Showing papers on "Mixed oxide published in 1983"

Study of mixed-oxide catalysts containing bismuth, vanadium and antimony. Preparation, phase composition, spectroscopic characterization and catalytic oxidation of propene

Abstract: The structural and catalytic properties of oxides in the Bi–V–Sb–O system, which are propene oxidation catalysts, have been studied. Two domains of solid solutions exist for the compounds BiV1–xSbxO4, with the scheelite structure for 0 ⩽x < 0.04 and a monoclinic structure for 0.876 ⩽x⩽ 1. Characterization by X-ray photoelectron spectroscopy (X.p.s.) shows that for a given MO (M = Bi, V or Sb) environment, the higher the average interatomic distance, the higher the cation binding energy, corresponding to an effective decrease in electronic density. From a semi-quantitative X.p.s. analysis of the surface composition of the BiV1–xSbxO4 system it is shown that for low values of x(x⩽ 0.10) the surface concentrations of vanadium and oxygen decrease sharply compared with those of the other elements. Activities and selectivities for acrolein, determined in a stirred gas–solid reactor, are measured as a function of x. Oxides having the scheelite structure exhibit a sharp increase in activity with increasing x. The larger performance found for x= 0.035 is connected with a high oxygen mobility.

A Scientific Approach To The Preparation Of Bulk Mixed Oxide Catalysts

Abstract: Publisher Summary This chapter focuses on mixed oxide catalysts, and presents an approach, as scientific as possible, to the selective synthesis of mixed oxide catalysts, i.e. those, which are uncommon, made of mixed oxides or true solid solutions and those, which are more numerous, made of a complex association of mixed oxides (or solid solutions) and of single oxides. In all cases, the mixed oxide catalyst is the result of a complex synthesis method comprising many elementary steps. These steps must lead to the desired state of the following characteristics: bulk structure, texture, superficial and bulk composition, and metal oxidation state. This implies the fixing and the controlling of the main parameters of each elementary step and a systematic characterization of all the intermediary precursors. The mixed oxide coming from the last thermal activation step is usually different from the catalyst that has a steady-state interaction with the reaction medium. The chapter discusses some of these main steps, and illustrates transformations of the catalyst in contact with the reaction medium by a few examples.

Method of making ABO3 of the cubic perovskite structure

Abstract: Disclosed is a method of making a continuous mixed oxide thin film. A composition is prepared of an alkoxide source of one of the metals in the mixed oxide, a chelate source of a second metal in the mixed oxide, sufficient alcohol to solubilize sources of all metals in said mixed oxide and about 1 to about 2 moles of water per mole of mixed oxide. The composition is applied to a substrate and the coating on the substrate is heated to at least about 500° C. to evaporate the solvent and produce the mixed oxide film on the substrate.

Development of a Process for Co-Conversion of Pu-U Nitrate Mixed Solutions to Mixed Oxide Powder Using Microwave Heating Method

Abstract: For the complete nuclear fuel cycle, the development of a process for the co-conversion of Pu-U nitrate mixed solutions to mixed oxide powder has been performed along the line of non-proliferation policy of nuclear materials. A new co-conversion process using a microwave heating method has been developed and successfully demonstrated with good results using the test unit with a capacity of 2 kg MOX/d. Through the experiments and engineering test operations, several important data have been obtained concerning the feasibility of the test unit, powder characteristics and homogeneity of the product, and impurity pickups during denitration process. The results of these experimental operations show that the co-conversion process using a microwave heating method has many excellent advantages, such as good powder characteristics of the product, good homogeneity of Pu-U oxide, simplicity of the process, minimum liquid waste, no possibility of changing the Pu/U ratio and stable operability of the plant. Since Augu...

Process for nitration of benzene

Abstract: A process for the gas-phase nitration of benzene which comprises treating benzene with, as nitrating agent, an oxide of nitrogen in the presence of a solid catalyst, characterised in that the nitrating agent is NO2 or N204 and the catalyst is composed of an acidic mixed oxide containing at least one of W03, MoO3 and Ti02 and optionally containing SiO2 and/or ZnO

Alkali regeneration process

Abstract: The invention relates to an improvement in a method of regenerating alkaline or alkaline earth metal oxides or hydroxides from solution particularly in delignification processes wherein a suitable transition metal such as ferric oxide is burnt with the solution to produce a mixed oxide that is subsequently treated in hot water to regenerate the alkaline or alkaline earth metal oxide or hydroxide and precipitate the transition metal oxide. The improvement controls the presence of fines in the transition metal oxide to maintain these at an acceptable level in the fluidized bed combustion zone. This is achieved by contacting the fines with spent liquor from a delignification process. The invention also provides for the pelletization of the fine material of the transition metal oxide and spent delignification liquor can be used as a binder in the formation of such pellets.

Process for preparing phosphorus-vanadium mixed oxide oxidation catalysts

Abstract: Phosphorus-vanadium mixed oxide oxidation catalysts are prepared by introducing a substantially pentavalent vanadium-containing compound and a pentavalent phosphorus-containing compound into an alcohol medium capable of reducing the vanadium to a valence state less than +5 in the presence of an alcohol-modifying agent to form a phosphorus-vanadium mixed oxide catalyst precursor. The catalyst precursor is recovered, dried, formed into desired structures, and calcined at temperatures from about 250° C. to about 600° C. The catalysts are highly effective in that they exhibit a weight/weight productivity of at least 70 grams of maleic anhydride per kilogram of catalyst per hour.

Mixed rare earth metal, divalent transition metal, aluminum oxide

Abstract: A mixed aluminum oxide having the following formula: X.sup.1.sub.(x.sbsb.1.sub.-x.sbsb.2.sub.) X.sup.2.sub.(x.sbsb.2.sub.) M 1 .sub.(y.sbsb.1 -y .sbsb.2.sub.) M 2 .sub.(y.sbsb.2.sub.) Al.sub.(z.sbsb.1 -z .sbsb.2.sub.) M 3 .sub.(z.sbsb.2.sub.) O 19 wherein X 1 and X 2 , which can be the same or different, represent a metal selected from the group consisting of lanthanum, praseodymium, neodymium, samarium and gadolinium, provided that X 1 and X 2 are different when X 1 or X 2 represents lanthanum or gadolinium; M 1 and M 2 , which can be the same or different, each represent a metal selected from the group consisting of magnesium and divalent transition metals; M 3 represents a trivalent transition metal; x 1 represents a number from 0.8 to 1; y 1 represents a number from 0.7 to 1; z 1 represents a number from 10 to 12; x 2 represents a number from 0 to x 1 ; y 2 represents a number from 0 to y 1 ; and z 2 represents a number from 0 to 1; and wherein said mixed aluminum oxide has a single phase crystalline structure of the magnetoplumbite type. A process for producing the mixed oxide is also disclosed, as well as its applications to power lasers emitting in the infrared and to telecommunications by optical fibers.

Process for producing maleic anhydride

Abstract: Maleic anhydride is produced by the oxidation of a nonaromatic hydrocarbon having at least four carbon atoms in a straight chain with molecular oxygen or a molecular oxygen-containing gas in the vapor phase in the presence of a phosphorus-vanadium mixed oxide catalyst. Such catalysts are prepared by contacting a tetravalent vanadium compound, dissolved in an aqueous, non-oxidizing acid medium, with crystalline diphosphoric acid to form a phosphorus-vanadium mixed oxide catalyst precursor. The resulting catalyst precursor-containing solution is subjected to a series of concentration/dilution cycles to induce crystallization of the catalyst precursor. The crystals are collected, dried, formed into desired structures, and calcined at temperatures from about 300° C. to about 600° C.

Process for the preparation of alloys of aluminium and of rare earths

Abstract: Process for the preparation of alloys of aluminium and of rare earths with a low rare-earth content The said process consists in reducing at least one oxide of a rare-earth metal with aluminium at a temperature above 700 DEG C An alternative form of the invention also consists in recovering the rare-earth metals present in the mixed oxide powder obtained at the same time as the alloy The alloys obtained according to the invention have many applications especially in the nuclear, aeronautical and metallurgical industries

Nb3Al/oxide/Pb Josephson tunnel junctions fabricated using a CF4 cleaning process

Abstract: Nb3Al/oxide/Pb Josephson tunnel junctions have been fabricated using a new surface cleaning technique, the CF4 cleaning process (CFCP), in which the base electrode is cleaned prior to oxide barrier formation in an Ar and CF4, rf plasma mixture. Adopting lower cleaning voltages than for Nb/oxide/Pb junctions, makes it possible to obtain high‐quality junctions with very low leakage (Vm=30 mV) and uniform Josephson current distribution. Such good junction characteristics indicate the formation of damage‐free cleaned electrode surfaces and highly insulating mixed oxide barriers.

The Conversion of CH3OH into Olefins over Al2O3–Cr2O3 Treated with CF3Cl

Abstract: A mixed oxide of Al and Cr having an atomic ratio(Al/Cr) of around 9 showed catalytic activity for the conversion of CH3OH into olefins and aromatic compounds after treatment with CF3Cl at 450 °C. The mixed oxide treated with CF3Cl adsorbed a considerable amount of NH3, even at temperatures as high as 500 °C. Analyses of the compositions on the surface layer by using XPS showed that the F component was predominantly bound to Al, not to Cr. Strong acid sites related to the less crystallized AlF3 seemed to be able to promote the conversion of CH3OH.

Valence states and solubility limits in ternary iron-tin-antimony mixed oxide catalysts

Abstract: The electrical conductivity study of a series of ternary Fe−Sn−Sb mixed oxides with 5 at. % Fe has shown that iron dissolves in the structure of SnO2 as ferric ions and, consequently creates acceptor centers which compensate the doping effect of Sb5+ ions simultaneously dissolved, thus increasing the maximum dissolution of pentavalent antimony and shifting thereby the apparition limit of Sb3+ ions towards higher Sb contents.

Gas sensitive element

Abstract: PURPOSE:To improve remarkably selectivity for malodorous gas and alcohols, by constituting a gas sensitive element by baking an electrode consisting essentially of lutenium oxide on an element substrate consisting essentially of complex oxide of titanium and niobium. CONSTITUTION:A special grade titanium oxide TiO2 and niobium oxide as starting materials are mixed in a specific ratio of seven kinds, and mixed oxide is molded by pressing and calcined. A gas sensitive element is formed by attaching lead wires 4, 5 of RuO2 separation electrodes 2, 3 on one side of a sintered body 1. The most suitable ratio is Nb/Ti=2/1 and a sensitivity S is attained 500 times at the ratio of Nb/Ti=2/1 denoting the ratio Ra/Rg of a resistance value Ra in the atmosphere and a resistance value Rg in 100ppm gas as the sensitivity S. The figure is shown the sensitivity of each 100ppm malodorous gas and combustible gas at 450 deg.C working temperature of Nb/Ti=2/1.

Studies involving high temperature desulfurization/regeneration reactions of metal oxides for fuel cell development. Final report

Abstract: Research conducted at Giner, Inc. during 1981 to 1983 under the present contract has been a continuation of the investigation of a high temperature regenerable desulfurization process capable of reducing the sulfur content in coal gases from 200 ppM to 1 ppM. The overall objective has been the integration of a coal gasifier with a molten carbonate fuel cell, which requires that the sulfur content be below 1 ppM. Commercially available low temperature processes incur an excessive energy penalty. Results obtained with packed-bed and fluidized bed reactors have demonstrated that a CuO/ZnO mixed oxide sorbent is regenerable and capable of lowering the sulfur content (as H/sub 2/S and COS) from 200 ppM in simulated hot coal-derived gases to below 1 ppM level at 600 to 650/sup 0/C. Four potential sorbents (copper, tungsten oxide, vanadium oxide and zinc oxide) were initially selected for experimental use in hot regenerable desulfurization in the temperature range 500 to 650/sup 0/C. Based on engineering considerations, such as desulfurization capacity in per weight or volume of sorbents, a coprecipitated CuO/ZnO was selected for further study. A structural reorganization mechanism, unique to mixed oxides, was identified: the creation of relatively fine crystallites of the sulfided components (Cu/submore » 2/S and ZnS) to counteract the loss of surface area due to sintering during regeneration. Studies with 9 to 26% water vapor in simulated coal gases show that sulfur levels below 1 ppM can be achieved in the temperature range of 500/sup 0/ to 650/sup 0/C. The ability of CuO/ZnO to remove COS, CS/sub 2/ and CH/sub 3/SH at these conditions has been demonstrated in this study. Also a previously proposed pore-plugging model was further developed with good success for data treatment of both packed bed and fluidized-bed reactors. 96 references, 42 figures, 21 tables.« less

Preparation of materials

Abstract: The present invention relates to the preparation of materials and more particularly to the preparation of tin oxide materials. Thus, the present invention provides a process for the preparation of a tin oxide material by a gel precipitation process which includes contacting together a metal stannate, an organic gelling agent comprising a salt of a polycarboxylic acid and an acidic precipitating agent to form a gel precipitate. The gel precipitate may be treated further to provide the tin oxide material. The tin oxide material may be tin oxide as such, or a mixed oxide material containing tin oxide and an oxide of another element.

X-ray photoelectron spectroscopy of corrosion inhibitors on metal surfaces 1. Adsorption of chromates on magnesium alloys

Abstract: 1. The composition of the surface layers formed when chromate solutions are applied to a magnesium alloy has been studied. 2. The interaction results in the strong adsorption of the chromate with the reduction of chromium to the +3 oxidation state. 3. Chromate is weakly adsorbed on the surface of a magnesium alloy preliminarily oxidized in water, its amount on the surface is small, and its oxidation state is equal to +6. 4. It has been postulated that the protective layer consists of a mixed oxide of magnesium and chromium.

Catalyst containing iron, chromium, potassium and lanthanum oxides, its manufacture and use in dehydrogenation reactions

Abstract: There are described catalysts containing, as oxides, iron, chromium and potassium, the latter being optionally partly in form of kaliophyllite Al 2 O 3 , 2 SiO 2 , K 2 O, as well as lanthanum, in a proportion, calculated in oxide weight, of 1-15% with respect to the final catalyst. The presence in the catalyst of lanthanum oxide, optionally previously combined with cobalt or vanadium, at least in part in the form of a mixed oxide of the perovskite type, confers to the catalyst an improved activity and/or selectivity in dehydrogenation reactions, particularly of ethylbenzene to styrene.

Selective propylene oxidation over a copper‐tin oxide catalyst

Abstract: The mixed oxide system of copper and tin and the active single oxide, Cu/sub 2/O, were compared for reducibility of the copper ion, relative number and type of active sites, and reaction kinetics. The enhanced selectivity of the mixed oxides may result from the formation of highly selective sites at the expense of less selective sites. The reducibility of the copper ion in the mixture is influenced by the oxidation state of the tin ion. The reactant and product reaction orders are the same for both catalysts but the mixed oxides are more sensitive to inhibition by water. The catalyst composition affects the energetics of the reaction over the copper-tin oxide catalysts.

Catalysts containing mixed oxides 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.

Catalysts containing mixed oxides of vanadium and phosphorus

Abstract: Mixed oxide catalyst of vanadium and phosphorus prepared by a procedure including pretreating the dried catalyst precursor of the said mixed oxides in finely divided form with an acid solution.

Propylene Oxidation on Mixed Oxide Catalysts

Abstract: The catalytic activity in the propylene oxidation, over the mixed oxides Fe2(Mo04)3, a-Te2Mo07 and Fe2(Te03)3 pure and promoted with 5 % of the third simple oxide of the system Mo03 —Fe203 —Te02 has been studied. The addition of the third oxide to the mixed oxide enhances the activity, selectivity or both in the partial oxidation towards acrolein, suggesting a concerted action of the three components of the catalytic system. Regarding the total oxidation,

Production of catalysts

Abstract: Mixed oxide catalyst precursors are milled in the substantial absence of liquid to mean crystallite sizes of at most 1,000 A and formed into catalyst pellets. The process is particularly suitable in the production of vanadium/phosphorus mixed oxide catalysts for the oxidation of butane to maleic anhydride.