Platinum Metals Rev., 1965, 9, (4), 140
ABSTRACTS: October 1965
of current literature on the platinum metals and their alloys
The Adsorption of Krypton on Platinum Films Thermally Treated
ya. adamek, v. d. yagodovskii and v. m. gryaznov, Kinetika i Kataliz, 1965, 6, (3), 486-492
Kr adsorption showed that thermal treatment of Pt films at 100-740°C increased their surface areas or maintained them at their original value. Surface heterogeneity was reduced. Treatment of Pt film on glass at 630ºC caused ageing and decreased the surface area at lower temperatures due to defect formation.
The Problem of the Nature of the High Coercive Force in Cobalt-Platinum Alloys
d. d. mishin, ya. s. shur and v. i. timoshchuk, Fiz. Met. Metalloved., 1965, 19, (5), 793-796
The magnetisation of equiatomic Co-Pt alloys was studied at —196 to 350°C to relate their coercivity Hc to magnetic saturation Is and magnetic anisotropy constant K. Coercivity is greatly reduced as the temperature rises but Is changes less. These variations are related to the two-phase b.c. composition of the alloys—cubic and irregular; tetragonal and regular.
Use of Platinum Alloy for Electrical Leads at Liquid Helium Temperatures. Heat Conductivity
a. j. buhl and w. f. giauque, Rev. Sci. Instrum., 1965, 36, (5), 703
9% W-Pt has small thermal conductivity and is therefore useful in superconducting leads for work in high magnetic fields. Observed and calculated values were in good agreement between 1 and 4°K.
Equiatomic Transition Metal Alloys of Manganese. IV. A Neutron Diffraction Study of Magnetic Ordering in the PtMn Phase
a. f. andersen, a. kjekshus, r. m. øllerud and w. b. pearson, Phil. Mag., 1965, 11, (114), 1245-1256
PtMn with CuAuI structure has antiferromagnetic arrangement of magnetic moments with spin quantum numbers of 4/2 for Mn atoms, o for Pt atoms. Moments of nearest-neighbour Mn atoms in (001) planes are antiparallel. Direction of moments is parallel to c in ≤50 at.% Pt alloys, perpendicular to c in >50 at.% Pt alloys. Néel temperatures are observed at 840-970°K. Weak ferro-magnetism at lower temperatures is caused by canting of the moments.
Semiconducting Properties of PtSb2
d. h. damon, r. c. miller and a. sagar, Phys. Rev., 1965, 138, (2A), A636-A645
Hall coefficient, electrical conductivity, Seebeck coefficient, magnetoresistance, piezo resistance, magnetic susceptibility, and elastic constants of PtSb2 were measured in the range 78-1200°K. Samples from a PtSb2 melt were p -type and additions of Te produced n -type samples.
Mass Spectrometric Knudsen Cell Measurements of the Vapour Pressure of Palladium and the Partial Pressure of Palladium Oxide
j. h. norman, h. g. staley and w. e. bell, J. Phys. Chem., 1965, 69, (4), 1373-1376
Measurements of the vapour pressure of Pd and of the partial pressure of PdO(g) in equilibrium with Pd(s) in an O2 atmosphere are ΔH°298 = 91.0 kcal/mole for Pd(s)=Pd(g), and ΔH°298 = 83.4 kcal/mole and ΔSº298 = 18.8 e.u. for Pd(S)+½O2=PdO(g). log PPd(atm) = (—19,370/T)+6.120 at 1485-1710ºK.
X-ray Investigation of the Solubility of Hydrogen in Dispersed and Compacted Palladium
zh. l. vert, i. a. mosevich and i. p. tverdovskii, Zh. Fiz. Khim, 1965, 39, (5), 1061-1064
X-ray measurements of lattice spacings of Pd black and Pd foil during dissolution and desorption of H2 in near-equilibrium conditions showed that the parameters of the α and β phases at the α-β transition remain constant and are unrelated to H3 content and process direction. The (Pd-H)β phase grows linearly in agreement with solubility isotherms starting with Ch: CPd= 0.53/0.54. Linear growth also occurs in 10% Cu-Pd in spite of the absence of a horizontal stage on the solubility isotherm.
Dilute Ferromagnetic Alloys
j. crangle and w. r. scott, J. Appl. Phys., 1965, 36, (3/2), 921-928
Magnetic moments and Curie temperatures were measured for dilute Fe-Pd, Fe-Pt, Co-Pt, and Ni-Pd alloys. Ferromagnetism also occurs in Gd-Pd and Fe-Au alloys.
Diffusion of Hydrogen through Palladium and Palladium-Silver Alloys
d. m. jewett and a. c.makrides, Trans. Faraday Soc., 1965, 61, (5), 932-939
Tests on 0.0051 cm thick Pd and 0.0025 cm Ag-Pd membranes showed that the permeation rate of H2 at 27°C depends on the pressure by a relation derived for a two-phase system with different diffusion constants and that the permeation rate decreases with increasing Ag content at room temperature. The diffusion constants are 1.6 x 10–7 cm2/s in the low H2-content α-phase; 1.5 x 10–6 cm2/s in the high H2-content β-phase.
Wettability of Metals under Continuous Condensing Conditions
r. a. ERB J.Phys. Chem., 1965, 69, (4), 1036-1309
Wettability tests in pure steam for long periods gave contact angles for Au,55-85°; Ag,68-89°; Rh, 65-82º; Pd, 74°; Pt, 50°. H2O condensed as a film on Ni, Cd, Ti, Cr, type 316 stainless steel, 10%Ni-Cu, and quartz, indicating zero or low contact angles. A clean “high-energy surface” of metal substantially O2-free is not wettable by H2O.
Constitution Diagram and Some Properties of Alloys of the Nickel-Rhodium System
i. i. kornilov and k. p. myasnikova, Izv. Akad. Nauk S.S.S.R., Metally, 1965, (2), 175-179
Thermal, microstructural and X-ray tests on the Ni-Rh system showed that there is a continuous series of solid solutions but that the change in the lattice parameter deviates from linearity as Rh content increases. The anomalous increase in hardness which occurs at 61 at.% Rh is probably connected with the formation of a regular structure in the NiRh3 region.
Neutron and X-ray Diffraction Study of LiRh
s. s. sidhu, k. d. anderson and d. d. zauberis, Acta Cryst., 1965, 18, (5), 906-907
Rh and Li atoms occupy preferred positions in the hexagonal unit cell with Rh atoms in one layer and Li atoms in the other, the layers alternating along c at c0/2 distances apart. Space group is P; ao=2.649±0.003, co = 4.357±0.002 Å. Interatomic distances are Rh-Rh=Li-Li=2.649, Rh-Li=2.663 Å.
Phase Relations between Iridium and the Sesquioxides in Air
s. j. schneider, j. l. waring and r. e. tressler, J. Res. N.B.S., Sect. A, Phys. Chem., 1965, 69A, (3), 245-254
X-ray studies were made of the reactions in air between Ir and IrO2 with each of Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Y2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, In2O3, Sc2O3 and A12O3. Ir oxidises at low temperatures to IrO2, which dissociates at 1020°C. Nd2O3-IrO2 was studied in detail. Nd2O3-2IrO2 is a cubic pyrochlore phase which dissociates at 1190°C. 3Nd2O3-2IrO2 dissociates to Nd2O3 and Ir after possibly losing O2 at 1195°C. No further reactions between Nd2O3 and Ir occurred up to 2000°C. The other rare earths behaved similarly but no apparent reaction occurred between IrO2 and ln2O3, Sc2O3 or A12O3.
Hot-stage Microscope Determination of the Solidus Temperatures of Iridium Alloys with about 1 wt.% Boron, Phosphorus or Silicon
g. reinacher, Metall, 1965, 19, (7), 707-711
Tests on powder samples of 1.5 wt.% B-Ir, 1 wt.% P-Ir and 1.5 wt.% Si-Ir gave their solidus temperatures as 1046, 1262 and 1470°C compared with 750, 588 and 830ºC for the corresponding Pt alloys. This confirmed laboratory experience that Ir apparatus is much more corrosion-resistant than Pt apparatus to B, P and Si.
On the Structure of the Ruthenium-Silicon System
w. obrowskI Metall, 1965, 19, (7), 741-742
The system includes the silicides Ru2Si, RuSi and Ru2Si3 as well as Ru and Si mixed crystals. There are three eutectic and one peritectic reactions. RuSi and Ru2Si3 melt without decomposing. Ru dissolves <2 at.% (0.5 wt.%) Si in the solid state and Si dissolves at least 3 at.% (10 wt.%) Ru.
Equiatomic Compounds of the Transition and Lanthanide Elements with Rh, Ir, Ni and Pt
Enhanced Oxidation of Platinum in Activated Oxygen. II. Identity of Active Species and Oxide Formed
g. c. fryburg, J. Chem. Phys., 1965, 42, (11), 4051-4052
The O atom causes the enhanced oxidation of Pt in activated O2 above 800°C. The oxide formed is PtO2 which may partly decompose to give the impression that PtO has been formed.
Structural Studies on Platinum(II) Chloride
k. brodersen, g. thiele and h. g. schnering, Z. anorg. allgem. Chem., 1965, 337, (3-4), 120-127
X-ray studies of black-red single crystals of PtCl2 prepared by chemical transport methods showed that PtCl2 consists of Pt6Cl12 groups with Cl on the edges of an octahedron built up by 6 Pt atoms. PtCl2 is diamagnetic and has a different reflection spectrum to that of other Pt(II)-Cl compounds.
On the Hydrolysis of Potassium Chlorplatinite
n. m. nikolaeva, b. v. ptitsyn and i. i. gorbachev a, Zh. Neorg. Khim., 1965, 10, (5), 1051-1057
Equilibrium constants of the first stage of K2[PtCl4] hydrolysis were determined at 25,35,45 and 55°C from which the enthalpy is ΔHº = 5.35 kcal and the reaction constants are E=22.1 kcal, log PZ= 10, ΔH≠=21.51 kcal, Δs≠ = —12.7 eV. Measurements on the second stage at 35, 45 and 55°C give ΔHº =31.2 kcal.
The Hydrolysis of Potassium Chlorplatinate
n. m. nikolaeva, b. v. ptitsyn and e. d. pastukhova, Ibid., 1058-1061
The rate of the first stage of hydrolysis of K2[PtCl6] is less than the second. The rates increase with temperature. Equilibrium in the hydrolysis of K2[PtCl6] occurs after 1-5 h. At 22-55°C the orientation constants of the first and second stages ate 6.10–8 and 2.10–4. Dissociation constants of [Pt Cl5.H2O]_ are k =1.10-5 and of [PtCl4(H2O)2] are k1≈;6.3. 10–5 and k2≈6.3. 10–7.
Four New Complexes of Platinum and Palladium with Cyclooctene and 4-Vinyl-cyclohexene
e. kuljian and h. frye, Z. Naturf., 1965, 20b, (3), 204-205
The syntheses are reported of 4-vinylcyclohexene-Pt(II)-chloride and -bromide, and of cyclooctene-Pd(II)-chloride and -Pt(II)-chloride. Spectral data of these complexes are tabulated.
Cyclooctatetraene Palladium(II) Bromide; Synthesis and Characterisation
h. frye, e. kuljian and j. viebrock, Ibid., 269
Syntheses are reported for cyclooctatetraene Pd(II) bromide and for bis(benzonitrile) Pd(II) bromide.
Quinquevalent Rhodium Compounds: RhF5 and CsRhF6
j. h. holloway, p. r. rao and n. bartlett, Chem. Commun., 1965, (14), 306-307
RhF5 was prepared by the action of gaseous f2 on RhF3 at 400°C, 90 lb/in.2. It is a dark red solid, m.p. 95.5±0.5°C. Magnetic properties are tabulated. Crystal data are a = 12.28, b=9.85, c = 548 Å, β =99.2°. It is a powerful oxidising and fluorinating agent. CsF and RhF5 react in IF5 solution to form CsRhF6 which is similar to CsPtF6. Hexafluororhodates(V) were unknown previously.
On the Structure of Iridium(III) and of Ruthenium(III) Chlorides
k. brodersen, f. moers and h. g. schnering, Naturswissenschaften, 1965, 52, (9), 205-206
Two modifications of IrCl3 exist: α-IrCl3 as hexagonal, honey-brown, shiny flakes with a = c = 5.99±0.01 Å, b = 10.37±0.02 Å, β = 109.4±0.2°; β-IrCl3 as dark-red, bipyramidal crystals. Atomic distribution within α-IrCl3, crystals was studied. α-RuCl3 exists as black, shiny flakes but its parameters have not been determined exactly yet.
n. bartlett andp. r. rao, Chem. Commun., 1965, (12), 252-253
IrF5 was prepared by heating Ir metal in F2 gas, the elements being in stoichiometric ratio. The crystals are yellow and monoclinic with a = 12.5, b = 10.0, c=5.4 Å, β =99.8°, m.p. 105°C. Magnetic susceptibilities were measured between 77 and 296°C and are typical of d 4octahedral or near octahedral third-transition-series metal fluorides.
α- and β-Ruthenium Trichloride
k. r. hyde, e. w. hooper, j. waters and j. m. fletcher, J. Less-Common Metals, 1965, 8, (6), 428-434
Systematic study of the chlorination of Ru metal led to methods for the preparation of pure α-and β- RuCl3. The properties of these forms are described and previous confusion was dispelled.
Fluorine Bomb Calorimetry. XII. The Enthalpy of Formation of Ruthenium Pentafluoride
h. a. porte, e. greenberg and w. n. hubbard, J. Phys. Chem., 1965, 69, (7), 2308-2310
The standard enthalpy of formation of RuF5 from calculations based on direct combination measurements in a combustion bomb calorimeter is ΔHf°298.15= –231.41±0.35 kcal/mol.
Carboxylates of Palladium, Platinum, and Rhodium, and their Adducts
t. a. stephenson, s. m. morehouse, a. r. powell, j. p. heffer and g. wilkinson, J. Chem. Soc., 1965, (June), 3632-3640
Pd(II) nitrate reacted with CH3COOH and C2H5COOH to form brown carboxylates Pd(OCOR)2. Benzoates formed by exchange reaaction were trimeric at 37°C but fluorocarboxylates were monomeric. The carboxylates reacted with amines, triphenylphosphine and triphenyl-arsine to give trans- [Pd(OCOR)2L2] complexes. Trimeric diacetatoplatinum(II) was formed by reducing CH3COOH solution of hexahydroxyplatinate(IV) with HCOOH. It is not isomorphous with [Pd(OCOMe)2]3.
Formation and Reduction of the Oxygen Layer on Cold-worked Platinum-Gold Alloys in Acid Solutions
m. w. breiter, Electrochim. Acta, 1965, 10, (5), 543-547
Periodic potentiostatic current/potential curves for 5-70 at. % Au-Pt alloys at 30°C, in N H2SO4 and N HClO4, at 30 and 300mV/s have a characteristic shape with two reduction waves during the cathodic sweep and, to a first approximation, are composed additively of the curves for the pure metals.
Anodic Properties of Platinum Chromium Alloys in Sulphuric Acid Solution
m. w. beeiter, Extended Abs., Theoretical Div., Electrochem. Soc., 1965, 3, (May), 18-19, abs. 254
Voltammetric studies of 3, 10, 20 and 44.49 wt.% Cr-Pt alloys at 30°C in NH2SO4 saturated with He gave current-potential curves which showed similarities with pure Pt at 3wt.% Cr but changes at higher Cr content indicating changes in the surface layer of the alloys. Impedance measurements distinguished those parts of the surfaces with electrochemical behaviour like Pt and those like Cr.
Effect of the Adsorption of Foreign Ions and Molecules on the Rate of Oxidation of Organic Substances on Platinum Electrodes
o. a. khazova, yu. b. vasil’ev and v. s. bagotskii, Elektrokhimiya, 1965, 1, (4), 439-445
Ions and molecules such as SO42_, HPO43_, Cs+, Na+, (CH4)4N+, C6H13OH affect the rate of oxidation of CH3OH and HCOOH on Pt in 1 N HClO4 and 1 N LiOH. Studies of the relation of ion and molecule adsorption to electrode potential show that the curve for neutral molecules has a maximum at 0.55 V where the O2 and H2 adsorption is a minimum. A mechanism for the anodic regeneration of Pt electrode catalysts is suggested.
LABORATORY APPARATUS AND TECHNIQUE
High Temperature, Small Diameter, Radial Heat Flow Thermal Conductivity Apparatus
c. j. glassbrenner, Rev. Sci. Instrum., 1965, 36, (7), 784-990
A cylindrical apparatus with radial heat flow and accurate to ±5% includes radiation shields made of 40% Rh-Pt, and Pt: 10% Rh-Pt thermocouples to measure the temperature gradients of specimens. Thermal conductivities of Ge and Si from 300°K to their melting points were measured. Mo was chosen for the crystal heater as tests showed chat Ge had eutectics with Ir and Ta at 909°C and 932°C respectively.
Evaluating Corrosion Resistance of Fused Cast Refractories
d. e. emhiser and w. j. englert, Glass Ind., 1965, 46, (7), 393-397, 423-424
Two dynamic methods used by Pittsburgh Plate Glass Co. are described. A relatively quick, cheap simulation of tank conditions is obtained using a Pt tank into which cullet flows. Four 2 in X 2 in X 6 in refractory samples are placed round the overflow in the base of the tank. Losses of weight and volume of these are measured at the end of the test. Advantages of this method are simple control, reproducibility and no need of standard specimens. The tank and samples are contained in a Pt-wound electric furnace controlled by Pt: 10% Rh-Pt thermocouples. The second method is to use a small-scale glass-melting furnace.
Platinum Metal Sulphides as Heterogeneous Hydrogenation Catalysts
f. s. dovell and h. greenfield, J. Am. Chem. Soc., 1965, 87. (12), 2767-2768
Pt metal sulphides are more active and stable than base metal sulphides for liquid and vapour phase hydrogenations, whether as bulk or supported catalysts. They are insensitive to S poisoning and reduce halogen-containing nitro compounds to amines without dehalogenation. They are useful for reductive alkylation of aliphatic amines and their nitroalkene precursors with aliphatic ketones and for selective hydrogenation of aryl disulphides to the corresponding thiophenols.
Hydrogenation of Olefins. Part 2. Reaction of Ethylene with Deuterium over Alumina-supported Ruthenium and Osmium
g. c. bond, g. webb and p. b. wells, Trans. Faraday Soc., 1965, 61, (5), 999-1006
Tests in a static system at 0-80°C with various C2H4 and D2 pressures showed that, over Ru/ A12O3, ethylene-d 1 forms about 50% of the initial products, that ethane -d 2 is the main ethane and that no ethylene -d 3, -d 4 nor ethane -d 5, -d 6 were formed. Over Os/Al2 O3, less ethylene-d 1 was observed, and other deuterated ethanes besides ethane-d 2. Hydrogenation rates were proportional to pD2. Activation energies were ~8.5 kcal/mol for hydrogenation; ~I2 kcal/mol for H2 exchange and/or olefin exchange. The behaviour of ethyl radicals is discussed.
Hydrogenation of But-2-yne. Part 1. Ruthenium- and Osmium-catalysed Reactions
g. webb and p. b. wells, Ibid., (6), 1232-1245
Reactions with H2, D2 at 80-150°C in a static system were studied. Total butene yields exceeded n -butane yields by nine times over Ru, four times over Os. Butene proportions were cis -but-2-ene > but-1-ene > trans -but-2-ene. D2 distributions were determined. Stereochemistry and selectivity in the stages of H2 addition are discussed.
Role of Catalytic Metals in Hydrocracking
h. beuther and o. a. larson, Ind. Engng. Chem., Proc Design & Dev., 1965, 4, (2), 177-181
Tests on Pt/SiO2-Al2O3 and Ni/η-Al2O3 catalysts showed that the principal role of the metals was to keep the acidic sites free of coke precursors. They also formed the olefin intermediates needed in subsequent carbonium ion reactions. Rate of hydrocracking for on-stream or aged catalysts depends on the size of the metal crystallites, which controls the area of support which remains cake free and available for cracking and isomerisation. Pt catalysts tested contained between 0.13 and 2.86% Pt.
Feeling the Jolt
Chem. Week, 1965, 96, (20), 69-74
A review of newly-patented hydrocracking processes in the petroleum industry. Catalyst and H2 needs are likely to increase but olefin output will diminish. As well as Ni and W, there are new catalysts such as nitrided Ag and Rh on SiO2-MgO and Pd on activated zeolite.
Catalytic Isomerisation of the Leading Fractions of Straight-run Petroleum Distillate
n. r. bursian, g. n. maslyanskii and n. k. volnukhina, Khim. i Tekhnol., Topliv i Masel, 1965, (6), 1-4
A study of the isomerisation of pentane and hexane fractions over Pt catalysts established the process method, the product yield, composition and properties of these products. The octane number of fractions distilled up to 62°C can be raised from 73 to 85. If these fractions are jointly treated with hexane raffinate separated from the products of catalytic reforming then an octane number of 80 can be obtained.
The Influence of Gaseous Oxygen Atoms on the Catalytic Oxidation of Ammonia on Pt-Rh
e. molinari, f. cramarossa, a. pullo and l. triolo, J. Catalysis, 1965, 4, (3), 341-353
O atoms in the gas phase significantly reduce the activation energy of the catalytic oxidation of NH3 on Rh-Pt gauze. Tests were carried out at 350-750°K, 1 Torr. The kinetics of the reaction are controlled by diffusion processes. NO and H2Owere practically the only oxidation products. Small activation energies are compensated by small pre-exponential factors.
Catalytic Synthesis of Hydrogen Cyanide from Acetonitrile and Ammonia
a. ozaki, y. shiratsuti and k. mori, J.Chem.Soc. Japan., Ind. Chem. Sect., 1965, 68, (2), A14, En. abs.
Studies at 700-1000°C gave optimum yields of 1.5 mole HCN/mole CH3CN using Pt/Al2O3 and of 1.4 mole HCN/mole CH3CN using Pt gauze.
Investigation of the Effect of Thiophene on the Properties of Pd-, Rh-, Ru- and Pt-Al2O3 Catalysts during the Dehydrogenation of Cyclohexane
kh. m. minachev, d. a. kondrat’ev and p. i. slyuntaev, Izv. Akad. Nauk S.S.S.R., Ser.Khim., 1965, (6), 999-1003
Cyclohexane both pure and with 0.5, 1.0 and 2.0% thiophene was reacted over 1% Pd, Rh, Ru and Pt/Al2O3 at 450°C, 20 atm H2, v=2 h–1, molar ratio H2: HC=5:1. Pd/Al2O3 and Rh/Al2O3 showed less hydration of pure cyclohexane but more isomerisation activity than Pt/Al2O3. Ru/Al2O3 was relatively inactive. Thiophene reduced the activity for dehydration with increasing concentration. S distribution within the catalyst bed varied with the catalyst used.
The Hydrogenation of Acetylene. I. The Reaction of Acetylene with Hydrogen Catalysed by Alumina-supported Platinum
g. c. bond and p. b. wells, J. Catalysis, 1965, 4, (2), 211-219
Kinetics and product analyses for C2H2 hydrogenation in a static system over 5 mol.% Pt/ α-Al2O3 at 40-140°C indicate more selectivity for C2H4 formation as the temperature rises and the H2 pressure decreases. C2H2 is selectively removed when C2H2/C2H4 mixtures are hydrogenated. The composition of C4 hydrocarbons produced by C2H2 polymerisation has been determined. The reaction mechanism is discussed. Thermodynamic and mechanistic factors enable this catalyst to produce olefin rather than paraffin, while at the same time it possesses very high olefin hydrogenation activity.
The Catalysed Low-temperature Hydrogen-Oxygen Reaction
m. ladacki, t. j. houser and r. w. roberts, Ibid., 239-247
Best catalyst at low temperatures for the H2-O2 reaction was Pt-Rh-Pb/Al2O3. Pd, Pt and Rh were effective metals but Ni was poor. Various catalyst pretreatments and changes in the gas flow were studied on 19 catalysts between 25°C and—196ºC. High surface area and thorough drying of the catalysts before use were essential, the nature of the support was important, and yields of H2O were sensitive to changes in gas flow rates. The reaction may require a higher activation energy than the similar H-D isotopic exchange reaction at low temperatures.
Vapour-phase Dehydrocyclisation of Some Aromatic Hydrocarbons
d. a. scola, Ind. Engng. Chem., Product Res. Dev .,1965, 4, (2), 136-139
Fused ring systems were formed when diphenyl-methane, bibenzyl, trans -stilbene, 1,4-diphenyl-butadiene and I, I’ - binaphthyl were treated over 0.6% Pt/SiO2 at 550°C in H2 atmosphere. Major reaction was abstraction of nuclear H2 followed by intramolecular bond formation.
Reaction of p -Xylene with Deuterium on Supported Platinum Catalysts
j. w. hightower and c. kemball, J. Catalysis, 1965, 4,(3), 363-373
H-D exchange and deuteration of p -xylene on various Pt catalysts showed that, after allowing for different dispersions of Pt by expressing rates in terms of Pt available to chemisorb H2, results were similar for catalysts on the same support but obtained from different sources. At 100°C, exchange of ring atoms ≥ exchange of methyl H atoms >deuteration, but rates varied as the support changed from γ-Al2O3 to α-A12O3 or to SiO2. H2O strongly held on the supports may effect catalytic activity.
Chemisorption and Catalysis on Platinised Silica Gel. I. Dispersion of Platinum According to Chemisorption Data
o. m. poltorak and v. s. boronln, Zh. Fiz. Khim., 1965, 39, (6), 1476-1482
Tests at —196 to 200°C, 10-5 to 1.7 mm Hg showed that optimum conditions ( —196ºC, 10–5 to 10–2 mm Hg) for H2 chemisorption on Pt/SiO2occur when the number of Pt atoms on the crystal surface equals the number of adsorbed H atoms. Best conditions for catalyst preparation are those that cause all the Pt to be deposited on the surface of the SiO2 so that it can adsorb H2. This was confirmed using three series of differently prepared catalysts containing up to 7.2 wt.% Pt. The Pt dispersion did not depend on the amount of Pt used.
Conversions of Methycyclooctane in the Presence of Platinum Catalysts
e. s. balenkova, n. a. khafizova, s. i. khromov and b. a. kazanskii, Dokl. Akad. Nauk S.S.S.R., 1965, 161, (6), 1329-1332
The products of the conversion of methyl-cyclooctane over 5% Pt/C are exo- and endo-2-methyl-cis -pentalane (40%), exo- and endo-3-methyl-cis -pentalane (28%). 1-methyl-cis -pentalane (8%), hydrogenation products of these isomers (23%), and methyl-octane (1%). Conversion over an Fe-Pt catalyst gave slightly more of the methyl-cis -pentalanes.
Determination of the Area of Active Surface of Platinum Black during Catalytic Reactions
t. i. gorokhova, a. n. mal’tsev and n. i. kobozev, Zh. Fiz. Khim., 1965, 39, (5). 1206-1210
A linear relationship exists between poisoning of Pt black catalysts by Pb acetate and the rate of H2O2 decomposition or of C2H5OH oxidation, showing that Pb ions block active centres. Poisoning data show that 1/3 of the Pt surface is active; adsorption data show that 1/5 is active.
Catalytic Activity of Platinum Black, III. Adsorption and Decomposition of Butanes
d. w. mckee, J. Am. Chem. Soc., 1965, 87, (8), 1681-1686
Studies on adsorption and catalytic decomposition of n- and iso -C4H10 on sintered Pt black at 0-180°C showed that below 50°C physical adsorption occurred with coverages more than a monolayer, that at 50-80°C there was an increasing amount of irreversible chemisorption, and that above 80°C desorption of CH4, C2H6 and C3H8 occurred with a carbonaceous residue left on the surface. n- C4H10 decomposed more than iso -C4H10 above 100°C. Both cracked more readily than C3H8. Product distribution was different from hydrocracking with excess H2. There was no isomerisation. The reaction kinetics depend on the rate of hydrogenation of adsorbed hydrocarbon residues.
The Recombination of Atoms on Pd-Au Alloys
p. g. dickens, j. w. linnett and w. palczewska, J. Catalysis, 1965, 4, (2), 140-152
The time of exposure of annealed Pd-Au foils to radiation affected the atom recombination co-efficient γfor H2. For short exposures, the maximum activity occurred with 0-55% Au (γ ~ 10-2) and activity decreased as Au content rose to 100% (γ ~ 10–3). For long exposures, γ varied less but was still 10-3 at 100% Au. γ~10–3 to 10-4 for O2 and was not related to alloy composition. In all cases the disappearance of atoms from the gas phase was first order.
Catalytic Studies on Alloys. XXV. The Parahydrogen Conversion on Silver-Palladium Alloys
g. rienÄcker and s. engels, Z. anorg. allgem. Chem. 1965, 336, (5-6), 259-269
Tests on Ag-Pd foils at 200°C showed that maximum activity for conversion occurs at 80-70% Pd, with decreasing activity down to 0% Pd, i.e. pure Ag. Activation energies increase to ~9 kcal for 100-70% Pd, decrease to 6 kcal at 53.5% Pd, and increase to 11 kcal for Ag-rich alloys with between 50 and 20% Pd. The effects of Ag and H2 on the catalytic activity of Pd for the hydrogenation of gaseous C6H6 were also studied.
Catalytic Reduction of Inorganic Compounds by Carbon Monoxide in the Liquid Phase
a. b. fasman, v. d. markov and d. v. sokol’skii, Zh. Prikladnoi Khim, 1965, 38, (4), 791-800
Studies on catalysts and their concentration, on temperature, on pH, on Pco and on anion concentration during liquid phase reduction by CO of Cr2O72-,IO3–, Fe3+, [Fe (CN)6] 3–, Cu2+, and Sn4+ showed that the reduction rate depends on the respective sizes of the oxidation-reduction potentials and that the complex salt catalysts have activity Pd2+> Rh3+> Pt4+. Most active was [Pd Br4]2–. Cl– showed the reaction but Br, down to 0.2 g.ion/1, speeded it up. Reduction rates are given for various ions and a reaction mechanism is proposed.
The Synthesis of βγ-Unsaturated Esters from Conjugated Dienes
s. brewis and p. r. hughes, Chem. Commun., 1965, (8), 157-158
The yield of methyl pent-3-enoate from butadiene, CO and CH3OH, which depends on the Pd catalyst used, was only 1-2% with sodium chloropalladite or sodium bromopalladite but was 35-40% with sodium iodopalladite. To prevent catalyst decomposition above 70°C a ligand such as tributylphosphine was added which raised the optimum reaction temperatures to 150°C. Bridged Pd complexes were the best catalysts. The reaction appears to be general for synthesis of βγ-unsaturated esters from conjugated dienes. Yields were up to 73%.
The Isomerisation of Olefins by Palladium Complexes
m. b. sparke, l. turner and a. j. m. wenham, J. Catalysis, 1965, 4, (3), 332-340
Various Pd complexes are efficient catalysts and completely specific for low-temperature, liquid-phase olefin isomerization. 0.1 mole % Pd complex concentrations may give almost complete equilibrium of isomers at 50-60°C. The olefin-PdCl2. complex appears to be the true catalyst and is formed by addition to the olefin of PdCl2. or a complex with a displaceable ligand such as PdCl2-bis-(benzonitrile). Relative rates of methyl-pentene isomerisation were studied. During the process certain isomers are formed preferentially but simple stepwise migration of the double bond does not adequately explain this.
The Selectivity of the Cu/Pd Catalyst in the Oxidation of Hydrogen/Carbon Monoxide Mixtures and the Mechanism of this Reaction
a. krause, Roczniki Chem., 1965, 39, (3), 355-356
The influence of Pd content on catalyst selectivity is explained in terms of the reactor mechanism.
Reactions of Methoxy Hydroperoxides Derived from Methyl Oleate. Catalytic Hydrogenation
e. h. pryde, r. a. awl and j. c. cowan, j Am. Oil Chem. Soc., 1965, 42, (6), 549-553
Better yields of carbonyl compounds from the hydrogenation of methyl oleate ozonolysis products were obtained using poisoned catalysts and the proper choice of catalyst support. Formation of dimethyl azelate byproduct over Pd/C was 20% with no poison, 10% with CH3COONa in the support, 8% with triethylamine in solution. Pd/CaCO3-(CH3COO)2Pb gave 7%, Pd/ZnO with C5H5N or (CH3COO)2Pb gave 9%. Byproduct formation increases with support according to the order BaSO4, CaCO3, SiO2, A12O3, ZnO, C; i.e. BaSO4 is the best support and C is the poorest.
On the Aromatisation Power of Boride Catalysts of the Platinum Group Metals
m. i. rozengart, b. d. polkovnikov, v. l. polinin, a. m. taber and k. m. gitis, Izv. Akad. Nauk. S.S.S.R., Ser. Khim., 1965, (5), 919-922
Dehydrocyclisation of normal paraffins is catalysed by Pt group metals supported on active C. Pd-B and Pt-B gave sufficiently high stability in tests on N-octane at 550°C.
Low-pressure Hydrogenation of Alkoxyani-lines with Noble Metal Catalysts
m. freifelder, yew hay ng and p. f. helgren, J. Org. Chem., 1965, 30, (7), 2485-2486
5% Rh/Al2O3 gave the best yields of alkoxycyclo-hexylamines under low-pressure conditions. Hydrogenolysis and secondary amine formation were both small. Reaction time was shorter when CH3COOH was present than in neutral solvent. Rh/C is equally reactive but presented a greater fire hazard. 5% Pd/C and PtO2 were less successful.
Behaviour of Fuel Cell Porous Electrodes Fed with a Methanol Vapour Stream
p. longhi, Chim. e Ind., 1965, 47, (6), 606-610
Anodic oxidation of CH3OH at 25 and 65ºC in H2SO4 and H3PO4 solutions was studied using porous graphite disc electrodes coated with Pt group metals blacks. Pt, Rh and Ir behaved satisfactorily but Pd, Ru and Os were inactive or were quickly poisoned. For Pt black the highest current density was obtained with 0.5M H3PO4at 65°C. Higher current densities generally occurred with low electrolyte concentrations at high temperatures. H3PO4 solutions give higher current densities than H2SO4 solutions of equivalent concentration.
Cathodic Protection of Jetties
p. b. cherry. Corrosion Prevention and Control, 1965, 12, (7), 26-28
Platinised Ti anodes are superior to linseed oil impregnated graphite, silicon iron or scrap steel anodes, and can be used at 50-100A/ft2 in water with resistivity 25-2000 ohm cm. Oil wharves at Thameshaven and in the Persian Gulf have been protected by anodes mounted on unplasticised PVC and fixed to steel tubes immersed 6 ft below low water line and projecting 2½ ft from the steel jetty piles.
The Design and Application of a Steady-state Heat Flux Transducer for Aerodynamic Heat-transfer Measurements
d. l. johnson, I.S.A. Trans., 1965, 4, (l), 46-53
The temperature gradient across a thin ceramic disc is measured by thin-film Pt resistance thermometers painted on each side and fired at 1400°C. These transducers have been used to measure local convective heat transfer coefficients on models in the Boeing hypersonic wind tunnel.
Study of the Instability of Noble Metal Thermocouples in Vacuum
b. e. walker, c. t. ewing and r. r. miller, Rev. Sci. Instrum., 1965, 36, (5), 601-606
Studies were carried out at 800-1600°C on noble metal thermocouples and on thermoelements of Pt, Rh, Ir, Rh-Pt and Rh-Ir alloys. In vacuum, as in oxidising and neutral atmospheres, the main cause of instability is contamination by impurities, especially Fe, from the ceramic protection tubes.
Precise Temperature Measurement in Debye-Scherrer Specimens at Elevated Temperatures
r. g. merryman andc. p. kempter, J. Am. Ceram. Soc., 1965, 48, (4), 202-205
In this method lattice parameters are measured against the temperature of a primary standard forming one leg of a calibrated thermocouple with both specimen and junction in the X-ray beam, and mixing the internal standard with the specimen so that the lattice parameters of the former denote temperature. Au is the primary standard, Pt is the other thermocouple leg and N.B.S. have calibrated the Pt: Au thermocouple at 0-1000ºC