Platinum Metals Rev., 1985, 29, (3), 131
ABSTRACTS: July 1985
of current literature on the platinum metals and their alloys
Adsorption and Reactions of Acetaldehyde on Pt(S) − [6(111) × (100)]
r. w. mccabe, c. l. dimaggio and r. j. madix, J. Phys. Chem., 1985, 89, (5), 854–861
The adsorption and reactions of CH3CHO with clean and O-predosed Pt(S) − [6(111) × (100)] surfaces were studied by EELS and TPRS to examine the control of pollutants from ethanol-fuelled vehicles. Reaction pathways found were identical on both surfaces. Products formed included gases CO, CH4, H2, and adsorbed CH3CO, H, CH3, CO, C2H3, O and C, depending upon temperature.
The Influence of Preparation Methods of Platinized p-Type Indium Phosphide on Photoelectrochemical Properties
h. yoneyama, h. azuma and h. tamura, J. Electroanal. Chem. Interfacial Electrochem., 1985, 186, (1 and 2), 247–256
Comparative studies of the photoelectrochemical properties of platinised p-type InP were made for different methods of platinisation: electrodeposition under illumination (1), electrodeposition in the dark (2), and arc plasma spraying deposition (3). The highest activities and electrode stabilities for photoassisted H2 evolution occurred at electrodes prepared by (1) and the most inferior properties were observed for method (2). Deposited Pt showed different morphologies depending on the method of platinisation.
Thermodynamic, Elastic and Structural Properties of Solid Solutions of Hydrogen in Pd-Si Metallic Glasses
r. s. finocchiaro, Ph.D. Thesis, Northeastern Univ., 1983, Diss. Abstr. Int. B, 1985, 45, (7), 2174–B
The H solubility and thermodynamics in Pd-Si were studied in the temperature range 10−90°C and H pressures of 0−100torr. Pressure-composition-temperature diagrams were constructed and relative excess partial molar free energies, enthalpies and excess entopies are reported. There is a dramatic dependence of the H solubility on the Si concentration. A decrease in the H solubility is observed when the Si concentration increases from 14 to 22at.%.
Phase Relationship and Thermodynamic Properties of the Pd-S System
j. r. taylor, Metall. Trans., 1985, 16B, (1), 143–148
S pressures in the Pd-S system were measured for liquid mattes, PdS/liquid matte mixtures, Pd/matte, Pd4S/matte and Pd/Pd4S mixtures by various techniques. The phase diagram has been determined from 0−50at.% S and microprobe analysis was used to confirm the identification of equilibrated phases.
Composition and Structure of Fission Product Precipitates in Irradiated Oxide Fuels. Correlation with Phase Studies in the Mo-Ru-Rh-Pd and BaO-UO2-ZrO2-MoO2 Systems
h. kleykamp, j. o. paschoal, r. pejsa and f. thümmler, J. Nucl. Mater., 1985, 130, 426–433
Composition and crystal structure of fusion product precipitates in irradiated oxide fuels were studied by various techniques. Ru, Rh, Pd, Mo and Tc were found to form mono-phase or two-phase alloys in irradiated LWR, HRR and FBR oxide fuels. Metallic phases found were h.c.p. ε -Ru(Mo, Tc, Rh, Pd) solid solutions, b.c.c. β -Mo(Tc/Ru) and f.c.c. α -Pd(Ru, Rh).
Oxygen Potential and the Chemical State of the Fission Products Ruthenium, Rhodium and Palladium in Irradiated Oxide Fuels
m. s. chandrasekharaiah, J. Nucl. Mater., 1985, 130, 366–374
Thermodynamic properties of intermetallic compounds of the type M3U and M3Pu where M = Ru, Rh or Pd are reviewed. The critical oxygen potential of the oxide fuel matrix necessary for their formation is suggested. Phase diagrams for PuM3, UM3 and the formation of the UM3 phase are discussed. The UM3 have rather unusual thermodynamic stability.
Potassium Coadsorption Induced Dissociation of CO on the Rh(III) Crystal Surface: An Isotope Mixing Study
j. e. crowell, w. t. tysoe and g. a. somorjai, J. Phys. Chem., 1985, 89, (9), 1598–1601
The coadsorption of K with CO on Rh(111) induces dramatic changes in the chemisorption properties of CO. Isotopic mixing shows that CO dissociation occurs with coadsorbed K, but does not occur on a K-free Rh(111) surface. The simultaneous desorption of K and CO for the dissociated state indicates that direct interactions are responsible for CO dissociation and that up to 3 CO molecules are dissociated per K atom.
Excited-State Properties of a Triply Ortho-Metalated Iridium(III) Complex
k. a. king, p. j. spellane and r. j. watts, J. Am. Chem. Soc., 1985, 107, (5), 1431–1432
The characterisation of the ground and luminescent excited states of a triply ortho-metallated complex fac-Ir(ppy)3 are reported for the first time. The complex is one of the strongest transition metal photoreductants so far reported. A luminescent lifetime of 5.0μ s was observed in ethanol/methanol glass at 77K, but could be extended to 2.0μ s. The photoactivity in halocarbon solvents suggested that Ir(ppy)3 may be strongly reducing in its excited state.
Oxygen Evolution and Corrosion on Ruthenium-Iridium Alloys
r. kötz and s. stucki, J. Electrochem. Soc., 1985, 132, (1), 103–107
The initial stages of O2 evolution and anodic corrosion on Ru-Ir alloys were investigated in 1N H2SO4 by voltammetry and XPS. The corrosion of Ru was significantly reduced by increasing Ir content; simultaneously the activity for O2 evolution decreases. The reduced corrosion of Ru is paralleled by an increased tendency to oxide formation of the Ir. The stabilisation of Ru by Ir is assigned to the formation of a protective oxide layer with increased Ir.
Crystal Structure of Nonstoichiometric Tetranuclear Platinum Compound, cis-Diammineplatinum α -Pyrrolidone Violet, [Pt4(NH3)8(C4H6NO)4] (PF6)2(NO3)2.56. 5H2O
k. matsumoto, Bull. Chem. Soc. Jpn., 1985, 58, (2), 651–656
The nonstoichiometric Pt tetranuclear title compound, a Pt blue related compound was synthesised and its crystal structure solved by X-ray diffraction analysis. The crystal is triclinic with space group Pī. The cation is structurally identical with those of cis-diammineplatinum α -pyridone yellow, -α -pyridone blue and -α -pyrrolidone tan, and consists of 4 Pt atoms linked in a chain with bridging pyrrolidone ligands. The Pt-Pt bond distances are given, and the average Pt oxidation state is 2.14, therefore indicating that the compound is 44% of [Pt4 (NH3)8(C4 H6NO4]4+ and 56% of [Pt4(NH3)8(C4H6NO)4]5+.
The Platinum Benzoic Acid Blues—A New Class of Blue Platinum Compounds
t. ramstad and j. d. woollins, Transition Met. Chem., 1985, 10, (4), 153–155
The preparation of Pt blues from and benzoic or phthalic acids is described. The compounds were characterised and unlike pyrimidine blues the Pt blues appear not to be ionic.
Unique Structural Features of a Rh6-μ 4-t-BuAs Complex, Formed via As-C Bond Cleavage. Synthesis and Structure of a Rh6 Pentagonal Pyramid: Rh6 (CO)9 (μ -t-Bu2As)2 (μ 4-t-BuAs)
r. a. jones and b. r. whittlesey, J. Am. Chem. Soc., 1985, 107, (4), 1078–1079
The synthesis, characterisation and X-ray crystal structure of the title complex was studied. It is thought to be the first example of a Rh6 cluster where the framework is a pentagonal pyramid. Formation of the complex involves an As-C bond cleavage giving a t-BuAs unit bound to the cluster in a unique bridging manner with one As-Rh bond passing through the Rh5 plane. Other unique features are described.
A Tetrairidium Cluster with a Bridging SO2: The Synthesis, Fluxional Behaviour and Crystal Structure of Ir4(CO)9 (μ 2-CO)2 (μ 2-SO2)
d. braga, r. ros and r. roulet, J. Organomet. Chem., 1985, 286, (1), C8−C12
The reaction of SO2 with Ir4(CO)11(norborn-2-ene) yields the title cluster compound. X-ray diffraction shows that this compound contains a SO2 ligand and two CO groups, all three bridging between the basal metal atoms. The lowest energy CO scrambling process has been determined by 13C NMR studies. The thermal stability and high solubility of this compound, compared to Ir4(CO)12 make it a good starting material for the synthesis of other clusters.
A Simultaneous Voltammetric and UV-Visible Reflectance Spectroscopic Investigation of the Adsorption of Carbon Monoxide on a Platinum Electrode in Aqueous Solution
n. collas, b. beden, j. m. leger and c. lamy, J. Electroanal. Chem. Interfacial Electrochem., 1985, 186, (1 and 2), 287–297
The adsorption of CO on a smooth Pt electrode was studied by in situ u.v.-visible reflectance spectroscopy. Two types of adsorbed CO species were detected, depending on both the electrode potential and the degree of coverage. It is concluded that bridge bonded CO is adsorbed first at low coverage while linearly bonded CO predominates at high.
Electrocatalytic Oxidation of As(III). II. Kinetic Studies at Pt Electrodes
t. d. cabelka, d. s. austin and d. c. johnson, J. Electrochem. Soc., 1985, 132, (2), 359–364
The kinetics of As(III) electrocatalytic oxidation at a Pt rotating disc electrode were studied. PtOH formation was the first step in the production of surface oxides at Pt electrodes. The OH is reversibly adsorbed and can be stabilised by place exchange with surface Pt atoms to give OHPt, and ultimately oxidised further to give PtO. It is concluded that PtOH is the O transfer agent in the oxidation.
On the Electrosorption of Oxygen Species and Adlayer Growth on Noble Metal Surfaces
m. peuckert, J. Electroanal. Chem. Interfacial Electrochem., 1985, 185, (2), 379–391
The surface chemistry of adsorption and surface phase formation on Pt, Rh, Ir and Au single crystal electrodes in 0.5MH2SO4 was studied between 0−4V versus a standard hydrogen electrode by XPS and cyclic voltammetry. Both methods gave complementary results which were interpreted as potential-dependent changes from physisorption of water to adsorption of hydroxyl groups, hydroxide film formation and eventual growth of thick adlayers of oxyhydroxide (Ir, Rh, Au) or hydroxide (Pt). (65 Refs.)
Electrocatalysts on Supports—III. Electrocatalytic and Adsorption Properties of Microdeposits and Thin Films of Platinum Group Metals
v. s. bagotzky and a. m. skundin, Electrochim. Acta, 1985, 30, (4), 485–491
The adsorption and electrocatalytic properties of microdeposits of Rh on Au, Pd on Nb, Ru and Os on Ti and Pd thin films on glass C and Ni have been investigated. H adsorption on Rh and Ru microdeposits is characterised by a low binding energy, and on Pd films by a high binding energy. The cathodic H evolution rate on Ru microdeposits and Pd films on glass C and Ni is lower than those on the corresponding bulk metals.
Photoelectron Spectroscopic Studies of Electrode and Related Surfaces
p. m. a. sherwood, Chem. Soc. Rev., 1985, 14, (1), 1–44
A review of XPS studies of electrode surfaces and related surfaces is presented. XPS gives useful chemical information and is generally less destructive than other surface science methods. Noble metals present less problems over sample transfer than nonnoble surfaces where oxidation may occur. Consideration is given to the structure of the electrode surface, anaerobic transfer, electrochemical cells, non-aqueous electrolyte systems, complex systems with mixed oxidation state oxides and variations with electrolyte concentration, electrochemically prepared surfaces, gas evolution electrodes, and Ru, Pd, Rh, Ir, Pt electrodes. (228 Refs.)
Electrochemical Reduction of Carbon Dioxide to Methane, Methanol, and CO on Ru Electrodes
k. w. frese and s. leach, J. Electrochem. Soc., 1985, 132, (1), 259–260
Electroplated Ru/C and Ru/teflon electrodes were tested for CO2 electrolysis in Na2SO4 or H2SO4 electrolytes. For Ru/C CH4 yield increased with increasing temperature. The CH4 could also be produced in the absence of C, using Ru/teflon electrodes. Small amounts of CH3OH and CO were produced in local open circuit conditions.
Investigation of the Mechanism of Hydrogen Evolution during Photocatalytic Water Decomposition on Metal-Loaded Semiconductor Powders
r. baba, s. nakabayashi, a. fujishima and k. honda, J. Phys. Chem., 1985, 89, (10), 1902–1905
The active sites for photocatalytic H2 evolution have been identified for Pt, Pd, Ru, Ni and Sn metals loaded on TiO2 suspensions by measuring the H isotope effect of the gases produced by water photodecomposition. The mechanism of H evolution is discussed, and the site is assigned mainly to the loaded metal, when the deposited metal is active.
Photocatalytic Systems with Light-Sensitive Coordination Compounds and Possibilities of their Spectroscopic Sensitization—An Overview
h. hennig and d. rehorex, Coord. Chem. Rev., 1985, 61, 1–53
The purpose of this review of photocatalytic reactions of light sensitive co-ordination compounds is to examine areas not extensively reviewed in English. Photoassisted reactions, the application of both photoinduced catalytic and photoassisted reactions mediated by light-sensitive complex compounds, especially photoinduced homogeneous catalysis of olefins and other photocatalytic organic syntheses, photocatalysis and unconventional photographic processes; the storage and conversion of solar energy, and photo polymerisations, are reviewed. Various platinum group metal complexes and their reactions are discussed. (281 Refs.)
Electrochemiluminescence of Osmium Complexes. Spectral, Electrochemical and Mechanistic Studies
h. d. abruÑa, J. Electrochem. Soc., 1985, 132, (4), 842–849
Detailed electrochemical, spectral and electrochemiluminescence (ECL) studies are presented for Os bipyridine and Os phenanthroline complexes. ECL was observed for a large number of complexes, but was less than expected. Surface ECL was observed when the complex is immobilised on the surface of the electrode. There was a good correlation between the observed ECL intensity and the solution luminescence quantum yield.
Photoelectrochemical Oxidation of Halide Ions at Naked, Catalytically Modified, and Polymer-Coated n-CdS Electrodes in Aqueous Media
k. rajeshwar, m. kaneko, a. yamada and r. n. noufi, J. Phys. Chem., 1985, 89, (5), 806–811
Photoanodes made of n-CdS have been stabilised in Cl2- and Br2-containing aqueous media by the use of a catalytically modified polymer coating of RuO2. The RuO2 was the catalyst in a polymer matrix comprising a PS backbone with pendant moieties. Photoanodic corrosion of the n-CdS was suppressed by the coating. Photovoltages of up to 1.61 V were attained for the modified n-CdS/aqueous electrolyte interface comprising the Cl−/Cl2 redox system at ∼85mW/cm2. Implications for storage photoelectrochemical systems are discussed.
Photosensitized Cleavage of Acetylene to Methane
y. degani and i. willner, J. Chem. Soc., Chem. Commun., 1985, (10), 648–650
Photosensitised reductive cleavage of C2H2 to CH4 is accomplished in an aqueous solution that includes [Ru(bpy)3]2+ as sensitiser, triethanolamine as electron donor, and a [RuL5(H2O)]2+ complex that acts as electron acceptor and catalyst in the process.
Photoinduced Excited-State Reactions of Ruthenium(II) Complexes in Multiphase Systems
s. l. buell, Ph.D. Thesis, Univ. of Virginia, 1983, Diss. Abstr. Int. B, 1985, 45, (7), 2171–B
A new heterogeneous photocatalyst utilising [Ru(bpy)3]2+ irreversibly bound to a strongly acidic cation exchange resin is described. The limiting quantum yield for the photosensitised production of 1O2 in methanol is 0.90, and the photooxidation yield for 1O2 scavenging is 77%. Water added to the sensitiser decreases the photooxidation yield, but a water saturated sensitiser gives yields >20%. As a 1O2 generator in methanol the -Ru(bpy) is comparable to homogeneous Rose Bengal and superior to heterogeneous Rose Bengal.
Highly Efficient Sensitization of Titanium Dioxide
j. desilvestro, m. grÄtzel, l. kavan and j. moser, J. Am. Chem. Soc., 1985, 107, (10), 2988–2990
High efficiencies in the sensitisation of colloidal anatase particles and polycrystalline electrodes has been achieved on using tris(2,21-bipyridyl-4,41-dicarboxylate)Ru(II) dichloride as a sensitiser. A 44% incident light to current conversion efficiency was achieved.
Homogeneous Catalysis of the Photoreduction of Water. 6. Mediation by Polypyridine Complexes of Ruthenium(II) and Cobalt(II) in Alkaline Media
c. v. krishnan, b. s. brunschwig, c. creutz and n. sutin, J. Am. Chem. Soc., 1985, 107, (7), 2005–2014
The emission from (polypyridine)Ru(II) complexes is quenched by (polypyridine)Co(II) complexes by parallel oxidative, reductive and energy-transfer pathways. The oxidative route is the basis for a new water photoreduction sequence—in mixed acetonitrile-water solvents relatively high cageescape yields of and are obtained. The Ru(III) complex is reduced by TEOA and the reacts with water and/or TEOAH+ to give H2. The maximum H2 quantum yield obtained is 0.29 in 50% acetonitrile-water.
ELECTRODEPOSITION AND SURFACE COATINGS
On the Nature of Hydrogen in Electrolytic Palladium Precipitates. Optimisation of the Coulometric Methods of Measurement
d. walz, f. friedrich and ch. j. raub, Metalloberflaeche, 1985, 39, (3), 99–103
H2 in the crystal lattice of electrolytic Pd precipitates impairs mechanical properties. From the H2 contents inferences on the state of the electrolyte and working conditions can be drawn. An improved method of determining H2 contents in Pd layers in a relatively short time is described.
LABORATORY APPARATUS AND TECHNIQUE
A New Method of pH Control by Use of a Polypyrrole Coated Electrode
m. okano, a. fujishima and k. honda, J. Electroanal. Chem. Interfacial Electrochem., 1985, 185, (2), 393–396
By means of a polypyrrole coated Pt anode and a Pt counter electrode the pH of an aqueous solution can be changed quickly. A pH change between 4 and 10 was obtained.
Pyroelectric Enthalpimetric Detection
Catalytic Ignition and Heat Release of Fuel/Air Mixtures
p. cho, Ph.D. Thesis, Northwestern Univ., 1984, Diss. Abstr. Int. B, 1985, 45, (7), 2279–B
Ignition and heat release rates of fuel/oxygen/nitrogen over Pt wires were studied by microcalorimetry. Fuels studied were propane, butane, propylene, ethylene, CO and H2. For very low Reynolds number the flow velocity has negligible influence on ignition temperature. Variation in fuel concentration was an important factor as ignition temperatures of propane and butane decrease as the concentrations are increased from lean to rich mixtures, while the opposite trend is observed for propylene, ethylene, CO and H2. The effect of O concentration was also studied. Heat release rate showed H2/air mixture was diffusion limited.
Poisoning of Supported Platinum Catalysts: Deactivation by Carbon Monoxide for Methylcyclopropane Hydrogenolysis
d. e. damiani, Ph.D. Thesis, Northwestern Univ., 1984, Diss. Abstr. Int. B, 1985, 45, (7), 2244–B
The characterisation of a series of Pt/Al2O3 and Pt/TiO2 catalysts by methylcyclopropane hydrogenolysis under different poisoning conditions was investigated, CO being the main poison used. The apparent activation energy for isobutane and n-butane formation slightly increased with increasing poisoning, when CO pulses were injected to the fluidised catalyst bed. Poisoning by partial desorption of preadsorbed CO gave similar results when poisoning was extensive. CO and H2 coadsorption showed that when the poison and H2 compete for adsorption sites, the relative strengths of their adsorptions is important in determining the deactivation rate. A Pt/TiO2 catalyst free of SMSI lost activity faster than similar Pt/Al2O3 or Pt/SiO2 catalysts for comparable levels of poisoning.
Improved H2-D2 Exchange Activity of Pt and Pd by UHV Treatment
s. nishiyama, s.-i. matsuura, h. morita, s. tsuruya and m. masai, Appl. Catal., 1985, 15, (1), 185–195
The activity of polycrystalline Pt and Pd catalysts for the H2-D2 exchange reaction was enhanced by heating them at temperatures higher than 673K at 10−7 Pa for several hours. The enhanced activity is not ascribed to the desorption of contaminates by the UHV and heat treatment, but may be caused by surface rearrangement.
Behavior of Automotive Noble Metal Catalysts in Cycled Feedstreams
h. muraki, h. shinjoh, m. sobukawa, k. yokota and y. fujitani, Ind. Eng. Chem., Prod. Res. Dev., 1985, 24, (1), 43–49
The response of Pt, Pd and Rh catalysts to perturbations in the feedstream stoichiometry were examined in laboratory experiments. NO, CO and hydrocarbon conversions were measured during cycled and steady feeds of equivalent stoichiometry. The activities of Pt and Pd catalysts were improved, particularly for NO, by a cycled feed. The light-off performance also improved during cycled feeding, due to the periodic operation. The order of periodic operation effect was Pt > Pd > Rh. The optimum frequencies for the maximum conversion increased with increasing amplitude and temperature.
Application of High Resolution Analytical Electron Microscopy to the Analysis of Automotive Catalysts
r. k. herz, e. j. shinovskis, a. datye and j. schwank, Ind. Eng. Chem., Prod. Res. Dev., 1985, 24, (1), 6–10
An automobile oxidation catalyst, which had been taken from an automobile driven for 34,800km of normal use was analysed by electron microscopy and compared to a fresh catalyst. It was found that there was no loss of Pt and Pd and no change in the Al2O3 support. Poison concentrations were too low to explain a loss in CO oxidation activity. Metal particles in the aged sample were 20−30nm in diameter, compared to 1−2nm in diameter for the fresh sample, this showing that sintering and loss of metal surface area were primarily responsible for the decreased CO conversion.
Periodic Operation Effects on Carbon Monoxide Oxidation over Noble Metal Catalysts
h. muraki, h. sobukawa and y. fujitani, Nippon Kagaku Kaishi, 1985, (2), 176–181
The periodic effects of the CO-O2 reaction over Pt, Pd, Rh, Ru and Ir catalysts, supported on α -Al2O3 were examined. The period of the feed composition was varied from 0.1−20 s. The average reaction rate was significantly increased by injecting CO and O2 periodically and alternately to the reactor, compared to the steady state position. The optimum period for the maximum CO conversion increased in order Rh < Pd = Ru < Pt < Ir and with a decrease in temperature and stoichiometric 2[O2]: [CO] ratio.
Hydrogenation of Buta-1,3-diene on Supported Metal Catalysts in Aqueous Solution. Part 1.—Differences in the Catalytic Action of Al2O3-Supported Pt, Pd, Rh and Ru Catalysts
k. shimazu and h. kita, J. Chem. Soc., Farraday Trans. I, 1985, 81, (1), 175–183
The catalytic action during the deuteration of buta-1,3-diene on Pt, Pd, Rh and Ru catalysts, supported on Al2O3 in 0.5 mol/dm3 D2SO4 has been examined. Results are discussed in terms of two steps, namely the formation of the half-hydrogenated species and the ionisation of adsorbed H. The rate for the former step is Pd > Pt ≫ Rh > Ru and for the latter step the rate is in the order Pt ≫ Pd > Rh > Ru.
Effect of Titania on the Chemisorption and Reaction Properties of Pt
r. a. demmin, c. s. ko and r. j. gorte, J. Phys. Chem., 1985, 89, (7), 1151–1154
The unusual adsorption and reaction properties observed on Pt/TiO2 catalysts for CO and H2 chemisorption, and reactions have been reproduced on a Pt foil with a TiO2 overlayer. The TiO2 prevents adsorption of CO and H2 but does not prevent the Pt from catalysing the methanation. The methanation may be structure sensitive on Pt and this sensitivity may explain the different reactivities obtained on catalysts with different supports.
Transition Metals in Organic Synthesis: Hydroformylation, Reduction and Oxidation, Annual Survey Covering the Year 1983
l. markÓ, J. Organomet. Chem., 1985, 283, (1–3), 221–337
A survey for 1983 covering hydroformylation, using Pt and Rh catalysts, heterogeneous catalyst systems of supported complexes; the water gas shift reaction, reductions with CO + H2O; hydrogenations and reductions, with Pt, Pd, Rh, Ir, Ru and Os catalysts being used; diene and alkyne hydrogenation with Pt, Pd, Ir and Rh catalysts; hydrogen transfer reactions, reductions with molecular H2 and oxidations, are reviewed. (521 Refs.)
Initial Changes of the Catalytic Properties of Platinum Containing Catalysts. II. Selectivity Changes of Mono- and Bimetallic Pt/Al2O3 Catalysts
z. paÁl, m. dobrovolszky, j. vÖlter and g. lietz, Appl. Catal., 1985, 14, (1–3), 33–46
Profound changes have been observed in the product composition of n-hexane transformations over Pt, Pt-Sn and Pt-Pb supported on Al2O3 during the initial period of the catalyst lifetime. The number of fragments per hexane molecule decomposed decreased with decreasing cracking activity over each catalyst. Isomerisation selectivity increased over bimetallics after the first few pulses, which was partly due to acid isomerisation over Pt-Pb/Al2O3. Addition of Sn increases aromatisation and decreases cracking.
Effects of Oil Phosphorus on Deactivation of Monolithic Three-Way Catalysts
w. b. williamson, j. perry, h. s. gandhi and j. l. bomback, Appl. Catal., 1985, 15, (2), 277–292
The deactivation of Pt-Rh monolithic automotive three-way catalysts by P and Zn from engine oil-derived contaminants has been investigated. The combustion of isooctane containing a ten-fold excess of Zn dialkyldithiophosphate (ZDP) oil additive decreased 3-way conversions substantially when compared to normal oil consumption levels. The combustion of isooctane containing Zn-free cresyl diphenyl (CDP) phosphate gave greater P-retention on the catalyst than for ZDP-containing fuel, but CDP was much less detrimental to three-way activity than ZDP. P was less of a poison than Pb for three-way catalysis. Mechanisms are discussed.
Hydrogenation of Alkenes and Alkynes Catalyzed by Polymer-Bound Palladium(II) Complexes
s. d. nayak, v. mahadevan and m. srinivasan, J. Catal., 1985, 92, (2), 327–339
A polymer-supported Pd(II) species was prepared by oxidative addition between Pd(PPh3)4 and chloromethylated crosslinked PS. This catalyst was used for the hydrogenation of alkenes and alkynes under mild conditions. Quantitative data on hydrogenation rates, recycling efficiency of the catalyst and solvent effects on the reaction are presented.
An Infrared Study of the Hydrogenation of Carbon Dioxide on Supported Rhodium Catalysts
m. a. henderson and s. d. worley, J. Phys. Chem., 1985, 89, (8), 1417–1423
An i.r. study of the methanation of CO2 on supported Rh catalysts was performed. Turnover frequencies are in the order TiO2 > Al2O3 > SiO2. CH4 was the only hydrocarbon product observed. CO2 hydrogenation turnover frequencies are larger than those for CO under similar reaction conditions. A key surface intermediate during methanation is a carbonyl hydride species which can be produced in the absence of H2 by migration of H from the support to Rh. The CO2 dissociation was enhanced by the presence of H2 and impurity B.
Decomposition of Formic Acid on Supported Rh Catalysts
f. solymosi and a. erdÖhelyi, J. Catal., 1985, 91, (2), 327–337
The decomposition of HCOOH was studied on supported Rh catalysts in a flow reactor at 380–520K. The dominant process in the decomposition was dehydrogenation which followed first-order kinetics. The activity of the catalysts, based on turnover frequencies decreased in the order TiO2 > Al2O3 > MgO ≍ SiO2 of their supports. CO in the gas stream inhibited the reaction. Weakly held HCOOH, adsorbed CO and formate species were on the surface during the reaction. (46 Refs.)
Reduction of NO by H2 over Silicon-Supported Rhodium: Infrared and Kinetic Studies
w. c. hecker and a. t. bell, J. Catal., 1985, 92, (2), 247–259
The kinetics of NO reduction by H2 were investigated over a Rh/SiO2 catalyst. Catalyst pre-treatment determined specific activity and product selectivity. Pre-oxidation in NO increases the NO reduction activity to 50% over that observed when the catalyst is prereduced. Pre-oxidised catalyst favours N2 formation. At NO conversion levels below 60% the surface is saturated by adsorbed NO.
Methane Synthesis in the H2O + CO Reaction over Titania-Supported Rh and Rh-Pt Catalysts
f. solymosi, a. erdÖhelyi and i. tombÁcz, Appl. Catal., 1985, 14, (1–3), 65–67
Rh/TiO2 was found to be a very active catalyst for CH4 formation in the H2O + CO reaction and its catalytic activity was enhanced by a factor of 5 by the presence of Pt.
Selective Reduction of Various Functional Groups and Carbonylation of Olefins Using CO and H2O in the Presence of Rhodium Cluster Catalysts
k. kaneda, m. kobayashi, t. imanaka and s. teranishi, Nippon Kagaku Kaishi, 1985, (3), 494–502
The water gas shift reaction and its application to the reduction of various functional groups and to the carbonylation of olefins were studied using Rh carbonyl complex amine (or pyridine) systems. At 700 mm Hg for the CO pressure and 100°C Rh6(CO)16-ethylenediamine has high catalytic activity for the water gas shift reaction. Heterogenisation of Rh6(CO)16 on diaminated PS increases its catalytic activity.
Selective Hydrogenation of α,β -Unsaturated Carbonyl Compounds and Nitriles Catalyzed by Polymer-Supported Rhodium Carbonyl Complexes
t. kitamura and t. joh, Nippon Kagaku Kaishi, 1985, (3), 473–478
The hydrogenation of α,β -unsaturated carbonyl compounds and nitriles with CO and water was investigated using Rh carbonyl clusters on resin beads. Amberlite IRA-93 and Amberlyst A-21 beads were the best. Hydrogenation proceeded in a dioxane:hexane ratio of 3 : 7. Rh species partially migrated during the reaction from the resin beads to the solution in THF.C = C and α,β -unsaturated carbonyl compounds and nitriles were selectivity hydrogenated. Simple aldehydes were hydrogenated to alcohols. These resin-supported catalysts were stable under N2 or CO atmospheres and could be reused without loss of catalytic activity. The hydrogenation rates with resin-supported catalysts were greater than those with the homogeneous.
Structure and Reactivity of Aromatic Polymers/Ruthenium Catalysts
f. ciardelli and p. pertici, Z. Naturforsch. B, 1985, 40, (2), 133–140
Ru/PS systems have been examined by EXAFS, TEM and i.r. and Raman spectroscopies. A structure based on small metal clusters bound to the polymer by a single Ru-arene binding is proposed. The validity of this approach was confirmed by making a similar product from poly-1-vinylnaphthalene in place of PS. Both systems were active for hydrogenation of a large variety of unsaturated groups such as olefinic double bonds, mononuclear aromatic hydrocarbons, ketones, nitriles, nitroaromatics and oximes. Catalytic activity, chemio- and stereoselectivities are discussed in terms of the proposed structure.
Carbon-Supported Fe-Ru Catalysts Prepared from Stoichiometric Mixed-Metal Carbonyl Clusters
m. kaminsky, k. j. yoon, g. l. geoffroy and m. a. vannice, J. Catal., 1985, 91, (2), 338–351
Highly dispersed Fe-Ru bimetallic crystallites were obtained on an amorphous C black using mixed-metal carbonyl precursors. The catalysts were characterised by chemisorption of CO and H2 at 195 and 300K, and their kinetic properties in the CO hydrogenation reaction were determined. The presence of Ru helped reduction of the Fe and activated the clusters at 473K. Surface enrichment in Fe occurred in the small crystallites after reduction. Turnover frequencies for CH4 and total hydrocarbon formation increased in parallel with the increase in surface Ru concentration, but turnover frequency for CO2 smoothly decreased. Scanning transmission electron microscope micrographs showed a raft-like structure for the metal crystallites in the small pore structure of the C, which may be responsible for differences in catalytic behaviour between C and other supports. (45 Refs.)
Palladium-Catalyzed Carbonylation of Organic Halides with Terminal Acetylenes in the Presence of Amines—Novel Acetylenic Ketone Synthesis
m. tanaka, t. kobayashi and t. sakakura, Nippon Kagaku Kaishi, 1985, (3), 537–546
Organic halides were carbonylated with terminal acetylenes by Pd complexes in the presence of bases at 20 atm of CO and 120°C to give acetylenic ketones. Phosphine basicity, methylene chain length or framework between the two phosphine groups profoundly affected the reactivity. Arsines accelerated the insertion of CO compared to phosphines. Using strong bases such as triethylamine and tripropylamine was essential for high yield synthesis of 1,3-diphenyl-2-propyn-1-one. This new reaction could be applicable to a variety of aromatic heteroaromatic and vinylic halides combined with terminal acetylenes. (56 Refs.)
Palladium Chloride and Polyethylene Glycol Promoted Oxidation of Terminal and Internal Olefins
h. alper, k. januszkiewicz and d. j. h. smith, Tetrahedron Lett., 1985, 26, (19), 2263–2264
Both terminal and internal olefins can be efficiently converted to ketones in polyethylene glycol and water using Pd chloride as catalyst.
Palladium Catalysed Reaction of Butadiene Monoxide with Carbon Dioxide
t. fujinami, t. suzuki, m. kamiya, s.-j. fukuzawa and s. sakai, Chem. Lett. (Jpn.), 1985, (2), 199–200
CO2 readily reacts under mild conditions with 1,3-butadiene monoxide in the presence of a catalytic amount of tetrakis(triphenylphosphine)-Pd under ordinary pressure at 0°C to give vinylethylene carbonate in quantitative yield.
Incorporation of a Recyclable Surface-Active Electron Donor in Synthetic Vesicles. Application to Photosensitized Hydrogen Formation by Vesicle-Stabilized Rh-Coated Colloidal CdS Particles
r. rafaeloff, y.-m. tricot, f. nome, p. tundo and j. h. fendler, J. Phys. Chem., 1985, 89, (7), 1236–1238
Colloidal Rh-coated CdS particles were in situ generated in thiol-functionalised surfactant/dioctadecyldimethylammonium chloride (DODAC) mixed vesicles. Under u.v. irradiation the surfactant acted as a recyclable electron donor and promoted H generation. This vesicle-integrated electron donor could be chemically regenerated to resume H production at the same rate as during its first oxidation. This is a new concept in surfactant stabilised colloidal semiconductor system and makes a cyclic process of H generation possible.
Alkylation of Benzene with α -Diazoketones via Cycloheptatrienyl Intermediates
m. a. mckervey, d. n. russell and m. f. twohig, J. Chem. Soc., Chem. Commun., 1985, (8), 491–492
The combination of Rh(II)trifluoroacetate and trifluoroacetic acid catalysts was found to provide an efficient means of benzene alkylation and produced a range of alkyl and aryl benzyl ketones in excellent yields in one operation. The catalysts were used sequentially.
Ruthenium-Catalysed Oxidation of Secondary Amines to Imines Using t-Butyl Hydroperoxide
s.-i. murahashi, t. naota and h. taki, J. Chem. Soc., Chem. Commun., 1985, (9), 613–614
The oxidation of secondary amines by Ru(II) complexes, such as RuCl2(PPh3)3 and t-butyl hydroperoxide in benzene as oxidant under mild conditions, gave corresponding imines in high yields.
The Selective Homogeneous Hydrogenation of Alkynes in the Presence of Alkenes Catalyzed by [RuH(PMe2Ph)5]PF6
m. o. albers, e. singleton and m. m. viney, J. Mol. Catal., 1985, 30, (1–2), 213–217
The homogeneous hydrogenation of alkynes with cationic Ru(II) complexes [RuHL5]PF6 (L = PMe2Ph, P(OMe)2Ph, PMe2(C6H4OMe-o), AsMe3) as catalysts in which the title complex selectively reduces internal and terminal alkynes without hydrogenating the corresponding olefin is reported. This complex is a precursor to the most efficient catalyst known to date for the selective hydrogenation of alkynes. The catalyst shows negligible tendency to isomerise or hydrogenate olefinic substrates.
Ruthenium-Catalyzed Oxidation of Alcohols with Sodium Bromate
Catalytic Etching of Platinum during Ethylene Oxidation
n. l. wu and j. phillips, J. Phys. Chem., 1985, 89, (4), 591–600
Catalytic etching of Pt foils during ethylene oxidation was studied by SEM and TEM. The etching was a strong function of surface temperature and C2H4 : O2 ratio in the gas phase. A novel model was developed to explain all the regions of the phase diagram, and showed five regions on the plane defined by surface temperature and O2 : C2H4 ratio and three types of catalytic etching. The etching was attributed to formation of methylene radicals above ∼770K in the boundary layer over the catalyst.
Semiconductor Chip with Platinum Thin Film Resistor for Temperature Sensing
Res. Discl., 1985, (251), 141
A Pt resistor is formed on a semiconductor chip and is connected as a temperature sensitive resistor in a temperature measuring circuit. The resistor is a thin film and is ∼100μ m long, 0.5μ m wide and a few Ås thick. It can be formed by ion beam sputtering, patterned by photoresist techniques and etched by ion beam milling. The TCR is very reproducible. The Pt resistor can operate at high temperatures and resists oxidation.
Interpolation Procedures for Ceramic-Encapsulated Rhodium-Iron Alloy Resistance Thermometers in the Temperature Range 77 to 273K
l. m. besley, J. Phys. E, 1985, 18, (3), 201–205
The thermometric characteristics of six ceramic-encapsulated Rh-Fe alloy resistance thermometers were studied between 32 and 273.15K. Data are given for the resistance-temperature relationship and the self-heating. Interpolation means were investigated for the range 77−273.15K. An eleven-term polynomial fitted to many points gives a precision of ±0.5mK over this range.
Circadian Timing of Cancer Chemotherapy
w.j.m. hrushesky, Science, 1985, 228, (4695), 73–75
Circadian timing of adriamycin and cis-platin was found to influence toxicity substantially. Administering adriamycin in the morning and cis-platin in the evening caused fewer complications, dose reductions and treatment delays than administering adriamycin in the evening and cis-platin in the morning, in a study of 31 patients with advanced ovarian cancer.