Showing papers on "Mixed oxide published in 1985"

Preparation of Vanadium–Phosphorus Mixed Oxide (P/V=1) Catalysts and Their Application to Oxidation of Butane to Maleic Anhydride

Abstract: Several vanadium–phosphorus mixed oxides with a P/V ratio=1 have been prepared and the relationships between the structure of catalyst and the catalytic function for the selective oxidation of butane to maleic anhydride were examined. As revealed from XRD, IR, XPS, and redox titration studies, five among them were presumably composed of crystalline single phases, that is, α-VOPO4, β-VOPO4, and (VO)2P2O7 as well as unknown phases X1 and X2. The valences of the vanadium of these catalysts were close to five, except for (VO)2P2O7 (the valence was four). These phases were prepared, respectively, by controlling the kind of precursors and the calcination conditions. The selectivity to maleic anhydride differed markedly among these catalysts, although the rate did not change much when it was normalized to surface area. The selectivity at 440 °C was less than 20% for α- and β-VOPO4, 40% for X1 and X2, and 70% for (VO)2P2O7. Amorphous phases having V4+ were much less selective than (VO)2P2O7. No structural changes...

High temperature regenerative H2 S sorbents

Abstract: Efficient, regenerable sorbents for removal of H 2 S from high temperature gas streams comprise porous, high surface area particles. A first class of sorbents comprise a thin film of binary oxides that form a eutectic at the temperature of the gas stream coated onto a porous, high surface area refractory support. The binary oxides are a mixture of a Group VB or VIB metal oxide with a Group IB, IIB or VIII metal oxide such as a film of V-Zn-O, V-Cu-O, Cu-Mo-O, Zn-Mo-O or Fe-Mo-O coated on an alumina support. A second class of sorbents consist of particles of unsupported mixed oxides in the form of highly dispersed solid solutions of solid compounds characterized by small crystallite size, high porosity and relatively high surface area. The mixed oxide sorbents contain one Group IB, IIB or VIIB metal oxide such as copper, zinc or manganese and one or more oxides of Groups IIIA, VIB or VII such as aluminum, iron or molybdenum. The presence of iron or aluminum maintains the Group IB, IIB or VIIB metal in its oxidized state. Presence of molybdenum results in eutectic formation at sulfidation temperature and improves the efficiency of the sorbent.

X-ray absorption spectroscopy study of copper-based methanol catalysts. 1. Calcined state

Abstract: X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), and electron microscopy (TEM and AEM) have been used to elucidate the structure of binary Cu-Zn and ternary Cu-Zn-Al methanol catalysts in the calcined state. The XRD and TEM results did not show any features which could be assigned to a Cu phase and this indicates that these atoms are present in amorphous-like or microcrystalline structures. From a detailed study of the Cu and Zn absorption K-edges, information about the chemical state of Cu and Zn has been obtained, and the local structural geometry around the atoms has been elucidated by studying the extended X-ray absorption fine structure (EXAFS) above the absorption edges. These studies reveal that copper in both the binary and ternary catalysts is present as Cu/sup 2 +/ but with local environment somewhat different from that of copper in well-crystallized CuO. In contrast to the binary catalysts, which show the presence of small particles of well-defined ZnO, the ternary catalysts are found to contain zinc in microcrystalline or amorphous-like structures. The EXAFS results suggest that Zn/sup 2 +/ forms a mixed oxide phase with Cu/sup 2 +/ and this phase may also contain aluminum. The presence of such a phasemore » is in accordance with the analytical electron microscopy (AEM) results which show that Cu, Zn, and Al are homogeneously distributed in these catalysts. 19 references, 7 figures, 4 tables.« less

Hydrolytic stripping of single and mixed metal: versatic solutions

Abstract: Hydrolytic stripping is the process whereby metal ions in a loaded solvent extractant are directly precipitated as oxides or hydroxides by hydrolysis with water, typically at 130° to 200 °C. Hydrolytic stripping tests were carried out in sealed tubes at 200 °C on Versatic 10 solutions of Mg, Ca, Sr, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Cd, singly and in mixtures. Single solutions of Fe, Ni, Cu, Mg, and Mn precipitated αFe2O3, Ni(OH)2, CuO + Cu2O, Mg(OH)2, and γMn2O3, respectively, during testing. Several mixtures of iron with other metals precipitated magnetic spinel ferrites, MFe2O4. No other combinations of metals formed crystallographically distinctive mixed oxides.

EFFECT OF Nb2O5 ADDITION ON THE CATALYTIC ACTIVITY OF FeOx FOR REDUCTION OF NOx WITH NH3 AND O2

Abstract: Niobium oxide, Nb2O5, remarkably enhanced the catalytic activity of FeOx for the reduction of NOx with NH3 and O2. Thus, for the reduction catalyzed by FeOx containing a small amount of Nb2O5, the conversion attained 90–100% in contrast to less than 40% for the reduction catalyzed by FeO without Nb2O5. The catalytic activity of the mixed oxide was scarcely affected by addition of SO2 to the reaction gas.

Mixed-oxide catalysts for the metathesis of functionalized alkenes

Abstract: Low-rhenium-loading Re2O7/Al2O3–MR4(M = Sn or Pb; R = Me, Et, or Bu) catalysts show good activity at room temperature (293 ± 2 K) for the metathesis of functionalized alkenes, such as unsaturated esters, when they are modified with MoO3, V2O5, or WO3.

Reducible metal oxide compositions containing zirconium oxide, yttrium oxide and an alkali metal component

Abstract: A class of mixed oxide catalysts comprising at least one reducible metal oxide, which oxide produces higher hydrocarbons and water when contacted with a hydrocarbon at synthesizing conditions, at least one oxide of zirconium, and at least one oxide of yttrium. The compositions are useful for hydrocarbon conversion, methane conversion, and oxidative dehydrogenation processes characterized by the formation of coproduct water.

Low Temperature Synthesis of Liquid Hydrocarbons from Syngas on Composite Catalysts of Pd-doped Cu-Cr-Zn Mixed Oxides and an H-ZSM-5 Zeolite

Abstract: Synthesis of liquid hydrocarbons from syngas was studied at relatively low temperatures, below 300°C, using bifunctional composite catalysts composed of low-temperature type methanol-synthesis catalysts of Pd-doped Cu-Cr-Zn mixed oxides and an H-ZSM-5 zeolite. As a source of Zn component of the methanol synthesis catalyst, freshly prepared Zn(OH)2 from Zn(NO3)2 was more suitable than a commercial ZnO powder for higher hydrocarbon yields. Oxidation and succesive reduction (O-R) treatments of the composite catalysts were carried out at 400°C and in the range of from 400 to 800°C. When the reduction temperature of O-R treatment was 600°C, the performance of the composite catalysts was appreciably improved. Syngas (H2/CO=2) was converted to hydrocarbons, dimethyl ether, and CO2 with selectivities of 44.1, 1.4, and 54.5%, respectively, at 35.8% CO conversion at 290°C, 20atm, and 6, 000 hourly space velocity. The space-time conversion of CO to liquid hydrocarbons (C4-C11) and the corresponding selectivity were 9.5mol/l•h and 61.4%, respectively. By lowering the H2/CO ratio of syngas from 2 to 1, the liquid hydrocarbon selectivity increased to 68.4% whereas the space-time conversion of CO to liquid hydrocarbon decreased.

Support tubes for electrochemical cells

Abstract: Compounds having a fluorite-like structure comprising a solid solution having the general formula ; where MOs is calcia, yttria, a rare earth oxide, or mixtures thereof, x is from 0.1 to 0.3, y is from 0.005 to 0.06, z is from 0.1 to 1.9, A is yttrium, a rare earth element, an alkaline earth element, or mixture thereof, B is iron, nickel, cobalt, or mixtures thereof, m is 0.3 to 1, n is 0.5 to 1, and r is 2 to 4. A porous tube made from such compositions can be coated with an electrically conducting mixed oxide electrode such as lanthanum manganite, and can be used in making high temperature electro-chemical cells such as solid electrolyte fuel cells.

Gel precursor for tin oxide material

Abstract: A process for the preparation of a tin oxide material includes gelling a dispersion containing finely divided tin oxide and a colloidal component (e.g. tin oxide or zirconia sol) thereby to form a gel. The gel may be treated further to give the tin oxide material (e.g. by heating). The tin oxide material may be tin oxide as such, or a mixed oxide material containing tin oxide and an oxide of another element.

Metal Alkoxy-Derived Powders

Abstract: The use of metal alkoxides to prepare high purity oxide powders is emphasized. Thermal and hydrolytic decomposition of metal alkoxides, M(OR)n, have been employed to obtain submicron size <50nm single and mixed oxides powders. The alkoxy technique in powder synthesis allow the mixing of residual concentration of an alloying element to be done at something approaching the molecular level. The high surface activity associated with the alkoxy-derived powders make possible relatively low temperature processing of the powder compact to near theoretical density and uniform fine grain size bodies. Transmission electron microscopy, X-ray, ir, DTA and BET surface area measurement are used to show nucleation, crystallite growth and morphology as well as polymorphs of the oxide powder synthesized and microstructural features observed.

Mössbauer and related studies on the formation of some mixed oxide catalysts of iron and cobalt

Abstract: A series of mixed oxides and ferrites of iron and cobalt has been prepared by taking iron and cobalt in the atomic ratio 1∶0.50, 1∶1.33 and 1∶3.00, respectively. These samples were prepared by calcination of the stoichiometric amount of their respective nitrate salts for 6 h in air at 500±10°C. Characterization of the samples has been carried out using Mossbauer spectroscopy. Percentage formation of α-Fe2O3 and CoFe2O4 has been determined using the same technique. These results have been supplemented by X-ray diffraction studies. The particle size has been calculated using Scanning Electron Microscopy. the decomposition of 0.5% w/v hydrogen peroxide at 40°C over the catalyst has also been studied.

Manufacture of thin film thermistor

Abstract: PURPOSE:To reduce condensation of Au-Pt electrode film and to improve thermal stability at the contact part between an SiC thin film and the Au-Pt electrode film by using the Au-Pt electrode film where the mixture of a Ca oxide and a Ti oxide is added slightly. CONSTITUTION:A pair of Au-Pt calcination electrode film 22 of a specified shape and an SiC sputter resistance thin film 23 are formed on an insulation substrate 21 and a small amount of a mixed oxide of a Ca oxide and a Ti oxide is added into this Au-Pt calcination electrode film 22 slightly. When the Au-Pt calcination electrode film 22 including a small amount of oxide is used, it becomes difficult for condensation even at a high temperature of 500 deg.C to proceed. Thus, it becomes possible to obtain a practical SiC thin film thermistor 1 which can operate for a long time even at a high temperature of 500 deg.C.

Catalyst containing oxide mixture of vanadium, phosphorus and aluminum and/or boron

Abstract: A mixed oxide catalyst precursor comprising vanadium and phosphorus treated in finely divided form with phosphoric acid and water soluble compound of aluminum and/or boron to improve resistance to attrition