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Platinum Metals Rev., 1970, 14, (1), 29

ABSTRACTS: January 1970

of current literature on the platinum metals and their alloys

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PROPERTIES

Vapour Pressures of Liquid Titanium (2008 to 2379K) and Liquid Platinum (2045 to 2442K)

r. k. koch, e. d. calvert, c. r. thomas and r. a. beall, U.S. Bur. Mines Rept Invest. 7271, 1969 (July), 14 pp.

Two series of vapour pressure determinations were made on liquid Pt in a 2 kW electron beam furnace using a water-cooled Cu crucible and a disappearing filament pyrometer. Results were log p(atm)=8.240–30,460/T for 2086–2420K and log p(atm)=7.795–29,580/T for 2045–2442K respectively and mean standard heats of sublimation were 133.3 and 133.8 kcal/mole respectively.

Short-time Creep and Breaking Strength of Platinum-Rhodium Alloys

e. i. rytvin and v. v. malashkin, Metalloved. term. Obrabot. Metal., 1969, (6), 57–59

Studies of creep rate and breaking point of 15, 20, 30, and 40% Rh-Pt were extended above 1550°C by tests at 1500, 1600 and 1700°C under strain 1 kg/mm2. It appears that 15−20% Rh-Pt can be used to 1500, 20−30% Rh-Pt to 1600, and 30−40% Rh-Pt to 1700°C. The contributions of deformation between and inside the metal grains vary with Rh content and temperature so that 15−20% Rh-Pt fractures at 1600°C with necking, but 30−40% Rh-Pt fractures at 1500° without necking.

Intergranular Deformation during Creep of Platinum-Rhodium Alloys

i. i. novikov, f. s. novik, e. i. rytvin, s. s. prapor and l. p. shipulina, Izv. Vyssikh Ucheb. Zaved., tsvet. Metall., 1969, (3), 140–143

7, 10 and 15% Rh-Pt were studied at 1350, 1400 and 1500°C under stresses of 0.2, 0.5 and 1.3 kg/mm2. The contributions of intergranular and intragranular deformations to the elongation of the alloys were evaluated and point to a mechanism for creep of these alloys.

Constitution of Some Mixtures of Platinum with β-Elements (β = Sn, Sb, Te)

s. bhan, t. gödecke and k. schubert, J. less-common Metals, 1969, 19, (2), 121–140

An investigation by thermal analysis and X-ray diffraction of the phase diagrams of the Pt-Sb, Pt-Sn-Sb and Pt-Te systems revealed several new phases. Specific mention is made of the structures of Pt3Sb2, PtSn1·3Sb0·7, PtSnSb, PtSn1·2Sb1·8, PtTe, Pt3Te4, and Pt2Te3, which are discussed in terms of spatial correlationof electrons.

Dissociation Energy of Pd2

s.-s. lin, b. strauss and a. kant, J. chem. Phys., 1969, 51, (5), 2282–2283

The dissociation energy of Pd2 was determined using mass spectrometric and Knudsen effusion techniques and is given as 16.9 kcal, calculated using the Third Law method.

Hydrogen Permeation through Alpha-Palladium

s. a. koffler, j. b. hudson and g. s. ansell, Trans. Metall. Soc. AIME, 1969, 245, (8), 1735–1740

Permeability J of H2 through α-Pd, measured by a low pressure permeation technique in conditions where bulk diffusion was the rate-controlling process, is derived from for 2.9×10−5 to 5.0×10−3 cm Hg and T=300−709K. These data in conjunction with previous solubility data give the diffusivity of H2 through Pd as D=4.94×10−3exp(−5745/RT) cm2/sec. Substructure defects had no effect at these temperatures. The ratio of grain boundary diffusivity to bulk diffusivity was <105.

On the Role of Silver Atoms in the Absorption of Hydrogen by Palladium-Silver Alloys

r. burch, Solid state Commun., 1969, 7, (18), 1313–1317

Examination of the relationship between solubility of H2 and Ag content for Pd-Ag alloys over a range of temperatures and pressures showed that the reduction in bonding potential of Pd for H2 is a constant fraction of the Ag:Pd at. ratio.

Investigation of Alloys of the PdAl-Ag System

l. a. panteleimonov, d. n. gubieva and l. i. parshakova, Vest. moskov. Univ., Ser II, Khim., 1969, 24, (4), 85–87

Thermoanalytical, microstructural and microhardness studies of the PdAl-Ag system indicated the limited solubilities of the components in both liquid and solid states.

Localised Magnetic Moments on Iron Atoms in Solid Solutions of the Palladium-Copper System

l. a. ugodnikova and yu. n. tsiovkin, Fiz. Metal. Metalloved., 1969, 28, (2), 223–228

Studies of the relation between temperature and magnetic susceptibility of 1% solutions of Fe in Pd-Cu showed that the minimum magnetic moment of Fe is 3.8±0.2 μB in 40% Cu-Pd.

Iron-Palladium Fine Particles Prepared by Evaporation Method

a. iga, y. tawara, t. sakakibara and a. tasaki, Japan J. appl. Phys., 1969, 8, (8), 1057

Fe-Pd alloys were evaporated in an atmosphere of pure Ar at 15 Torr and formed into fine particles whose sizes ranged from 300 to 700Å and which were found to be in the f.c.c. disordered phase. The alternative ordered f.c.t. phase could then be obtained by heating the evaporated particles at a temperature below the critical temperature of composition. The lattice parameter for disordered Fe-Pd was 3.820 Å; for the ordered alloy parameters were a=3.86−3.88, c=3.68−3.71 Å, c/a=0.950−0.960, depending on the annealing temperature.

The Effect of Magnetic and Configurational Disordering on the High Temperature Heat Capacity of a Ni-50 at.% Pd Alloy

r. e. bingham and c. r. brooks, J. Phys. Chem. Solids, 1969, 30, (10), 2365–2370

Heat capacity – temperature curves at 400–920K for 50 at.% Pd-Ni solid solution, measured after various heat treatments, show quite measurable deviations from a smooth curve. A rise in the heat capacity beginning below 400K and finishing ∼520K is associated with ferromagnetic disordering. Anomalous behaviour above 520K is due to non-random atom arrangements in the alloy, induced by heat treatment.

Formation, Stability and Structure of Palladium-Silicon Based Alloy Glasses

h. s. chen and d. turnbull, Acta. Metall., 1969, 17, (8), 1021–1031

A report on Pd-Si based alloy glasses formed by quenching a number of different melts to room temperature at various cooling rates, typically in the order of 106 deg C/sec. Both binary and ternary alloys are discussed, and experimental details are given, including results of X-ray and electron microscope investigations, thermal properties and electrical resistivity.

A Study of Some α Palladium-Scandium, -Zirconium and -Gadolinium Alloys

m. norman and i. r. harris, J. less-common Metals, 1969, 18, (4), 333–345

A report on the room-temperature lattice spacings of some αPd-Sc, αPd-Zr and αPd-Gd alloys, and the room-temperature magnetic susceptibilities of some αPd-Sc and αPd-Zr alloys. Comparison is made with αPd-Y, αPd-Ce, αPd-In and αPd-Sn.

Thermodynamics of the First Order Transition in FeRh

j. m. lommel, J. appl. Phys., 1969, 40, (9), 3880–3881

Bulk samples of the compound FeRh undergo a sharp transition which is thermodynamically of the first order between the antiferromagnetic and ferromagnetic states. The critical temperature at which this transition occurs is field-dependent, and the critical field for inducing the transition is related to the square of the temperature. Results are given for 77–370K and for fields up to 250 kOe.

New A3B5 Phases of the Titanium Group Metals with Rhodium

b. c. giessen, r. wang and n. j. grant, Trans. Metall. Soc. AIME, 1969, 245, (6), 1207–1210

A report on the existence and isomorphism of Ti3Rh5 and Hf3Rh5, both shown to be of the orthorhombic Ge3Rh5 type; an analogous phase with Zr does not exist. Lattice parameters and refined positional parameters are given, together with details of experimental work based on X-ray and other crystallographic methods.

The Hafnium-Iridium System

m. i. copeland and d. goodrich, J. less-common Metals, 1969, 18, (4), 347–355

A report from the U.S. Bureau of Mines on Hf-Ir phase relations by metallography, thermal analysis, electron beam microprobe and X-ray diffraction techniques. Four intermediate phases (Hf2Ir, Hf5Ir3, HfIr, and HfIr3) were identified, together with a number of eutectic and eutectoid alloys of Hf and Ir.

CHEMICAL COMPOUNDS

Some Acid Properties of H2PtCl6

r. w. maatman and c. j. addink, J. Catalysis, 1969, 15, (2), 210–213

A method of determining the acid content of H2PtCl6 involves its titration with NaOH using an excess of Cl to repress exchange. H2PtCl6 was shown to be a very strong acid by plots of pH titrations, by comparison of pH values using the same electrodes for solutions of H2PtCl6 and of H2SO4 of the same concentration, and by its reaction with NDA (4-nitrodiphenylamine), a very weak base.

Two New Ternary Copper-Platinum Oxides

o. muller and r. roy, J. less-common Metals, 1969, 19, (3), 209–214

Two new phases synthesised at 890°C, atm are the solid solution Cu1−xPtxO, which has tetragonal PtS structure and x=0.135−0.355, and CuPt3O6, which has a primitive orthorhombic cell with a=11.588, b=6.126, c=3.109Å. These phases are black and very insoluble.

Cationic Transition Metal-Olefin Complexes

b. f. g. johnson, j. lewis and d. a. white, J. Am. Chem. Soc., 1969, 91, (18), 5186–5187

A number of cationic olefin complexes with Pd, Pt and Rh were derived by treating enyl complexes of the metals with electrophilic agents such as Ph3CBF4 or HBF4. Four reaction schemes are described. These provide a general route for preparation of a wide variety of cationic derivatives.

Chloride Complexes of Rhodium(III) in Aqueous Solutions

v. i. shlenskaya, o. a. efremenko, s. v. oleinikova and i. p. alimarin, Izv. Akad. Nauk SSSR, Ser. Khim., 1969, (8), 1643–1646

Ru chloride complex formation in aqueous solutions proceeds in stages and is reversible. Total and partial (stage) stability constants were calculated from spectrophotometric data derived from Ru perchlorate solutions.

The Reaction of Iridium and Rhodium with Refractory Carbides and Borides

r. a. mercuri and j. m. criscione, Abstr. Papers, 158th Mtg, Am. Chem. Soc., 1969, (Sept.), INOR 33

Ir and Rh when heated to ∼1200°C and mixed intimately with Hf and Zr carbides yield C and noble metal-rich compounds; e.g. HfC and Ir yield HfIr3 and C. Ir and Rh react at 1160−1230°C with Zr and Hf borides to yield cubic phases as 1:3 transition metal: noble metal, held in noble matrices.

Photochemical Oxidation of Nitrogenammine Ru(II) Compounds

c. sigwart and j. t. spence, J. Am. Chem. Soc., 1969, 91, (14), 3991–3992

A study of nitrogenammineruthenium(II) compounds as possible models for biological N2 reduction. Experiments included exposure of a solution of deoxygenated Ru(NH3)5N2+ to UV light and the subsequent appearance of a Ru(III) species; solutions of the dimer Ru(NH3)5N2Ru (NH3)54+ behaved similarly. Photochemical oxidation was found to proceed equally well in acidic, neutral or basic conditions. Work continues to identify the reduction product and to confirm the suspected reduction of the bound N2 after photolysis.

Formation of Metal Ion-Nitrene Complexes

l. a. p. kane-maguire, f. basolo and r. g. pearson, Ibid., (16), 4609–4610

A report on the formation of nitrene co-ordinated to Ru ion via the catalytic action of an acid, e.g., H2SO4, on Ru(II) azide complexes.

ELECTROCHEMISTRY

The Adsorption of Water on Platinum Electrodes in Aqueous Electrolytes

j. w. schultze, Ber. Bunsenges. Phys. Chem., 1969, 73, (5), 483–491

Potentiostatic tracer studies on H2O adsorption on smooth Pt electrodes in H2SO4 HTO solution showed that an approximate monomolecular H2O layer is formed in the double-layer region, and a similar layer is adsorbed on the oxide layer built up at higher potentials. In acid and neutral solutions the exchange PtOTH + H2O→PtOH2 + HTO is rate determining but in alkaline solutions the exchange occurs by PtOTH + OH → PtOH + HTO.

An Electrochemical and Electron Microscopic Study of Activation and Roughening of Platinum Electrodes

t. biegler, J. Electrochem. Soc., 1969, 116, (8), 1131–1137

A report on the factors governing the behaviour of Pt electrodes during anodic-cathodic cycling in 1 M H2SO4; in particular, details of the activation and roughening of Pt electrodes, thought to occur through weakening of Pt interactions due to the formation of strong Pt-O chemisorption bonds.

Cyclic Voltammetry of Mixed Metal Electrodes

j. s. mayell and w. a. barber, Ibid., (10), 1333–1338

Repetitive potentiostatic triangular voltage sweeps cause significant changes in surface structure and catalytic activity of mixed metal electrodes, e.g., with a Pt-Rh black electrode each successive cycle causes a decrease in the Pt oxidation and reduction peaks with a proportionate increase in Rh oxidation and reduction peaks. Complete elimination of Pt peaks is related to resistance of the electrode to CO poisoning. A mechanism for these phenomena involves migration and redistribution of Rh. Pd-Rh, Pt-Ru and Au-Rh electrodes exhibit similar characteristics.

Diffusion of Oxygen through a Platinum Diaphragm

j. p. hoare, Ibid., 1390–1392

A thin Pt foil, mounted in a cell between two compartments containing 2 N H2SO4, was anodised on the polarisation side and O2 was detected on the diffusion side by the increase in potential to an α-Pd reference electrode in the N2-stirred acid solution. When the foil became a cathode, the potential on the diffusion side became less noble. Diffusion coefficient at 24°C from cathodised foil data was 1.8 × 10−11 cm2 sec−1 and from anodised foil data was 4.4 × 10−11 cm2 sec−1.

Studies of Anodic and Cathodic Polarisation of Palladium in Cyanide Solutions

i. a. kakovskii, v. a. svetlov and b. d. khalezov, Izv. Vysshikh Ucheb. Zaved., tsvet. Metall., 1969, (3), 51–57

Galvanostatic studies on the anodic and cathodic polarisation of Pd in cyanide solutions saturated by O2 or air, using the rotating disc, show as much passivation of Pd as with less cyanide and lower temperature with more O2 and agitation. If the critical value of outer anode current is exceeded the potential drops sharply, i.e., passivation increases. O2 is reduced to hydroxyl during cathodic polarisation. These studies explain the dissolution of Pd in cyanide solutions.

Mechanism of Dissolution of Palladium in Chlorinated Hydrochloric Acid Solutions

a. d. kovylayev and m. d. ivanovskii, Ibid., 58–61

Rotating disc studies of Pd dissolution in chlorinated HCl solutions at 20−80°C, 300−1500 rev/min, 0−10 g.mole/l HCl suggest an electrochemical dissolution mechanism which is autocatalytic and has two stages. At first Cl2 causes cathodic depolarisation; in the second stage [PdCl6]2− is reduced at Pd electrodes with less overvoltage than for reduction of Cl2.

Electrochemical Preparation of Rhodium(O) Complexes

d. c. olson and w. keim, Inorg. Chem., 1969, 8, (9), 2028–2031

Two new Rh(O) complexes, Rh((C6H5)3P)4 and Rh((C6H5)2PCH3)4, were prepared by electro-reduction in 85% acetonitrile-15% toluene of ((C6H5)3P)3RhCl and ((C6H5)2PCH3)3RhCl, respectively.

ELECTRODEPOSITION AND SURFACE COATINGS

Epitaxial Deposition of Platinum on Iridium at Low Temperatures

w. r. graham, f. hutchinson, j. j. nadakavukaren, r. a. reed and s. w. schwenterly, J. appl. Phys., 1969, 40, (10), 3931–3936.

Pt evaporated on a clean Ir surface at temperatures as low as 200K produces epitaxial layers, as shown by field ion microscopy. If the Ir surface has been exposed to the atmosphere after forming, the temperature required for epitaxy rises to ∼375K. Even this temperature is well below that required for high mobility of the incoming atoms over the surface, as assumed in present theories of the formation of epitaxial layers.

Electrodeposition of a Silver-Palladium Alloy

l. domnikov, Metal Finish., 1969, 67, (9), 58–59, 65

Conditions are described for the electrodeposition of a Ag-Pd alloy from a CN bath. The structure sensitive properties of the deposits were studied and are compared with X-ray analysis results.

Direct Activation of Polymers for Electroless Deposition

l. t. romankiw, Extended Abstr., 136th natl Mtg. Electrochem. Soc., 1969, (Oct.), abstr. 135

A technique was developed which avoids intentional roughening of the polymer surface yet provides satisfactory adhesion of the plated film. A Pd salt as activator was dissolved in a solvent compatible with the monomer and the mixture was applied to the surface to be metallised. Reduction to Pd occurred either during or after polymerisation of the monomer. Pd on the surface initiates electroless deposition and is believed to be embedded in the polymer. NiPdCl6 dissolved in dimethylacetamide rendered polyimide capable of being metallised by Cu. 0.4−2.0% Pd in the polymer gave optimum results.

Palladium Chloride Activation of Plastic Surfaces prior to Metallisation

k. petrov, g. passabov, e. dobrev and m. entscheva, Kunststoffe, 1969, 59, (4), 229−232

Studies with 103Pd of the activation before metallisation of polystyrene and polyamide with HCl-PdCl2 solutions showed that surface activation is a sorption process, maximum sorption of Pd2+ occurring at 2 g/l Pd, pH2, 20°C, 20 min immersion. Satisfactory activation can occur in more dilute solutions over shorter times.

Electrodeposition of Rhodium from a Molten Sodium Cyanide Electrolyte

g. r. smith, c. b. kenahan, r. l. andrews and d. schlain, Plating, 1969, 56, (7), 805–808

A method of electrodepositing protective coatings of Rh up to 7.8 mils thick from a fused salt electrolyte made by dissolving Rh in molten NaCN. Plating is done in a special cell at 600°C under an atmosphere of Ar. The anode is either Rh or graphite. The cathode is one of several substrate materials suitable for plating, e.g., W and Mo, which so treated are protected from oxidation up to 600 and 700 deg C above their normal oxidation temperatures.

Ruthenium Plating

g. a. conn, Ibid., (9), 1038–1040

Tests on the plating of Au-plated Cu cathodes with Ru, using RuNOCl3.5H2O and sulphamic acid as plating solution showed the effects of Ru content, current density, sulphamic acid concentration, and temperature on the plating efficiency. A temporary increase of efficiency occurs by control of temperature, by anodic reactions and by control of complexing agent concentration to cause the metal complex to shift from a non-plateable to a plateable state. The physical properties of Ru plating are affected by the methods used to achieve increased plating efficiency. Periodic stopping of the plating current reduces stress in the deposit.

HETEROGENEOUS CATALYSIS

Comparison of the New Platinum Reforming Catalyst of Czechoslovak Production with Foreign Catalysts

o. svajgl and h. kostkova, Ropa Uhlie, 1969, 11, (3), 116–126

The stability and activity of the new Czech petroleum reforming catalyst, which is supported on a highly active Al2O3, is compared to the Houdry-Hüls catalyst. It is insensitive to low H2:hydrocarbon ratio. A drying method is specified as all feeds contained ∼10 p.p.m. H2O. Reformates have research octane numbers >95 in continuous operation, at lower pressures and with higher throughput than formerly.

Direct Evidence for Dual-functional Cyclisation of Paraffins over Platinum Reforming Catalysts

a. j. silvestri, p. a. naro and r. l. smith, J. Catalysis, 1969, 14, (4), 386–388

n -C7H16 containing 100 p.p.m. S reacts on either Pt/C or Al2O3 to yield relatively few ring hydrocarbons but the large increase in ring production when both catalysts are mixed points to paraffin cyclisation proceeding by a dual-functional mechanism.

On the Dependence of the Catalytic Activity of Platinum on the Crystalline Size and Orientation

v. s. bagotsky, yu. b. vassiliev, a. m. skundin, v. sh. palanker, i. i. pyshnograeva, o. a. khasova and l. s. kanevsky, Abstr. Papers, 158th Mtg, Am. Chem. Soc., 1969, (Sept.), FUEL 18

Pt catalyst activity was investigated for electrolytic H2 and O2 evolution, anion and CH3OH adsorption and CH3OH oxidation. For the latter the activity of platinised Pt was much lower than that of smooth Pt. Small quantities of Pt microcrystals were deposited on smooth C and it was found that the rate of H2 evolution depended on crystal size and distance between crystallites. For small crystallites and small amounts of crystallites the rate is >5–7 that on smooth Pt.

Kinetics of the Catalytic Conversion of Cyclodecane over Platinised Carbon

a. a. vedenyapin, e. s. balenkova and s. i. khromov, Kinet. Kataliz, 1969, 10, (4), 808–812

Kinetics of total conversion of cyclodecane over Pt/C are explained by the Frost equation. Methods for finding activation energies of the constituent processes are proposed. Activation energy of transannular C5- and C6-dehydrocyclisation exceeds that of the analogous reaction with paraffins, which suggests a mechanism for the transannular conversion of cyclodecane.

Catalytic Conversion of Spiro-(4,4)-nonane on Platinum Catalyst

n. v. elagina, s. z. frenkel’ and b. a. kazanskii, Dokl. Akad. Nauk SSSR, 1969, 188, (2), 358–361

Spiro-(4,4)-nonane undergoes ∼33% conversion over Pt black at 310°C in the absence of the gases but undergoes ∼75% conversion in a stream of H2. The compositions of the products are given and the reasons for them are suggested.

Investigation of Structures and Activity of Promoted Catalysts of the Metal-Metal Oxide Type. III. Hydrogenation of Isoprene on Pt and Pd Catalysts Promoted by Salts of Chromium, Manganese and Zinc

r. g. davlesupova, r. z. khairullina and r. i. izmailov, Kinet. Kataliz, 1969, 10, (4), 847–851

Comparison of Pt and Pd catalysts (on C, SiO2 and Al2O3) for the hydrogenation of isoprene showed that Cr and Mn additions to Al2O3 increased catalytic activity and raised the content of sorbed H2. Where the H2 is added to dienes it is independent of the nature of the support. Mn-promoted Pt/Al2O3 catalysed more direct H2 addition to isoprene to form 2-methylbut-2-ene.

Hydrogenation of Methylacetylene over Platinum and Iridium Catalysts

r. s. mann and k. c. khulbe, J. phys. Chem., 1969, 73, (7), 2104–2110

An investigation of the reaction between methylacetylene and H2 over pumice-supported and unsupported Pt and Ir catalysts in a static system for a wide range of reactant ratios and between 20 and 150°C. Selectivity was found to be dependent on initial H2 temperature and pressure and independent of methylacetylene pressure. Overall activation energies were 12.4, 14.7, 8.6 and 6.2 kcal/mole for Pt/pumice, Pt powder, Ir/pumice and Ir powder, respectively.

Investigation of Stationary Palladium Catalysts for Hydrogenation of Oils

d. v. sokol’skii, e. p. mazin and k. a. zhubanov, Zh. prikladnoi Khim., 1969, 42, (6), 1270–1274

Stationary Pd catalysts possess adequate activity, selectivity and stability for the hydrogenation of fats, e.g., optimum conditions for hydrogenation of sunflower oil over Pd/Al2O3 at atmospheric pressure are 220°C and space velocity of H2 18h−1.

Hydrogenation of Unsaturated Compounds on Palladium/Polymer Catalysts

o. a. tyurenkova, Zh. fiz.Khim., 1969, 43, (8), 2088–2092

Hydrogenations of allyl alcohol, o -nitrophenol and dimethylethynylcarbinol showed that catalysts used have the following order of activity: Pd/polyvinyl alcohol, Pd/polyacrylonitrile, Pd/anilide, Pd/polyethyleneterephthalate. The polymers enhanced the activity of Pd.

Mixed Adsorption Hydrogenation Catalysts. XV. Rhodium-Silver Catalysts on Silica Gel

a. a. alchudzhan, n. z. edigaryan and m. a. mantikyan, Arm. khim. Zh., 1969, 22, (1), 3–9

Studies of Rh-Ag/SiO2 catalysts with 1.0, 0.5 and 0.2 wt carrier % Rh and 20–90 at.% Ag-Rh for hydrogenation of C6H6 show that activity-Ag content graphs for 1.0 and 0.5% Rh catalysts have both a minimum and a maximum but that for 0.2% Rh there is a rapid decrease of activity with increased content of Ag and then a slower decrease. For 1% Rh catalysts prepared by consecutive adsorption and reduction of Rh and Ag salts, the activity decreases as Ag content increases. If Ag is adsorbed before Rh the catalysts are more active, i.e., Ag covers more active Rh in the former case.

Olefin Isomerisation Catalysed by Group 8 Metals in Absence of Molecular Hydrogen. Part 3. Butene Isomerisation over Iridium-Alumina

s. d. mellor and p. b. wells, Trans. Faraday Soc., 1969, 65, (7), 1873–1882

Butene isomerisation catalysed by Ir/Al2O3.H2O was studied at 100°C and the overall relative rate constants were determined. Isomerisation occurs by an addition-abstraction mechanism, the intermediates being chemisorbed secondary butyl groups. If surface H atom availability is low, butene desorption is rate-controlling, and the products are formed in equilibrium proportions; if high, desorption is not rate-controlling and the but-l-ene isomerises predominantly to cis -but-2-ene due to steric factors.

Hydrogenation of Olefins. Part 5. Hydrogenation of But-l-ene Catalysed by Iridium-Alumina

Ibid., 1883–1890

But-1-ene hydrogenation and isomerisation catalysed by Ir/Al2O3 was studied at 20−170°C and the kinetics were obtained. The formation of chemisorbed butyl groups was rate-determining in both processes. The rate of isomerisation declined from 150°C to a minimum at 20°C. Ir alone of Group VIII metals favours the formation of cis -but-2-ene.

On the Mechanism of Isomerisation of Allyl Alcohol on Platinum Group Metals

zh. i. bobanova, g. a. bogdanovskii and g. d. vovchenko, Vest. moskov. Univ., Ser. II, Khim., 1969, 24, (4), 88–91

Isomerisation of allyl alcohol on Pt, Rh and Pd blacks in 1 N H2SO4 showed C2H5CHO and traces of acrolein and C3H7OH in the liquid phase in the case of Rh black. Dehydrogenation and autohydrogenation controlled this isomerisation mechanism.

Catalytic Oxidation of Methane on Zeolites Containing Rhodium, Iridium, Palladium, and Platinum

j. g. firth and h. b. holland, Trans. Faraday Soc., 1969, 65, (7), 1891–1896

The complete oxidation of CH4 over zeolites containing Pd, Pt, Rh and Ir was studied using a microcalorimetric technique. The results show that isolated ions of these metals can absorb CH4 and O2 but only with Pt competitively.

Catalytic Decomposition of Hydrogen Peroxide by Metals and Alloys of the Platinum Group

d. w. mckee, J. Catalysis, 1969, 14, (4), 355–364

Kinetic studies at 27°C as a function of catalyst composition and pH of the solution for the decomposition of dilute aqueous solutions of H2O2 showed that in neutral solution the order of specific activity per unit surface area of the metals was Pt>Os>Ir>Pd>Ru>Rh and that Pt-Pd, Pt-Ru and Pt-Rh had activities intermediate between those of their constituents, while Pt-Ir and Pd-Au showed maximum activity at intermediate alloy compositions. The reaction rate reached a sharp maximum at pH 10–11.

Hydrogenation of Propylene over Group VIII Metals

r. s. mann and t. r. lien, Ibid., 15, (1), 1–7

Catalytic activities of Group VIII metals supported on pumice for the C3H6-H2 reaction are in the same sequence Rh>Ir>Ru>Pt>Pd>Ni>Fe>Co>Os. Orders of hydrogenation are first or slightly lower for H2 and zero or slighlty negative for C3H6. Activation energies have been determined.

HOMOGENEOUS CATALYSIS

Organic Syntheses by Means of Noble Metal Compounds. XXXIX. Palladium Catalysed Carbonylation of Propargyl Compounds

t. nogi and j. tsuji, Tetrahedron, 1969, 25, (17), 4099–4108

Pd-catalysed carbonylation of propargyl chloride and acetylenic alcohols were carried out using PdCl2 or Pd/C.

XL. Palladium-catalysed Carbonylation of Allylic Ethers

s. imamura and j. tsuji, Ibid., (18), 4187–4195

Carbonylation of allylic ethers, especially 1,4-diethoxy-2-butene was carried out using PdCl2, Pd(acac)2 or Pd/C.

A Novel Palladium(II) Chloride-promoted Addition-Rearrangement Reaction of Terminal Olefins with Diphenylacetylene

p. mushak and m. a. battiste, J. Chem. Soc., D, chem. Commun., 1969, (19), 1146–1147

C2H4 and certain terminal olefins react with diphenylacetylene in the presence of PdCl2 to produce substituted alka-1,3-dienes derived from symmetrical addition of two olefin units to the acetylenic reactant.

Aromatic Substitution of Olefins. VII. Reactions of Lower Olefins with Benzene Catalysed by Palladium Acetate

s. danno, i. moritani and y. fujiwara, Tetrahedron, 1969, 25, (19), 4809–4813

Phenylation of C3H6, 1-C4H8, trans- and cis- 2-C4H8 and 1,3-butadiene with C6H6 was carried out using Pd(OAc)2 and AcOH as catalysts.

VIII. Substituent Effects on the Reactions of Styrene with Monosubstituted Benzenes in the Presence of Palladium(II) Salts

y. fujiwara, i. moritani, r. asano, h. tanaka and s. teranish, Ibid., 4815–4818

Styrene was reacted with monosubstituted benzenes (toluene, ethyl benzene) with Pd(II) salts such as Pd(OAc)2 and PdCl2. Direction of substitution is influenced by the substituent.

IX. Reactions of Olefins Containing a Polar Group with Benzene

s. danno, i. moritani and y. fujiwara, Ibid. 4819–4823

Phenylation of olefins containing a polar group, such as acrylonitrile, was carried out using Pd(OAc)2 and AcOH as catalysts.

Trichlorotris(4-biphenyl-l-naphthylphenylphosphine)rhodium(III), a New Homogeneous Hydrogenation Catalyst

r. e. harmon, j. l. parsons, d. w. cooke, s. k. gupta and j. schoolenberg, Abstr. Papers, 158th Mtg, Am. Chem. Soc., 1969, (Sept.), INOR 202

This octahedral complex was synthesised from 4-biphenyl-1-naphthylphenylphosphine and RhCl3.H2O in stoichiometric amounts. It was used to reduce quantitatively internal and highly substituted double bonds in unsaturated carboxylic acids under mild conditions.

Homogeneous Benzylic Oxidation Catalysed by Some Complexes of the Platinum Group

j. blum, j. y. becker, h. rosenman and e. d. bergmann, J. Chem. Soc., B, phys. org., 1969, (8), 1000–1004

Studies of autoxidation of C6H5.C2H5 and related compounds in the presence of various organic compounds of Ir, Pd, Pt, Rh, and Ru showed that RhCl(PPh3)3 is the most effective catalyst but that use of RuCl2(PPh3)3 is limited to oxidation of non-halogenated alkylarenes and needs a co-catalyst addition of polyhalogenoalkane.

CHEMICAL TECHNOLOGY

Corrosion Resistance of Ti-0.2 Pd Semifinished Alloys Manufactured Industrially

n. d. tomashov, f. a. orlova, n. f. anoskin, ya. v. matlis, e. i. oginskaya and g. p. chernova, Zashchita Metal., 1969, 5, (5), 491–495

0.2% Pd-Ti is shown to be a corrosion-resistant material for chemical engineering.

Hydrogen Pick-up and Dissolution in Titanium and Titanium-Palladium Alloys

n. d. tomashov, v. n. modestova, r. p. vasileva and n. i. stroganova, Ibid., 496–502

Small additions of Pd reduce pick-up of H2 by Ti. Corrosion of Pd-Ti causes Pd to accumulate on the surface of the alloy which reduces the potential so that H pick-up decreases. H2 diffuses deep into Ti when anodic dissolution occurs at the unalloyed metal.

ELECTRICAL AND ELECTRONIC ENGINEERING

Platinum-doped Silicon Diodes with Negative Resistance

a. a. lebedev and n. a. sultanov, Fiz. Tekh. Poluprov., 1969, 3, (4), 622–623

Pt-doped Si diodes with normal V-A characteristics at room temperature, with a small voltage drop in the forward direction, had negative differential resistance at 77K. Vmax reaches 120V and Vmax/Vmin is 2−5.5. Vmax decreases as temperature rises and the negative resistance disappears at 150K. Diodes prepared from over-compensated Si where, after diffusion of Pt the p -Si is converted to n -Si, have some negative differential resistance at room temperature.

A Thick-film Resistor Glaze of Precision Properties

p. r. van loan, Proc. 1969 electron. compon. Conf., 1969, 285–288

TI and Ru oxides dispersed in a Pb borosilicate glass matrix form thick-film glaze resistors with good electrical properties, especially stability. Pastes can be fired at 625−675°C to produce films with sheet resistivity 100 ohm/sq−1 kohm/sq, TCR values of ±50 p.p.m., noise <−25 db/decade, stability ≫1% ΔR in a wide range of environments.

TEMPERATURE MEASUREMENT

Determination of Temperatures below 14K with Platinum Thermometers

r. muijlwijk, Physica, 1969, 43, (3), 419–423

By using the results of measurements of the resistances of eight Pt thermometers between 1.3 and 14K it is shown that temperature can be deduced from measurements with Pt thermometers between 2 and 14K with an accuracy of 0.02 deg K if the constants W0, A, B, and γ in the equation W = W0 + AT2 + BTγ are known from calibrations between 1.3 and 5K and between 10 and 14K. W is the resistance ratio R(T)/R(0°C).

On the Definition of an International Practical Temperature Scale. The Interpolation of Differences in the Resistance Ratios of Platinum Thermometers between 91K and 14K

r. muijlwijk, m. durieux and h. van dijk, Ibid., (4), 615–621

The IPTS is defined by using the relation between temperature and resistance ratio W(T)=R(T)/R(0°C) of Pt. In this study three methods for interpolation of ΔW have been applied to experimental data. Between the boiling and triple points of 02 the accuracy is within 1 mK; between the boiling points of 02 and of H2 and also between the boiling and triple points of H2 accuracies within 2 mK are possible.

Comparison of Platinum Resistance Thermometers with the Hydrogen Vapour-pressure Thermometer

Ibid., 622–632

Pt thermometers are compared with the 20.4K equilibrium H2 vapour pressure thermometer in three different apparatuses, using the CCT-64 scale for the Pt thermometers and the TL60 scale for the vapour pressure thermometer. “Best values” on the CCT-64 scale of the fixed points of the 1968 IPTS in the liquid H2 range are given.

The Behaviour of Pt/PtRh and Ni/NiMo Thermal Elements in the High Temperature Furnace in the Presence of Material Containing Chromium

e. lenz, Werkstoffe Korrosion, 1969, (8), 651–658

Evaporation of Cr from alloy parts of the furnace during vacuum annealing at 10−3 to 10−4 Torr, >1200°C leads to deposition of Cr on thermocouples, which suffer reduction of service life by formation of hard, brittle intermetallic compounds. Suggested cures include use of vacuumtight sheaths for the thermocouples, introduction of some N2 to the vacuum above 1000°C, and replacement of Cr alloy components by ceramic materials or Mo alloys.

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