ABSTRACTS: January 1985
ABSTRACTS: January 1985
of current literature on the platinum metals and their alloys
Oxidative Dissolution of Platinum and Ruthenium from Various Base-Metal Binary Alloys
r. l. paul and m. m. krÜger, S. Afr. J. Chem., 1984, 37, (3), 116–120
The preparation of several binary alloys composed of Pt or Ru with a base metal (Al or Fe) and leaching tests on them in HCl acid are described. The poor dissolution observed for Ru is attributed to the strong affinity of this metal for O, which results in partial passivation of the metal. The almost quantitative dissolution of the Pt alloys is ascribed to the lesser affinity of Pt for the adsorption of O, and to the presence of absorbed H.
The Effect of Various Additional Elements on Properties of Fe-Pt Permanent Magnets Having High Energy Product
k. watanabe and h. masumoto, J. Jpn. Inst. Met., 1984, 48, (9), 930–935
The effects of Rh, Pd, Ir, Ti, V, Au, Al, Ga and Ge on Fe-Pt alloys were evaluated. The permanent magnetic properties of Fe-Pt alloys can be improved by adding a small amount of Ti and V. The alloy 60at.%Fe-39at.%Pt-1at.%Ti has the highest maximum energy product of 165 kJ/m3, coercive force of 360A/m and residual flux density of 1.0T when aged at 823K after water quenching. Alloy 60.5at.%Fe-38.5at.%Pt-1at.%V showed the highest coercive force of 410kA/m, maximum energy product 160kJ/m3 and residual flux density of 1.04T when aged at 773K after water-quenching. The permanent magnetic properties cannot be improved by other additions.
A Photoemission Study of the Oxidation of Platinum in Pt-Based Alloys: Pt-Pd, Pt-Ru, Pt-Ir
l. hilaire, g. diaz guerrero, p. lÉgarÉ, g. maire and g. krill, Surf. Sci., 1984, 146, (2/3), 569–582
A photoemission technique was used to study the surface composition of Pt-Pd, Pt-Ru and Pt-Ir alloys. The samples were exposed to O2 at atmospheric pressure and 200−600°C. O-induced changes of surface composition were followed. Oxidation properties of Pt, Pd, Ru and Ir changed on alloying. The Pt-based alloys could be oxidised provided the Pd, Ru or Ir surface concentration was higher than a limit between 13% and 20% for all three systems. Above this limit, the impurity and the Pt atoms were both oxidised. Three different Pt oxidation states were detected PtO, α -PtO2 and β -PtO2. In the low impurity content range, neither impurity nor Pt could be oxidised.
On the Electrical Resistivity of Pt3FexMn1−x Alloys in the Exchange Inversion Region
y. v. yakhmi, i. k. gopalakrishnan and r. m. iyer, J. Phys. Lett., 1984, 45, (16), L-781–L-784
The electrical resistivity ρ as a function of temperature is reported for a series of Pt3FexMn1−x alloys with x = 0, 0.5, 0.6, 0.7, 0.8 and 1.0. The ρ (T) curve for Pt3Fe0.6Mn0.4 shows two ρ -anomalies, one is attributed to the Curie temperature and the other to the transition to a heterogeneous non-colinear magnetic structure.
Low Voltage Hydrogen Plasma Interaction with Palladium Surface
t. d. radjabov, l. ya. alimova and a. v. sharudo, J. Nucl. Mater., 1984, 125, (3), 326–329
H2 penetration, distribution and content in Pd under low voltage glow discharge plasma, depending on plasma component structure (H2, He, Ar and their mixtures), irradiation succession and possible surface structure changes have been investigated by various techniques. The dependence of the H2 permeability through Pd membranes upon the plasma component structure and the preliminary irradiation dose in the inert gas atmosphere has been shown.
On the Friction and Closing Behaviour of Gold and Palladium Alloys. Part 2. The Palladium Alloy System
h. akpolat, h. g. feller and p. veile, Metalloberflaeche, 1984, 38, (10), 448–454
Alloys and sandwich systems based on Pd, with a disc-pin-arrangement were investigated. Friction, rubbing, roughness and surface composition were determined. The results showed a phase, in which the mechanical properties and the dominance of the 4 closing mechanisms changed continuously. All the Pd-Ni layers had selective oxidation of Ni already at 373K, and Ni enriched the surface as Ni oxide.
Some Properties of Amorphous Pd-Si and Pd-Ni-Si Alloys under Hydrogen Pressures of up to 2GPa
s. m. filipek, a. w. szafranski and f. duhaj, J. Less-Common Met., 1984, 101, 299–304
The electrical resistance and thermoelectric power of amorphous Pd85Si15, Pd83Si17, Pd82Si18, Pd72Ni10Si18, Pd63Ni20Si18 and Pd50Ni32Si18 were measured as functions of the hydrogen pressure up to 2GPa. Hysteresis was observed during absorption-desorption cycling for all the Pd-Si alloys and for Pd72Ni10Si18. Both Pd85Si15 and Pd83Si17 became saturated with H at H : Pd ratios of 0.45 and 0.36, respectively, and then exhibited superconducting behaviour with Tc = 1.6K.
Formation of Bulk Metallic Glass by Fluxing
h. w. kui, a. l. greer and d. turnbull, Appl. Phys. Lett., 1984, 45, (6), 615–616
Bulk specimens (0.4−4g) of Pd40Ni40P20 have been undercooled consistently to the glass state with no detectable superficial crystallinity in a molten flux of dehydrated B oxide. The minimum dimensions of the most massive glass specimen so formed was 1.0cm.
On the Structure of Metallic Glasses in the System Palladium with Magnesium, Zinc or Cadmium as Second Component and Phosphorus or Arsenic as Third Component
m. el-boragy, m. ellner and b. predel, J. Less-Common Met., 1984, 102, (1), 67–78
The preparation of various metallic glasses was carried out by the splat cooling method. Phase diagrams of the binary and ternary systems are presented. The ranges of good glass-forming ability are outside 80 : 20 stoichiometry.
Magnetic Properties of Intermetallic Compounds RhMnGe, PdMnGe, Pd1.5Mn0.5Si, Pd1.5Mn0.5Ge and RhMnSi
w. bazela, J. Less-Common Met., 1984, 100, 341–346
The magnetic properties of the polycrystalline title compounds were studied using magnetometric measurements. The first four compounds display ferromagnetic properties at low temperatures, whereas RhMnSi is an antiferromagnet. Their Curie (Néel) temperatures are 622K, 576K, 498K, 392K and 400K, respectively and their magnetic moments are 3.56μ B, 3.165μ B, 2.12μ B, 1.6μ B and 2.6μ B.
Mobility of Pd and Si in Pd2Si
e. c. zingu, j. w. mayer, c. compie and r. pretorius, Phys. Rev. B, 1984, 30, (10), 5916–5922
A diffusion-membrane technique has been developed to determine the mobilities of Pd and Si in Pd2Si. A multilayer film structure Pd/Pd2Si/Ge, in which Ge acts as a sink for Pd is used to monitor the flux of Pd through Pd2Si. The Si flux is determined by using the thin film structure Si/Pd2Si/Cr in which Cr acts as a sink for Si. Values for the Pd and Si mobilities were calculated and good agreement was found between the calculated Pd mobility values and the parabolic rate constant for Pd2Si growth around 200°C.
Profile of Crude Rhodium
h. renner and u. trÖbs, Metall, 1984, 38, (10), 1002–1005
The history of platinum group metals and properties of Rh are explained. Then the geological occurrence of Rh and other platinum group metals is discussed. Present prices of platinum group metals and means of recycling them are given. The recovery of Rh and platinum group metals, the applications and uses of Rh are commented on.
Relationship between the Crystal Structure and the Reentrant Superconducting Properties of (Sn1−x-Erx) Er4Rh6Sn18
s. miraglia, j. l. hodeau, m. marezio, h. r. ott and j. p. remeika, Solid State Commun., 1984, 52, (2), 135–137
Single crystals of (Sn1−xErx)Er4Rh6Sn18 are superconducting (Tc = 1.3K) for x ∼ 0, and are reentrant superconductors (Tc = 1.24K and Tm = 0.34K) for x ∼ 0.30 and undergo a single magnetic transition (Tm = 0.68K) for x ∼ 0.75. Since the occupancy of the [Sn(1)1−xEr(1)x]Er(2)4 sublattice is responsible for the variation of the low temperature properties, predictions can be made as to new reentrant superconductors in the MRhxSny series (M = RE). This seems to be the first system of reentrant superconductors where stoichiometry within a sublattice controls both magnetic ordering and superconductivity.
Magnetic Properties of New Ternary Silicides: Tb2Ir3Si5 and Both Polymorphic Forms of TbIr2Si2
m. hirjak, b. chevalier, j. etourneau and p. hagenmuller, Mater. Res. Bull., 1984, 19, (6), 727–733
New ternary silicide Tb2Ir3Si5 and two polymorphic forms of TbIr2Si2 have been prepared. The three compounds order antiferromagnetically. A high Neél temperature is observed for the low-temperature modification (TN = 80K, θ p = 42K). Tb2Ir3Si5 and the high temperature modification of TbIr2Si2 have low TN and θ p values.
Semiconducting Behaviour of RuGa2
j. evers, g. oehlinger and h. meyer, Mater. Res. Bull., 1984, 19, (9), 1177–1180
RuGa2, with TiSi2 type structure was prepared by inductively heating Ru and Ga in a water cooled Cu boat under Ar. The electrical conductivity of a polycrystalline sample 7 × 5 × 4mm3 was measured from 20−400°C by the four point technique. RuGa2 is a semiconductor with electrical resistivity of 0.2Ω cm at room temperature. RuAl2 and Os2Si3 were also shown to have semiconducting properties.
Effect of Atmosphere on the Electrical Conductivity of RuO2 and Ruthenate Layers
b. ŘemÁk, m. frumar and l. koudelka, J. Mater. Sci. Lett., 1984, 3, (11), 1011–1014
The effects of N2 and O2 on the electrical conductivity of polycrystalline layers of RuO2 and Bi2Ru2O7 pure and doped with an excess of Bi2O3 and RuO2 was studied over a broad temperature range. The electrical resistance of Bi2Ru2O7 layers and ruthenate layers with excess RuO2 and Bi2O3 in the range 20−650°C changes very little, but above 650°C it decreases more steeply. The temperature dependence of resistance of the thick layers of pure RuO2 has a similar shape. N2 exposure increases the resistance of the layers, changing to O2 decreases it.
The Micro-Structure of RuO2 Thick Film Resistors and the Influence of Glass Particle Size on Their Electrical Properties
t. inokuma, y. taketa and m. haradome, IEEE Trans. Components, Hybrids Manuf. Technol., 1984, CHMT-7, (2), 166–175
The microstructure and electrical properties of RuO2 thick film resistors have been studied with emphasis on the effects of material parameters and processing variables, such as size of glass frit particles, RuO2:glass mixing ratio, firing conditions, etc. A network of RuO2 develops in a glass matrix on firing, and the increase in the glass particle size enlarged the cell in the network without any significant change in the microstructure.
Fluorosulfates of the Noble Metals. 5. Fluorosulfato Derivatives of Platinum(IV) and the HSO3F-Pt(SO3F)4 Superacid System
k. c. lee and f. aubke, Inorg. Chem., 1984, 23, (14), 2124–2130
A simple synthetic route to pure Pt(SO3F)4 is described. This compound was found to be an excellent fluorosulphate ion acceptor forming either [Pt(SO3)F6] or an oligometric anion of the composition [Pt(SO3F)5]−. A number of complexes with the counterions Cs+, ClO2+, Ba2+ and were prepared and spectroscopically characterised. The novel dibasic acid H2[Pt(SO3F)6] which undergoes dissociation equilibria was formed in a solution of HSO3F.
Preparation and Characterization of Some Ruthenium (III) Porphyrins, Including the Crystal Structure of Bromo(octaethylporphinato) (triphenylphosphine)ruthenium(III)
b. r. james, d. dolphin, t. w. leung, f. w. b. einstein and a. c. willis, Can. J. Chem., 1984, 62, (7), 1238–1245
Some Ru(III) complexes Ru(porp)(L)X and [Ru(porp)L2]X, (porp = dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP)), (L = PPh3, P11Bu3; X = Br, Cl) were prepared from the precursor complexes Ru(porp)L2 or Ru(porp)(CO)L using as oxidant the halogens or air. The X = PF6 salts can be made using as oxidant, Ru(II) porphyrin π -cation radical intermediates have sometimes been detected.
Preparation and Electrical Conductivity of Bi2Ru2O2 Single Crystals
b.ŘehÁk, k. hoŘcic, m. frumak and l. koudelka, J. Cryst. Growth, 1984, 68, (2), 647–649
Single crystals of Bi2Ru2O2 have been grown by the flux method from a Bi2O3/V2O5 melt. The electrical conductivity of the crystals is of a metallic type, and the major current carriers are electrons.
The Catalytic Thermal Decomposition of Water and the Production of Hydrogen
h. h. g. jellinek and h. kachi, Int. J. Hydrogen Energy, 1984, 9, (8), 677–688
The Pt and Ir catalysed thermal decomposition of H2O has been carried out at 1300−1400°C. The dissociation was very rapid, yielding appreciable quantities of H2 and O2. The great rate of catalytic decomposition compensated for the small degrees of thermal decomposition in this temperature range. Two prototypes for large scale thermal H2 production are proposed and are described in detail. A reasonable number of these prototypes can replace one year’s supply of natural gas by H2 in the U.S.A.
Oxygen Reaction on Titanium Catalysed by Gold, Platinum and Palladium
r. zejniloviĆ, m. pjeŠČiĆ, m. ŠjukiĆ and a. r. despiĆ, J. Appl. Electrochem., 1984, 14, (4), 481–488
The electrocatalytic properties of Ti surfaces coated with small amounts (0.025−0.6mg/cm2) of Pt, Pd and Au and their mixtures, have been investigated during O2 evolution and reduction in alkaline solution. All the samples had higher electrochemical activity than the corresponding compact metal surfaces, which may be ascribed to a larger specific surface area of the dispersed catalysts than of smooth metal surfaces. Dispersed Pd gave the best performance, the potential gap between O2 evolution and reduction at 1mA/cm2 being reduced to 0.66V. No indication of a fast degradation was found.
The State of Pd(II) in Solutions of Sulphuric Acid
e. s. rudakov, a. p. yaroshenko, r. i. rudakova and v. v. zamashchikov, Ukr. Khim. Zh. (Russ. Ed.), 1984, 50, (7), 680–684
Spectrophotometric studies of the state of Pd(II) in H2SO4 solutions showed that Pd(II) is found either as aqueous-ions or as monobisulphate complexes. Stability constants of the complexes in the solution H2SO4 + HClO4 with specific concentration of 8.00 are given at 25 and 80°C. It is shown that aqueousions and monobisulphate Pd(II) complexes in H2SO4 react with H2 at the same rate.
Electrochemical Polarisation of Dispersed Palladium Selenide in Caustic Soda Solutions
a. baeshov, m. z. ugorets, o. i. semina and d. n. nagumanov, Zh. Prikl. Khim. (Leningrad), 1984, 57, (7), 1520–1524
Electrochemical polarisation studies of dispersed Pd selenide made in 4M NaOH at 25°C showed the solid phase reduction of Pd and the electrochemical decomposition of Se into the solution as selenides. The rate of electrochemical decomposition of Pd selenide into NaOH solution was fast and was complete when accompanied by oxidation processes.
Electrochemistry of Coordination Compounds. Part XXI. Electrogeneration and Decay of Rh(PPh3)3 and Rh(PPh3)4
g. zotti, s. zecchin and g. pilloni, J. Electroanal. Chem. Interfacial Electrochem., 1984, 175, (1/2), 241–250
The voltammetric behaviour of Rh(PPh3)3(DME)(ClO4) was studied in 1,2-dimethoxyethane (DME) at the Pt electrode. The formally three-co-ordinate d8 species is reduced in two one-electron reversible processes. The d9 intermediate, Rh(PPh3)3, either undergoes a fast second order reaction producing the dimers [Rh(PPh3)4]2 and [Rh(PPh3)2]2 or co-ordinates one extra phosphine ligand if present, followed by dimerisation.
In-situ Identification of RuO4 as the Corrosion Product during Oxygen Evolution on Ruthenium in Acid Media
r. kÖtz, s. stucki, d. schierson and d. m. kolb, J. Electroanal. Chem. Interfacial Electrochem., 1984, 172, (1/2), 211–219
The corrosion of Ru during O2 evolution in 0.5MH2SO4 was studied using cyclic voltammetry, the rotating ring-disc electrode technique and differential reflectance spectroscopy. Cyclic voltammetric curves show a distinct reduction peak at ∼ + 0.80V vs. S.C.E. in the negative scan provided the positive limit is extended beyond ∼ + 1.2V vs. S.C.E. The voltammetric feature observed at ∼ + 0.80V vs. S.C.E. is attributed to the reduction of RuO4 in solution. It is concluded that the onset of O2 evolution and Ru corrosion takes place at the same potential and thus the reaction pathways of both processes involve a common intermediate.
Hydrogen Evolution and Iodine Reduction on an Illuminated n-p Junction Silicon Electrode and Its Application to Efficient Solar Photoelectrolysis of Hydrogen Iodide
y. nakato, y. egi, m. hiramoto and h. tsubomura, J. Phys. Chem., 1984, 88, (19), 4218–4222
A p-Si electrode, highly doped with P from the surface (n+/p-Si) generated a photocurrent corresponding to I (or triiodide) reduction in a HI/I2 solution at potentials much more positive than those on Pt and p-Si electrodes. The kinetics of the H2 photoevolution were improved by depositing a 0.5−3nm Pt layer on the surface, but the H2 evolution photocurrent gradually decayed under prolonged illumination, and was restored by keeping the electrode in an oxidative condition. Photo-electrochemical cells, with a Pt-deposited n+/p-Si electrode and a Pt counterelectrode electrolysed HI into H and triiodide ions under no externally applied voltage with a high solar to chemical energy conversion efficiency of 7.8% under simulated solar AM 1 radiation.
Photoproduction of Hydrogen by Dye-Sensitized Systems
z.-c. bi and h. ti tien, Int. J. Hydrogen Energy, 1984, 9, (8), 712–722
Visible light induced production of H2 has been investigated in five different systems. Acridine yellow/EDTA/K2PtCl6 was shown to be the best system examined, and when Triton X-100, a nonionic interface agent, was added there was a further enhancement in the rate of H2 evolution.
Photogenerated Catalysis by Transition-Metal Complexes. Photoacceleration of the Valence Isomerization of Quadricyclene to Norbornadiene in the Presence of PdCl2(η 4-norbonadiene)
n. borsub and c. kutal, J. Am. Chem. Soc., 1984, 106, (17), 4826–4828
Light accelerates the rates at which PdCl2(η 4-NBD)(I) catalyses the valence isomerisation of quadricyclene (Q) to norbornadiene (NBD). The observed quantum yield, defined as (mol of NBD produced/mol of photon absorbed), can exceed 102 and is dependent upon Q concentration, light intensity and solvent.
Photocatalytic Dehydrogenation of Propan-2-ol Using Rhodium Based Catalysts
c. g. griggs and d. j. m. smith, J. Organomet. Chem., 1984, 273, (1), 105–109
Efficient photogeneration of H2 from propan-2-ol can be achieved with a number of preformed Rh1 complexes, as well as RhCl3 in the presence of Ph3PO or Ph3P after exposure to air. The turnovers for the Rh1 species are in the range 2000−6000 mmol H2/h.mmol/Rh, which are much higher than those claimed for such photolytic systems. RhCl3 systems have lower activity (∼1000 turnovers).
Effect of the Ru+++ Treatment on the Electrochemical Hydrogen Evolution Reaction at GaAs Electrodes
k. uosaki and h. kita, Chem. Lett. Jpn., 1984, (6), 953–956
The electrochemical H2 evolution reaction (H.E.R.) both at n-GaAs and p-GaAs electrodes in the dark was accelerated significantly by dipping treatment in RuCl3 solution; but the photocurrents at p-GaAs decreased by the treatment. The Ru+++ treatment introduces a catalytic surface for the H.E.R. and also surface states which act as recombination centres.
Redox Polymeric Film Electrode by Electropolymerization of a Pyrrole-Containing Complex of Ruthenium(II)
s. bidan, a. deronzier and j.-c. moutet, Nouv. J. Chim., 1984, 8, (8/9), 501–503
A photosensitive electroactive electrode was obtained by anodic electropolymerisation of the [Ru(bpy)2L2]2+ complex on Pt in which L is a pyrrolic group-substituted pyridine.
Photoredox Reactions in Water-in-Oil Microemulsions. The Functions of Amphiphilic Viologens in Charge Separation and Electron Transfer across a Water-Oil Boundary
d. mandler, y. degani and i. willner, J. Phys. Chem., 1984, 88, (19), 4366–4370
The photosensitised reduction of a series of dialkyl-4,41-bipyridinium salts, CnV2+ was examined in water-in-oil microemulsions, by using as sensitiser and (NH4)3EDTA as electron donor. With the amphiphilic electron acceptors (n = 8−18), these microemulsion media affect the charge separation of the initial encounter cage complex and stabilise the photoproducts, CnV+. and against the recombination process. Consequently, enhanced quantum yields for CnV+. formation are observed.
ELECTRODEPOSITION AND SURFACE COATINGS
New Platinum Plating Process Ensures Numerous Fields of Application for Platinised Anodes
h. heiner, Galvanotechnik, 1985, 75, (10), 1271–1272
Platinising by electrolysis in the melt at temperatures >500°C in an inert gas atmosphere gives coatings which are distinguished by high adhesion, ductility and freedom from porosity. This enables platinised refractory metals, such as Ti, Nb and others to be used for manufacturing insoluble anodes for use in acid electrolytes. Their use is particularly good as expanded metal, as the actual anode surface is greater than the geometrical one.
Pulsed Current Electrodeposition of Palladium
y. fukumoto, y. kawashima, k. manda and y. hayashi, Met. Finish., 1984, 82, (9), 77–80
Electrodeposition of Pd from dinitrodiamine, dibromodiamine and dichlorodiamine baths has been performed by applying pulsed current electrolysis. A close correlation was found between crystallographic features of the Pd deposits and the mode of the pulse current. A decrease in grain size of the deposits was observed by using higher pulse current density, longer pulse on-time and shorter off-time which lead to higher cathodic overpotentials. Although desorption of H2 from the Pd deposits was expected during off-time, this did not always occur.
Palladium-Nickel Coating System for High Reliability Connectors
s. w. updegraff, Electron. Ind., 1984, 10, (9), 43, 45–46, 48
The properties which make a Pd-Ni alloy system superior to gold for application to connectors are reviewed. The Pd-Ni is plated onto square pin connectors, and then plated with gold flash.
Study of the Composition of Olefins Formed in Conditions of Dehydrogenation of n-Decane on Pt/Al2O3
g. v. isagulyants, o. d. sterligov, a. p. barkova, i. p. yakovlev, m. a. panfilova, l. k. maslova and n. a. elissev, Izv. Akad. Nauk SSSR, Ser. Khim., 1984, (9), 2049–2053
The effect of catalyst composition and of the reaction conditions on the ratio of n-decene (with various positions of the double bond) formed during dehydrogenation of n-decane was studied on Pt/Al2O3 catalysts modified by MnO. Amount of α, cis- and trans-decene, formed during dehydrogenation of n-decane was on average in the ratio of 1:8:11, respectively, and no dependence on the catalyst composition was observed. Decenes with internal double bonds were predominantly formed.
Activity, Yield Patterns, and Coking Behaviour of Pt and PtRe Catalysts during Dehydrogenation of Methylcyclohexane. I. In the Absence of Sulfur. II. Influence of Sulfur
r. w. coughlin, k. kawakami and a. hasan, J. Catal., 1984, 88, (1), 150–162; 163–176
The conversion of methylcyclohexane decreased less rapidly while selectivity and aromatic yield increased more rapidly over a 20h period with PtRe/Al2O3 than with Pt/Al2O3. Coke deposition was retarded on the PtRe as compared to the Pt catalysts. After H2 treatment selectivity and aromatic yield were lower for PtRe than Pt catalyst. Adding small amounts of S lowers hydrocracking for both Pt and PtRe. S retards deactivation of the dehydroaromatisation activity of PtRe catalysts more significantly than for monometallic Pt catalysts.
Kinetics of the Catalytic Decomposition of Hydrogen Iodide in the Thermochemical Hydrogen Production
y. shindo, n. ito, k. haraya, t. hakuta and h. yoshitome, Int, J. Hydrogen Energy, 1984, 9, (8), 695–700
The decomposition rates of HI over Pt/γ -Al2O3 were measured in the temperature range of 480–700K by a flow method. HI decomposed to H2 and I2 and an overall rate equation was obtained according to the Langmuir-Hinshelwood model, assuming the rate determining step was a surface reaction.
Peculiarities in the Conversion of Naphthenes on Bifunctional Catalysts
j. weitkamp, s. ernst and h. g. karge, Erdoel Kohle Erdgas Petrochem., 1984, 37, (10), 457–462
The differences between the reactions of naphthenes and alkanes on bifunctional catalysts are reviewed and some peculiar results from a bifunctional mordenite catalyst are examined. Ideal bifunctional catalysts are Pt/SiO2-Al2O3, Pt/CaY zeolite, Pt/ultrastable Y zeolite and Pd/LaY zeolite. (39 Refs.)
Rapid Determination of Heavy Water Concentration by Isotopic Exchange Reaction between Liquid Water and Hydrogen Using Hydrophobic Platinum Catalyst
t. takahashi, s. ohokoshi, n. shinriki and t. sato, Bunseki Kagaku, 1984, 33, (5), 233–236
A 2% Pt coated on HD4 type styrene-divinyl benzene copolymer was used as catalyst to promote the H2-D2 exchange reaction at room temperature and atmospheric pressure. The catalyst did not lose its activity for a long time after contact with water because it is hydrophobic. On losing its activity it can be easily reactivated. The catalyst was used in a gas chromatographic method for the rapid easy determination of heavy water in light water, in concentrations 0.01−99.5%.
Hydrogenation of Acetone to Isopropanol with High Efficiency and Selectivity at 330K over Pt-TiO2
j. cunningham and g. h. a. sayyed, Nouv. J. Chim., 1984, 8, (7), 469–474
The preparation of finely dispersed Pt on TiO2 and various pretreatments to confer high activity for selective hydrogenation of acetone vapour to isopropanol at 330K are described. With optimum values of partial pressures and Pacetone in the Ar carrier gas 75% conversions with selectivites ≥98% were achieved and maintained. Conversion decreased with the reciprocal of the flow rate. H2 dissociation took place at sites involving Pt and acetone attack occurred on TiO2. Effects of differences in Pacetone and the temperature of prereduction were examined. This catalyst has enhanced catalytic activity at 330K.
n-Hexane Isomerisation and Toluene Disproportionation in the Presence of Modified Platinated Zeolites
kh. dimitrov, r. dimitrova, z. popova, k.-g. shchainberg, a. peters and k. g. nestler, Akad. Nauk SSSR, Neftekhim., 1984, 24, (3), 335–339
Studies made of n-hexane isomerisation and toluene disproportionation in the presence of 0.5wt.% Pt/zeolite catalysts modified by addition of REE (REE = mixture of ∼25% Pr, 55% Nd and 20% La) and of Mn2+ cations into CaNaY zeolite showed improved catalytic properties. Zeolites REE CaNaY were found to be active during n-hexane isomerisation and MnCaNaY zeolites during toluene disproportionation.
Kinetic Analysis of Complex Catalytic Reactions
g. f. froment, Bulg. Acad. Sci., Commun. Dep. Chem., 1984, 17, (1), 28–43
Reaction rate data can be obtained in either differential or integral reactions. Examples are given for hydroisomerisation and hydrocracking of n-paraffins on a Pt/ultrastable-Y-zeolite, for catalytic cracking of gas oil on zeolites and for naphtha reforming on Pt/Al2O3. (55 Refs.)
Molecular Clusters. Applications in Homogeneous and Heterogeneous Catalysis
m. dorbon, Rev. Inst. Fr. Pet., 1984, (4), 497–515
An overview of the metal cluster catalysts in heterogeneous and homogeneous reactions is presented. Various Pt, Pd, Rh, Os, Ir and Ru clusters and their structures and reactions are examined. A general examination of clusters in catalysis, catalysis mechanisms and Fischer-Tropsch syntheses are presented. Olefin hydrogenations and H2 displacement from H2O are examined. The view is taken that cluster chemistry is new and vast and that the catalytic properties of clusters have shown remarkable activity.
Oxidation of Formic Acid in Aqueous Solution of Palladium Catalysts
b. claudel, m. nueilati and j. andrieu, Appl. Catal., 1984, 11, (2/3), 217–225
Studies of liquid phase oxidation of formic acid by O2, both dissolved in H2O, were made in the presence of supported and non-supported Pd catalysts at 100−150°C. Determination of diffusional limitations allows an investigation of the rate law in the chemical regime. Appreciable conversions can be reached with a Pd content as low as 50 ppm.
The Influence of High Methane Concentration on the Stability of Catalytic Flammable-Gas Sensing Elements
s. j. gentry and p. t. walsh, Sens. Actuators, 1984, 5, (3), 229–238
Studies were made of the effect of the form of the Pd catalyst used in catalytic flammable-gas sensing elements on their stability following exposure to high methane concentration. Improvement in stability to coking effect was achieved either by depositing Pd on a high surface-area support or by using a co-precipitation of Pd and Th. The apparent H solubilities of a series of Pd+ThO2 elements with different Pd:ThO2 ratios were determined by a temperature-programmed technique. The role of ThO2 as a coke prevention agent is to decrease the Pd particle size which results in a lower rate of methane decomposition.
Reduction of NO by H2-CO Mixtures over Silicon-Supported Rhodium:Infrared and Kinetic Studies
w. c. hecker and a. t. bell, J. Catal., 1984, 88, (2), 289–299
The kinetics of NO reduction by H2-CO mixture was studied over a Rh/SiO2 catalyst. The presence of CO retards the rate of NO reduction presumably due to competitive adsorption with H2. The catalyst activity is 50% higher when the catalyst is preoxidised rather than prereduced. NH3 formation is suppressed when the catalyst is preoxidised and a product believed to be HNCO is formed instead of urea. In situ i.r. spectra of the catalyst show that at NO conversion below 70% the surface is dominated by adsorbed NO.
Alcohol Synthesis from Syngas on Ruthenium-Based Composite Catalysts
m. inoue, t. miyake, y. takegami and t. inui, Appl. Catal., 1984, 11, (1), 103–116
Hydrogenation of CO on Ru-Mo-Na and related catalysts was studied at 255°C and 86kg/cm2 pressure. A series of straight chain primary alcohols, together with hydrocarbons were formed on the catalysts. A Ru-Fe-Na/Al2O3 catalyst had considerable activity for the formation of higher alcohols, but it gave a low alcohol selectivity. Ru-Mo-Na/active C and Ru-Mo-La/Al2O3 had high activity for alcohol synthesis, but 70% of this alcohol was CH3OH. The Ru-Mo-Na/Al2O3 catalyst prepared from RuCl3 was preferable to the other catalysts.
The Platinum Complex Catalyzed Transformation of Primary Amines to Secondary Amine
y. tsuji, j. shida, r. takeuchi and y. watanabe, Chem. Lett. Jpn., 1984, (6), 889–890
The novel catalysis by a homogeneous Pt catalyst is described. In combination with SnCl2.2H2O it activates a primary amine and catalyses the transformation to secondary amine at 180°C. Dibutylamine was obtained from butylamine in 74% yield.
Tetrahedron Report Number 166: Palladium (II) – Assisted Reactions of Monoolefins
l. s. hegedus, Tetrahedron, 1984, 40, (13), 2415–2434
The two major reaction types of Pd(II)-complex-catalysis of olefins, the nucleophilic attack of Pd(II) complexed olefins, and insertion of olefins into σ -alkylpalladium(II) species are discussed. Nucleophiles reacted include O, N and C, whilst insertion reactions involving oxidative addition, transmetallation and “ortho-palladation” are discussed. (74 Refs.)
Regioselective Synthesis of 1-Olefins by Palladium-Catalyzed Hydrogenolysis of Terminal Allylic Compounds with Ammonium Formate
j. tsuji, i. shimizu and i. minami, Chem. Lett. Jpn., 1984, (6), 1017–1026
Various terminal allylic compounds, such as allylic esters, phenyl ethers, carbonates, chlorides and vinyl epoxides react with ammonium on Na formate to give 1-olefins with high regioselectivity using Pd tributylphosphine complex as catalyst.
Selective Palladium Catalysed Mono-hydroesterification of Diols
s. b. fergusson and h. alper, J. Chem. Soc., Chem. Commun., 1984, (20), 1349–1351
Olefins react with diols under oxidative carbonylation and acidic conditions, using Pd and Cu(II) chloride as catalysts, to give hydroxy esters.
Aromatic Hydroxylation: the Direct Oxidation of C-Pd into C-OPd
a. k. mahapatra, d. bandyopadhyay, p. bandyopadhyay and a. chakravorty, J. Chem. Soc., Chem. Commun., 1984, (15), 999–1000
The C-Pd bond in cyclopalladated azobenzenes can be converted into the C-OPd function in good yield by stoichiometric reactions with m-chloroperbenzoic acid. In effect azobenzene is oxidised to 2-hydroxyazo benzene and 2,21-dihydroxyazobenzene.
Synthesis of Esters by Rhodium (I) Catalyzed Borate Ester-Benzylic Bromide Carbonylation Reactions
j. b. woell and h. alper, Tetrahedron Lett., 1984, 25, (35), 3791–3794
Studies of the benzylic halides reaction with trialkylborates and CO in the presence of 1,5-hexadiene Rh chloride dimer showed the production of esters in excellent yields. The reaction is applicable to the synthesis of primary, secondary and even tertiary esters.
Hydroformylation of Propene Catalyzed with Carbonylchlorobis(triphenyl-phosphine) Rhodium (I)
m. polievka, a. jegorov, l. uhlar and v. macho, Collect. Czech. Chem. Commun., 1984, 49, 1677–1679
The effect of amines, amino acids, N heterocyclic compounds and urea derivatives on the rate of the Rh(CO)Cl(PPh3)2 catalysed hydroformylation of propene was studied. A positive effect on the catalytic activity was found with modifying ligands of very low basicity.
Carbonylation with Homologation Reactions of Formic and Higher Molecular Weight Carboxylic Acid Esters with Ruthenium Catalysts
g. brace, g. gualnal, a. m. raspolli, g. sbrana and g. valentini, Ind. Eng. Chem., Prod. Res. Dev., 1984, 23, (3), 409–417
The carbonylation and homologation of formic and higher molecular weight carboxylic acid esters catalysed by Ru carbonyl iodide systems at 200°C and under a CO/H2 pressure of 15−20MPa was studied. The catalyst was active in the hydrogenation of the formyl moiety of methyl formate to methyl derivatives and in carbonylation and homologation.
Ruthenium-Catalyzed Oxidation of Alcohols and Catechols Using t-Butyl Hydroperoxide
y. tsuji, t. ohta, t. ido, h. minbu and y. watanabe, J. Organomet. Chem., 1984, 270, (3), 333–341
Ru complexes catalyse the oxidation of alcohols into the corresponding ketones or aldehydes when t-BuOOH (70% aqueous) is used as an oxidant. The reactions proceed at room temperature to give the products in good yields. RuCl2(PPh3)3 had the highest catalytic activity.
Water-Gas Shift Reaction over Ruthenium Carbonyl Complexes Anchored to Silica via Phosphine Ligands
y. doi, a. yokota, h. miyake and k. soga, Inorg. Chim. Acta, Artic. and Lett., 1984, 90, (1), L7–L9
The synthesis of Ru carbonyl complexes, anchored to SiO2 via phosphine ligands, Ru(CO)4(PPh2C2H4-SIL)(1) and H4Ru4(CO)8(PPh2C2H4-SIL)4(2), and their catalytic properties for the water gas shift reaction are reported. The i.r.spectra of both of the used catalysts were almost identical with their original complexes. Catalyst (2) could be reused without any loss of catalytic activity. Complex (1) exhibited a high catalytic activity for the water gas shift reaction.
Functional Metal-Porphyrazine Derivatives and Their Polymers. Part 11. Secondary Fuel Cells based on Oxygen Reduction at a Platinum Electrode Modified by Metal-2,9,16,23-Tetracarboxyphthalocyanine Covalently Bound to Poly(2-vinylpyridine-styrene)
o. hirabaru, t. nakase, k. hanabusa, h. shirai, k. takemoto and n. hojo, J. Chem. Soc., Dalton Trans., 1984, (8), 1485–1489
A new type of secondary fuel cell is described in which O2 evolved by electrolysis of H2O in the charging process is stored in the polymer matrix of metal-2,9,16,23-tetracarboxyphthalocyanine covalently bound to poly(2-vinylpyridine-styrene) (M = FeIII, CoII, NiII and CuII) on a Pt electrode and then electrocatalytically reduced in the discharging process in 30% KOH aqueous solution. For this cell, there was no significant decay in its characteristics after over 30 charge-discharge cycles.
ELECTRICAL AND ELECTRONIC ENGINEERING
Enhanced Quantum Efficiency of Pd2Si Schottky Infrared Diodes on <111> Si
r. c. mckee, IEEE Trans. Electron Devices, 1984, 31, (7), 968–970
A two-fold improvement in the i.r. emission efficiency has been obtained on Pd2Si/p-Si Schottky diodes through using <111> Si for the substrate orientation. Photo response measurements were taken for <111> Si and <100> Si. Leakage current vs. temperature measurements at 6V reverse bias of the Pd2Si/p-Si <111> diodes with guard ring structures, agreed with thermionic emission leakage current theory, using barrier value 0.35 eV obtained by photo response. These results have implications for detection applications.
Search for Thermometers with Low Magnetoresistive Effects: Platinum-Cobalt Alloy
f. pavese and p. cresto, Cryogenics, 1984, 24, (9), 464–470
A systematic set of measurements on Pt-Co thermometers of difference Co concentrations have been performed at 2-28K and up to 6T. Also three commercial thermometers with 0.5wt% Co were used. Pt-Co alloy, with 0.5at.% Co was insensitive to magnetic fields within ±0.5K down to 4K and up to 4T, or within ±0.2K above 10K and below 3T. Among high-stability thermometers presently available Pt-Co alloy showed the least error in magnetic field at fields of a few teslas.