Showing papers on "Noble metal published in 1978"

Alloy depletion profiles resulting from the preferential removal of the less noble metal during alloy oxidation

Abstract: The assumptions involved in Wagner's original treatment of alloy depletion profiles are examined and found to be acceptable for many situations. Finite difference analyses do not result in profiles which are significantly different from those obtained by the much simpler analytical solution once steady-state parabolic growth is established. Consequently an analytical solution is preferred and its combination with the classical Wagner expression for scale growth leads to a unified description of alloy oxidation when only the least noble metal is oxidized. The description is tested for an Fe-27.4wt.% Cr alloy oxidized at 1273°K and agreement between theoretical and experimental results is satisfactory. Alternative treatments of alloy oxidation which require that there be no recession of the alloy-scale interface are discussed and it is concluded that this assumption is unnecessarily restrictive in many cases. Suggestions that the oxidation of austenitic steels is controlled by diffusion in the alloy and that an interfacial transfer step is of importance in determining the oxidation rate in some cases are shown to be based on invalid assumptions. An analytical solution to the diffusion equation is developed for the case when a phase change occurs in the alloy because of less noble metal depletion and an expression is also presented for the profile developed in the limiting case where depletion is determined by scale evaporation.

Noble metal-refractory metal alloys as catalysts and method for making

Abstract: Finely divided noble metal-refractory metal alloys and methods for making them are disclosed. As catalysts these alloys have greater activity than a catalyst of the same unalloyed noble metal and may be advantageously used as electrodes for fuel cells particularly when supported. The method for making supported catalysts involves a simple and inexpensive procedure for converting a supported, finely divided noble metal catalyst to the desired alloy. In a preferred embodiment the process includes intimately contacting the supported noble metal catalyst with a finely divided refractory metal oxide, the metallic component of which is capable of enhancing the activity of the catalyst when alloyed therewith, and then heating to a sufficiently high temperature, preferably in a reducing atmosphere, to reduce the oxide and simultaneously form a finely divided, supported alloy of the noble metal and the metallic component of the oxide.

Process for isomerizing 1-butene to 2-butene

Abstract: Process for isomerizing 1-butene to 2-butene by contacting 1-butene, at a temperature from 50 to 140° C, in the presence of hydrogen, with an isomerization catalyst containing a noble metal from group VIII of the periodic classification of elements, which catalyst was previously contacted with a sulfur compound at a temperature from 50 to 400° C and then with hydrogen at a temperature of at least 50° C.

Noble metal/vanadium alloy catalyst and method for making

Abstract: A novel catalyst comprises an alloy of a noble metal and vanadium. The catalyst is particularly useful in an electrochemical cell cathode electrode. The method for making the alloy involves reacting a vanadium compound with sodium dithionite to form a sol of a finely dispersed vanadium sulfite complex, and then reacting noble metal particles with the complex in a reducing environment.

Process for the conversion of relatively low molecular weight hydrocarbons, to higher molecular weight hydrocarbons catalyst-reagents for such use in such process, and the regeneration thereof

Abstract: Novel regenerable catalyst-reagents, and a new and improved process utilizing said regenerable catalyst-reagents, for the conversion, and oligomerization of hydrocarbons, notably methane, at relatively low temperatures to produce products rich in ethylene or benzene, or both, usually in admixture with other hydrocarbons; and process for the regeneration of said catalyst-reagents (a) The catalyst-reagents are multi-functional and are comprised of (1) a Group VIII noble metal having an atomic number of 45 or greater, nickel, or a Group 1-B noble metal having an atomic number of 47 or greater; (2) a Group VI-B metal oxide which is capable of being reduced to a lower oxide, or admixture of metal oxides which includes one or more of such metal oxides; and, (3) a Group II-A metal or alkaline-earth metal, composited with a suitably passivated, spinel-coated refractory support, notably an inorganic oxide support, preferably alumina (b) The process is one wherein a hydrocarbon feed, notably methane, is contacted and reacted with a catalyst-reagent as characterized in (a), supra, at temperature ranging from about 1150° F to about 1600° F; and also embodies (c) a process for regeneration of said catalyst-reagent which has become inactivated as by use in the process characterized in (b), supra, by contact thereof in an exothermic reaction with water, oxygen or an oxygen-containing gas, preferably air, at temperatures sufficient to reoxidize the Group VI-B metal oxide, and preferably also sufficient to provide the required sensible heat for the operation of said novel hydrocarbon conversion process (b), supra, on recycle of the catalyst-reagent

Electrochemical cell electrodes incorporating noble metal-base metal alloy catalysts

Abstract: A novel and improved fuel cell electrode includes a finely divided noble metal-base metal alloy catalyst. The catalytic activity of noble metal in the electrode is greater than the catalytic activity of the same unalloyed noble metal. Theoretically any base metal may be advantageously alloyed with the noble metal and will yield improved catalytic activity. Preferably the finely divided alloy is supported.

Process of regenerating a noble metal catalyst used in the reduction of organic nitro compounds

Abstract: Noble metal catalysts are regenerated according to a process comprising the steps of washing the deactivated catalyst with a polar organic solvent; contacting the washed catalyst with a hot aqueous alkali metal hydroxide solution; contacting the catalyst with an oxygen-containing gas at moderately elevated temperatures; and washing the catalyst a final time with a polar organic solvent. This method of regenerating the catalyst is particularly useful to reactivate palladium on carbon catalysts deactivated in the reduction of nitrophenol compounds to aminophenols.

Carbonylation with Group VIII noble metal catalysts

Abstract: In the carbonylation of alkyl esters in the presence of a Group VIII noble metal catalyst to produce a reaction mixture comprising volatile components and the non-volatile Group VIII noble metal catalyst, and the volatile components are separated from the catalyst, catalyst activity is maintained by providing a partial pressure of hydrogen of at least 10 psi during the separation of the volatile products. A partial pressure of at least 15 psi of carbon monoxide is also preferably provided, particularly when a metal promoter for the Group VIII noble metal catalyst is present, during such separation.

Interfacial noble-metal corrosion in metal to ceramic reaction welding

Abstract: WELDING refractory ceramic oxides to a range of transition metals in oxidising atmospheres may involve two apparently distinct bonding mechanisms1,2. In type 1 bonds, which involve the noble metals, a sharp phase discontinuity at the metal–ceramic interface is maintained, even after prolonged annealing in oxygen. No intermediate oxide phase, other than the original ceramic, is observed. The substantial bond strengths3 reach their maximum value after a few hours and do not deteriorate with time. Residual thermal stresses are small as shown by high resolution hot-stage electron microscopy4. In contrast, in type 2 bonds, in which the more reactive transition metals are used, an intermediate (quaternary) oxide layer is clearly visible, its thickness growing with time. The bond strength depends on the corrosion behaviour of the metal and the mechanical strength of the intermediate oxide layer, as metal cations diffuse by bulk and grain boundaries into the ceramic. It is influenced by the duration of the anneal, as the oxidation process continues. Here we report the experimental observation that the couples Pd/MgO and Pd/Al2O3 form type 2 bonds below 800 °C and strong type 1 bonds above that temperature, when annealed in air.

Use of noble metal solutions in catalyst regeneration zones

Abstract: The use of a solution in a catalyst regeneration zone to increase the CO 2 /CO ratio of the flue gas produced in the regeneration zone comprising a noble-metal CO oxidation promoter and a solvent comprising a selected saturated aliphatic alcohol.

Extraction of gold and silver

Abstract: A process for the extraction of gold and silver from their ores in which the ore is reduced to a particle size of 1 mm or less and mixed with a lixiviant, e.g., alkaline sodium or potassium cyanide, in an amount to provide a liquor content of about 8 to 12%, the lixiviant coated particles are allowed to react for a time sufficient for the lixiviant to extract the noble metal and the particles washed with water to obtain a solution of the noble metal salt from which the noble metal is recovered.

Hydrocarbon conversion processes utilizing a catalyst comprising a Group VIII noble metal component supported on Group IIA metal oxide-refractory metal oxide supports

Abstract: The instant invention relates to a novel catalyst which comprises a physical mixture of (1) at least one catalytically active transition metal selected from Group VIII of the Periodic Table of the Elements in combination with at least one alkaline earth metal oxide, and (2) an acidic refractory oxide. The combination of one or more of said Group VIII metals and one or more alkaline earth metal oxides may be provided by supporting said metals and said oxides on a nonacidic refractory oxide support. These catalysts are useful in hydrocarbon conversion processes and are characterized as having improved stability under oxidizing conditions, for example, the high temperature oxidation treatments encountered in regenerating deactivated reforming catalysts.

Process for the preparation of 2,2'-dichloro-hydrazobenzene

Abstract: The catalytic hydrogenation of o-nitro-chlorobenzene in aqueous alkali metal hydroxide solution with addition of an aromatic non-watermiscible solvent at an elevated temperature and under pressure using a noble metal catalyst and a polycyclic quinone as a co-catalyst leads to high and well-reproducible yields of 2,2'-dichloro-hydrazobenzene when the quinone is a derivative of anthraquinone, especially a hydroxy-anthraquinone. The product is obtained in so high a quality that it can be transformed without isolation or purification into 3,3'-dichlorobenzidine.

Noble metal alloy for dentistry and dental restoration using same

Abstract: A noble metal alloy having a solidus temperature above 1100° C., a Vickers hardness of at least 150 and a coefficient of thermal expansion at 600° C. of at least 0.8 percent consists essentially of 45-60 percent gold, 30-50 percent palladium and 2-7 percent tin. The alloy includes 3 to 10 percent of zinc, and mixtures thereof with indium, and up to 2 percent of rhenium, nickel, platinum and mixtures thereof. The tin to palladium ratio is 5-15:100 and the gold, palladium and platinum content must not exceed 95 percent of the composition. This alloy provides a desirable casting upon which may be fired a porcelain coating to provide a desirable dental restoration from the standpoints of hardness, inertness and aesthetics.

Vinyl acetate preparation

Abstract: A Group VIII noble metal catalyst supported on an alumina carrier having an alumina content greater than 99.0%, a crystalline alpha-alumina content of greater than 96%, a theta-alumina content of less than about 3.0%, a total calcium and magnesium content of less than 750 ppm, a surface area of about 2 to 6 m 2 /g, an average crush strength of from about 20 to 45 lbs., a bulk density of less than about 1.35 g/cc, and an acetic acid loading of less than about 1.5% in 200 hours. The catalyst generally contains an alkali metal carboxylate activator and optionally a metal such as gold, copper, and the like. The catalyst is particularly useful for the preparation of unsaturated organic esters such as vinyl acetate and allyl acetate by a vapor phase process wherein a gaseous mixture of an olefinic compound, a lower carboxylic acid, and oxygen is contacted with the catalyst.

Catalyst and a process for its preparation

Abstract: A novel catalyst precursor which comprises a Group IV-B transition metal oxide deposited on the surface of an inorganic metal oxide support, preferably alumina; especially where the Group IV-B transition metal oxide is deposited on the support surface as discrete areas separated by areas of support surface which contain little, if any, of said Group IV-B transition metal oxide; and a catalyst composition comprised of a cluster of a Group IV-B transition metal oxide and a Group VIII metal preferably a Group VIII noble metal, deposited on an inorganic metal oxide support, particularly an alumina support, especially where the clusters are deposited on the surface of the support, as discrete clusters separated by areas of support surface which contain little, if any, of said Group VI-B transition metal oxide, or clusters of said Group IV-B and Group VIII metals.

Catalyst activation in oxidation process

Abstract: A noble metal catalyst, such as palladium, is activated by successive and sequential reactions with an alcohol, such as hydroxybenzyl alcohol, and oxygen or a gas containing oxygen in an aqueous, preferably alkaline, medium, The catalyst activated in the aforementioned manner is particularly useful for the oxidation of alcohols to the corresponding aldehydes.

Supported heteronuclear noble metal cluster catalysts and method for preparing same

Abstract: New heteronuclear noble metal cluster complexes have been discovered and synthesized for the first time. These complexes are (pyridine) 2 Pt[Ir 6 (CO) 15 ], (pyridine) 2 --Pt[Ir 2 (CO) 7 ], (pyridine) 3 Pt[Ru 3 (CO) 12 ], ((C 6 H 5 ) 3 P) 2 --Pt[Ir(CO) 3 P(C 6 H 5 ) 3 ] 2 , ((C 6 H 5 ) 3 P) 2 Rh(CO)[Ir(CO) 4 ], and (pyridine) 2 Pt[Rh(CO) 2 (P(C 6 H 5 ) 3 ) 2 ] 2 . These new heteronuclear noble metal cluster complexes are useful as supported mixed noble metal catalyst precursors. These new cluster complexes, of known stoichiometry, are deposited on anhydrous refractory inorganic oxide or carbon supports and then reduced resulting in the formation of a supported heteronuclear noble metal catalyst having the same metals stoichiometry as the starting cluster complexes. In this way, precise control can be exercised over the ratio and distribution of multiple metal components in a mixed noble metal catalyst. The usage of preformed heteronuclear noble metal cluster complexes as supported mixed metal catalyst precursors maximizes surface alloy formation and also yields unique mixed-metal cluster structures on the support surface.

Hydroisomerization process and catalyst

Abstract: A process for the hydroisomerization of paraffinic hydrocarbons employing a catalyst composed of a noble metal, alumina and chlorine. The catalyst is prepared by treating a composite of noble metal and alumina with an aluminum compound such as an inorganic or organic salt of aluminum, preferably aluminum nitrate, calcining the treated composite and thereafter contacting the treated composite with a conventional chloride activating agent. By treating and calcining the composite with an aluminum salt, the amount of noble metal retained on the catalyst's surface during chloride activation is maximized enabling high conversions of normal paraffins to isoparaffins to be realized.

Method for electrolyzing molten metal chlorides

Abstract: OF THE DISCLOSURE A method of electrolyzing a molten chloride which comp-rises electrolyzing a molten bath of a chloride of a metal more base than hydrogen, such as sodium, magnesium, calcium or aluminum, in an electrolytic cell containing an anode and a cathode to form chlorine at the surface of the annode and the metal at the surface of the cathode, wherein the anode comprises an electrically conductive substrate resistant to corrosion by the molten bath of the metal chloride and the electrolysis products thereof and having thereon a coating of a noble metal oxide, and with the electrolysis being carried out in the presence of an oxide or oxychloride of a metal more base than the metal formed at the cathode where the concentration of the oxide or oxy-chloride of the metal present in the molten bath, expressed as the mole fraction of free oxygen, is at least about 1 x 10-4.

Superficially mixed metal oxide electrodes

Abstract: A superficially mixed metal oxide electrode and a method of preparing same. The electrode is useful in anodic electrochemical reactions. There is no distinct outer layer of either noble metal or noble metal oxide. Instead, the noble metal or noble metal oxide is superficially mixed in with a layer of an oxide of a film-forming metal which has been deposited over a conductive base metal.

Cell having in situ reduction of electrode overvoltage

Abstract: A method and apparatus for in situ reduction of cathode overvoltage in electrolytic cells. The method involves introducing low overvoltage or noble metal ions into the catholyte solution and plating those ions on the cathode in situ. The apparatus includes a low overvoltage or noble metal ion generating device for introducing low overvoltage or noble metal ions into the cathode solution so as to plate them in situ on the cathode during or prior to cell operation.

Temperature and pressure effects on surface processes at noble metal electrodes. Part 2.—Volume of adsorbed H and oxygen species at Pt and Au

Abstract: The multiple states of electrosorbed H and oxygen species at Pt, which arise below monolayer coverage, are of current interest in electrochemical surface science.The results of experiments on the effects of high hydraulic pressure on H chemisorption and surface oxide formation at Pt electrodes are described. “Clean” electrochemical surface studies can be performed in a shrinkable Teflon vessel, under oil, up to several thousand bars. The equilibrium volume changes for electrodeposition of H and surface oxidation of Pt are evaluated allowing for the effect of pressure on the potential of the reversible reference electrode used. The volume of electrodeposited H is found to be ≈ 5.1 cm3 mol– 1 at Pt, a value similar to that for H in methylene groups.The pressure effects on surface oxidation arise from (a) the volume change in the surface oxidation reaction itself and (b) the volume change in desorption of specifically adsorbed anions which controls, in part, the potential for onset of surface oxidation of Pt and Au electrodes. Semi-quantitative interpretations of the observed behaviour are offered.

Treatment of reducing gas for suppression of corrosiveness

Abstract: The disclosed invention embodies both catalyst and process. The catalyst is comprised of a Group VIII metal, preferably a noble metal, especially platinum, or copper composited with a low acidity inorganic oxide base, preferably alumina. A bed of the catalyst is contacted at elevated temperature with nitrogen oxide containing gas at net reducing conditions to convert the nitrogen oxide to non-corrosive, innocuous by-products to render the gas useful for reservoir pressure maintenance injection needs. In all embodiments, the base with which the metal, or metals, is composited is one having an acidity ranging from about +6.8 to about +0.8 Ho (Hammet acid function), preferably from about +6.8 to about +1.5 Ho. Inorganic oxide bases, especially alumina, which exhibit a weakly acidic Hammet acidity function, Ho≧+0.8, when impregnated with a noble metal, or copper, show a marked improvement in NO x removal vis-a-vis catalysts prepared by impregnating more strongly acidic aluminas with said metal species.

Hydrocarbon conversion processes utilizing supported heteronuclear cluster complex catalysts

Abstract: Hydrocarbon conversion processes wherein hydrocarbon feedstreams are contacted with heteronuclear noble metal catalysts are improved by the use of supported heteronuclear noble metal cluster catalysts prepared from novel supported heteronuclear noble metal cluster complexes. The heteronuclear noble metal cluster complexes used as catalyst precursors are selected from the group consisting of (pyridine) 2 Pt[Ir 6 (CO) 15 ], (pyridine) 2 Pt[Ir 2 (CO) 7 ], ((C 6 H 5 ) 3 P) 2 Pt[IR(CO) 3 P(C 6 H 5 ) 3 ] 2 , (pyridine) 2 Pt[Ru 3 (CO) 12 ] ((C 6 H 5 ) 3 P) 2 Rh(CO)[Ir(CO) 4 ], (pyridine) 2 Pt[Rh(CO) 2 (P(C 6 H 5 ) 3 ) 2 ] 2 . Heteronuclear noble metal cluster catalysts prepared by the reduction of supported heteronuclear noble metal cluster complexes exhibit greater activity, and lower coking rates for numerous hydrocarbon conversions than conventionally prepared supported mixed noble metal catalysts of the same nominal metals concentration.