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Platinum Metals Rev., 1968, 12, (4), 146

ABSTRACTS: October 1968

of current literature on the platinum metals and their alloys

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PROPERTIES

Young’s Modulus of Single Crystals of Palladium at High Temperatures

h. masumoto, h. saito and s. kadowaki, J. Japan Inst. Metals, 1968, 32, (6), 529–532

Measurements at 0−600°C using a dilatometer and a vibrator-controlled oscillator system showed that the Young’s moduli of a Pd single crystal are 7.35, 13.77 and 19.44 × 105 kg/cm2 at 20°C in the <100>, <110> and <111> orientations respectively. The modulus in the <100> and <110> orientations decreases with increasing temperature but in the <111> orientation increases to a maximum at ≍250°C and then decreases. Calculated and measured values for a polycrystal are in good agreement.

A New Heat-treatment of Pt-Co Alloys of High-grade Magnetic Properties

h. kaneko, m. homma and k. suzuki, Trans. Japan Inst. Metals, 1968, 9, (2), 124–129

Detailed studies of the magnetic properties of ≍50 at.% Co-Pt revealed that double ageing at 680−720°C and 600°C effectively increased the coercive force and gave a maximum energy product (B.H)max=12.5 × 106G.Oe.

Uniaxial Magnetic Anisotropy Induced in Pt-Co Alloy by Tempering under Stress

s. shimizu and e. hashimoto, J. appl. Phys., 1968, 39, (5), 2369–2371

Tempering under compressive stress induces uniaxial magnetic anisotropy in 50 at. % Pt-Co with its easy axis along the direction of stress but tempering under tensile stress induces anisotropy with the hard axis along the direction of stress. In the perfectly ordered state K=3.1 × 106 erg/cm3 in 20 kOe field. 4πI is 7.4 kG and 4.7 kG is 23 kOe along the easy and hard axes respectively. X-ray diffraction indicates a kind of fibre structure with <001> axes of the ordered tetragonal lattices oriented more to the compressive stress direction than to the cross directions.

Electronographic Investigation of Diffusion in Thin Gold-Palladium Films

b. t. boiko, l. s. palatnik and m. v. lebedeva, Fiz. Metall. Metalloved., 1968, 25, (5), 845–848

Diffusion coefficients of vacuum-deposited 100–150 Å films of 0−50 at.% Au-Pd annealed at 400−600°C are given by D=1.2 × 10−5exp (−11,000/RT) cm2/sec and are unrelated to solid solution concentration. D tends to decrease as annealing time increases.

The Electrical Resistivity of Palladium-Hydrogen and Palladium-Deuterium Alloys between 4 and 300°K

n. s. ho and f. d. manchester, Can. J. Phys., 1968, 46, (11), 1341–1345

Electrical resistivity measurements at 4−300°K, and 0−0.62 H/Pd, showed that an anomaly exists in the resistivity of Pd-D as well as that in Pd-H.

The Reaction of Hydrogen with Palladium-Nickel Alloys

a. a. rodina, m. a. gurevich, n. i. doronicheva and l. v. mel’nikova, Zh. fiz. Khim., 1968, 42, (4), 977–981

Studies of 2−50 wt.% Ni-Pd alloys at 300−500°C showed that at a pressure difference of 1 atm there is no significant decrease of permeability for H2 up to 5.5 wt.% Ni but that there is above this Ni content. 2 and 3.5 wt.% Ni-Pd have poor stability in H2 for 20−500°C heating-cooling cycles. No second phase was formed although the microstructure altered. 5−50 wt.% Ni-Pd are stable in H2, even after 3000 temperature cycles. No second phase was formed in 5−8 wt.% Ni-Pd alloys and the microstructure remained unaltered.

The System Ag2Te-Pd

i. i. chernyaev, n. n. zheligovskaya, m. k. borisenkova and n. a. subbotina, Zh. neorg. Khim., 1968, 13, (6), 1620–1625

X-ray and thermographic studies of the Ag2Te-Pd system enabled its composition diagram to be built up as far as 1000°C and indicated the existence of a quasibinary layer at the boundary of Ag2Te and Pd. (Ag Pd)2 Te is stable below 425°C and possesses a PbFCl-type tetragonal lattice with a=6.24, c=11.56Å.

Thermal Expansion of Iridium from 4.2° to 300°K

h. f. schaake, J. less-common Metals, 1968, 15, (1), 103–105

The coefficient of linear thermal expansion of Ir in this range, determined from lattice parameter measurements by X-ray diffraction, is reported for 13 temperatures and agrees well with previous data. An empirical equation for the lattice parameter of Ir as a function of temperature at 0−300°K is a(T)=3.8344±0.0004−3.3612×10−6T+1.2265 × 10−7T2−1.7956 × 10−10T3.

Brittle Fracture in Iridium Single Crystals

c. a. brookes, j. h. greenwood and j. l. routbort, J. appl. Phys., 1968, 39, (5), 2391–2395

Scanning electron microscope studies of brittle fracture of Ir showed that, except where macroscopic imperfections occur, cracks can be nucleated only after extensive work-hardening. Plastic relaxation of the crack is inhibited because impurities substantially increase the critical resolved shear stress. Thus brittle fracture in Ir is caused mainly by impurities.

Reactions of Uranium with the Platinide Elements. I. The Uranium-Ruthenium System

j. j. park, J. Res. NBS, Sect. A, Phys. Chem., 1968, 72A, (1), 1–10

Thermal analysis, metallography and X-ray diffraction revealed five intermetallic compounds: U2Ru, formed peritectically at ≍937°C; “URu,” melting congruently at ≍1158°C; U3Ru4, formed peritectically at ≍1163°C; U3Ru5, formed peritectically at ≍1182°C; URu3, formed peritectically at ≍1850°C. “URu” undergoes solid-state transition at ≍795°C. Eutectics occur at ≍886°C, 18.5 at.% Ru and ≍1148°C, 49 at.% Ru. Maximum solid solubilities are ≍7.5 at.% Ru in U, and ≍1.3 at.% U in Ru. Ru lowers the γ-U transformation to ≍691°C, and the β -U transformation to ≍625°C.

II. The Uranium-Rhodium System

Ibid., 11–17

Similar studies revealed four intermetallic compounds: U4Rh3, formed peritectically at ≍1155°C with a solid state transformation at ≍720°C; U3Rh4, formed peritectically at ≍1450°C; U3Rh5, formed peritectically at ≍1550°C; URh3, melting congruently at ≍1700°C. Eutectics occur at ≍865°C, 24.5 at.% Rh and ≍1393°C, 87 at.% Rh. Maximum solid solubility of Rh in U is ≍8 at.%, and of U in Rh is ≍3 at.%.

III. The Uranium-Iridium System

j. j. park and l. r. muller, Ibid., 19–25

Similar studies revealed five intermetallic compounds: U3Ir formed peritectically at ≍945°C and decomposing eutectoidally at ≍758°C; U3Ir2, formed peritectically at ≍1121°C; UIr, melting congruently at ≍1470°C; UIr2, formed peritectically above 1850°C; UIr3 with congruent m.p. above 1950°C. U3Ir2 has a solid state transition at ≍898°C. Eutectics occur at ≍914°C, ≍15 at.% Ir; at ≍1450°C between UIr and UIr2; at ≍1950°C between UIr3 and Ir. Solid solubility of Ir in γ-U is ≍5.5 at.%, of U in Ir is <3 at.%. Ir reduces the γ-β U transformation to ≍681°C, and the β -γ transformation to ≍565°C.

Activities in Solid Iridium-Iron and Rhodium-Iron Alloys at 1200°C

k. schwerdtfeger and l. zwell, Trans. Metall. Soc. AIME, 1968, 242, (4), 631–633

The equilibria between Ir-Fe or Rh-Fe, Fe oxide (wüstite or magnetite), CO2 and CO at 1200°C were studied by X-ray and thermodynamic analysis. Lattice parameters and activities are presented.

The Effect of Ruthenium, Rhodium and Palladium on the Heat of Expansion of Iron-Nickel and Iron-Nickel-Cobalt Alloys

n. a. solov’eva, m. i. yudkevich, i. i. pasternak and v. z. pogosov, Metalloved. Term. Obrabot. Metal., 1968, (4), 45–46

Additions of Ru or Rh to Fe-Ni and to Fe-Ni-Co alloys raised their coefficients of thermal expansion but had no effect on their Curie points. Additions of 5% or 20% Pd to Fe-Ni-Co at the expense of Fe and Ni raised both factors but the more intensive rise occurred for the coefficient of thermal expansion, which rose 5.0 × 10−6 deg−1 at 20−700°C.

CHEMICAL COMPOUNDS

Complex Sulphates of the Platinum Metals

s. i. ginzburg and n. n. chalisova, Zh. neorg. Khim., 1968, 13, (5), 1239–1244

A review of the electrochemical and other properties of the Pt metal sulphates. (46 references.)

High Pressure Synthesis of Pyrochlore-type Oxides of Tetravalent Platinum

h. r. hoekstra, s. siegel and f. gallagher, Abstr. Papers, 155th Mtg, Am. Chem. Soc., 1968, (Mar.), M76

Fifteen A2IIIPtIV2O7 pyrochlore oxides, where A = Sc,In,Y, or rare earth, synthesised from binary oxides at 30–50 kbar, 100−1500°C, possess cell parameters 9.85−10.42Å and are stable to ≍1000°C at ambient pressure.

Synthesis and Properties of Two New Members of the Rutile Family RhO2 and PtO2

r. d. shannon, Solid state Commun., 1968, 6, (3), 139–143

A tetragonal rutile form of RhO2 and an orthorhombic distorted form of PtO2 were made from commercial oxides at 700°C, 3000 atm. These compounds have room-temperature resistivities <10−4 ohm cm respectively and ionic radii r(Pt4+)=0.63Å and r(Rh4+)=0.62Å. Both are thermally unstable.

Phase Relations between Palladium Oxide and the Rare Earth Sesquioxides in Air

c. l. mcdaniel and s. j. schneider, J. Res. NBS, Sect. A, Phys. Chem., 1968, 72A, (1), 27–37

Equilibrium phase relations were determined in air between PdO and each of La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Y2O3, Er2O3, Tm2O3, Yb2O3, and Lu2O3.

The Ruthenium Dioxide-Oxygen-Ruthenium Tetroxide Equilibrium

b. d. penman and r. r. hammar, USAEC Rept IN-1013, 1968, (Jan.), 7 pp

Partial pressure of RuO4 over RuO2 as a function of at 453−723°C enabled new values of H°f,298, F°f,298 and Cp for oxides of Ru to be recommended. It is suggested that during calcining of nuclear waste there is volatilisation of Ru as RuO4 and also as either nonequilibrium concentrations of RuO4(g), very fine particles, or as another Ru vapour species.

The Oxidising Properties of the Third Transition Series Hexafluorides and Related Compounds

n. bartlett, Angew. Chem. internat. Ed. En., 1968, 7, (6), 433–439

Electron affinity E increases regularly by 20 kcal/mole for each unit increase in atomic number over the series WF6 < ReF6 < OsF6 < IrF6 < PtF6, while affinity for F decreases. PtF6, (E> − 156 kcal/mole), oxidises O2 and Xe. IrF6 is more effective in oxidative fluorination of ONF to ONF3.

ELECTROCHEMISTRY

Mechanism of Electrolytic Perchlorate Production

m. p. grotheer and e. h. cook, Electrochem. Technol., 1968, 6, (5–6), 221–224

Smooth bright Pt is the most efficient anode for the electrochemical oxidation of NaClO3. The effects of current density, NaClO3 concentration and anode polarisation on perchlorate production are analysed and a mechanism is suggested whereby d(ClO4)/dt, the rate of production, is equal to K3(ClO3)i, where K3 is proportional to the true current density and (ClO3)i is the concentration of chlorate ion at the anode surface.

Electrochemical Determination of the Specific Surface and the Activity of Porous Platinum

h. binder, a. köhling, k. metzelthin, g. sandstede and m.-l. schrecker, Chem.-Ing.-Tech., 1968, 40, (12), 586–591

The specific surface area of Rancy Pt depends on Al content and decreases with use. Results were obtained from measurements of cathodic adsorption and anodic desorption of H atoms by potentiostatic sweep methods and were compared with those obtained from BET surface area measurements.

The Effect of Surface-active Cations on the Catalytic Activity and Selectivity of Pt Black

f. m. toktabaeva, g. d. zakumbaeva and d. v. sokol’skii, Kinet. Kataliz, 1968, 9, (3), 690–692

Studies at 20 and 30°C showed that increasing concentrations of the surface-active cations Cd, Zn, Pb, Sn, In, Tl, Mn, and Re decreased the rate of hydrogenation of propargyl alcohol on Pt black. A decrease in selectivity for the hydrogenation of triple bonds was connected with the changed mechanism due to certain adsorbed cations suppressing atomisation of H2. Activation of H2 was mainly by formation of Pt-H2 dipoles, it was assumed.

On the Activity of Platinum Catalysts in Solution. III. Facets on Flame-formed Platinum Spheres

t. b. warner, J. Electrochem. Soc., 1968, 112, (6), 615–616

Pt beads melted with an oxyhydrogen flame and cooled slowly develop flat regions corresponding to {111} and {100} crystal faces, which increase catalytic activity.

Surface Oxidation and Reduction of Platinum Electrodes: Coverage, Kinetic and Hysteresis Studies

d. gilroy and b. e. conway, Can. J. Chem., 1968, 46, (6), 875–890

Polarisation and hysteresis effects were used to study the nature and extent of surface oxidation on three sorts of Pt surface. The quantity of reducible oxide depends on potential and time of anodic polarisation. Galvanostatic and potential sweep techniques were compared.

Adsorption and Oxidation of Carbon Monoxide on Platinised Platinum Electrodes

m. w. breiter, J. phys. Chem., 1968, 72, (4), 1305–1313

Anodic oxidation mechanisms of the two types of CO adsorbed on platinised Pt at open circuit are discussed. Saturation coverage of H atoms decreases linearly with CO coverage and the H-adsorption isotherms change.

Interactions of Adsorbed Organic Layers with Hydrogen Atoms on Platinum Electrodes

s. b. brummer and k. cahill, US Rept AD 663, 903, 1968, (Jan.), 28 pp

Studies in 1 M H2SO4 at 40°C of H atom coverage of smooth Pt foils indicate that the presence of CO leads to repulsive H-CO interaction at all potentials in terms of sites occupied and at >0.15 V versus R.H.E. Interaction of H-CO2 is repulsive above 0.20 V but attractive below 0.20 V. Results are discussed. The cathodic method of H-atom charging for estimating organic coverage on Pt seems least suspect. Interactions with H on Pt show that the species COads and “reduced CO2” are different.

On the Activity of Platinum Catalysts in Solution. Part I. Effects of Thermal Treatment and Chemical Etching on the Pt-O/Hydrogen Specific Reaction Rate

t. b. warner, s. schuldiner and b. j. piersma, US Rept AD 664,490, NRL Rept 6622, 1967, (Dec.), 11 pp

This reaction is very sensitive to pretreatment of the Pt and is a responsive test for cleanliness of electrode and electrolyte. H was present in electrochemically clean 1 M H2SO4 and in the derma of the Pt. Reaction of H with Pt-O on Pt beads was usually faster where their heating to m.p. had been more uniform and their re-crystallisation on cooling had been slower. The specific rate of chemical reaction of chemisorbed O2 with H was lower on Pt wires than on Pt beads, due to differences of crystallite size and drawing defects, but results on both were variable.

Oxygen Overvoltage on Bright Rhodium

j. p. hoare, Electrochim. Acta, 1968, 13, (3), 417–428

Anodic evolution and cathodic reduction of O2 on bright Rh electrodes were studied galvano-statically and by potentiometry. O2 is absorbed above 1400°C to give Rh2O3, which produces a higher overvoltage than do Pt electrodes. Rh has a poor surface for decomposition of H2O2.

Oxygen Overvoltage on Bright Iridium

j. p. hoare, J. electroanal. Chem. interfac. Electrochem., 1968, 18, (3), 251–259

Galvanostatic and potentiostatic studies of bright Ir bead electrodes in O2-saturated H2SO4 indicated that the O2-reduction mechanisms on Ir and Pt cathodes are similar. Although IrO2 is formed, the O2-evolution mechanism is that of H2O-discharge. The adsorbed O2 layers on Ir are believed to be good electronic conductors. Adsorbed O2 on Ir cathodes hinders reduction of O2 to H2O2 but promotes reduction of H2O2 to H2. Intermediate H2O2, which is stable, forms during the O2-reduction process.

Electrooxidation of Methanol on Pt+Ru and Ru Electrodes at Various Temperatures

v. s. entina and o. a. petrii, Elektrokhimiya, 1968, 4, (6), 678–681

Stationary polarisation curves were obtained for the electrooxidation of CH3OH on Ru, platinised Pt, 10 and 25% Pt-Ru, and 10, 25 and 40% Ru-Pt electrodes in 2N H2SO4+2M CH3OH at various fixed temperatures. Products were analysed for HCHO, HCOOH and CO2.

ELECTRODEPOSITION AND SURFACE COATINGS

High-speed Hard Chromium Plating. Part I. Etch-free Plating

r. d. bedi, Plating, 1968, 55, (3), 238–246

Etching frequently occurs while hard Cr plating steel or steel alloys from fluoride-catalysed baths at unprotected low current density areas, thus contaminating the bath. It is due to homogeneous electrochemical corrosion, depending on the passivating properties of the electrolyte, the degree of cathodic activation of the passive film, and the stability of the complex formed between passive film cations and solution anions. An immersion deposit of Pt or another Pt metal inhibits cathodic reduction of the passive film, so protecting recessed areas from etching, and increasing the range of hard Cr plating by giving high-speed, smoother harder deposits.

Part II. A New Stop-off Procedure

Ibid., 246–249

The surface to be stopped off is coated with an immersion deposit of a low H2 overvoltage noble metal such as Pt or Pd. This procedure prevents plating where not desired and yet gives uniform hard Cr deposits with smooth, rounded edges, which can be put in service with no further finishing.

Platinised Titanium Anodes Permit Plating of “Unplatable” Parts

e. jolliff, Plating, 1968, 55, (5), 508

Auxiliary anodes of Pt/Ti enabled awkward angles of wheel covers to be Ni- and Cr-plated. Their life is more than 100 times that of a similar design in Ni.

Electrodeposition of Ductile Palladium

j. m. stevens, Trans. Inst. Metal Finish., 1968, 46, (1), 26–31

An electrolyte based on [Pd(NH3)4]Br2 can be used under a range of conditions to provide Pd coatings with up to 20% ductility. Under the preferred conditions for vat plating the cathode efficiency is >90% and the rate of deposition is 1μ/min. Regeneration of the electrolyte is simple and incorporates purification. Impurity effects and wear characteristics are studied.

The Corrosion Resistance of Electroplated Rhodium Deposits on Nickel

k.-e. becker, h. schlegel and a. kubat, Metalloberfläche, 1968, 22, (5), 145–153

Measurements of corrosion current density and of current density-potential curves for Ni and Rh show that contact corrosion in the pores of electroplated Rh deposits on Ni is determined by reactions on the Rh. Corrosion is accelerated at low pH but is still detectable at pH9. This indicates that the standard Rh electrodeposit on Ni may not stand up to such severe conditions as are met with in the food industry.

LABORATORY APPARATUS AND TECHNIQUE

Initial Field Evaporation of Platinum Surfaces in the Field Ion Microscope

c. a. speicher and w. t. pimbley, Surface Sci., 1968, 10, (3), 470–473

Two methods of obtaining atomically smooth Pt tip surfaces are described. Rough surfaces resulting from etching may be treated by field evaporation at 78°K or by field evaporation at 10°K while stress cycling the tip.

Versatile and Rapid Trace Nitrogen Analysis of Petroleum Materials by Microcoulometry

d. r. rhodes, j. r. hopkins and j. c. guffy, Abstr. Papers, 155th Mtg, Am. Chem. Soc., 1968, (Mar.), R37

10 to 20 times the sensitivity of the Dohrmann N2 analyser was obtained by modifications, including the use of Pd instead of Pt pH-sensing electrodes. The range was extended to 0.1±0.02 ppm, 600°C with ±5% reproducibility.

Production of Ruthenium Targets [Foils] for Nuclear Research and a Study of Ruthenium, Rhodium, and Palladium Deposits

c. n. medyanik and l. i. kadaner, Ukr. fiz. Zh., 1968, 13, (1), 127–129

Electrolytic production of ≥3μ Ru foils is described. The dependence of the internal stress of Ru, Rh and Pd foils on electrolyte concentration and current density was studied.

BRAZING

Joining Dissimilar Metals by Gas Tungsten-Arc Braze-Welding

d. e. solomon, Welding J., 1968, 47, (3), 181–191

Brazing alloys for the tungsten arc technique of joining dissimilar metals were evaluated by tests on welding an annular disc around a pipe. The eutectic alloys Pd-Au, m.p. 1190°C and Pd-Co, m.p. 1220°C were used successfully in a number of cases, e.g. Pd-Au: discs of carbon steel to stainless steel pipe, Ni-Fe-Co alloy to stainless steel, stainless steel to carbon steel, Mo, Ni-Fe-Co, and W; Pd-Co: discs of carbon steel to carbon steel and Ni-Fe-Co pipes, Ni-Fe-Co to carbon steel and Ni-Fe-Co, stainless steel to Mo, stainless steel and W.

HETEROGENEOUS CATALYSTS

Atomisation of Oxygen on Platinum

j. fusy, b. weber, a. cassuto and p. le goff, J. Chim. phys., 1968, 65, (6), 1192–1193

Studies of O2 atomisation between 10−9 and 10−4 torr on Pt at 1370−1640°K show that the reaction is first order at low pressures with the probability of atomisation of a molecule during one collision at 0.12±0.015. As the pressure rises the reaction becomes half order with frequency factor ≍1025.

Hydroisomerisation of n -Paraffins over Fluorided Platinum on Alumina Catalysts

b. a. orkin, Abstr. Papers, 155th Mtg, Am. Chem. Soc., 1968, (Mar.), R57

Selectivity of Pt/Al2O3 catalyst with 5% fluoride for isoparaffin formation from C11−C14 n -paraffins was greater than with 10% fluoride or no fluoride at 300 psig H2. Effects of , type of Al2O3, S compounds, N compounds, and aromatic compounds were studied. Reduced from 1000 to 50 psig increased isomerisation from 37 to 88%.

Dehydrocyclisation of 2-n -Butylnaphthalene on Alumina-Platinum Catalyst

l. a. erivanskaya, g. a. shevtsova, n. l. komissarova and a. f. plate, Neftekhimiya, 1968, 8, (2), 192–197

Studies of the effects of temperature, volume rate, test duration and concentration of Pt in Pt/Al2O3 catalyst during C6-dehydrocyclisation of 2-n -butylnaphthalcne showed that the phenanthrene: anthracene product ratio depends on the reaction temperature. The reaction is accompanied by cracking, by isomerisation and by dehydrogenation of alkyl groups. The chief mechanism leading to the predominant formation of phenanthrene at 400−510°C is the intermediate formation of 2-(buten-1-yl)naphthalene.

The Surface Transport of Various Gases on a Platinum-Alumina Catalyst

d. gelbin, Chem. engng Sci., 1968, 23, (1), 41–49

Permeation measurements of the surface transport rates of C3H8, n -C4H10, n -C6H14 and Kr in a Pt/Al2O3 pellet showed that surface transport of hydrocarbons is related to the dissociative adsorption of the migrating gas. Surface mobility decreases with increasing molecular length. Activation energies, which increase from C3H8 to C5H12, are rather larger than the corresponding heats of adsorption. The behaviour of Kr is different and a mechanism for it is proposed.

On the Role of C5-Dehydrocyclisation in the Aromatisation of n -Paraffins in the Presence of Platinum on Alumina Catalysts

yu. v. fomichev, i. v. gostunskaya and b. a. kazanskii, Izv. Akad. Nauk SSSR, Ser. Khim., 1968, (5), 1112–1117

Microreactor studies of the aromatisation of n -C6H14 and of n -C7H16 over 0.6% Pt/Al2O3 at 450−540°C, 1 atm H2 indicated a C5-dehydrocyclisation mechanism involving alkylcyclopentane intermediates, the hydrogenation of which is accompanied by dehydrogenation with some isomerisation to the aromatic compound.

C5- and C6-Dehydrocyclisation of n -Paraffins in the Presence of a Platinum on Alumina Catalyst

Ibid., Dokl. Akad. Nauk SSSR, 1968, 180, (2), 383–385

Tests at 450−540°C over Pt/γ-Al2O3 showed that aromatisation of n -hexane and n -heptane can proceed via C6-dehydrocyclisation with subsequent dehydrogenation in which all the cyclo-hexane and methylcyclohexane are converted to the respective aromatic compounds, as well as by C5-dehydocyclisation with subsequent dehydroisomerisation.

Competitive Hydrogenations on Platinum

a. s. hussey, r. h. baker and g. w. keulks, J. Catalysis, 1968, 10, (3), 258–265

Results of competitive hydrogenations of 14 pair combinations of 10 cycloalkenes from solution in cycloalkane solvents on 0.52% Pt/Al2O3 at 25°C, 1 atm agreed with both equilibrium and rate-controlled chemisorption models, the latter being preferred. Stereochemical and product ratio problems are discussed and factors affecting chemisorption of cycloalkenes on Pt surfaces are considered.

Catalytic Dehydrogenation of Cyclohexane: a Transport-controlled Model

r. r. graham, f. c. vidaurri and a. j. gully, AIChE J., 1968, 14, (3), 473–479

Kinetics of the dehydrogenation of cyclohexane with excess H2 over Pt/Al2O3 at 400−500°C, 21–41 atm and at Reynold’s numbers 20–65 indicate a rapid overall reaction influenced by external concentration, temperature gradient and reverse reaction.

The State of Platinum in Promoted Platinum Catalysts and the Nature of the Activity of Metallic Catalysts in the Dehydrocyclisation of Paraffin Hydrocarbons

n. r. bursian, s. b. kogan and z. a. davydova, Kinet. Kataliz, 1968, 9, (3), 661–667

Additions of Li, Na and Cs to Pt/Al2O3 and Pt/SiO2 promote the catalysts by stabilising the active centres containing Pt ions both in air and H2. A suggested model contains complex active centres incorporating Pt4+ ions. Its action during dehydrocyclisation of paraffins is discussed.

Hydrogenation of Ethylene on Platinised Silica Gel

i. nicolau, Rev. roumaine Chim., 1968, 13, (1), 71–75

The rate of hydrogenation of C2H4 on 0.1% Pt/SiO2 at 30−90°C, 1 atm is dependent on H2 concentration but is independent of C2H4 concentration. An apparent activation energy of 4.2 kcal/mole is reported.

Kinetics of Isomerisation of Cyclohexane on Pt Zeolite Catalyst in a Gradientless System under Pressure of Hydrogen

u. m. kurkchi, v. i. garanin and kh. m. minachev, Kinet. Kataliz, 1968, 9, (3), 571–576

The rate of isomerisation of C6H12 on a Pt zeolite catalyst was studied in relation to the size of the catalyst granules, the rate of circulation of the gas mixture, and the temperature and partial pressure of C6H12 and H2. At 288−318°C, as increases, the order of the reaction with respect to C6H12 changed from first to zero order. Increasing retards the reaction. Apparent activation energy was 32 kcal/mole.

Dehydrocyclisation of n -Hexane on Palladised Tape

v. m. gryaznov, k. maldonado, e. khazhzhar and d.-k. oluoch okeio, Kinet. Kataliz, 1968, 9, (2), 435–437

Mass-spectrometric studies of n -C6H14 vapour conversion on palladised tape at ≍10−6 mm Hg indicated slight dehydrocyclisation at 20°C, intensifying with increased temperature. At 200°C there is almost complete conversion into C6H6.

Palladium Areas in Supported Catalysts. Determination of Palladium Surface Areas in Supported Catalysts by Means of Hydrogen Chemisorption

p. c. aben, J. Catalysis, 1968, 10, (3), 224–229

Hydrogen chemisorption proved suitable for determination of Pd surface areas in Pd/Al2O3 and Pd/SiO2 when the chemisorption conditions were chosen carefully. It was also suitable for particle size determination in cases where interference by the support caused other methods to fail. Combined surface area and H2 chemisorption measurements on Pd black showed that 1 H atom was adsorbed on each exposed Pd atom, as confirmed by electron microscopy.

Heterogeneous Catalysis by Metal Chelates — Isomerisation of Butenes

m. misono, y. saito and y. yoneda, Ibid., (2), 200–202

[Pd(acac)2] mounted on silica gel is an efficient catalyst for isomerisation of C4H8. Rate constant at 61.5°C for cis -2-C4H8 isomerisation was 4.3 × 10−3g−1min−1, far higher than with Ni or Pt as the central metal ion and also far higher than with dmg as chelate.

On the Mechanism of 1-Butene Isomerisation on Supported Palladium

s. carra and v. ragaini, Ibid., (3), 230–237

Studies of double-bond migration of 1-butene on 0.484% Pd/Al2O3 in the absence of H2 indicated stereoselectivity towards cis -2-butene. Kinetic studies by both integral and differential reactor techniques at 160−240°C suggested two mechanisms for isomerisation: the former with two atomic centres and stereospecific towards cis isomer; the latter tending towards equilibrium of trans- and cis -2-butene.

The Hydroisomerisation of n -Butenes. 1. The Reaction of 1-Butene over Alumina- and Silica-supported Rhodium Catalysts

j. i. macnab and g. webb, J. Catalysis, 1968, 10, (1), 19–26

Studies of the reaction of 1-C4H8 with H2 over 5%Rh/Al2O3 or 5%Rh/SiO2 at −20 to +80°C gave the kinetics and apparent activation energies for hydrogenation and isomerisation. The initial cis: trans ratio in 2-C4H8 is greater than the thermodynamic equilibrium value but it decreases with increasing temperature. The support has little effect. A suggested isomerisation mechanism is via a 1-methyl-π-allyl intermediate.

Catalytic Activity of Rhodium and Ruthenium in the Hydrogenolysis of Ethane

g. k. starostenko, t. a. slovokhotova, a. a. balandin and k. a. el khattib, Vest. Moskov. Univ., Ser. II, Khim., 1968, (2), 52–55

Activities of Rh/SiO2 for hydrogenolysis of C2H6 were measured at 155−190°C and activation energies were calculated for various H2/C2H6 mixtures.

Modification of Raney Catalysts by Addition of Transition Metals. VIII. Electrooxidation of Hydrogen and Catalytic Hydrogenation on Raney Nickel-Ruthenium Alloys

a. b. fasman, a. isabekov and b. k. almashev, Zh. fiz. Khim., 1968, 42, (4), 903–908

Studies of the effect of the composition of Raney Ni-Ru catalysts on the kinetics of hydrogenations of potassium maleate, o -nitrophenol, and α-naphthoquinone, and of anodic oxidations of H2 and alkaline electrolytes showed that new phases were formed in the initial Ni-Ru-Al alloys and that the Ru addition leads to growth of the crystal lattice parameters of Raney Ni.

Structures of Olefins and their Simultaneous Hydrogenation on Ru Catalyst

l.kh. freidlin, e. f. litvin and s. k. tilyaev, Neftekhimiya, 1968, 8, (2), 155–161

Studies with 5% Ru/C show that it possesses high selectivity during simultaneous hydrogenation of olefins with various structures. The H2 is added in positions depending on the alkyl groups to be substituted, the structures and the position of the double bonds.

Stereoisomeric Conversion of Individual cis - and trans -3-Methylpentene-2 in the Presence of Group VIII Metals

m. abubaker, z. s. khrustova, i. v. gostunskaya and b. a. kazanskii, Vest. Moskov. Univ., Ser. II, Khim., 1968, (2), 148–152

The activity and selectivity of C-supported catalysts for cis-, trans -isomerisation of cis- and trans -3-methylpentene-2 are in the order Pd>Rh>Ru>Os>Ir>Pt.

Catalytic Hydrogenation of Methylacetylene over Group VIII Metals

r. s. mann and s. c. naik, Indian J. Technol., 1968, 6, (2), 57–58

Studies of the reaction between methylacetylene and H2 over pumice-supported catalysts in a static system showed that the initial rates of reaction depended only on the initial , except for Pt/pumice where the pressure of methylacetylene was also important. Apparent activation energies for pumice-supported Fe, Co, Ni, Rh, Pd, Ir, and Pt were 14, 13.3, 16.8, 8.6, 10.3, 9.2, and 12.9 kcal/mole respectively and the activities were in order Pt>Pd>Ni>Ir>Rh>Co>Fe>Ru, Os.

Consecutive Hydrogenation of Double Bonds of Cycloheptatriene over Palladium, Platinum and Rhodium Catalysts

b. d. polkovnikov, o. m. nefedov, e. p. mikos and n. n. novitskaya, Izv. Akad. Nauk SSSR, Ser. Khim., 1968, (6), 1240–1245

Hydrogenation of conjugated double bonds of cycloheptatriene-1,3,5 proceeded consecutively on borided Pd catalyst, with less selectivity on borided Rh, and with no selectivity on borided Pt. Consecutive hydrogenation of unsaturated bonds of cycloheptadiene-1,3 also occurred on borided Pd catalyst.

HOMOGENEOUS CATALYSIS

Organic Syntheses by Means of Noble Metal Compounds. XXXVI. Reactions of Carbanions with Cyclooctadienepalladium and -platinum Halide Complexes and Tetraphenylcyclobutadienepalladium Chloride Complex

h. takahashi and j. tsuji, J. Am. Chem. Soc., 1968, 90, (9), 2387–2392

Studies of C-C bonding by the reaction of dienepalladium and -platinum halide complexes with carbanions showed that malonate and acetoacetate react smoothly at room temperature with cyclooctadienepalladium and -platinum complexes to give new complexes with σ and π bonds with metals. Reaction of these with methylsulphinyl carbanion produced bicyclo[6.1.0]-nonene derivatives. Malonate attacked the complexes to give 2,6-disubstituted bicyclo[3.3.0]-octane rings.

Palladium-catalysed Reactions of Unsaturated Compounds in Non-aqueous Solvents

c. f. kohll and r. van helden, Rec. Trav. chim. Pays-bas, 1968, 87, (5), 481–500

The formation of vinyl acetate is first order in catalyst and in acetate concentration. Acetate is thought to displace chloride via a π-olefin-Pd(II) complex. Effects of chloride ion, solvent and various transition metal salts are discussed.

Polymerisation of Allene with a Soluble Palladium Catalyst

g. d. shier, Abstr. Papers, 155th Mtg, Am. Chem. Soc., 1968, (Mar.), T25

1:1 mole ratio of Pd(NO3)2: triarylphosphine in glacial CH3COOH catalysed head-to-head polymerisation of allene. Chemical and spectral tests indicated that the polymer contained repeating conjugated diene units.

The Dimerisation of Butadiene by Palladium Complex Catalysts

s. takahashi, t. shibano and n. hagihara, Bull. Chem. Soc. Japan, 1968, 41, (2), 454–460

Pd(Ph3P)2(C4H2O3) catalysed linear dimerisation of butadiene to form 1,3,7-octatriene in aprotic solvents and 1-alkoxy-2,7-octadiene and/or 1,3,7-octatriene in alcohols, depending on the nature of the solvent. Dimerisation in C6H5OH, CH3COOH or amines produced solvent-dimer adducts.

Carbonylation of Olefins under Mild Temperature Conditions in the Presence of Palladium Complexes

k. bittler, n. von kutepow, d. neubauer and h. reis, Angew. Chem. internat. Ed. En., 1968, 7, (5), 329–335

LmPdXn complexes, (where L is a ligand such as phosphine, nitrile, amine, or olefin; where X is acid; where m+n=3 or 4) are efficient catalysts for both ester and acid production below 100°C. Polyunsaturated olefins were carbonylated selectively.

Transition Metal Catalysis Exemplified by Some Rhodium-promoted Reactions of Olefins

r. cramer, Accounts chem. Res., 1968, 1, (6), 186–191

The Rh ion catalysed syntheses C2H4→C4H8, C2H4 + C4H8 → 1,4-C6H10, 1-C4H8 → isomeric linear C4H8, and the effect of thermodynamic or kinetic control on the products are discussed. Coordination of Rh with the reactant molecules causes orientation and reduces energy barriers to the reaction.

Dimerisation of Acrylonitrile by Ruthenium Chloride

a. misono, y. uchida, m. hidai, h. shinohara and y. watanabe, Bull. Chem. Soc. Japan, 1968, 41, (2), 396–401

RuCl3.3H2O under H2 atmosphere catalysed the formation of cis - and trans -1,4-dicyano-1-butene by end-to-end coupling of acrylonitrile. Effects of temperature, and addition of various salts were considered.

Patterns of Organometallic Reactions Related to Homogeneous Catalysis

j. p. collman, Accounts chem. Res., 1968, 1, (5), 136–143

A review of reaction patterns involved in homogeneous catalysis by transition metal complexes, including those of Ru, Ir, Rh, and Pt.

FUEL CELLS

Activation of Nickel Fuel Electrodes with Platinum Catalysts

d. m. drazic, a. r. despic and n. d. koselj, Electrochem. Technol., 1968, 6, (3–4), 98–100

The activity of porous Ni fuel cell electrodes, activated by chemical plating with a solution of H2PtCl6, Pb(CH3COO)2 and NaCl, depended on the concentrations of Pt and of the neutral salt, on the flow rate of the solution through the electrode, and on the amount of Pt deposited. With 1 mg Pt/cm2, 100 mA/cm2 the best H2 electrodes had overpotential 65mV. It appears from Pt distribution measurements that, whatever the overall electrode thickness, the active layer is 0.3 mm.

Electrocatalysts for Hydrogen/Carbon Monoxide Fuel Cell Anodes. III. The Behaviour of Supported Binary Noble Metals

d. w. mckee and a. j. scarpellino, Electrochem. Technol., 1968, 6, (3–4), 101–105

Practical CO-tolerant anode electrocatalysts were prepared from Pt and Ru on inert substrates such as B4C. Catalyst activity depends strongly on the preparation and composition of the metal phase. Using reformer gas as fuel with up to 10%CO at 85°C, satisfactory results were obtained with as little as 3 mg/cm2 metal in 5N H2SO4. The high performance of Rh-Pt or of Ir-Pt blacks is largely lost when these are supported, perhaps because the mechanism of anodic oxidation is different.

CATHODIC PROTECTION

Internal Cathodic Protection of Salt Water Pipelines with the Aid of Platinised Titanium Anodes

j. w. kühn von burgsdorff, Werkstoffe Korrosion, 1968, 19, (6), 473–478

Continuous partly platinised Ti wire anodes were used to protect long pipelines. A current density of ≍150mA/m2 was required but could be reduced considerably by coating the pipeline with a passive protective coating.

CHEMICAL TECHNOLOGY

Electrolysed Seawater Plays Big Role in Sewage Disposal Method

r. eales, Chem. Engng, 1968, 75, (13, June 17), 172–174

Vertical electrolytic cells for the purification of sewage by electrolysis with sea water have platinised Ti anodes and plain steel cathodes. The cells operate at 6 V dc. CJB have constructed one plant on Guernsey and another is under construction at Capenhurst in Cheshire.

TEMPERATURE MEASUREMENT

A Platinum Resistance Thermometer Calibration between 2 and 273.15°K

chan yet-chong and a. m. forrest, J. sci. Instrum., J. Phys. E., 1968, 1, (8), 839–842

Selected Pt resistance thermometers were calibrated approximately at 2−273.15°K using only the b.p. of He, the ice point, and temperatures at 2−4.2°K from He vapour pressure thermometer measurements. Interpolation for 4.2−273.15°K used a table of Z functions and for 2−16°K used a polynomial equation in T against R.

Comparison between Gas Thermometer, Acoustic, and Platinum Resistance Temperature Scales between 2 and 20°K

j. s. rogers, r. j. tainsh, m. s. anderson and c. a. swenson, Metrologia, 1968, 4, (2), 47–59

The NBS Pt resistance thermometer scale of 1955 at 2−16°K was used in determining the resistance versus temperature relation of Ge thermometers to ±3 mdeg against a constant volume gas thermometer.

Temperature Measurements with Metal Ribbon High-temperature X-ray Furnaces

w. ostertag and g. r. fischer, Rev. sci. Instrum., 1968, 39, (6), 888–889

Thin Pt and Rh-Pt thermocouple wires were welded to the Pt ribbon of a high-temperature X-ray diffractometer attachment. The temperature profile of the specimen stage, determined as functions of temperature, heater position and heater shape, showed improved accuracy of temperature measurement.

Protective Devices for Thermocouples Used in Glass-melting Furnaces

v. m. obukhov, Steklo Keram., 1968, 25, (4), 12–14

Four types of protective casings for 6%Rh-Pt: 30% Rh-Pt thermocouples are described. Protection against flame above 1450°C is given by a three-layer cover of corundum, ZrO2 and corundum. Protection against molten glass up to 1200°C may be afforded by corundum, or at temperatures ±1200°C by a three-layer cover of corundum, steel and corundum. Protection against molten glass above 1250°C consists of corundum sheathed with Pt. In each case the thermocouple itself is supported in a twin-bore corundum tube.

Determination of Temperature According to the Thickness of the Clinker Deposit

v. v. puzankov, yu. p. shchukin and m. l. vishnevetskii, Stal’, 1968, (4), 304–305

To eliminate errors of temperature measurement with Rh-Pt thermocouples due to clinker build-up on the sheath a probe has been developed at the Karaganda works which extends telescopically so that the hot junction projects beyond the point of clinker build-up.

Calibration and Stability of Miniature Resistance Thermometers

g. w. lindberg and w. v. johnston, Abstr. Papers, 155th Mtg, Am. Chem. Soc., 1968, (Mar.), V9

Miniature Pt resistance thermometers 0.5 in. long, 0.156 in. diameter, weighing 1 g were calibrated at −182 to +100°C by comparison with capsule-type Pt resistance thermometers and at −262 to −182°C by interpolation data. The resistance at 0°C was reproducible to 10 ppm for six months.

The Accuracies of Calibration and Use of I.P.T.S. Thermocouples

t. p. jones, Metrologia, 1968, 4, (2), 80–83

Uncertainty expressed as 99% confidence limits from precise calibration of Pt: 10% Rh-Pt thermocouples at 630.5−1063°C is ≍±1.0 μV, based on five replicates at each of the three primary calibration points and subsequent accuracy of a calibrated thermocouple with systematic errors eliminated is ±0.2°C.

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