respect to the aldol condensation of citral with ketones to yield pseudoionones and in the self-aldolization of acetone. The textural properties of HT-rl and HT-rg differ strongly and determine the catalytic behavior. A memory effect led to a higher degree of reconstruction of the lamellar structure when the mixed oxide was rehydrated in the gas phase rather than in the liquid phase, although liquid-phase rehydration under fast stirring produced a surface area that was 26 times greater. This contrasts to typical statements in the literature claiming a higher degree of reconstruction in the presence of large amounts of water in the medium. CO(2)-TPD shows that the number of OH(-) groups and their nature are very similar in HT-rg and HT-rl, and cannot explain the markedly different catalytic behavior. Accordingly, only a small fraction of the available basic sites in the rehydrated samples is active in liquid-phase aldol condensations. Our results support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions. Based on this, reconstructed materials with small crystallites (produced by exfoliation during mechanical stirring), that is, possessing a high external surface area, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity.
211 citations
TL;DR: In this article, the effects brought about by the cerium salt precursor ((NH 4 ) 2 Ce(NO 3 ) 6 or Ce( NO 3 ) 3 ), the introduction of drying and aging steps as well as pH controlling upon precipitation were analyzed.
Abstract: The preparation of CeO 2 –ZrO 2 mixed oxides preparation was studied by evaluating the influence of several conditions Coprecipitation was taken as the standard method and the effects brought about by the cerium salt precursor ((NH 4 ) 2 Ce(NO 3 ) 6 or Ce(NO 3 ) 3 ), the introduction of drying and aging steps as well as pH controlling upon precipitation were analyzed The samples were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, infrared spectroscopy, oxygen storage capacity and surface area The use of Ce(NO 3 ) 3 leads to the formation of c -CeO 2 and t -ZrO 2 mixed oxide whereas a solid solution is achieved by using (NH 4 ) 2 Ce(NO 3 ) 6 It was observed that the cerium precursor is the most significant parameter of preparation procedure since it defines the crystalline phases and consequently the reducibility behavior of the CeO 2 –ZrO 2 system
172 citations
TL;DR: Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film.
Abstract: Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO42-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO42- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly...
164 citations
TL;DR: In this article, a mixed oxide consisting of TiO 2 as the major phase and CeO 2− y (0 y i -OC 3 H 7 ) 3 in an aqueous solution of Ce(NO 3 ) 3.
139 citations
TL;DR: In this article, a sol-gel route with propylene oxide as a gelation agent was used to synthesize mixed oxide nanoparticles, especially for that with one of metal ion having a formal charge of less than +3.
Abstract: Spinel nanoparticles of CoAl2O4 (blue), CoCr2O4 (bluish green), ZnFe2O4 (brown) and CuCr2O4 (black) were synthesized by a sol-gel route with propylene oxide as a gelation agent. This method has proven to be an effective route to synthesize mixed oxide nanoparticles, especially for that with one of metal ion having a formal charge of less than +3. Transmission electron micrographs show the small particle size (less than 60 nm) of the four pigments and their narrow particle size distributions.
132 citations
TL;DR: In this paper, a short-range ordered mesoporous structure with the nanoparticles (8nm) of TiO 2 dispersed uniformly on SiO 2 supports was obtained by a novel method in which hydrolysis and condensation of titanium tetraisopropoxide and tetraethoxysilane were controlled by the pH change of acidic solution using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent.
Abstract: Titania–silica mixed metal oxide materials with a mesostructure have been prepared by a novel method in which hydrolysis and condensation of titanium tetraisopropoxide (TTIP) and tetraethoxysilane (TEOS) were controlled by the pH change of acidic solution using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. The prepared materials were characterized by TEM, XRD, XPS, FT-IR and nitrogen sorption. The resulting materials showed a short-range ordered mesoporous structure with the nanoparticles (8 nm) of TiO 2 dispersed uniformly on SiO 2 supports. These TiO 2 –SiO 2 mesoporous materials were also found to have a higher photocatalytic activity than that of commercial pure TiO 2 nanoparticles at the same titanium loading for the degradation of methyl orange.
131 citations
TL;DR: In this paper, the homogeneous co-precipitation method was proposed to synthesize nanoscale binary mixed oxide ZnO-SnO2 in the presence of ethyl acetate.
120 citations
TL;DR: The catalytic activity of the surface metal oxide sites was found to decrease upon reduction of these sites and the most active surface sites were the fully oxidized surface cations, which reflected the chemical nature of surface active sites.
Abstract: CH3OH temperature programmed surface reaction (TPSR) spectroscopy was employed to determine the chemical nature of active surface sites for bulk mixed metal oxide catalysts. The CH3OH-TPSR spectra peak temperature, Tp, for model supported metal oxides and bulk, pure metal oxides was found to be sensitive to the specific surface metal oxide as well as its oxidation state. The catalytic activity of the surface metal oxide sites was found to decrease upon reduction of these sites and the most active surface sites were the fully oxidized surface cations. The surface V5+ sites were found to be more active than the surface Mo6+ sites, which in turn were significantly more active than the surface Nb5+ and Te4+ sites. Furthermore, the reaction products formed also reflected the chemical nature of surface active sites. Surface redox sites are able to liberate oxygen and yield H2CO, while surface acidic sites are not able to liberate oxygen, contain either H+ or oxygen vacancies, and produce CH3OCH3. Surface V5+, Mo6+, and Te4+ sites behave as redox sites, and surface Nb5+ sites are Lewis acid sites. This experimental information was used to determine the chemical nature of the different surface cations in bulk Mo-V-Te-Nb-Ox mixed oxide catalysts (Mo(0.6)V(1.5)Ox, Mo(1.0)V(0.5)Te(0.16)Ox, Mo(1.0)V(0.3)Te(0.16)Nb(0.12)Ox). The bulk Mo(0.6)V(1.5)Ox and Mo(1.0)V(0.5)Te(0.16)Ox mixed oxide catalytic characteristics were dominated by the catalytic properties of the surface V5+ redox sites. The surface enrichment of these bulk mixed oxide by surface V5+ is related to its high mobility, V5+ possesses the lowest Tammann temperature among the different oxide cations, and the lower surface free energy associated with the surface termination of V=O bonds. The quaternary bulk Mo(1.0)V(0.3)Te(0.16)Nb(0.12)Ox mixed oxide possessed both surface redox and acidic sites. The surface redox sites reflect the characteristics of surface V5+ and the surface acidic sites reflect the properties normally associated with supported Mo6+. The major roles of Nb5+ and Te4+ appear to be that of ligand promoters for the more active surface V and Mo sites. These reactivity trends for CH3OH ODH parallel the reactivity trends of propane ODH because of their similar rate-determining step involving cleavage of a C-H bond. This novel CH3OH-TPSR spectroscopic method is a universal method that has also been successfully applied to other bulk mixed metal oxide systems to determine the chemical nature of the active surface sites.
TL;DR: In this article, a heat treatment in H2 bearing gas was used to synthesize spinodally decomposed samples of mixed oxides and pure TiO2 and mixed oxide samples of SnO2 sintered with different surface areas.
Abstract: Pure TiO2 and mixed oxide samples of TiO2 and SnO2 sintered samples having different surface areas were synthesized using a heat treatment in H2 bearing gas. Nanostructures of solid solutions and spinodally-decomposed samples of mixed oxides were compared to the oriented nanofibers formed in pure TiO2 created by the same heat treatment. Comparisons between the sensing characteristics of the samples were made to determine that the samples with higher surface areas were more sensitive to H2 in the presence of O2.
TL;DR: In this paper, a fluorite type Ce-Zr-Co oxide, Ce 2 Zr 1.5 Co 0.5 O 8− δ, is studied for hydrogen production by steam reforming of ethanol/water mixture and bioethanol solution.
01 May 2005
TL;DR: Temperature-programmed reduction (TPR), oxidation (TPO), and desorption (TPD) studies were performed on three copper-ceria mixed oxide samples and reveal that despite a drastic initial drop in specific surface area after consecutive redox cycles, the hydrogen consumption remains constant.
Abstract: Temperature-programmed reduction (TPR), oxidation (TPO), and desorption (TPD) studies were performed on three copper-ceria mixed oxide samples having the same nominal composition, Cu0.15Ce0.85O(2-y), but prepared in three different ways: by co-precipitation, the sol-gel peroxide route, and the sol-gel citric acid route. The obtained results reveal that despite a drastic initial drop in specific surface area after consecutive redox cycles, the hydrogen consumption remains constant. This is because CuO is highly dispersed over the surface of CeO2 nanocrystallites and remains highly dispersed even after the agglomeration of CeO2 nanocrystallites in a denser secondary structure. The dispersed CuO is reduced to Cu(0) during the TPR, forming agglomerated metal particles on the surface of partially reduced CeO2. However, after subsequent temperature-programmed oxidation all the Cu(0) is oxidized back into CuO and redispersed over the CeO2 crystallites.
TL;DR: In this paper, the mechanism of eggshell-type Ni loading on Mg-Al mixed oxide particles has been carefully studied in connection with the structure of the mixed oxides as the catalyst supports.
TL;DR: The structural and electronic properties of Ti-W binary mixed oxide nanoparticles are investigated by usingX-ray diffraction, Raman, X-ray absorption spectroscopies (XAS), UV-vis spectroscopy, and density functional calculations.
Abstract: In this article, the structural and electronic properties of Ti−W binary mixed oxide nanoparticles are investigated by using X-ray diffraction, Raman, X-ray absorption spectroscopies (XAS; near edge XANES and extended EXAFS), UV−vis spectroscopy, and density functional calculations. A series of Ti−W binary oxide samples having W content below 20 atom % and with particle size between 8 and 13 nm were prepared by a microemulsion method. The atoms in these nanoparticles adopted the anatase-type structure with a/b lattice constants rather similar to those of the single TiO2 reference and with a c cell parameter showing a noticeable expansion upon doping. Within the anatase structure, W occupies substitutional positions, while Ti atoms only suffer minor structural perturbations. A change in the W local order at first neighboring distance is observed when comparing samples having a W content below and above 15 atom %. Charge neutrality is mostly achieved by formation of cation vacancies located at the first cat...
TL;DR: In this article, the effect of modification with cobalt of a series of LaFe 1-x Co x O 3 mixed-oxide perovskites as catalyst precursors in the combined reforming of methane with CO 2 and O 2 for the production of syngas was investigated.
TL;DR: In this paper, the preparation of nanostructured mixed metal oxide based on a sol-gel method with surfactant-assisted mechanism, and its application for dye-sensitized solar cell (DSSC) are reported.
TL;DR: In this article, the Guerbet condensation was used for the synthesis of isobutyl alcohol from methanol (MeOH) and n -propanol (PrOH) through batch experiments using bifunctional heterogeneous systems.
Abstract: The synthesis of isobutyl alcohol ( i BuOH) from methanol (MeOH) and n -propanol (PrOH) through the Guerbet condensation has been studied in batch experiments using bifunctional heterogeneous systems based on a dehydrogenating/hydrogenating metal (Pd, Rh, Ni or Cu) and a basic Mg–Al mixed oxide derived from hydrotalcite-type (HT) precursors. Only copper-based systems showed appreciable performances. In particular, the Cu/Mg/Al mixed oxides catalysts obtained by the co-precipitation method offered the best results in terms of activity and selectivity, thus allowing to reduce pollution problems connected with the up to now adopted copper chromite. These co-precipitated systems were also tested in some preliminary experiments carried out in gas–solid phase in a flow reactor, thus confirming promising application perspectives.
TL;DR: Alumina-zirconia mixed oxide-supported sulfate-, molybdate- and tungstate-promoted solid acid catalysts were synthesized and characterized by various techniques as discussed by the authors.
Abstract: Alumina–zirconia mixed oxide-supported sulfate-, molybdate- and tungstate-promoted solid acid catalysts were synthesized and characterized by various techniques. The Al–Zr hydroxide gel was obtained by a co-precipitation method from their corresponding nitrate salts by hydrolysis with aqueous ammonia. To the Al–Zr-hydrous mixed oxide support, aqueous solutions of sulfuric acid, ammonium heptamolybdate and ammonium metatungstate were added and the mixtures were refluxed at 110 °C, followed by evaporation of the water, drying and calcination at 650–750 °C. The surface and bulk properties of the catalysts were examined by using X-ray diffraction, BET surface area, TGA/DTA, ammonia-TPD and XPS techniques. The XRD results reveal that Al2O3–ZrO2 mixed oxide calcined at 650 °C is in amorphous or poorly crystalline state exhibiting broad diffraction lines due to tetragonal ZrO2 phase. At 750 °C calcination, a better crystallization of the zirconia tetragonal phase is observed. The XRD results further indicate that incorporation of alumina into zirconia stabilizes the tetragonal phase. The TGA–DTA studies provide information that there are at least two types of sulfate species with different thermal stabilities in the case of SO42−/Al2O3–ZrO2 catalyst. The TPD study reveals that the SO42−/Al2O3–ZrO2 catalyst exhibits an ammonia desorption peak maximum at 600 °C indicating super-acidic nature of the catalyst. The XPS peak intensities and the corresponding binding energies indicate that sulfate ion interacts with the support more strongly than other promoters. All characterization results provide information that the impregnated sulfate ions show a relatively strong influence on the physicochemical properties of the Al2O3–ZrO2 mixed oxide. The prepared catalysts were evaluated for acetylation of alcohols and amines with acetic anhydride in the liquid phase. In line with physicochemical characteristics, the SO42−/Al2O3–ZrO2 exhibits better product yields under very mild reaction conditions.
TL;DR: Binary and ternary mixed oxide of Y/Fe/Ti with homogeneous distribution of yttrium and iron oxides into TiO 2 has been prepared by sol-gel method using metal alkoxide precursors in presence of acid base catalysts as mentioned in this paper.
Abstract: Binary and ternary mixed oxide of Y/Fe/Ti with homogeneous distribution of yttrium and iron oxides into TiO 2 has been prepared by sol–gel method using metal alkoxide precursors in presence of acid–base catalysts The structural features of Y 2 O 3 /Fe 2 O 3 /TiO 2 mixed oxide fired at 550 °C have been investigated by XRD, FT-IR, SEM, AFM, XPS and surface area measurements A preliminary investigation of photocatalytic activity of mixed oxide on EDTA photo-oxidation showed that Y/Fe/Ti is more photoactive than pure TiO 2
Patent•
23 Mar 2005
TL;DR: In this paper, a nitrogen oxide storage material based on storage compounds of elements selected from the group consisting of magnesium, calcium, strontium, barium, the alkali metals, the rare earth metals and mixtures thereof is described.
Abstract: A nitrogen oxide storage material which is based on storage compounds of elements selected from the group consisting of magnesium, calcium, strontium, barium, the alkali metals, the rare earth metals and mixtures thereof and has a homogeneous magnesium-aluminium mixed oxide doped with cerium oxide as support material for the storage compounds is described. Nitrogen oxide storage catalysts using this storage material display a broad working range, a high storage efficiency and good ageing resistance.
TL;DR: In this paper, a black pigment consisting of mixed manganese, copper and iron oxides was tested as a catalyst as well as an oxidant for CO oxidation and the results showed that the mixture of mixed oxides of transition metals can be a viable alternative to precious metal and noble metal containing catalysts for oxidation of CO.
Abstract: Commercially available black pigment consisting of mixed manganese, copper and iron oxides was tested as a catalyst as well as an oxidant for CO oxidation. The crystalline structures of the catalyst were determined by XRD as Cu 1.5 Mn 1.5 O 4 mixed with Fe 2 O 3 and Mn 3 O 4 oxides. The fresh catalyst with 30–300 nm size and a BET surface area of 18.5 m 2 g −1 was able to completely convert CO at 525 °C even at a significantly high CO O 2 He gas flow rate of 1000 ml min −1 (corresponding space velocity being ∼310,000 h −1 ). While the reaction rate was independent of oxygen concentration in the range tested (0.8–9.9 vol.% of O 2 at a constant CO concentration of 0.85%), it depended on CO concentration. The reaction order over fresh catalyst was measured to be 0.85 with respect to CO with an activation energy value of 47.9 kJ mol −1 . Application of a reduction followed by oxidation type of heat treatment on fresh catalyst induced the formation of fine clusters or domains of ∼5 nm on the surface of the catalyst particles. This refined morphology with high density of defects led to a great improvement in catalytic activity. Complete CO conversion was achieved at 180 °C over a heat treated catalyst. This change in morphology also led to higher reducibility of mixed oxide system after heat treatment as indicated by TPR results. The mixed oxides of transition metals can be a viable alternative to precious metal and noble metal containing catalysts for oxidation of CO.
TL;DR: In this article, high-homogeneous (Ce,Tb) oxides are prepared by a micro-emulsion technique, and their structural and electronic state after high temperature calcination is examined with X-ray diffraction, high resolution transmission electron microscopy, X -ray photoelectron and absorption (XANES) spectroscopies and impedance spectroscopy measurements.
TL;DR: In this article, a novel synthetic strategy for preparing bimetallic Ru-M (M = Cr, Fe, Co, Ni and Cu) catalysts, supported on Mg-Al mixed oxide, has been introduced.
Abstract: A novel synthetic strategy for preparing bimetallic Ru–M (M = Cr, Fe, Co, Ni and Cu) catalysts, supported on Mg–Al mixed oxide, has been introduced. It was based on a “memory effect”, i.e. on the ability of Mg–Al mixed oxide to reconstruct a layered structure upon rehydration with an aqueous solution. By repeated calcinations–rehydration cycles, layered double hydroxide (LDH) precursors of catalysts containing two different metals were synthesized. Bimetallic catalysts were then generated (i) in situ from LDH under methane reforming reaction conditions and (ii) from mixed metal oxides obtained by preliminary LDH calcination. Among all the LDH-derived catalysts, a Ru 0.1% –Ni 5.0% /MgAlO x sample revealed the highest activity and selectivity to syngas, a suitable durability and a low coking capacity. A promoting effect of ruthenium on catalytic function of supported nickel was demonstrated. Preliminary LDH calcination was shown to markedly affect the catalytic activity of the derived catalysts and especially their coking properties.
TL;DR: The value of DeltaH degrees and DeltaG degrees prove that the sorption of strontium on mixed oxide gel is an endothermic and a spontaneous process.
TL;DR: In this article, Magnesium-lanthanum mixed oxide, a strong solid base, was used for adding Michael additions to super bases at room temperature with a broad spectrum of acceptors and donors.
Abstract: Michael additions were achieved quantitatively at room temperature with a broad spectrum of acceptors and donors, using a magnesium-lanthanum mixed oxide, a strong solid base. The best solvent for the reaction is dimethylformamide, but good yields were also obtained using toluene as solvent. The results obtained with magnesium-lanthanum are comparable to those reported for super bases. The catalyst can be separated from the reaction mixture and recycled five times without loss of activity with no other treatment.
TL;DR: In this paper, cobalt and lead based mixed oxide catalysts were tested for their soot oxidation ability in addition to a mixed oxide formerly marketed as ceramic paint, a home made set was also prepared by incipient wetness impregnation of a cobalt oxide powder with a lead acetate solution and subsequent calcination.
Abstract: In this study, cobalt and lead based mixed oxide catalysts were tested for their soot oxidation ability In addition to a mixed oxide formerly marketed as ceramic paint, a home made set was also prepared by incipient wetness impregnation of a cobalt oxide powder with a lead acetate solution and subsequent calcination The materials investigated in this study were shown to decrease the peak combustion temperature of home made soot from 500 to 385 °C in air Soot oxidation tests under inert (N2) atmospheres revealed that the oxidation took place by using the lattice oxygen of the catalyst Reaction temperature could be further decreased when these mixed oxide catalysts were impregnated with platinum An optimum platinum loading was determined as 05 wt% based on the peak combustion temperature of the soot The role of Pt was to assist the oxygen transfer from the gas phase to the lattice It was observed that NO2 is a better oxidizing agent as compared to air whereas NO had hardly any activity against soot oxidation reaction When the mixed oxide catalyst was impregnated with platinum, the peak combustion temperature was measured as 310 °C in the presence of NOx and air The catalyst's unique performance was in terms of the rate of soot oxidation Under the experimental conditions studied here, the soot oxidation was so facile that the oxygen in the gas phase was completely depleted This stream of oxygen depleted and CO enriched gas phase can be used to reduce NOx in the presence of a downstream or a co-catalyst
TL;DR: In this article, a porous oxide semiconductor material made of a titanium-niobium oxide was evaluated as a heterogeneous photocatalyst for the photolysis of organic compounds in water.
TL;DR: Porous Mn−Cu and Mn− Cu−V mixed-oxide sorbents prepared by the complexation technique were tested for high-temperature removal of H2S in the presence of hydrogen gas as discussed by the authors.
Abstract: Porous Mn−Cu and Mn−Cu−V mixed-oxide sorbents prepared by the complexation technique were tested for high-temperature removal of H2S in the presence of hydrogen gas. Sorption experiments carried out at 627 °C in a fixed-bed reactor showed higher reactivity and also higher sulfur retention capacity (over 0.15 g of S/g of sorbent) for the Mn−Cu mixed oxide than for the Mn−Cu−V mixed oxide. Successive sulfidation−regeneration cycles demonstrated that the Mn−Cu mixed oxide was also more stable than Mn−Cu−V, maintaining its activity and about 90% of its sulfur retention capacity at the end of five cycles. Although formation of some MnSO4 was observed during regeneration at 700 °C with a gas mixture containing 6% oxygen in nitrogen, this did not cause significant reduction in the activity of this mixed-oxide sorbent. It was also shown that a previously proposed deactivation model gave good predictions of the experimental breakthrough curves obtained with these sorbents.