Platinum Metals Rev., 1983, 27, (3), 133
ABSTRACTS: July 1983
of current literature on the platinum metals and their alloys
Drastic Reduction of Adsorption of CO and H2 on (111)-Type Pd Layers
h. poppa and f. soria, Phys. Rev. B., 1983, 27, (8), 5166–5168
Clean surfaces of (111)-type Pd layers, grown from the vapour phase on Mo(110) at room temperature were used to study the adsorption of CO and H2 by various techniques. Mild annealing of the as-grown layers during a single desorption cycle (to ∼600K) drastically reduces the adsorptions. Low-dose Ar+ bombardment restores high adsorption probability.
Photographic Properties of Palladium-Containing TiO2 Layer under Nickel Physical Development
v. v. sviridov, n. i. kuntsevich, g. a. sokolik and i. n. evtukhovich, Vestn. Akad. Nauk BSSR, Ser. Khim. Nauk, 1983, (1), 30–35
The photographic properties of Pd-containing TiO2-layers under Ni development depends on the Pd concentration in the layer, TiO2 preparation conditions and on the development conditions. Both negative and positive images can be obtained depending on the Pd2+ content.
A Study of the Palladium-Platinum-Hydrogen System over a Wide Range of Hydrogen Pressures
b. baranowski, f. a. lewis, w. d. mcfall, s. filipek and t. c. witherspoon, Proc. R. Soc. London, 1983, 386A, 309–332
Measurements of changes in electrical resistivity in Pd-Pt alloys caused by absorption of H2 at 30 kbar pressures, were made at 25−70°C. Substantial resistivity changes due to H2 absorption occur over increasingly higher ranges of pressure with increasing Pt contents. There is a gradually accelerating increase of resistivity with increasing H2 pressure up to maximum values, followed by a decrease back to close to initial H2-free values. An extrapolation of results suggests it may be possible to attain a solid solution of H2 in pure Pt up to a composition of ∼PtH0.25 at H2 pressures of ∼100 kbar at 25°C.
Properties and Electron Transfer Reactivity of Coordination Compounds for the Photochemical Splitting of Water
l. moggi, NTIS, Chemistry, 3 May 1983, 426
Photochemical, photophysical and electrochemical properties have been determined for the excited states of many polypyridine complexes of Rh(III), Ir(III), Ru(II), Os(II) and Cr(III) for use in cyclic photochemical systems for the splitting of water.
Blue Sputtered Iridium Oxide Films (Blue SIROF’s)
k. s. kang and j. l. shay, J. Electrochem. Soc., 1983, 130, (4), 766–769
“Blue” sputtered Ir oxide films (blue SIROF) were prepared and compared with “black” SIROF’s and anodically grown Ir oxide films (AIROF’s). Blue SIROF’s are prepared by reactive d.c. sputtering of Ir in an Ar : O2, 80 : 20 mixture, at deposition rates of ∼200 Å/min on substrates held at 238K. Blue SIROF’s have similar physical properties to AIROF’s. In contrast to SIROF’s previously deposited in pure O2 onto substrates held at 289K the new films have an optical absorption spectrum which peaks at 610nm. The blue SIROF’s have an improved open-circuit bleached state and memory.
Oxidation of Ruthenium
s. p. sharma and l. l. hines, IEEE Trans. Components, Hybrids, Manuf. Technol., 1983, CHMT-6, (1), 89–92
Ru has been heated in air at 100−400°C to find its usefulness as an electrical contact. At up to 200°C Ru oxidises to produce a film which causes high contact resistance. Above 300°C Ru forms an oxide film RuO2 which has low contact resistance. The film <200°C is a lower Ru oxide (probably RuO).
Preparation, Electrical Resistivity and Its Temperature Dependence of RuO2-Polystyrene Composite Powder
t. nishizawa, m. senna and h. kuno, J. Mater. Sci., 1983, 18, (5), 1346–1352
RuO2-polystyrene composite powder was prepared by mixing fine powdered RuO2 and PS beads thoroughly in ethanol. RuO2-coated PS beads were also prepared by direct suspension polymerisation of styrene in an acqueous phase in the presence of suspended RuO2 powder. The apparent d.c. volume resistivity, ρ a, of the hot-pressed composite was measured from 20−80°C, pressure 3.5–35 MPa and volume fractions of RuO2. ρ a increased linearly with temperature on a double logarithmic scale. The composite prepared by direct polymerisation completed a network of the conductive phase at a smaller fraction of RuO2.
Ion Mixing to Produce Amorphous Mo-Ru Superconducting Films
Chemistry of Triosmium Carbonyl Cluster Compounds and Its Implications for Catalysis
r. d. adams, Acc. Chem. Res., 1983, 16, (2), 67–72
A study of a series of triosmium carbonyl cluster complexes formed by the addition of a variety of small heteronuclear unsaturated molecules to the cluster complex H2Os3(CO)10(I) is presented. The reactions of (I) with isocyanides, nitriles, aryl isocyanates, carbodiimides, aryl isothiocyanates and CS2 are described. The evidence suggests that cluster compounds have unique chemical properties allowing development as a new class of reaction catalysts.
Transient Behaviour in Electroreductions of Ethylene and Acetylene on Pt in H2SO4 Solution
t. masui and h. kita, Denki Kagaku, 1983, 52, (2), 250–255
Studies were made of transient behaviour in electroreductions of C2H4 and acetylene on a Pt electrode. Open circuit potential measurements under the contact of the electrode prepolarised at oV with C2H4 and acetylene showed that from the three kinds of adsorbed H atoms on Pt the second stable one takes part in the reactions, while the most stable one is inactive.
Crystallographic Anisotropies in Electrochemical Etching of Pt
r. caracciolo and l. d. schmidt, J. Electrochem. Soc., 1983, 130, (3), 603–607
Single crystal microspheres of Pt are examined by SEM after electrochemical and chemical etching in chloride and cyanide solutions. In all cases, a single major crystal plane is formed which is not the close packed (111) plane. Electrochemical chloride etching with a.c. potentials produces large smooth planes near (100), and the (111) plane is attacked readily to form (100) facets.
Electroreduction of Acetone on Pt-Ni Catalysts
a. d. semenova, a. i. barkovskii and g. d. vovchenko, Vestn. Mosk. Univ., Khim., 1983, 24, (2), 159–162
Studies of adsorption and catalytic properties of metallic Pt-Ni alloys were made during electroreduction of acetone in 1N KOH at 25°C. Analysis of polarisation curves of the electroreduction on Pt, Ni and Pt-Ni alloys showed that alloys containing >60 at.% Pt have a form of curves similar to Pt and Ni, whereas alloys containing <50 at.% Pt have different forms of curves. It is concluded that ordered atoms in Pt-Ni system give higher catalytic activity. Alloys in equiatomic systems have 6 times higher activity than Pt in the studied reaction.
Anodic Characteristics of Amorphous Palladium-Iridium-Phosphorus Alloys in a Hot Concentrated Sodium Chloride Solution
m. hara, k. hashimoto and t. masumoto, J. Non-Cryst. Solids, 1983, 54, (1, 2), 85–100
The corrosion resistance and electrocatalytic activity for Cl2 and O2 evolutions at amorphous Pd-Ir-P alloys containing a small amount of Ti, Rh, Pt and/or Ru in hot concentrated NaCl solution were investigated. The electrocatalytic activity of several amorphous alloys for Cl2 evolution was much higher than that of dimensionally stable RuO2/Ti anodes, while their catalytic activity for O2 evolution was lower than that of the RuO2/Ti electrode, suggesting amorphous alloys can produce high purity Cl2 at high efficiencies.
Interfacial Properties of Oxides Used as Anodes in the Electrochemical Technology
a. daghetti, g. lodi and s. trasatti, Mater. Chem. Phys., 1983, 8, (1), 1–96
A review of surface chemistry of oxides and the behaviour of the relevant insoluble oxides is presented. The oxides are the components of electrodes used in chlor-alkali cells, water electrolysis, electroorganic oxidations, metal electrowinning and cathodic protection. Oxides discussed include RuO2 and IrO2. (492 Refs.)
Ruthenium Behaviour during Electrochemical Dissolution of Its Binary Alloys with Copper
v. f. borbat, o. v. zavel’eva and m. a. orlov, Izv. Vyssh. Uchebn. Zaved., Tsvetn. Metall, 1983, (2), 54–57
Studies of Ru behaviour during electrochemical dissolution of Cu-Ru binary alloys containing 0.004% and 0.01−0.03% Ru were made in solutions of H2SO4 and CuSO4 of various acidities by anodic polarisation measurements. Anodic polarisation curves rose in more electropositive areas with the increase of the Ru content in the alloy. An increase in acidity resulted in dissolution of Ru into the solution, and at 1.4V the dissolution of Ru in 4N H2SO4 + 1.5N CuSO4 was nearly complete. The rate of dissolution of Ru in the electrolyte was found.
XPS Studies of Oxygen Evolution on Ru and RuO2 Anodes
r. kötz, h. j. lewerenz and s. stucki, J. Electrochem. Soc., 1983, 130, (4), 825–829
Anodic oxidation of Ru and RuO2 electrodes in 1N H2SO4 has been investigated using XPS. During O2 evolution of Ru, a highly defective hydrate oxide film is formed as a result of corrosion. At 310°C in vacuum this film decomposes to metallic Ru. The surface of RuO2-anodes prepared by thermal decomposition of RuCl3 contains some RuO3 which is stable during anodic polarisation.
Photo-Induced Hydrogen Evolution Accelerated at Semiconductor/Liquid Interface
t. shimidzu, t. iyoda, y. koide and n. kanda, Nouv. J. Chim., 1983, 7, (1), 21–27
A novel water photoreduction system is presented, where an appreciable quantity of H2 is catalytically produced by visible light illumination in neutral aqueous solution containing an appropriate electron donor, platinised semiconductor power and a water soluble Zn porphyrin. The ZnTPPS4-ZnO/Pt-TEA system showed the highest catalytic activity. A platinised semiconductor powder plays the role of an excellent electron relay and redox catalyst for H2O reduction.
Factors Influencing Product Distribution in Photocatalytic Decomposition of Aqueous Acetic Acid on Platinized TiO2
h. yoneyama, y. takao, h. tamura and a. j. bard, J. Phys. Chem., 1983, 87, (8), 1417–1422
Reaction products of the photocatalytic decomposition of acetic acid/acetate mixtures at Pt/TiO2 were examined. The relative yield of C2H6:CH4 produced was high when the decomposition rate was high, and the amount of CO2 produced usually exceeded that of the methyl radical consumed in the formation of CH4 and C2H6. Ethanol and acetaldehyde were produced. The production occurred even under adverse conditions, and even when a very high acidic bias completely suppressed any cathodic reaction CH4 was produced in higher yields than C2H6.
Photoassisted Water-Gas Shift Reaction over Pt/TiO2 (100)
s.-c. tsai, c.-c. kao and y.-w. chung, J. Catal., 1983, 79, (2), 451–461
Saturated H2 production was observed over platinised TiO2 (100) in the presence of H2O vapour and CO with or without u.v. illumination. The thermal reaction is dominant at temperatures over 400K. Below 400K the photoreaction is dominant, and is independent of H2O and CO partial pressures in the range 0.5 to 18 Torr and 0.1 to 10 Torr, respectively. Reaction rate increases monotonically with increasing u.v. intensity.
Hydrogen Generation by Photocatalytic Oxidation of Gases by Platinized n-TiO2 Powder
m. r. st. john, a. j. furgala and a. f. sammells, J. Phys. Chem., 1983, 87, (5), 801–805
The photocatalytic reaction of glucose in aqueous solution containing platinised n-TiO2 powder occurred at pH = 4.5. Under an inert atmosphere H2 and CO2 were produced, but under an O2 atmosphere, only CO2 was produced. For a 2.8M glucose solution and at 60°C, the initial H2:CO2 ratio was near 10, but decreased to near 3 at times >100 hours. Gas evolution rates were determined.
Semiconductor Electrodes. 48. Photooxidation of Halides and Water on n -Silicon Protected with Silicide Layers
f.-r. f. fan, r. g. keil and a. j. bard, J. Am. Chem. Soc., 1983, 105, (2), 220–224
The electrochemical and photoelectrochemical behaviour of n-type Si electrode coated with noble metal silicides and RuO2 in aqueous solutions containing various redox couples was studied. Ir silicide coated n-Si electrodes, n-Si(Ir), and RuO2-modified n-Si(Ir) electrodes can photogenerate I2, Br2 and Cl2 with high stability and efficiencies (75%). The photooxidation of H2O on these electrodes is also feasible.
ELECTRODEPOSITION AND SURFACE COATINGS
Changing Concepts in the Electroplating of Platinum Group Metals – Part 1
h. m. smith, Met. Finish., 1983, 81, (3), 55–58
Electrodeposits of Pt, Pd, Rh and Ru, are discussed. Properties, electroplating applications and an analysis of platinum group metals in industry are examined. Physical properties reviewed include internal stresses, reflectance, corrosion and solubility, wear resistance, contact and arc resistances, electrical resistivity, solderability and thermal expansion.
The Electrolytic Deposition of Pd-NiCoatings from an Ammoniacal Electrolyte
m. butz, f. friedrich and ch. j. raub, Metalloberflaeche, 1983, 37, (3), 89–93
Factors connected with the electrolytic deposition of Pd-Ni coatings from an ammoniacal electrolyte are examined. These include the plating bath conditions, the composition of the deposit, temperature and pH, the H content in the deposit, internal voltages and deposit thicknesses. The use of a high deposition rate is also considered. The H content of the deposits is a strong indicator of the working conditions.
LABORATORY APPARATUS AND TECHNIQUE
Urea Sensor Based on Iridium Dioxide Electrodes with Immobilized Urease
r. m. ianniello and a. m. yacynych, Anal. Chim. Acta, 1983, 146, 249–253
An IrO2 electrode with immobilised urease was found to be useful as a potentiometric detector for pH changes resulting from hydrolysis of urea at the electrode surface. Electrodes constructed by urease entrapment in a PVC film are superior to electrodes with urease covalently immobilised to the oxide layer via a cyanuric chloride linkage. Logarithmic response is obtained for the range 5 × 10−5−5 × 10−3M urea, with a slope of −51 mV/decade. The slope is constant for ∼12 days. Recoating a stripped electrode with PVC-urease has essentially no effect on the slope.
Effects of Impurities on Hydrogen Permeability through Palladium Alloy Membranes at Comparatively High Pressures and Temperatures
h. yoshida, s. konishi and y. naruse, J. Less-Common Met., 1983, 89, (2), 429–436
The Pd alloy membrane method was studied as a means for purifying fusion reactor fuel by investigating the effects of impurities on the permeation characteristics, at high pressures and temperatures, of Pd alloys. The H2 permeability of Pd-25wt.%(Ag-Au-Ru) was not affected by impurities such as NH3, CH4, CO, CO2 and N2 which are present at concentrations 10−10,000ppm in H2. However, permeability deteriorates on contamination with oil vapour, but is easily recovered.
A Proposed Method of Hydrogen Isotope Separation Using Palladium Alloy Membranes
j. evans, i. r. harris and d. k. ross, J. Less-Common Met., 1983, 89, (2), 407–414
The viability of using Pd alloy membranes in cascade to separate the H, D and T produced in a fusion reactor is discussed. Values of the permeation separation factor are estimated for Pd-20%Ag, and estimates for the number of stages and membrane area are given for the required isotope purification. Using Pd-8%Y will probably even further improve the performance.
Palladium-Catalyzed and Sonically Accelerated Hydrogenations of Olefins Using Formic Acid as a Hydrogen Transfer Agent
p. boudjouk and b.-h. han, J. Catal., 1983, 79, (2), 489–492
In the presence of Pd/C, formic acid is a very efficient H donor at room temperature. Ten olefins, including terminal and internal alkenes, a diene, a vinyl ether and an α, β -unsaturated ketone were hydrogenated in high yields at room temperature and atmospheric pressure. In the presence of sonic waves, the rate of hydrogenation was significantly increased.
Oxidation of Polyunsaturated Ethers and Esters with Molecular Oxygen Catalysed by Palladium Salts
g. a. dzhemileva, v. n. odinokov, u. m. dzhemilev and g. a. tolstikov, Izv. Akad. Nauk SSSR, Ser. Khim., 1983, (2), 343–348
Studies of oxidation of polyunsaturated ethers and esters with O2 over PdCl2-CuCl catalysts showed the formation of a series of new mono,-di- and triketoesters. A synergetic effect in quaternary ammonium salts was observed during O2 oxidation and was followed by an increase in the yield of carbonyl compounds.
On the Properties of Monodispersed Pd/MgO Catalysts
g. d. zakumbaeva, n. a. zakarina, v. a. naidin, a. m. dostiiarov, n. f. toktabaeva and e. n. litviakova, Kinet. Katal., 1983, 24, (2), 449–453
Microcalorimetric studies of adsorption of H2 and O2 on mono-(25−75Å) and polydispersed Pd/MgO catalysts showed an increase in adsorption temperature of H2 and O2 with the decrease of Pd particle diameter. Selectivity and activity of Pd catalysts was found to depend on its dispersity and level of Pd reduction.
An Active Methanation Catalyst Prepared from an Amorphous Pd35Zr65 Alloy
a. yokoyama, h. komiyama, h. inoue, t. masumoto and h. kimura, Chem. Lett., 1983, (2), 195–198
A highly active methanation catalyst was prepared in situ from an amorphous Pd35Zr65 alloy. In the reaction at 260°C and 1 atm the catalytic activity had a 100-fold increase with time and after 60 hours had a steady value, compared to the initial value.
Palladium Alloys as Hydrogen Permeable Catalysts in Hydrogenation and Dehydrogenation Reactions
v. m. gryaznov, m. m. ermilova, l. s. morozova, n. v. orekhova, v. p. polyakova, n. r. rosham, e. m. savitsky and n. r. parfenova, J. Less-Common Met., 1983, 89, (2), 529–535
H2 permeation across a binary Pd alloy catalyst (Pd alloyed with Al, Ti, Ni, Cu, Mo, Ru, Rh, Ag, In, W, Re, Pt) enhances the rate and selectivity of hydrogenation compared with what is observed when the compound being hydrogenated is mixed directly with H2. The principal product of diene hydrogenation when the H2 permeates through a membrane catalyst is not a saturated hydrocarbon but the corresponding olefin from which polymers can be synthesised.
Water Gas Shift Reaction Catalyzed by Iridium Complexes Supported on Zeolites
r. ganzerla, f. pinna, m. lenarda and m. graziani, J. Organomet. Chem., 1983, 244, (2), 183–189
Ir compounds, supported on 13-X faujasite type zeolite catalyse the water gas shift reaction. During the reaction carbonyl complexes are formed and are detected by i.r. spectroscopy. Addition of ethylene diamine enhances the catalytic activity.
Synthesis and Characterisation of an Alumina-Supported RuOs3 Cluster Catalyst
j. r. budge, j. p. scott and b. c. gates, J. Chem. Soc., Chem. Commun., 1983, (7), 342–343
Al+[H3RuOs3(CO)12]−/Al2O3 was formed upon heating [H2RuOs3(CO)13] adsorbed on γ -Al2O3 at 373−473K under a H2 + CO atmosphere. The material is catalytically active for ethylene hydrogenation at 340K and for but-1-ene isomerisation at 330K.
Kinetics of the Fischer-Tropsch Synthesis
r. s. dixit and l. l. taviarides, Ind. Eng. Chem., Process Des. Dev., 1983, 22, (1), 1–9
The kinetics of the Fischer-Tropsch synthesis reactions were studied in an internally recycled reactor over a 0.5% Ru/γ -Al2O3 catalyst. Steady-state turnover numbers were obtained for 3:1 and 2:1 H2:CO feed gas at 200−300°C. Intrinsic kinetic data were obtained on surface-impregnated catalysts. A mechanism for the Fischer-Tropsch synthesis was given and several kinetic models were developed. The product selectivity and CO conversion were strongly influenced by temperature.
Physical Effects on Fischer-Tropsch Synthesis over Composite Ru Catalysts
c.-h. yang and j. g. goodwin, Can. J. Chem. Eng., 1983, 61, (2), 213–217
Fischer-Tropsch synthesis was studied over composite catalysts formed by addition of SiO2 to Ru/Al2O3 and Ru/TiO2. The results showed that the presence of excess amounts of SiO2 with the primary Ru catalysts produced significant changes in conversion and product selectivity.
Ruthenium-Based Catalyst for the Gas-Phase Synthesis of Alcohols from CO and H2
m. inoue, t. miyake, t. inui and y. takegami, J. Chem. Soc., Chem. Commun., 1983, (2), 70–72
Hydrogenation of CO with H2 at 86kg/cm2 and 255°C over a Ru, Mo and Na2O catalyst gives a series of straight-chain primary alcohols as essentially the only liquid products. Since the liquid product was uncontaminated by hydrocarbons and other oxygenated products, the refining of the alcoholic products would be much simpler than with the conventional Fischer-Tropsch reaction.
Metal-Support Effects in the Catalytic Hydrogenation of CO over Ruthenium Y-Zeolites: Influence of Zeolite Basicity on Olefin Selectivity
Pd(I) Complexes in Co-ordination Chemistry and Catalysis
o. n. tezhkin and l. g. bruk, Usp. Khim., 1983, 52, (2), 206–243
A review is given of Pd(I) complexes in co-ordination chemistry including formation and physical properties of Pd(I) complexes, their methods of synthesis and reactions, and the role of Pd(I) compounds in stoichiometric and catalytic reactions. (163 Refs.)
Study of Glycolic Ester Formation in Olefin Catalytic Liquid Phase Oxidation. VII. State of the Components in CH3COOH-Dioxane-HNO3-Pd(II) Contact Solutions
m. g. kolkhonskh, v. a. likholobov and iu. i. ermakov, Kinet. Katal., 1983, 24, (2), 347–351
Studies were made of the state of components in contact solution CH3COOH-dioxane-HNO3-Pd(II) during oxidation of ethylene to saturated glycolic ester. Spectrophotometric studies showed that absorption of ethylene by contact solution at the beginning of the reaction resulted in formation of Pd nitrite complexes yielding saturated glycolic esters.
Mechanism of the Reaction of Oxidative Conjunction of Unsaturated Hydrocarbons in the Presence of Palladium (II) Complexes
i. v. kozhevnikov, Usp. Khim., 1983, 52, (2), 244–267
A review is given of data on the mechanism of liquid phase reaction of oxidative conjunction of arenes to diaryls, arenes with olefins to aryl-olefins and olefins to diene-1,3 in the presence of Pd(II) complexes. (161 Refs.)
New Catalysts for Hydrosilylation of Acetylenic Compounds
m. g. voronkov, v. b. pukhnarevich, i. i. tsykhanskaya, n. i. ushakova, yu. l. gaft and i. a. zakharova, Inorg. Chim. Acta, Artic., 1983, 68, 103–105
The regio- and stereo-selectivity in the homogeneous hydrosilylation of acetylene and heptene-1 monosubstituents and carbofunctional ethylene derivatives in the presence of Pd and Pt catalysts of a new type [Pd2(Ph3P)4Cl2]B10Cl10, [Pd2(Ph3P)4Cl2]B12Cl12, [Pt(Ph3P)3Cl]2B10Cl10, etc., have been studied. Unlike H2PtCl6 and other commonly used catalysts, their application for hydrosilylation of acetylenic compounds makes the process regio specific, forming the β -adduct.
Heat Activated Silicone Foam
c. l. lee, g. m. ronk and s. spells, J. Cell. Plast., 1983, 19, (1), 29–33
The production and properties of a Rh catalysed flame resistant silicone foam are compared to those of a Pt catalysed one. RhCl3(Bu2S)3 when used as catalyst produced a foam with a working time of at least 8 hours at room temperature and which foams rapidly upon heating at 100−150°C, – “heat activated foam”. Its flame retardancy is comparable to that of Pt catalysed foams. The “heat activated foam” cures slowly at room temperature to give an elastomeric material after a few days. Foaming at higher temperature and higher catalyst concentration gives a lower density foam. The heat activated foam has a honeycomb-like structure which makes it useful as window coating for a solar heating panel.
Two New Routes to Ethylene Glycol from Synthesis Gas
Chem. Eng. News, 1983, 61, (15), 41–42
Industrial processes for ethylene glycol production using platinum group metal complex catalysts are described. One method, based on the catalytic hydroformylation of formaldehyde to glycolaldehyde and subsequent hydrogenation to ethylene glycol, uses stable Rh catalyst HRh(CO)2 [P(C6H5)3]2 in the presence of excess phosphine ligands.
Clay Intercalation Catalysts Interlayered with Rhodium Phosphine Complexes. Surface Effects on the Hydrogenation and Isomerization of l-Hexene
r. raythatha and t. j. pinnavaia, J. Catal., 1983, 80, (1), 47–55
Clay intercalation catalysts formed by interlayering of Na+-hectorite with Rh phosphine complexes of the type and Rh(NBD)(dppe)+, where NBD = norbornadiene and dppe = 1,2-bis(diphenylphosphino)ethane, were examined as catalyst precursors for the hydrogenation-isomerisation of 1-hexene in methanol. The intercalated catalysts have a much lower tendency to isomerise the substrate to the less reactive internal olefin 2-hexene under homogeneous conditions. The results showed that surface chemical effects can dramatically alter the catalytic properties of metal complexes immobilised in clay interlayers.
Alkane C-H Bond Activation: New Hope for Catalysis Research
j. haggin, Chem. Eng. News, 1983, 61, (7), 9–12
The history and recent advances in alkane C-H bond activation are examined. Catalysts discussed include the diacetone Ir complex with two hydride and two triphenylphosphine ligands used by Bergman. Bergman has also found that there is a preferential attack on primary C-H bonds. Graham’s work using an Ir catalyst, a new hydridoneopentyliridium compound, is discussed. Work on [C5(CH3)5]Rh[P(CH3)3]H2 which selectively activates alkane C-H bonds is examined. Work on heterogeneous catalysis and on arene C-H bond activation with Rh complexes is also considered.
An Osmium Catalyst for the Selective Electrochemical Oxidation of Alcohols
f. c. anson, t. j. collins, s. l. gipson and t. e. krafft, Book of Abstracts, 185th ACS National Meeting, Seattle, Washington, March 20–25, 1983, Abstract No. 240
Addition of alcohols to bis(pyridine) [N, N1-bis(3,5-dichloro-2-hydroxybenzamido)1,2-ethane]Os(IV), (I), in CH3Cl was studied. Controlled oxidation of (I) in the presence of alcohols forms a new Os species which shows catalytic activity for alcohol oxidation. Controlled potential oxidation of 0.5M benzyl alcohol in the presence of 40μ M catalyst produced >40 catalyst turnovers with the selective production of benzaldehyde.
The OsO4-Catalysed Decomposition of Hydrogen Peroxide
l. j. csányi, z. m. galbács and l. nagy, Magy. Kem. Foly, 1983, 89, (3), 131–140
The rate of H2O2 decomposition in the presence of OSO4 as catalyst was proportional to the first power of the OsO4 concentration, and to the power 1−1.2 of the H2O2 concentration. Hydroxyl and superoxide radicals were formed during the decomposition.
Standardised Tethering of Ru3-Ru6 Clusters to High Surface Area Oxides
j. evans and b. p. gracey, J. Chem. Soc., Chem. Commun., 1983 (5), 247–249
Molecularly-specific routes to support Ru clusters have been developed to find the particle size effects on the catalytic activity of materials. Complexes Ru3(CO)11L, H4Ru4(CO)11L, Ru5C(CO)14L and Ru6C(CO)16L [L = PPh2CH2CH2Si(OEt)3] have been isolated and used to tether Ru3−6 units to SiO2, Al2O3 and TiO2 supports in a standard manner.
Ethanol from H2 and CO via Homogeneous Ruthenium Catalysis
b. k. warren and b. d. dombek, J. Catal., 1983, 79, (2), 334–347
Ru carbonyl complexes, obtained from Ru2(CO)12 in the presence of an iodide promoter, an acid and a phosphine oxide, provide an unusually selective system for the direct conversion of CO and H2 to ethanol. Reaction conditions were 30 to 87 MPa and 180 to 250°C. Other products include methanol, methane, acetaldehyde, ethylene glycol and n-propanol.
Composite Catalysts for Carbon Monoxide Resistant Fuel Cell Anodes
a. j. coleman, a. a. adams, j. a. joebstl and l. s. joyce, Extended Abstracts, 83–1, 163rd Spring Meeting of the Electrochem. Soc., San Francisco, May 8–13, 1983, 1262–1263
A comparison is made between a standard Pt-fuel cell anode and a 50/50 wt.% Pt-Ru alloy electrode, and a WC anode and a WC electrode with 0.1 wt.% Pt. The electrolyte was phosphoric acid and the reactants were pure H2 and a 3% CO-H2 mixture. A modest gain in activity occurred for the 0.1% Pt/WC electrode and a sizeable gain for the 1% Pt/WC sample when H2 was the reactant. With CO present the 1% sample lost 96% of its activity, while the 0.1% sample decrease by 26%. A Pt/WC electrode can be made where the WC supports the anode reaction at low temperatures, with the Pt becoming active as temperature and the reaction rate increase. Anode polarisation curves for Pt and Pt-Ru, in the presence of CO, show the advantage of using Pt-Ru especially below 160°C. Pt-Ru and Pt/WC may be alternative anode electrocatalysts for fuel cells, started from low temperatures on reformate fuel.
Hydrogen Absorption and Embrittlement of Tantalum by Cathodic Loading
h. heuberger, a. knodler and ch. j. raub, Metall, 1983, 37, (3), 244–248
The takeup and enbrittlement of Ta by electrolytically produced H2 was investigated on various samples. The oxide surface layers affect the H2 uptake. Surface coatings of varying thicknesses with platinum group metals as alloying constituents were tested as anodic protection for Ta.
ELECTRICAL AND ELECTRONIC ENGINEERING
Precious Metal Inlays for P.C. Connector Contacts
d. maddick, New Electron., 1983, 16, (2), 44, 46, 49
An evaluation of noble metal alloy inlays as replacements for Au electrodeposits is presented. Solderability, high temperature mechanical endurance, effects of rapid change of temperature, mechanical endurance, solvent resistance and costs were examined. Alloys considered were 6Pt-25Ag-69Au, 40Ag-60Pd and 6Ni-94Au of thicknesses 0.5μ m and 0.75 μ m.
An Integrated CO-Sensitive MOS Transistor
d. krey, k. dobos and g. zimmer, Sens. Actuators, 1983, 3, (2), 169–177
MOS transistors with hole-structure Pd gates are detectors for CO. The CO-sensitive transistors, studied at 180°C, showed reproducible sensitivities with measured threshold shifts of 75mV for 0.1 Torr CO pressure. By using a protective Al layer on the Pd gate, a considerable improvement in CO selectivity with respect to H2 was obtained.
The Use of Industrial-Grade Platinum Resistance Thermometers between 77K and 273K
l. m. besley and r. c. kemp, Cryogenics, 1983, 23, (1), 26–28
Measurements made on the stability of seven industrial platinum resistance thermometers when exposed to thermal cycling between 77K and 373K are described. A two point calibration method giving an accuracy of ±35mK for thermometers of this type over the range 70−273K is also described, which is better than that obtainable with IPTS-68.