Platinum Metals Rev., 1970, 14, (4), 147
ABSTRACTS: October 1970
of current literature on the platinum metals and their alloys
Effect of Grain Size on the Creep of Platinum-Rhodium Alloys
i. i. novikov, f. s. novik, e. i. rytvin, s. s. prapor and i. f. pruzhinin, Izv. Vysshikh Ucheb. Zaved., Tsvet. Metall., 1970, (3), 110–113
Models are described for estimation of the rate of creep of 7−10% Rh-Pt alloys at 1300°C, applied pressure 1.0−1.3 kg/mm2 and grain sizes from 0.4 to 2.8 mm.
Deviations from Matthiessen’s Rule in Dilute Gold and Platinum Alloys
r. g. stewart and r. p. huebener, Phys. Rev. B, 1970, 1, (8), 3323–3338
Positive deviations Δ(T) from Matthiessen’s rule have been observed in several dilute Au and Pt alloys (solute concentration ≈0.1−5 at.%). Δ(T) ∝ log T for Au-Co and Pt-Rh at 30−200 K. Δ(T) has a sharp peak at 30−50 K for the low solute concentrations. Results are interpreted in terms of the two-band model, the anisotropy of the electron scattering, and the shift in the Fermi surface due to alloying.
Vacancy Formation and the Thermal Expansion of Platinum
j. van den sype, Scripta Metall., 1970, 4, (4), 251–254
The measurement of the coefficient of thermal expansion of Pt at 1000−1900 K is discussed. Measurement by optical comparison and by a direct method agree well at 1000−1400 K. Above 1400 K increasing deviation is in evidence, amounting to 26% at 1900 K. The deviation is explained on the basis of a vacancy relaxation effect inherent in the temperature technique for measuring thermal expansion.
Internal Friction in the Equiatomic Alloy CoPt
w. chomka, j. belson, p. eurin and j. paulevÉ, C. R., Sér. C, 1970, 270, (24), 2042–2044
Internal friction observed in CoPt during annealing is very sensitive to changes caused by magnetoelastic effects, which are affected by the induced magnetism and by the degree of ordering of CoPt.
Specific Heat and Electrical Resistivity of Exchange-enhanced Dilute Pt-Ni Alloys
c. a. mackliet, a. i. schindler and d. j. gillespie, Phys. Rev. B, 1970, 1, (8), 3283–3290
The specific heat and electrical resistivity of dilute Pt-Ni alloys were measured at 1.2−4.2 K. Specific heat results fitted C=γT+β ′T3 and resistivity fitted ρ=ρ 0+AT2. Experimental results are used to evaluate current theories of localised spin fluctuation effects.
On the Structure of the Platinum-Copper-Zinc Composition
y. khan, b. v. r. murty and k. schubert, J. Less-common Metals, 1970, 21, (3), 293–303
Structural analysis of the Pt-Zn-Cu system showed its brass-like properties. Both the valence-electron and the core-electron spatial correlations affect the alloy structure.
Field-electron Microscope Study of Pt-Ba Alloy
yu. v. zubenko and n. p. esaulov, Fiz. Tverd. Tela, 1970, 12, (3), 852–855
An emission image of the surface of single crystals of 1.3 wt.% Ba-Pt was obtained. The formation of an adsorbed Ba film on the alloy surface was studied visually during thermal treatment.
The X-ray Structural Investigation of Pt-Ba and Pd-Ba Alloys in the Region of the Compositions Pt5Ba and Pd5Ba
n. n. zhuravlev, n. p. esaulov and i. v. rall’, Kristallografiya, 1970, 15, (2), 374–376
Pd5Ba and Pt5Ba are isomorphous with CaCu5-type structure. X-ray studies of Pt5Ba variously heat-treated show that it is stable over a wide range of temperature, whereas Heumann claimed that it was stable only at high temperatures.
Hydrogen Solubility in Electrolytically Deposited Thin Films of Palladium
r. v. bucur and l. stoicovici, J. Electroanal. Chem. Interfac. Electrochem., 1970, 25, (2), 342–343
The quantity of H2 absorbed in electrodeposited thin films of Pd in equilibrium at atm. pressure was determined in 0.1 M H3PO4 solution at 25°C. For a compact Pd or Pd black film the H2 solubility r is 0.564± 0.003; r is less for bright films and is very sensitive to heating. Use of a Pt anode in the electrodeposition of bright films results in an increase in H2 solubility above the reference value.
Non-linear Magnetisation of Pd
f. a. muller, r. gersdorf and l. w. roeland, Phys. Lett. A, 1970, 31A, (8), 424–425
The non-linear magnetisation of Pd at 4.2 K was determined in semi-continuous fields up to 325 kOe. For the expression M=χH(1+β H2), β =–(9.5±1.7)×10−8m2/A2. Measurements were repeated with a Pt sample where χβ =(0±3)×10−21m2/A2 compared with (10±1.8)×10−21 m2/A2 for Pd.
Elastic Constants of Monocrystalline Alloys of Pd-Rh and Pd-Ag between 4.2 K and 300 K
e. walker, j. ortelli and m. peter, Ibid., (5), 240–241
The elastic properties of six monocrystalline Pd-Rh and Pd-Ag alloys were measured. Results are presented graphically and agree with the theoretical model predicting a correlation between susceptibility and elastic modulus.
Volume and Shape Magnetostriction of Alloys of Pd-Rh and Pd-Ag at 4.2 K
r. keller, j. ortelli and m. peter, Ibid., (7), 376–377
Longitudinal and transverse magnetostriction of Pd-Rh and Pd-Ag alloys was measured in fields up to 50 kG. Values of the magnetostrictive coefficients Sv and Sf are presented graphically and are interpreted in terms of a band model.
Optical and Photoemissive Properties of Palladium in the Vacuum Ultraviolet Spectral Region
r. c. vehse, e. t. arakawa and m. w. williams, Phys. Rev. B, 1970, 1, (2), 517–522
Optical properties of evaporated films of Pd at 10−8 torr were studied at 2–24 eV. Results are correlated with the photoemissive properties of similar samples for photon energies of 10.2–22.4 eV. Interband transitions are identified from the optical data at 1.3, 3.6, 15.2, and 20.5 eV; at 7.3 and 7.6 eV peaks appear in energy loss functions −Im[1/(ε+1)] and −Im[1/ε], respectively.
Giant Moments of Dilute Fe in Binary and Ternary Pd Alloys
r. p. guertin and s. foner, J. Appl. Phys., 1970, 41, (3), 917–918
The saturated local moment psat and the ordering temperature Tc of very dilute (≈1000 p.p.m.) Fe in Pd alloys were measured at low temperature. Alloy systems included Pd1−xAx, where A=Rh, Ag, Pt, or Ni, and Pd1−2xRhxAgx. Psat and the high-field matrix susceptibility χHF were also measured at 1.2−4.2 K up to 60 kG; psat was not simply related to χHF.
Magnetic Field Dependence of the Specific Heat of Dilute Pd-Co, Pt-Co and Pd-Mn Alloys
b. m. boerstoel and c. van baarle, Ibid., 1079-1080
The specific heat of Pd-Co-type alloys was measured at 1.2−30 K in external fields of up to 30 kOe; field strength greatly influenced the excess specific heat. A comparison between Pd and Pt alloys emphasised the smaller exchange enhancement in Pt. Results for dilute alloys of Mn in Pd differed greatly from those for Co or Fe in Pd.
The Mechanism of Ordering of Alloys with Periodic Antiphase Domain Structure
l. n. buinova, v. i. syutkina, o. d. shashkov and e. s. yakovleva, Fiz. Metal. Metalloved., 1970, 29, (6), 1221–1230
Results of electron microscope studies of the dislocation structures of deformed Cu-Pd alloys with regard to the reported ordering mechanism show that, in alloys with a large number of antiphase domain boundaries, ordering mechanisms connected with the movement of pair dislocations have no place.
Low-temperature Specific Heat Study of Cu-Pd Alloys
y. sato, j. m. sivertsen and l. e. toth, Phys. Rev. B, 1970, 1, (4), 1402–1410
Variations with composition of the electronic specific heat γ and Debye temperature θD were determined for Cu-Pd alloys from specific heat measurements at 1.5−4.2 K. Deviations from a rigid-band model were observed for small Pd concentrations. Thermodynamic properties are discussed in terms of the band structure from γ values. Changes in long and short range order have pronounced effects on γ and θD values.
Magnetic Properties of Mn and Fe in CuPd and AgPd
b. dellby and h. p. myers, J. Appl. Phys., 1970, 41, (3), 1010–1011
The magnetic susceptibility of 0.1−1.0 at.% Mn and of dilute solutions of Fe in CuPd and AgPd was measured. Results were interpreted in terms of s-d exchange scattering of conduction electrons at the resonance bound d electrons of Mn, Fe and Pd. This supports a model for AgPd and CuPd with Pd in resonant bound states for low Pd concentrations and in energy band states for high Pd concentrations.
Effect of Atomic Ordering on the Magnetic Structure of the MnPd3 Phase
e. kren, g. kadar and l. pal, Ibid., 941–942
Neutron diffraction and magnetic susceptibility measurements for ordered and disordered MnPd3 confirmed an antiferromagnetic configuration for 23−30 at.% Mn. The angle ϕC of the magnetic moment to the tetragonal axis was 0° below 25% and 90° at higher concentrations. ϕC was order-dependent at 25% and increased from 0 to 90° with decreasing order. A decrease in the Néel temperature with decreasing order was also observed.
High Temperature Creep of Rhodium
v. i. shalaev, i. b. tkachenko, v. a. pavlov, n. i. timofeev and a. v. gushchina, Fiz. Metal. Metalloved., 1970, 29, (5), 1601–1068
Studies of the creep of 99.98% Rh in vacuum at 630−1770°C, 0.4−46.2 kg/mm2 showed that the activation energy QC of creep is 91 kcal/mole, agreeing well with estimates of the activation energy QSD of self-diffusion. It follows from the practical agreement in size of QC and QSD that self-diffusion in Rh controls the rate of deformation during the steady stage of creep.
Electrical Resistance Measurements on Pd Base Alloys
a. m. schiffrin, Phys. Status Solidi, 1970, 39, (2), K81–K83
The effect of the presence of 4f magnetic impurity atoms on the electrical resistivity of Pd was investigated at 1.4−60 K. A well defined resistivity minimum exists at ∼15 K for 8.9 at.% Gd-Pd with a maximum at ∼5 K. This was correlated with magnetic ordering in the alloy.
Magnetic Properties of the Nickel-Rhodium System
e. r. katz, U.S. Rept PB 187,924, 1969, 159pp
Magnetisation and magnetic resonance studies on Ni-Rh alloys, which are ferromagnetic for >63 at.% Ni and paramagnetic for lower Ni concentrations, were compared with data of other workers. A model similar to the Anderson model of dilute magnetic alloys explains all the data qualitatively.
Properties of the Ni-Ir System
e. bucher, w. f. brinkman, j. p. maita and a. s. cooper, Phys. Rev. B, 1970, 1, (1), 274–277
Measurements of the lattice parameters, electronic specific heat, magnetic susceptibility and Debye temperature in 0−100 at.% Ir-Ni showed no ordering or decomposition after annealing for several days at 500−1100°C. A sharp peak occurred in the electronic specific heat/concentration curve at 85 at.% Ni, together with a weak anomaly in the T3 term of the low temperature specific heat. Susceptibility was measured on the paramagnetic side only up to 79 at.% Ni, where a spontaneous moment developed at low temperatures.
The W-Re-Ir Composition Diagram
e. m. savitskii, m. a. tylkina and l. l. zhdanova, Izv. Akad. Nauk S.S.S.R., Metally, 1970, (3), 181–183
The W angle of the W-Re-Ir system was studied and ordering was investigated throughout the system. Ternary alloys which are α-solid solutions are produced at high temperatures. From them can be produced bars, wires and sheet by hot working, wire drawing and rolling respectively.
On the Composition and Thermodynamics of the Uranium-Ruthenium-Carbon System
h. holleck and h. kleykamp, J. Nucl. Mater., 1970, 35, (2), 158–166
The U-Ru-C phase diagram was established at 1300°C using arc-melted and sintered samples of different compositions. The system has two ternary solid phases: U2RuC2 and URu3Cx, where xmax≈0.7. Values of the Gibbs free energy of formation are given, and confirmation of the reaction UC+3Ru→URu3Cx+(1−x)C.
Activation of the Sintering of Tungsten by Platinum-group Metals
g. v. samsonov, Poroshkovaya Metal., 1970, (1), 37–44
Studies of the effect of stable electron configuration of Rh, Pd, Os, and Ru as activators for sintering of W powder compacts at 1000−2000°C showed that it was due to localisation of non-localised electrons from the W atoms in the nuclei of the Pt-metal atoms, thereby promoting mutual dissolution. Activation rose in the order Os, Ru, Rh, and Pd.
Activation of Nitrogen by Transition-metal Complexes
g. martino and l. sajus, Rev. Inst. Fr. Petrole, 1970, 25, (1), 36–45
The synthesis and properties of many N-containing complexes of Ir, Os, Rh, and especially Ru are described.
On the Chemistry of Ruthenium
e. schleitzer, Chem. Z., 1970, 94, (6), 189–192
Ru nitrosyl complexes are important in the reprocessing of used nuclear fuels. Aqueous Ru(III) chloride solution contains complexes of the type [RuXn(H2O)6−n]3−n with n = 1−6, and X=Cl, Br, I, BF4, or PF6. Ru and Ru-chloro complex hydrogenation catalysts are discussed.
Properties and Reactions of Ruthenium(II) Amine Complexes
p. c. ford, Coordination Chem. Lett., 1970, 5, (1), 75–99
The synthesis, properties and reactions of a large number of Ru(II) complexes with N-containing ligands are described. Complexes with and without π-acceptor ligands, with N2, N-heterocycles, organonitriles, and with nitrosyls are considered, as are substitution and redox reactions peculiar to the complexes.
Electrical Transport Properties of IrO2 and RuO2
w. d. ryden, a. w. lawson and c. c. sartain, Phys. Rev. B, 1970, 1, (4), 1494–1500
Electrical resistivities of single crystals of RuO2 and IrO2 were measured at 10−1000 K. Hall constants were obtained at 77 and 300 K. The temperature dependence of the resistivity is explained in terms of electron-photon and electron-electron interband scattering.
Thermal Conductivity and Lorenz Ratio of RuO2
j. millstein, J. Phys. Chem. Solids, 1970, 31, (4), 886–887
Thermal conductivity and Lorenz ratios of very pure RuO2 crystals were investigated. Conductivity/temperature curves show that α=8.42×10−4 cm deg K1−n/W, β = 18.1 cm deg K2/W, and n=1.66. At low temperatures the Lorenz ratio reached a constant value of (2.60±0.1)×10−8 WΩ/deg K2, which is close to the theoretical value of 2.45×10−8 WΩ/deg K2.
Refinement of the Crystal Structure of Ruthenium Dioxide
c.-e. boman, Acta Chem. Scand., 1970, 24, (1), 116–122
RuO2, which has a rutile structure, crystallises in space group p42/mnm of the tetragonal system. The unit cell contains two formula units, and has dimensions a=4.491, c=3,106 Å and V=62.68 Å3.
Precision Determination of the Crystal Structure of Osmium Dioxide
OsO2 has a rutile structure crystallising in space group p42/mnm of the tetragonal system with two formula units per unit cell. Unit cell dimensions are a=4.500 Å, c=3.183 Å, and V=64.48 Å3.
Some New Organometallic Compounds of Osmium Tetracarbonyl
f. l’eplattenier, Chimia, 1970, 24, (4), 151–152
The reactions of Os carbonyl compounds with H2 and allyl halides were studied. Dialkyl complexes, e.g., cis -Os(CH3)2(CO)4 and cis -Os(C2H5)2(CO)4, were isolated and their structures and spectral were determined. Their reactions with CO at elevated temperature and pressure were studied; the former was converted to Os(CO)5 and the latter to cis -Os(COC2H5)2(CO)4.
The Oxidation of Hydrazine in Alkaline Solution at Platinum and Mercury
j. a. harrison and z. a. khan, J. Electroanal. Chem. Interfac. Electrochem., 1970, 26, (1), 1–11
The mechanism of N2H4 oxidation in alkaline solution was investigated at Pt and Hg. On Pt the oxidation is a surface process involving a fast three-electron transfer preceding a one-electron rate-determining step. The reaction is fourth order in HO−.
Hydrogen Sorption by Palladium in Hydrazine Electro-oxidation
n. v. korovin and b. n. yanchuk, Electrochim. Acta, 1970, 15, (4), 569–580
The amount of H2 absorbed by Pd in N2H4 electro-oxidation increases with anodic polarisation. H2 is present in Pd after N2H4 electro-oxidation at high positive potentials, (up to 1.0 V). H2 is an intermediate product of N2H4 electro-oxidation and is probably produced by the decomposition of intermediate radicals.
On the Interaction of Carbon Monoxide with an Iridium Electrode Catalyst
a. b. fasman, g. l. padyukova and d. v. sokol’skii, Elektrokhimiya, 1970, 6, (6), 832–834
Charging curves were obtained at 20, 30, 50, and 70°C for Ir electrodes in 1 N H2SO4 in the presence of H2. CO reduces the Slade potential more than with Pt or Rh.
Electrosorption of Molecular Oxygen from Aprotic Solvents on Noble Metal-Mercury Alloys
w. lund and m. e. peover, J. Electroanal. Chem. Interfac. Electrochem., 1970, 25, (1), 19–25
Chronocoulometry shows that O2 is adsorbed on alloys of Hg with Pt, Au, Ir, and Rh from solutions in acetonitrile, dmf and dms reaching 200−800 μC/cm2. Adsorption depends on alloy composition, electrode potential and O2 concentration. Double layer capacity increases with alloy formation.
ELECTRODEPOSITION AND SURFACE COATINGS
Internal Stresses of Platinum Coatings on Titanium
LABORATORY APPARATUS AND TECHNIQUE
An Automatic Spherical High Temperature Adiabatic Calorimeter
f. r. sale, J. Phys. E, Sci. Instrum., 1970, 3, (8), 646–650
The calorimeter, which was developed for determination of specific heats and enthalpies of transformation of Fe alloys at 650−1750 K, has ±1.2% reproducibility and ±1.5% absolute accuracy for an enthalpy of transformation of 923 J/g.atom at 1184 K. Energy is supplied to the specimen by a small 10% Rh-Pt immersion heater which also supports the specimen in the inner spherical chamber. Temperature distribution in the calorimeter is measured with Pt:10% Rh-Pt thermocouples at the poles and equators.
Production of Micro-steam Quantities for Dynamic Gas Flow Reactors
m. landau, m. j. langford and g. sniezo-blocki, Chem. & Ind., 1970, (May 2), 591–592
A cell capable of giving as little as 3 ml of steam per minute was constructed using Pt wire electrodes wound on glass formers to electrolytically convert water to H2 and O2, and Pt/asbestos to catalytically recombine them as steam as near as possible to the reactor to be dosed with gas of consistent composition.
Here’s How New Platforming Catalysts Are Performing
e. a. sutton, Oil Gas J., 1970, 68, (20), 100–108
Summaries are given of results for four commercial operations using the U.O.P. R-16 Re-Pt catalyst and for one using the U.O.P. R-20 catalyst. The advantages of both are given and results are compared. Both allow greater throughput and increased operating severity with higher yields of reformate and aromatics. Regeneration is less frequent and catalyst investment is reduced. R-20 has a significant selectivity advantage in favour of Platformate and aromatic yields.
Production of Petrol with Octane Number 95 at Industrial Catalytic Reforming Plant
d. v. ivanyukov, e. f. kaminskii, g. n. maslyanskii, a. p. fedorov, r. n. shapiro, v. v. shipikin and v. yu. georgievskii, Khim. Tekhnol., Topliv Masel, 1970, (3), 1–5
A reforming unit was modernised by replacing F-promoted AP-56 catalyst with AP-64 Cl-promoted Pt/Al2O3, which has superior stability, activity and selectivity.
Isomerisation of n -Butenes and n -Butane in the Presence of Group VIII Metals on Aluminium Oxide
g. m. panchenkov, g. s. volokhova and yu. m. zhorov, Neftekhimiya, 1970, 10, (2), 178–182
Group VIII metals are active in the double bond and cis-trans isomerisations of n -C4H8 and of n -C4H10. Activity for skeletal isomerisation varied in the order Co<Ni<Rh<Fe<Pd<Pt. The most active catalysts for hydrogenation were Rh/Al2O3 and Platforming catalyst (Pt/Al2O3).
Conversions of C6 Hydrocarbons on Platinum Alumina Catalysts Modified by Manganese
o. v. andreeva, yu. m. volodin and r. i. izmailov, Ibid., (3), 355–358
Pt/Al2O3 catalyst containing 0.014 wt.% Mn possesses reduced activity for hydrocracking hydrocarbons but the introduction of Mn in atomic ratios to Pt of 1:15, 1:10, 1:5 increases the activity of Pt/Al2O3 for isomerisation of n -C6H14.
Deactivation of Platinum/Alumina Reforming Catalysts by Carbon Deposits
n. m. shaimardanov, m. a. tatamarov and m. e. levinter, Ibid., 371–375
C is deposited mainly on the active Pt centres during dehydrocyclisation of n -C7H16. Deactivation of Pt/Al2O3 by C during dehydrogenation of cyclohexane occurs by a reduction in the number of active centres and not by a decrease in their activity. This is clear from the constancy of the activation energy for cyclohexane dehydrogenation at various stages of C deposition on the catalyst. Differences between deactivations of cyclohexane and HCOOH dehydrogenation are apparently due to heterogeneity of the active Pt centres.
Studies of the Regularity of Crystallisation of Platinum on Supports. IV. Effect of Conditions of Preparation on the Dispersion of Platinum
n. m. zaidman, n. p. krasilenko, l. m. kefeli and i. d. ratner, Kinet. Kataliz, 1970, 11, (3), 741–746
Studies of factors affecting the dispersion of Pt in Pt/Al2O3 showed that there is reduced dispersion when the support is roasted at a lower temperature than normal or when various chemical reagents are used to treat the support.
Dehydrocyclodimerisation. I. Dehydrocyclo-dimerisation of Butanes over Supported Platinum Catalysts
s. m. csicsery, J. Catalysis, 1970, 17, (2), 207–215
Dehydrocyclodimerisation, which converts C3, C4 and C5 paraffins to aromatics, is carried out at 430°C with dual-function catalysts possessing dehydrogenation and acid-type activity. Tests with 0.8% Pt/Al2O3 showed that the principal aromatics formed from C4H10 are xylene and toluene with smaller amounts of C6H6 and C9 and C10 aromatics. Using strongly acidic catalyst, product distribution from iso- and n -butanes is identical. Ethylbenzene and styrene are the main C8 aromatics formed from n -C4H10 over weakly acidic catalyst.
II. Dehydrocyclodimerisation of Propane and Pentane over Supported Platinum Catalysts
Dehydrocyclodimerisation of C3H8 over 0.8% Pt/Al2O3 gave mainly C6H6 whereas the process gave higher molecular weight products, e.g., naphthalene and other condensed aromatics, from C5H12. Ultimate recycle yield and conversion to aromatics increase with increasing C number of the initial light paraffin.
IV. The Reactions of Butenes
Ibid., (3), 323–330
To clarify the role of olefins as possible key intermediates in this process, C4H8 was reacted over Pt/Al2O3 and the product contained a large fraction of C5-C8 olefins and naphthenes. These and some aromatics also form over acidic catalysts with no dehydrogenation component. Results indicate that dehydrocyclodimerisation proceeds via conversion of light paraffins to olefins, dimerisation of these olefins and aromatisation of the dimers.
Effect of Heat Treatment on the Catalytic and Physical Properties of Pt/Al2O3 Adsorption Catalysts
s. a. khassan, g. i. emel’yanova, v. p. lebedev and n. i. kobozev, Zh. Fiz. Khim., 1970, 44, (6), 1469–1474
Studies of the sintering of Pt/Al2O3 at various stages of charging with Pt showed that in vacuum a steady amount of activity and surface is reached at each stage. Isochronous sintering has a minimum at 300−400°C. A decrease in activity during roasting is accompanied by a decrease in surface area and a decrease in size is accompanied by a drop in the number of Pt crystals. The number of active centres on the catalysts was determined.
Dehydrogenation of Dicyclohexyl over a Platinum-Alumina Catalyst without Added Hydrogen
a. w. ritchie and a. c. nixon, Ind. Engng. Chem., Product Res. Dev., 1970, 9, (2), 213–219
The effects of pressure, temperature and space velocity on the rates of reaction over Pt/Al2O3 were determined in the range 10–30 atm, 700−1300°F. High selectivity for the production of diphenyl was favoured by high temperature, high conversion and low pressure.
The Form of Active Centres of Adsorption Platinum Catalysts in Vapour-phase Processes
n. i. kobozev, zh. v. strel’nikova and l. e. martyshkina, Zh. Fiz. Khim., 1970, 44, (4), 1059–1064
Active centres of Pt/SiO2 catalysts for vapourphase hydrogenation of cyclohexene and dehydrogenation of cyclohexane are pairs of Pt atoms [Pt]2, as established during the reduction of CH3.CO.CH3, which showed that reduction of the C = O bond requires the proximity of two Pt atoms each with two free valencies.
On the Orientation of Cyclic Hydrocarbons with Medium-sized Rings in the Adsorption of Complexes on Platinum Catalysts
a. a. vedenyapin, e. s. balenkova and s. i. khromov, Kinet. Kataliz, 1970, 11, (3), 676–682 Differential heats of adsorption on C8−C12 cycloparaffins and n -paraffins over 5% Pt/asbestos were determined by chromatography. Cyclane molecules were oriented to the surface by CH2 groups containing transannular H atoms when in H2 atmosphere but in N2 atmosphere they were oriented by the maximum number of CH2 groups. The difference in entropy of adsorption of cycloparaffins in the two atmospheres was calculated. The high reactivity of medium-sized cycloparaffins in transannular dehydrocyclisation is due to the specific orientation of their molecules on the catalyst surface by reacting C atoms.
Kinetics and Mechanism of Oxidation of Carbon Monoxide on Platinum, Purified in High Vacuum
i. i. tret’yakov, a. v. sklyarov and b. r. shub, Ibid., (1), 166–175
A scheme is proposed for the oxidation of CO on Pt, purified in high vacuum at 10−6−10−2 torr, 175−1000°C. The reaction proceeds by a shock mechanism between adsorbed O2 and CO from the gaseous phase.
Determination of Surface Area by Chemisorption: Unsupported Platinum
m. a. vannice, j. e. benson and m. boudart, J. Catalysis, 1970, 16, (3), 348–356
Adsorption of H2 and O2, as well as reaction of H2, was studied gravimetrically and volumetrically on Pt black. H2O formed leaves the surface but is not replaced by additional H2. Amount of H2 adsorbed is the same on a reduced and evacuated surface as on a preoxidised surface. Ratio of adsorbed H and O atoms to surface Pt atoms is close to unity at room temperature and 50 torr.
The Problem of Standardising Pt-Catalysts
a. m. sokol’skaya, a. p. gorokhov and s. a. ryabinina, Vest. Akad. Nauk Kaz. S.S.R., 1970, 26, (2), 66–67
Exact control of alkali metal cation content is required to produce at PtO2 catalyst most suitable for a given reaction. The electrochemical potential of Pt black varies inversely with cation content and indicates the degree of purity of PtO2. Hydrogenation rate of compounds with various types of chemical bonds depends on the potential of the Pt black.
On the Effect of the Structure of Medium Size Cyclanes on their Catalytic Reactions in the Presence of Platinum
a. a. vedenyapin, e. s. balenkova and s. i. khromov, Vest. Moskov. Univ., Ser. II, Khim., 1970, 24, (2), 245–257
Studies of the reactions of C8 and C12 cycloparaffins on Pt/C showed the kinetics of decomposition of cyclooctane, cyclononane and cyclodecane, whose reactivities depended on their structures.
Hydrogen Chemisorption and Surface Composition of Silica-supported Platinum-Copper Alloys
j. h. anderson, p. j. conn and s. j. brandenberger, J. Catalysis, 1970, 16, (3), 326–331
9, 14, 19, and 25% Cu-Pt alloys were formed into 5 and 0.55 wt.% metal/SiO2 catalysts. Surface composition of alloy crystallites depended upon crystallite size; the larger the crystallite, the more the surface was enriched with Cu. Surface composition of 30Å crystallites approached that of their interior.
The Hydrogenation of Ethylacetylene. III. Reaction of Ethylacetylene with Hydrogen Catalysed by Platinum and Iridium
r. s. mann and k. c. khulbe, Ibid., (1), 46–53
When ethylacetylene and H2 reacted over pumicesupported and unsupported Pt and Ir at 20−80°C in various reactant ratios, the orders of reaction with respect to ethylacetylene and H2 were zero and one, respectively. Overall apparent activation energies were determined. Changes in selectivity and activity in relation to physical properties are discussed.
Vinyl Acetate. Vapour-phase Process
Br. Chem. Engng., 1970, 15, (5), process scan
The Hoechst-Bayer vapour-phase process for the catalytic conversion of C2H4, CH3COOH and O2 to vinyl acetate uses noble metal fixed bed catalysts, e.g., 0.1−2.0 wt.% Pd on Al2O3 and/or SiO2. An alkali acetate moderator improves the yield but requires constant replenishment. 91–94% selectivity is achieved and activity remains high for several months. Fluidised bed technique is also possible.
The Mechanism of the Palladium-catalysed Synthesis of Vinyl Acetate from Ethylene in a Heterogeneous Gas Reaction
s. nakamura and t. yasui, J. Catalysis, 1970, 17, (3), 366–374
Studies of Pd in the synthesis of vinyl acetate from C2H4 suggest that C2H4 and CH3COOH are activated by abstraction of H by Pd, (even when O is absent for C2H4 whereas it only occurs for CH3COOH when O is present). Vinyl acetate is produced by combining dissociatively adsorbed CH3COOH and C2H4, which is the rate-determining step in industrial reactions. Co-catalysts, e.g., K or other alkali metals, promote abstraction of H from CH3COOH and weaken Pd-O bonds in dissociatively adsorbed CH3COOH.
Study of Catalytic Hydrogenation in Liquid Phase
l. ČervenÝ, v. zapletal and v. ružička, Chem. Prumysl, 1970, 20, (4), 160–164
The selectivity of hydrogenation on a Pd/C catalyst does not depend on temperature, and is not influenced by catalyst poison, but increases with H2 partial pressure. Hydrogenation and isomerisation probably proceed on identical catalytic centres, their extent being governed by the strength of the olefin-active centre bond.
Fundamental Studies on Supported Palladium Catalysts
m. uhara, t. yamabe and s. suzuki, Kogyo Kagaku Zasshi, 1970, 73, (2), 252–256
The amount of H2 adsorbed on a Pd/C catalyst is much larger than on Pd wire or Pd black under the same conditions. The specific surface area has a great effect on the absorption isotherm. The relation between the specific surface area of Pd and the amount of H2 absorbed was studied using Pd/SiO2−Al2O3.
Asymmetric Hydrogenation Using Modified Cellulose-Palladium Catalysts
k. harada and t. yoshida, Naturwissenschaften, 1970, 57, (3), 131
Benzoylformic acid and α-acetamidoacrylic acid were hydrogenated using a series of Pd/cellulose catalysts to mandelic acid and alanine respectively. The products were of high optical purity, which was not obtained when unmodified catalysts were used. The celluloses used were carboxymethyl cellulose, aminoethyl cellulose and diethylamino-ethyl cellulose.
Asymmetric Hydrogenation Using Modified Ion Exchange Resin-Palladium Catalysts
Ibid., (6), 306–307
The same hydrogenations as above were carried out using a Pd-resin complex. The carboxylic acid resin was modified with optically active L-alanine or L-phenylalanine to give optically active products.
The Change of Adsorption and Catalytic Properties of Rh Black in the Presence of Cations
l. a. beketaeva, g. d. zakumbaeva and d. v. sokol’skii, Kinet. Kataliz, 1970, 11, (3), 704–709
Tests in H2SO4 electrolytes with additions of Cd, Tl, and Zn sulphates and of Pb acetate showed that the amount of H2 absorbed on Rh black decreases as the cation concentration rises. Thus hydrogenation of dimethylacetylenylcarbinol and of butyn-1-ol-3 on modified Rh black is slower than on Rh black without cations.
Catalytic Properties of Iridium Deposited on Alumina. III. Application of Thermodesorption to the Study of Adsorbed Ammonia
j. p. contour, j. pagniet and g. pannetier, Bull. Soc. Chim. Fr., 1970, (1), 75–79
NH3 adsorbed on γ-Al2O3, Ir/Al2O3 and Ir/SiO2 was studied by thermodesorption. The desorption activation energy was studied as a function of surface coverage from which the desorption sites energy distribution was calculated. For Ir/Al2O3 catalyst the desorption activation energy is 10.7 kcal/mole and is independent of the surface coverage.
Catalytic Reactions in an Ultrasonic Field
a. n. mal’tsev and i. v. solov’eva, Zh. Fiz. Khim., 1970, 44, (4), 1092–1094
An ultrasonic field acting on an aqueous N2−H2 solution in the presence of Pt-, Rh- and Pd-blacks increased the NH3 yield from 2 up to 6.5 times with the greatest yield using Rh. An ultrasonic field during H2O2 decomposition on Pt, Rh and Pd showed increased activity up to 10 times on Pt black, up to 2.5 times on Rh black but lower activity on Pd black. Change of activity was related to quantity of catalyst, e.g., reduction from 5 to 1 mg increased the activity of Pd by up to 4.5 times.
On the Relation of the Stereochemistry of Hydrogenation of Cyclo-olefins to the Nature of the Catalysts – Refractory Group VIII Metals
o. v. bragin, l. v. pozdnova and a. l. liberman, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1970, (6), 1319–1325
The activity of Group VIII metal catalysts for liquid-phase hydrogenation of methylcyclopentane decreases in the order: Pt>Rh>Pd>Ir≫Os>Ru>Co. Studies of the stereochemistry of hydrogenation of dialkylcyclopentanes over Pt/C, Pd/C, Rh/C, and Ir/C showed that the mixture of steroisomeric 1,2-dialkylcyclopentanes produced was richer in the trans isomer over Pt/C and Pd/C, and richer in the cis isomer over Rh/C and especially over Ir/C. A new mechanism for the hydrogenation of substituted cyclo-olefins is discussed.
Liquid-phase Hydrogenation of cis- and trans -Cyclodecenes over Group VIII Metals
v. i. alekseeva, e. s. balenkova, l. e. marinina and s. i. khromov, Neftekhimiya, 1970, 10, (3), 315–320
The constants were determined of the ratios of hydrogenation of cis -cyclodecene over Pt, Ir and Rh blacks, of trans -cyclodecene over Pt and Ir blacks, and of the rates of isomerisation of trans- to cis -cyclodecene over Pt, Ir and Pd blacks. The hydrogenation rate constants of cyclo-olefins are related to ring size, which is connected with the pressure of the cycloparaffins formed; the higher this pressure, the less is the rate constant of hydrogenation of the initial cyclo-olefin. Both cis- and trans -forms of cyclodecene are reduced at the same rate during this reaction.
Intramolecular Aromatic Substitution in Transition Metal Complexes
g. w. parshall, Accounts Chem. Res., 1970, 3, (4), 139–144
An aryl C-H bond in a donor ligand of a transition metal complex reacts with the central metal atom to form a metal-C bond. The H originally attached to C adds to the metal to form a metal-H bond or is eliminated as H+. This reaction is generally intramolecular and involves an ortho H bond of an aromatic N- or P-donor ligand. Reactions involving these ligands and complexes of Pt, Pd, Ir, Rh, and Ru are reviewed and the catalytic activity of triarylphosphine complexes is related to the studied mechanism.
Reactions of Acetylenes with Noble-metal Halides. VIII. The Palladium Chloride Catalysed Trimerisation of 2-Butyne and 1-Phenyl-l-propyne
h. dietl, h. reinheimer, j. moffat and p. m. maitlis, J. Am. Chem. Soc., 1970, 92, (8), 2276–2285
A series of these reactions was carried out. The mechanism was examined.
IX. The Decomposition of the Complex [Cl(Me2C2)3PdCl]2, Particularly to Vinylpentamethylcyclopentadiene
h. reinheimer, j. moffat and p. m. maitlis, Ibid., 2285–2294
The mechanism of this reaction is discussed.
Organic Syntheses by Means of Noble Metal Compounds. XLI. Reaction of Isocyanide with π-Allyl-palladium Chloride
t. kajimoto, h. takahashi and j. tsuji, J. Organometal. Chem., 1970, 23, (1), 275–280
The treatment of cyclohexyl isocyanide with π-allyl Pd chloride in C6H6 at room temperature gave di-μ-chloro-bis[1-(cyclohexylimino)-3-butenyl]-bis(cyclohexyl isocyanide)dipalladium by the insertion reaction, whose progress was followed by NMR spectroscopy.
Kinetics and Mechanism of the Oxidation of Olefins by Palladium Salts
i. i. moiseev, Kinet. Kataliz, 1970, 11, (2), 342–356
Experimental data are reviewed for the equilibrium formation of olefin π-complexes of Pd and for the kinetics of reduction of Pd salts by olefins in hydroxyl-containing solvents. The reduction includes the intermediate formation of π-complexes, their conversion into σ-bonded organopalladium compounds, and their heterocyclic decomposition. The mechanism of π-σ isomerisation and of the decomposition of organopalladium compounds is discussed.
Ligand Factors in the Isomerisation of Olefins by Palladium Complexes
w. h. clement and t. speidel, Ind. Engng. Chem., Product Res. Dev., 1970, 9, (2), 220–223
Studies of the equilibrium isomerisation of 1-hexene in methyl chloride catalysed by a series of 1,3-dichloro-2-hex-1-ene-4-(p Zpyridine-N-oxide)Pd(II) complexes showed that it is sensitive to the electronic nature of the trans N-oxide ligand, isomerisation only occurring when this ligand dissociates from the Pd-olefin complex. When the complex contains a strongly electron-withdrawing ligand the equilibrium favours free ligand and the catalyst system is then very effective.
Polymerisation of Butadiene by Rhodium Trichloride in Aqueous Medium
f. mikeš and j. kálal, Chem. Prumysl, 1970, 20, (5), 218–221
K formate and saturated aldehydes increase the rate of butadiene polymerisation by RhCl3, probably due to the reducing action of these compounds, which support the Rh having a lower degree of oxidation. Even low concentrations of K acetate lower the polymerisation rate.
Hydride Transfer Reactions Catalysed by Rhodium-Tin Complexes
h. b. charman, J. Chem. Soc., B, Phys. Org., 1970, (4), 584–587
Rh-Sn chloride complexes catalyse dehydrogenation of isopropyl alcohol to acetone, and H-D exchange between the α-CH and OH group of the alcohol. Reaction mechanisms are suggested.
Rhodium Catalysts for the Homogeneous Hydrogenation of Ketones
r. r. schrock and j. a. osborn, J. Chem. Soc., D, Chem. Commun., 1970, (9), 567–568
[RhH2X2L2]+ complexes, where L=solvent and X=PPh2Me, PPhMe2 or PMe3, catalyse the reduction of ketones under mild conditions, when promoted by small amounts of H2O.
Desulphonation of Aromatic Sulphonyl Halides Catalysed by Some Platinum-metal Complexes
j. blum and g. scharf, J. Org. Chem., 1970, 35, (6), 1895–1899
Desulphonylation of arenesulphonyl chlorides and bromides using RhCl(PPh3)3, RhCl(CO) (PPh3)2, IrCl(CO)(PPh3)2, RuCl2(PPh3)4, and PdCl2 catalysts is assumed to proceed mainly by a metal ion-promoted mechanism and partly by homolytic decomposition. A theory of the former accounting observations includes the steps ArSO2IrCl2(CO)(PPh3)2 → ArSO2IrCl2(CO) (PPh3) → ArIrCl2(CO)(SO2)(PPh3) and loss of SO2 from the last compound. Some new Rh and Ir complexes are described.
Homogeneous Olefin Hydrogenation over Oxidised Rhodium Complexes
r. l. augustine and j. f. van peppen, Ibid., 571–572
Hydrogenation of oxides obtained by oxidation of [Rh(Ph3P)Cl] in C2H5OH and C6H6 gives materials capable of olefin hydrogenation but double-bond isomerisation occurs in the reaction. Hydrogenation of these species in the presence of Ph3P gives catalysts much more active for olefin hydrogenation and which also inhibit isomerisation.
Homogeneous Catalytic Hydrogenation of α,β-Unsaturated Nitro Compounds Using Triarylphosphine-rhodium Complexes
r. e. harmon, j. l. parsons and s. k. gupta, Org. Prep. Proced., 1970, 2, (1), 25–27
RhCl(Ph3P)3 and trichlorotris [(4-biphenylyl) (1-naphthyl)phenylphosphine]rhodium(III) were used as homogeneous catalysts for the hydrogenation of α,β-unsaturated nitro compounds.
Synthesis of Trichlorotris(4-biphenyl-1-napthylphenylphosphine)rhodium(III). New Octahedral Complex
r. e. harmon, j. l. parsons and s. k. gupta, Org. Prep. Proced., 1970, 2, (1), 19–23
The complete synthesis of this complex is described. This complex is another potential homogeneous catalyst.
Use of Transition Metal Complexes as Selective Hydrogenation Catalysts
j. e. lyon, l. e. rennick and j. l. burmeister, Ind. Engng. Chem., Product Res. Dev., 1970, 9, (1), 2–20
Several specific examples of selective catalysis by noble metal complexes are given. Catalysts discussed include: IrX(CO)(Ph3P)2, where X = H or halogen; IrH3(Ph3P)3; (Ph3P)2MCl2, where M = Pt or Pd; and especially complexes of Rh with Ph3P, CO, H, and halogens.
Anodic Behaviour of Pb-Pt Bielectrodes in Low Salinity Electrolytes
h. helber and e. l. littauer, Corrosion Sci., 1970, 10, (6), 411–419
The Pb-Pt bielectrode was studied in various salinities. A thin film of PbO+PbS formed on the surface aids PbO2 formation and growth. In solutions ≥0.1 M NaCl the Pt microelectrode influences the sequence of events leading to the initial passivation prior to PbO2 formation and subsequently is vital to the nucleation and growth of PbO2.
ELECTRICAL AND ELECTRONIC ENGINEERING
Beam Lead Technology
m. e. hutton, Microelectronics, 1970, (April), 32–35
Beam leads of Au for Si monolithic circuits are produced in four stages: passivation, metal deposition, circuit delineation, and chip separation. During the second stage a thin layer of Pt is sputter-deposited over the whole slice and sintered into the contact window areas to produce Pt silicide. Excess Pt is etched away without masking. Layers of Ti and Pt are then deposited in sequence over the whole slice. Ti keys the metallising to the passivation surface. Pt acts as a diffusion barrier to subsequent Au deposition.