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Platinum Metals Rev., 1977, 21, (4), 138

Abstracts of current literature on the platinum metals and their alloys

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PROPERTIES

The Relation Between Adsorption and Catalysis Centres of the Surface of a Platinum Sponge

r. e. mardaleishvili, zh. ya. smorodinskaya and d. mink, Dokl. Akad. Nauk S.S.S.R., 1977, 233, (5), 911–914

The number of catalytic centres on Pt sponge (37.3g sample) was determined by studying the hydrogenation of C2H4 at 75−245°C and 50–300 torr. The results show that the number of catalytic centres on the Pt sponge was (0.92±0.03)×1020 which is in good agreement with the number derived from adsorption experiments (1.03±0.03)×1020. This suggests that the adsorption and catalytic centres are of the same nature.

Study of Simultaneous Adsorption of Hydrogen Peroxide and Some Organic Acids on Platinum by Impulse Methods

t. m. semenkina, g. i. elfimova, g. a. bogdanovskii and g. d. vovchenko, Zh. Fiz. Khim., 1977, 51, (5), 1194–1197

The simultaneous adsorption of H2O2 and organic acids (acetic, n- and iso-butyric, iso-valeric) on Pt was shown to occur on the same Pt centres. The acids have an inhibiting effect on the decomposition rate of H2O2.

Chemisorption of Nitrogen on Platinum {111}: Reflection-Absorption Infrared Spectroscopy

r. a. shigeishi and d. a. king, Surface Sci., 1977, 62, (2), 379–385

Nitrogen adsorption on a {111} oriented Pt ribbon was studied under ultra-high vacuum conditions. The activation energy for desorption was found to be 40kJ/mole at 120K. The initial sticking probability at this temperature was found to be 0.15 and the maximum uptake was∼1.1×1014 molecule/cm2.

Photoelectron Spectroscopic Studies of the Chemisorption of Ethylene and Halo-substituted Alkenes on the (100) and (111) Crystal Surfaces of Platinum and a General Model for the Dissociation of Unsaturated Molecules at Surfaces

r. mason, m. textor, y. iwasawa and i. d. gay, Proc. R. Soc. A, 1977, 354, (1667), 171–196

X-ray and ultraviolet photoelectron spectroscopy were used to study the chemisorption of ethylene and halogen-substituted alkenes on the Pt(100) and Pt(111) surfaces. The results show that the initial dissociation of the vinyl halides at sub-monolayer coverage is followed by an associative mechanism at higher coverages. A statistical model explaining the differing reactivities of the alkenes on the two types of surfaces is proposed.

The Influence of Alloying on the Heat Resistance of Platinum Alloys

e. i. rytvin, Izv. Vysshikh Ucheb. Zaved., Tsvetnaya Metallurgia, 1977, (2), 125–129

The influence of Ru, Rh, Ir, Au and Pd alloying additions on the heat resistance of binary Pt alloys was studied by measuring their creep rate in air and in molten glass at a stress σ=0.5kg/mm2 at 1200−1700°C. The results show that alloying Pt with Ru, Rh and Ir considerably lowers the creep rate and increases the time to failure. Alloying Pd does not give a strengthening effect. Alloying with 5% Au lowers the creep rate from 76 to 12%/h andincreases the time to failure from 0.5 to 2.5h at 1400°C and stress σ=0.5kg/mm2 in air.

Investigations of Metal Catalysts. X. Characterisation of Pt-M Catalysts (M:Fe, Co, Ni). XI. Investigations on Pt-η-Al2O3 Catalysts Modified by Iron, Cobalt and Nickel

s. engels and l. lehmann, Z. Anorg. Allgem. Chem., 1977, 431, 181–190, 191–200

X-ray powder methods, magnetic studies and measurements of dispersity were used to characterise the phase structure and dispersity of carrier-free P-M bimetallic catalysts (M=Fe, Co, Ni) respectively. Pt-M/η-Al2O3 catalysts were studied by magnetic investigations, reflectance spectra and determination of dispersity. The phase structure of Pt-rich catalysts was found to be of Pt3Fe superstructure to a high degree. All the Pt-Fe/η-Al2O3 catalysts contained Fe111 ions in octahedral symmetry. (54 Refs.)

Studies of the Properties of Calcium and Platinum Oxide Compounds

m. lugowska and i. lazarska, Przem. Chem., 1977, 56, (3), 143–145

Studies of the properties of Pt and Ca oxide compounds formed on Ca sieves during recovery of Pt used in nitric acid production were carried out. The results showed a high instability of the bond between CaO and PtO2 and a tendency to form compounds with a lower CaO content. Thermal stability of the compound was studied at 700−900°C. Further studies at pilot scale are suggested to ascertain losses from the above reaction during Pt recovery on the Ca filters.

Oxygen Penetration into the Bulk of Palladium

c. t. campbell, d. c. foyt and j. m. white, J. Phys. Chem., 1977, 81,(5), 491–494

Studies of O2 interaction with polycrystalline Pd showed that above 250°C a significant amount of O2 penetrates into the bulk at pressures below the dissociation pressure of PdO. The uptake rate of O2 began to decline after about 100 monolayers of O2 were incorporated.

Thermodynamic Properties of Hydrogen in Palladium and Its Alloys under Conditions of Constant Volume

w. a. oates and t. b. flanagan, J. Chem. Soc., Faraday Trans. I, 1977, 73, (7), 993–1002

Thermodynamic properties of H/Pd and its alloys were studied experimentally under conditions of constant alloy volume. It is shown that the phase change α→β1, which is characteristic of Pd/H no longer appears under condition of constant volume. This shows that long range dipole-dipole elastic interactions are predominant inthis system.

Adsorption and Absorption of Hydrogen by Thin Palladium Layers

r. v. bucur, Surface Sci., 1977, 62, (2), 519–535

Kinetic analysis for the sorption mechanism of H2 by a Pd layer is presented. Kinetic relationships describing the time dependence of the atomic fraction 0 during the sorption were obtained by direct integration of the differential balance equations.

Chemical Reactions on Palladium Surfaces Studied with Pd-MOS Structures

i. lundström, m. s. shivaraman and c. svensson, Surface Sci., 1977, 64, (2), 497–519

The catalytic reactions on Pd and Pt surfaces were successfully studied with metal-oxide-semiconductor structures. The hydrogen induces a flatband voltage shift at the metal-oxide interface, which is a measure of the amount of H2 in the metal. The Pd film acts like a selective H2 filter enabling the determination of participating species in the surface reaction in a very simple way.

A Conjecture on a Possible Relation Between the 55K Heat Capacity Anomaly in Palladium Hydride and the Modification of the Vibrational Spectrum of Palladium

g. boureau and o. j. kleppa, Scripta Metall., 1977, 11, (4), 327–329

The calorimetric measurements and lattice dynamics studies were used to explain the heat capacity anomaly at 55K in the Pd-H system. It is proposed that this anomaly may be caused by a displacement of the Pd atoms. This suggestion may have important consequences in the interpretation of superconductivity in these alloys.

Adsorption of NO and CO on a Ru Surface

r. ku, n. a. gjostein and h. p. bonzel, Surface Sci., 1977, 64, (2), 465–483

The chemisorption of NO and CO on a Ru surface was studied by LEED, AES and thermal desorption spectroscopy. The results show that NO adsorbs and rapidly dissociates into separate N and O adsorbed phases with ordered C(2×4) and (2×1) structures, respectively. CO was found to adsorb in a molecular state and does not form an ordered structure. The results are discussed in terms of the catalytic reduction of NO by H2 and CO.

CHEMICAL COMPOUNDS

A Structural Model for Barium Platinum Oxide, Ba3Pt2O7

p. s. haradem, b. l. chamberland, l. katz and a. gleizes, J. Solid State Chem., 1977, 21, (3), 217–223

Crystal structure studies of Ba3Pt2O7 show it to have a hexagonal cell of dimensions a=10.109Å and c=8.638Å, space group P 62c and Z=4. Pt occupies mainly the face-sharing octahedra. The Pt-O bond length was found to be 2.00Å and the three long Pt-O distances 2.65Å.

Covalent Transition Metal, Lanthanide and Actinide Tetrahydroborate Complexes

t. j. marks and j. r. kolb, Chem. Reviews, 1977, 77, (2), 263–293

A comprehensive review of synthetic methods and chemical properties of known tetrahydroborates, including Au and Pt group metal tetrahydroborates is presented. Structural studies of these compounds were carried out using vibrational spectroscopy and nuclear magnetic resonance. The geometric parameters associated with the metal-ligand interaction are derived and the bonding in covalent metal tetrahydroborates in relation to their physical and chemical properties is discussed. (213 Refs.)

The Addition of Alkyl Halides to Rhodium (I) Dithiolene Complexes. The Synthesis, Structure and Chemical Properties of Rhodium (III) Acyl Species

c.-h. cheng, b. d. spivack and r. eisenberg, J. Am. Chem. Soc., 1977, 99, (9), 3003–3011

The synthesis and characterisation of a series of anionic and neutral Rh(III) acyl complexes by i.r. and 1H NMR spectroscopy are presented. The structure of a representative member of the series (R=Et) was determined by single crystal X-ray diffraction. The complex (AsPh4)[RhI(COEt)(PPh3)(mnt)] crystallises in space group P2 1/a(C2h5) in a cell of dimensions a=18.466, b=13. 608, c=19.088Å, β=106.39° with four molecules/unit cell.

Stereospecific Exchange of Carbon Monoxide in Clusters of the Type Os(CO)10X2

e. g. bryan, b. f. g. johnson and j. lewis, J. Chem. Soc., Chem. Comm., 1977, (10), 329–330

Compounds of the type Os3(10)10X2, where X=Cl, Br, I and OEt, have been studied by 13CO NMR techniques. It was found that stereospecific exchange of labelled CO takes place on the non-unique Os atoms. Carbonyl bridging between the different types of Os atoms does not take place.

ELECTROCHEMISTRY

XPS Spectroscopic Study of Potentiostatic and Galvanostatic Oxidation of Pt Electrodes in H2SO4 and HClO4

j. s. hammond and n. winograd, J. Electroanal. Chem. Interfacial Electrochem., 1977, 78, (1), 55–69

X-ray photoelectron spectroscopic studies of the surface oxides produced by potentiostatic and galvanostatic oxidation of Pt electrodes in HClO4 and H2SO4 were carried out. The oxide species produced as the initial oxidation product by successively more anodic potentiostatic oxidation in 0.2M HClO4 is found to have a Pt2+ oxidation state and a limiting thickness of 8Å. Galvanostatic oxidation in HClO4 and H2SO4 produced PtO2.H2O as an unlimiting growth oxide.

Kinetics and Mechanism of Oxygen Film Electroformation up to a Monolayer Thickness at the Pt/KHSO4 (Melt) Interface and Its Relation with the Electroreduction Process

j. o. zerbino, n. r. de tacconi, a. j. calandra and a. j. arvia, J. Electrochem. Soc., 1977, 124, (4), 475–480

The electrochemical reactions occurring at the Pt/KHSO4(melt) interface were studied, and the potentiodynamic E/I response of the interface under various O2 potentials and under different perturbation conditions. A reaction model involving different surface species gives a satisfactory explanation of the anodic and cathodic experimental results.

The Anodic Evolution of Oxygen on Iridium Oxide Electrode

c. iwakura, h. tada and h. tamura, Denki Kagaku, 1977, 45, (4), 202–206

The anodic evolution of O2 on the Ir oxide electrode prepared by thermal decomposition of IrCl4 on a Ti substrate, was studied in acidic and alkaline solutions. The mechanistic parameters and the overall current densities for O2 generation were determined. It was shown that the rate-determining step in the acidic solution was a chemical reaction whereas in the alkaline solution it was an electrochemical reaction. The O2 overvoltage was very high in neutral solutions.

Oxide Stability and Chemisorption Properties of Supported Ruthenium Electrocatalysts

k. kinoshita and p. n. ross, J. Electroanal. Chem. Interfacial Electrochem., 1977, 78, (2), 313–318

The analysis of Ru oxides observed on Ru supported graphitised C black and a comparison of both electrochemical and gas-phase chemisorption measurements were carried out using CO and H2 for determining Ru surface areas. The results showed that RuO2 formed on supported Ru electrocatalysts by heating in air was difficult to reduce by electrochemical treatment in 1M H2SO4, but could be reduced by heating in H2 at 200°C. The RuO2 produced during an anodic potential sweep in H2SO4 to 1.3V could be reduced to Ru during the subsequent cathodic sweep to 0.

LABORATORY APPARATUS AND TECHNIQUE

Catalysts in Action

r. t. k. baker, Chem. Engng. Progress, 1977, 73, (4), 97–99

A new technique, controlled atmosphere electron microscopy, was developed to study reactions between gases and solidsat very high magnifications, while they are taking place. The technique was used to study the growth of Pt particles supported on γ-Al2O3. It was found that the presence of Cl ions tends to suppress the growth of Pt on Al2O3.

Determination of Platinum in Sands by Flameless Atomic Absorption Using the HGA-2100

a. tello and n. sepulveda, At. Absorp. Newsl., 1977, 16, (3), 67–69

A method for the determination of Pt in beach sands from the south of Chile, using atomic absorption and a graphite furnace is discussed. The use of the graphite furnace was found to improve the sensitivity of determination. It was shownthat the concentration of HCl does not affect the results. The reproducibility and accuracy were found satisfactory for the studied range of 0.02μg Pt/ml−1.00μg Pt/ml.

Palladium and Titanium Thin Films as Probes for Determination of Hydrogen in Helium

r. r. olsen and v. s. srinivasan, Anal. Chem., 1977, 49, (6), 853–857

Studies of the utility of a thin film of Pd in the detection and determination of H2 gas in a He atmosphere under ambient conditions showed that the response of Pd to H2 was different under unannealed and annealed conditions. Un-annealed films responded irreversibly to H2 to a lower limit of 20 ppm, while conditioned filmsresponded from <1% to 5% (w/w) of H2.

HETEROGENEOUS CATALYSIS

New Hydrogenation Catalysts with Platinum Deposited on Polyamide-66. VI. Activity and Selectivity in the Hydrogenation of Styrene and Cyclopentadiene

j. -r. bernard, c. hoang-van and s. j. teichner, J. Chim. Phys., 1977, 74, (4), 475–480

Studies of the activity and selectivity of Pt/polyamide-66 catalysts were carried out during hydrogenation of styrene and cyclopentadiene using a reaction scheme of the “rake” type. The results showed that the adsorption-desorption equilibria of unsaturated hydrocarbons on Pt/nylon catalysts are displaced towards the desorption thus favouring the production of an intermediate compound in successive hydrogenation reactions. The observed modifications of the catalytic properties of Pt/nylon are explained by a partial electron transfer from the polyamide support acting as an electron donor, towards the incomplete inner electron shell of Pt.

The Catalytic Decomposition of Formaldehyde on Palladium

g. ertl and j. tornau, Z. Phys. Chem. (Frankfurt ), 1977, 104, (4–6), 301–308

Spectroscopic studies of the decomposition of formaldehyde at a clean Pd surface of polycrystalline wire were carried out in a UHV flow system. The thermal desorption experiments showed that desorption takes place at higher temperatures than if present alone on the surface. The desorption energy of H2 increased by the interactions between Had and COad. A reaction scheme is proposed whereafter desorption of the products is rate-determining.

Noble Metal Catalysis. IV. Products from Benzyl Alcohol Decomposition

d. m. fenton, e. r. fett and e. c. schluter, J. Appl. Chem. Biotechnol., 1977, 27, (6), 281–290

Benzyl alcohol disproportionates to benzaldehyde and toluene in the presence of Pd, Rh or Ru chloride catalysts. The results show that the benzaldehyde can either decarbonylate to benzene or disproportionate to benzyl benzoate. The order of catalyst activity is: Pd>Rh>Ru. Benzyl alcohol also dehydrogenates to benzaldehyde or dehydrates to dibenzyl ether. The order of catalyst activity is then: Ru>Rh>Pd.

Adsorption of Hydrogen on Skeleton Rhodium, Ruthenium and Rhodium-Ruthenium Catalysts

t. m. grishina, v. v. zhuchkova, g. d. vovchenko and e. v. sukhanovskaya, Zh. Fiz. Khim., 1977, 51, (5), 1257

The adsorption of H2 on skeleton Rh, Ru and 5−60 at.% Ru-Rh catalysts was studied using the charging curves method. It is shown that the adsorption ability of the catalysts with respect to H2 in 1N H2SO4, decreases with increase in Ru.

Vapour Phase Carbonylation of Methanol at Atmospheric Pressure in the Presence of a Rhodium Catalyst. II. Rhodium Chloride on Alumina

a. krzywicki and g. pannetier, Bull. Soc. Chim. Fr., 1977, (1/2), 64–68

Studies of the vapour phase carbonylation of methanol were carried out over Rh chloride supported on η-Al2O3 at atmospheric pressure. The catalytic activity depended on the Rh concentration on the Al2O3 surface. Methyl iodide in the reacted mixture was found to affect the carbonylation of methanol only when its concentration was quite low.

Methane On-site as a Nuclear Power Station Spin-Off

h. webster, Processing, June 1977, 28, 30

Methane can be synthesised from carbon dioxide and hydrogen in the presence of a Ru/α-Al2O3 catalyst. The stages in the development of such a methanation process, which resulted in the successful commissioning of four patented plants at Hinkley Point and Hunterston nuclear power stations, are outlined.

Study of the State and Behaviour of Hydrogen on Ru Catalysts

r. v. dmitriev, n. d. zubareva, a. a. vedenyapin, e. i. klabunovskii and kh. m. minachev, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1977, (5), 986–991

Adsorption, thermodesorption and isotopic methods were used to study the state of H2 on the surface of Ru/Al2O3, Ru/SiO2 and Ru-black catalysts. It was found that H2 is adsorbed very strongly on the surface of these catalysts and can be removed only at high temperatures. The specific adsorption of H2 is highest on the Ru/Al2O3 and lowest on the Ru-black catalyst. The H2 adsorbed on Ru can migrate on its surface and exchange with the OH groups of the carrier.

The Activity of Supported Ruthenium-Palladium Catalysts in Hydrogenation and Isomerisation of Hexene-1

d. v. sokol’ skii, t. m. dukhovnaya and k. k. dzhardamalieva, Zh. Fiz. Khim., 1977, 51, (5), 1118–1121

The hydrogenation and isomerisation of hexene–1 was carried out over 1% Pd, Ru and Ru–Pd catalysts supported on TiO2, ThO2 and activated C, in 96% ethanol at 20−40°C. It is shown that Ru-Pd catalysts are 1.5–2 times as active as Pd catalysts and 10–15 times as active as Ru catalysts. The Ru-Pd/TiO2 and Ru-Pd/ThO2 are 2–3 times as active as the Ru-Pd/C catalysts. The highest isomerisation activity was found for Pd catalysts.

Carbon Supported Ruthenium-Palladium Catalysts, in Hydrogenation of Dimethyl-ethinylcarbinol

d. v. sokol’ skii, k. k. dzhardamalieva, t. m. dukhovnaya and sh. d. dinasylova, Zh. Fiz. Khim., 1977, 51, (5), 1115–1117

The hydrogenation of dimethylethinylcarbinol was carried out over Ru-Pd/C catalysts in ethanol, H2O and KOH. The results show that most active are catalysts containing 10−20% Ru and 80−90% Pd. The rate of hydrogenation in ethanol is 2–3 times higher than in H2O and in 0.1N KOH. The activity was found to depend on the type of carrier used, and changed in the order: C<Al2O3<BaSO4<TiO2<ThO2.

HOMOGENEOUS CATALYSIS

Homogeneous Catalytic Hydrogenation of Unsaturated Carboxylic Acid Esters with H2PtCl6+SnCl2 in iso-Butanol

w. strohmeier and l. weigelt, Z. Naturf. B, 1977, 32, (5), 597–598

Studies of the catalytic system, prepared from H2PtCl6+SnCl2.2H2O and theadditives HBr and H2O in iso-butanol showed it to be a very efficient catalyst for homogeneous hydrogenation of unsaturated esters under mild conditions. Reaction rates up to 40 m Mol/1 min and turnover numbers UZ higher than 1600 were observed.

Synthesis and Reactions of and Catalytic Homogeneous Hydrogenation by Chlorocarbonyl(o -(diphenylphosphino)-N,N -dimethylaniline)iridium(I) and Chlorocarbonyl (o -(diphenylphosphino)-N,N -dimethylbenzylamine) iridium(I)

t. b. rauchfuss, j. l. clements, s. f. agnew and d. m. roundhill, Inorg. Chem., 1977, 16, (4), 775–778

The preparation of complexes IrCl(CO)PN and IrCl(CO)PCN where PN is o -(diphenylphosphino)–N,N –dimethylaniline and PCN is o –diphenylphosphino)–N,N –dimethylbenzylamine is described. The complexes react with HCl and with a mixture of Mel and iodide. They also catalyse the hydrogenation of hexene–1 with the following effectiveness: IrCl(CO)PCN>IrCl(CO)PN>IrCl(CO)(PPh3)2.

CHEMICAL TECHNOLOGY

Rhenium Activated Sintering

r. m. german and z. a. munir, J. Less-Common Metals, 1977, 53, (1), 141–146

The influence of Pd, Pt, Cr, Mn, Fe and other additives on the sintering process of Re was studied at 1000−1400°C in dry H2. The results show that at 1000°C, only Pt acts as a sintering enhancer, but at 1400°C, both Pt and Pd provide appreciable sintering enhancement.

Efficient Maintenance of Platinum Milling Tools

m. lorenz, Metall, 1977, 31, (6), 636–638

The application of new grinding machines using B nitride and diamonds as grinding agents was found to improve the maintenance of Pt milling tools. The economical aspects of this improvement are discussed.

ELECTRICAL AND ELECTRONIC ENGINEERING

Performance Review of Thick Film Materials

j. d. provance, Insulation/Circuits, 1977, 23, (4), 33–36

A review of materials used in the thick film hybrid microcircuitry is presented. The advantages of Pt-Ag conductors which are readily soldered and do not form oxide films during firing, are discussed. New and improved Au, Pt-Au and ternary compositions of Pt-Pd-Ag conductors with high conductivity, high adhesion and ease of soldering and their applications in automotive voltage regulators, digital watches and circuits for communication systems are considered.

Structural and Electrical Characteristics of Platinum-Silicide-Silicon Contacts as Influenced by Sputter Etching and Annealing Ambient

m. severi, e. gabilli, s. guerri and g. celotti, J. Appl. Phys., 1977, 48, (5), 1998–2003

Studies of the influence of the surface-cleaning procedure and the annealing ambients on the structure of the Pt-silicide and on electrical properties of the resulting Schottky barrier showed that the annealing ambient is a dominant factor for the silicide formation. The results show that sputter etching is necessary for obtaining of nearly ideal and reproductible electrical characteristics and in order to ensure a silicide formation, vacuum annealing must be performed.

Thick Film Adherence Fracture Energy: Influence of Alumina Substrates

p. f. becher and j. s. murday, J. Mater. Sci., 1977, 12, (6), 1088–1094

Studies of the adherence of a glass bonded Pt-Au thick film conductor to various Al2O3 substrates show that the adherence is degraded by changes in the surface composition and by the presence of (0001) crystallographic texture in the substrate. The results show that the critical fracture energy was reduced from a maximum of 3.7 J/m2 using an as-received 96+wt.% Al2O3 substrate to ∼2 J/m3 using an as-received 99+wt.% Al2O3. The changes in the crystallographic texture of the substrate and in the glass layer diminish the interpenetrating nature of the glass-metal interface and cause poorer thick film adherence.

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