Showing papers on "Noble metal published in 1986"

Photoredox reactions at semiconductor particles incorporated into clays. CdS and ZnS + CdS mixtures in colloidal montmorillonite suspensions

Abstract: CdS and CdS + ZnS mixtures included into colloidal suspensions of clay were prepared and examined by various methods in connection with their potential use as supports or matrices with specific ionic environments and given interlayer spacings. The physical properties of semiconductor particles incorporated into montmorillonite were studied by X-ray spectroscopy and transmission electron microscopy; they were strongly dependent upon the method of preparation. Significant differences were observed for the rate of the photocurrent increase with time (..delta..i/..delta..t) vs. pH, for semiconductors included into clay as compared to a physical mixture of equivalent amounts of clay and nonincluded semiconductor particles. Hydrogen was photoproduced (in the absence of a noble metal catalyst) and detected by GC; the rate depended upon the pH and the nature of the hole scavenger used. Mass transfer problems linked to the spacing between clay sheets decrease the efficiency of clay-incorporated semiconductors for the visible-light-induced hydrogen evolution when compared to previously described silica-supported catalysts. 17 references, 7 figures.

Experimental study of the chemisorbed state of C2 H2, C2 H4, and C2 H6 on noble-metal surfaces.

Abstract: Etude par spectrometrie NEXAFS de la chimisorption de C 2 H 2 , C 2 H 4 et C 2 H 6 sur Cu(100) et Ag(100). Determination de l'orientation moleculaire et de la resistance de la liaison. Comparaison de la position de la resonance de forme σ en phase gazeuse chimisorbee sur Ag, Cu, Pt

Alcohols production by hydrogenation of carboxylic acids

Abstract: Ethanol is produced from acetic acid or propanol is produced from propionic acid by contacting either acetic acid or propionic acid in the vapor phase with hydrogen at elevated temperature and a pressure in the range from 1 to 150 bar in the presence of a catalyst comprising as essential components (i) a noble metal of Group VIII of the Periodic Table of the Elements, and (ii) rhenium, optionally on a support, for example a high surface area graphitized carbon.

Seeding process for electroless metal deposition

Abstract: A process for depositing and tightly binding noble metal seeds onto a substrate by coating the substrate with a very thin layer of a polymer which complexes with a noble metal compound and contacting the layer of polymer with a noble metal compound which forms a complex with the layer of polymer.

Two‐dimensional crystal structure of single Langmuir–Blodgett films deposited on noble metal single crystals studied with LEED.

Abstract: Single fatty acid monolayers were deposited onto noble metal single crystals (Cu, Ag, Au).Low‐energy electron diffraction (LEED) investigations of these 2D monolayer crystals reveal a structural quality comparable to that of single crystal metal surfaces. The monolayer crystal is aligned with respect to the metal substrate and the positional coherence extends over the whole monolayer coated metal substrate 20 mm in diameter.

Composite electrodes for use in solid electrolyte devices

Abstract: A composite electrode material for use in solid electrolyte devices, which comprises a mixture of a noble metal and a semiconducting metal oxide with either electronic (n-type) or hole (p-type) conductivity

Method for the production of alloys possessing high elastic modulus and improved magnetic properties by electrodeposition

Abstract: The present invention relates to a method for the electrodeposition of an ordered alloy structured in alternate discrete layers said alloys possessing high elastic modulus and adjustable magnetic susceptibility. According to the invention, the electrodeposition of at least two metals, characterized by a redox potential gap of at least 0.1 V between said metals, is obtained by the pulse plating technique with a frequency in the range of 0.02 Hertz to 15 Hertz. The concentrations of the noblest metal in the electrodeposition solution should be in the range of 0.001M to 2.0M while that of the less noble metal is about its saturation at room temperature. The discrete layers obtained according to the method are less than 90 Angstroms thickness, being substantially pure. Examples of the metals to be electrodeposited according to the invention are copper-nickel; copper-palladium; nickel-gold; copper-nickel-iron and corresponding alloys with cobalt or iron replacing nickel.

Process for treatment of liquids consisting primarily of methanol

Abstract: Process for the treatment of liquids consisting mainly of methanol as fuels for mobile or stationary combustion engines or as hydrogen sources for fuel cells, which comprises passing the methanol mixture through a reaction chamber containing a noble metal supported catalyst for the catalytic decomposition or steam reforming of methanol, which is composed of: (A) a noble metal component of one or more elements of Group VIII of the Periodic Table on a carrier material which comprises, (B 1 ) TiO 2 or CeO 2 , singly or in admixture with other refractory metallic oxides and/or binders, or (B 2 ) TiO 2 or CeO 2 , applied to the surface of a preformed refractory carrier.

Process for the dehydrogenation of dehydrogenatable hydrocarbons

Abstract: Unsaturated hydrocarbons may be prepared by subjecting a dehydrogenatable hydrocarbon to dehydrogenation in the presence of a dehydrogenation catalyst. The effluent stream from this step, comprising unconverted hydrocarbons, dehydrogenated hydrocarbons, hydrogen and steam, may then be passed to a selective oxidation step in which the hydrogen is selectively oxidized in the presence of an oxygen-containing gas to the substantial exclusion of the oxidation of the hydrocarbons. The oxidation catalyst which is employed will comprise a Group VIII noble metal, a Group IVA metal and a Group IA or IIA metal composited on a metal oxide support. The metal oxide support such as alumina will possess a particular configuration having one or more open channels such as a tubular or cartwheel particle having an outside to inside diameter ratio of the channels ranging from 1.1 to 8 and having a ratio of shape surface to catalyst volume greater than [4D+2L] in which D is the largest representative diameter of the particle and L is the length of the particle.

Catalytic composition for the isomerization of paraffinic hydrocarbons

Abstract: Superior isomerization performance is obtained with a catalytic composition comprising a Group VIII noble metal and a hydrogen form mordenite incorporated with alumina. The superior performance is a direct result of the catalyst composition having a surface area of at least 580 m 2 /g. A novel method of preparing an isomerization catalyst having a surface area of at least 580 m 2 /g is characterized by contacting a formed catalytic composite with an acidic aqueous solution prior to addition of the Group VIII noble metal.

Lead-tolerant catalyst for treating exhaust gas in the presence of SO2

Abstract: A lead-tolerant exhaust gas oxidation catalytic composite for oxidizing gas in the presence of SO 2 comprising a refractory inorganic oxide support material having deposited thereon a noble metal component and having dispersed thereon a protective coating of titania. The refractory support material may be deposited with a noble metal and thereafter applied as a washcoat on a low surface area support matrix followed by a titanium washcoat superimposed thereover. Also, a method for treating exhaust gases containing lead components by contacting the exhaust gas with the catalytic composite is disclosed.

Carrier-supported catalyst and process for making mono-carboxylic anhydrides

Abstract: Monocarboxylic anhydrides of the general formula (RCO) 2 O are made by reacting a carboxylic acid ester or dialkylether of the general formulae RCOOR and ROR, respectively, in which R stands for one and the same alkyl radical having from 1-4 carbon atoms, with carbon monoxide in gas phase, in the presence of iodine or bromine or their compounds as a reaction promoter and also in the presence of a carrier-supported catalyst containing noble metal compounds of group VIII of the Periodic System, at temperatures of 130°-400° C. and under pressures of 1-150 bars. To this end, a novel carrier-supported catalyst is used in which the carrier material has a noble metal/chelate-compound formed of the noble metal compound and a chelator containing organonitrogen, organophosphorus, organoarsenic or organosulfur groups applied to it.

High surface area supported noble metal catalysts and process for their preparation

Abstract: Novel supported noble metal catalysts have high metal loadings and dispersions and are particularly effective catalysts in the conversion of 2-chloropropene to methyl methacrylate by vapor phase reaction with methanol and carbon monoxide.

Redispersion of agglomerated noble metals on zeolite catalysts

Abstract: A process is described for rejuvenation of a deactivated highly siliceous noble metal-containing zeolite catalyst having a framework silica to alumina ratio of at least about 20 which contains agglomerated noble metal in its deactivated state. The process comprises redispersing the noble metals associated with the deactivated catalyst by contacting the catalyst with a stream of inert gas containing molecular chlorine, water and optionally, oxygen, a temperatures ranging from about 150° to about 450° C., a partial pressure of chlorine of from about 6 to about 15 Torr and a ratio of partial pressure of water to partial pressure of chlorine of from about 0.01 to about 2 for a period of time sufficient to achieve redispersion; purging said catalyst with an inert gas; and reducing said purged catalyst in a stream of hydrogen at a temperature ranging from about 140° C. to 550° C.

Catalyst recovery process.

Abstract: A method for recovering noble metals from a catalyst-tar formed during a process in which acetic anhydride is prepared by carbonylating methyl acetate in the presence of a catalyst containing a noble metal such as rhodium, lithium and methyl iodide. Rhodium is recovered from the tar formed in the process by treating the catalyst containing tar with a lower fatty acid at a temperature of at least 100oC, thus isolating the noble metal precipitated tar.

Process for dissolution and recovery of noble metals

Abstract: Disclosed herein is a process for dissolving and recovering noble metals form used catalysts. Noble metal components are leached out from particles supporting or containing at least one noble metal or noble metal compound by subjecting particles them to electrolysis, with the electrolyte being an acid, in the anode compartment of an electrolytic cell which divided by a diaphragm into anode and cathode compartments, and the resulting solution containing noble metals is subjected to electrolysis in a fluidized bed electrolytic cell, thereby causing the noble metals to separate out on to the fluidizing cathode particles. The thus deposited noble metals are again leached out in an electrolytic cell.

Thermodynamical investigations on actinide-noble-metal alloy phases

Abstract: Thermodynamic values and functions for the noble-metal-actinide systems (Pt, Pd, Rh, Ir)-(Th, U, Np, Pu, Am) have been measured for the first time. By use of high-temperature galvanic cells with solid electrolytes (vrO2 + CaO) the ovygen partial pressure of the “coupled reduction” of ovides with highly purified hydrogen in the presence of noble metals could be measured continuously. A refined evperimental arrangement enables measurements with small amounts, up to 10 mg, of highly active actinide alloys. The high stability of the actinide-noble-metal alloys agrees with the predictions of the Engel-Brewer theory for intermetallic compounds. The facility of the coupled reduction decreases in the sevuence Pt > Pd ⪢ Ir, Rh > Ru independent of the base ovide.

Method for treating carbon supports for hydrogenation catalysts

Abstract: A method for treating carbon that is deficient in alkali and/or alkaline earth metal content to improve the efficacy of the carbon as a catalyst support, particularly as a support for a noble metal hydrogenation catalyst.

On the use of markers and tracers to establish the growth mechanism of alumina scales during high temperature oxidation

Abstract: Various ‘marker methods’ have been applied to study the oxidation mechanism of NiAl and Ni-15Cr-24Al-.3Y from 1170 K to 1370 K. Experiments were performed using noble metal markers. The behaviour of both vacuum deposited noble metals as well as implanted noble metals was studied. Also 18O tracers were used. RBS, 18O(p, α)15N resonance spectrometry and SIMS analysis were performed to investigate the alumina scale composition and the position of the marker after oxidation of alloys. The results show that (at 1170 K) NiAl oxidizes mainly by outward diffusion of Al through the oxide scale. It is also shown that noble metal markers may give misleading results. The oxidation mechanism of Ni-15Cr-24Al-.3Y is much more complex. The oxide scale formed on this alloy contains Ni, Cr and Y-rich oxide regions. These regions contribute to the apparent overall oxidation mechanism of the alloy.