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Platinum Metals Rev., 1966, 10, (2), 66

ABSTRACTS: April 1966

of current literature on the platinum metals and their alloys

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PROPERTIES


Electron Density and Electronic Properties in Noble-Metal Transition Elements


m. a. jensen, b. t. matthias and k. andres, Science, 1965, 150, (3702), 1448–1450

It is shown empirically that, for the Pt group metals and their alloys, the superconducting transition temperature, the magnetic susceptibility and the electronic specific heat are adequately described as universal functions of the valence electron density.

Surface Energy and the Secondary Recrystallisation of Platinum Sheet


m. mclean and h. mykura, Acta Met., 1965, 13, (12), 1291–1297

When growth rates of secondary crystals in thin Pt sheet at 1500°C were measured, only crystals with orientations close to {111} were observed to grow. They grew through the polycrystalline matrix at rates dependent on the specimen thickness and their own orientation. Impurities may cause the reduced grain boundary mobility. Contributions to driving pressure for 0.01 cm Pt sheet are: surface, 59%; grain boundary, 62%; impurity drag, −21%. No secondary recrystallisation is predicted for Pt sheet thicker than 0.027 cm. More possible orientations occur with thinner specimens.

The Wetting of Gold and Platinum by Water


k. w. bewig and w. a. zisman, J. Phys. Chem., 1965, 69, (12), 4238–4242

A sessile drop of pure H2O placed on pure, polished Au or Pt spreads spontaneously over the clean surface with zero contact angle but if the surfaces have been contaminated by hydrophobic traces then white heat in a stream of high-purity gas is required previously. Similar traces in the gas may be adsorbed and keep the surfaces non-wetting but, if they are removed in an adsorbent cold trap, the Au and Pt specimens can be wetted completely.

The Pressure Dependency in the Oxidation of Platinum Explained by a Boundarylayer Diffusion Mechanism


g. c. fryburg, Trans. Met. Soc. A.I.M.E., 1965, 233, (11), 1986–1989

Evidence indicates a boundary-layer diffusion mechanism for Pt oxidation above 800°C except at the lowest pressures. The oxidation rate depends on the rate of diffusion of oxide through the boundary-layer away from the Pt, whereas for W and Mo oxidation the rate is controlled by O2 diffusion through the boundary-layer towards the metal. This difference results from the much lower oxidation rate of Pt.

Thermal Diffusivity of Platinum


j. j. martin, p. h. sidles and g. c. danielson, U.S.A.E.C. Rept. IS–1261, 1965, (Oct.), 11 pp

Values for the thermal conductivity of Pt were calculated from diffusivity measurements. They agree with other studies at room temperature but not at high temperature and the use of Pt as a conductivity standard will need additional measurements by absolute methods. Four Pt samples with resistivity ratios of 34, 100, 900 and 5000 were studied at 300–1200°K. Thermal diffusivity values were insensitive to small amounts of impurities.

Magnetic Moments in the Ordered Fe2·8 Pt1·2 Alloy


e. krÉn and p. szabÓ, Solid State Commun., 1965, 3, (11), 371–372

Neutron diffraction measurements on Fe2·8 Pt1·2, which has Cu3Au-type structure, give μFe=3.3 ±0.2 μB and μPt = 1.5±0.2 μB.

Investigation of the Recovery of Atomic Defects in Palladium and Copper-Palladium Alloys


w. köster and h.-p. kehrer, Z. Metallkunde, 1965, 56, (11), 760–767

Studies of the recovery of cold-worked and quenched Pd and Cu-Pd alloys by resistivity measurements at −40 to 300°C showed that Pd recovers in stages III and IV with activation energies of 1.03 ±0.02 eV (stage III after cold working only), due to recovery of interstitial atoms, and 1.50±0.07 eV (stage IV after quenching), due to annihilation of vacancies. Activation energies of the alloys increased with Pd content.

On the Change in the Thermoelectric Power and the Electrical Resistance of Alloys of the Palladium-Silver System in a Transverse Magnetic Field


t. ricker and r. luck, Ibid., 799–802

Studies were made on Pd-Ag, Pd-Rh and Ag-Cd alloys. A cryomagnet for the measurement of galvanomagnetic properties at low temperatures is described. The changes depend on both the magnetic induction and resistivity according to the second power although this is not strictly true in pure metals and in stronger fields.

The Temperature Dependence of the Resistance and Other Electrical Properties of Palladium-Silver and Palladium-Rhodium Alloys


t. ricker and e. pflüger, Ibid., 1966, 57, (1) 39–45

Results for the temperature dependence of the resistance of Pd-Ag and Pd-Rh alloys at 80–1100°K, for the Hall effect in Pd-Ag alloys at 80–400°K and for the Nernst effect in Pd-Ag, Pd-Rh and Pd-Mo alloys at room temperature agree well with an extended model of quasi-free electrons combined with Mott’s picture of electron structure of transition metals. Ag-rich alloys show effects due to change of Debye temperature. The model enables temperature dependence of resistance, thermoelectric power and Nernst effect to be derived from the same density of states function. The concentration dependence of these effects is due essentially to scattering of electrons into the incompletely filled d-band.

Ordered Alloys of Gold-Palladium System. I. Electron Diffraction Study of Evaporated Au3Pd Films


a. nagasawa, y. matsuo and j. kakinoki, J. Phys. Soc. Japan, 1965, 20, (10), 1881–1885

Electron diffraction study of evaporated single crystal films of 10–60 at.% Pd-Au alloys revealed an ordered phase with Cu3Au-type structure at 25 at.% Pd-Au with an order-disorder transformation which occurs at 850°C.

Plastic Deformation of Pd-H Alloys


s. takagi and t. sugeno, Japan J. Appl. Phys., 1965, 4, (10), 772–777

Tensile tests on Pd-H alloys were carried out at various temperatures and strain rates. Hardening of Pd due to H-charging was more pronounced in α- than in β-phase. In polycrystalline d-alloys the temperature and concentration dependence of yield stress were measured at −80 to +130°C and indicated that hardening was dominated by the chemical interaction. Low H2-concentration specimens at liquid H2 temperatures had serrated stress-strain curves (the Portevin-Le Chatelier effect) but why is not known.

Absorption Isotherms of Hydrogen in the α-Phase of the Hydrogen-Palladium System


j. w. simons and t. b. flanagan, J. Phys. Chem., 1965, 69, (11), 3773–3781

Absorption isotherms were determined at 0–90°C from variations in the electrode potential and electrical resistivity of Pd wires during slow absorption of H2 from dilute HCl solutions, and represent equilibrium data. Average isosteric heat of absorption is 4780±100 cal/mole of H2 from H-Pd=0.002 to 0.014. Statistical analysis of the isotherms is based on interacting absorbed protons.

The Plastic Deformation of Iridium Single Crystals


r. haasen, h. hieber and b. l. mordike, Z. Metallkunde, 1965, 56, (12), 832–841

The critical shear stress of zone-refined Ir single crystals has temperature dependence similar to that of impure Cu and Ag. Activation energy is 1.2 eV and initial activation volume is 2.5.10−19 cm3. Stacking fault energy is estimated to be γ=296±59 erg/cm2, i.e. more than other noble metals and comparable to that of Ni, i.e. dislocations are practically undissociated. Elastic and plastic parameters of Ir show quantitative agreement of mechanical properties with other f.c.c. metals if the characteristic deformation stresses are related to shear modulus, which for Ir is very high and limits its range of plasticity. The influence of impurities is still apparent and yet more so in polycrystalline Ir.

Establishment of Two New Compounds IrBi3 and IrBi2 in the System Bismuth-Iridium


n. n. zhuravlev and e. m. smirnova, Kristallografiya, 1965, 10, (6), 828–832

IrBi3 has rhombic crystals isomorphous with NiBi3. IrBi2 has monocyclic crystals isomorphous with α-RhBi2 and possesses arsenopyrite structure.

The Reaction of Niobium with Ruthenium


l. a. pantaleimonov, o. p. nesterova, z. a. guts, k. g. akhmetzyanov and i. g. sokolova, Vest. Moskov. Univ., Ser. II, Khim., 1965, (6), 57–62

NbRu melts at 1900°C, the eutectic point occurs at 1760°C, 66 at.% Ru and there is a minimum in the solidus curve at 1800°C, 40 at.% Ru. This minimum and that of the isotherm of electrical resistivity and of the temperature coefficient of resistance, the maximum of the hardness curve and the b.c.c. lattice to tetragonal lattice transition all occur at ∼40% Ru.

The Reaction of Ruthenium with Tantalum


l. a. pantaleimonov, o. p. nesterova, k. g. akhmetzyanov and i. g. sokolova, Ibid., 63–68

The Ru-Ta system has a eutectic point at 1950°C, 70 at.% Ru, a minimum in the solidus curve at 1970°C, 44–45 at.% Ru and RuTa melts at 2050°C. The maximum in the hardness curve and the b.c.c. to tetragonal lattice transition also occur at 44–45 at.% Ru.

On the Occurrence of Some U2X Compounds of Uranium with Transition Metals


a. f. berndt and a. e. dwight, Trans. Met. Soc. A.I.M.E., 1965, 233, (12), 2075–2078

The stoichiometrically prepared compounds U2Tc, U2Rh, U2Os and U2Ir, formed by peritectic or peritectoid reactions, are isostructural with U2Ru. Lattice parameters and miscibility relationships are listed.

New T3B7 Compounds


f. hulliger, Nature, 1966, 209, (5022), 500–501

New compounds synthesised include Ir3Ga4Ge3, Ir3In4Sn3, Ir3Ga3Ge4, Ir3Ga3Sn4, Ir3In3Ge4, Ir3In3Sn4, Mo3Sb7, OsIr2Sn7, Tc3As7, Re3As7.

The Occurrence of Superconductivity in Sulphides, Selenides, Tellurides of Pt-group Metals


c. j. raub, v. b. compton, t. h. geballe, b. t. matthias, j. p. maita and g. w. hull, J. Phys. Chem. Solids, 1965, 26, (12), 2051–2057

Superconductivity occurs in Pd-Se and Pd-Te compounds, in IrTe3 and in PtTe. 85-87 at.% Pd-Se alloys have Tc =0.66°K, which is unusually high for its valence-electron concentration. Homogeneity ranges exist for hexagonal B8-type PdTe and for trigonal C6-type PdTe2. Low temperature heat capacity measurements for PdTe and PdTe1·04 show that large changes of Tc with composition are accompanied by large changes in linear heat capacity coefficient γ.

CHEMICAL COMPOUNDS


Platinum Carbonyls Substituted by Tertiary Phosphines


g. booth, j. chatt and p. chini, Chem. Commun., 1965, (24), 639–640

A series of quite stable trinuclear Pt carbonyl derivatives was produced by substitution of tertiary phosphines and also a less well-defined polymeric dicarbonyl [Ptn(CO2)n]. Ease of preparation fell when methyl groups replaced phenyl groups. Structures, melting points and some other properties are tabulated. Those derivatives which contain triangles of Pt atoms are the first to be reported.

Rhodium Sulphate Complexes


s. i. ginsburg and n. n. chalisova, Zh. Neorg. Khim., 1965, 10, (11), 2411–2417

Thermogravimetric, polarographic and potentiometric studies of the synthesis of Rh sulphates show that the mononuclear aquohydroxysulphate is formed at room temperature with single bonds which readily split in aqueous solution. At 100–125°C the sulphate is more complex with double bonds and Rh: SO4 = 2:3. At 250–325°C the stable trisulphate is formed with triple bonds and Rh: SO4 = 1:3.

Chemical and Structural Characterisation of Some π -Allylic Derivatives of Rhodium(III)


g. paiaro, a. musco and g. diana, J. Organomet. Chem., 1965, 4, (6), 466–474

RhCl3.3H2O and trans,trans,trans -1,5,9-cyclododecatriene react in boiling C2H3OH to form insoluble red diamagnetic dichloro(cyclodeca-1,5-dienyl)rhodium(III), which is polymeric through Cl bridges and which reacts with Lewis bases to give octahedral derivatives such as C12H19RhCl2B2 where B is monodentate basic ligand.

Ionisation and Dissociation of Ruthenium and Osmium Tetroxides


j. g. dillard and r. w. kiser, J. Phys. Chem., 1965, 69, (11), 3893–3897

Principal ions from ionisation and dissociation of RuO4 and OsO4 by electron impact were determined by mass spectrometry and their heats of formation were obtained. MO2 is formed by dissociative electron attachment; MO and MO3 are produced by ion-pair formation processes. I (RuO4) = 12.33±0.23eV, I (OsO4) = 12.97± 0.12eV, D (O-RuO2) = 104 kcal/mole and D (O-OsO3) = 108 kcal/mole.

ELECTROCHEMISTRY


Nature of the Surface of a Platinum-Rhodium Alloy in Electrocatalysis


a. damjanovic, a. dey and j. o’m. bockris, J. Catalysis, 1965, 4, (6), 721–724

Steady state potential-log rate relationships for the electrochemical oxidation of H2O to O2 and for the cathodic reduction of O2 to H2O in 1 N HClO4 and in 1 N KOH, plotted for Rh, Pt and 40% Rh-Pt, show that the reactions on the alloy follow the kinetic characteristics of whichever pure metal has the faster rate at a given electrode potential, indicating the possibility that the homogeneous alloy substrate has become a heterogeneous mixture of the metal oxides and therefore a type of polyelectrode.

Anodic Corrosion of Rhodium in Hydrochloric Acid Solutions


j. llopis, i. m. tordesillas and m. muñiz, Electrochim. Acta, 1965, 10, (11), 1045–1055

Anodic corrosion of Rh in HCl by action of dc occurs with high overpotential and Rh(III) complex formation (yellow solutions) and it is enhanced by increasing temperature and HCl concentration. Superimposed ac increases the attack and at low overpotentials raspberry-red Rh(III) solutions are obtained; ac effect increases as frequency decreases. For a given dc value no apparent corrosion occurs until a threshold iac≫idc is reached. Order of corrosion resistance is Rh<Pt ≪Ir.

Oxygen Overvoltage on Bright Palladium in Acid Solutions


j. p. hoare, J. Electrochem. Soc., 1965, 112, (11), 1129–1133

Galvanostatic and potentiostatic overvoltage measurements of anodic evolution and cathodic reduction of O2 on bright Pd electrodes in O2-saturated 2 N H2SO4 gave generally similar kinetic results. Pd catalysed peroxide decomposition less well than Pt. Adsorbed PdO film was a poor electronic conductor. O2 was evolved anodically on a Pd anode by decomposition of PdO2 to PdO and O2. O2 was reduced from adsorbed O2 molecules on a Pd cathode.

On the Adsorption Properties of Rhodium and Ruthenium Electrodes in Relation to Electrolytes


g. p. khomchenko, a. f. lunev and k. n. bogdanovskaya, Elektrokhimiya, 1965, 1, (11) 1352–1355

Adsorption properties of Rh and Ru electrodes depend on the electrolytes in relation to the potential. Comparison of their properties of gas adsorption and retention demonstrates the roles of the ionic double layer and of the potential drop at the metal-solution grain boundary. Just as the Pt surface is fully degasified in the double layer potential region so on Rh is an insignificant amount of gas present, whose atoms have dipole bonding with the metals.

New Method of Dissolving Ruthenium


a. a. goryunov and a. n. ryabov, Zh. Neorg. Khim., 1965, 10, (12), 2596–2601

The anodic dissolution of Ru powder in an alkaline medium to obtain a concentrated solution of ruthenates and perruthenates of the alkaline metals, free from extraneous salts, occurs efficiently and relatively quickly in a described cell.

ELECTRODEPOSITION AND SURFACE COATINGS


Investigation of Electrolytic Mixed Deposits of Platinum and Palladium with Ruthenium


o. a. petrii and v. e. kazarinov, Elektrokhimiya, 1965, 1, (11), 1389–1391

Ru-Pt and Ru-Pd deposits on Pt from 1% [x H2PtCl6+y K2RuNOCl5] and 1% [x PdCl2 + y K2RuNOCl5] solutions were checked for thickness and composition by radioactive labelling of K2RuNOCl5. The amount of Ru is proportional to the amount in solution until secondary factors cause its value to pass through a maximum. Mixed electrolytic deposits containing 5–80% Ru have high chemical stability and are more active for catalytic and electrochemical processes than the metallic alloys.

LABORATORY APPARATUS AND TECHNIQUE


Diffusion-Sorption Pumping


p. l. read and h. h. glascock, J. Vacuum Sci. Technol., 1965, 2, (6), 307–308

Pressure in a small system was reduced from 760 Torr to 1 × 10−8 Torr by using H2 diffusion through a 25% Ag-Pd foil combined with the sorption of gas on liquid-N2-chilled synthetic zeolite. This is a useful technique for a forepump in getter-ion-pumped ultra-high vacuum systems. Ag-Pd alloy is used because pure Pd might crack during thermal cycling.

Hydrocarbon-leak-detector Tool Contributes to Cleaner Air


Oil Gas J., 1965, 63, (48), 65

Esso Research and Engineering Co have developed a leak detector for hydrocarbons with a sensing head containing shielded and unshielded Pt wires. When gaseous fumes reach the less-shielded wire the Pt catalytically raises the burning of the gases and also changes the circuit resistance to alert the operators. Use of the device at Humble’s Bayway Refinery, Linden, N.J., has reduced hydrocarbon leakage to the sewers, and air and water pollution.

CATALYSIS


Platinum-based Reforming Catalysts


j. tomasik and j. wrzyszcz, Chem. Stosowana, 1965, 9, (2A), 205–216

Tests on catalysts containing 0.1–1.0 at.% Pt for both low and high pressure reforming show that the amount of Pt does not affect the isomerisation activity but that it affects the degree of conversion and the aromatisation. These data can be used in optimising Pt content of industrial contact catalysts.

Changes of the Aromatisation Property of Platinum-Alumina Catalyst in Relation to the Content in it of Platinum and Sodium


n. r. bursian, s. b. kogan and z. a. davydova, Kinetika i Kataliz., 1965, 6, (6), 1046–1051

The aromatisation of N-hexane at 545°, atm. pressure over Pt/Al2O3 catalysts with 0.01–1.2 wt.% Pt and 0.02–1.6 wt.% Na and the conversion of N-hexene-1 over Al2O3 were studied in the same conditions. Possible mechanisms for alkylaromatic hydrocarbon formation were examined. A scheme for conversion of N-hexane over Pt/Al2O3 with parallel formation of aromatic hydrocarbons on Pt and acid centres is proposed. Optimum Na concentration depended on the Pt content of the catalyst.

Development of a Mathematical Description of Platforming for Optimisation of the Process. I.


yu. m. khorov, g. m. panchenkov, s. p. zel’tser and yu. a. tirak’yan, Ibid., 1092–1097

This mathematical model of platforming takes account of the catalyst and of the composition of the input material and its fractions. Determinations of the reaction parameters show good agreement between calculation and experiment.

The Production of High Octane Petrol by Catalytic Reforming


g. n. maslyanskii, r. f. pannikova and g. d. kamusher, Khim. i Tekhnol., Topliv i Masel, 1965, (12), 1–6

Catalytic reforming of a wide range of petroleum fractions can be carried out at 20 atm without regeneration of the catalyst for many months. The use of Pt catalysts with high selectivity increases the yields of high-octane petrol and of H2. Fractions evaporating in the ranges 85–140, 85–180, 105–140 and 105–180°C, which contain 60% paraffins can be reformed to 95 octane petrol with a yield between 78.7% and 85.7% compared to the original composition. H2 yield is 1.5–1.8%.

Catalytic Oxidation of Ammonia on Platinum


e. j. nowak, Chem. Engng. Sci., 1966, 21, (1), 19–27

The kinetics and mechanism of NH3 oxidation on Pt or Pt alloy screens and gauzes are discussed with respect to new data on heat and mass transport compared with those for a single infinite circular cylinder. The adequacy of mass transport for a solely heterogeneous mechanism is indicated. Effects of catalyst shape and roughness together with analysis of earlier data suggest that catalyst losses during commercial oxidation are due to oxidative volatilisation of Pt.

The Mechanisms of Hydrogenolysis and Isomerisation of Hydrocarbons on Metals. I. Hydrogenolysis of Cyclic Hydrocarbons


g. maire, g. plouidy, j. c. prudhomme and f. g. gault, J. Catalysis, 1965, 4, (5), 556–559

Product distribution for hydrogenolysis of methylcyclobutane and of various substituted cyclobutanes and cyclopentanes on metal films depends on the metal, on the temperature and on ph2; on the corresponding metal/Al2O3 it depends on metal concentration. At high temperatures on Pt and Pd films and on low content Pt/Al2O3 and Pd/Al2O3 it is typical, denoting equal chances of breaking the cyclic bonds; π -allylic triadsorbed species are involved in the inferred mechanisms. On 10% Pt/Al2O3 or Pt film, or on Ni, only disecondary CH2-CH2 cyclic bonds of cyclobutanes and cyclopentanes are broken; α,α,β,β-tetrasorbed species are involved in the suggested mechanism. Distributions from methylcyclo-pentane on Pt/Al2O3 and the dependency of methylcyclobutane hydrogenolysis on Pt films point to another mechanism. Similar distributions on films to those on supported catalysts indicate no catalytic effect by the carrier.

The Effect of Deformation on Catalytic Activity of Platinum in the Decomposition of Hydrogen Peroxide


k. b. keating, a. g. rozner and j. l. youngblood, Ibid., 608–619

The decomposition of 0.3% H2O2 on annealed and cold-worked Pt foils is first order. The rate constant increases with cold working. The catalytic activity of Pt and its deformation are related directly. Increased activity seems due directly to deformation since possible effects of preferred orientation and of increased surface were proved negligible.

Catalytic Conversions of 1,4-Endomethylenespiro-(5,5)-undecane on Platinum Catalyst


n. v. elagina, a. k. mirzaeva, kh. e. sterin, a. v. bobrov and b. a. kazanskii, Neftekhimiya, 1965, 5, (5), 671–675

Final products (wt.%) of the catalytic conversion with Pt/C at 320°C are 2,3-benzbicyclo-[1,2,3]-octane and 2,3-benzbicyclo-[0,3,3]-octane, (50); 1-methyl-3-phenylcyclopentane, (11); benzyl-cyclopentane, (9); monoalkylbenzenes, (7).

Hydrogenation of 2-Methyl-5-acetylfuran on Platinised Carbon in a Flow System under Pressure


n. i. shuikin, g. k. vasilevskaya and i. f. bel’skii, Izv. Akad. Nauk S.S.S.R., Ser.Khim., 1965, (11), 2029–2032

The reaction was studied at 200–220°C. Changing from 1 to 50 atm. did not affect the reduction of the carbonyl group nor hydrogenolysis of the furan ring but increased the degree of hydro-genisation of the hydrogenolysis products.

Kinetic Regularity of the Isomerisation Reaction of n -Pentane on Platinum Catalysts


n. r. bursian and n. k. volnukhina, Zh. Prikladnoi Khim., 1965, 38, (10), 2273–2278

The rate of n -C5H12 isomerisation is directly proportional to up to 10 atm when is 30 atm from 15 to 75 atm. The rate is inversely proportional to from 15 to 75 atm when is 10 atm, and from 60 to 90 atm when pc5h12 is 10 atm. Changes of working pressures between 15 and 100 atm do not affect the rate of n -C5H12 isomerisation if does not exceed 10 atm. Studies establish that adequate activity and stability of the Pt/SiO2-Al2O3 catalyst for the industrial process occur at: working pressure, 35–40 atm; 10 atm; , 25–30 atm, which are the optimum conditions.

The Conversion of cis -8-Methylhydrindane in the Presence of Platinised Carbon


e. s. balenkova, n. a. khafizova and s. i. khromov, Neftekhimiya, 1965, 5, (6), 797–800

Pt/C catalysed the conversion at 300°C of cis -8-methylhydrindane with the formation of o -xylene, o -methylethylbenzene, o -methylpropylbenzene, indane, and 1- and 4-methylindane. This shows that some methyl groups were split off during aromatisation and that methyl radicals also exchanged positions with neighbouring C atoms.

Activation Energy of Crystalline Catalysts


li ven’-chzhou, a. n. mal’tsev and n. i. kobozev, Zh. Fiz.Khim., 1965, 39, (11), 2704–2707

Pt black is 140 times more active than thin Pt layers for the strongly exothermic oxidation of C2H5OH to CH3COOH (Qp = 117 kcal/mol). Moderately exothermic reactions exhibit less activation of Pt atoms in the lattice. Results confirm that the Pt crystals account for the energy of the reaction by the way in which catalyst atoms act as acceptors of energy when the reaction occurs at active centres.

Effect of Exposure on the Catalytic Activity of Platinum during Hydrogenation


i. v. krylova, a. p. filonenko and n. i. kobozev, Ibid., 2742–2744

Exposure of Pt catalysts to light from mercuryquartz lamps caused increased activity for hydrogenation of cyclohexene but preliminary illumination decreased activity for reduction of nitro groups (e.g. in nitrophenol) and for H2O2 decomposition. Tested were Pt/SiO2 and Pt black.

The Oxidative Coupling of Aromatic Compounds with Palladium Salts


r. van helden and g. verberg, Rec. Trav. Chim., 1965, 84, (9–10), 1263–1273

C6H6, PdCl2 and CH3COONa react in CH3COOH to produce biphenyl in high yield but no reaction occurs in the absence of CH3COONa. A mixture of isomeric biphenyls is obtained from mono-substituted benzenes. Steric effects affect the reaction with disubstituted benzenes, e.g. 3,4,3′,4′,-and 2,3,3′,4′-tetramethylbiphenyl were obtained from o -xylene in ratio 2.7:1. The assumed mechanism involves complex formation between the aromatic compound and PdCl2, then π-cyclohexadienyl-PdCl2 formation by reaction between the complex and acetate ions, and decomposition to biphenyl and Pd metal.

The Oxidation of Propylene by Palladium Chloride in Acetic Acid


a. p. belov, g. yu. pek and i. i. moiseev, Izv. Akad. Nauk S.SS.R., Ser. Khim., 1965, (12), 2204–2206

C3H6 oxidised by PdCl2 in glacial CH3COOH forms iso-, cis-n- and trans-n -propenylacetates, the respective alkylidenediacetates and small amounts of allylacetate.

Organic Syntheses by means of Noble Metal Compounds. XI. Copolymerisation of Carbon Monoxide and Norbornadiene


j. tsuji and s. hosaka, J. Polymer Sci., Part B, Polymer Letters, 1965, 3, (9), 703–707

Norbornadiene and CO react in C6H6 to form a 1:1 copolymer in the presence of a catalytic amount of PdCl2, which is the first copolymerisation of CO and olefins catalysed by a transition metal compound to be reported.

XVI. Carbonylation of Allene-Palladium Chloride Complexes


j. tsuji and t. susuki, Tetrahedron Letters, 1965, (34), 3027–3031

Structures of substances prepared by carbonylation of allene-PdCl2 were identified and the mechanisms are discussed.

XVII. Reaction of π-Allylpalladium Chloride with Nucleophiles


j. tsuji, h. takahashi and m. morikawa, Ibid., (49), 4387-4388

π-Allylpalladium chloride reacts smoothly with ethyl malonate and acetoacetate to form ethyl allylmalonate and ethyl diallylmalonate. Enamines react similarly with the complex. Thus carbanions can attack the C atom of the Pd complex to give allyl derivatives in high yield. Acetate and alcoholate anions react with the complex to give allyl acetate and ether in low yield.

XX. Decarbonylation of Acyl Chloride and Aldehyde Catalysed by Palladium and its Relationship with the Rosenmund Reduction


j. tsuji, k. ohno and t. kajimoto, Ibid., (50), 4565–4568

Olefin was formed from acyl chloride with evolution of CO and HCl in the presence of metallic Pd from PdCl2 decomposed by heating, e.g. decanoyl chloride treated thus formed nonene isomers. Thus Pd catalyses both carbonylation of olefin to acyl halide and decarbonylation of acyl halide to olefin. Decarbonylation of aliphatic aldehyde to form a mixture of olefin and the corresponding paraffin also occurred, e.g. decanal to nonane and nonene. A mechanism for the olefin-CO reaction in the presence of Pd is proposed; connection with the Rosenmund reduction (acyl halide into aldehyde) is established.

XXI. Decarbonylation of Aldehyde Using Rhodium Complex


j. tsuji and k. ohno, Ibid., (44), 3969–3971

Chlorotris(triphenylphosphine)rhodium was converted into chlorocarbonylbis(triphenylphosphine)rhodium by reaction with aldehydes even at room temperature and thus aldehydes were decarbonylated smoothly into corresponding paraffins.

The Transannular Addition of Carbon Monoxide to Cyclo-octa-1-5-diene


s. brewis and p. r. hughes, Chem. Commun., 1966, (1), 6–7

Pd complexes catalyse this reaction, e.g. cycloocta-1,5-diene in tetrahydrofuran reacted with CO at 150°C, 1000 atm in the presence of 1% diiodobis(tributylphosphine)palladium(II) to give 40–45% yield after 8 h of bicyclo-[3,3,1]-non-2-en-9-one. Some 45–50% cyclo-octa-1,3-diene was obtained.

Homogeneous Catalytic Hydrogenation of Ethylene and Acetylene with Four-Coordinated Iridium and Rhodium Complexes. Reversible Catalyst-Substrate Adducts


l. vaska and r. e. rhodes, J. Am. Chem. Soc., 1965, 87, (21), 4970–4971

The trans -[MX(CO)(Ph3P2] complexes, where M=Ir, Rh and X = halogen, catalyse reactions of C2H4, C3H6 and C2H2 with H2 in C6H6 or C6H5CH3 solutions at subatmospheric pressure and 40–60°C. These systems combine the features of: catalyst complexes with known compositions, properties and structures; Ir complexes reacting reversibly with 1 mol.H2/complex; the H2 adducts [H2IrX(CO) (Ph3P)2], which have been isolated, characterised, and their molecular consfigurations established; Ir complexes reacting reversibly with C2H4, C2H2 etc. at ambient conditions.

The Isomerisation of Cyclo-octadienes Catalysed by Rhodium, Iridium and Platinum Complexes


j. k. nicholson and b. l. shaw, Tetrahedron Letters, 1965, (39), 3533–3535

During the preparation of [RhCl(C8H12)]2 from cycloocta-1,5-diene and RhCl3 all the uncomplexed olefin is converted to the 1,3-isomer and much of the 1,4-isomer is formed as an intermediate. In the reaction of chloroiridic acid with 1,5-C8H12 to give [IrHCl2(C8H12)]2 all the uncomplexed olefin is converted into 1,3-C8H12. Tertiary phosphine complexes also isomerise 1,5-C8H12 to 1,3-C8H12, e.g. [Ir HCl2(PEt2Ph)3] at 130°C gives 90% conversion after 120 min. [Ir Cl3(PEt2Ph)3] is five times less effective. Diethylphenylphosphine inhibits the isomerisation. [RhCl3(PEt2Ph)3] is also a good catalyst but trans -[PtHCl(PEt3)2] and trans -[PdI2(PMe2Ph)3] are poor. A high yield of catalyst can be recovered from 1,3-C8H12.

The Isomerisation of Octenes Catalysed by Phosphine Complexes of Iridium(III)


r. s. coffey, Ibid., (43), 3809–3811

Similar work to the preceding abstract has been carried out with Ir complexes on octene isomerisation.

Polymerisation by the Derivatives of Transition Metals. III. Competitive Action of Different Ligands on the Stereospecific Polymerisation of Butadiene by Rhodium Salts in Aqueous Emulsion


p. teyssie and r. dauby, Bull. Soc. Chim. France., 1965, (10), 2842–2848

Rh salts catalyse the sterospecific polymerisation of butadiene in aqueous emulsion to give only the poly-trans-1,4 isomer. The reaction is coordinated polymerisation. Very active catalyst systems (Rh-cyclohexadiene) were discovered and the possibility of polymerising butadiene and piperylene simultaneously.

Hydrogenation of Aromatic Amines on Ruthenium Catalysts


a. s. chegolya, n. s. smirnova, b.i. zhizdyuk, l. m. ryshenko, g. i. golub and a. a. ponomarev, Zh. Org. Khim., 1965, 1, (10), 1868–1871

The activity and stability of Ru catalysts were studied during liquid phase hydrogenation of aromatic amines under pressure. Conditions for stereospecificity during the hydrogenation of 1,4-phenylenediamine to trans -1,4-diaminocyclohexane with high yield over RuO2 were established.

Oxidation of Sugars with Ruthenium Dioxide-Sodium Periodate: A Simple Method for the Preparation of Substituted Keto Sugars


v. m. parikh and j. k. n. jones, Canad. J. Chem., 1965, 43, (12), 3452–3453

Substituted keto sugars as intermediates in the synthesis of antibiotic agents are prepared by combining the two steps of the previous method into one, whereby RuO4 oxidant is formed from RuO2 and then oxidises the alcohol to the sugar. Advantages include nearly quantitative sugar yields, use of only trace quantities of RuO2, time-saving and destruction of impurities in the starting material.

Homogeneous Hydrogenation and Hydroformylation Using Ruthenium Complexes


d. evans, j. a. osborn, f. h. jardine and g. wilkinson, Nature, 1965, 208, (5016), 1203–1204

The Ru(II) complexes RuCl2(PPh3)4 and RuCl2 (PPh3)3 dissociate in C6H6 solutions. Olefines and acetylenes such as hept-1-ene and hex-1-yne are hydrogenated rapidly by the complexes at 25°C, 1 atm in C6H6/C2H5OH solution. Ru(CO)3(PPh3)2 in 10−2 M C6H6 at 100 atm of CO:H2(1:1) gives 80% yield of hexaldehydes from pent-1-ene in 15 h, and is the first case of a Ru complex hydroformylation.

FUEL CELLS


The Electrochemical Oxidation of Hydrocarbons on a Tantalum-supported Platinum Catalyst


r. thacker, Electrochem. Technol., 1965, 3, (11–12), 312–316

Teflon-bonded Pt/Ta cathodes with 9 mg Pt/cm2 were used in the oxidation of C2H6, C3H8, C2H4, C3H6 and n -C4H10 gases, and n -C5H12 and CH3OH vapours, with 14.6 M H3PO4 electrolyte immobilised on an asbestos matrix, at 150°C. Cells with higher Pt content on the cathode had been preferred for oxidation of C6H8. Rest potential and polarisation behaviour is discussed.

Electrochemical Energy Conversion in a Palladium Hydrogen Diffusion Electrode


h. j. cleary and n. d. greene, Electrochim. Acta, 1965, 10, (11), 1107–1115

Current densities of 165 mA/cm3 were achieved at 30°C on Pd-H diffusion wall electrodes after pretreatment by abrading and oxidising in air at 800°C. H2 transport is governed by solid-state diffusion. H2 diffusion in β-Pd is expressed by Dβ =3.8 × 104− exp (−2930/RT).

CATHODIC PROTECTION


Anode Design for Shipboard Cathodic Protection


r. l. benedict, Materials Protection, 1965, 4, (12), 36–38

Effective protection depends on the shape and voltage of the anodes and on their area. They should be located where mechanical abrasion of paint is unlikely to occur. Platinised Ti, and Pb anodes with Pt micro-electrodes are most effective and should last the life of the ship.

GLASS TECHNOLOGY


A Wide Range (up to 1010P) Rotating Cylinder Viscometer


a. napolitano, p. b. macedo and e. g. hawkins, J. Res. N.B.S., Sect. A, Phys. Chem., 1965, 69A, (5), 449–455

Three techniques enable the range of this viscometer (described in Platinum Metals Rev., 1963, 7, (2), 54–55) to be extended up to 1010P. At 10° − 105P the outer Pt cylinder is rotated at constant speed and the torque measured on the inner Pt bob. From 104.5 to 107.5P the bob is rotated through an angle and timed as it returns to its zero position. From 105.5 to 1010P the bob is driven through an angle at constant torque and is timed as it does so.

TEMPERATURE MEASUREMENT


Reference Tables for Platinum-40% Rhodium/Platinum-20% Rhodium Thermocouples


r. e. bedford, Rev. Sci. Instrum., 1965, 36, (11), 1571–1580

Tables in the range 0–1880°C are based on calibrations in air of ten thermocouples from four wire lots at the freezing points of Zn, Sb, Ag and Au; the melting points of Pd and Pt by the wire method, and from comparison with standard Pt:10%Rh-Pt and 5%Rh-Pt:20%Rh-Pt thermocouples at 0–1750°C. Test thermocouples are intercompared at 0–1850°C. A.P.H. Report No. 1292 gives more detailed tables.

Measurement and Control of Gas Temperature in the FINGAL Process


m. n. elliott and j. r. grover, Br. Chem. Engng., 1965, 10, (12), 846–849

The design of a bare wire Pt:13% Rh-Pt thermocouple is described for measurement of off-gas temperatures in the FINGAL process, developed at Harwell for the incorporation of highly radioactive fission product wastes in glass. A similar thermocouple is used with a suction-type pyrometer for gas temperatures in the process vessel.

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