PLATINUM METALS REVIEW · PLATINUM METALS REVIEW ... hydrazine, etc., are not. In addition the...

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their applications in industry

V O L . 2 0 A P R I L 1 9 7 6 NO. 2

Contents

Sulphate Emissions from Automobile Exhaust

Palladium Alloys for Electrical Contacts

Coating Methods for Use with the Platinum Metals

Russian Research on the Platinum Group Metals

Hydrogen in Palladium

Carboxylato Complexes of the Platinum Group Metals

Abstracts

New Patents

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Communications should be addrmsed to The Editor, Pkrtinum M& R&w

Johnson Matthey & Co Limited, Hatton Garden, London EClN 8EE

A hydrogen generator undergoing field trials with the British Army. The balloon which is about to lq t the radiosonde equipment into the atmosphere, has just been injated with pure, dry hydrogen produced on-site. As the generation of hydrogen proceeds the gas is used to 511 the hydrogen storage cylinders in readiness for the next launch

interruption in the availability of hydrogen, it was decided to generate the daily requirements in the field.

Hydrogen Production Several possible methods of producing

hydrogen in a mobile plant were considered including electrolysis, simple chemical reactions and cracking processes. The high electrical power requirements and the heavy equipment involved were disadvantages which ruled out the use of electrolytic processes. Simple chemical processes were discounted because they need bulky supplies of expensive and corrosive chemicals, considerable operator attention is required, and the gas produced is delivered hot, wet and at low pressure.

Of the several cracking processes that were possible the low-temperature steam-methanol reaction, coupled with the use of a diffusion membrane to separate pure hydrogen from the gas mixture produced, appeared to have the most advantages. Methanol/water mixtures are already present in military logistic

Platinum Metal Rev., 1976, 20, (4),

systems while other possible chemical compounds such as ammonia, naphtha, hydrazine, etc., are not. In addition the methanol/water mixture is easily carried in light, thin-walled containers such as jerry cans whereas ammonia needs to be transported in heavy iron cylinders, and hydrazine, though transportable in steel drums, is a corrosive chemical with a toxic and explosive vapour. Economically the methanol/water feedstock is the cheapest of the possible starting materials and it is available internationally at an acceptable standard of purity. The use of naphtha as an alternative feedstock was considered but the possible variations in its chemical composition, and the high cost of the cracking catalyst, made it unacceptable.

The hydrogen generator being developed for the British Army is mounted on a standard one-ton general-service trailer and produces hydrogen at a rate of 4.2 cubic metres per hour (150 cu ft/h) at standard temperature and pressure. This output consumes fuel at a rate of just over a gallon per hour.

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Platinum Metal Rev., 1976, 20, (4), 112

During production the fuel, a I : I molar methanol/water mixture, is pumped through a heat exchanger then into a vaporiser, as shown in the Figure opposite, before entering the catalyst chamber where the methanol is cracked into hydrogen and carbon monoxide. Subsequently steam reacts with the carbon monoxide to produce carbon dioxide and more hydrogen all of which passes into the diffusion module.

Diffusion Module The module consists of a large number of

small diameter thin walled tubes of palladium-silver alloy closely packed in a stainless steel case. The tubes provide a large surface area through which diffusion can take place. The high density packing provides mechanical strength and ensures that the hydrogen in the input gas has every opportunity to diffuse through the membrane, rather than being vented with the unwanted impure gases through a bleed valve to the atmosphere. Furthermore, the arrangement of the tubes is such that the formation of a layer of stagnant impure gas on the surface of the diffusion tubes, which would considerably retard diffusion, is prevented.

The hydrogen which diffuses through the palladium-silver membrane is a cool, pure, dry gas with maximum lifting power. This pure hydrogen can be fed either directly to a balloon filling nozzle or to hydrogen storage containers mounted on the trailer.

A metering device incorporated in the equipment automatically measures the amount of hydrogen necessary to life the balloon and its load to the required height, 20,000 metres, at a specified rate of six metres per second. In addition the device indicates both the volume and the rate of flow of the hydrogen.

Field Trials The generator described has already suc-

cessfully completed most of the extensive trials considered necessary before entering service with the British Army. These have established that the equipment can perform

satisfactorily in arctic and tropical conditions, in driving rain and in dust storms. Further- more it has been shown that towing the equipment over rough roads or through flooded open country does not significantly affect the output performance, in fact the generator is sufficiently rugged to withstand and operate in a military environment regardless of weather conditions. Compatibility trials have established that the function of the equipment will not affect, nor be affected by, the operation of other military equipment in the vicinity.

I t is now expected that the generator will be in service with the British Army towards the end of this year. A considerable interest has been shown in this generator by six of the NATO countries and at the last meeting of the NATO Meteorological Panel it was agreed that the hydrogen generator would be accept- ed by NATO for srandardisation.

Civilian Applications The generator has been built on a modular

principle and both larger and smaller models are being designed to cover a range of outputs of I to 17 cubic metres per hour (35 to 6,000 cu ft/h). Civil applications for small hydrogen generators exist in meteorological stations for weather soundings and also in industry for such purposes as semiconductor manufacture, the heat treatment of metals, in brazing, and for many laboratory applications. The robust construction of the military generator will enable it to form the basis of the design of commercial equipment capable of operating in the open, exposed to all weather conditions, as has now been shown by the performance of the first commercial hydrogen generator supplied which is now operating satisfactody at Halley Bay Base, Antarctica.

References I Platinum Metals Rev., 1962, 6, (2), 47 2 Platinunz Metals Rev., 1964, 8, (3), 91 3 Platinum Metals Rev., 1968, 12, (I), 15 4 G. L. Matlack, Platinum Metals Rev., 1969, 13,

5 P. M. Roberts andD. A. Stiles, Platinum M e t a l s (1),26

Rev., 1969, 13, (413 141


Pol ymet allic Cluster Catalysts SUPERIOR PROPERTIES FOR SPECIFIC APPLICATIONS

By John H. Sinfelt Corporate Research Laboratories, Exxon Research and Engineering Co., Linden, New Jersey

Highly dispersed metallic clusters composed of two or more metals within Group VIII , or Combinations of one or more Group VIII metals with a Group I B metal, when supported on a carrier, form catalysts of considerable theoretical interest which also have practical industrial applications. The simpler bimetallic clusters have provided useful model systems for investigating basic concepts and have demonstrated that their catalytic behaviour can be very different for different types of reactions. The idea of polymetallic clusters could be applicable to a number of combinations of elements, so increasing the range of catalyticalky usefuE systems.

Historically, bimetallic catalysts have been of interest in the development of ideas related to an electronic factor in catalysis by metals (I, 2). The bimetallic catalysts employed in such investigations have typically been alloys in which the metal dispersion or surface area is very low, at least by comparison with the supported platinum reforming catalysts (3, 4) which have long been of great importance in the petroleum industry.

For a bimetallic catalyst to be of interest for industrial applications, it is necessary that the catalyst be prepared in a high surface area form and that it be resistant to loss of surface area during use. Deposition of the components of a bimetallic catalyst on a carrier provides an approach to this problem (5,6). In considering the nature of such a supported bimetallic catalyst, one might ask the following question: Will the atoms of two different metals interact to form a “bimetallic cluster” or will the individual metal components exist as separate entities on the carrier? If two completely miscible metals are co-deposited on a carrier surface, one might expect on purely statistical grounds that the individual metal clusters formed would contain atoms of both metals; that is, it is unlikely that the metal components would be

completely isolated from each other in the form of monometallic clusters containing atoms of only one or the other of the two components. Various combinations of completely miscible metals provide interesting candidates for highly dispersed, supported bimetallic catalyst systems. Surprisingly, perhaps, experience has shown that systems of interest include metallic combinations which do not form alloys in the bulk (5). Consequently, the term “bimetallic clusters” rather than alloys is preferred when referring to highly dispersed supported bimetallic systems where there is evidence of significant interaction between the metallic components. Very highly dispersed bimetallic clusters are composed mainly of surface atoms, and one can obtain compositions not possible in bulk crystals.

The term “polymetallic clusters” is used when referring more generally to clusters containing atoms of two or more metals, and includes bimetallic clusters as a special case. Polymetallic clusters provide great flexibility in the design of metal catalysts. Virtually any property of a metal catalyst, including activity, selectivity, or surface stability, may be in- fluenced by combining it with one or more other metals in the form of polymetallic

Platinum MetalRev., 1976, 20,(4),114-119 114

clusters. The metallic portion of polymetallic cluster catalysts may constitute a very small fraction of the total mass of metal plus carrier, as in the case of catalysts employed in the catalytic reforming of petroleum naphthas for production of high anti-knock quality motor gasolines (3). In such catalysts the metallic portion commonly comprises less than I per cent of the total catalyst mass. Correspondingly, the degree of coverage of the carrier surface by the metal clusters is typically lower than about I per cent in reforming catalysts.

Examples of types of polymetallic clusters of interest include combinations of two or more metals within Group VIII and combinations of one or more Group VIII metals with a Group IB metal. Bimetallic combinations of a Group VIII metal and a Group IB metal provide useful model systems for investigating the basic concept (5) . Reactions such as the hydrogenolysis of ethane to methane and the dehydrogenation of cyclohexane to benzene have been very valuable in probing into the nature of these model bimetallic catalysts. The studies have demonstrated a strong element of catalytic specificity, the Group VIII-Group IB clusters behaving very differently for different types of hydrocarbon reactions. With such information, one is in a position to exert considerable control over the catalytic behaviour of metallic sys tems . Experimental Evidence for Bimetallic Clusters

Direct experimental verification of the existence of highly dispersed bimetallic clusters is complicated by limitations in the ability of physical methods to obtain structural information on highly dispersed systems. For example, conventional X-ray diffraction pro- cedures are unsatisfactory for the investigation of metal crystallites or clusters in the size range of 10 to 20 8. Recently, a method based on the analysis of the fine structure X-ray absorption spectra on the high energy side of an X-ray absorption edge has shown

promise for structural investigations on highly dispersed materials (7). The application of this method, known as EXAFS, to bimetallic clusters is currently being ex- plored @), but no results are yet available. In the absence of information by physical methods, however, chemisorption or a catalytic reaction can serve as a sensitive probe to obtain evidence of interaction between the atoms of the two metallic components in a bimetallic catalyst.

Bimetallic clusters of a Group VIII and a Group IB metal are good model systems for chemisorption and catalytic studies, since the individual components have very different properties. Thus, the Group VIII metals exhibit strong hydrogen chemisorption whereas the Group IB metals do not (9, 10, 11). Similarly, the Group VIII metals exhibit catalytic activities for the hydrogenolysis of alkanes which are many orders of magnitude higher than those of the Group IB metals (12). Incorporation of a Group IB metal with a Group VIII metal in an alloy or bimetallic cluster leads to a marked decrease in the extent of strong hydrogen chemisorption and in the catalytic activity for hydrogenolysis of ethane to methane (5, 11, 12, 13). Interestingly, these effects are observed even for Group VIII-Group IB metal combinations which exhibit very limited miscibility in the bulk (5). Examples of such systems are ruthenium-copper and osmium- copper. Specific catalytic activities of silica supported ruthenium-copper and osmium- copper clusters for the hydrogenolysis of ethane to methane are given in Figure I. The catalysts of Figure I contain I weight per cent of either ruthenium or osmium and varying amounts of copper, the atomic ratio of copper to the Group VIII metal ranging from o to I. The specific activity for ethane hydrogenolysis declines markedly as the copper content increases. For clusters containing one atom of copper per atom of ruthenium or osmium, the hydrogenolysis activity is three orders of magnitude lower than that of the supported Group VIII


metal alone. These data clearly demonstrate an interaction between copper and the Group VIII metal, and thus provide evidence for the existence of bimetallic clusters. If copper and the Group VIII metal existed as separate entities on the carrier, one would not expect the hydrogenolysis activity of the bimetallic catalyst to be significantly differcnt from that of the supported Group VIII metal alone. The interaction between copper and either ruthenium or osmium may be considered analogous to that in chemisorption, manifesting itself as a surface rather than a solution effect. If one visualises chemisorption of copper atoms on ruthenium or osmium entities consisting entirely of surface

atoms, a model of a highly dispersed bimetallic cluster emerges. From this point of view, it is readily seen how bimetallic clusters may exist with compositions far outside the range of those possible in bulk solid solutions.

For systems whose components exhibit limited miscibility in the bulk, it is interesting to consider what happens as the degree of dispersion of the system is varied (14). In the case of ruthenium-copper, for example, one might expect a large aggregate to consist of a core of ruthenium covered by a layer of copper, corresponding to the “cherry” model of Sachtler for bimetallic systems with a large miscibility gap (15). Because of the almost complete immiscibility of ruthenium and copper in the bulk, it is useful to make the simplifying assumption that the copper in a ruthenium-copper aggregate is confined strictly to the surface. In considering an aggregate consisting of a monolayer of copper on a core of ruthenium, we note that the atomic ratio of copper to ruthenium in the aggregate will increase with decreasing aggregate size. As the degree of metal dispersion becomes very high the atomic ratio of copper to ruthenium in such an aggregate eventually attains a value of the order of unity. The bimetallic entity generated in this manner is a highly dispersed ruthenium- copper cluster. According to this view of the ruthenium-copper system, the atomic ratio of copper to ruthenium required to achieve a given extent of inhibition of hydrogenolysis activity will be much higher for highly dispersed ruthenium-copper clusters than for large aggregates. This is indeed found to be the case, as shown in Figure 2. The metal dispersion, expressed as the percentage of metal atoms present in the surface, is of the order of I per cent for the large ruthenium- copper aggregates and of the order of 50 per cent for the clusters. In the case of the clusters a thousand-fold decrease in hydrogenolysis activity is obtained for a copper to ruthenium atomic ratio equal to one. With the large aggregates, however, the same


inhibiting effect is observed for a fifty-fold lower ratio of copper to ruthenium. Similar effects are observed in hydrogen chemisorption studies, in which a given degree of inhibition of hydrogen chemisorption requires a much higher atomic ratio of copper to ruthenium in the highly dispersed clusters than in the large aggregates (see Figure 3).

Selectivity Effects Recent research on alloys and bimetallic

clusters has revealed that selectivity effects may be very important in such systems. Catalytic studies on Group VIII-Group IB alloys and bimetallic clusters provide a striking example of specificity with regard to the type of reaction. In particular, it has been found that the addition of a Group IB metal to a Group VIII metal leads to marked

inhibition of the hydrogenolysis activity of the latter, while the dehydrogenation activity is affected relatively little (5, I I, 12, 13). This is illustrated in Figure 4 by data on the conversion of cyclohexane on supported ruthenium-copper and osmium-copper cluster catalysts (5 ) . On pure ruthenium and osmium, cyclohexane undergoes appreciable hydrogenolysis to lower carbon number alkanes in addition to dehydrogenation to benzene. The major product of the hydrogenolysis reaction is methane, even at very low conversions. As copper is added to ruthenium or osmium to form bimetallic clusters, the hydrogenolysis activity decreases relative to the dehydrogenation activity, resulting in improved selectivity to benzene. Selectivity is defined here as the ratio of dehydrogenation activity (D) to hydrogen-


Industrial Applications Research on the polymetallic cluster con-

cept at the Exxon Corporate Research Laboratories has recently led to a new catalyst for the reforming of petroleum naphthas for motor gasoline production (19). While the composition of the catalyst, designated KX 130, has not yet been dis- closed, data on its performance have been published (20). The catalyst is several fold more active than conventional platinum catalysts, as shown in Figure 5. Furthermore, the activity maintenance of KX 130 catalyst is far superior to that of a conventional platinum catalyst, as also shown in Figure 5. The superior activity maintenance of KX 130 reIative to a pIatinum/alumina catalyst is related to a lower rate of deposition of carbonaceous residues on KX 130 catalyst. As is well known, the catalytic reforming process is conducted at elevated hydrogen pressures to suppress the formation of carbonaceous residues which deactivate the catalyst. A catalyst with better activity maintenance can be run for a longer period of

olysis activity (H), and is represented by the dashed curves in Figure 4. The different effects of copper on the hydrogenolysis and dehydrogenation activities of the Group VIII metals may be rationalised on the basis of differences in the nature of the rate determin- ing step for the two reactions, as has been discussed by the author elsewhere (11, 16).

Data which have recently become available on other hydrocarbon reactions on Group VIII-Group IB bimetallic catalysts suggest that reactions a t carbon-hydrogen bonds in general behave differently from reactions at carbon-carbon bonds. Thus, the exchange reactions of cyclopentane (17) and methyl- cyclopentanc (18) with deuterium on nickel- copper alloys are affected less than the accompanying hydrogenolysis reactions.


time before regeneration is required. Re- generation of a reforming catalyst involves the combustion of carbonaceous residues from the catalyst surface using a gas of low oxygen content with close attention to control of temperature and other operating conditions. An alternative way to take advantage of a catalyst with superior activity maintenance is to operate at lower pressure. For a given length of operation (cycle length) between regenerations, KX 130 catalyst can be used at lower pressures than a platinum/ alumina catalyst. The advantage of operating at low pressure is associated with a higher yield of liquid reformate for inclusion in gasoline. The choice of the best way to take advantage of the improved activity maintenance depends on the particular situation.

Another catalyst which exhibits improved reforming performance relative to that obtained with platinum/alumina catalysts is the platinum-rhenium/alumina catalyst f ist announced by Chevron (21). The catalyst generally contains rhenium in an amount comparable to the amount of platinum present. Again, a major advantage of this catalyst over platinum/alumina is the improved activity maintenance, which makes it possible to obtain longer reforming cycles or to operate at lower pressures to take advantage of higher reformate yields. From a fundamental point of view, a question of interest with regard to the platinum-rhenium catalyst is the physical and chemical state of the rhenium in the catalyst. Whether or not a highly dispersed alloy or cluster of platinum and rhenium exists on the alumina surface is of interest to catalytic scientists working with this system. Some workers have presented evidence that the rhenium is present as a highly dispersed oxide on the alumina surface at typical reforming conditions (zz), while others have claimed that rhenium can be reduced to the metallic state (23). The data supporting reduction to the metallic state have been obtained on catalysts containing much higher rhenium concentrations than exist in the commercial catalyst; it may

well be that rhenium concentration has an important bearing on its reducibility (24).

Conclusion The concept of highly dispersed poly-

metallic clusters introduces some intriguing features to the science of highly dispersed metals and would appear to have considerable generality. It should be applicable to a variety of combinations of metallic elements, thus extending the range of systems of interest in metal catalysis. Work in this area provides an example of how technological advances in catalysis can be realised within a framework of

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References G. M. Schwab, Discuss. Faraday Soc., 1950, 8,166 D. A. Dowden,J. Chem. Soc., 1950,242 J. H. Sinfelt, Adv. Chem. Engng., 1964, 5, 37 J. H. Sinfelt, Annu. Rev. Mater. Sci., 1972,

J. H. Sinfelt, J . Catalysis, 1973, 29, (2), 308 J. H. Sinfelt, Prog. Solid State Chem., 1975,

D. E. Sayers, E. A. Stern and F. W. Lytle, Phys. Rev. Lett., 1971, 27, (IS), 1204 F. W. Lytle, G. H. Via and J. H. Sinfelt, unpublished data B. M. W. Trapnell, Proc. Roy. SOL. A, 1953, 218, (11351, 566 P. van der Plank and W. M. H. Sachtler, J . Catalysis, 1967,7, (31, 300 J. H. Sinfelt, J. L. Carter and D. J. C. Yates, J. Catalysis, 1972, 24, (2), 283 J. H. Sinfelt, Adv. Catalysis, 1973, 23, 91 J. H. Sinfelt, A. E. Barnett and J. L. Carter, U.S. Patent 3,617,518; 1971 J. H. Sinfelt, Y . L. Lam, J. A. Cusumano and A. E. Barnett, 3. Catalysis, 1976, 42, (2), 227 W. M. H. Sachtler, Vide (Paris), 1973, 28,

2,641

I0, (2)J 55

(I64)2 67 J. H. Sinfelt, Catalysis Ren Sci. Engng,, 19749 9, (11, I47 V. Ponec and W. M. H. Sachtler, J. Catalysis, 1972, 241 (2), 250 A. Roberti, V. Ponec and W. M. H. Sachtler, J . Catalysis, 1973, 28, (3), 381 J. H. Sinfelt, Chem. Engng. News, 1972, 50, (27),18 R. R. Cecil, W. S. Kmak, J. H. Sinfelt and L. W. Chambers, Proc. Am. Pet. Inst., Division of Refining, 1972, 52, 203 R. L. Jacobson, H. E. Kluksdahl, C. S. McCoy and R. W. Davis, Proc. Am. Pet. Imz., Division of Refining, 1969,49, 504 M. F. L. Johnson and V. M. LeRoy, J.

A. N. Webb, J . Catalysis, 1975, 39, (3), 485 M. F. Johnson, J. Catalysis, 1975, 39, (3), 487

Catalysis, 1974, 35, (31, 434


Diaphragm Cells for Chlorine Production PLATINUM METAL OXIDE COATINGS ON TITANIUM ANODES

A symposium held in London in June, organised by the Electrochemical Technology Group of the Society of Chemical Industry, provided an opportunity for discussion of developments over the last ten years i n the operation of diaphragm cells for chlorine production. .Many of the papers presented outlined improvements incelldesign and in diaphragm materials. Dimensionally stable anodes, made of titanium coated with a platinum- group metal oxide, are used in all the cells reviewed.

The electrolysis of brine is the main industrial process for the production of chlorine and its co-product, sodium hydroxide. Two types of electrolysis cell are used in the chlor- alkali industry; mercury cells in which the cathode is a circulating stream of mercury, and diaphragm cells in which anodic and cathodic liquors and products are separated by a diaphragm, usually of asbestos.

Cell Design In an introductory lecture, Dr. M. G. T.

Burrows of BP Chemicals described the stages in the development of the design of diaphragm cells from the late 1880s and compared the performance of four diaphragm cells now in commercial use. Operating data in this comparison included current range, anode area, current density, cell voltage, power consumption and current efficiency. The four types of cell reviewed were those licensed by Hooker, Diamond Shamrock, ICI/ Solvay and de Nora/PPG. In all these cells the dimensionally stable anodes-titanium coated with an oxide of one of the platinum metals-make a significant contribution to their efficiency.

An analysis of the proportion of chlorine produced in diaphragm cells throughout the world showed a wide variation between countries, with the greatest proportion at present in the U.S.A. (73 per cent in 1975).

However, because of environmental con- siderations, there are plans for the complete conversion of the Japanese chlorine industry to the use of diaphragm cells by 1978. In most western European countries, on the other hand, diaphragm cells were used for less than 20 per cent of chlorine production in 1975 and wholesale conversion from mercury cells is not foreseen.

The Dimensionally Stable Anode The inventor of the dimensionally stable

anode, Henri B. Beer (Scientific Research Society NV), described the sequence of his experimental work that culminated in the development of these anodes for the chlor- alkali industry. In 1956 he realised the potential value for the electrochemical industries of anodes made from titanium coated with platinum. The anode material was produced at first by electrodepositing platinum on to the titanium base, but in later work the coating was thermally deposited. Tests with both types of platinised titanium in brine electrolyses showed that thermal deposition gave a coated anode with some advantages over graphite, but with problems of platinum loss and passivation during electrolysis.

By 1965 investigation of the properties of titanium anodes coated with oxides of the platinum group metals had started. Oxides of the rutile type, such as are formed by

Platinum MetalRev., 1976, 20,(4),120-122 120

ruthenium and iridium, showed particular promise. Further improvement was achieved by thermal deposition on to titanium of mixtures of isomorphous oxides of platinum metals and non-platinum metals. Coated anodes of this type had very low overvoltages, were durable and could be used successfully at very high current densities. With some further refinements, these dimensionally stable anode materials have extensively replaced graphite in the chlor-alkali industry.

Mixed Qxide Coatings A paper by Dr. Vittorio de Nora discussed

the present applications and future development of dimensionally stable anodes. Titan- ium anodes coated with catalytically active isomorphous mixed oxides of a platinum group metal and a valve metal are used in the electrolytic production of chlorine, chlorates and hypochlorites. Special coatings have been developed for other processes such as the electrolysis of sea-water, nuclear effluents and sewage. The electrocatalytic activity of dimensionally stable anodes may be modified by the presence of doping agents, which replace part of the valve metal oxide, in the coating. Other types of dimensionally stable anodes, formed on sintered ceramic bases, are being developed for use in molten salt electrolysis, for example, in the production of sodium and aluminium.

Electrolysis of brine in diaphragm cells produces a caustic soda liquor that requires concentration before the separation of its main components-sodium hydroxide, sodium chloride and sodium sulphate. Dr. R. Winkler of Escher Wyss AG described in his paper various types of evaporation plant and discussed the economics of their operation.

Dr. G. van der Heiden of Akzo Zout Chemie reported results of a study of the fundamentals of diaphragm performance in terms of its permeability and electrical resistance. Permeability of an asbestos diaphragm is a function of its porosity, thickness, tortuosity and pore diameter and of the viscosity of the cell electrolyte. The electrical resist-

ance of the diaphragm is a function of its porosity, thickness and tortuosity. Chemical degradation of the asbestos fibres during electrolysis limits diaphragm life,

Reduced Power Consumption Technical advances in diaphragm chlorine

cells developed by the Electrode Corporation were described by T. A. Liederbach of that company. Because of increasing energy costs, the emphasis of development programmes has been on the reduction of cell power consumption. The advent of the dimensionally stable anode made possible a power saving of about 20 per cent in diaphragm cells. A further power saving of 10 to 15 per cent resulted from the development in the early 1970s of expandable anodes and modified diaphragms, which together facilitated reduction of the cell electrolytic gap and, consequently, lowering of the cell voltage.

H. Shibata, Y . Kokubu and I. Okazaki of the Kureha Chemical Industry Co described the Kureha SK-Diacell, developed to replace mercury cells, and designed as a multi-cell unit that can use much of the electrical equipment previously required for the mercury cells. Layout of the diaphragm cell is similar to that of a mercury cell. The SK-Diacell has dimensionally stable anodes and asbestos diaphragms with a high degree of uniformity; it has been designed to operate at currents in the range IOO to 400 kA. Details were given of the performance over several months of an SK-Diacell operating at 330 kA.

The development of the Glanor Electro- lyser by PPG Industries and Oronzio de Nora Impianti Elettrochimici was described by R. J. Scott of PPG. This bipolar diaphragm cell has dimensionally stable anodes. Four Glanor plants are now operating in Japan and one in the U.S.A.; others are under construction.

K. O’Leary of Diamond Shamrock reviewed his company’s work on the development of semi-permeable membrane cells for chlorine production. Nafion membrane material, developed by du Pont, has been


modified and installed in a demonstration plant at Muscle Shoals, Alabama. In its first two months of operation the cell has shown a greater tolerance to load variations than the conventional permeable diaphragm cell.

At Dryden, Ontario, a Nafion membrane cell chlorine plant has been in operation since the beginning of this year. The plant was

J. E. Currey and A. T. Emery reviewed the developments in Hooker membrane cell design and technology that led up to the commissioning of this plant.

Finally, Dr. S. F. Mellish of ICI Mond Division, using published information, gave an economic assessment of the performance of membrane cells by comparison with con-

designed by Hooker Chemicals and Plastics ventional diaphragm cells. Corporation for Dryden Chemicals Ltd. B. M. G .

Temperature Control in the Casting of Copper Alloys

Temperature control in the continuous or semi-continuous casting of copper alloys is vital to the production of sound material. For any given pouring temperature there are optimum rates of pouring and of cooling, and a new installation for the rapid and visible measurement of this temperature has recently been put in at Usine Metal- lurgiques Suisse Selve et Cie at Thun. The usual platinum : rhodium-platinum thermocouple not only records graphic-

ally but by means of an electronic circuit displays the temperature at any one of eight locations on a large luminous panel when a control button is activated. The operator can thus concentrate on the handling of the immersion pyrometer with an eye on the panel, which shows both the location and the temperature. The installation was supplied by Ets. Dr. Ness of Kiissnacht, Switzerland, under the supervision of Dr. F. Roggen of Selve.

Platinum MetalRev., 1976, 20,(4), 122-122 122

Solar Energy Conversion of Water to Hydrogen PHOTOCHEMICAL CLEAVAGE WITH A RUTHENIUM COMPLEX

A potentially most important discovery of a means of producing hydrogen from water by photochemical cleavage has been announced by a team led by Professor David G. Whitten of the Department of Chemistry in the Uni- versity of North Carolina. The reaction, which could have a major impact on future energy requirements, involves a ruthenium complex, tris(2, 2'-bipyridine)ruthenium (11)".

One of the most efficient processes for con- verting optical energy into chemical energy has been shown to be photo-induced electron transfer, and it has been shown earlier that essentially all the excitation energy of this complex can be used to transfer an electron to a long-lived reduced species. Unfortun- ately it has not so far been possible to make use of this reaction as an energy conversion process because the hydrogen and hydroxyl ions rapidly reformed to water.

Professor Whitten and his colleagues have now found (Gerhard Sprintschnik, Hertha Sprintschnik, Pierre Kirsch and David Whitten, J . Am. Chena. Soc., 1976, 98, (8), 2337-2338) that by reacting this compound with dioctadecyl or dihydrocholesteryl esters to yield long-tailed surfactant complexes insoluble in water, these can effectively pro- mote cleavage. Spread as a monolayer on sheets of glass, in contact with water and irradiated by light, these complexes give rise to a steady stream of molecular hydrogen and oxygen. The presence of the long tails apparently lowers the barrier to the electron transfer process, although it is admitted that a detailed mechanism cannot yet be established.

The efficiency of the reaction is relatively high-of the order of 10 per cent-and further work is being carried out to determine

its scope and mechanism, but the results so far obtained indicate that this novel means of solar energy conversion is extremely promis- ing if it can be successfully developed on a large scale.


The Sixth International Congress on Catalysis OUTSTANDING IMPORTANCE OF THE PLATINUM METALS

The four-yearly International Congress on Catalysis provides an opportunity to survey the dominating importance of the platinum metals in catalysis and to sense the major areas of growth and interest. This article reviews some of the papers relevant to the platinum metals that were presented.

The Sixth International Congress on Cata- lysis took place at Imperial College, London, in the week of 12 July 1976. It was attended by almost a thousand full participants from over forty countries. Of the IOI papers presented, more than a third were concerned with the adsorptive and catalytic properties of the platinum group metals, either as heterogeneous or homogeneous catalysts. Some of the more significant of these papers are reviewed here.

Characterisation of Supported Catalysts

Advanced spectroscopic techniques have been applied to the characterisation of silica- supported platinum. X-ray photoelectron spectroscopy (XPS) can be used to estimate the degree of dispersion (I) of the metal (Angevine, Delgass and Vartuli) : nuclear magnetic resonance (NMR) spectroscopy has been directed for the first time to examining adsorbed hydrogen, and interstitial H atoms have been distinguished from surface H atoms (Bonardet, Fraissard and de Menorval). By the use of XPS it has also been shown that the cations of palladium and platinum in dehydrated zeolites form nearly pure ionic bonds with the zeolite framework (Minachev, Antoshin, Shpiro and Yusifov).

Hydrogenation and Hydrogenolysis over Monometallic Catalysts

A number of papers were addressed to the problems of mechanisms in reaction of hydro-

Platinum MetalRev., 1976, 20,(4), 1244125

carbons with hydrogen catalysed by the platinum metals. The competitive hydrogenation of pairs of unsaturated hydrocarbons was used by Burwell, Kung and Pellet as a sensitive indicator of specific particle size effects (I): the interesting conclusion was reached that chemisorption of an acetylenic hydrocarbon may cause metal atoms to be raised outwards from the catalyst surface. The phenomenon of “hydrogen spillover” also received attention : when platinum on alumina was diluted with more alumina, catalytic activity for the hydrogenation of cyclopropane increased considerably, and this was attributed by Compagnon, Hoang-Van and Teichner to the participation in the reaction of hydrogen which had migrated from the catalyst to the alumina.

The mechanism of hydrogenation of allene over the platinum metals was discussed by Khulbe and Mann, who used infra- red spectroscopy to investigate the structure of adsorbed intermediates. Silica-supported catalysts prepared by simultaneous impregnation by solutions of ally1 complexes of platinum and tungsten were reported to be more active for benzene hydrogenation and for ethane hydrogenolysis than similar catalysts not containing tungsten (Ioffe, Kuz- netsov, Ryndin and Yermakov): the tungsten was thought to be in the +2 oxidation state in the active catalysts.

The chemisorption of acetylene on palladium produces a “surface template” which modifies subsequent reaction behaviour of

124

other substances (Inoue, Kojima, Moriki and Yasumori) : this effect should be capable of development to produce highly specific catalysts.

The selectivity of hydrogenation of acetylene to ethylene is greater over a-PdH than over palladium itself, and is less over P-PdH (Borodzinski, DuS, F q k , Janko and Palczewska). Very small palladium particles were found to be unable to form the P-PdH phase.

Bimetallic Catalysts There have been highly significant develop-

ments in catalysts for petroleum reforming during the past decade. The introduction of one or more other elements besides platinum has produced catalysts much less prone to deactivation by carbon deposition, and of greater specificity. This has led to a great deal of continuing research both in academic and industrial laboratories, partly aimed at under- standing the phenomena and partly designed to explore the application of bimetallic catalysts in other areas.

The addition of copper causes a drastic decrease in the activity of iridium for n-pentane hydrogenolysis, while increasing its isomerisation and cyclisation selectivity; the addition of rhenium however increases its hydrogenolysis activity (Brunelle, Montarnal and Sugier). Iridium added to platinum has a similar effect, but hydrogenolysis activity (which is normally undesired) may be poisoned by sulphiding (Ramaswamy, Rat- nasamy, Sivasanker and Leonard). The addition of copper to platinum causes a decrease in isomerisation selectivity, but an increase in dehydrocyclisation selectivity (Jongste, Kuijers and PoneE). Van Keulen presented a kinetic model to describe the loss of selectivity of platinum-rhenium catalysts, and used it in accelerated life tests. Menon and Prasad examined and accounted for the greater sensi- tivity of platinum-rhenium catalysts to sulphur. Alloys of palladium with nickel, ruthenium and platinum all demonstrate an activity maximum for dehydrogenation of

cyclohexane at some composition (Gryaznov, Smirnov and Slin’ko).

Supported Complexes The notion of chemically linking inorganic

complexes active as homogeneous catalysts on to supports such as silica or synthetic polymers, and of using them as heterogeneous catalysts, was a most attractive one, and a number of papers in this Congress reported studies on such systems. I t is however fair to say that, with a few notable exceptions, they have not fulfilled their early promise.

The kinetics of ethylene hydroformylation by a rhodium complex adsorbed on y-alumina were reported by Tjan and Scholten, while the same reaction with propylene using a rhodium-polymer catalyst was investigated by Batchelder, Gates and Kuijpers. Interaction of rhodium trichloride with polymeric di- phenylbenzylphosphine leads to a rhodium(I1) complex active for the hydrogenation of a number of olefins (Imanaka, Kaneda, Teran- ishi and Terasawa), and ruthenium complexes linked to polymeric carboxylic acids are also active for olefin hydrogenation and isomerisation (Braca, Carlini, Ciardelli and Sbrana). A new method for heterogenising catalytically active homogeneous complexes, involving radiation grafting, was described by Garnett and his associates.

Conclusion The large proportion of papers presented

at the Sixth International Congress on Cata- lysis concerned with one or more of the platinum group metals is a continuing witness of their importance as catalytic agents of immense practical value. The development and application of bimetallic catalysts is un- doubtedly one of the major growth points, and their extension into other areas besides petroleum reforming may be confidently expected.

G. C. B. Reference

I G. C. Bond, Platinum Metals Rev., ip75, 19, (411 126


Il’va Il’ich Chernvaev’s Research J J

on the Platinum Metals By Professor George B. Kauffman California State University, Fresno, U.S.A.

This year marks thejfiieth anniversary of the trans efect, one of the most fundamental principles in the synthetic chemistry of the platinum metals, as well as the tenth anniversary of the death of its discoverer, Il’ya Il’ich Chernyaev, one of the Soviet Union’s most distinguished scientists and the man who was undisputedly this century’s most prolijc worker on the coordination chemistry of platinum.

Il’ya Il’ich Chernyaev (I-9), late Academician of the Academy of Sciences of the U.S.S.R., was born on January 21, 1893 in the village of Spasskii in what was formerly Vologda province. After graduating from the Vologda Gymnasium (High School) with a gold medal in 1911, he entered the Natural Science Division of the Physico-Mathe- matical Faculty of St. Petersburg University where he studied under Lev Aleksandrovich Chugaev (1872-1922) (10). In 1915, he graduated with a first class diploma in chemistry, and at Chugaev’s suggestion he remained at the university for training as a university teacher. He also began war research and work on platinum complexes in Chugaev’s laboratory. His first published studies dealt with hydroxylarnine (I I) and aquo salts (12) of divalent platinum. In 1917, he became a contributor to the Platinum Division of the Commission for the Study of Russian Natural Productive Sources (KEPS) of the Russian Academy of Sciences. In 1918, he became Assistant in the Chair of Inorganic Chemistry at the Petrograd University and also became a research associate at Chugaev’s newly created Institute for the Study of Platinum and Other Precious Metals at Petrograd. Until his death on September 30, 1966, he remained at this institute, which was transferred to Moscow in 1934 and underwent several changes in name through the years. Upon Chugaev’s death in 1922, Nikolai Semenovich Kurnakov

(1860-1941) (13) became director of the institute, and on Kurnakov’s death in I941 it was renamed the N. S. Kurnakov Institute of General and Inorganic Chemistry of the Academy of Sciences of the U.S.S.R., with

Il’ya Il’ieh Chernyaev 1893-1966

Academician of the Academy of Sciences of the U.S.S. R. and Professor of the Chemistry of Complex Compounds at the Lomonosov State University i n Moscow, Chernyaeu is remembered as one of the most prolijfie workers on the coordination chemistry of the platinum group metals


Chernyaev as its director, a post which he held until his death.

In 1923, Chernyaev became Assistant Lecturer at Petrograd University. In 1930, he became Docent in Inorganic Chemistry at the Leningrad Chemical-Technological Uni- versity where he directed the Faculty of General Chemistry. In that same year he became Head Chemist of the Platinum Institute. In 1932, he was appointed Professor at Leningrad University, and in 1934, he took charge of the Section for the Chemistry of Complex Compounds in the newly created Institute of General and Inorganic Chemistry of the U.S.S.R. Academy of Sciences. From 1945 until his death he was Professor of the Chemistry of Complex Compounds at the Lomonosov State University in Moscow.

As Chugaev’s successor and most outstanding student, Chernyaev was at the time of his death in charge of the world’s largest school of chemists specialising in the chemistry of the platinum metals and one of the world’s principal centres for the systematic study of coordination compounds in general. His name, of course, is inextricably linked with the trans effect and with numerous researches on the compounds of divalent and tetravalent platinum, especially those containing nitro groups. Less well known, however, is his role as one of the creators of refining technology in the Soviet precious metals industry. As such, his name is associated with a new and advanced method for the purification of platinum, its separation in highest purity, the preparation of pure osmium, a method for extracting platinum metals from low grade ores, the development of a series of analytical methods for noble metals, and the solution of many other critical industrial problems. Among the subjects included in his more than 275 articles are the synthesis, reactions, structure-proof, thermochemistry, thermodynamics, photochemistry, spectroscopy, and optical properties of complexes of the platinum metals. In the last decade of his life he helped to establish the nuclear fuel industry in the U.S.S.R. by his extensive

research on uranium and thorium complexes (7).

Chernyaev was the editor of many important monographs published by the Institute of General and Inorganic Chemistry. He was a co-editor of the Institute’s journal, IzvestGa Sektora IYatiny i Drugikh Blagorod- nykh Metallov (14) from 1947 until 1955, when it ceased publication. In that year he became editor-in-chief of its newly founded successor, the Zhurnal Neorganicheskoi Khiniii. For his discovery and application of the trans effect, Chernyaev received numerous awards and prizes from the Soviet government, including the Stalin Prize, First Class in Chemistry in 1952, four Orders of Lenin, and two Orders of the Red Banner of Labour. He was made a Corresponding Member of the U.S.S.R. Academy of Sciences in 1933 and an Academician in 1943.

Chernyaev’s Work Almost every student of organic chemistry

knows that most substitution reactions do not occur in a random manner, and in a similar manner, substitution reactions among coordination compounds are not random. However, the general principle underlying the directive influences of coordinated ligands was not enunciated until well into the third decade of the present century. Such influences are most pronounced and well investigated among square planar complexes, especially those of platinum( I I).

The chemical behaviour of dipositive platinum complexes was studied by many of the early investigators in coordination chemistry, and the well-known regularities observed in substitution reactions were cited by Werner in his assignment of cis or trans configurations for platinum(I1) complexes, to which he ascribed a square planar arrangement. The compounds chosen by Werner were among the simplest and longest known (1844) platinum isomers, viz., platosemi- diammine chloride or Peyrone’s Salt and platosammine chloride or Reiset’s Second Chloride, both with the formula Pt(NH,),CI,.


On the basis of transformation reactions, Werner assigned them the configurations :

Since the two isomers yield different products, this reaction, known as Kurnakov’s reaction or Kurnakov’s test, may be used to differentiate cis from trans isomers of dipositive platinum or palladium.

In 1926, Chernyaev (18, 19) generalised that a negative group coordinated to a metal

\,,JNHs

\Cl CI / y N H I H,N

c’‘PtJ NH3

cis trans

The synthesis of each of these compounds involves directive influences, and the pre- parative reactions were known as Peyrone’s reaction and Jorgensen’s reaction, respectively and were said to exemplify Peyrone’s rule (cis orientation) (15) and Jorgensen’s rule (trans orientation) (16):

cis Peyrone’s reaction

rrans

Jorgensen’s reaction

(A-NH, or an amine, X-halogen)

In 1893, a third important regularity was observed by the Russian chemist Nikolai Semenovich Kurnakov (13), who found that substitution by thiourea occurs with all the ligands of the cis compound but only with the acid radicals of the trans compound (17):

cis

-2tu+

trails

(A=NH, or an amine, X-halogen or acid radical, tu =thiourea).

atom loosens the bond of any group trans to it and thus explained not only Peyrone’s, Jorgensen’s, and Kurnakov’s reactions but also many other features of the reactions of divalent and tetravalent platinum. He also investigated substitution reactions of complexes of chromium, cobalt, tellurium, and osmium. He postulated that the trans effects of atoms are inversely proportional to their metallic character, i.e., directly proportional to their electronegativities. Electronegative ligands such as NO,-, NCS-, F-, C1-, Br-, and I- have a greater “truns influence” than neutral ligands such as NH,, amines, or H,O. Chernyaev’s original trans-directing series has been extended to include a variety of ligands : CN- - CO - C,H, - NO - H- > CH,- - SC(NHz), .- SR, -PR3 > S0,H- > NOz- N I- N SCN- > Br- > C1- > C,H,N > RNH, -NH, > OH- > H,O (208).

Chernyaev’s trans effect has been useful not only in synthetic work but also in structure-proof. His discovery enabled him and his many students and research workers to prepare many complexes not only of platinum but also of palladium, rhodium, iridium, ruthenium, cobalt, and other metals. The rule made it possible for the first time to plan systematic routes for carrying out inner- sphere substitution reactions in order to prepare platinum complexes in which all the ligands are different. For example, Chernyaev’s early synthesis of the three possible geometric isomers of [Pt(NH,)- (C,H,N)(NH,OH)(NO,)]+ was cited as evidence for a square planar arrangement for platinum(I1) (21). Among his syntheses of pIatinum(1V) complexes we may cite the following: [PtenNH,NO,Cl,]X (three out of four possible isomers and resolution of the two asymmetric compounds) (21, 22),


[PtenNH,NO,BrCl]X (five out of six possible isomers) (231, [Pt(NH,),(NOa)zC12] (all five possible isomers) (24).

Chernyaev’s concept is one of the fundamental principles of synthetic inorganic chemistry and has greatly stimulated the theoretical study of the reactivity and kinetics of coordination compounds, and a number of reviews have been devoted to it (25, 26). At present there are two theoretical viewpoints concerning the possible mechanism of the trans effect.

T h e first type of theory is primarily an electrostatic one that emphasises a weakening or labilisation of the trans bond, suggested by Chemyaev himself (IS), Nekrasov (27), and Grinberg (28). The second type of theory emphasises the lowering of the activation energy of trans replacement and makes use of modern molecular orbital theory (29-33). Two x-bonding ligands competing for the d orbitals of the metal tend to labilise each

other, compared to the more stable cis isomer where no competition takes place, and the stronger r-bonder will weaken the bonding of the ligand trans to it (zob). Several inter- pretations have also been made to explain the trans effect on the basis of u-bonding only (34). It is currently uncertain what interpretation of the trans effect is the best.

Acknowledgements The present study resulted from research on the

separation of inorganic geometric isomers supported by the Research Corporation, the National Science Foundation, and the Petroleum Research Fund, administered by the American Chemical Society. The author, a Visiting Scholar at the Office for History of Science and Technology, University of California, Berkeley, acknowledges the John Simon Guggenheim Memorial Founda- tion for a Guggenheim Fellowship. He is also indebted to Drs G. V. Bykov, V. A. Golovnya, T. N. Leonova, and L. A. Nazarova, and the late Academician Il’ya Il’ich Chernyaev, all of the U.S.S.R. Academy of Sciences, for the location of source material, to Dr Henry M. Leicester and Alexander Beck for assistance in translation, and to Elsie Taylor and Robert ,Michelotti for technical assistance.

References

I V. V. Lebedinskii, “Il’ya Il’ich Chernyaev,” iMaterialy kBiobibliografii Uchenykh S.S.S.R., publ. by Akademia Nauk S.S.S.R., Moscow, Leningrad, 1948. This contains a bibliography of one hundred and one titles to early 1948.

2 V. V. Lebedinskii and A. M. Rubinshtein, Uspekhi Khim., Ig53,22, (31,241

3 A. V. Babaeva, Zh. Obshch. Khim., 1953, 23, (5), 713. This is a summary of Chernyaev’s work on the occasion of his 60th birthday.

4 N. M. Zhavoronkov, Zh. Neoig. Khim., 1967, 12, (z), zgr. This contams a list of one hundred and seventy-five of Chernyaev’s works from 1948 to 1966.

5 I. A. Fedorov, in “Vydayushchiesya Sovetskie Khimiki Akademiki A. A. Grinberg i I. I. Chernyaev”, publ. by “Nauka”, MOSCOW, 197% 39

6 A. V. Babaeva, Ibid., 46 7 V . A. Golovnya, Ibid., 58 8 “I. I. Chernyaev, Izbrannye Trudy,

Kompleksnye Soedineniya Platiny”, ed. Ya. K. Syrkin, publ. by “Nauka”, Moscow, 1973. This contains seventy-six of Chernyaev’s articles on platinum complexes.

g D. N. Trifonov, “Dictionary of Scientific Biography”, ed. C. C. Gillispie, Charles Scribner’s Sons, New York, 1971, Vol. 3, 235

10 G. B. Kauffrnan, J. Chem. Educ., 1963, 40, (IZ), 656; Platinum Metals Rev., 1973~17, (4), I44

11 L. A. Chugaev and I. I. Chernyaev, J. Rtcss. Phys. Chem. SOC., 1g15,47,201; Compt. Rend.,

12 L. A. Chugaev and I. I. Chernyaev, J . Rms. Phys. Chem. SOC., 1915, 47, 1806; Compt. Rend., 1915, 161, 792

13 G. B. Kauffman and A. Beck, J. Chem. Educ.,

14 G. B. Kauffman, Platinum Merals Rev., 1974,

15 M. Peyrone, Liebigs Ann. Chem. Pharm., 1844, 51,I

16 S. M. Jorgensen,J. Prakt. Chem., 1886, 33, (10-11), 489; Z. Anorg. Chem., 1900, 24, (2),

I53 17 N. S. Kurnakov, J . Rms. Phys. Chem. SOC.,

1893, 25, 565; J . Prakt. Chem., 1894, 50, (11-12), 481

18 I. I. Chernyaev, Izv. Inst. Zzucheniiu Platiny i Drug. Blagorodn. Metall. (hereafter abbre- viated Izv.), 1926,4, 243

19 I. I. Chernyaev, Izv., 1927, 5, 118 20 J. E. Huheey, “Inorganic Chemistry: Prin-

ciples of Structure and Reactivity”, Harper and Row, New York, 1972, (a) p. 424;

1915, 161,637

196293% (I),44

18J (41,

(b) P. 427 21 I. I. Chernyaev, Izv., 1928, 6, 55 22 I. I. Chernyaev, Zzv., 1928, 6,23 and 40 23 I. I. Chernyaev and A. D. Adrianova, Zzv.,

1949123~ 9


24 I. I. Chernyaev and G. S. Muraveiskaya,

25 J. V. Quagliano and L. Schubert, Chem. Rev.,

26 F. Basolo and R. G. Pearson, “Mechanisms of Inorganic Reactions”, John Wiley and Sons, New York, 1958, Chap. 4; Prog. Inorg. Chem., 196294,381

27 B. V. Nekrasov, “Kurs Obshchei Khimii”, Moscow, Leningrad, 1935, Vol. 2, p. 777; rev. ed., Gosudarstvennoe Nauchnotekhnicheskoe Izdatel’stvo Khimicheskoi Literatury, Mos- cow, Vol. 2, p. 860; idem, Zh. Obshch. Khim., 1937, 7, (111, 1594

12% 1955,31, 5

1952, 50, 201

28 A. A. Grinberg, Izv., 1932, 10,47 29 J. Chatt, L. A. Duncanson and L. M. Venanzi,

3. Chem. SOC., 1955,4456 and 4461

30 A. Pidcock, R. E. Richards and L. M. Venanzi,

31 L. E. Orgel, J . Znorg. Nucl. Chem., 1956, 2,

32 J. A. Wunderlich and D. P. Mellor, Acta CTyst., 1954, 7, 130; Ibid., 1955, 8, 57; P. R. H. Alderman, l?. G. Owston and J. M. Rowe, Ibid., 1960, 13, 149

33 F. Basolo, J. Chatt, H. B. Gray, R. G. Pearson and B. L. ShawJ. Chem. SOC., 1961,2207

34 C. H. Langford and H. B. Gray, “Ligand Substitution Processes”, W. A. Benjamin, New York, 1965, p. 25; Ya. K. Spkin, Izv. Akad. Nuuk S.S.S.R., Otdel. Khim. Nuuk, 1948, (I), 69; L. M. Venanzi, Chem. Br., 1968, 4, (4), 162; R. S. Tobias, Inmg Chem.:

3. Chem. Soc.,A, 1966, (12), 1707

(31, I37

197% 9, (51, 1296

The Electrodeposition of Osmium Osmium is a rare metal with some unique

properties. I t has the highest work function of any metal and this has led to its use as thin coatings in thermionic devices. It has also been suggested that, because of its high melting point (30s0°C), osmium could find application as a coating material for reed switches particularly at higher loads where arcing temperatures are greater. Such uses require the development of methods for producing thin coatings of the metal and a recent paper by J. N. Crosby, of International Nickel (Trans. Inst. Metal Finishing, 1976, 54, (II), 75) describes a novel method for the electrodeposition of osmium.

The new electrolyte is prepared by reacting sulphamic acid with osmium nitrosyl complexes, in particular K,[Os(NO)(OH) (N02)J. Bright osmium deposits are obtained in both acid and alkaline conditions. However, below pH 7 the current efficiencies are low (-2 per cent) and base metals such as copper have first to be given a protective gold coating. For maximum current efficiency (8 to 12 per cent) the preferred operating range is pH 12 to 14 when a deposition rate of z to 3 pm/hr can be achieved. Plating performance is critically dependent on temperature and 70°C is the optimum. A plot of plating rate against current density shows the former to pass through a sharp maximum at 2 to 3 A/dm2. An advantage of this system is that it is not markedly dependent on osmium concentration so that it can be run for long periods without replenishment (e.g. from its normal level of 4 g/1 0 s down to 0.5 g/1 0 s ) .

However, this advantage is offset by the electrolyte’s unfortunate characteristic of producing blackened deposits after a period of satisfactory operation.

Investigation of the blackening phenomenon showed that an anodic reaction plays a particularly important part in the bath’s operation. If an electrolyte producing blackened deposits is operated in the cathode compartment of a divided cell the deposits soon improve and the normal mode of operation can then be resumed. However, con- tinued use in the divided cell leads to a dramatic reduction in efficiency. Further- more osmium cannot be deposited from a fresh electrolyte in such a cell. Thus a certain amount of anodic oxidation is necessary for the operation of the electrolyte but too much is deleterious. This is consistent with the fact that the current efficiencies of freshly prepared solutions tend to be very low ini- tially and to rise during use.

The osmium deposits obtained under the preferred conditions are bright and adherent but are highly stressed and at thicknesses greater than I pm are microcracked. Deposits become dull and heavily cracked at thicknesses of - 6 pm.

An account is given of infra-red studies carried out to elucidate the nature of the electrolytes.

The need to operate this electrolyte with the intermittent use of a divided cell suggests that it is likely to find somewhat limited application, while the highly stressed nature of the deposits tends to reduce the useful thicknesses obtainable. C . W. B.


ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Epitaxial Growth and Structure of Evap- orated Platinum Films on Rock Salt J. KOSHY,J. Crystal Growth, 1976,34, (z), 345-349 Transmission electron microscopy was used to study the structure of Pt single crystal films IO- 7ooA thick, epitaxially grown by vacuum evaporation on the cubic, octahedral and dodecahedra1 planes of rock salt at 20-5oo0C. The Pt single crystals are shown to be in parallel orientation to the crystallographic planes in the substrate surface. Below a substrate temperature of 430-450"C the films were found to be polycrystalline, and became perfectly continuous at 600A.

An Investigation of the Mechanism of the Oxidation of Carbon Monoxide Adsorbed onto a Smooth Pt Electrode in Aqueous Acid C. MCCALLUM and D. FLETCHER, J . Electroanal. Chem. Interfacial Electrochem., 1976, 70, (3), 277-290 The mechanism of the anodic oxidation of CO adsorbed on to a smooth Pt surface was studied by potential step techniques. The heterogeneous chemical reaction between the adsorbed CO and the oxidised Pt species occurred at the edge of growth of two dimensional islands of the Pt oxide.

The Nature of Adsorption of some Simple Gases on Platinum ZH. YA. SMORODINSKAYA, R. E. MARDALEISHVILI and D. MINK, Dokl. Akad. Nauk S.S.S.R., 1976, 228,

Studies of the adsorption of N,, Ar, O,, CO and H,O on a clean surface of Pt sponge and on the same surface covered with irreversibly adsorbed 0, or CO were carried out by the determination of primary and secondary adsorption isotherms. The results show that the quantities of reversibly adsorbed Ar, N, and CO at -196°C and that of H,O at 26°C on the surface of clean Pt are practically the same and coincide with the quantity of 0, and H, adsorbed in the surface monolayer at o and -78°C.

Steric Properties of the Transition Metal Ions on Stepped Surfaces Y. w. TSANG and L. M. FALICOV~J. Phys. C, Solid State Phys., 1976, 9, (I), 51-61 Studies of the effect of surface steps in the transition metals Pt and Au show that the steps definitely play a catalytic role in the case of Pt surfaces but do not increase the chemical reactivity of Au surfaces. The results are explained.

f4)J g00--9*3

The Effect of Gold on Hydrogenolysis, Isomerisation and Dehydrocyclisation Re- actions on Polycrystalline Platinum and Iridium Foils D. I. HAGEN and G. A. SOMORJA1,J. Catabsis, 1976, 41, (31,466-481 Spectroscopic studies were made of the effect of the addition of Au to polycrystalline Pt and Ir foil samples on the initial reaction ratio for the hydrogenolysis, isomerisation and dehydrocyclisation reactions at roo-500°C and I O - ~ torr. The results showed that the addition of Au to the Pt and Ir surfaces decreases the rates for all reactions studied. A linear decrease in isomerisation rate as a function of Au coverage was observed but hydrogenolysis and dehydrocyclisation decreased similarly, and more rapidly than isomerisation.

The Thermal Desorption of Carbon Mon- oxide from Platinum and Platinum-Gold Films J. J. STEPHAN and v. P O N E C , ~ . Catalysis, 1976,42, (11, 1-9 Studies of CO adsorption and desorption on Pt and Pt-Au films show that the amount of CO adsorbed on Pt-Au films at 295K and at pressure of z x IO@ torr is low and almost independent of alloy composition. The thermal desorption spectrum of CO measured at 78-575K shows a broad peak caused by desorption from both Pt and Au. A broad maximum in the range 300- 4ooK was also observed. A model for CO adsorption on Pt and 1%-Au films is proposed.

A New Platinum Fluoride : PtIIPtIVF,

and P. HAGENMULLER, Mater. Res. Bull., 1976, 11,

(6), 689-693 Studies of the Pt-F system show the existence of a new fluoride PtIIPtIvF, which contains Pt in an oxidation state lower than that found in the already known Pt fluorides PtF,, PtF, and PtF,. The compound has a rhombohedra1 LiSbF,-type structure with a=5.565A and c(=53.85".

Plutonium-Palladium Pu,Pd, D. T. CROMER, Acta Cryst. B, 1976, 32, (6), 1930- I932 X-ray studies of a 67 at.?; Pd-Pu alloy arc melted and heat treated at 950°C for 7 days showed the existence of a new compound PuJ'd, which crystallises in Cmcm space group with a=g.zor, b=7.159, C59.77I& Z=4 and pc= 12.89 g/cma. The new compound is thought to have the same structure as Ga5Zr,.

A. TRESSAUD, F. PINTCHOVSKI, L. LOZANO, A. WOLD


Effect of Fast Quenching on Phase Trans- formation and Structure of U-(0.05-6 at.?;) Ru Alloys

J. Nucl. Muter., 1976, 60, (I), 66-78 The structure of 0.054 at.% Ru-U alloys after fast quenching from the p and y phases was studied using thermal analysis, X-ray diffraction, and optical and transmission electron microscopy. The results show that alloys containing 6, 3 and I at.% Ru, quenched from 900"C, transform martensitically to a-uranium. Uranium alloys containing 0.05 and 0.1 at.% Ru quenched from the P-phase show a fine a grain structure. This indicates that small amounts of Ru can be used for grain relining in U.

Ethylene Hydrogenation on Evaporated Iridium Films P. MAHAFFY, P. B. MASTERSON and R. s. HANSEN, J . Chem. Phys., 1976,64, (IO), 3911-3916 Studies were made of the ethylene hydrogenation reaction catalysed by evaporated Ir thin films over a wide temperature range using isotope labelling techniques. The results showed that at 15oK the rate of a surface dehydrogenation becomes significant. The microscopic surface area of the Ir films measured by HZ adsorption is proportional to film thickness for average thicknesses of 3c-2ooA.

A. A. ABOU-ZAHRA, F. H. HAMMAD and P. BOUDEAU,

Thermal Dissociation of Iridium Dioxide

and D. M. CHIZHIKOV, Zh. Neorg. Khim., 1976,

A high temperature mass-spectrometric method was used to study the thermal dissociation of IrO, at 780-850K. I t was found that the dissociation has a condensation character and is accompanied by a formation of solid solutions in the Ir02-Ir system. The dissociation pressure and heat of dissociation of IrO, are given.

E. K. KAZENAS, V. K. TAGIROV, L. K. SHUBOCHKIN

21, (51, 1403-1404

CHEMICAL COMPOUNDS Chemistry of Metal Hydrides. XVII. Iso- cyanide Insertion into the Pt-H Bond, and the Formimidoyl Ligand. XVIII. The For- mation of Secondary Carbene Complexes from Imidoyl Derivates D. F. CHRISTIAN, H. C. CLARK and R. F. STEPANIAK, J. Organometal. Chem., 1976, 112, (2), 209-225,

The insertion of isocyanide into the Pt-H bond of the tram-[PtH(CNR)L,]CI (R=p-tolyl; L= PEt,, PMe,Ph) in non-polar solvents yielded the Pt formimidoyl complexes trans-PtCI(CHNR)L,. Protonation of trans-PtCl(CHNR)(PEt,), occurred reversibly to produce the cation trans-[FtCl(CHNHR)(PEt,) ,I+ while methylation produced tram-[PtCl(CHNMeR)(PEt,) ,I +.

227-241

Complexes of Platinum and Palladium with Phosphorus Ligands A. D. RATTRAY, Diss. Abstr. B, 1976, 36, (8), 3947- 3948 Preparation and interconversion reactions are described for the complexes [M,Xz(PPh,0)2 (PPhzOH) ZIJ [MX(PPhzO)(PPhzOH) 21, [MX (PPh,O)(PPh zOH)(PRdI, [MXdPPhzP(O)Phz) 21,

where M-Pd or Pt, X=chloride or bromide; Ph=phenyl, and R=phenyl or ethyl. The complex [PtCI(Phen)(PEt,),]BF,, containing in the solid state the first known example of a mono- dentate phenanthroline ligand, was also isolated and i s described.

Study of Catalytic Properties of Platinum- Tin Complexes with Dimethyl Sulphoxide, Dimethyl Formamide or Dimethyl Aceta- mide

YA. G. MUKHTAROV, A. N. SHAN'KO and L. KH. FREIDLIN, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1976, (9, 971-975 Studies of a series of new Pt(I1)-Sn(I1) complexes containing dimethyl acetamide and dimethyl formamide show their considerably higher activity in isomerisation and hydrogenation of C =C containing compounds than that of Pt-SnC1, complex. All the studied complexes were found to catalyse the selective hydrogenation of phenylacetylene to styrene and diphenylacetylene to diphenylethane.

N. V. BORUNOVA, P. G. ANTONOV, YU. N. KUKUSHKIN,

Carboxylates of Divalent Rhodium L. A. NAZAROVA and A. G. MAIOROVA, Zh. Neorg.

New dimeric E&(II) complex compounds with metal-metal bonds were synthesised. The general formula is Rh,(Ac)&A,, where Ac is HCOO- or CHCOO- and A is an organic complex containing various functional groups, benzene ring and unsaturated atoms.

Khim., 1976~21, (4), 1070-1074

ELECTROCHEMISTRY


Kinetics of the Hydrogen Electrode Re- actions on Platinum in the NaHSO,+ KHSO, Eutectic Melt

Electroanal. Chem. Interfacial Electrochem., 1976, 71, (11, 5171 The kinetics of the H, electrode reactions on Pt wire in the NaHSOd and KHSOl melt were studied at -185°C. Under potentiodynamic conditions both the anodic and cathodic processes can be interpreted with the H, electrode reaction mechanism already known. The mechanism of the cathodic reaction changes at <O.IV because of a sulphide species formed on the electrode, which is produced by a reduction of the melt components.

R. 0. LEZNA, W. E. TRIACI and A. J. ARVfA, J.

E.M.F. Measurements of Cells Employing Metal-Metal Oxide Electrodes in Aqueous Chloride and Sulphate Electrolytes at Tem- peratures between 25-250°C J. v. DOBSON, P. R. SNODIN and H. R. THIRSK, Electrochim. Acta, 1976, 21, (7), 527-533 E.M.F. measurements were made on Pt-PtO,, Ir-IrO,, Rh-Rh,O, and Zr-ZrO, electrodes at 25-,qo°C and pH 1-12 using aqueous chloride and sulphate electrolytes. The results showed an 0, and sulphate response at 25°C for a Pt-PtO, electrode in concentrated H,SOI. The effects of temperature, pressure, concentration and time are discussed.

ELECTRODEPOSITION AND SURFACE COATINGS Precious Metal Plating H. GROSSMANN and G. SCHAUDT, Galvanotechnik,

Studies of Pd, Ru, Rh, and hard Au coatings electrodeposited on electrotechnical connecting components show that Pd deposits perform best in abrasion tests. Ru and Rh deposits were found satisfactory in rotary switches and in plug and socket connectors. Pd deposits applied in sliding and plug contacts show similar wear resistance to hard Au deposits.

The Chemistry of Palladium-Tin Colloid Sensitising Processes R. L. COHEN and R. I.. MEEK,J. Colloid Inteiface sci.,

Massbauer spectroscopic studies were made of the chemical composition of layers deposited on graphite substrates by commercial Sn-Pd sensitising system. The results showed that the catalytic centres consist of colloidal particles of Pd-Sn alloy and that the primary purpose of the "acceler- ator" step in the process is to remove Sn hydroxide deposits.

1976.7 67, (41,292-297

1976,55, (I), 156-162

LABORATORY APPARATUS AND TECHNIQUE Molecular Beam Apparatus with Supersonic 0, Beam (700-3000 m/sec) for Reactive Scattering Experiments with Metal Atoms c. B. COSMOVICI, K. w. MICHFL, R. DIRSCHERL and u. STANGGASSINGER, Rev. Sci. Instrum., 1976, 47,

A simple alignable nozzle source for mass spectrometric detection systems consists of a pinhole in the wall of a U-shaped Pt tube which is closed at one end and connected to the gas inlet at the other. When the nozzle, which can withstand corrosive 0, and can be heated directly, is used in conjunction with a thermal oven, beam collisional energies from 0.1 to rev can be obtained.

(61,667476

Mercury Thermometers - Are They Becom- ing Antiques? B. w. MANGUM, N.B.S. Tech. News Bull., 1976,

Electronic thermometers for medical applications employing either thermistors or Pt resistors have been developed, and the working principles are described. The accuracy is --o.I"C.

60, (21, 13-17

Radiative Heat Transfer from Metal Wires: Hemispherical Total Emittance of Platinum B. J. JODY and S. C. SAXENA, 3. Phys. E: sci.

Data of the radiative heat transfer from Pt at 400-15ooK measured on a general hot wire apparatus were analysed to determine the hemispherical total emittance of Pt as a function of temperature. The use of such an instrument for the determination of electrical resistivity of metal wires at high temperature is discussed.

Instrm., 1976% (9,359-362

Conductivity Cell for Molten Glasses and Salts F. G. K. BAUCKE and W. A. FRANK, Glastech. Ber.,

An immersion or dip-type cell incorporating two parallel Pt electrodes was developed for conductivity measurements of molten glasses and salts. A cylindrical volume of the melt is enclosed by a ceramic or S O , tube and subjected to the homogeneous and uniform electric field between the electrodes. The cell also allows measurement of local conductivities within technical glass melting units.

1976,491 (7), 157-161

Electrical Conductivity Measurements on Silicate Melts Using the Loop Technique H. S. WAFF, Rev. sci. htrum. , 1976, 47, (7), 877-879 The electrical conductivity of silicate melts was measured at up to 1550°C by a technique using loops of 0.635 mm diameter So%Pt-zo%Rh wire. The melt samples are suspended as droplets on the loops and maximum surface exposure results in rapid equilibration of the melt with the con- trolled atmosphere. This technique gives repro- ducible rcsults to &s% and is suitable for electrical conductivity studies on silicate melts containing redox cations.

The Choice of Cathode Material in a Hot Cathode Ionisation Gauge

Studies of cathode materials for use in an u.h.v. gauge showed that cathodes of Tho, on I r or W have reasonable emission efficiencies, low evaporation rates and are relatively unaffected by chemically active gases. The Tho, on I r cathode can be exposed to air when hot without damage, which makes it particularly useful for ionisation gauge applications.

P. E. GEAR, vacuum, 1976,26, (I), 3-10


HETEROGENEOUS CATALYSIS Ammonia Oxidation over Platinum-promoted Oxide Catalysts N. I. IL'CHE~KO, Kinet. Kataliz, 1976, 17, (2), 386-391 Studies of low temperature NH, oxidation to N, and N,O over oxide catalysts show that additions of 0.1% Pt to Co304, MnO, and V,O, increase considerably their catalytic activity. The selectivity of the process remains almost unchanged. It is suggested that Pt facilitates the activation of NH, molecules and increases the rate of reduction of the oxide catalysts.

Study of Hydrogenation Reactions with Rhodium and Platinum Catalysts Supported on lon Exchange Resins S. SABADIE and G. DESCOTES, Rull. Soc. Chem. Fr.,

Studies of the activity of Pt and Rh catalysts supported on ion exchange resins made during hydrogenation of cyclohexene, alkyl alcohol, carvone and phenylacetylene showed better selectivities than the ones obtained with the catalysts supported on charcoal. The influence of the metallic ions on the process is described.

On the Electrolytic Mechanism of Liquid- phase Propene Oxidation over Palladium Catalysts KH. KINTSA and L. P. MASHKOVA, Kinet. Kataliz,

A potentiodynamic method was used to study the oxidation of propene and reduction of 0, on dispersed Pd and Au-Pd alloys. It is shown that the Pd-Au catalysts have higher catalytic activity in the reaction of propene oxidation than the pure catalyst, with 25 at. $4 Au-Pd most active.

Synthesis of Cyclododecane hy Cyclodode- canone Epoxide Isomerisation on Pd and Rh F. A. CHERNYSHKOVA and D. v. MUSHENKO, Neftekhimiya, 1976, 16, (2), 250-254 The isomerisation of cyclododecane epoxide leading to the formation of cyclododecanone was carried out on supported Pd and Rh catalysts and also on A1,0,, SiOz and zeolite catalysts. The results show that only Pd and Rh supported on A1,03 and C give high (80-83 "/o) cyclododecanone yields at 245-265°C in H, atmosphere.

Transformations of Cyclohexane with Water Vapour on Alumina-Rhodium Catalyst v. N. MOZHAIKO, G. L. RABINOVICH and G. N. MASLYANSKII, Nefiekhthimiya, 1976, 16, (I), 45-50 The transformations of cyclohexane with H,O vapour were studied over a 0.6 wt."/, Rh/A1,03 catalyst. It is shown that dehydrogenation and decomposition of cyclohexane take place at 380-460°C. The activation energy of dehydrogenation was found to be 23 kcal/mole. The

1976% (5-61, 911-913

1976, 17, (2), 362-366

selectivity of dehydrogenation increases with a decrease in both temperature and H,O : cyclohexane ratio. At 420'C and H,O . cyclohexane ratio of 4 the selectivity reaches 95 mole :/u.

Methylcyclohexane Transformations with Water Vapour to Aromatic Hydrocarbons on Alumina-Rhodium Catalyst G. L. RABINOVICH and V. N. MOZHAIKO, Neftekhhimiya, 1976, 16, (2), 187-193 Transformations of methylcyclohexane with H,O vapour over 0.6 wt.% Rh/y-Al,03 catalyst at 40~-48o"C with a molar ratio of H,O : methylcyclohexane of 4 to 12 were studied. The transformation takes place in three parallel reactions: dehydrogenation leading to toluene formation, dehydrodemethylation leading to benzene formation and decomposition resulting in C oxides formation. The total output of aromatic hydrocarbons is > 80 rnol. 7;.

Alkane and Cycloalkane Reactions on Rhodium, Rhodium-Copper and Related Films A. PI~TER and J. K. A. CLARKE, 3. Chem. SOC., Faraday Trans. I , 1976, 72, (5), 1201-1211

Studies of the catalytic reaction of n-hexane-H, mixture on Rh-Cu alloy films at -570K showed the dehydrocyclisation/hydrogenolysis product ratio is one order of magnitude greater than that found on roo$//, Rh films. 1.5-cyclisation occurs on Rh-Cu films and also on Rh-Au and Rh-Sn films. Ring enlargement of methylcyclopentane and of I. I-dimethylcyclopentane occurs above -540K on both Rh and Rh-Cu films.

Mechanism of the Catalytic Effect of Osmium Compounds on the Oxidation of Copper(II) with Periodate G. I. ROZOVSKII, z. A. POSHKUTE and A. YU. PROKOPCHIK, Zh. Neorg. Khm., 1976, 21, (S), 1248-1251 The catalytic effect of OsO, on the oxidation of Cu(I1) with periodate was studied. It is shown that the catalysis involves the oxidation of Os(VI1) to Os(VII1) with periodate, followed by the reduction of the oxidised form of 0 s by Cu(I1). The reaction of Os(VII1) and Cu(I1) was found to be reversible.

HOMOGENEOUS CATALYSIS Catalytic Asymmetric Hydrosilylation of Ketones. I. Chwal Phosphine-Plathum(I1) Complex-catalysed Hydrosilylation T. HAYASHI, K. YAMAMOTO and M. KUMADA, J . Organometal. Chem., 1976, 112, (9 , 253-262 Studies of the hydrosilylation of alkyl phenyl ketones and dialkyl ketones with HSiMeC1, in the presence of the [(PhMe,P)PtCl,] , catalyst showed good yields of corresponding silyl ethers of


I-phenylalkanols and silyl enol ethers respectively. Asymmetric hydrosilylation of a series of alkyl phenyl ketones catalysed by chiral phosphine- Pt(I1) complexes was studied.

Palladium-catalysed Dibenzofuran Synthesis by Dehydrogenative Ring Closure A. sHIOTANI and H. ITATANI,~. Chem. soc., Perkin Trans. I, 1976, (11), 1236-1241 Studies of the dehydrogenation of diphenyl ethers in the presence of a Pd acetate catalyst showed that under 0, pressure the coupling proceeds with a catalytic quantity of Pd acetate to give dibenzofuran in higher yields relative to dimers. The regeneration of the Pd acetate is described.

CHEMICAL TECHNOLOGY The Effect of Nickel and Palladium Additions on the Activated Sintering of Tungsten R. M. GERMAN and v. HAM, Internat. J. Powder Metall. Powder Technol., 1976, 12, (2), 115-125 Studies of sintering processes on two different W powders show that Pd is a better sintering activator than Ni at 1100-1400~C. Both Pd and Ni give best shrinkage enhancement when present at the quantity of four atomic monolayers.

NEW PATENTS

ELECTRICAL AND ELECTRONIC ENGINEERING

METAL§ AND ALLOYS Alloys Containing Platinum Group Metals JOHNSON MATTHEY & CO. LTD.

French Appl. 2,277,903 Apart from impurities, the alloy contains at least 40% Ni or Co, a trace to 30% Cr and a trace to 15% of one or more of Pt, Pd, Rh, Ir, 0 s and Ru. The alloy is useful for manufacturing reaction motor parts and gas turbines.

Electroetching of Platinum in the Titanium- Platinum-Gold Metallisation on Silicon Integrated Circuits R. P. FRANKENTHAL and D. H. EATON, J. Electrochem.

A rapid electrolytic method of etching patterns in Pt onsemiconductor slices is described, a periodic- ally varying potential being applied to the Si wafer immersed in HC1 solution at room temperature. The dissolved Pt can be recovered and the process is also applicable to the etching of metallisations on other high-resistance substrates.

Hydrogen-sensitive Palladium Gate MOS Capacitors M. c. STEELE, J. w. HILE and B. A. MACIYW,?. Appl.

The C-V characteristics of Pd gate MOS capacitors using thin Pd films (roo& on thin oxide layers ( IOO-IOOO& change considerably when exposed to an air ambient containing up to 4% Ha. The changes are attributed to the lowering of the Pd work function brought on by the formation of Pd hydride.

SOC-, 1976,123, (51, 703-706

PbS., 1976, 471 (6), 2537-2538

ELECTROCHEMISTRY Seawater Electrolysis Cathode ELECTRONOR CORP. US. Patent 3,947,333 A cathode for a cell has an electrically conductive electrode base with an outer coating, on at least a portion of its surface, of an alloy of Pd and IO-~O% of either Ag or Pb.

Iridium Thin Ribbon Electrodes for Electro- chemical Cells E. I. DU PQNT DE NEMOURS & CO.

US. Patent 3,954,590 An electrolytic moisture direction cell consists of a substrate and spacxi ih in ribbon metal electrodes having a thickness of 0.1-1.0 pm attached

to and supported by the substrate. The electrodes consist of an anode and a cathode, the cathode being formed by Ir or an alloy containing at least 10% Ir and the remainder Pt. A hygroscopic film is deposited on the substrate and fills at least a portion of the space between the anode and the cathode.

ELECTRODEPOSITION AND SURFACE COATINGS


Thin Layers of High Melting Point Materials SIEMENS A.G. British Patent 1,442,109 A thin layer of Os, W, Mo or Re is produced on a substrate by evaporating the (IV) oxide of the metal under a high vacuum while heating the substrate.

Chemical Plating Catalyst A.M.P. INC. U S . Patent 3,937,857 A substrate is catalysed for chemical plating by applying and then thermally decomposing a thin film of a complex L,PdX, or the corresponding Pt complex. L is a ligand or unsaturated organic group, X is halide, alkyl or a bidentate ligand, m is 1-4 and n is 0-3. A typical complex is Pd bis-triphenylphosphine dichloride.

Brazed Electronic Circuit Package BURROUGHS CORP. U.S. Patent 3,941,916 Au plated electrical lead pins are fixed in pin receiving holes in a ceramic layer of an electronic package by depositing Pd-Ag on the interior surfaces defining the holes, depositing Au on the Pd Ag, positioning Au plated pins within the hoIes and brazing the Au plated pins within the holes with an Au-Ge solder.

Rhodium Plating of Contacts LICENTIA PATENT-VERWALTUNGS G.m.b.H.

German Offen. 2,442,212 Long life spring contacts are provided on spring Ni-Fe elements, by applying a Rh layer in at least two electroplating operations with intermediate annealing to increase the adhesion.

LABORATORY APPARATUS AND TECHNIQUE Ion Monitoring ETAT FRANCAIS British Patent 1,436,287 Ion monitoring apparatus for the detection of a cyanide ion-forming component in a gaseous medium of cyanide ions in aqueous solution has a working electrode formed of a metal selected from Pt, Ag and Au.

Oxygen Sensor GENERAL ELECTRIC CO. British Patent 1,436,339 The sensor has a first electrode of a corrodible metallic base member such as W, a second electrode of Rh or Pt wire coupled electrically to the metal of the first electrode, and a third electrode of Ag with at least a partial layer of Ag halide, other than fluoride, on the surface.

Gas Pollution Monitor BRITISH GAS COW. British Patent 1,438,107 Low concentrations of NOx and CO in a gas are measured by apparatus which includes a galvanic cell associated with each of two gas streams and consisting of a Pt cathode in contact with a buffered halide electrolyte in which is immersed an active C or Ag anode.

Oxygen Sensor Devoid of Catalytic Oxidation Activity

An oxygen sensor has a layer of a solid oxygen-ion electrolyte, a first electrode formed on one side of the layer to communicate with a reference gas and a second electrode formed on the opposite side of the layer of Pt or Rh and at least one catalytic poison selected from Pb, S, P, As and their compounds. The catalytic poison is such that the complex material is devoid of catalytic activity with respect to oxidation of CO and hydrocarbons in an engine exhaust gas.

NISSAN MOTOR CO. LTD. U.S. Patent 3,941 ,673

HETEROGENEOUS CATALYSIS Alkanolamine Derivatives IMPERIAL CHEMICAL INDUSTRIES LTD.

British Patent 1,433,592 Hydrogenolysable protecting groups are removed by catalytic hydrogenation in the presence of Pd on charcoal catalyst in the production of ~-isopropylamino-1-[2-methoxy-~-(~-methyl- ureidomethyl) phenoxy]-2-propanol.

Preparing Cycloolefins INSTITUT NEFTEKHIMICHESKOGO SINTEZA IMENI A.V. TOPCHINA AKADEMII NAUK S.S.S.R.

British Patent 1,434,176 A cycloolefin is prepared by hydrogenating the corresponding cyclodiene with hydrogen in the presence of a catalyst which is an alloy containing Pd and Ru or Rh, preferably 10% Ru or 2% Rh.

Hydrocarbon Conversion with a Sulphided Catalytic Composite UNIVERSAL OIL PRODUCTS CO.

U.S. Patent 3,936,369 The hydrocarbon is contacted with a catalytic composite consisting of a porous carrier material containing 0.01-2% Pt or Pd, 0.01-2% Ir, 0.01-5% Ge and 0.1-3.5% halogen. The Pt or Pd, Ir and Ge are uniformly dispersed throughout the porous carrier material and the catalytic composite is sulphided prior to contact with the hydrocarbon, by treating the composite with a sulphiding gas at conditions selected to incor- porate O.O~-O.S% S.

Platinum Group Metal on a Support Having Separate Alumina Phase ATLANTIC RICHFIELD co. U.S. Patent 3,937,742 In the hydroformylation of 2-16C olefms a new catalyst consists of O.WI-I% Rh, Ru, Pt or Pd deposited on a Si0,-Al,O, support which has a separate AlaOs phase. The support consists of 4 5 9 5 % amorphous Si0,-A1,03 and 5 3 5 % of a separate phase of A1,0, resulting from the cal- cination of a mixture of amorphous hydrous A1,0, and A1 monohydrate.

Catalyst for Purifying I.C.E. Exhaust JOHNSON MATTHEY & CO. LTD.

US. Patent 3,945,948 A catalyst consists of a mixed oxide obtained by co-precipitating Ru and a base metal as hydrated oxides from a solution of Ru salt and salt of Ti, Zr, Hf, Nb and/or Bi, drying and calcining.

Zinc Aluminate Catalyst Compositions PHILLIPS PETROLEUM CO. u.3. Patent 3,948,808 A catalyst composition consists of Zn aluminate promoted with 0.05-20%, calculated as the metal, of at least one of Pt, Pd, Ir, Re, Ni, Cu, Bi, Mn and Ce or La, and is used in the purification of organically polluted water.


1 to 20% Rh-Pt Catalysts JOHNSON MATTHEY & CO. LTD.

U.S. Patent 3,951,860 A catalyst consists of an inert porous refractory ceramic material such as zircon-mullite, mullite, a-Al,O,, in the form of a corrugated cellular honeycomb which is coated with a layer or deposit of a mixture of two catalytically active refractory metal oxides. The first of the oxides is an oxide of Be, Mg, B, Al, Si, Ti, Zr, Hf and/or T h and the second is an oxide of Sc, Y and/or a lanthanide. A second coating consisting of a mixture of Pt and 1-20% Rh is applied to the refractory oxide coating. The catalyst is particularly useful in the vapour phase oxidation of CO and the lower hydrocarbons.

Hydrocarbon Conversion Catalyst UNIVERSAL OIL PRODUCTS CO.

U.S. Patent 3,951,868 A conversion catalyst consists of a porous carrier material containing 0.01-2% Pt group metal, 0.1-3.576 halogen, 0.01-57/0 Ge or Sn and In in an amount sufficient to result in an atomic ratio of In to Pt group metal of about 0.1 : I to about I : I. A typical catalyst contains 0.3750:;1 Pt, 0.22% In, 0.5% Sn and 1.07; combined chloride. The atomic ratio Sn : Pt is 2.19 : I and of In : Pt is I : I. The catalyst may be used for reforming naphtha.

Hydrocarbon Conversion Catalysts EXXON RESEARCH & ENGINEERING CO.

US. Patent 3,953,368 Useful hydrocarbon conversion catalysts consist of I r and at least one other metal, preferably Pt, in the form of highly dispersed polymetallic clusters on a refractory support.

Hydrocarbon Conversion Catalyst STE. FRANCAISE DES PRODUITS POUR CATALYSE

French Appl. 2,268,558 A high strength, abrasion resistant catalyst for hydro conversion reactions, especially isomerisation and dehydrocyclisation reactions, consists of a support such as A1,0,, a Pt group metal or metals and a pair of metals selected from Mn/Ge, Mn/Sn and Ge/Sn. A halogen is also preferably present. In one example Alsoa carrying 0.4% Mn, o.35y0Pt, 0.5”/0 Ge and 1.05y6 C1 is used.

Hydrodealkylation Catalyst INSTITUT FRANCAIS DU PETROLE

French Appl. 2,268,772 The hydrodealkylation of alkyl aromatic compounds is catalysed by a supported mixture of 0.05-50/0 Pt group metal, Co and/or Ni and 0.05-

of Au, Ag, Cu, a lanthanide, Ti, Hf, Nb and/ or Ta. Also3-supported mixtures of 0.4y0 I r and 0.5% Au or 0.4% Rh and 0.5% Eu are used in one example for benzene production from alkyl benzenes.

Ruthenium Containing Catalyst FORD FRANCE S.A. French Appl. 2,274,352 Finely divided Ru is fixed on a catalyst by preparing an acid solution containing at least two materials at least one of which is a product which contains Ru and a lanthanide which can be used with the active material in an oxidising atmosphere to form a non-oxidising, non-volatile and heat-stable compound and precipitating the two materials from a solution on to the substrate which forms the support.

HOMOGENEOUS CATALYSIS Vinylation of Aromatic Compounds UNIVERSAL OIL PRODUCTS CO.

U.S. Patent 3,936,473 A coumarin is produced from a hydroxylic aromatic compound by vinylation in the presence of a Pt group metal or Cu acetylacetonate or carboxylate. A preferred catalyst system consists of Pt acetylacetonate, cupric propionate, pro- pionic acid and air.

Transition Metal Carboxylates JOHNSON MATTHEY & CO. LTD.

U.S. Patent 3 ,939~ 19 A process for homogeneous, liquid-phase, hydrogenation reactions uses, as catalyst, a cation of a Pt group metal, Mo, Cr, Cu or Re which may be complexed with carboxylate, thiocarboxylate or dithiocarboxylate groups, such as a protonated Ru acetate. The metal complex may be prepared from a metal carboxylate salt, optionally stabilised, and a strong acid.

Production of Aromatic Primary Amines MONSANTO GO. U.S. Patent 3,944,615 Aromatic primary amines are prepared by reduc- ing an aromatic nitro compound with CO and water in the presence of a basic N containing compound, tertiary amine or an amide, and a Rh catalyst selected from Rh oxide, Rh hydroxide, a Rh carbonyl compound and a Rh salt which forms a Rh carbonyl compound under reduction conditions.

Iridium Carbonyl Complexes MONSANTO CO. U.S. Patent 3,948,962 New hydrocarboxylation catalysts are Ir carbony1 halide complexes of MR,, where M is P, As, Bi or Sb and R is I-2oC alkyl, alkoxy, aryl or aryloxy, such as IrBr(CO), (PPh,).

Carbonylation of Olefins and Acetylenes IMPERIAL CHEMICAL 1NI)USTRIES LTD.

U.S. Patenr 3,952,034 Olefins and acetylenes are carbonylated using a homogeneous catalyst containing Pd and Fe or a Group IVA, VA or IIIB element as a mutual complex or a simple mixture. In one example a


phosphino-Pd-Fe carbonyl complex is used and in another example a bis(tripheny1 phosphine) Pd chloride-ferric chloride mixture.

GLASS TECHNOLOGY Producing Decorated Glass-ceramic Surfaces P.P.G. INDUSTRIES INC. British Patent 1,436,040 A glass-ceramic article containing less than 0.02% As oxide and Sb oxide is decorated by contact with a material containing molten Sn so that the Sn penetrates at least 5 pm into the surface of the article. A stain decorating composition including a colourant selected from compounds of Pt, Pd, Ag or Au, is applied to portions of the surface of the article. The article is heated causing the colourant to penetrate the surface.

ELECTRICAL AND ELECTRONIC ENGINEERING Plastic-packed Semiconductor Device R.C.A. CORP. British Patent 1,442,881 The conductors in a p-n junction semiconductor consist of a layer of Ti, a layer of Pt or Pd, a layer of Au and a SiO, protective coating.

Multi-layer Capacitor P. R. MALLORY & co. INC. British Patent 1,444,380 The capacitor consists of a body including a number of layers of material which has been formed by rolling from powdered ceramic material, and Pd, Pt, Au and Ag electrode layers between and contiguous with the ceramic layers. Metallic termination layers of the same metals are formed on the body surface.

Schottky Barrier Diode Semiconductor SIGNETICS CORP. U.S. Patent 3,938,243 In a method for fabricating a Schottky barrier diode semiconductor structure, Si semiconductor body ohmic contacts are formed from a ternary alloy of approximately 50% Si, 37.5-45 76 Ni and 5-12.5% Pt. The relative amounts of Ni and Pt in the alloy are adjusted to provide a predetermined barrier height in the range of approximately 0.64-0.835 eV.

Powder Compositions of Polynary Oxides and Copper E. I. DU PONT DE NEMOURS & CO.

U.S. Patent 3,950,597 Resistors are formed on dielectrics from powders of conductive polynary oxides with a pyrochlore crystal structure. The oxides have the formula MxMe-xM”,O,-, where M is Ag and/or Cu, M‘ is Bi used alone or mixed with Cd, Pb, Y, TI, In or a lanthanide, M” is Ru and/or Ir or their mixtures with Pt, T i and/or Rh, x is 0.1-0.6 and z is 0.1-1.0.


Resistance Element S I E m N S A.G. German Offen. 2,446,606 A protected resistance element has a resistance path of Pt-Au alloy applied to the inside of a hollow tube of insulator.

Liquid Metal Connector JOHNSON MATTHEY & CO. LTD.

German Offen. 2,542,582 Current is supplied to a vessel filled with con- ducting material, such as molten glass, by means of a fin which enters the vessel but is not rigidly attached to it. The other end of the fin is linked to a second filled container attached to a current source. The fin conductor is a Pt group metal, Au, Ag, Cu, A1 or their alloys.

TEMPERATURE MEASUREMENT Electrical Accumulators Having Tempera- ture Indicating Means

A battery has visible means for indicating when a given temperature differing from ambient temperature has been reached. The visible indicator is Ag-Hg iodide or Ag-Cu-Hg iodide combined in a coil of blue asbestos cloth catalysed with Pd and made H,O repellent.

High Temperature Sensing Elements SIEMENS A.G. British Patent 1,441,739 A high temperature sensing element consists of a hot conductor installed in a gas- and liquid-tight quartz housing containing an oxidising atmosphere. Current is supplied by P t supply lines.

VARTA BATTERIE A.G. British Patent 1,437,752

MEDICAL USES Plastics Article for Use with Biological Tissue DEVEX S.A. British Patent 1,441,627 The article is, for example, a surgical implant for use in prolonged contact with biological tissue and consists of a transparent body of plastics material, at least part of the surface having a transparent film of Ag, Au, Rh, Pt or Pd on it.

Dental Gold Alloys W. C. HwAmTS G.m.b.H. German Offen. 2,441,360 Au alloys particularly suitable for firing on to porcelain contain 20-30% Pd, r~-zs% Ag, 2.5-5% Sn, O.O~-O.~% Ir, 0.05-0.5”/0 Ru, 0.05-0.5% Cu, 0.1-2% In, remainder Au.

Copper-free Dental Gold Alloy DEUTSCHE GOLD- & SILBER-SCHEIDEANSTALT

Gerfnan Offen. 2,453,799 An alloy for crowns and bridges contains 25-40% Ag, 40-60% Au, 5--20% Pd, 0.05-0.5% Ir, 0-6% In, -6% Sn and 0-27; Zn.

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UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their applications in industry

V O L . 2 0 A P R I L 1 9 7 6 NO. 2

Contents

Sulphate Emissions from Automobile Exhaust

Palladium Alloys for Electrical Contacts

Coating Methods for Use with the Platinum Metals

Russian Research on the Platinum Group Metals

Hydrogen in Palladium

Carboxylato Complexes of the Platinum Group Metals

Abstracts

New Patents

38

44

48

53

54

54

64

69

Communications should be addrmsed to The Editor, Pkrtinum M& R&w

Johnson Matthey & Co Limited, Hatton Garden, London EClN 8EE

Mardaleishvili, R. E.

Moiseev, D. P. Montreuil, C. N. Morabito, J. M. Morcos, I. Mottola, H. A. Moyer, R. 0. Mozgin, V. V. Mozhaiko, V. N. Mrk, R. Muller, V. Murrell, L. L. Mushenko, D. V. Musket, R. G. Myagkova, A. A. Mydosh, J. A.

Nazarova, L. A. Nelson, J. H. Nicholas, D. M.

Martyshkina, L. E. 103 Mashkina, A. V. 67 iMashkova, L. P. I34 Masters, C. 28 Masterson, I?. B. 132 Mathieu, M.-V. 30 Matijevii., E. 11 Mayne, J. E. 0. 30 Meek, R. L. 66, 133 Mentzer, E. 65 Merrill, R. P. 100 Meschter, P. J. 85 Messmer, R. P. 21 Metham, T. N. 65 Michel, K. W. 133 Million, B. 64

Mitchell, R. W. 104 Mladejovsky, M. C. 68

21

104 100 66

102 28 64

134 29 26

Mills, D. J. 30

Page Pacia, N. 100 Pandolfi, L. J. 104 Papaconstantoponlos,

D. A. 26 Parker, J. M. 68 Patei, C. I(. N. 67 Paul, A. 68 Pertici, P. 29 PCter, A. 134 Phiipott, J. E. 110 Pilipenko, A. T. 66 Pintchovski, P. 131 Pletcher, D. 131 Polikarpov, V. A. 30 Pollitzer, E. L. 2 Polyakova, V. P. 53, 99 Ponec, V. 131 Poshkute, Z. A. 134 Poskanzer, A. L. 11 Potts, L. W. 29 Primet, M. 30

Quinn, T. J. 10 Quitana, C. 100

Rabinovich, G. L. 3 1, 134 Rade, H. S. 65 Raevskaya, M. 1'. 65

Rasmnssen, P. G. 28 Rainen, L. C. 105

Page

Sangcr, A. R. 65 Sarachik, M. P. 65 Sarkissian, B. V. B. 65 Sato, M. 64 Savitskii, E. M. 53, 99 Saxena, S. C. 133 Schaudt, G. 133 Schmid-Martii., S. 25 Scgat, J. A. 66 Selman, G. L. 86 Semenova, A. D. 100 Semenova, E. L, 27 Setsune, J. 65 Shashkov, 0. D. 25 Shiotani, A. 135 Shirasaki, T. 31 Shivaraman, M. S. 67 Shpiro, E. S. 104 Shutt, E. 38 Simpson, R. 102 Sinfelt, J. H. 114 Singh, H. S. 32 Singh, S. P. 32 Smorodinskaya, ZH.

YA. 131 Smutek, M. 25 Snab, Y. T. 103 Snodin, P. R. 133 Sobkowski, J. 29 Sokol'skaya, A. M. 103 Sokol'skii, D. V.

6Q In?

Page Togano, K. 26, 65 Tomashov, N. D. 102 Torfs, E. 64 Touger, J. S. 65 Tressaud, A. 131 Triaci, W. E. 132 Trimble, L. E. 31 Tsang, Y. W. 131 Tseung, A. C. C.

29, 102 Tsybulevskii, A. M.

104

Usov, YU. N. 67 Ustinova, T. S. 104

Valyaeva, V. A. 68 Van Dongen, J. P. C. M. 28

Van Landuyt, J. 64 Van Schaik, J. R. H. 30

Vcdcnyapin, A. A. 32 Vcrstnyft, A. W. 28 Vinogradov, S. I. 66 Vitulli, G. 29

Voorboeve, R. J. W. 31, 67

Vorontsov, E. S. 67 Vshivtsev, V. 1. 27

Vassie, P. R. 102

Vlasov, V. M. 100

I,", ."" 104 Rattray, A. D. 132 Somorjai, G. A. 134 Raub, C. J. 79 103, 131 Waff, H. S. 133 101 Raub,E. lo1 Sosinsky, B. A. 29 Wandelt, K. 101

12 Wang,D.K.W. 32 20 Reinacher, G. 8, 68 sDerner. F. 25

132 28

103 Nishiguchi, T. 103, 105 Nolte, M. J. 28 Nowakowski, T. 101

Obermann. A. 102 Ogoshi, H. 65 Onions, A. 32 Orioli, P. L. 21 Orisheva, R. M. 25 Oser, P. 38 Osterreicher, H. 64

Otto, K. 104 Ott, D. 79

Reith, T. M. Rekova, L. P. Robbins, C. G. Robinson, S. D. Rochon, F. D. Roggen, F. Rony, P. R. Roshan, N. R. Roth, J. A. Roth, J. F. Rozovskii, G. I. Rnsalina, L. V.

9 64 26 56 27

122 31 99 68 31

134 103

Sabadie, S. 134 Salahub, D. R. 27 Saltich, J. 105 Sanchez-Delgado, R. A.

105

I ,

Sprintschnik, G. Sprintschnik, H. Steele, M. C. Stephan, J. J. Strukov, V. M. Sutin, N. Sverdlova, A. L. Swofford, H. S. Syutkina, V. I. Szafranski, A. W.

123 123 135 131 67

101

31 29 25 67


Tachikawa, K. 26, 65 Tagirov, V. K. 27, 132 Tanaka, K. 32 Taubc, XI. 29 Tauster, S. J. 104 Terry, L. E. 105 Thompson, J. S. 28

Whitten, D. G. Wieckowski, A. Williams, A. J. Wise, H. Wong, E. H. S. Wood, B. J. Worrell, W. L. Wiihl, H.

Yamamoto, K. Yanin, V. C. Yurtaeva, V. K.

Zenkov, V. S. Zcntko, A. Zhanabaev, B. Zubanova, L. G. Zuman, P.

123 29 26 64

102 64 85 26

134 66 65

31 64

103 67 11

SUBJECT INDEX TO VOLUME 20

a= abstract Page Book Review, Physical Metallurgy of the Platinum

Metals 99 Temperature Measurement 1975 10

Catalysts, continuous replacement of 2 polymetallic cluster 114

olefins over, a 103 IrCL, reactions of amines with buta-1,

3-diene and isoprene in the presence ~

Iridium, IrCla, H, transfer from amines to

-L- - u1, u complexes, rrans-IrCI(CO)(PPh,) 2,

conversion of acyl chlorides and triethylsilane over, a

skeleton, structure of, a Iridium-Platinum, skeleton, structure of, a Ir/Al,Oa, for automotive NOx and CO

control, a

J L

68 100 100

104 Osmium, complexes, OsO,, oxidation of

2-propanol and 1-propanol over, a 32

periodate over, a 134 Os-Pd/Al,Oa, hydrogenation of hexene-l

over, a 68 Palladium, black, H, transfer from amines to

olefins over, a 103 complexes, dehydrogenation of diphenyl

ethers over, a 135 complexes, hydrogenation of

dimethylethynylcarbinol on, a 27 complexes, cis-PdCla(PPh,)a, conversion

of acvl chlorides and triethvlsilane

compounds, oxidation of Cu(1I) with

over, a complexes, (NH,),PdCl,, H a transfer

from amines to olefins over, a com lexes Pds(CO),(PPhr),,

Pck!O($Ph ) -, carboxymethylation of organic halides on, a

complexes, PdC1,(PPh3) I, carboxymethylation of organic halides on, a

dispersed, propene oxidation over, a NHs oxidation over, activity and

selectivity of, a oxidation of CO and hydrocarbons

over, tetraethyllead and lead scavengers, a

reduction of MOO, with H over, a Palladium-Gold, dispersed, propene

oxidation over, a surface composition of, a

Palladium-Rhodium, dehydrogenation of cyclohexane over, surface layer composition of, a

Palladium-Silver, surface composition of, a Palladium-Tin, colloidal, for electroless Cu

plating, a Pd/Al20,, hydrogenation of

2,5-dihydrothiophene sulphone over, stability of, a

Pd/asbestos, H, transfer from amines to olefins over, a

Pd/C, catalytic hydrogenation over, influence of metal-carrier ratio of solvents and acidity, a

Ha transfer from amines to olefins

68

103

32

32 134

67

104 31

134 64

104 64

66

67

103

103

over, a 103 Pd/support, isomerisation of cyclododecane

epoxide over, a 134 Platinum Group Metals, polymetallic cluster 114 Platinum, black, hydrogenation of eugenol

over, a 103 black, oxidation of monocrystalline

Si over, a

over, a catalytic activity of, oxidation of CO

Platinum MetalRev., 1976, 20,(4), 141-144

67

31

Catalysts (contd) Page complexes, carbonylation of olefins

over, a 104 complexes, hydrosilylation of ketones

over, a 134 complexes, cis-PtCI ,(PPh ,),, conversion

of acvl chlorides and triethvlsilane over, a

gas over, a

structure and activity of, a

selectivity of, a

over, influence of tetraethyllead and lead scavengers, a

over

over, a

over, a

fibre, oxidation of automobile exhaust

hydrocarbon reactions over, surface

NHs oxidation over, activity and

oxidation of CO and hydrocarbons

production of gasoline and hydrogen

reduction of NO for HCN production

skeleton, hydrogenation of nitroethane

skeleton, structure of, a Platinum-Iridium, skeleton, structure of, a Platinum-Rhodium, skeleton, hydrogenation

Platinum-Tin, complex, catalytic activity

Pt/Al,Os, Cu impregnation of, a gas- and liquid-phase hydrogenation

of acetone over, a hydrogenation of nitrobenzene over,

effect of heat treatment on, a interaction between aromatic

hydrocarbons, and, a stabilitv in relauon to N comoounds

of nitroethane over, a

of, a

68

103

I03

67

104

2

67

31 100 100

31

I32 30

103

103

30

of, n 30 67

aromatic hydrocarbons over, a 104 Pt-Au/support, n-pentane and n-hexane

reactions over, a 30 Pt-Re/A1,OI, reduction by H, of, a 30 Pt-Sn/Al,O characterisation of, n 30 Pt!C, catalytic hydrogenation over,

influence of metal-carrier ratio of solvents and acidity, a 103

Pt/CoaOd, promoted, ammonia oxidation over, a 134

Pticordierite, reduction of NO for HCN production over, a 61

Pt/ion exchange resins, activity of hydrogenation reactions over, a 134

PtlMnO,. Dromoted. ammonia oxidation

thiophene and pyridine poisoning of, a with C1 additions, hydrogenation of

-, - over, a

waste gases over

over, catalytic activity of, a

over, activity of, a

and Mo ions in, a

over, a

over, a

Pt/Nichrome, purification of industrial

Pt/polyamide 66, hydrogenation of styrene

Pt/Si0,-Ale03, isomerisation of n-hexane

Pt/support, interaction between Pt atoms

Pt/VaOs, promoted, ammonia oxidation

Pt/zeolite, hydrocracking of n-octane

n-pentane and n-hexane reactions over,

134

20

30

103

30 a 30

134

104

Rhodium, alkane and cycloalkane reactions on, a 134

black, chemisorption of O 1 and CO on, determination of surface area of, (I 31

complexes, carboxylation of methanol to acetic acid over, a 104

complexes, Rh(CO),CI 2, isomerisation of phenylcyclopropanes over, ( I 68

141

Catalysts (contd) Page complexes, (CO,B),,RhH,,

hydrogenation, hydrogenolysis and methanation of cis-but-2-ene over, a

complcxes, (NilB),,RhHlr, hydrogenation, hydrogenolysis and methanation of cis-but-2-ene over, a 104

complexes, RhCl, reactions of amines with buta-1,3-diene and isoprene over, a 32

complexes, RhH(PPh*),, HI transfer from amines to olefins over, a 103

complexes, RhC1,.2H20, H z transfer from amines to olefins over, a 103

complexes, RhCls.3H20, isomerisation of n-butenc on, a 32

skeleton, hydrogenation of nitroethane over. a 31

reactions on, a 134

104

Rhodium-Copper, alkane and cycloalkane

Rhodium-Gold. alkane and cycloalkane reactions on, a 134

Rhodium-Palladium, dehydrogenation of cyclohexane over, surface layer composition of, a 104

of nitroethane over, a 31

reactions on, Q 134

Rhodium-Platinum, skeleton, hydrogenation

Rhodium-Tin, alkane and cycloalkane

Rh/AI,O,, chemisorption of Oa and CO on, determination of surface area of, a

transformations of cyclohexane with 31

HaO vapour on, u 134 Rh/Y-AlaOa, state of Rh in, Q 31

transformations of methvlcyclohexane with HsO vapour ove;, a 134

CO on. determination of surface area of. n 31 Rh/Al,O,-SiO,, chemisorption of 0, and

RhE, caialytic hydrogenation over, influence of metal-carrier ratio of solvents and acidity, a 103

31 =/ion exchange resins! activity of

hydrogenation reactions over, a 134 Rh/SiO,, chemisorption of 0% and CO on,

determination of surface area of, a 31 Rh/support, activity of, a 31

isomerisation of cyclododecane epoxide over, a 134

Ruthenium, complexes, chiral phosphine, hydrogenation of unsaturated carboxylic acids over, a 32

complexes, bydroformylation of alkenes over, a 105

complexes, RuCl,(PPh,) J, conversion of acyl chlorides and triethylsilane

chemisorption of O 2 and CO on, determination of surface area of, a

over, a 68

from amines to olefins over, a 103

from organic compounds to aldehydes

complexes, RuCL(PPh,) I, H e transfer

complexes, RuHa(PPhs),, H a transfer

and ketones over, k 105 31

salts, dehydrogenation of cyclohexane over, a 31

hydrogenation of acetoacetate ester over, a 32

dehydrogenation of cyclohexane over, a 31

dimethylethynylcarbinol over, selectivity and activity of, a 68

126

Glasgow, catalysis 96

in metals 54

Ru/AlsOl, reduction of NO over, a Ru/graphite, promoted by alkali metal

RujSiO,, modified by tartaric acid,

promoted by alkali metal salts,

Ru-Pd/TiOe, hydrogenation of

Chernyaev, I. I., research on platinum metals Chlorine Production, review of 120 Conference, Annual Congress Chemical Society,

Chemical Society, Birmingham, hydrogen

Conference (contd) Chemical Society, Nottingham, surface

Holm Seminar, Chicago, electrical contacts Sixth International Congress on Catalysis,

Society of Chemical Industry, London,

reactivity and catalysis

London

chlorine production

tarnishing characteristics of, Electrical Contacts, Palladium-Silver,

Ruthenium, electrodeposits for, a TaPt-Ta-Au, reactions with PtSi ohmic

contacts, a Electrodes, Iridium, cathode, in hot ionisation

gauge, a Iridium-Iridium Oxides, e.m.f.

Page

91 46

124

120

46 1 02

32

133

measurements of, a 133

underpotential at, a 102 Palladium, black, H overpotential and

Palladium-Silver. H overpotential and underpotential at, a 102

Palladium-Platinum, H overpotential and . . .


underpotential at, a 102 Platinum, adsorption and oxidation of

formic acid on, a 29 anodic oxidation of Hn on, a 29 black, teflon bonded, H p evolution in, a 102 conductivity cell, for molten glasses, a 133 construction of, a 102 in electrochemical photocell for H,

production under sunlight, a 66 medical use, for “braille” reading, a 68 on glass substratc, for conductivity and

oxidation of CO adsorbed on, a Platinum-Hydrogen, kinetics of, in eutectic

Platinum-Palladium, H overpotential and

Platinum-Platinum Oxide, e.m.f.

Rhodium-Rhodium Oxide, e.m.f.

Ruthenium-Titanium, preparation of

Electrodeposition of, Osmium? novel method of Palladium, electrocatalytic activity toward

on pyrolytic graphite, electrocatalytic activity toward 0 reduction of, a

permittivity measurements, a 102 131

melt, a 132

underpotential at, a 102



chlorates on, a 29 130

0 reduction of, a 66

66 Palladium-Manganese, on Pt and C

electrodes, microhardness and wear resistance, a 66

Platinum Group Metals, comparison of 133 102

11

chemistry of, a 133

68 68

. . properties, u

Ruthenium, for electrical contacts, a Electroless Plating, sensitisation and activation

of plastics by PdCI,/SnCla before Palladium-Tin, sensitising, colloid,

Glass, corrosion of Pt-Rh alloy by, a solubility of Rh and Pt-Rh alloys in, n

History, Platinum Metals, I. I. Chernyaev’s research 126

Gustav Magnus, Green Salt 21 Hydrogen, generator 110

production, by solar energy 66, 123 separator 92

28 complexes, crystal structure of, molecular

Iridimn, complexes, crystal structure of, a

geometry of, a 28 28 complexes, hydrido transfer from, 4

complexes, IrH2(BH,)L, structure and properties of, a 65

compounds, IrOl, thermal dissociation of, a 132 compounds. KIrO,, preparation and crvstal -. ~ -

stiucture ‘of, a . 65 132 films, thin ethylene hydrogenation on, a

Iridium (contd) Page foils, hydrogenolysis, isomerisation,

dehydrocyclisation on, a 131 reactions with HCIOa, a 66 ternary oxides with Ti and Ca,

semiconductivity in, magnetic and electrical properties of, a 101

thermoelectric power, of, a 65

power of, a 65 Iridium-Zirconium, superconductivity in, a 27

hydrogen separator 92

hafnium, high-temperature containers, a 67

Indium Alloys, Iridium-Iron, thermoelectric

Laboratory Apparatus, Palladium-Silver,

Platinum, intermetallic compound of

supersonic O2 beam, reactive scattering experiments with, a 133

21 Mars, Palladium-Silver Separator on 92

12

Magnus, Gustav, his Green Salt

Nitric Acid, gauzes for production of

Osmium, complexes, ammine, preparation of, properties of, a 29

complexes, preparation and characterisation of, a 66

complexes, tris(2,2’-bipyridine),

electrodeposi tion 130 photogalvanic effects in, a 101

Palladium, additions to Cr of, improvement of

catalytic determination of, in reduction of

complexes, equilibrium energetics of

complexes, with phosphorus ligands, a compound, Pu,Pd,, crystal structure of, a films, resistivity minima in, a H*-sensitive, gate MOS capacitor, a solubility of H in, a

Palladium-Cobalt-Silicon, amorphous,

Palladium-Copper-Silver, decomposition and

Palladium-Deuterium, superconductivity,

Palladium-Gallium-Nickel, coexistent

Palladium-Gold, thin films, diffusion

Palladium-Helium, heat conductivity of, a Palladium-Hydrogen, critical - poin t

corrosion resistance, a 102 135

dyes, a 102

addition of, sintering of W,. a

cis-trans isomerisation for, a 28 132 131 135 135 25

54

magnetic susccptibility of, a 64

ordering in, a 25

tunnelling in, a 26

phases in, a 26

67

25 effects of contamination, a 101 heat conductivity of, a 67 residual resistivity of, a 26 superconducting, specific heat,

electrical resistance of, a 101 superconductivity in, a 26

Palladium-Indium, heat capacitics of, a 26 Palladium-Iron-Silicon, amorphous, magnetic

susceptibility of, a 64 Palladium-Molsbdenum-Niobium, effect of

H 2 on transition temperature of, a 26 Palladium-Nickel, oGdation of, electron

Palladium-Nickel-Aluminium,. magnetic properties of, electrical resistivity of, a 64

Palladium-Niobium, effect of Hz on transition temperature of, a 26

Palladium-Niobium-Tungsten, effect of Hz on transition temperature of. a 26

Palladium-Platinum, liquid, surface tension and density of, a 100

Palladium-Silver, hydrogen separator 92 meteorology, production of H, through 110

Palladium Alloys, hydrogen in, review of

mechanism in, a 100

behaviour of H , in, a

spectroscopic studies, a 101

Palladium Alloys (conrd) I Palladium-Thorium, hydride formation and

superconductivity in hyd4des of, a Palladium-Tin, heat capacities of, a Palladium-Titanium- Aluminium-Niobium-

Tantalum, environmental cracking resistance of, a

Palladium-Vanadium, absorption of H f by, a Palladium-Yttrium, H diffusion membrane

of, dilatometric measurements of, a Platinum, adsorption of gases on, a

adsorption of H1 on, a adsorption of NO and CO on, p complexes, hydrides, carbencs, isocyanidc

complexes, with phosphorus ligands, a complexes, [Pt(NH,)nl[PtClrl, discovery of complexes, [Pt(NH,)&I,, on the

photolysis of, a complexes, acyl- and sulphonato-,

preparation of, a complexes, n-allylplatinum(II), novel

method of preparation of, a complexes, cryst.al and molecular structure

of, a complexes, hydrido transfer from, a complexes, isomerisation of, a complexes, metal-C bonds, a complexes, mononucleoside, a complexes, silylplatinum, preparation of, a compounds, diiodine-bis(diethylsu1phide)

platinum(II), reaction with NHI, (2 compounds, K,Pt(CN),Bro.8.3H,0,

electronic structure of, a compounds, HfPtr, HfPts, melting points

and stability of, high temperature applications of, a

compounds, (H,O),. 6[Pt(C,0,)31nH,0, conduction properties of magnetic susceptibility of, a

compounds, PtlrPtIvF,, crystal structure of, a

effect of 0% on the thermionic emission of impurity ions from, a

electroetching of, in Ti-Pt-Au metallisation,

films. calorimetric heats of adsoration of

insertion into, a

a

H ~ ’ on, u films, diffusion of ALI through, a films, epitaxial growth of, structure of, a films. thermal desorotion of CO from. a films; thin, sputtering of, a foils, hydrogcnolysis, isomerisation,

dehydrocyclisation on, a interaction of 0, with, a oxidation of H, on, a resistance of polymeric films supported on, L stepped surfaces, steric properties of, a

Platinum Alloys, Platinum-Aluminium, intermetallic compounds of, a

sub-solidus equilibria in, a Platinum-Copper, ordering mechanism in, a Platinum-Gallium, intermetallic compounds

Platinum-Gallium-Nickel, coexistent phases

Platinum-Gold, films, thermal desorption of

Platinum-Indium, intermetallic compounds

Platinum-Iron, diffusion of Pt in, a Platinum-Palladium, liquid, surface tension

Platinum-Rhodium, dispersion-strengthened,

of, a

in, a

CO from, a

of, a

and density of, a

high-temperature applications of effect of Pd on propcrties of gauzes for NH, oxidation wire loops, conductivity of silicate

melts with, a

and density of, a Platinum-Silicon, liquid, surface tension

’age

64 26

26 101

101 131 100 25

132 132 21

25

27

102

27 28 21 28 27 65

68

21

61

65

131

64

135

25 100 131 131 32

131 100 100

1 30 131

I00 25 64

100

26

131

100 64

100

86 8

12

133

100


Platinum Alloys (contd) Page

thermodynamic properties of 85

Platinum Metals, affinity for refractory oxides of 79 carboxylato complexes of, recent

developments in 56 Chernyaev’s research on 126 coating methods for, a review of 48 ductility enhancement in Group Vla

elements by 7 for chemisorption studies, meeting on 91 in catalysis, symposium on 96, 124 physical metallurgy of 99 purification, production of singlc crystals of 9 Russian research on 53 sputtering of, high rate 94

9

Platinum-Titanium, high-temperature

Platinum Silicide, thin films, propcrties of

Pollution Control, Automobile exhaust gases, hydrogen cyanide production, resulting from, a

influence of tetraethyllcad and lead

iridium catalysed, a oxidation by fibre supported catalysts, a research on sulphate emissions, level of Industrial waste gases, purification of

scavengers, a

Research Centre, the ncw Johnson Matthcy

Rhodium, complexes, dimeric, metal-metal bond, preparation of, a

cornolexes. RhfII) carboxvlatcs. as ~I

aiti-tumour agents, a complexes, RhCI2(NO)(P(CsH6) J

crystal and molecular structure of, a complexes, RhH %(BH *)L,, structure

and properties of, a complexes, chloro-l,2-bis- (dipheny1phosphino)ethanecarbonyl rhodium(I), structure of,

complexes, crystal structure of, a complexes, mono and dinuclear, a complexes, porphyrin [Rh(C0),ls and

N-alkyl-porphyrin [Rh(CO) ,C1] 1,

preparation of, a RhP,, thermodynamics of gaseous, a

Rhodium Alloys, Rhodium-Gadolinium, of, a

high-temperature applications of effect of Pd on properties of gauzes for NHs oxidation wire loops, conductivity of silicatc

Rhodium-Platinum, dispersion strengthened,

melts with, a


67

104 104 103 74 38 20

14

132

105

28

65

65 28 28

65 26

101

86 8

12

133

Rhodium Alloys (confd) Page Rhodium-Silicon. liauid. surface tension and

density of, a . ’

critical fields of. a Rhodium-Zirconium, noncrystalline, upper

structure and’superconductivity of, CJ

Rhodium Oxides, sesquioxide, thermal

Ruthenium, adsorption of NO and CO on, a

synthesis and properties of, a

dissociation of, a

complexes, 2,1,7-[(PPh,) ,RuH %C ,B,H, ,I, complexes, cyclic dienyl, a complexes, cyclo-olefin, preparation of, a complexes, tctracarbonyl(phosphine)

ruthenium, preparation and properties of, a

complexes, solar energy conversion of H1O to HZ over, photochemical cleavage with

complexes, thermal and light-induced decomposition of, a

complexes, tris(2,2’-bipyridine), photogalvanic effccts in, a

interaction of 1,2,3-benzotriazole with, a reduction in HCI, a

Ruthenium Alloys, Huthenium-Dysprosium, intermetallic phases of, magnetic properties of, a

Ruthenium-Gadolinium, intermetallic phases of; magnctic propcrries of, LI

magnetic ordering in, R

diagrams of, magnetic susceptibility of, a

diagrams of, magnetic susceptibility of, ( I

transtormation of, a

Kuthcuium-Iron, electrical rcsistivity and

Ruthenium-Rhenium-Titanium, phase

Ruthenium-Rhenilun-Vanadiuin, pli?sc

Ruthenium-Uranium, quenching of, phase

Ruthenium Ilydridc, prcparation of, xructure of, propertic,: of, ( I

Ruthenium Oxides, dioxide, thermal dissociation

Solar Energy, Ruthenium Complex,

Temperature Measurement, Platinum Alloys in

Thermocouples, Pt:Rh-Pt, in the casting of Cu

Transistors, Palladium, thin film, detecting

of, a

photochemical cleavage with

Pt resistor, electronic, medical use of, a

alloys

hydrogen in air with, a detecting H, N and Ar in air with, a

144

100

65 26

27

25

102 29 29

66

123

29

101 66 29

101

101

65

65

65

132

28

27

123

10 133

122

135 67

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