ABSTRACTS: April 1974
ABSTRACTS: April 1974
of current literature on the platinum metals and their alloys
The Mechanism of Crystallographic Ordering in CuPt
r. s. irani and r. w. cahn, J. Mater. Sci., 1973, 8, (10), 1453–1472
Studies of the ordering of the Cu-Pt system near to the Cu-Pt composition showed that Pt-rich off-stoichiometric alloys contain a wide two-phase region of order and disordered platelets. Two types of diffraction sequence were observed in isothermally ordered stoichiometric alloys. Those annealed at 620°C <T< 815°C showed a series of broad, asymmetric X-ray line profiles during the early part of the ordering cycle, representing a “continuous” reaction but those annealed below 620°C showed evidence of coexistence of both ordered and disordered phases, representing a “discontinuous” reaction. A nucleation-and-growth model is proposed for CuPt at all ordering temperatures. Microscopic studies indicated a lamellar structure above 620°C but a grain-boundary reaction, generating very coarse domains, below it. Samples annealed below 475°C had ordered spherulites grow within the grains. Samples cooled slowly through Tc=815°C order by a diffusion-controlled shear process.
Investigations on the Systems of Platinum and of Rhenium with Mercury
g. jangg and t. dÖrtbudak, Z. Metallkunde, 1973, 64, (10), 715–719
Partial pressure studies on Pt amalgams confirmed the existence of PtHg4, PtHg2 and PtHg4 PtHg2 and PtHg2 are stable at 200−500°C. PtHg decomposes eutectoidally at 250°C into PtHg2 and Hg-saturated Pt. All three phases have at most very narrow regions of homogeneity. Their thermodynamic data could be derived from vapour pressure measurements. Solubility studies showed that Os, Ir, Ru, and Re, which form no compounds with Hg, are only very slightly soluble in it; Rh is slightly more soluble in it (6×10−5 wt.% at 500°C) and does form compounds with Hg; Pt and Pd form compounds with Hg and their solubilities in it at 300°C are 8×10−4 and 0.2 wt.% respectively.
Crystal Growth and Characterisation of PtP2
a. baghdadi, a. finley, p. russo, r. j. arnott, and a. wold, J. Less-common Metals, 1974, 34, (1), 31–38
PtP2 crystals grown from a Sn flux were shown to be of good quality by magnetic, density and crystallographic measurements. The crystals were diamagnetic, with susceptibility −64×10−6 e.m.u./mole and P—P bond distance 2.22Å.
Pressure against Composition Isotherms and Thermodynamic Data for the α-Phase of the Palladium/Hydrogen System
r. burch and n. b. francis, J. Chem. Soc., Faraday Trans. I, 1973, 69, (11), 1978–1982
Pressure/composition isotherms were determined for the α-phase of the Pd/H system at 372–724K by direct equilibration with gaseous H2. The partial molar enthalpy and partial molar entropy of solution of H in Pd were derived as a function of composition, the values at 600K being respectively −15.56kJ/mol. H2 and −96.5J/°K/mol.H2.
Diffusion of Hydrogen in Rhodium-Palladium Alloys
d. artman and t. b. flanagan, J. Phys. Chem., 1973, 73, (23), 2804–2807
Diffusion constants were determined for interstitial H2 in a series of random f.c.c. Rh-Pd alloys and the diffusion parameters were determined at small H2 contents.
Diffusion Investigations in the System Palladium-Titanium by Means of Electron Probe Micronanalysis
p. lamparter, t. krabichler and s. steeb, Z. Metallkunde, 1973, 64, (10), 720–724
Electron probe studies of diffusion processes at 600−1000°C in the Pd-Ti system showed d(Ti) and β(Ti) solid solubility and the phases TiPd, TiPd2, Ti2Pd3, and TiPd3. Thickness d of single phases grows as d ∼√t. Interdiffusion coefficients were obtained by Matano’s method and their temperature dependence led to determination of their activation energy.
Comprehensive Plastic Deformation of a Bulk Metallic Glass
c. a. pampillo and h. s. chen, Mater. Sci. Engng., 1974, 13, (2), 181–188
Compressive plastic deformation experiments at 77−520K were made on a bulk Pd0·775Cu0·06Si0·165 glass. At 100−500K the ratio of the stress to the elastic modulus is ∼1/60, independent of temperature.
Physicochemical Properties of Metallic Melts Based on Palladium
n. a. vatolin and e. l. dubinin, Fiz.-Khim. Osn. Met. Protsessov, 1973, 266–278
Activities, heats of mixing, vapour pressures, viscosities, electrical resistances, magnetic susceptibilities, density, and surface tensions were determined and discussed for the Pd-Ni, Pd-Co, Pd-Cu, Pd-Ag, Pd-Fe, Pd-Cr, Pd-Mn, Pd-Sb, Pd-Pb, Pd-Al, Pd-Si, and Pd-W systems.
The Crystal Structure and Lattice Constants of RE3Pd4, Y3Pd4 and Th3Pd4 Compounds
a. palenzona and a. iandelli, J. Less-common Metals, 1974, 34, (1), 121–124
Alloys of the rare earths, Y, Th, Hf, and U with Pd of the M3Pd4 composition were studied. With the exception of Eu, V and Hf, single phases were formed, crystallising with Pu3Pd4-type structure. The stability was restricted for radius ratio (Rm/RPd) to 1.20 and 1.37.
Upper Critical Fields and Critical Currents of Superconducting Zirconium-Rhodium Alloys
k. togano and k. tachigawa, J. Less-common Metals, 1973, 33, (2), 275–282
Tetragonal Zr2Rh has a high superconducting transition temperature but contains no Group Va element. Studies of 3, 14 and 33 at.% Rh-Zr alloys showed that 33 at.% Rh-Zr consists of Zr2Rh columnar crystals with  simple fibre texture and substructures. The superconducting critical field Hc2 of Zr2 Rh is as high as 80 kOe at 4.2K, despite its relatively low normal state resistivity, and has crystallographic anisotropy, i.e. Hc2 is higher perpendicular to the columnar axis. Critical current density Jc of 14 and 33 at.% Rh-Zr is related to the metallographic structures.
Reflectance and Optical Constants of Evaporated Ruthenium in the Vacuum Ultraviolet from 300 to 2,000Å
j. t. cox, g. hass, j. b. ramsay and w. r. hunter, J. Opt. Soc. Am., 1973, 63, (10), 1281, abstr.
Studies of Ru films at 300−2000Å showed that variation of deposition from 1 to 80Å/s by electron bombardment on the glass and quartz substrates had little effect on their reflectance. Reflectance loss during extended exposure to air was small, i.e. oxide film formation is low. Films made on substrates at 300°C had slightly higher reflectance than those made at 40°C. Interference effects made 150−200Å semitransparent films have higher reflectance than opaque films ∼584Å thick. Near 2000Å films 300Å thick had highest reflectance. Ru films under optimum conditions had 26% reflectance at λ=584Å.
Effect of Zirconium on Conversions in the System Niobium-Ruthenium
a. l. tatarkina, v. i. gryzunov, g. n. ronami, m. v. raevskaya, i. g. sokolova and e. m. sokolovskaya, Vest. Moskov. Univ., Ser. II, Khim., 1973, (6), 673–678
Diffusion layer studies at 1000−1700°C on Nb-Ru alloys and physico-chemical studies on 10% Zr-Nb-R.u alloys at 1050 and 1600°C are reported.
Intermetallic Compounds in the Ruthenium-Magnesium System
l. westin and l.-e. edshammar, Chem. Scripta, 1973, 3, (1), 15–22
Phase analysis studies on Mg-rich Ru-Mg alloys show the existence of two cubic phases with homogeneity ranges of RuMg1·25−2·25 and RuMg6·2−6·6, the former being of the β-Mn type with a≃6.93Å, while RuMg6·2 has a partly disordered structure of the Rh7Mg44 type with a≃20.2Å.
Gaseous Platinum Chloride
u. wosiewitz and h. schäfer, J. Less-common Metals, 1973, 32, (3), 389–390
The formation of the gaseous Pt6Cl12 molecules from Rh-Pt alloys and Cl2-N2 mixtures was studied at various temperatures and pressures.
Identification of a Mixed-valence Triclinic Product Formed by the Partial Bromination of K2Pt(CN)4
n. j. minot, j. h. perlstein and t. j. kistenmacher, Solid State Commun., 1973, 13, (9), 1319–1323
X-ray diffraction and chemical analysis studies showed that the partial bromination of K2Pt(CN)4 results in at least 2 structurally and stiochio-metrically different products. Triclinic crystals with Pt-Pt spacing 2.95Å grow from acid aqueous solution and tetragonal phases with Pt-Pt spacing 2.88Å grow from basic solutions.
Interactions between Polynucleotides and Platinum(II) Complexes
s. wherland, e. deutsch, j. eliason and p. b. sigler, Biochem. Biophys. Res. Commun., 1973, 54, (2), 662–668
Reaction of either cis - or trans -Pt(NH3)2Cl2 with poly-adenylic acid in dilute aqueous solution leads to quantitative precipitation of the polymer > 0.5. At <0.5, intramolecular binding of one Pt to two bases is favoured; at higher Pt:nucleotide ratios, intermolecular cross linking is important and precipitation results. The absence of isomer selectivity in precipitation suggests that biological specificity of the cis -isomer results from a process other than cross-linking of polynucleotide strands.
Crystal Structure of
k. leary, d. h. templeton, a. zalkin, and n. bartlett, Inorg. Chem., 1973, 12, (18), 1726–1730
Structure studies showed that unit cell is orthorhombic with a=9.346Å b=12.786Å, c=9.937Å, V=1122.9Å3, Z=4, and dc=3.91 g/cm3.
Crystal Structures of [XeF+][RuF6−] and
n. bartlett, m. gennis, d. d. gibler, b. k. morrell and a. zalkin, Inorg. Chem., 1973, 12, (8), 1717–1721
Structure studies showed that XeRuF7 is monoclinic with a=7.991Å, b=11.086Å, c=7.250Å, β=90.68, V=642.2Å3, Z=4, and dc=3.78g/cm3. XeRuF11, however, is orthorhombic with a=16.771Å, b=8.206Å, c=5.617Å, V=773.03Å3, Z=4, and dc=3.79g/cm3.
The Electro-oxidation of Acetylene on Heterogeneous Au-Pt Alloys
j. w. johnson, c. k. wu and w. j. james, J. Electrochem. Soc., 1973, 120, (12), 1676–1681
The anodic oxidation of C2H2 was studied in aqueous solutions at pH 0.3–12.6 at 80°C on heterogeneous Au-Pt alloy electrodes. Results are interpreted in terms of parallel reactions occurring separately on the Au-rich and Pt-rich phases. The polarisation behaviour on the separate phases is like that of the corresponding pure metals.
Adsorption Properties of Skeleton Rhodium-Titanium Electrode-catalysts in Relation to Hydrogen in Sulphuric Acid Solutions
g. s. manankova, g. a. martinyuk and g. p. khomchenko, Zh. Fiz. Khim., 1973, 47, (12), 3085–3087
Studies of 5, 10, 25, and 40 wt.% Ti-Rh electrode catalysts showed that the adsorption of H2 decreases with increasing Ti content until 40% Ti-Rh, when H2 adsorption increases again. X-ray studies showed that the main phase is a Rh-based solid solution.
ELECTRODEPOSITION AND SURFACE COATINGS
A Study of Contamination on Electroplated Gold, Copper, Platinum, and Palladium
d. l. malm and m. j. vasile, J. Electrochem. Soc., 1973, 120, (11), 1484–1487
Examination of electroplated Au, Cu, Pd and Pt for surface and bulk impurities indicates that electroplated metals have more surface contamination than cast metals after identical cleaning procedures. Methods of removing surface impurities are discussed, whilst bulk impurities are generally indicative of plating bath contamination.
Reliability in Printed Circuitry Metallisation—A Case for Improved Catalysing Systems
n. feldstein, Plating, 1973, 60, (6), 611–616
The new approach by which complete metallic coverage of organic substrates incorporates aged SnCl2 solutions with sensitisation by acidic SnCl2 and activation by acidic PdCl2, then catalysis with colloidal PdCl2 in excess acidic SnCl2.
The Nucleation with SnCl2-PdCl2 Solutions of Glass before Electroless Plating
g. h. de minjer and p. f. j. van der boom, J. Electrochem. Soc., 1973, 120, (12), 1644–1650
Metallic Pd nuclei are formed by the nucleation of nonconducting substrates with SnCl2-PdCl2. However, results of experiments on glass using radioactive tracers and ellipsometry showed that no metallic Pd was present after the nucleation.
LABORATORY APPARATUS AND TECHNIQUE
Catalytic Properties of Platinum/Alumina Catalysts Promoted by Rare Earth Elements
n. s. kozlov, g. m. sen'kov, v. a. polikarpov, v. v. shipikin and a. m. davidovskaya, Neftekhimiya, 1973, 13, (5), 643–649
Promotion of Pt/Al2O3 by Y increases the catalytic activity for dehydrogenation of cyclohexane. 0.1 wt.% of promoter has the greatest effect. During conversion of n -octane on the promoted catalyst the aromatics content remains unchanged, but increasing the amount of promoter above 0.1 wt.% depresses the cyclisation capacity of the catalyst. Y improves thermal stability of Pt/Al2O3.
X-ray Structural Investigation of Platinum/Alumina Catalysts
n. s. kozlov, m. ya. lazarev, l. ya. mostovaya and i. p. stremok, Kinet. Kataliz, 1973, 14, (5), 1287–1291
Al2O3 and 0.1−3.0 wt.% Pt/Al2O3 catalysts studied at 600−1200°C exhibit the existence of three modifications of Al2O3: γ, θ and α, which are stable over different ranges of temperature. Pt catalyses the conversion of one modification to another.
Investigation of the State of Platinum in Platinum/Alumina Catalysts for Dehydrocyclisation
n. s. kozlov, e. f. ivan'kovich, a. f. volkodatov and g. a. zhizhenko, Kinet. Kataliz, 1973, 14, (6), 1550–1555
Electron microscope studies of Pt/Al2O3 with no Cl2 but with alkali (K, Cs) and alkaline earth (Ca, Ba) promoters enabled comparisons to be made of Pt crystallite distribution by size and diameter against activity for dehydrocyclisation of n -C6H12. The most active catalysts for this reaction are Pt crystallites of size 40–80Å.
Effect of Media on the Intensity of Sintering of Platinum Catalysts
kh. shpindler, i. d. ratner and l. m. kefeli, Kinet. Kataliz, 1973, 14, (6), 1588–1591
Electron microscope and H2 adsorption studies of the effect of temperature and the nature of the atmosphere (air, He, vacuum) on the dispersion of Pt in Pt/Al2O3 showed that calcining of the catalyst in air causes a decrease in dispersion by increasing the size of the metal particles.
Investigation of Coke Formation during the Aromatisation of Olefins in the Presence of Platinum/Alumina Catalysts
t. v. kurchatkina and yu. v. fomichev, Neftekhimiya, 1973, 13, (5), 665–668
Studies of coke formation on Pt/Al2O3 during aromatisation of aliphatic olefins show that more coke forms from n -C6H12-1 than from n -C7H14-1. Coke formation, determined by catalyst weight increases, rises in the order n -C6H12-1 < methylcyclopentane < cyclohexene < methylcyclopentene. Coke yields on Pt/Al2O3 are higher than on halided Al2O3. Less C6H6 is produced from C6 olefins than from C6 paraffins because the rate of deactivation of the catalyst by coke is greater.
Effect of Oxygen and Water on the Direction of C6-Dehydrocyclisation of N -Octane
a. m. gyul'maliev, e. a. udal'tsova, i. i. levitskii, i. v. stankevich and kh. m. minachev, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1973, (10), 2252–2256
Tests at 450°C, 5 and 20 atm showed that O2 and H2O alter the C6-dehydrocyclisation of n -octane over 0.3% Pt/Al2O3 in the direction of greater ethylbenzene formation. The electron behaviour during this reaction was investigated. The direction of the reaction depends on the number of electron donors in the Pt after absorption of H2O by the catalyst, and on the electron distribution in n -octane molecules.
Kinetic Study of Carbon Monoxide and Propylene Oxidation on Platinum Catalysts
s. e. voltz, c. r. morgan, d. liederman and s. m. jacob, Ind. Engng. Chem., Prod. Res. Dev., 1973, 12, (4), 294–301
The kinetics of CO and C3H6 oxidation on a Pt/Al2O3 catalyst at 400−700°F were studied. Oxidation rate increases with O2-concentration but is inhibited by CO, C3H6 and NO. Results obtained are directly relevant to Pt catalytic converters in automobile exhaust emission control systems.
Mechanism and Poisoning of the Molecular Redistribution Reaction of Alkanes with a Dual-functional Catalyst System
r. l. burnett and t. r. hughes, J. Catalysis, 1973, 31, (1), 55–64
Alkane disproportionation over Pt/Al2O3 mixed with WO/SiO2 involves formation of low concentrations of olefin intermediates over the former followed by their disproportionation over the latter. The overall process is better termed molecular redistribution. Straight chain alkanes are more reactive than branched with pure isobutane only slightly reactive. This catalyst system is very sensitive to poisoning by impurities and it must be protected by a suitable guard chamber in the feed line. An excess of olefins or of H2 over the low intermediate concentrations inhibits the reaction. Catalyst stability is greater at low temperatures and higher pressures, and is also affected by the ratio of Pt/Al2O3 to WO3/SiO2.
Catalysis—Evidence from E.P.R. Is Presented for the Formation of Paramagnetic Platinum by Interaction of Nitric Oxide with Platinum Deposited on Amorphous Alumina
a. ghorbel, p. meriaudeau and s. j. teichner, Comptes Rend., Sér. C, 1973, 277C, (17), 739–741
Pt deposited on amorphous Al2O3 shows paramagnetic deviation after adsorption of NO. The conditions for the formation of this paramagnetic Pt, as well as the characterisation of its E.P.R. spectrum at 77K are described and discussed.
Effect of Electrolyte Composition on Hydrogen Adsorption by Platinum, Rhodium and Platinum-Rhodium Skeleton Catalysts
t. m. grishina, l. i. logacheva, v. i. fadeeva, a. i. strat'ev and g. d. vovchenko, Vest. Moskov. Univ., Ser. II, Khim., 1973, (5), 586–590
Studies of the effect of electrolyte composition on the H2 adsorption of Pt metal Raney-type catalysts showed that their ability to adsorb H2 increases as the content of Rh compared to Pt increases in the electrolyte from which the metals are deposited.
Heats of Adsorption of Hydrogen on Skeleton Platinum and Rhodium Catalysts in Sulphuric Acid Solutions
t. m. grishina, l. i. logacheva and g. d. vovchenko, Zh. Fiz. Khim., 1973, 47, (11), 2872–2874
Charging curve studies of the adsorption of H2 on skeleton Pt and Rh catalysts in 1N H2SO4 at 20°C intervals from 20 to 80°C showed that adsorption decreases as temperature increases. Adsorption isotherms were plotted, the effect of heterogeneity of the surfaces was calculated, and heats of adsorption and energy of bonding of H2 to the surface were determined.
Changes in the Morphology of Platinum Agglomerates during Sintering
k. kinoshita, k. routsis, j. a. s. bett and c. s. brooks, Electrochim. Acta, 1973, 18, (12), 953–961
Pt black was sintered at 150°C in 96% H3PO4 at various potentials, and the surface area and particle size of the blacks were measured, and any morphological changes were noted. Results indicate that the loss of surface area is accompanied by densification of the agglomerates. Pore size distribution measurement confirmed that pore volume decreases and small pores <10Å are preferentially eliminated; there is also some evidence that some occlusion of pores may occur.
The Mechanism of Aromatisation on Platinum Black Catalyst; Dehydrocyclisation of Hexadienes and Hexatrienes
z. paÁl and p. tÉtÉnyi, J. Catalysis, 1973, 30, (3), 350–361
Studies of aromatisation of hexadiene isomers and of trans - and cis -1, 3, 5-hexatriene on Pt black in He and H2-He mixtures showed C6H6 formation in all cases to be of the same order of magnitude. Catalyst activity rapidly decreased when successive pulses of hydrocarbons were introduced without regeneration. Cis -1, 3, 5-hexatriene was the exception—C6H6 yield was higher and deactivation was slower. Even small amounts of H2 slowed the deactivation. The reaction involves dehydrogenation followed by cis-trans isomerisation. These processes are equally important but ring closure is very fast. Trans -polyenes are precursors of coke formation on the catalyst surface. H2 in the gas phase determines the relative importance of C6H6 and coke formation.
Propylene Hydrogenation over Platinum/Carbon Molecular Sieve Catalysts
d. l. trimm and b. j. cooper, J. Catalysis, 1973, 31, (2), 287–292
Studies were made of the kinetics of hydrogenation of propylene over Pt/C molecular sieve catalyst and the rates of adsorption and diffusion of reactants and products in the catalyst was found to be a controlling influence on the kinetics.
On the Connection of the Direction of Hydrogenolysis of Ethylcyclopentane with Its Electronic Structure
a. m. boganov, a. m. gyul'maliev, i. i. levitskii, kh. m. minachev and i. v. stankevich, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1973, (10), 2257–2260
As rises from 0.8 to 7.8 atm the direction of hydrogenolysis of ethylcylopentane over 20% Pt/C at 250°C changes to give more breakage of bonds adjacent to the ethyl group. The electronic behaviour during such reactions was studied. The direction of the catalysed reaction is related to the electronic structure of the reacting molecule and the catalyst.
Hydrogenolysis of Spiro[2, 3]hexane on Platinised Kieselguhr
n. s. nametkin, v. m. vdovin, e. sh. finkel’htein, a. m. popov and a. v. egorov, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1973, (12), 2806–2807
Hydrogenolysis of spiro[2, 3]hexane on 15% Pt/kieselguhr at 100°C in a flowing system led to the formation of gem -dimethylcyclobutane but at 140−150°C the main substance formed was ethylcyclobutane.
Influence of the Conditions on the Rate of Conversion of Anatase to Rutile
v. i. bystrov, v. v. avksent'ev and v. a. sokolov, Zh. Fiz. Khim., 1973, 47, (10), 2561–2564
X-ray studies of the phase composition of TiO2 in powder form and as a thin layer on the surface on Ti membranes showed that the ratio rutile: anatase depends on the conditions of TiO2 formation and on the duration of exposure at different temperatures. Addition of Pt group metal compounds, e.g. RuO2 and PdO, accelerates the conversion of anatase to rutile.
Hydrogenation of Alkyl-substituted Naphthalenes over Palladium
t. j. nieuwstad, p. klapwijk and h. van bekkum, J. Catalysis, 1973, 29, (3), 404–411
The kinetics of the hydrogenation of a series of alkyl- and dialkylnaphthalenes over Pd/C in CH3COOH was studied at 80°C and atmospheric pressure. The mechanism of H2 addition was also discussed. Competitive hydrogenations showed that bulky alkyl substituents reduce absorption.
On the Stereoselectivity of Heterogeneous Catalysts, Modified by Optically Active Polyelectrolytes
v. k. latov, v. m. belikov, k. k. babievskii and a. i. vinogradova, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1973, (12), 2764–2770
Optically active phenylalanine was formed during hydrogenation of the methyl ether of α-acetoaminocinnamic acid over Pd black and Raney Ni modified by optically active styrene copolymers with alanine maleimide. The pH of the modifier of Pd black affects both the size and the direction of rotation of the phenylalanine. The size and type of stereoselectivity of the catalysts is related to pH of the modifier by complexes formed on the catalyst surface due to configurational changes of the optically active polyelectrolytes related to the stage of their dissociation.
On the Effects of Ultraviolet and Visible Light on the Catalytic Oxidation of CO on Pd, Pt and Ag
a. v. sklyarov, a. g. vlasenko and i. i. tret'yakov, Zh. Fiz. Khim., 1973, 47, (11), 2894–2895
The observed increase in the rate of oxidation of CO by O2 over Pt and Pd during exposure to UV and visible light is connected only with the initial heating of the catalysts In the case of Ag, no reaction is observed either during exposure to or absence of light.
Conversion of n -Heptane during Reaction with Water Vapour on Rhodium/Alumina Catalyst
g. l. rabinovich, l. m. treiger and g. n. maslyanskii, Neftekhimiya, 1973, 13, (5), 659–664
Both conversion of n -C7H16 and its dehydrocyclisation occur during passage of n -C7H16 and H2O vapour over 0.6% Rh γ-Al2O3; the ratio of these processes at 430−480°C is 3.0–3.5. Product yields are determined by the depth of conversion of the initial hydrocarbon. The yield of C6H6 significantly exceeds that of C6H5.CH3 because the latter is dealkylated without intermediate desorption.
Effect of Carbon Monoxide on the Selectivity of Dealkylation of Toluene on Rhodium Catalyst
l. m. treiger, g. l. rabinovich and g. n. maslyanskii, Kinet. Kataliz, 1973, 14, (6), 1582–1584
Studies of dealkylation and decomposition of toluene over 0.6% Rh/Al2O3 at 430°C, atm. pressure showed that, as CO is introduced up to CO: toluene=0.33, the decomposition is strongly retarded while the reduction in dealkylation is insignificant. CO also retards the decomposition of C6H6 reacted with H2O vapour.
Hydroformylation of Methyl Oleate with a Recycled Rhodium Catalyst and Estimated Costs for a Batch Process
j. p. friedrich, g. r. list and v. e. sohns, J. Am. Oil Chem. Soc., 1973, 50, (11), 544–548
Methyl oleate was hydroformylated to methyl formylstearate at 120°C, 850–900 p.s.i.g. with a 1:1 mixture of H2 and CO. In the presence of triphenylphosphine, an activated Rh/Al2O3 catalyst produced essentially quantitative conversion in 40 min. Preliminary processing costs based on a hypothetical plant are given.
The Catalytic Hydrogenation of Substituted 4-Chromanones and 4-Chromanols
j. a. hirsch and g. schwartzkopf, J. Org. Chem., 1973, 38, (20), 3534–3536
Hydrogenations over 5% Ru/C of 6- and 7-carbomethyoxy-4-chromanones, 6-methyl-4-chromanone, 6-carbomethoxy-4-chromanol, and the ethylene ketal of 6-carbomethoxy-4-chromanone showed that there are conditions for which the ketones have perhydro alcohols as the major products. Electron donating ring substituents seemed to minimise significantly any competing hydrogenolyses.
Synthesis of Polymethylene from Carbon Monoxide and Hydrogen
h. pichler and f. bellstedt, Erdöl Kohle, 1973, 26, (10), 560–564
Temperatures of 100−120°C and pressures of 1000–2000 atm were used in the synthesis of polymethylene from CO and H2 in the presence of Ru catalysts, the activity of which was increased by H3PO4 treatment to produce large amounts.
Relation of the Catalytic Activity of Palladium-Ruthenium Alloys to Their Composition and Conditions of Heat Treatment
e. v. khrapova, v. m. gryaznov, v. i. kaluga, n. r. roshan, v. i. shimulis, b. dzhuntini and v. v. kornilov, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1973, (11), 2431–2436
Studies of the heat treatment of 4.4−9.2% Ru-Pd alloys in air, H2 and Ar showed that raising the temperature from 350 to 750°C during treatment in air and also repetition of this treatment in air at 750°C produces greater catalytic activity, connected with a rise in the pre-exponential factor. Yet more activity caused by a fall in the activation energy is obtained by treatment with air followed by H2 and then fast cooling in H2.
The Catalytic Reduction of Nitric Oxide over Supported Ruthenium Catalysts
k. c. taylor and r. l. klimisch, J. Catalysis, 1973, 30, (3), 478–484
Studies of Ru/Al2O3 or Ru/SiO2 spheres as catalysts for NO reduction in simulated exhaust gases showed that the rate and temperature of NO removal depends largely on NO inlet concentration and are independent of the concentration of reducing agents. Selectivity for N2 formation depends on concentration of reducing agents CO2 and H2 as well as NO concentration. No NH3 intermediate was indicated in the NO→N2 reduction over Ru. Ru is highly selective for this reaction because CO inhibits NO reduction over Pt and Pd but not over Ru.
Complex Metal-Polymer Catalysts for Benzene Hydrogenation
e. n. rasadkina, a. t. teleshev, i. d. rozhdestvenskaya and i. v. kalechits, Kinet. Kataliz, 1973, 14, (5), 1214–1221
Complex organoplatinum hydrogenation catalysts supported on nylon can produce up to 1.5% cyclohexene during gas phase conversion of C6H6 amounting to 15%.
Silyl Complexes of Nickel, Palladium and Platinum
d. j. jones, Organomet. Compounds, 1973, 23, (10), 234–238
Studies of the preparation of organosilicon compounds in reactions of hydrido-silyl compounds with an olefinic compound in the presence of Ni, Pt, Pd metal complexes and their influence as catalysts in the hydrogenation of disilanes, the exchange of Si-Cl, Si-H atoms in hydrosilylation and polymerisation of acetylenic compounds are discussed.
Palladium(II) Chloride Catalysed Decomposition of Vinyl Acetate in Dry Acetic Acid
p. m. henry, J. Org. Chem., 1973, 38, (20), 3596–3600
Two regions of kinetic behaviour occur in decomposition of vinyl acetate to give CH3CHO and Ac2O; at low Cl−, high Pd(II) and high vinyl acetate concentration the reaction rate was almost independent of them and addition of Ac2O depressed the rate only slightly; at high Cl−, low Pd(II) and low vinyl acetate concentrations the kinetic behaviour conventionally follows −d[C2H3OAc]/dt = k[Li2Pd2Cl6][C2H3OAc]/[LiCl] and Ac2O strongly inhibits the reaction. A proposed mechanism includes slow formation of H2O and Ac2O without Pd(II) catalysis. H2O then reacts with vinyl acetate to give CH3CHO and CH3COOH in a Pd(II) catalysed reaction. Either H2O formation or the H2O-vinyl acetate reaction can be the rate-limiting step.
Effect of Solvents on Isomerisation of Heptene-1 in the Presence of π-Complexes of Palladium(II) Chloride
g. m. panchenkov, g. v. demidovich, i. n. kartsivadze and yu. m. zhorov, Neftekhimiya, 1973, 13, (5), 650–654
Studies of the effect of solvents on the isomerisation of heptene-1 with complexes of Pd(II) showed that alcohols most effectively accelerate the process; acetone, nitrobenzene and acetic acid have little effect; C6H6 retards the reaction. Alcohols in the presence of π-complexes of PdCl2 encourage the formation of trans isomers. Process rates with alcohols increase as the polarisability of the alcohol molecules decreases.
Asymmetric Catalytic Reduction with Transition Metal Complexes. II. Asymmetric Catalysis by a Supported Chiral Rhodium Complex
w. dumont, j.-c. poulin, t.-p. dang, and h. b. kagan, J. Am. Chem. Soc., 1973, 95, (25), 8295–8299
An insoluble chiral-polymer-supported Rh complex closely related to the soluble Rh(I)-diop complex (diop=2, 3-0-isopropylidene-2, 3-dihydroxy-1,4-bis(diphenylphosphino) butane) was prepared using a Merrifield resin. Synthesis of this catalyst and its use in heterogeneous asymmetric catalysis involving Rh complexes are discussed.
Selective Hydroformylation of Unsaturated Fatty Acid Esters
e. n. frankel, Ann. N. Y. Acad. Sci., 1973, 214, 79–93
The preparation and use of Rh-Ph3P catalyst for the selective hydroformylation of fatty acid esters and its use in hydroformylation of Me oleate, linseed oil and safflower oil was discussed.
Selective Hydrogenation or the Cyclohexadienes Catalysed by trans -IrCl(CO) (PPh3)2
j. e. lyons, J. Catalysis, 1973, 30, (3), 490–494
Trans -IrCl(CO)(Ph3P)2 catalyses hydrogenation of isomeric cyclohexadienes smoothly and selectively under mild conditions to give predominently cyclohexene, and little or no isomerisation or disproportionation. Deuteration studies established the reaction mechanism.
Synthesis and Catalytic Properties of Some CarbonyltriphenyIphosphineruthenium(II) Complexes
b. j. james, l. d. markham, b. c. hui and g. l. rempel, J. Chem. Soc., Dalton Trans., 1973, (21), 2247–2252
[HRuCl(CO)2(PPh3)2], [RuCl2(CO)2(PPh3)2], [RuCl2(CO)(PPh3)2], and [RuCl2(CO)(PPh3)2L] complexes were prepared from [RuCl2(PPh3)3]. Analogous bromo-complexes were also synthesised. Solvent molecules (L=NN′-dimethylformamide, NN′-dimethylacetamide, or dimethyl solphoxide) are co-ordinated to the metal through O, and are removed by recrystallisation from CH2Cl2-CH3OH. Under mild conditions these complexes show low activity for olefin hydrogenation and are ineffective for hydroformylation but [RuCl2(CO)(PPh3)2] is an efficient olefin isomerisation catalyst.
Reduction of Ketones by Secondary Alcohols Catalysed by Triphenylphosphine Complexes of Ruthenium and Rhodium
v. z. sharf, l. kh. freidlin and v. n. krutii, Izv. Akad. Nauk S.S.S.R., Ser Khim., 1973, (10), 2264–2267
The rate of reduction of cyclohexanone by alcohols in the presence of RuCl2(PPh3)3 is not related to the length of the alkyl chains in C4-C11 secondary alcohols, or to the presence of secondary butyl or cyclohexyl radicals, but falls sharply during transition to 3-, 4- and 5-alcohols and 3,3-dimethyl-2-butanol. Alkylphenylcarbinols reduce ketones faster than do secondary alcohols and promote conversion of the latter. RuCl2(PPh3)3 catalyses ketone reductions by alcohols in descending rates: cyclohexanone > acetophenone > cyclopentanone > 2-hexanone ≥cycloheptanone > cyclooctanone. RhCl(PPh3)3 has greater activity for H transfer than RuCl2(PPh3)3; on it the rate of reaction is scarcely related to alcohol or ketone structure.
Electrolytic Preparation of Highly Dispersed Pd-Ag Powders of Predefined Chemical Composition
b. p. yur'ev and s. p. shkuryakova, Porosh. Metall., 1973, 13, (6), 6–10
X-ray studies were made on highly dispersed Ag-Pt powders obtained electrolytically from NH3 solution with Pt and Ag nitrates and on the effect of different electrolysis parameters on their current yields, chemical compositions and dispersion.
DENTAL AND MEDICAL USES
Towards a Dosimetric System for Use with Iridium-192 Wires in Interstitial Therapy: a Suggested Protocol for Planning the Single Plane Implant
a. wambersie and a. dutreix, Atomkern. Energie, 1973, 22, (2), 134–138
The results of a dosimetric study for planning single plane implants of parallel equidistant Ir–192 wires are described. Dose distributions were computed for different arrangements of wires.