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Showing papers on "Platinum published in 1981"



Journal ArticleDOI
Brett A. Sexton1
TL;DR: In this article, the interaction of methanol with clean and oxygen-covered Pt(111) surfaces has been examined with high resolution electron loss spectroscopy (EELS) and thermal desorption spectrography (TDS).

296 citations


Journal ArticleDOI
TL;DR: In this article, a series of bimetallic Pt-Sn/alumina catalysts have been prepared by impregnation of samples of industrial Pt/Alumina reforming catalysts with solutions of Sn(IV) chloride in acetone.

266 citations


Patent
08 May 1981
TL;DR: In this paper, low heating value gases are combusted substoichiometrically in two combustion zones in series in contact with two different supported platinum catalysts in which the concentration of platinum in the catalyst in the first zone is higher than the concentration in the second catalyst.
Abstract: Low heating value gases are combusted substoichiometrically in two combustion zones in series in contact with two different supported platinum catalysts in which the concentration of platinum in the catalyst in the first zone is higher than the concentration of platinum in the second catalyst The combusted gas of reduced carbon monoxide can be directly vented to the atmosphere after energy has been extruded from it for a useful purpose

255 citations


Patent
18 May 1981
TL;DR: In this article, a process for the vapor phase hydrogenation of carboxylic acids to yield their corresponding alcohols in the presence of steam and a catalyst comprising the mixed oxides of ruthenium, at least one of cobalt, nickel, and optionally one of cadmium, zinc, copper, iron, rhodium, palladium, osmium, iridium and platinum.
Abstract: A process is provided for the vapor phase hydrogenation of carboxylic acids to yield their corresponding alcohols in the presence of steam and a catalyst comprising the mixed oxides of ruthenium, at least one of cobalt, nickel, and optionally one of cadmium, zinc, copper, iron, rhodium, palladium, osmium, iridium and platinum. A process is further provided for the preparation of carboxylic acid esters from carboxylic acids in the absence of steam utilizing the above-identified catalysts.

200 citations


Journal ArticleDOI
TL;DR: In this paper, four platinum-based binary catalysts were investigated for the electrochemical oxidation of methanol, and their performance was investigated by linear and cyclic voltammetry.

200 citations




Journal ArticleDOI
TL;DR: In this paper, the state of the platinum and catalytic activity of the Pt sites in benzene hydrogenation and n-hexane dehydrocyclisation were investigated using X-ray diffraction, electron micrography and infrared studies of CO adsorption.
Abstract: Alkaline platinum L zeolites have been studied with regard to the state of the platinum and the catalytic activity of the platinum sites in benzene hydrogenation and n-hexane dehydrocyclisation. X-ray diffraction, electron micrography and infrared studies of CO adsorption led to the conclusion that there are four types of Pt particles: large 100–600 A particles outside the channels, crystals 10–25 A in diameter and small metallic cylinders inside and outside the channels and very small particles in cavities, the latter giving reversible Pt carbonyl clusters upon CO adsorption. The Pt active sites in benzene hydrogenation and n-hexane dehydrocyclization (10–25 A crystals and small cylinders) are strongly dependent upon their environment. In the absence of any acidity their activity increases with the zeolite basicity, while no electron deficiency is observed. The infrared band at 2060–2065 cm–1 of adsorbed CO suggests that Pt particles have an excess of electrons and/or typical faces, corners or edges. It is suggested that the L zeolite structure and field induced these unusual Pt state and catalytic properties.

153 citations


Journal ArticleDOI
TL;DR: The state of Pt-Sn Al 2 O 3 catalysts with Pt and Sn contents (wt%) 0.47-0.5, and 0.95 -0.2 was studied by tin Mossbauer spectroscopy pointing out the special features of the spectra of some highly dispersed species.

137 citations


Journal ArticleDOI
TL;DR: In this paper, a platinum disc electrode under quiscent and steady state conditions, in the pH range of 2-12.3 in an universal buffer medium, was used for hydrogen peroxide analysis.

Journal ArticleDOI
TL;DR: In this paper, the electrocatalytic activity of different alloys for methanol oxidation has been characterized by exchange current densities obtained from extrapolation of Tafel lines of calculated equilibrium potential.


Journal ArticleDOI
TL;DR: In this article, the deactivation of the catalyst is attributed to the formation of platinum oxide (PtO2), which can be reversed by temporarily replacing the oxygen flow by a nitrogen flow.


Journal ArticleDOI
01 Oct 1981
TL;DR: An ESCA study of hemoglobin adsorbed to poly(tetrafluoroethylene) (PTFE) and platinum was described in this article, where a new technique was used to preserve the structural integrity of the adsorbbed protein.
Abstract: An ESCA study of hemoglobin adsorbed to poly(tetrafluoroethylene) (PTFE) and platinum is described. A new technique thought to preserve the structural integrity of the adsorbed protein was used. Wet adsorbed protein films were rapidly frozen prior to placing them in the ultrahigh vacuum environment of the electron spectrometer. On PTFE, hemoglobin was localized into islands approximately 50 A in thickness, with relatively little coverage between the islands. In contrast, however, adsorbed hemoglobin appears to completely and uniformly cover the platinum surface, and may be preferentially oriented with the majority of the protein nitrogen atoms toward the aqueous interface.

Journal ArticleDOI
TL;DR: In this paper, an atom superposition and election delocalization (ASED) technique applied to water adsorption on a small cluster model of Pt(111) shows weak and reversible chemisorption and facile and reversible hydrogen transfer to preadsorbed oxygen atoms as observed by Fisher, Sexton and Gland in EELS and UPS studies.

Journal ArticleDOI
TL;DR: In this paper, the stoichiometry, temperature dependence, and the effect of atmosphere for the thermal decomposition of Pt and Pd ammine complexes exchanged into zeolite Y were investigated by thermogravimetry.

Journal ArticleDOI
TL;DR: In this paper, the formation and stability of surface layers of platinum oxides in single crystals has been studied in ultrahigh vacuum and it is shown that the Pt oxide layers are stabilized by the very slow kinetics of oxygen diffusion to the surface which is responsible for the observed long life of the oxide layers under most catalytic reactions that are carried out at temperatures below 500°C.

Journal ArticleDOI
TL;DR: Gold was evaporated onto Pt(100) and platinum was evapated onto a single crystal surface as mentioned in this paper, and the (1 × 5) and ( 1 × 7) surface structures can be explained by the formation of a hexagonal top atomic layer on a substrate that retains a square lattice.

Journal ArticleDOI
TL;DR: In this article, the authors described the characteristics and elaboration of polyphenylene oxide films bearing reactive amino functions by the selective electrochemical oxidation of phenol derivatives substituted by amino or anilino groups.

Journal ArticleDOI
TL;DR: In this paper, BF4-doped polypyrrole grown on platinum was used as electrodes in a series of reactions, and they were found to be quite stable and nonporous; they generally do not perturb the redox reactions of dissolved species and they display rapid surface-substrate electron transfer kinetics.
Abstract: Films of BF4-doped polypyrrole grown on platinum, hereafter termed [Pt]polypyrrole, were used as electrodes in a series of reactions. These organic electrodes are found to be quite stable and nonporous; they generally do not perturb the redox reactions of dissolved species and they display rapid surface-substrate electron-transfer kinetics. The polypyrrole films are sensitive to the presence of Lewis bases in solution, which apparently act as nucleophiles, leading to degradation of the electrode properties


Patent
07 Oct 1981
TL;DR: In this article, a process for producing aromatic hydrocarbons by bringing a feedback containing at least 10% w/w of C 2 polycyclic acid (C 2 ) into contact with a catalyst composition comprising a gallium loaded ziolite and a Group VIII metal selected from rhodium and platinum is described.
Abstract: This invention relates to a process for producing aromatic hydrocarbons by bringing a feedback containing at least 10% w/w of C 2 hydrocarbons into contact with a catalyst composition comprising a gallium loaded ziolite and a Group VIII metal selected from rhodium and platinum. The reaction is carried out at a temperature from 500°-750° C. A WHSV of 0.2-10 and a pressure of 1-20 bar are preferred. The presence of Group VIII metal increases conversion of the C 2 feed reduces formation of undesirable polynuclear aromatics.

Journal ArticleDOI
TL;DR: The catalytic activity of the colloidal platinum for light-induced hydrogen evolution from water depends on the particle size of the platinum indicating the maximum activity for the colloid of about 30 A in diameter as discussed by the authors.
Abstract: Well-dispersed fine and stable colloidal platinum is easily prepared by refluxing the solution of chloroplatinic acid in alcohol (and water) in the presence of poly(vinyl alcohol) or polyvinylpyrrolidone under air. The catalytic activity of the colloidal platinum for light-induced hydrogen evolution from water depends on the particle size of the platinum indicating the maximum activity for the colloid of about 30 A in diameter.

Journal ArticleDOI
TL;DR: In this article, the anodic oxidation of formaldehyde in alkaline medium was studied and the influence of electrode material, pH and potential was investigated, showing that methylene glycol anion (CH2OHO−) is dehydrogenated at the electrode surface, yielding adsorbed hydrogen atoms.
Abstract: To elucidate the mechanism of electroless plating solutions with formaldehyde as the reductant, the anodic oxidation of formaldehyde in alkaline medium was studied. The influence of electrode material, pH and potential was investigated. The experimental results can be explained by a mechanism in which methylene glycol anion (CH2OHO−) is dehydrogenated at the electrode surface, yielding adsorbed hydrogen atoms. The atomic hydrogen can either be oxidized to water or be desorbed as a gas. Kinetic rate laws for these two reactions are given. Electroless copper, platinum and palladium solutions behave according to the mechanism.

Journal ArticleDOI
TL;DR: In this article, an evaluation of five Cabot Corporation furnace blacks of widely varying physical and chemical properties, including Vulcan XC-72R, was performed using a cyclic voltammetric technique.
Abstract: In early development of the phosphoric acid fuel cell, the most common carbon support material for the platinum catalyst was a Cabot Corporation furnace black called Vulcan XC-72R. Even though use of this material facilitates dispersion of platinum and electrode fabrication, it is unstable at elevated temperatures and high electrode potentials. At present the main approach to the problem is to heat-treat the Vulcan material or use acetylene black. The present study is an evaluation of five Cabot Corporation furnace blacks of widely varying physical and chemical properties, including Vulcan XC-72R. These studies include an investigation of wetting characteristics, oxygen reduction on platinum supported on these carbons, and a determination of carbon stability using a cyclic voltammetric technique. Carbons with high volatile content and acid pH (Cabot Corporation Mogul 1300, CSX 98 and Mogul L) were hydrophobic and inhibited platinum dispersion. Platinum dispersion was good on Vulcan XC-72R but the platinum sintering rate was high. One carbon (Regal 660R) with a low volatile content and a neutral pH had high platinum dispersion, good electrode performance, a negligible platinum sintering rate and a high resistance to corrosion. It appears to be a potentially useful substitute for Vulcan XC-72R.

Journal ArticleDOI
TL;DR: In this paper, the existence of cis and trans isomers in solution of binary chelates of unsymmetric β-diketones was confirmed by 1H and 13C NMR spectroscopy.
Abstract: A number of palladium(II) and platinum(II) bis-chelates have been prepared which contain one kind of symmetric or unsymmetric β-diketonate anions, or involve two different β-diketonate anions. Existence of the cis and trans isomers in solution of the binary chelates of unsymmetric β-diketones was confirmed by 1H and 13C NMR spectroscopy. Geometrical isomerization of the palladium(II) complexes to attain equilibrium in solution is fast, while the platinum(II) complexes are quite inert. The mixed-ligand chelates are stable in solution, showing no sign of disproportionation. The isomeric pairs of bis(1-phenyl-1,3-butanedionato)palladium(II), bis(2,4-hexanedionato)palladium(II), and bis(1,1,1-trifluoro-2,4-pentanedionato)platinum(II) were isolated, and molecular structure of the cis isomer of the first complex was determined by X-ray analysis.

Journal ArticleDOI
TL;DR: In this paper, a planar magnetron with a zinc target is used to sputter zinc oxide in an oxygen atmosphere, and highly oriented zinc oxide films are obtained on a variety of subtrates such as gold, aluminum, platinum, quartz, and oxidized silicon.
Abstract: A planar magnetron with a zinc target is used to sputter zinc oxide in an oxygen atmosphere. Highly oriented zinc oxide films are obtained on a variety of subtrates such as gold, aluminum, platinum, quartz, and oxidized silicon. The sputtering rate is typically 10–20 μm/h for a substrate temperature of 450–500 °C, a substrate‐to‐target spacing of 4–7 cm, an oxygen partial pressure of 7 μm, and an input rf power of 1–1.25 kW. The films are evaluated by acoustic measurements, x‐ray diffraction, reflection electron diffraction, and scanning electron microscopy.

Journal ArticleDOI
TL;DR: In this paper, the deactivation due to the formation of PtO2 and the oxidation reaction are chemically coupled, and are explained in the same way as in the oxidation of glucose.