Showing papers on "Noble metal published in 1981"

The enthalpy of formation of solid borides, carbides, nitrides, silicides and phosphides of transition and noble metals

Abstract: Enthalpies of formation for transition and noble metal borides, carbides, nitrides, suicides and phosphides are calculated according to the semiempirical model proposed by Miedema and coworkers and are compared with the available experimental data. On the whole there is fair agreement. A few compounds are exceptional since the structure-dependent contribution to the enthalpy of formation is relatively important here.

A possible model for corrosion pitting and tunneling in noble-metal alloys

Abstract: Electron microscope observations of the micromorphology of silver-gold and copper-gold alloys corroded in nitric acid and ferric chloride solutions demonstrate how the surfaces of these alloys become covered by a gold-rich layer following the selective dissolution of the less-noble component. The gold layer forms initially from island nuclei which grow and eventually merge to form a connected structure, enclosing channels and pits where the merger is incomplete. Observations on the kinetics of island growth suggest a model for this form of corrosion by which the surface of the alloy becomes disordered by selective dissolution and then reorders by surface diffusion of the residual gold atoms. Analysis of this model is used to discuss the morphology of islands and pits and the conditions under which the pits might transform into corrosion tunnels. Those results are discussed in relation to previous morphological studies of corrosion tunnelling. It is shown that the surface disordering-reordering mo...

Catalyst for the reduction of unsaturated organic acids

Abstract: Unsaturated carboxylic acids may be subjected to a reduction process in which the resulting product retains the unsaturation of the starting acids by effecting the reaction in the presence of a catalyst comprising cadmium and rhenium composited on a solid support such as alumina. If so desired, the catalyst composite may also contain a noble metal of Group VIII of the Periodic Table.

Supported catalysts and process for their preparation

Abstract: A process for the preparation of a supported catalyst containing a catalytically active metal such as a noble metal is disclosed wherein the supported catalyst is prepared by initially contacting the inert support with a base and disposing an amount of base in the support corresponding to 0.01 to 50 gram equivalents of base per gram equivalent of catalytically active metal to be deposited thereon, drying the so-treated support to a residual moisture content of less than 10 percent of the maximum absorbency of the support and thereafter impregnating the same with a salt solution of a catalytically active metal, e.g., a salt of a catalytically active noble metal. The inert support is one having a BET surface area of less than 20 square meters per gram. The catalyst is useful in hydrogenation, dehydrogenation, hydrogenolysis, oxidation, polymerization, isomerization or cyclization reactions.

Cermet anode electrowining metals from fused salts

Abstract: An anode for use in electrowinning molten metal from a fused salt bath, e.g., aluminium from cryolite-alumina, consists of a cermet material formed from a ceramic oxide of, e.g., a ferrite or chromite, and a metal, e.g., a noble metal or alloy th

Hydrocarbon conversion catalyst system

Abstract: A hydrocarbon conversion catalyst system comprising a mixture of a first catalyst containing a noble metal component deposed on a refractory inorganic oxide and a second catalyst containing a non-noble metal component deposed on a support containing a refractory inorganic oxide and a crystalline aluminosilicate material, and a reforming method employing such catalyst system are disclosed.

Cooling tubes for glass filament production apparatus.

Abstract: This invention relates to glass filament production. Conventionally the hollow cooling tubes and/or solid metal bars utilized in the making of continuous glass fibers have been constructed of high temperature corrosion resistant materials whose costs are exorbitant for extensive present day factory operations. The present invention dramatically reduces the price of cooling tubes (24) suitable for use in the making of glass filaments by coating or cladding a relatively inexpensive base or substrate metal (48) such as nickel, Inconel, molybdenum copper, alloys thereof or a refractory material with a high temperature corrosion resistant material (50) such as the noble metals, e.g. platinum, palladium, rhodium, iridium, gold, silver or alloys thereof. Fins (52) which may be attached to the cooling tubes (24) may be made either of a solid noble metal or may also be coated or clad in the same manner as the cooling tubes (24).

Recovery of noble metal values from carbonylation residues

Abstract: Heavy residues produced by noble metal catalyzed carbonylation reactions and containing Group VIII noble metals, particularly rhodium, are treated with reagents to precipitate solids containing substantially all of the noble metal contained in the residues. The solids may be further treated to concentrate the noble metals or they may be returned directly for reuse in the carbonylation reaction. Suitable reagents include aliphatic alcohols, carboxylic acids, and carboxylic acid esters. Preferred are branched-chain alcohols, especially tertiary alcohols; of the acids, acetic acid is particularly preferred; and of the esters, n-butyl acetate and ethylidene diacetate are preferred. Subsequent treatments with other solvents, e.g., alkanes, cycloalkanes, ethers, and aromatic compounds, may be used to further concentrate the rhodium content of the precipitated solids.

Noble metal-coated cathode

Abstract: Cathodes comprising a conductive metal substrate, such as a ferrous metal or titanium, having thereon an intermediate protective layer and an overcoating of a mixture of platinum and another noble metal are prepared. These cathodes function in aqueous alkali metal salt solution electrolytic cells or alkali metal halate electrolytic cells to reduce the cathode overvoltage in comparison with conventional ferrous metal electrodes.

Recovery of rhodium from carbonylation residues

Abstract: Residues are formed in the carbonylation of esters or ethers, particularly in the production of acetic anhydride or ethylidene diacetate. Such residues contain noble metal, typically rhodium used as a catalyst, which must be recovered before the residues can be disposed of. In the process of the invention, the rhodium values are freed from the residues by a series of treatments with amines and other reagents, thereby enabling the rhodium to be extracted by subsequent contact with an aqueous halogen acid.

Self-cleaning coating compositions and cooking apparatus coated therewith

Abstract: A self-cleaning coating film is formed using a self-cleaning coating composition including an oxidation, catalyst mixed within a composition including silicone synthetic resin and an organic solvent. The oxidation catalyst includes at least one element selected from a metal such as a noble metal and a metal oxide such as manganese dioxide, copper oxide, iron oxide, nickel oxide, chrome oxide, and the like. The metal is blended with a powder made of alumina, or the like, in the range of about 0.1 to 1.0 weight %. The diameter of the particles of the powder is on the order of about 40 to 300μ. The powder is mixed with the composition in the range of about 5 to 100 weight %. The metal oxide is present in the composition at about 50 weight %. The self-cleaning coating film is formed at about 40 to 300μ thickness. The thus formed self-cleaning coating film is exposed to an elevated temperature of about 300° to 400° Centigrade for about 5 to 10 minutes, whereby the silicone synthetic resin is carbonized to form a film of SiO 2 .

Ceramic body having a metallized layer

Abstract: A ceramic body having a metallized layer which comprises a ceramic substrate and a metallized layer fired on the substrate to be integrated or further comprises a conductive layer consisting of a noble metal or noble metal alloy to be joined onto the metallized layer, the composition of the metallized layer being one or more of a silicide of transition metals belonging to Groups V and VI of periodic table; one or more of a boride of lanthanum and a boride of transition metals belonging to Groups IV, V and VI of periodic table; or a high melting point metal or alloy unmelted at a firing temperature of the ceramic substrate and containing, based on 100 parts by weight of the metal or alloy, 0.5-25 parts by weight of niobium, 0.5-10 parts by weight of yttrium, 0.5-10 parts by weight of tantalum, 0.5-25 parts by weight of mixture of niobium and yttrium, 0.5-25 parts by weight of mixture of yttrium and tantalum, 0.5-25 parts by weight of mixture of niobium and tantalum, 0.5-25 parts by weight of mixture of niobium, yttrium and tantalum, 0.05-3 parts by weight of nickel, 0.5-4 parts by weight of chromium or 0.05-3 parts by weight of mixture of nickel and chromium, which is a useful material for various electronic and electric apparatuses.

Role of Noble Metal d-States in the Formation of the Electron Structure of Ternary Sulphides

Abstract: Combined X-ray spectroscopic and X-ray photoelectron investigations are made of the valence electron energy spectra in the semiconducting ternary sulphides CuGaS2, AgGaS2, AgSbS2, Ag3AsS3, and CuFeS2. The main features of such spectra in the complex compounds of noble metals are shown to be governed by the resonance character of the interaction between the d-states of noble metal and p(s)-states of non-metal as already observed earlier especially in binary compounds of noble metals. Its pecularities are manifesting themselves first of all by the splitting of sulphur p-band into two components and by pushing the latter apart from the noble metal d-band. The magnitude of this p-band splitting increases almost linearly with the amount of copper or silver in the compound. With the use of these data for the first time the broadeningof band gap in AIBIIICVI2 ternary sulphides is explained, which occurs under substitution of copper by silver, contrary to the usual narrowing of it with the increase of the mean atomic number of a compound. [Russian Text Ignored].

Dimensionally stable coated electrode for electrolytic process, comprising protective oxide interface on valve metal base, and process for its manufacture

Abstract: An electrode for use in an electrolytic process is provided with a mixed oxide interface between a titanium base and an outer coating. The mixed oxide is formed at said interface by means of titanium from the base and noble metal from a solution containing a predetermined amount of HCl which attacks the titanium base surface. Slow drying provides a metal chloride mixture which is thermally converted to said mixed oxide of titanium and noble metal in a given ratio, whereby to protect the titanium base from oxidation. An outer coating of manganese dioxide or lead dioxide is electroplated on the mixed oxide layer so as to provide an inexpensive electrode with improved resistance to oxidation. This electrode can be used for various processes where a high resistance to oxidation is required, e.g. as a manganese dioxide anode in a metal electrowinning process or as a lead dioxide anode for electroflotation or organic oxidation reactions.

Treatment of carbonylation residues

Abstract: Residues are formed in the carbonylation of esters or ethers, particularly in the production of acetic anhydride or ethylidene diacetate. When such residues contain noble metal, typically rhodium, used as a catalyst, the noble metals must be recovered before the residues can be disposed of. The metal values are freed from the residues by treatment with amines, thereby enabling the rhodium to be extracted by subsequent contact with an aqueous halogen acid. The residues are pretreated with alkanols and concentrated by evaporation to improve the effect of such amine treatments.

TiO2-supported Noble Metal Catalysts for the NO–CO and NO–CO–H2O–H2–O2 Reactions

Abstract: TiO2-supported noble metal catalysts, such as Pt–, Pd–, and Rh–TiO2, are much more active for the NO–CO reaction in the presence or absence of H2O, H2, and O2 than the corresponding Al2O3– or other supported catalysts. They are effective even in an oxidative gas composition range for the NO–CO–(H2O)–H2–O2 reaction, producing no NH3 in the NO–CO–H2O reaction. Comparison of the catalytic activity and properties of Pt–TiO2 with those of other supported catalysts suggests that the higher activity of the TiO2-supported catalysts could be attributed to their ability to activate NO molecules by the dissociative adsorption at lower temperatures.

Manufacture of fine grain for decoration

Abstract: PURPOSE:To easily manufacture inexpensive powder having the same appearance as nobel metallic powder by coating powderlike nuclei of glass, ceramic, plastic, metal or the like with a noble metal by sputtering. CONSTITUTION:The powdered nuclei are fine grains of >=about 50mu diameter. The thickness of each noble metallic layer is preferably about 50-2,000 Angstrom , and it is adjusted to about 1/250-1/10,000 to the diameter of the whole resulting powder. The sputtering apparatus used is a publicly known one such as bipolar sputtering, magnetron sputtering or other system.

Separation of tars from carbonylation reaction mixtures

Abstract: Tarry residues often are formed in carbonylation reactions, such as those in which esters or ethers are carbonylated to produce ethylidene diacetate or carboxylic acid anhydrides, such as acetic anhydride. Such residues contain Group VIII noble metal catalysts, typically rhodium, which must be separated before the residues can be disposed of. In the process of the invention, the residues are extracted with solvents which preferentially dissolve the tars. Preferred solvents include alkanes, cycloalkanes, halogenated alkanes, and aromatic hydrocarbons, particularly cyclohexane, carbon tetrachloride, and toluene. Separation of the residues from the noble metal catalyst by solvent extraction makes possible the disposal of the residues and the return of the noble metals to the reaction for reuse.

Cathodic protection of catalysts in a corrosive environment

Abstract: Dissolution of Group VIII supported metal catalysts from semi-conductive or conductive carriers in liquid media containing a strong inorganic acid is stopped by making the Group VIII noble metal cathodic with respect to an anode placed in the reactor. A representative embodiment is in processes for synthesis of hydrogen peroxide from its elements.

Image forming method

Abstract: PURPOSE:To enhance resistance to heat, light, and chemicals, and durability, by contacting a silver image formed on a heat-resistant diffusion transfer image-receiving layer by a specified method, with a compound containing a noble metal, such as gold to convert the image into a noble metal image and covering its surface with a heat-resistant transparent layer. CONSTITUTION:Heat-resistant diffusion transfer image-receiving layer 11 is formed by vapor- depositing a silver nuclei precipitating agent such as a sulfide of heavy metal, Zn or Pb, or coating this together with fine glass powder or the like and a small amount of binder on substrate 10, such as glass, aluminum, or polyimide, resistant to temperatures to or above 200 deg.C. Widely known silver halide emulsion layer 12 is formed on layer 11, imagewise exposed, developed with a diffusion transfer developer, and washed with hot water to remove layer 12. Obtained silver image 16 is processed with a solution containing a complex compound of a noble metal smaller in ionization tendency than silver to substitute gold image 17 or the like for silver image 16. Heat- resistant transparent layer 18 is formed on the entire surface of substrate 10 including image using glaze, SiO2, or the like. Photosensitive material 15 prepared by forming silver halide emulsion layer 14 on support 13 in place of layer 12 may be superposed on layer 11 to make imagewise exposure or imagewise exposed material 15 may be superposed to transfer the image and to remove layer 15 after developing.

Dental prostheses with gold-coloured coating

Abstract: Dental prostheses, especially those made of base metal and white noble metal alloys, are provided with a gold-coloured appearance by adherent and abrasion-resistant coatings of titanium nitride or zirconium nitride.

Catalyst for gas purification

Abstract: PURPOSE:To improve catalytic activity and thermal characteristic by wash- coating a carrier by adding a liquid composition of colloidal rare earth element and/or activated alumina to a liquid composition of colloidal noble metal- alumina CONSTITUTION:Soluble noble metallic salt is reduced by being adsorbed to an alumina hydrate, and then mixed with an acidic material such as acetic acid This mixture is dried and then deflocculated to obtain a colloidal noble metal- alumina liquid composition To this formation, a colloidal rare earth element liquid composition and/or activated alumina is added and a carrier is wash- coated The catalyst produced as mentioned above has superior catalytic activity and thermal chracteristics

Fuel cell electrode

Abstract: The invention relates to a fuel cell electrode provided with a catalytic layer containing a noble metal on carbon with a relatively low specific surface and a carbon with a relatively high specific surface, of which electrode the catalytic layer contains noble metal on carbon with a specific surface lower than 100 m 2 g -1 and carbon with a specific surface higher than 150 m 2 g -1 on which there is at most an equally large percentage by weight of noble metal as on the carbon having a relatively low specific surface. The invention also relates to a process for preparing such a fuel cell electrode.

Method of making layered catalysts

Abstract: In a preferred embodiment a solution of a suitable noble metal compound in acetone or other C 1 to C 3 dialkyl ketone is used to selectively place a noble metal catalyst in a very thin layer on an alumina or base metal modified alumina carrier particle.

Process using noble metal-chromium alloy catalysts in an electrochemical cell

Abstract: A novel and improved noble metal-chromium alloy catalyst is disclosed with catalytic oxygen reduction activity at least twice that of the unalloyed noble metal. The noble metal-chromium alloy catalyst disclosed has particular utility as an electrocatalyst for the reduction of oxygen which makes it particularly useful as a cathode catalyst in an acid fuel cell.

Solderable largely base metal electrodes for metal oxide varistors

Abstract: Solderable, largely based metal electrodes for metal oxide varistors are fabricated by screen printing an electrically conductive, air-fireable base metal composition on a varistor material substrate. A distributed fine noble metal array is screen printed over the screened base metal and the varistor heated in air at a temperature of between approximately 500° C. and 800° C. The varistor leads are easily solderable to the noble metal array.