Showing papers on "Mixed oxide published in 1980"

Catalysis by mixed oxide perovskites. I. Hydrogenolysis of ethylene and ethane on LaCoO3.

Abstract: Catalysis by a mixed oxide with a perovskite structure, LaCoO3, was studied for the hydrogenolysis of ethylene and ethane at temperatures 300–600 K using the hydrogen-excess mixtures. The high and stable activity was obtained by evacuating LaCoO3 at 600 K. Ethylene hydrogenolysis above 420 K proceeded consecutively via the intermediate, ethane, to produce methane, whereas only the hydrogenation to form ethane occurred below 420 K. Different temperature dependence of the rate was observed, i.e., the activation energy of −19.3 kJ·mol−1 in the range 420–600 K and 33.6 kJ·mol−1 in the range 300–420 K. The mechanistic analysis and tracer study using D2 showed that the slow step of the hydrogenation shifts, with increasing temperature, from the adsorption of hydrogen to the surface reaction between hydrogen atom and ethyl radical. The hydrogenolysis of ethane produced only methane and no ethylene was observed in gas phase; the reaction orders with respect to hydrogen and ethane pressures were, respectively, −0....

Production of maleic anhydride

Abstract: Catalysts for the oxidation of hydrocarbons to acid anhydrides, for example maleic and phthalic anhydrides, are prepared from a vanadium/phosphorus mixed oxide precursor by conditioning it by contact with a strong acid of concentration at least 3N and solvent extraction to remove unwanted phases. The treated precursor is converted to a catalytically active form by heating. Novel catalysts containing phase X are produced. The catalysts may contain rare earth metal promoters.

Structural properties of Sb–Sn—O mixed oxide catalysts

Abstract: Mixed oxides of tin and antimony were investigated by X-ray diffraction and Mossbauer spectrometry as a function of chemical composition and of firing temperature. At low calcination temperatures, antimony is present as Sb5+ dissolved in the SnO2 lattice at 5 atom % Sb and a mixture Sb5++ Sb3+ at higher concentrations.Upon calcination a demixing of the solid solution occurs and an antimony oxide phase is formed. From X-ray diffraction, this phase is identified as a bidimensional Sb2O4 layer. The balance of electrical charges in the lattice is achieved by two different mechanisms as a function of the Sb content: delocalization of electrons in the conductivity band at low antimony content and reduction of Sb5+ to Sb3+ at higher antimony percentage. Good selectivities are obtained for propene oxidation when the system is biphasic; it is postulated that the actual catalyst consists of an oriented film of Sb2O4 supported by the Sb5+–SnO2 solid solution.

Temperature-stabilized pyrogenic oxide mixture of silica oxide, process for its production and its use

Abstract: Pyrogen hergestelltes Siliciumdioxid-Mischoxid mit einer BET-Oberflache von 50 bis 400 m 2 /g, welches Pyrogenically prepared silicon dioxide mixed oxide having a BET surface of 50 to 400 m 2 / g, which 0,01 bis 10 Gew.-% Zirkonoxid oder 0.01 to 10 wt .-% of zirconium oxide or 0,1 bis 10 Gew.-% Eisenoxid oder 0.1 to 10 wt .-% iron oxide, or 0,1 bis 9,9 Gew.-% Titandioxid 0.1 to 9.9 wt .-% titanium dioxide als Bestandteil des Mischoxides enthalt. contains as constituent of the mixed oxide. Das Siliciumdioxid-Mischoxid ist aufgrund der Fremdmetalldotierung temperaturstabiler als das undotierte Siliciumdioxid. The silicon dioxide mixed oxide is due to the foreign metal doping temperature stable than the undoped silicon dioxide. Es kann zur Warmedammung als ungepresstes Material in loser Schuttung oder als kompaktierte Mischung verwendet werden. It can be used for thermal insulation as unpressed material in bulk or as a compacted mixture.

Temperature stabilized silicon dioxide-mixed oxide, the process for its production and use

Abstract: There is prepared pyrogenically produced silicon dioxide-mixed oxide having a BET surface area of 50 to 400 m2 /g which contains as a constituent of the mixed oxide: 0.01 to 10 weight % zirconium dioxide or 0.01 to 10 weight % iron oxide (ferric oxide) or 0.01 to 9.9 weight % titanium dioxide. Because of the doping with the foreign oxide the silicon dioxide-mixed oxide is more temperature stable than the undoped silicon dioxide. The product can be used as thermal insulation either as unpressed material in free bulk form or as a compacted mixture.

Experimental study of respiratory contamination by a mixed oxide aerosol formed from the combustion of a plutonium magnesium alloy.

Abstract: Plutonium aerosol was produced by arc ignition of Pu-Mg alloy (atomic ratio, 1 : 66). Respirable fraction (CMD = 0.33 pm) consisted of aggregates of fine particles (CMD = 0.04 pm). One day after inhalation, we observed a quick deposition of Pu in skeleton (2% inhaled burden) which rose to 8% the 30th day after inhalation. At the same time liver burdens were always 2-3 times lower than skeletal burdens. These results show that Pu particles obtained after ignition at high temperature of Pu-Mg alloy could be classified as W compounds although a noticeable fraction of the inhaled burden behaves as Y compounds according to ICRP Task Group on Lung Model. DTPA treatment efficiency was greater than after 239Pu02 inhalation and was time dependent. Early injection modified significantly transportable fraction. INTRODUCTION THE BEHAVIOUR of plutonium in animals exposed to an aerosol mixture of plutonium and sodium oxides was studied by the “National Radiological Protection Board” (U.K.) and the “Commissariat B 1’Energie Atomique” (France). Results have shown that plutonium in mixed aerosols of plutonium and sodium was more transportable than plutonium dioxide alone (Br75; Me76). In the event of the accidental release of radioactivity due to the plutonium industry it would also be useful to study mixed aerosols generated by mixing plutonium and different metals at high temperature. The use of magnesium in many metallurgical and chemical processes, along with the high inflammability of this metal, led us to study biological reactions to a mixed aerosol obtained by burning a plutonium-magnesium alloy. On the other hand, solubility of Pu after Pu-Na burning has been associated with fine particles and with production of hexavalent state of plutonium (Ch69; Me76a; St78a). In the case of Pu-Mg burning small particles only were produced without any change of the valency state of plutonium (C h69). MATERIALS AND METHODS Alloy preparation Plutonium magnesium alloy was prepared from fusion of Pu and Mg metals in an arc furnace at 10oO-1300°C under argon atmosphere. Initial atomic ratio was Pu : Mg, 1 : 30; i.e. 1 :3 in weight ratio. After fusion the alloy was cut into three parts in the same furnace, then into 29 specimens for different experiments. These alloy specimens were conditioned in silica vacuum flasks. The mean weight of each bar was 380 2 60 mg, each was approx. 5mm in diameter and 5-10mm in length. Specimens were randomized and final atomic ratio was determined by mass spectrometry in 6 specimens. The mean final atomic ratio was Pu : Mg, 1 : 66.

The Nature of Anodic Films on Nickel and Single Phase Nickel‐Molybdenum Alloys

Abstract: The decay of potential after anodization at a passive potential has been followed for a series of nickel‐molybdenum alloys and the observations used to speculate on the effects of molybdenum alloying additives on the nature of the passivating films formed on nickel in at a pH of 2.8. It is concluded that small quantities (<5 w/o) of molybdenum causes considerable defectiveness to passive films, decreasing their stability. It is proposed that at higher alloy levels, but levels which do not produce a two‐phase alloy, a mixed oxide is produced along with a much less stable defective.

Preparation of vanadium phosphorus catalysts

Abstract: The present invention provides a method for the preparation of oxidation catalysts containing mixed oxides of vanadium and phosphorus, which catalysts are particularly effective in the oxidation of n-butane, n-butenes, 1,3-butadiene or a mixture thereof with molecular oxygen or an oxygen-containing gas in the vapor phase to produce high yields of maleic anhydride with good selectivity. Vanadium phosphorus mixed oxide catalyst precursors prepared in solution in organic media are extracted from the organic media with water, with subsequent drying down to recover a precursor solid, or impregnation of a support with the aqueous solution.

X-ray and electrical conductivity studies on iron-aluminium mixed oxides

Abstract: Co-precipitated iron-aluminium mixed oxide cataiysts containing 0 to 100 mol % alumina have been studied by X-ray diffraction and electrical conductivity measurements. Formation of solid solution has been observed. At lower concentrations, aluminium ions occupy the interstitial sites while at higher alumina contents, it forms a substitutional solid solution. Electrical conductivity of the specimens has been measured in air and nitrogen atmospheres in the temperature range room temperature to 400° C. The influence of moisture is found to be significant and it increases with increasing alumina content. A straight line relationship exists between log σ and 1/Tfor all the specimens. The activation energies for conduction in air and nitrogen are observed to be in the range 0.25 to 0.35 and 0.24 to 0.29 eV, respectively. Electron holes are found to be responsible for electrical conduction in these materials.

Temperature stabilized, pyrogenically produced aluminum oxide-mixed oxide, the process for its production and use

Abstract: There is provided temperature stabilized pyrogenically produced aluminum oxide-mixed oxide having a BET surface area of 50 to 200 m2 /g which contains 0.5 to 20 weight % silicon dioxide as a constituent thereof. Because of the silicon dioxide constituent the aluminum oxide does not change into the α-Al2 O3 phase until 1350° C. The temperature stabilized aluminum oxide-mixed oxide is suitable for the production of thermal insulation compositions.

Catalyst of monolithic construction type for purification of waste gas

Abstract: PURPOSE:To obtain a three element catalyst of high activity and monolithic construction by depositing a catalyst component on a carrier applied with a coating film of alumina contg. lanthanum oxide and cerium oxide. CONSTITUTION:The oxide film of the composite oxide or mixed oxide of lanthanum oxide and cerium oxide consisting essentially of alumina, and of 0.05-0.3 cerium/lanthanum atom number ratios, and 2-50wt% the total amt. of rare earth element oxide R2O3, more preferably, 5-35wt% is coated on an inert carrier of porous inorg. oxide, heat resistant metal or the like. A catalyst component contg. a platinum group element is deposited on this oxide film, whereby the catalyst of monolithic construction type for purification of waste gases is obtained. Since this catalyst is deposited with noble metal ions at high density on the surface of the carrier, it has high activity and durability and is used as a three element catalyst.

DISPROPORTIONATION OF CF3Cl CATALYZED BY Al2O3·Cr2O3

Abstract: A mixed oxide of Al2O3 and Cr2O3 (Al2O3· Cr2O3) showed catalytic activity higher than that of Al2O3 or Cr2O3 in the disproportionation of CF3Cl. Maximum conversion (> 30 %) was obtained when the reaction was carried out over the mixed oxide (atomic ratio of Cr/Al:1/9) at 450°C.

Catalytic conversion of alcohols. 15. Alkene selectivity from the conversion of 2-octanol over hafnium-zirconium mixed oxide catalysts

Abstract: Catalysts containing 0-100% zirconia/hafnia were prepared by coprecipitation of the hydroxides and calcination at 600/sup 0/C. No surface enrichment occurred because the hydroxides have similar solubilities and the oxides similar free energies. The selectivity of these catalysts for 2-octanol dehydration to 1-octene was identical to that of hafnia, approx. 30% up to approx. 75 mole % zirconia content; it changed abruptly to that of pure zirconia, 90% at higher zirconia contents.

Physico-chemical properties of iron-tin mixed oxide catalysts in cyclohexane oxidation

Abstract: The state of mixed iron-tin oxide catalysts with a variable ratio of their metallic components has been studied by Mossbauer and ESCA spectroscopy. The results are compared with the activity of these catalysts in cyclohexane oxidation.

Solid state studies on rare earth mixed oxide pyrochlores Er2(V1−x Fe x )4/3 W2/3O7

Abstract: Complete series of solid solutions exist in the mixed oxide pyrochlore system, Er 2 3+ (V 1−x 3+ Fe x 3+ )4/3 W 2 3/6+ O7, with the crystal structure changing from cubic to rhombohedral atx=0·25. The compounds are semiconductors at 300 K exhibitingp- orn-type behaviour depending on the value ofx. The observed resistivity and Seebeck coefficient data as a function of temperature have been interpreted in terms of a hopping mechanism.

Synthesis of mixed oxide composition and products obtained

Abstract: A non-aqueous gel of at least two metal oxides which is a precursor for glassy amorphous or crystalline mixed oxides is produced by reacting an alkoxide of one metal and a halide of another metal producing a low molecular weight polymeric reaction product, heating the reaction product to produce a polymeric product of substantially higher molecular weight, and heating the higher molecular weight polymeric product in air to remove its carbonaceous content.

The Dissociative Vaporization of Alkaline Earth-Containing Mixed Oxide Thermionic Emission Materials

Abstract: The high-temperature chemistry of some mixed oxide thermionic emission materials has been studied by Knudsen cell mass spectrometry. It has been shown that these materials, such as Ba2CaWO6 and Ba3Y2WO9, vaporize by a dissociative process. The dominant volatile components over these materials are BaO(g), Ba(g), and Ca(g), with BaWO4(g) and BaWO3(g) being present in lower concentrations. The decomposition of these materials begins at approximately 1300°C.

Selective ortho substitution of phenol cpds. - by gas phase reaction with methanol or di:methyl ether over mixed oxide catalyst

Abstract: Prodn. of ortho-substd. phenols (I) comprises reacting a phenol (II), opt. mono- or di-alkyl substd. but with at least one free ortho position, in the gas phase with methanol and- or dimethyl ether at mole ratio 1:0.1-10. Reaction is at 270-390(300-380) deg.C with dwell time 0.05-10(1-3.5)sec. over a mixed oxide catalyst (A). (A) comprises (a) Fe oxide; (b) Cr oxide; (c) Si oxide; and (d) at least one alkaline earth, La and Mn oxide; or (a) Fe oxide; (b) Cr oxide; (c) at least one of Ge, Ti, Zr, Sh and Pb oxides, and (d) at least one alkali and-or alkaline earth metal, La and Mn oxides, there being 0.1-10 moles each of (b), (c) and (d) per 100 moles (a). 2,6-Dimethylphenol is an intermediate for poly(phenylene oxide) and 2,4,6-dimethylphenol is used in prodn. of Vitamin E. Selectivity for ortho substitution is 98-99% and even after 2000 hr. operation there is no significant decrease. Methanol consumption is substantially lower than in known processes.

Multicomponent Oxide Systems for Corrosion Protection.

Abstract: : The formation and function of corrosion-resistant surface oxide films on aluminum have been investigated during a three-year research effort Mixed oxide coatings should, based on a conceptual model, offer superior corrosion resistance (a mixed oxide is defined as an oxide system based on more than one cation species) The structures of the mixed oxide coatings studied were characterized using Auger electron spectroscopy, x-ray photoelectron spectroscopy, and ion microprobe mass analysis Corrosion resistance was assessed by exposing specimens in a salt chamber Chromate coating systems, long in use on aluminum, were examined first to provide a standard against which to measure coating performance Chromate coating formation was explained in terms of the role of hydrogen fluoride (or hydroxyl ion) in the dissolution of the native aluminium oxide layer and through the influence of the slight solubility difference between chromium and aluminum hydroxides on film growth New types of mixed oxide coatings deposited from nonaqueous solutions of organometallic compounds were developed Titanium-aluminum mixed oxide coatings, deposited from solutions of titanium alkoxides in isopropanol, served as a prototype system for much of this work It was found that the application of certain sulfur compounds in conjunction with titanate coatings resulted in enhanced corrosion resistance, and in one case (AA 6061), the corrosion resistance exceeded that of the chromate coatings The feasibility of the basic approach taken here has been validated It remains for future work to effect further improvements in the technique (Author)

Catalysts Examined by Electron Spin Resonance-Examples from Hydrodesulfurization Catalysis

Abstract: The utility of electron spin resonance (ESR) for catalyst characterization is illustrated for the desulfurization catalysts used to remove sulfur, nitrogen, and organically bound metals from petroleum. These catalysts consist of active metals (Mo, W, Co, Ni) in mixed oxide and sulfide phases on high surface area alumina supports. Coordinated studies of unsupported sulfide and oxide model systems determine the chemical form and number of defect sites on the actual catalysts. Parallel catalysis studies correlate ESR defects and catalytic activity for many reactions.