PLATINUM METALS REVIEW...ketone (Fig. 4) or di-n-propyl ketone. The following is a very interesting...

PLATINUM METALS REVIEW

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

V O L . 9 A P R I L 1 9 6 5

Gontents

Molecular Models : A Means of Studying Catalytic Hydrogenations

A High Temperature Vacuum Furnace

The Availability of Platinum

Aromatics Production by Platinum Reforming

Phosphine Complexes of the Platinum Group Metals

Hydrogen Recovery by Palladium Diffusion

Reactions of Oxygen with the Platinum Metals

Galvanic Couples with Platinum Metals

The Care and Maintenance of Thermocouples

Electrochemical Hydrogen Purification

Platinum for Resistance Thermometry

Thermal Conductivity of Pure Platinum

Abstracts

New Patents

NO. 2

38

43

45

46

47

50

51

56

57

58

59

60

61

66

Communications should be addressed to The Editor, Platinum Metals Review

Johnson, Matthey & Co., Limited, Hatton Garden, London, E.C.1

Molecular Models: Studying Catalytic

A Means of Hydrogenations

By Morris Freifelder Abbott Laboratories, North Chicago, Illinois

Although in many cases it will not be necessary, the assembly of molecular models can prove extremely valuable in studying certain types of catalytic hydrogenations. They may, for example, help in understanding problems of selectivity when more than one reducible group is present, and they can also show whether poisoning by certain atoms will occur, ofering a possibility of overcoming this by the use of more vigorous conditions or of more catalyst.

To carry out successfully the catalytic hydrogenation of organic compounds contact must be effected between the surface of the catalyst and that portion of the molecule to be reduced. The importance of good contact should be emphasised because not all of the surface is capable of inducing hydrogenation. Reaction takes place only at active centres. Without going into the modus opevandi of catalytic reduction, if the starting material is pure and contact with the catalyst is satisfactory, uptake of hydrogen will proceed more or less readily, unless an intermediate or the final product inhibits the activity of the catalyst used in thc operation.

In many instances, the effect of substituents will be obvious. It should be easy to predict that ring reduction of a-methylpyridine would take place more readily than 2,4,6-trimethyl- pyridine under similar reaction conditions. This is described in the reductions with ruthenium dioxide at 90' and 70 atmospheres pressure (I). Complete conversion to 2-

methylpiperidine was completed in five minutes while the more substituted compound took about 15 hours. One might guess that 1-phenyl-2-aminopropane would be less difficult to hydrogenate than the branched compound 1-(4-isopropylphenyl)-2-aminopropane. The difference in reaction time is

rather striking, 30 minutes against 12 hours at 90' and 70 to 80 atmospheres with ruthenium catalyst (2).

How will the chemist foresee less obvious difficulties, except from experience or perhaps by intuition? How can he get an understanding of why certain hydrogenations will present more problems than others ? Mole- cular models can be of great help. A model of the last mentioned compound would have shown that, on rotation, portions of the ring were often out of contact with the catalyst. This observation could suggest increasing the temperature and pressure to bring about more rapid uptake of hydrogen.

In some instances, the reason for lengthy reaction is not always so obvious. In a series of hydrogenations of some substituted pyri- dines at 55 to 60" and 3 atmospheres pressure in the presence of rhodium on a carbon support, most of the compounds with a single substituent were readily reduced (3). Nico- tinamide was converted to the corresponding piperidine in less than two hours, yet the N,N-diethylamide took 13 hours. It was not a question of purity since the compound had been recrystallised several times before use. I t did not seem likely that the ring nitrogen of the substituted pyridine or piperidine amide would have any greater poisoning power than

Platinum Metals Rev., 1965, 9, (2), 3 8 4 2 38

Fig. 1 Ethyl 2-cyano-2-ethyl- 3-methyl-4-hexenoate: the model shows that it is impossible to get the olefinicgroup in close contaet with the catalyst surface and therefore it cannot be reduced

the corresponding nitrogen atoms of un- substituted amides. From models of the four compounds involved, no apparent difficulty could be envisaged. However, an examination of a model of a partially reduced diethylamide did offer a clue. It appeared that as hydrogens were added, portions of the ring were raised from the surface. It seemed likely that more vigorous conditions were necessary to force the intermediate back into better contact with the catalyst. When reduction was carried out at go" and 70 atmospheres, conversion was complete in about 45 minutes (I).

An examination of models can help one to understand and at times to predict the results of hydrogenating compounds with several reducible groups. The reductions shown below are an illustration (4).

CH, C,H, I I

CH,CH,CH=C - C - CN +> I PtO,

O=COC,H,

In each instance a model of the unsaturated cyano ester made it clear (Fig. I) that the cyano group would make good contact with the catalyst surface and therefore be amenable to conversion to the unsaturated primary and/ or secondary amine. At the same time, it was not possible to manipulate the models to allow the C = C bond to make any contact whatsoever.

On the other hand, a model (shown in Fig. 2) predicted that the following reduction should yield the desired saturated compound :

CH.! I

CH&H2CH,C=C-CN > I PtO*

O=COC,H,

CH, I

CH,CH,CH,CH-CHCN I o-coc,w5

saturatcd cyano ester

I t also showed that conversion to the saturated amine was possible. Indeed, the presence of amine has been noted as a by-product in

I PtO, the hydrogenation of similar compounds (5 ) . The reduction shown above did give a high yield of the saturated cyano ester (4).

CH,CH=C - C - CN -b

O=COC,H,

saturated cyano ester

Platinum Metals Rev., 1965, 9, ( 2 ) 39

In an attempted conversion of dicyclopropyl ketone to the corresponding carbinol, no uptake of hydrogen was observed in the presence of platinum oxide (4). From the model (Fig. 3) it could be seen that the carbonyl group would be out of contact with the catalyst most of the time. When palladium was used in the reduction, 4-heptanol was obtained (4). The rings were undoubtedly ruptured, leaving the carbonyl group in a favourable position on the catalyst so that further reduction would take place. This is evident from models of cyclopropyl n-propyl ketone (Fig. 4) or di-n-propyl ketone.

The following is a very interesting example of the reduction of a ring system in preference to a more readily reducible group, with a

Fig. 2 Ethyl 2-yarn-3- methyl-2-hexenoate: in this compound both the okfinic and nitrile groups are in contact with the catalyst surface and both can be reduced. The olefinic group is selectively reduced before the nitrile

catalyst not generally used for aromatic systems (6):

NO2 I a COC,H, 12 hours

CH,CHCII,CH,

H i

+ R -N0,(48"<) R-NH2(22'/,)

The authors repeated their work with a different lot of catalyst, in another piece of

equipment, and obtained the same results. They reported that they made models which suggested that the terminal methyl group on the side chain prevented reduction of the nitro group because it could occupy only a restricted

Fig. 3 Dicyclopropyl ketone: the Iceto-group will be out of contact with the catalyst surface and this explains the lack of reactivity


Fig. 4 Cyclopropyl n-propyl ketone: opening one of the ryclopropane rings enables the keto-group to haue better contact with the catalyst surface, thus enabling it to be reduced

number of positions. Dup- lication of models by this author showed the aromatic portion of the molecule in good contact with the catalyst, while the nitro group was off in space more often than it was in contact with the catalyst.

When the same authors investigated the hydrogenation of the corresponding nitro- propane under similar conditions, but in a much shorter time, they were able to reduce the nitro group without affecting the ring. A model of the shorter chain compound suggests that less difficulty should be encountered.

Models can often be useful in deciding whether catalytic reduction is feasible in the presence of known poisoning atoms. Maxted has suggested that poisoning of sulphur- containing compounds is due to the unshared electron pairs which allow strong bonding to the catalyst surface, or more pointedly, to the active centres on the surface of the catalyst (7). Nevertheless, it is possible to carry out catalytic reduction of certain groups in the presence of organic sulphides. The literature is full of examples :

Fig. 5 4-nitrophenyl sulphide: the sulphur atom i s so f a r removed from the surface that it cannot art as a catalyst poison

A model of 4-nitrophenyl sulphide shows (Fig. 5 ) that the sulphur atom is sufficiently out of contact with the catalyst to allow reduction to proceed to completion. How- ever, when one of the phenyl rings is removed and an aliphatic side chain is substituted, hydrogenation becomes more difficult. The model of ethyl 4-nitrophenyl sulphide (Fig. 6) suggests that poisoning can occur.

The model of the nitro compound given in the equation overleaf showed (Fig. 7) that the 2-methyl group interfered with contact between the sulphur atom and the catalyst. In view of the theory of active centres, the position of the sulphur atom suggested that


Fig. 6 Ethyl 4-nitrophenyl sulphide: in this molecule the sulphur atom can easily touch the catalyst surface. suggesting that poisoning will occur

might give an insight into selectivity when more than one reducible group is present.

O,N <% SCH,CH,COOC~H, ~3 They could also show whether poisoning by certain atoms would take place and perhaps offer a means of overcoming this by the use of

CH,

/- iCH:; more vigorous conditions or more catalyst or both. Our experience has shown that models

complete poisoning would not take place and that complete conversion could be attained

References

I M. Freifelder and G. R. Stone,.B. O r f . Chem., - - in the presence of a higher than normal

amount of catalyst. Although uptake of SOC., 1958, 80, 5270

1961, 26, 3805 2 M. Freifelder and G. R. Stone,?. Amer. Chem.

hydrogen was slow, it was Complete With a 30 7 M. Freifelder and G. R. Stone, 7. Om. Chem., . -

per cent ratio of catalyst to compound (4). 1962,279 284 4 Unpublished work from this laboratory 5 A. C. Cope, C. M. Hoffman, C. Wyckoff and

E. Hardenbergh, J. A m . Chem. SOC., 1941, 63, 3452, used a dilute acid wash to remove any bases formed by addition of hydrogen to the nitrile grow

The writer does not suggest that models should be studied before every reduction is carried out. There are many times when it will not be necessary. Nevertheless, with a know- - - ledge of other factors in catalytic hydrogena- 6 D. V. Young and H. R. Snyder,.?. Am. Chem. tion, the short time spent in assembling models could prove extremely valuable. They

1961y 83y 3160 7 E. €3. Maxted, Advunces in Catalysis, (Aca-

demic Press, New York), 1951, 3, 129

Fig. 7 Ethyl (Bmethyl-$-nitrophenyl) mercuptopropionate; the methyl group i d c i b i t ~ contact b e t t ~ ~ e n the sulphur atom and the catalyst surfuce and hydrogenation of the nitro- group proceeds, although slowly. ( T h i s model is somewhat ideulised f o r photographic purposes. The sulphur atom is actually closer to the surfuce and the 2-methyl group res- tricts rotation to prevent j i rm attachment of the sulphur to the catalyst)


can be of considerable value.

A High Temperature Vacuum Furnace NEW DESIGN OF PLATINUM ALLOY ELEMENTS

By J. P. Rayner, B.Sc.(Eng.) Furnace Department, Johnson Matthey & Co Limited

One of the largest furnaces to be heated by platinum alloy windings has recently been installed in the Johnson Matthey Research Laboratories. This is a precision-controlled vacuum furnace, for use up to 14oo0C, having a chamber 4 inches in diameter and 28 inches in length. Of this total length, 18 inches - from the back wall to within 10 inches of the front of the chamber - can be maintained at a uniform temperature.

The furnace runs on rails on top of its control cubicle. It may be automatically withdrawn from the vacuum tube by a variable speed motor when slow withdrawal is required, or it may easily be withdrawn manually with the automatic drive declutched. This arrangement was preferred to the more conventional alternative of moving the more delicate vacuum pumping equipment.

The automatic withdrawal system reduces heat treatment cycle times, and thus enables a greater throughput to be obtained. At the end of a soak period the furnace is switched off and withdrawn from the vacuum tube at the maximum speed at which the hot vacuum tube can leave the furnace without suffering thermal shock. By this means the charge is cooled much more rapidly than if it were left in the furnace hot zone and could only follow the natural cooling rate of the furnace. When the charge has reached a temperature at which it will be unaffected, air is admitted into the system and the seal at the head of the vacuum tube is broken, the charge withdrawn and a new charge inserted. The furnace is returned manually to cover the vacuum

tube unless the furnace temperature is too high, when the automatic drive is used.

The long rear zone of the furnace is controlled by a galvanometer type programme controller having an 8-inch scale covering the range o to 1600'C. The platinum:13 per cent rhodium-platinum thermocouple connected to this instrument is located near to the back of the furnace. A thermocouple within the short front winding is connected in series opposition to a reference thermocouple near the back of the furnace, the resultant e.m.f. is fed to a small centre zero galvanometer controller which controls the power to the front winding. With this simple circuit the long level temperature zone is readily obtained and maintained.

Element current is controlled by simple on/off switching of mercury relays. Trans- formers within the control cubicle supply the elements with a maximum of 150 volts. If the elements were run at normal mains voltage there would be a risk that a metallic charge might short circuit the element windings, as the electrical resistance of the vacuum tube wall would be very low at the maximum furnace temperature of 14ooOC. Two four- position transformer tap changing switches enable both the front and back element voltages to be further reduced when the furnace is being used in the lower parts of its temperature range.

To guard against the expensive damage that could occur to either charge or furnace if failure of a component in the main control circuit led to an uncontrolled temperature


The high temperature pla$inum-mound vacuum furnace installed in the Johnson M(z&hey Research Laboratories

rise, an additional simple over-temperature control circuit, quite separate from the main control circuit, is provided. I t consists of a thermocouple, a small o to 1600°C controller, and a contactor which opens to cut off all the power to the furnace when the thermocouple temperature reaches the set point on the controller. The over-temperature controller is usually set 20 to 50°C above the maximum operating temperature.

To indicate the temperature of the charge as distinct from that of the furnace, a thermocouple may be placed within the vacuum tube through a special seal in the vacuum head.

The heating of this large size of furnace by platinum alloy elements has been made possible by the extensive development by Johnson Matthey during recent years of fabricated elements. Previously most platinum alloy elements were made by winding the wire on to fully fired ceramic tubes. Un-

avoidable expansion differences led to stress- ing and fracture of the thin wires at high temperatures, particularly when the tubes were above 2-inch bore. Production of a furnace having 4-inch bore wound tube elements would thus not have been contem- plated.

In the fabricated element the winding wire is buried in the ceramic tube before the tube is fired. Fabricated elements have not only proved to be more reliable than the wound tube type in the smaller sizes, they have been found to be very reliable in the larger sizes. The compactness of the fabricated construc- tion leads to increased thermal efficiency, and the elimination of the fired tube between the winding and the chamber makes possible even faster heating rates.

The thermal efficiency of this furnace is such that the losses at 1400°C amount to only 3 kilowatts.


The Availabilitv of r,

FURTHER EXPANSION IN MINING

The consumption of platinum for industrial purposes continues to rise steadily, while the variety of its uses continues to increase. On several occasions during the past few years specific expansion programmes have been announced by Rustenburg Platinum Mines Limited, each designed to maintain output in balance with demand and to give effect to the declared policy of the mining company and its sole refiners and marketing agents Johnson Matthey & Co Limited to ensure to the best of their ability that platinum shall always be available for use by industrial consumers, and that it shall be available at reasonably steady prices.

The last such announcement, only a year ago, referred to an immediate programme to expand capacity at the mines - already the world's largest producer of platinum - by about 25 per cent. Refined platinum arising from this particular phase of expansion, which will be completed towards the end of 1965,

Platinum ACTIVITY AT RUSTENBURG

will become available in increasing quantities from the last quarter of this year.

However, it has now been considered advisable to provide still further capacity at Rustenburg in order to ensure continuity of supplies at a higher level and to assist in the building up of stocks of metal that will be available at short notice to meet sudden changes in the supply position, should these recur. Capacity is therefore being increased still further, to an extent which will increase 1964 output by 40 per cent instead of the 25 per cent previously planned. This further expansion will be completed during the first half of 1966, and some additional refined platinum arising from this programme will become available towards the end of that year.

The present project includes an accelera- tion of shaft sinking programmes, the further expansion of all the numerous mining facilities required for the higher rate of production,

A train load of platinum ore emerging from the mine at Rustenburg


and a further extension of the reduction works. The total cost involved will exceed Es million, but it is considered that this level of new capital expenditure is essential to Rustenburg’s endeavours to ensure that some surplus capacity is always available, and that stocks of refined platinum are adequate to meet the needs of users as and when these needs arise.

An early stage in the process in the Johnson Matthey smelting plant. Nickel matte, carrying with it the pla.tinum metals, is cast into pigs

It is also expected that the large scale of production upon which Rustenburg is now engaged, and which will con- tinue for so long as it is warranted, will assist ma- terially towards mitigating the effects of inflation upon the cost of production, and by so arresting the otherwise steady increase in production costs it is hoped that it will be

possible to avoid any further increase in the price of platinum for some considerable time to come.

Smelting and refining capacity in the Johnson Matthey plants in the United King- dom, as a result of steady modernisation and improvement, will be adequate to deal with the increased output from Rustenburg.

Aromatics Production by Platinum Reforming LARGE SCALE PLANT DESIGNED FOR BILLINGHAM

The largest aromatics plant of its kind in Europe, having a projected capacity of some 400,000 tons a year, is now in course of con- struction at the Billingham works of Imperial Chemical Industries Limited and will begin production in the latter part of this year.

Six process units licensed by Universal Oil Products Company comprise the new complex, two of them employing platinum catalysts. Light straight-run naphtha feed will be charged to a Unifining plant for desul-

phurisation and then to a Platforming unit for aromatics reforming. An alternative source of aromatics, cracked naphtha, will be hydrogen treated in a Platfining process unit, and the products from both streams will be fed to a Sulfolane unit for the extraction of high purity aromatics.

The use of these two routes will give flexi- bility in the production of aromatics - mainly benzene, toluene, xylenes and cyclohexane - on this large scale.


Phosphine Complexes of the Platinum Group Metals By B. W. Malerbi, M.A. Research Laboratories, Johnson Matthey & Co Limited

Complexes made by reacting the platinum group metals with alkyl or aryl phosphines are of comiderable potential interest. Many of them are soluble in aromatic or polar aliphatic solvents and are already Jinding applications as homogenous catalysts. In this paper the methods available for producing the phosphine complexes are reviewed, and details are given of a range of phosphine stabilised hydrido and phosphine stabilised carbonyl hydrido complexes of the metals, all of which have been produced under controlled conditions and are now available in research quantities.

Just over a hundred years ago Hofmann ( I )

first reported that platinum and gold compounds could be reacted with triethylphos- phine in alcoholic solution to produce phosphine co-ordination complexes. In 1870 Cahours and Gal (2) prepared and character- ised complexes of gold, palladium and platinum with tertiary phosphines and arsines. Progress in this field was slow until the thirties when Mann and Chatt (3) stimu- lated a new interest. This was heightened in the forties and fifties by Hieber (4), Malatesta (5) and Vaska (6). Since then the expansion of effort has been almost explosive, with the result that nearly every possible permutation of ligand and metal has now been prepared.

These phosphine complexes are part of a much larger field of co-ordination complexes in which transition metals are linked to donor atoms or groups of atoms by dative or co- ordinate bonds. Examples of such donor groups of ligands are ammonia, amines, arsines, carbonyls, halogen ions, and olefins.

In co-ordination complexes certain charac- teristic configurations of atoms are common, for example the square planar (Fig. I) and the octahedral (Fig. 2). Less common are the halogen-bridged binuclear species (Figs 3 and 4) and the tetrahedral structure found in some nickel complexes. Of the metals under

consideration here, Pd (11), Pt (II), Rh (I) and Ir (I) complexes have the square-planar form, and Ir (111), Rh (111), Ru (111) and 0 s (11) have an octahedral configuration. Ru (11) and Rh (11) tend to give the bridged structure of Fig. 4.

Most of the platinum metal phosphine complexes known show the structures illustrated in Figs I to 4. In phosphine complexes the ligand, shown in the diagram as R,P, may consist of trialkyl (e.g. Et,P), triaryl (e.g. Ph,P), or mixed alkyl aryl tertiary phosphines such as Et,PhP or EtPh,P.

Several general methods of preparing phosphine complexes of platinum metals are known. The simplest, used by Mann among others, is to stir the metal halide with the tertiary phosphine in ethanol either at room temperature, or with gentle heating up to boiling. Complexes such as PdCl,(PPh,), or RhCl,(PPh,), result. If the boiling is prolonged, especially if higher boiling alcohols such as ethanediol or 2-methoxyethanol are employed, reductive carbonylation or hydride formation will result. As an example, Vaska boiled IrCl, with excess PPh, in 2-( P-methoxyethoxy) ethanol and obtained IrCl(CO)(PPh,),.

A different approach involves carbonylation of the metal halide, followed by addition of

Platinum Metals Rev., 1965, 9, (2), 47-50 47

the phosphine to the metal carbonyl halide. Heck (8) prepared [Rh(CO),Cl], from RhC1, by this method, and then added PPh, to give RhCl(CO)(PPh,),. The iridium analogue IrCl(CO)(PPh,),, prepared by Vaska, on treatment with HCl gas yields the hydrido complex IrHCl,(CO)(PPh,), . Presumably the analogous rhodium compound would react similarly. In preparing a range of ruthenium complexes Chatt (7) utilised the intermediate [Ru,Cl,(PEt,Ph),]+Cl- (prepared by refluxing RuCl, with PEt,Ph in 2-methoxyethanol under nitrogen), and reductively carbonylated it by boiling it with ethanolic potassium hy- droxide to give RuHCl(CO)(PEt,Ph),. In another reaction with [Ru,Cl,(PEt,Ph),]+Cl-, by shaking an ethanol solution with CO at 75°C and 50 atm, Chatt obtained the dicarbonyl complex RuClz(CO),(PEt,Ph),.

Complexing the salts of platinum group metals with phosphines gives them certain

useful properties. The normal salts of these metals are generally not appreciably soluble in organic solvents other than alcohols, and for applications in the field of homogenous catalysis this limits their usefulness. (An exception is the notable reactivity of rhodium trichloride trihydrate in ethanolic solutions; Harrod and Chalk (9) showed that rhodium trichloride in ethanol readily catalysed the isomerisation of hex-I-ene to cis-hex-3-ene.) On the other hand the tertiary phosphine complexes of the platinum metals are usually quite soluble in a wide range of organic solvents. The trialkyl- phosphine derivatives are especially soluble but this causes difficulties in their preparation. A further advantage conferred by the phosphine ligands is the stabilisation of lower, normally unstable, valency states of the platinum metals. If the normal lower valent platinum metal salts, which are very reactive, were used as catalysts there is a danger of their


being reduced to the metal. When associated wirh phosphines this is less likely. The phosphine ligand has been found to stabilise transition metal hydrides which are otherwise unobtainable. Vaska (6) has prepared Ir132Cl(l?Ph3)3 and OsHCl(CO)(PPh,) 3, but simple hydrides of iridium and osmium are unknown. The carbonyl ligand has a similar stabilising effect but it is much weaker. The metal-carbon bond is also strengthened by co-ordinated phosphines, as in the case of

It has been reported by Wilkinson, et al. (10) that the rhodium complex RhCl,(PPh,), has the ability to promote hydrogenation and hydroformylation (the simultaneous addition of CO and H,) of olefins and acetylenes under relatively mild conditions. Hydrogenation of hex-I-ene to n-hexane occurs at 20°C and less than I atmosphere pressure of hydrogen. Hydroformylation of hex-I-ene is effected after twelve hours at 55°C and go atmospheres pressure of a I :I mixture of carbon monoxide and hydrogen. The products are 20 per cent of 2-methylhexanoaldehyde and 70 per cent of n-heptaldehyde. As an aside, it may be noted that Wilkinson (11) reports that ethanolic solutions of RhC1,.3H20 also catalyse the hydrogenation of olefins.

The work of Harrod and Chalk, referred to earlier, suggests that a metal hydride is a likely intermediate in the case of isomerisation and hydrogenation reactions. The fact that some of these complexes are relatively labile in solution in the presence of air would imply that they may also catalyse organic oxidation reactions under relatively mild conditions.

It seems likely, on the basis of our present knowledge of homogeneous catalytic mechanisms, that many applications of hydride complexes of the platinum metals will soon emerge.

For these reasons the preparation of a number of these complexes has been surveyed in the Johnson Matthey Research Labora- tories, and details of seven of the compounds so far prepared are summarised below. All these compounds are now available to potential users in research quantities.

(ECJ')J't(CHd,.

Pt"C,H5)3PJ4 This is made by reacting K,PtCl, with an

excess of triphenylphosphine in a mixture of ethanol and water at 55°C.

The compound consists of orange yellow crystals having a melting point of 120 to 125'C. They are readily soluble in benzene and sparingly so in hrxane. Benzene solutions slowly decompose in air, and on standing in the absence of air, they gradually deposit PtH,[(C,H,),P],. This compound can replace chlorine in CC1, by hydrogen.

PdChC(C8%)3PI 2

This is made by reacting (NH,),PdCI4 with triphenylphosphine in ethanol at 2ooC.

The compound consists of yellow crystals which decompose at around 250°C. The crystals are soluble in benzene, toluene and chloroform and the resulting solutions are stable in air.

I W J [(C$5)3PI 3

This is made by reacting IrC1,.3H20 with an excess of triphenylphosphine in a mixture of ethanediol and water, boiling the mixture for about four hours.

The compound consists of white crystals having a melting point of 195 to 210'C. The crystals are insoluble in alcohol but soluble in carbon tetrachloride or CHC1,; but the solutions are unstable. The solid slowly turns green on exposure to light.

IrHCIdCO) [(C,H,),PI 2

This is made by passing dry HCI gas into an ether suspension of IrC1(CO)[(C,H,),P]2.

The compound is a white crystalline solid having a melting point of 295 to 310°C. It is very sparingly soluble in acetone, chloroform OT benzene.

IrCl(C0) [(C,H,),PI 2

This is made by reacting IrC1,.3H20 with excess of triphenylphosphine in a mixture of methyl digol and water. The mixture is boiled for about two and a half hours.


The compound consists of lemon yellow crystals having a melting point of 315 to 320’C. They are soluble in high boiling alcohols and chloroform.

fRu&I,[(c~H&$],j)’ c1- This is made by reacting RuC1,.3H20 with

an excess of triphenylphosphine in boiling methanol for twenty-four hours.

The compound consists of red-brown crystals having a melting point of 176 to 178°C. The crystals are sparingly soluble in alcohols but readily soluble in acetone, chloroform and benzene. The solutions rapidly change in colour from red to green when exposed to air and the compound is not recry stallisable.

RhC’, [(C,H,),PI 3

This is made by reacting RhC13.3H,0 with a large excess of triphenyl phosphine in ethanol. The solution is brought just to the boiling point and then allowed to cool.

The compound consists of orange red crystals having a melting point of 270 to

280’C. The crystals are soluble in alcohols and benzene, but attempts at recrystallisation result in loss of phosphine.

References I A. W. Hofmann, Ann. Chetn. Liebigs, 1857,

2 A. Cahours and H. Gal, ibid. 1870, 155, 223,

3 F. G. Mann and J. Chatt, J . Chem. SOL. 1938,

4 W. Hieber and H. Heusinger,?. Znorg. Nucl.

5 L. Malatesta et al,J. Chem. Sac., 1955, p, 3924; 1958, 2323; 1963, 2080; J. Inorg. Nucl. Chem., 1958, 8, 561

6 L. Vaska et a1,J. Amer. Chem. Sac., 1960, 82, 1263; 196r, 831 756, 1262, 2784; 1962, 84,

7 (a) J. Chatt and R. G. Hayter,J. Chem. SOL.,

(b) J. Chatt and B. L. Shaw, Chem. Ind., 1960,

(c) J. Chatt, B. L. Shaw, A. E. Field,J. Chem.

8 R.F. Heck, J . Amer. Chem. Soc., 1964~86,2796 9 J. F. Harrod and A. J. Chalk,?. Amer. Chem.

Sac., 1964, 86, 1776 10 J, A. Osborn, G. Wilkinson, J. F. Young,

Chem. Communications, 1965, 17 11 R. D. Gillard, J. A. Osborn, R. B. Stockwell,

G. Wilkinson, Proc. Chem. Soc., 1964, 284

103,357

355

p. 1949,2086; 1939,p. 1622

Chew., 1957, 4, 179

679; 1964, 86, I944

1961, 896

93 1

Sac., 1964, 3466

Hydrogen Recovery by Palladium Diffusion AN INEXPENSIVE LARGE-SCALE PROCESS

The big demand for pure hydrogen has encouraged Union Carbide Corporation to develop a large-scale hydrogen diffusion process using thin palladium films. Hydrogen 99.99 per cent pure is being produccd at Corporation plants and the Olefins and Linde Divisions are prepared to manufacture units for salc elsewhere. The first nine plants will soon be operating, producing between them 34 million cubic feet of hydrogen per day.

R. B. McBride and D. L. McKinley have described these developments in a paper delivered at the 55th National Meeting of the American Institute of Chemical Engineers at Houston, Texas. Following experiments on the mechanisms of hydrogen diffusion through palladium, a pilot plant was built which operated satisfactorily from 1961 onwards.

Details were given of a 4 million cubic feet per day plant which uses a feed gas containing

50 per cent hydrogen. The diffuser operates at 350 to 400°C and produces hydrogen suitable for catalytic hydrogenation processes.

An important consideration is the availability of feed gases. The Union Carbide plant is designed for using off-gas streams from olefin plants and might also be used with coke oven gas or gas streams from oil refin- eries. Feed gases from such sources are low in cost and the reforming of other molecules to generate fresh hydrogen is obviated. Only hydrogen sulphide seriously poisons the palladium films and must be removed before the diffusion stage.

Factors which merit favourable consideration of diffusional recovery and purification of hydrogen include high pressure and concentration of feed gas, absence of contami- nants, and a requirement for high purity hydrogen at low pressure.


Reactions of Oxygen with the Platinum Metals 11-OXIDATION OF RUTHENIUM, RHODIUM, IRIDIUM AND OSMIUM

By J. c. Chastoii, A.R.S.M., Ph.D.

Research Laboratories, Johnson Matthey & Co Ltd

In the second part of this survey of the oxidation of the plat inum metals attention i s given to the formation of solid oxideJilms on the more reactive metals ruthenium, rhodium, ir idium and osmium. T h e j i lms formed in air on these metals are thick enough to give tarnish colours at temperatures of

400 to 500"C, and they may be in equilibrium with a n appreciable partial pressure of gaseous oxides at temperatures below that at which they decompose. Diagrams showing the solid (oxide and metal) phases and the sapour pressures of the gaseous oxide phases in equilib- r ium with one atmosphere of oxygen at temperatures up to about 1800°C are given fo r four o f the plat inum metals. A third part of this paper will deal with

the oxidation of palladium.

The first part of this review (I) dealt particularly with the oxidation of platinum at temperatures above about 600°C~ when (at atmospheric pressures) no solid platinum oxides can exist and the products of the reaction are volatile. The volatile oxides, it was emphasised, do not remain attached to the platinum surface and their rate of formation must necessarily be related to the geometry of the container in which they are confined, the temperature distribution throughout the system, and in addition the

Platinum Metals Rev., 1965, 9, (2), 51-56

pressure, the composition, and the rate and pattern of circulation of the diluent gases.

The same general considerations must also apply to the rates at which the volatile oxides of ruthenium, iridium, rhodium and osmium are formed.

In the particular case of palladium, compli- cations result from the need to consider the solubility of oxygen in the solid metal, so its reactions with oxygen will be considered separately.

The table summarises the presently known data on the dissociation temperatures of the solid oxides and the nature of the gaseous oxides which can exist.

I t should be added that the compositions quoted for the solid oxide phases are those of ideal crystals. I n general, solid oxides nearly always have a range of compositions, but the possible range has not yet been established for the platinum metal oxides.

I t should further be noted that although RuO, and OsO, can be prepared as solid oxides in a metastable condition at room temperature, they are not believed to form solid films on surfaces of their parent metals in an oxidising atmosphere.

No figures have been included in this table for the rates by which these metals lose weight when heated at high temperatures in oxidising conditions since, in spite of a grcat deal of recent experimental work, it is becoming increasingly evident that the factors control- ling transport of the volatile oxides have not been sufficiently controlled to make the pub-

51

Solid Oxide Phase in equilibrium with metal and

one atmosphere of oxygen at room Dissociation Temperature

temperature at I atm of oxygen

PtO, Rho, IrO, RuO,

oso,

280-450°C (3) 1400°C (4) IIZ0”C (5) I540O”C (2)

Gaseous Phases

PtO, Rho, IrQ (6) RuO, (2) (predominates slightly

RuO, (2) (predominates at lower temperatures)

at higher temperatures) oso, (4) oso, (4)

lished results meaningful. For these reasons it is not proposed to discuss further at this stage the formation of the volatile oxides of these metals.

Solid Oxides It is proposed, instead, to review a little

more closely the growth of films of solid oxides on these metals. As is apparent from the table, the solid oxides of rhodium, iridium, ruthenium and osmium are much more stable than the solid oxide of platinum, and are thus more readily studied. In the first part of this review, the charac-

teristics of solid PtO, were only very briefly touched upon. It was pointed out, however, that at temperatures below about 350°C (the precise temperature is uncertain, but is probably in the range 280 to 450°C) platinum surfaces are, when under a pressure of one atmosphere of oxygen, covered with a film of PtO,. It was suggested this film may thicken as the temperature is increased. It was not, however, made clear that the behaviour of the film cannot be predicted from the thermo- dynamical data quoted (any more than the loss of weight by formation of volatile oxides can be predicted thermodynamically), but will depend largely on the physical characteristics of the oxide film.

The film of solid PtO, is so very thin that its characteristics are not readily determined. At room temperatures there is some electrochemical evidence to suggest that it can be

thickened by anodic treatment in an electrolyte, but that in these circumstances the thickness reaches a maximum value in a matter of minutes. It has been calculated that a completely oxidised surface is covered with about 0.3 millionths of a gram of PtO, per square centimetre.

These observations would imply that at room temperatures the solid film of PtO, is dense and completely protective, like the film on stainless steel. How completely the protective properties are maintained as the temperature rises is at present a matter for speculation, but it would seem that the most likely clues to the possible characteristics of the solid oxide film at higher temperatures, but still below its decomposition temperature, may be derived from a study of the rather more reactive platinum metals.

Rhodium, iridium, ruthenium and osmium all, like platinum, remain bright and visibly free from more than very thin films of oxide at room temperature. As with platinum, a freshly-formed surface of any of these metals becomes covered with a film of oxide in a matter of seconds, but, as with platinum, the film first formed presumably acts as a barrier to smother further growth in some way. No visible tarnish ever develops in any normal environment.

When any one of these four metals is heated in air or oxygen to a temperature above about 400°C (and below the decomposition temperature of its solid oxide), thickening


of the oxide skin is clearly to be seen. There is not the slightest doubt that there is a change in the physical nature of the oxide layers. Whether the growth is due to enhanced diffusion of either metal or oxygen ions through the layer or whether it is due to cracking or the development of porosity has not been established, but the fact that the film is thick enough to have a colour of its own is clear enough.

The films, although thicker than those which form at room temperatures, are still by no means unprotective. They show not the slightest signs of growing unrestrainably. They, too, very quickly reach a maximum thickness, and thereafter apparently remain appreciably constant in weight and thickness for as long as the temperature is not further raised - at least in the temperature range up to, say, goo"C.

In passing, it is of interest to recall that these tarnish films are extremely refractory chemically. The film formed on ruthenium (or on ruthenium-platinum alloys), for example, resists pickling by boiling aqua regia. The films are most simply removed by hearing to above their decomposition temperature, the metal being then quenched in water to prevent the films from reforming during cooling. Alternatively, of course, they can be reduced by heating in hydrogen and then either quenching the work rapidly in water

or cooling it in a reducing atmosphere. It should be emphasised also that at

temperatures up to about goo"C the rates of tarnishing of even these more reactive platinum metals are very small - too small to be easily detected by any method dependent on measuring the changes in weight of a specimen.

Vapour Pressure of Solid Oxides The picture so far presented seems clear

enough. At relatively low temperatures - say up to 500°C for platinum and up to 900°C for rhodium, iridium and ruthenium -the platinum metals are at the most susceptible to slight tarnishing by a very thin and more or less protective film of solid oxide; and at a specific temperature, depending on the oxygen pressure and on which particular platinum metal is concerned, the solid oxide film can no longer exist, so that when the metal is quenched from above this temperature it is bright and free from tarnish.

It remains to consider how far the solid films themselves can contribute, by their own vapour pressure or by reaction with oxygen, to the losses of weight which are observed when the platinum metals are heated in air - particularly at temperatures just below the decomposition temperature of the solid oxide.

This mechanism needs particularly to be examined when dealing with the more reactive


of the platinum metals, and it is fortunate that reliable vapour pressure data for the oxides in the ruthenium-oxygen system (the most complex, apparently, of the platinum metal-oxygen systems) are now available. A very careful study(2)of this system has recently been made by Wayne E. Bell and M. Tagami of the General Atomic Division of General Dynamics Corporation, working in the John Jay Laboratory for Pure and Applied Science, San Diego, California, so it can be said that the oxidation pattern for ruthenium heated in oxygen under equilibrium conditions is well established.

In Fig. I an attempt is made to show diagrammatically the solid and gaseous phases which would be expected to be in equilibrium when ruthenium is exposed in a confined volume of oxygen at a pressure of one atmosphere at various temperatures over the range from 800 to 1600°C. At temperatures up to 1540°C the ruthenium is considered as being covered completely by a layer of solid RuO,. It is, unfortunately, impossible to say how thick the layer is or how protective and continuous it is at various temperatures in this range, but the assump- tion here made is simply that it is sufficiently protective as to be regarded as the only solid phase in contact with the oxygen. At tem-

peratures above 154o"C, of course, the solid ruthenium oxide can no longer exist and clean ruthenium metal is in contact with oxygen.

It will be seen that at temperatures above about IOOO~C small amounts of RuO, and RuO, will form and if the temperature is raised to 15oo0C the vapour pressure of the RuO, starts to increase rapidly. The vapour pressure of RuO, also rises, but much more

The total of the vapour pressures of these oxides in equilibrium with one atmosphere of oxygen reaches an order of one-thousandth of an atmosphere at a little over I IOO'C, and this vapour pressure (being about one thousand times greater than that of PtO, at the same temperature) is quite sufficient to account for appreciable losses of ruthenium when a specimen is heated in a current of oxygen.

This accounts for the well-known observations that ruthenium specimens when heated to around this temperature lose weight much more rapidly than platinum when heated at the same temperature, and on removal from the furnace are seen to be heavily discoloured and tarnished.

It is unfortunate that very little experimental evidence is available on the oxidation of osmium, although it seems probable that it follows the same general pattern as that of

slowly.


ruthenium as described above. The position is a little better with regard to the oxidation behaviour of iridium and rhodium, and such results as are available are set out diagrammatically in Figs. 2 and 3, and for conveni- ence a similar phase diagram for platinum is given in Fig. 4.

Comparison of Phase Diagrams In making the comparison between the

curves for these three metals, particular note should be made of the variations in the scales for vapour pressure. The vapour pressure

Platinum Metals Rev., 1965, 9, ( 2 )

curves are based on the results of Alcock and Hooper (7) and the decomposition temperatures of the solid oxides are from the sources quoted in the table on page 52.

Brief comments only seem necessary and the curves illustrate very well the paucity of the vapour pressure data available. With rhodium it is interesting that the solid oxide skin appears to exert an appreciable partial vapour pressure of RhO,(g) at temperatures several hundred degrees below its temperature of decomposition. With iridium, the out- standing features of the vapour pressure

55

curve are that there is such a relatively small change in partial pressure between 1200 and 15oo0C, as well as that the value of the partial pressure over the whole of this range is so high. It would be of particular interest to know the course of the vapour pressure curve when extended to lower temperatures below about IIOOOC when the surface of the metal is covered by a film of solid oxide. One question that inevitably arises concerns the possibility of an inflection in the vapour pressure curve at the temperature corresponding to the decomposition temperature of the solid oxide.

It will be appreciated that this discussion is necessarily based on the results of studies made under equilibrium conditions. So long as this is borne in mind these results can be of the greatest help in assessing the importance of the factors that are likely to influence the loss of weight of the platinum metals when heated at high temperatures in service, although it must always be emphasised that they cannot in themselves enable a quantitative determination to be made of the losses that occur in kinetic systems.

Many questions still call for an answer. It would be of the greatest interest, for example, to know much more of the structure of the solid oxide films on ruthenium and the other platinum metals. It would further be of

great interest to know the steps by which RuO, and RuO, are formed. Is the reaction one between oxygen and solid RuO,, and when this happens on the surface of an oxide- coated piece of ruthenium, how is the porosity and thickness of the oxide film affected ?

The possible influence of traces of moisture in oxygen on the rate and progress of the formation of oxide films on platinum metals has hitherto been entirely overlooked. When the mechanism of oxidation is considered in the light of all that has been said above, however, it is obvious that the structure and characteristics of the thin oxide films involved may very well be influenced by quite small amounts of water vapour, as well perhaps as of carbon dioxide, which would be present in industrial conditions. It is evident that here there is an immense field for further enquiry.

References 1 J. C. Chaston, Platinum Metals Rev., 1964, 8,

2 Wayne E. Bell and M. Tagami,J. Phys. Chem.,

3 L. Brewer, Private communication 4 L. Brewer, Chemical Reviews, 1953, 52, 1-75 5 G. Schneidereith, Diuertation from Harald

Schafer Imt . of Munster, Platinum Metals Rev., 1962, 6, 137

6 H. Schafer and H. J. Heitland, Zeit. anog. U. allgemeine chemie, 1960, 304, 249

7 C. B. Alcock and G. W. Hooper, Proc. Roy. Soc. A., 1960,254, 557

50-54

1963,679 2432-2436

Galvanic Couples with Platinum Metals SURFACE POISONING BY INTERMETALLIC COMPOUNDS

There is a fascination in observing how a skilled experimenter learns to exploit little known phenomena. For instance, the seasoned analytical chemist knows instinctively that if a sample of tin is slow to dissolve in acid the reaction can be made to proceed simply by placing a clean platinum wire through the liquid into contact with the tin. Some years ago, Buck and Leidheiser (Nature, 1958, 181, 1681) observed that some platinum metals were more effective than others in catalysing reactions of this type, the relativc effect of each platinum metal depending on the particular base metal with which it was coupled.

They now report (Nature, 1964, 204, 177) some further observations on platinum metal and base metal couples, both in direct contact and (connected externally) separated by a porous diaphragm. The results indicate that the behaviour of the platinum metals is influenced by films of intermetallic compounds which form on the surface. When used to catalyse the dissolution of tin, for instance, platinum and iridium are not seriously poisoned, but palladium rapidly loses its catalytic powers, and X-ray diffraction analyses show the formation on its surface of PdSn, and also of an unidentified compound.


The Care and Maintenance of Thermocouples PRACTICAL PROBLEMS OF INSTRUMENTATION AND INSPECTION

By H. E. Bennett, F.I.M. Quality Control and Inspection Department, Johnson Matthey & Co Limited

The thermocouple has for many years been the most practical choice as a means of measuring high temperatures. I t is accurate, consistent, robust, reasonably inexpensive, and gives a quick response to changes in temperature. At the same time, proper precautions must be taken in its instrumentation and use to ensure that these advantages are retained, and that the care given to its manufacture by the metallurgist is not vitiated by unnecessary contamination or ill treatment during its service life. In many industrial operations such as melting, casting and heat treatment the quality of the final product may depend a great deal on maintain- ing the accuracy of temperature measurement.

The realisation of the importance of this aspect of engineering metallurgy has presumably provided the impetus for the Institu- tion of Engineering Inspection to publish a thirty-page monograph on “Thermocouples : Their Instrumentation, Selection and Use”, compiled by B. F. Billing, of the Royal Aircraft Establishment.

This is a good practical manual, providing sufficient theory to enable works engineers, inspectors and laboratory technicians to understand the fundamentals of thermocouple thermometry. The principles of current- sensitive and potentiometric measuring instruments are well described in concise language, without omitting essential details. Although the sensitivity of the different types of instrument is indicated, there is no recommendation to enable the user to choose

equipment most suitable for his purpose. There is also no mention of recorders, quick- response instruments or large-scale indicators so useful in a foundry or heat-treatment shop.

The whole field of base metal and rare metal thermocouples is surveyed accurately, the facts being well documented and up to date. The scope of the platinum metal thermocouples is well covered objectively, with information on insulation and the risks of contamination. There is a review of high temperature thermocouples - of increasing importance nowadays -including the Feussner couple and the iridium : tungsten couple, but there is no warning of the embrittlement of iridium through recrystallisation after use at high temperatures. One omission is the 0.1 per cent molybdenum-platinum : 5 per cent molybdenum-platinum thermocouple for the measurement of temperature under conditions of neutron radiation.

While there is a place in the literature for reference to such methods as burying the reference junction 10 feet in the ground, which no one is likely to employ, it scarcely has a place in a practical monograph. More- over, the subject is unnecessarily complicated by reference to thermocouples in series or parallel, and details about the more complex instruments and methods of calibration.

The appendices give some useful tables comparing the calibrations, working ranges and physical properties of a wide variety of thermocouples suitable for use down to near absolute zero.


In a monograph offered to engineering inspectors, it might have been thought desirable to give a more practical emphasis to the faults and failings of thermocouple installations, as it is often the simple and almost obvious faults that are overlooked. Over and over again failures and rejections occur in industrial processes owing to faulty temperature measurement.

The positioning of a thermocouple in a heat-treatment furnace is of first importance. Most furnaces have temperature gradients and all too often a thermocouple is placed in a position of safety, perhaps in the roof of the furnace, where the temperature may bear little resemblance to the temperature of the work. Occasions have been known when billets have started to melt at one end of a furnace, while those at the other end were at the required temperature. The temperature variations within the chamber of a furnace should always be explored, and if necessary allowances made for the difference between the temperature at the control couple and that of the work. In critical circumstances a thermocouple should always be placed on or very near the work. The time required to attain the desired temperature, depending upon the size of the part and the thermal capacity of the furnace, should also be considered.

There is need for a constant awareness of the possibility of contaminating a platinum

metal thermocouple. It is extremely unIikeIy that a new thermocouple will be faulty, but often, when a thermocouple breaks in service due to contamination, it is replaced by a new one in the old sheath, which itself must have become contaminated. Platinum thermocouples will give long and reliable service at high temperatures, often under apparently adverse conditions, provided that they are adequately protected against the few sub- stances that can contaminate them.

Thermocouple installations should be regu- larly inspected and tested. A temperature indicator or recorder should bc checked, either with a potential divider or a standard thermocouple at least once a month, whether it is used much or little. Terminals must be kept clean, insulation must be checked, and thermocouples themselves must be recali- brated.

Where many couples are in constant use, the simplest and quickest reliable means of calibration should always be kept in readiness for a thermocouple check by a competent technician.

So the inspector must make himself aware of the sources of error in thermocouple installations : the thermocouple must be properly located to give the true temperature of the work, its correct positioning inside the sheath must be assured, it must be free from stresses liable to cause fracture, and insulation must be effective, especially on bends.

Electrochemical Hydrogen Purification THE USE OF A MODIFIED FUEL CELL TECHNIQUE

Arising from research in the field of fuel cell technology, a novel electrochemical method for purifying hydrogen has been reported by J. E. McEvoy, R. A. Hess, C. A. Mills and H. Shalit, of Houdry Process and Chemical Co (Znd. and Eng. Chem. Process Design and Development, 1965, 4, (I) I). In a hydrogen-consuming fuel cell the gas is oxidised electrochemically at the anode, using oxygen supplied to the cathode and a suitable electrolyte separating the two electrodes. This

system may be modified by the use of two highly reversible hydrogen electrodes operating in an electrolyte of 30 per cent H,SO, to form a purification cell in which hydrogen containing impurities is consumed at the anode and quantitatively generated at the cathode. A small e.m.f. applied across the two electrodes provides the driving force. Both the anode and the cathode are prepared by incorporating a platinum-impregnated charcoal catalyst in a suitable carbon matrix.


Platinum for Resistance Thermometry EFFECTS OF SURFACE CONTAMINATION

Recognition of the virtues of the platinum resistance thermometer as a practical means of accurate temperature measurement has been slow. Recently, however (perhaps largely on account of improvements in electrical measuring instruments), it has been finding wider use in the laboratory and in industry. In particular, it offers many attractions as an instrument for measuring very low temperatures. It seems likely that the range of temperature over which it will be employed to define temperature on the International Practical Temperature Scale will be extended from the present limits of between 90°K (-183°C) and 900°K (627°C) to the whole of the long range from 2oCK (-253"C, the boiling point of hydrogen) to 1336°K (1063T, the melting point of gold).

It is thus of special interest to be able to understand the exact mechanism by which changes in temperature can affect the resistivity of platinum. In the past it has been common to base theories of conduction on the simple view that any expression for resistivity can be separated into two terms, one indepen- dent of temperature and the other temperature dependent. This is known as Matthies- sen's Rule, and may be written simply

where R and R, represent the resistance at temperature T and at 0°K respectively.

In a recent paper D. R. Lovejoy, of the Division of Applied Physics, National Re- search Council, Ottawa, describes (Canadian J. Physics, 1964, 42, (11), 2264) how an analysis of a very large volume of experimental data collected during the calibration of resistance thermometers reveals that the resistance characteristics of thermometric grade platinum wire show, in fact, considerable devia-

R=% +f(T)

tions from Matthiessen's Rule. An important practical consideration that emerges is that various batches of thermometric grade platinum having the same value of temperature coefficient of resistivity measured between o and IOOOC can have significantly different values of resistivity at temperatures below about - 180°C.

In the paper a theoretical study is presented in an endeavour to find the causes of these deviations. It is known that positive deviations from Matthiessen's Rule result when- ever two or more groups of carriers which contribute additively to the conductivity are affected by a change of temperature to a different degree by the two scattering mechanisms (photo scattering and impurity scattering).

The results of tests on Ehree batches of 30, 59 and 33 thermometers respectively are analysed and it is shown that the variations can all be explained by the 2-electronic band theory of Sondheimer and Wilson if it is considered that the thermometer wire in fact consists of parallel bands which vary in impurity concentration. The model finally set up to reconcile the calibration data postu- lates that the wire consists simply of a virtually pure core of platinum, surrounded by two regions of contamination. These regions comprise :

(I) A heavily contaminated surface skin extending to a depth of about 10 atomic layers. This accounts for variations in resistivity near 700°K.

(2 ) A sub-surface layer about 200 atoms thick in which the impurity level aver- ages about 0.1 per cent. This accounts for variations in the resistivity in the region of 90°K.


By making these assumptions it is shown that the observed variations in parameters A, alpha, B and C in the Callendar Van Dusen equation can be satisfactorily accounted for, and in addition it is possible to explain the variations in resistivity below 90°K.

From this work it follows that the surface contamination normally present on the wire of an average platinum resistance thermometer is the major cause of error in resistance thermometry at low temperatures. If this can be prevented there secms no reason why these instruments should not bc uscd with confi- dence and the readings extrapolated below 9o'K to an accuracy of better than a few millidegrees K.

The results also serve to indicate the steps

that can undoubtedly be taken to improve the reliability of platinum thermometers in this respect. It is pointed out that the simple step of increasing the wire diameter alone and thereby reducing the proportion by which surface effects can influence resistivity is not a satisfactory solution and can raise more problems than it would solve. There is, however, very great hope that considerable improvements can be made by scrupulous attention to cleanliness at ali stages in hand- ling the wire and fabricating the thermometers. It is particularly hopeful to note that even now many of the best commercial thermometers show excellent performance at low tempcratu,res.

J. C . C .

Thermal Conductivity of Pure Platinum The thermal conductivity of pure platinum

was recently found by Powell and Tye ( I ) at the National Physical Laboratory, working for the first time on substantial solid specimens, to remain surprisingly constant within 0.5 per cent of 0.73W cm-loC-l over the range o to 950°C. Several other investigators have since examined the thermal conductivity of platinum and some of their results were reported at the Thermal Conductivity Conference at the National Physical Laboratory last July.

At first sight the conclusions of Powell and Tye are not fully supported by this further work. Thus K. H. Bode (2j of Physikalische- Technische Bundesanstalt, Braunschweig, obtained a value rising from 0.7025 to 0.7100 between o and IOO'C using as test piece a massive cylindrical specimen. The platinum, however, contained 135 to 150 p.p.m. of impurities and its density was only 21.32 g/ml compared with 21.5, the NPL figure.

J. J. Martin and P. H. Sidles (3) of Iowa State University measured the thermal diffusivity of two specimens, one of high purity (99.999 per ccnt) and the other less pure (99.9 per cent) at temperatures up to 927OC and from their results calculated values of thermal conductivity. Unexpectedly the purer sample had the lower thermal conductivity at high temperatures. The figures obtained for the purer sample were, however, certainly not constant, being 5 per cent lower

at room temperature than the value found by Powell and Tye, and 10 per cent higher at

Finally, M. J. Wheeler (4) of the Hirst Research Centre of the General Electric Company Limited, at Wembley, measured thermal diffusivity from 907" to 1477°C using a modulated beam technique. The calculated

877°C.

values of thermal conductivity agree reasonably well with those of Powell and Tye around I I O O " ~ but tend to rise at higher temperatures.

On the whole this new evidence does not seem to be of sufficient weight to overthrow the conclusion of Powell and Tye that the thermal conductivity is sensibly constant from room temperature to around 900°C. On the other hand, it is possible that there may very well be an inflexion around 800 to 900"C, the thermal conductivity tending to rise at higher temperatures.

J. C. C .

References I Platinum Metab Rev., 1964, 8, 13 z K. H. Bode, PTB-Miueilungen, 1964, 75,

(in the Press) 3 J. J. Martin and P. H. Sidles, Contribution

1614 from Institute for Atomic Research and Department of Physics, Iowa State Univer- sity, Ames, Iowa

4 M. J. Wheeler, Brit.J. uf App. Physics, 1965, 16, (31, 365


ABSTRACTS of current literature ova the platinum metals and their alloys PROPERTIES

Effect of the Addition of Palladium on the Properties of Platinum-Cobalt Permanent Magnetic Alloys K. WATAI, s. SHIMIZU and Y . TSUJI, J . Japan Inst. Metals, 1964, 28, (1 I), 745-749 Pt-Co equiatomic alloys were prepared by powder metallurgy with Pd substituted for some Pt. This depressed the lattice transition temperature and raised the magnetic transition temperature. As Pd was added the axial ratio of the superlattice approached unity. Alloys with : a 1 0 at.", Pd formed no superlattice. Pd delayed the rate of lattice transition so that higher temperature and longer heat-treatment were needed for the best permanent magnets with improved high temperature stability. Alloys with 2 to 5 at.",, Pd had energy product >1o7 G.Oe with improved reproducibility.

Calculation of Thermoelectric Power of Pd-Ag and Pd-Rh Alloys H. KIMURA and M. SHIMIZU, J. Php. SOC. Japan, 1964Y19, (9)1 1632-1637 Assuming that only s-electrons are current carriers, calculations of thermoelectric powers of Pd-rich Pd-Ag and Pd-Rh alloys from the Mott model for s-d scattering and from the density of electronic states derived from low temperature specific heat data agreed qualitatively with experiments at room but not at low temperature. The role of d-holes is discussed. Experimental results can be assigned to a function of composition and temperature by assuming that: phonon drag affects the thermoelectric power of Pd at low temperature.

Yield-strength Variation in Polycrystalline Silver-Palladium Alloys P. RODRIGUEZ and K. K . RAO,?. Inst. Metals, 1964, 93, (31, 96 Curves of yield strength and ultimate tensile strength against composition for Ag-Pd alloys were derived from true stressitrue strain curves for each alloy tested. Specimens were polycrystalline 0.01 in. wires. Maximum yield strength occurred at 25 at.", Ag-I'd.

Thermodynamic Properties of Solid Palladium-Silver Alloys K. M. MYLES, Acta Metallurgaca, 1965, 13, (2)) 109-1 13 Chemical activities of Ag and of nine Ag-Pd alloys, and their free energies, entropies, and enthalpies of formation at 12oooK, were com-

puted from vapour pressure measurements by the torsion-effusion method at 1100 to 1300'K. Ag activities show large negative deviations from ideal behaviour over the whole range, while Pd activities deviate positively in Pd-rich and negatively in Ag-rich alloys. Thermodynamic properties are compared to earlier data. Excess entropies and enthalpies are both negative.

[Thermal Coefficient of Expansion of Palau Alloy1 P. L. SPDDING, J. Less-Common Metalsy 1964, 7, (9, 395-396 The linear expansion coefficient of Soo, Au-Pd was measured up to rooo"C using a precision micrometer type instrument. It varied from 13.20 x 10-6 cmjcm "C at 100°C to 15.40 x 10-6 cm:cm "C at 10oo"C. Results are tabulated together with the slightly higher calculated values.

Effect of Temperature on the Lattice Para- meter of a 58.98 at.:/, Gold-41.02 at.Oh Palladium Alloy U. DEVI, C. N. RAO and K. K. RAO, Acta Metallurgica, 19651 13, (11, 44-45 Lattice parameters were proportional to temperature in the range 0-600°C. The alloy exhibited short-range order.

Lattice Spacings of Gold-Palladium Alloys A. MAELAND and T. B. FLANAGAN, Canad. J . Phys.,

Lattice parameters of alloys in the Au-Pd system were determined by X-ray diffraction and are tabulated. Small negative deviations from linear dependence of parameters on composition, predicted by Vegard's Law, which occur in the Au-Pd and Ag-Pd systems, are discussed. Greater deviations in the Ag-Pd system may be due to the compressibility of Ag being larger than that of Au.

Unit-cell Dimensions of Ni-Pd Alloys at 25 and 900°C L. R. BIDWELL and R. SPEISER, Acta Cryst., 1964,

Lattice parameters from crystal studies of a complete range of Ni-Pd alloy compositions were tabulated to a precision estimated as &I part in 10,000 at 25°C and f 3 parts in 10,000 at 900°C.

The Relative Thermodynamic Properties of Solid Nickel-Palladium Alloys Ibid., Acta Metallur~ica, 1965, 13, (z), 61-70 Measurements at 700-1200°C using a solid electrolyte galvanic cell showed that the relative partial molar free energies of Ni were linear with

1964, 42, (II), 2364-2366

17, (II), 1473-1474


respect to temperature, that Ni-rich solutions have endothermic enthalpies of mixing and positive deviations from Raoult's Law for the solvent and negative for the solute and that Pd-rich solutions have exothermic enthalpies with negative deviations for solvent and solute. All excess entropies of mixing are positive. Ni-Pd alloys, especially when Pd-rich, have short-range order.

The System Palladium-Molybdenum E. M. SAVITSKII, M. A. TYLKINA and 0. KH. KHAMIDOV, Zk. Neorg. Kkirn., 1964, 9, (IZ), 2738-2742 Microscopic and X-ray tests established the Pd-Mo constitution diagram as of peritectic type with two solid solutions and one intermetallic compound. The a-solid solution contains up to 33 wt.% Mo. Electrical resistivity and the elastic limit rise with greater Mo content but the temperature coefficient of resistance decreases. The P-solid solution contains up to 17 wt.O; l'd near the melting point but only IZ wt.% Pd at 1400°C. It has b.c.c. structure. The E-phase compound has h.c.p. structure with a=2.761, c=4.476 A, c/a=1.62 and is formed peritectically at 1750&25"C from the melt and the P-phase. It decomposes at 1425125'C into the a- and p-solid solutions.

Ferromagnetism in Dilute Solutions of Gadolinium in Palladium J. CRANGLE, Pkys. Rev. Letters, 1964, 13, (IS), 569-570 Magnetisation of Pd-Gd alloys containing up to 9.7 at.?; Gd was plotted against magnetic field at temperatures between 1.5 and 81°K. Ferro- magnetism persisted down to alloys with < I at.n, Gd. Curie temperatures were lower than for Pd-Fe and Pd-Co alloys.

Superconducting Tubes and Filaments G. ARRHENIUS, R. FITZGERALD, D. C. HAMILTON, B. A. HOLM, B. T. MATTHIAS, E. CORENZWIT, T. H. GEBALLE and G. w. HULL,^. Appl. Phys., 1964,

A regular prismatic honeycomb of a superconducting compound was observed when 20.5 at.% La was quenched with Rh in an arc furnace. For ~ 0 . 5 at.()'O La the network was not observed, indicating lowering and broadening of the superconducting transition region. At these concentra- tions superconducting tunnelling occurs through the elemental Rh phase. This points to the super- conductivity of Rh at lower temperatures.

Magnetic Susceptibility andElectronicSpecific Heat of Transition Metals and Alloys. VIII. Zr and Rh Metals M. SHIMIZU and A. KATSUKI, J . Pkys. SOC. Japan, 1964, 19, (IO), 1856-1861 Temperature variations for electronic specific heat of Rh are explained by calculated results but calculated values for spin paramagnetic susceptibility are lower than observed values.

35, (14, 3487-3490

The Niobium-Rhodium Binary System. Part I. The Constitution Diagram D. L. RITTER, B. c. GIESSEN and N. J. GRANT, Trans. Met. SOC. A.Z.M.E., 1964, 230, (6), 1250-1259 The complex constitution diagram of this sytem was determined from X-ray, metallographic, solubility limit, and transformation and solidus temperature tests and indicated nine intermediate phases with two eutectic, five peritectic, two eutectoid, and three peritectoid reactions.

Part 11. Crystal Structure Relationships Ibid., 1259-1267 The crystal structures of the nine intermediate phases are: a-Nb,Rh, Cr,O-type; a, type; a, H.T. phase of unknown structure; a,, AuCu-type; a,, orthorhombic analogous to a l of the Ta-Rh system; ma, AuCd-type; aa, mono- clinic related to Sm-type; a6, VCo,-type; a-NbRh,, AuCu,-type. The last six are close- packed structures which are compared with Nb-Ir, Ta-Rh and Ta-Ir systems.

The Niobium-Iridium Constitution Diagram B. c. GIESSEN, R. KOCH and N. J. GRANT, Zbid., 1268-1273 X-ray, metallographic, solubility limit and solidus tests of the Nb-Ir system showed the five intermediate phases : a-Nb,Ir, cubic Cr,O-type; a, tetragonal cs F ~ - c ~ type; a, tetragonal AuCu- type; a,, orthorhombic isostructural with a, in the Ta-Rh system; a-NbIr,, cubic AuCu,-type. a-Nb,Ir and a-NbIr, melt congruently. There are three eutectic and three peritectic reactions.

Phase Diagram of the System Chromium- Ruthenium A. K. SHURIN and G. P . DIMITRIEVA, Sb. Nauckn. Raboi Inst. Metallofz., Akad. Nauk Ukr. S.S.R.,

X-ray and micrographic studies of r8 homogeneous and repeatedly annealed Ru-Cr alloys with 3.8-73 wt."; Ru revealed that 20 wt.Yn Ru-Cr melted at 1780-90°C and that a eutectic formed at 37.5 at.?: Ru, 1610+1o'C. In cooling from liquid, P-phase Cr in Ru solid solution crystallised at 1665"C, the eutectic at 16oo0C, and a-phase Ru in Cr, which was homogeneous over 35.5-37.5 at.?, Ru, at 1580°C. Ru in Cr was 34 at.?; soluble at 1600OC to 19 at."o at 800°C; CrinRu52.5at."& at 1600~Cto46at.~,atgoo"C. Cubic P-W-type RuCr, decomposed at 780°C. Structure and decomposition temperature of RuCr, could not be determined.

Transformations in Iron-Ruthenium Alloys under High Pressure L. D. BLACKBURN, L. KAUFMAN and M. COHEN,

us. Rept. AD 437,5799 1964,37 PP. A diffusionless a (b.c.c.) 3 y (fcc.) transformation occurs on heating and cooling < 12 at, YO Ru- Fe alloys at atm. pressure and 12-36 at.:(, Ru-Fe

1964, (IS), 170-174


alloys show a diffusionless E (h.c.p.) S y (f.c.c.) transformation. High pressure depresses the a-Y reaction temperature but elevates that of the E-y reaction. Pressure also causes an a-E transformation at room temperature in alloys which contain a at atm. pressure. Pressure-temperature diagrams at constant composition have triple points involving a, y, E. Triple-point pressure decreases continuously as Ru content increases.

CHEMICAL COMPOUNDS

Thermal Dissociation of Platinum Iodides s. A. SHCHUKAREV, T. A. TOLMACHEVA and G. M. SLAWTSKAYA, Zh. Nearg. Khim., 1964, 9, (11), 2501-2506 Thermal stability studies on PtI, and PtI, showed that dissociation pressure varied continuously during their oxidation. Enthalpy of dissociation was: PtI,,-4 kcalimol; Pt13,-xz kcal/mol. Dis- sociation pressure was I atm for PtI, at 246°C; for PtI, at 277°C.

New Fluorides of Palladium: Palladium(I1) Hexafluoropalladate(1V) and Related Com- pounds and Palladium Tetrafluoride N. BARTLETT and P. R. RAO, PTOC. Chem. SOC. , 1964, (Dec.),393-394 The “trifluoride” of Pd is Pd2+[PdF,]‘-. It was obtained by adding BrF, to PdBr,. Other compounds of general formula Pdz+[MF6]z- were prepared by adding BrF, to Pd(II)Br, and the appropriate acid former, e.g. GeO, for PdGeF,. Fluorination of these salts at 150-3oo~C yields PdF, in the case of Pd2f[PdF,]*- and mixed tetrafluorides in the other cases. PdF4 has tetragonal unit cell with a=6.585fo.o005 A, ~=5.835&0.005 8, v=253 8, Z=4.

Molecular Structure of .rr-Allyl-palladium Acetate M. R. CHURCHILL and R. MASON, Nature, 1964,

Results of a three-dimensional X-ray analysis of n-ally1 palladium acetate are illustrated and discussed.

Complexes of Ruthenium, Rhodium, Iridium, and Platinum with Tin(I1) Chloride

J . Chem. SOC., 1964, (Dec.), 5176-5189 Pt metal salts reacted with Sn(I1) chloride to form the anions [RuCl,(SnCl,)J ,-, [Rh,CI,(SnCl,),]*-, [1r2Cl6(SnCl3)J-, and cis- and trans-ptCI, (SnCl,),]*-, where the trichlorostannate (11) has a donor anionic ligand as strong as chloride ion. Neutral Rh, Ir, and Pt complexes were prepared with an SnCl, group bound to the metal together with ligands such as di-olefins, triphenylphosphine and -arsine, e.g. (C,H,),RhSnCl, and (Ph3P),PtC1(SnCl3).

204, (4960), 777

J. F. YOUNG, R. D. GILLARD and G. WILKINSON,

Transition Metal-Carbon Bonds. Part 11. r-Allylic and Related Complexes from Some Cyclic 1,3-Dienes s. D. ROBINSON and B. L. SHAW, 3. Chem. soc., 1964, (Dec.), 5002-5008

Preparations are described of chloro-bridged methoxy x-allylic Pd(I1) complexes from several cyclic 1,3-dienes, of cyclohepta- and cyclo- octadienyl Pd(I1) complexes, and of a meth- oxylooctatrienyl Pd(I1) complex.

The Action of Reducing Agents on Pyridine Complexes of Rhodium(TI1) B. N. FIGGIS, R. D. GILLARD, R. s. NYHOLM and G. WILKINSON, Ibid., 5189-5193 A series of pyridine complexes containing Rh(I1) is now shown to contain Rh(II1).

Thermodynamic Properties and Stability of Ruthenium and Osmium Oxides A. B. NIKOL’SKII and A. N. RYABOV, Zh. Neorg.

Areview of data for enthalpy of formation, entropy, and free energy of formation of Ru and 0 s and their oxides. (32 refs.)

Dehing the Heat of Sublimation of Ruthen- ium Tetroxide A. B. NIKOL’SKII, Ibid., 290-292 AHsubl. RuO, is 13.2fo.2 kcal/rnole.

New Complex Compounds of Phthalocy- anine with Ruthenium and Iridium B. D. BEREZIN and G. v. SENNIKOVA, Dokl. Akad. Nauk. S.S.S.R., 1964, 159, (I), 117-120 The acidic-basic properties, absorption spectra, and kinetics of stability were determined for H,SO,IrPc and H,SO,RuPc, which are compared with Pt metal and Ni and Co phthalocyanines.

Khim., 1965, 10, (I), 3-9

ELECTROCHEMISTRY The Transmission of Electrolytically Depos- ited Hydrogen through a Palladium Mem- brane Electrode. I. The Rate Equations G. W. CASTELLAN, J . Electrochem. Soc., 1964, 111,

11. Experimental. Oxidising Agents and Hydrogen Gas on the Exit Side R. A. LA PIETRA and G. w. CASTELLAN, Ibid., 1276- I279 III. Pressure and Temperature Dependence P. L. DAMOUR and G. W. CASTELLAN, Ibid., 1280- 1283 A mechanism is postulated for transport of H z through a Pd membrane which relates the amount of Hz transmitted to a current density, -j, and the rate of deposition of H, per cm2 to a polarisation current density, 4. In general, for

(II), 1273-1276


equilibrium on both sides of the membrane, 50% of the H, deposited is transmitted. Trans- mission rate reaches a limiting value, -jm, when -i is high and for thin membranes of thickness L, L cc r / (-jm). The slope of this relation depends on the diffusion coefficient of H a in Pd, is inde- pendent of surface reaction rates, but may depend on the equilibrium coverage by H atoms. The mechanism was tested and gave a low diffusion coefficient D, which just below room temperature has D =0.0260 exp ( -6800/RT) cm2/sec. From 0.329 to I atm. the penetration-exit reaction H@ds) =H(bulk) is the slowest surface reaction but is fast enough to have an exchange current density of 0.8 A/cm2 at I atm.

Preparation and Surface Area Measurements of Platinised-Platinum Electrodes M. J. JONCICH and N. HACKERMAN, Ibid., 1286--1289 Surface areas of platinised Pt electrodes measured by two methods were in good agreement. Specific surface areas of the Pt deposits were functions of the geometry of the plating system, the composition of the plating solution, the time of plating, and the current density. Deposits from the first stages of plating tended to have higher specific surface areas. Additions such as Pb acetate assist adherence of deposits but decrease reproducibility.

Passivation of Rhodium in Hydrochloric Acid Solutions J. LLOPIS and M. VhZQUEz, Electrockim. Acta, 1964,

Anodic and cathodic charging curves for a Rh plate electrode show that passivation occurs by electrochemical surface oxidation, in HCIO, electrolyte by the formation of monomolecular films of Rh,O, or Rho,, depending on the potential, and in HCI electrolyte by the formation of RhaO, only and the absorption of CI atoms.

9, (12), 1655-1663

ELECTRODEPOSITION AND SURFACE COATINGS Development of a Process for the Deposition of Noble Metal Resistors in Microcircuits E. E. WRIGHT and w. w. WEICK, Electrockem. Tecknol., 1964, 2, (9-IO), 262-267 Pt and Pd-Au resin films were applied to glass and ceramic substrata by dipping or spinning and were decomposed thermally to produce resistive films of 30-roo ohm/cm2 and 10-30 ohm/cm2 respectively. Microcircuits for a five-bit computer adder were made in this way. Life tests indicated high resistor stability. Resistors seem well suited for high temperature service.

Metallising Non-conductors E. B. SAUBESTRE, L. J. DURNEY and E. B. WASHBURN, Metal Finishing, 1964, 62, (rI), 52-59 New methods of metallising A.B.S. plastics use

chemical conditioning in place of roughening followed by etching and cleaning. The metallising steps of sensitising, activation with dilute PdCI, solution, and electroless Cu plating are unaltered. The Cu electroplating step has been improved and final plating is now easier.

LABORATORY APPARATUS AND TECHNIQUE The Preparation of Calcium Tungstate Crystals by a Modified Floating Zone Recrystallisation Technique D. B. GASSON, 3. Sci. Imtrum., 1965, 42, (2), 114-115 Precise control over the shape of the growth front of the CaW0,:Nd3+ single crystal is maintained by having a small area of an Ir strip heater immersed in the melt itself. Ir is the only metal which leaves the crystal free of metal or oxide particles. Uniform growth is ensured by rotation of the growing crystal at 60 rev min-I. Two holes in the Ir strip ensure that only the periphery of the growth front is affected. The afterheater furnace which anneals the crystal is wound with Pt wire.

CATALYSIS Catalytic Activity of Reduced Platinum- Ruthenium Oxides G. c. BOND and D. E. WEBSTER, Proc. Ckem. soc.,

Pt-Ru oxides, prepared by a modified Adams method, on reduction have high activity in certain hydrogenations performed by shaking 10-50 mg catalyst with 20 ml alcohol solution of reactant at 30°C. Compared to PtO, the rate was enhanced four times for nitrobenzene, twice for o-nitroaniline. Indirect evidence that the Pt and Ru are alloyed in the catalyst is presented.

Homogeneous Isomerisation of Pent-1-ene Catalysed by a Platinum-Tin Chloride Complex G. c. BOND and M. HELLIER, Ckem. & Ind., 1965,

The complex isomerised pent-I-ene to cis- and trans-pent-a-ene when shaken in CH,OH under H, at 25°C. The trans : cis ratio at equilibrium after r.5 h was about 81 : 17.5. A mechanism is proposed to explain this ratio by means of a complex ion of Pt and Sn chlorides reacting with H,. The Importance of rr-Bonded Intermediates in Hydrocarbon Reactions on Transition Metal Catalysts J. J. ROONEY and G. WEBB, J. Catalysis, r964, 3,

Mechanisms involving n-bonded intermediates for exchange of paraffins, olefins and aromatics

1964, (Dee.), 398

(I), 35-36

(6), 488-501

Platinum Metals Rev., 1965, 9, (2) 64

with D for hydrogenation, dehydrogenation and isomerisation reactions on transition metal catalysts are reviewed, affording a rational explanation of many unrelated phenomena. Metal surface atoms have properties resembling those of free atoms and ions. Heats of chemisorption of x-bonded intermediates, and catalytic activity and selectivity shouId be functions of the metals’ positions in the periodic table.

On the Problem of the Kinetics of Dehydro- cyclisation of n-Heptane and n-Octane on Alumina-Platinum Catalysts YU. N. usov, N. I. KUBSHINOVA and L. s. SHESTOVA, Neftekhimiya, ~964, 4, (s), 700-707 Conversions of n-heptane and n-octane were studied at 38o-42o0C, atm. pressure, over Pt /A1,0,. Product ratios of alkanes, alkenes and arenes are tabulated and the reaction kinetics are discussed.

Kinetic Equations for the Reaction of n-Heptane under Catalytic Reforming Con- ditions F. A. FEIZKHANOV, G. M. PANCHENKOV and I. M. KOLESNIKOV, Ibid., 722-726 Isomerisation, hydrocracking and dehydrocyclisation of n-heptane were studied on platforming catalysts. Kinetic equations were derived as functions of the adsorption coefficient, the reaction rate and the activation energy of the reactions.

Organic Synthesis by means of Noble Metal Compounds. VIII. Catalytic Carbonylation of Allylic Compounds with Palladium Chlorides J. TSUJI, J. KIJI, s. IMAMURA and M. MORIKAWA, J. Am. Chem. SOC., 1964,86, (20), 4350-4353 Ally1 chloride and allyl alcohol reacted with CO at 100 kg/cm2 in C2H,0H in the presence of PdC1, to form ethyl 3-butenoate. Other allylic compounds reacted similarly. In C,H, solution allyl acetate formed 3-butenoic acetic anhydride and allyl ether yielded 3-butenoic anhydride by CO addition to the allylic carbon. IX. Preparation of a New Type of r-Allylic Palladium Chloride Complex and its Car- bonylation J. TSUJI, s. IMAMURA and J. KIJI, Ibid., 4491 New complexes were formed from a, p- and p,y- unsaturated carboxylic esters by heating the latter in the presence of PdCI,, by addition of the esters to an alcoholic solution of Na chloro- palladate, or by their addition to CBHa solution of bisbenzonitriledichloropalladium. Physical properties of the complexes are tabulated and their carbonylation is being studied. VII. Reactions of Olefin-Palladium Chloride Complexes with Carbon Monoxide J. TSUJI, M. MORIKAWA and J. KIJI, Zbid., (22),

4851-4853 Olefin-PdC1, complexes reacted under 40-100 kg/cm2 pressure of CO to form p-chloroacyl

chlorides. Yields were moderate only. Carbonyla- tion was followed by esterification. Similar reactions of some chlorinated olefins were also studied.

Isomerisation of n-Pentane over Platinum Alumina Catalysts of Different Activity w. N. LISTER, J. L. HOBBS and H. w. PRENGLE, Am. Inst. Chem. Eng. J., 1964, 10, (6), 907-912 Reaction of n-C6HI2 over 0.3 wt.% Pt/Al,O, took place at two distinct sites on the catalyst; the amount of hydrogenation-dehydrogenation depended on the Pt content and the isomerisation depended on the acidic content; 0.26 and x.69 wt. % chloride contents were tested. Diffusion within the catalyst pores may have affected the rate of reaction. Kinetic factors are evaluated and discussed.

Study of Mixed Adsorption Catalysts for Dehydrogenation. 111. Pd-Au/SiO, as a Catalyst for Cyclohexane Dehydrogenation A. A. ALCHUDZHAN, M. A. MANTIKYAN and A. M. AIKAZYAN, Izv. Akad. Nauk Armyan. S.S.R., Khim. Nauki, 1964, 17, (4), 368-374 Catalysts with 1.0 or 0.2 wt.% Pd and Pd:Au ratios from X:I to x:18 were tested. Au did not affect the activity of 1.0 wt.% Pd catalysts what- ever the method of Pd and Au deposition on SiO,. 0.2 wt.% Pd catalysts prepared by joint deposition of Pd and Au showed increasing activity as the Au content rose. Activity then reached a maximum and decreased.

Hydrogenation of P-Furylpropionic Acid on Catalysts Containing Certain Metals of Group VIII

I. F. BEL’SKII, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1964, (XI), 2102-2103 Hydrogenolysis of the furan group of p-furylpropionic acid over 5% Rh/C at atmospheric pressure and 265°C in a flowing system yielded y-ketoenantic acid from which H,O was elimin- ated to give 60% yield of 5-propylbutyrolactone. Over 5% Pd/C the hydrogenation of double bonds in the furan group yielded 47% p-tetra- hydrofurylpropionic acid at 250’C. 5 % Pt/C, 10% RaneyPdand 30% Ni/ZnO werealso studied.

Study of the Dual Nature of Selectivity and Stereospecificity in the Process of Hydro- genating n-Pentynes on Pd-, Pt- and Rh- Catalysts L. KH. FREIDLIN and Yu. YU. KAUP, Zbid., (IZ),

Monoolefin formation by hydrogenation of n- pentynes on Pd-, Pt- and Rh-black and on Raney Ni catalysts is determined by the adsorption of the pentynes and desorption of the products at the catalyst surface. Graphs show the relative amounts of products formed using each catalyst.

N. I. SHUIKIN, V. V. AN, V. M. SHOSTAKOVSKII and

2146-21 5 I


FUEL CELLS Fuel Cell Uses Methanol. Methanol is Source of Hydrogen for Hydrogen-Oxygen Fuel Cell that Generates 5 kw Electricity Chem. Eng. Nezus, 1964, 42, (52), 31 The Shell Research Ltd fuel cell generates up to 5 kw at 60°C by converting CH30H to H, and reacting the latter with air. The H, is purified by diffusion through Ag-Pd alloy. Electrodes are microporous PVC sheets with a Ag layer over which is a Pt metal catalyst layer. Each electrode is 85% porous and about 1.3 ftz, 0.03 in. thick. The electrolyte is alkaline, 62 cells in each of two batteries form a truck-mounted unit.

Fuel Cells. I. Propane on Palladium Cata- lyst. 11. Propane and Propylene on Adams' Platinum Catalyst. 111. The Propylene Potential in Low Temperature Cells M. FUKADA, c. L. RULFS and P. J. ELVING, Electro- chim. Acta, 1964, 9, (IZ), 1551-1562, 1563-1580, 1581-1586 Low temperature cells using gaseous hydrocarbons as fuels were studied. First, negative electrode catalysts of Pd, reduced by C3H8 at H,, supported on porous discs of Ni or C, in many cases waterproofed, were tested using gaseous C,H8 fuel, 30% KOH electrolyte, carbon-black air electrode, at 50°C. Repeated small current

NEW PATENTS METALS AND ALLOYS Spring Elements THE INTERNATIONAL NICKEL co. (MOND) LTD. British Patent 974,057 A spring for use at 5oo"C or above consists of an Ir alloy containing 0 .57 wt.% W and incidental impurities.

Commutator Devices for Micromotors HITACHI LTD. British Patent 975,299 A commutator device for micromotors has commutator segments made of 80-60 wt.% Ag and 20-40 wt.% Pd alloy and holders carrying in sliding contact with the segments metallic brushes made of 95-70 wt.% Pt and 5-30 wt.% I r alloy.

Improving the Ductility of Ruthenium THE INTERNATIONAL NICKEL co. (MOND) LTD. British Patent 981,535 The workability of Ru is improved by melting it under neutral conditions in contact with 0.05-5 wt. % of one or more of the elements : Zn, Cd, Bi, Ti, Ge, Ba, Hf, Ce, Er, Ga, Ho, La, Pr, Sm, Y or Yb and allowing it to solidify without changing the conditions.


discharges gave steady high open-circuit poten- tials and electrodes with fairly good discharge- rates. Fifteen discs of Adams' catalyst pressed with Ag powder were tested at 80°C in He, C3H,,C3H,, and H,. The effect of the period of electrode reduction on the potential with C3HG was studied. Finally, from the reproducible C3H, potential at the Pt catalyst in 30% KOH, at 25°C a potential of 0.465 V (NHE) was calculated compared to 0.838V for the C3HG-0, cell. Possible reaction mechanisms in C3HG cells are discussed.

ANODIC PROTECTION Anodic Protection of Stainless Steel by Galvanic Coupling with Platinum

Acts, 1965, 10, (I), 83-95 Stainless steel in H,SO, is passivated and does not corrode when coupled galvanically to Pt sheet with areas in suitable ratio; e.g. R = I with 38% H,SO, at room temperature; R = ~ o o with 52% H,SO, at 75°C. Tests with Pt, Pd and Au show that the efficiency of Pt for anodic protection of stainless steel is due to its dual effect on passivation, not shared by Pd and Au. Stainless steel first enters the zone of unstable passivity, since over-voltage of Pt for discharge of H+ is low; then it enters the zone of stable passivity, since 0, in solution is reduced more easily on Pt than on stainless steel.

G. BIANCHI, A. BAROSI and S. TRASATTI, Electrochim.

Precious Metals and Alloys THE INTERNATIONAL NICKEL co. (MOND) LTD. British Patent 981,792 A sheet or strip of Pt group metals or their alloys is produced by forming a compact of flake powder with or without alloying ingredients, heating so that sintering occurs and working the sintered metal to give the desired sheet or strip.

Electrical Resistors

U.S. Patent 3,154,503 An electrical resistor is produced by applying to a ceramic substrate and firing a vitreous enamel consisting of 99-50 wt.% glass frit including 1-24 wt.% Ag,O and 1-50 wt.% finely divided Pd, Pt or Rh.

Coating Glass or Refractory Oxides

French Patent 1,366,570 The thermal resistance of refractory metal oxide bodies or mixtures of silicates is improved and their corrosion by other materials is prevented by coating them with a Pt alloy containing 2-10 wt.% Rh and 0.5-10 wt.% Pd.

INTERNATIONAL RESISTANCE CO.

DEUTSCHE GOLD- 82 SILBER-SCHEIDEANSTALT

Spinnerets

German Patent 1,181,922 Longer spinneret life is achieved using alloys containing 25-409/, Rh and the remainder Pt.

DEUTSCHE GOLD- & SILBER-SCHEIDEANSTALT

ELECTROCHEMISTRY Coated Titanium Electrodes CANADIAN INDUSTRIES LTD. British Patent 974,320 An electrode particularly suitable as an anode in the electrolysis of brine consists of a T i core with a 10-200 p thick electrodeposited layer of an alloy of 35-60 wt.%, Rh and 65-40 wt.% Pt.

Activated Platinum-plated Titanium Anode

British Patent 974,570 An anode suitable for the electrolysis of an alkaline chloride solution is prepared by electroplating a T i member from H,PtCl, solution at 71-77OC to give an adherent amorphous coating of Pt which is then activated by heating above 316°C in the presence of an air stream containing hydrocarbon vapours, whereby catalytic oxidation of the vapours occurs over the entire surface of the Pt coating.

Production of Super-pure Hydrogen NIPPON JUNSINZO K.K. U S . Patent 3,155,467 Super-pure H, is obtained by passing a gaseous H, mixture at 500-600°C through a permeable wall of a Pd alloy containing 2-40 wt. % of at least one Group I B metal and 0.1-20 wt.% of at least one Group VIII metal other than Pd, e.g. Ag-Ru-Pd or Au-Pt-Pd.

Activation of Platinum Group Metals

French Patent 1,364,203 The Pt group metals, and in particular various electrodes coated with such metals, are activated by contacting them with an alkali metal amalgam, distilling off Hg at 260-482'C and recrystallising the Pt or Pt-Rh alloy film at 37r-537"C.

Hydrogen Diffusion Tubes CHEMETRON CORP. French Patent 1,367,110 An improved apparatus for the production of extremely pure H, uses an arrangement of 75 p thick Pd diffusion tubes.

UNIVERSAL OIL PRODUCTS CO.

JOHNSON, MATTHEY & CO. LTD.

ELECTRODEPOSITION Electrolytic Palladium Plating

U.S. Patent 3,150,065 Non-porous Pd deposits suitable for use as electrical contacts for printed circuit cards are obtained by using a Pt anode and connecting the

INTERNATIONAL BUSINESS MACHINES COW.

Platinum Metals Rev., 1965, 9, ( 2 )

substrate as a cathode in a diaphragmless bath solution containing 60 g/l palladosamine chloride, i o g/1 Na,Cl, 25 g/1 (NH,),SO, and 50 ml/l NH,OH.

Palladium or Platinum Plating Bath

German Patent I, I 82,924 Bath contains an aqueous solution of a complex dinitritoplatinate (11) or dinitritopalladate (11).

Platinum Electrodeposition THE INTERNATIONAL NICKEL co. (MOND) LTD. Dutch Application 212,633 Electrodeposition takes place using an aqueous chloroplatinate solution containing 10-50 g Pt and 180-300 g HCl at 45-90"C using plating conditions laid down in a diagram.

Platinum Plating Baths ASAHI KASEI K.K.K. Dutch Application 64.02,931 An electroplating bath consists of NH,, K or Na sulphamate dissolved in an aqueous solution of dinitrodiaminoplatinic acid. High gloss coatings can be obtained.

Chemical Deposition of Pd THE INTERNATIONAL NICKEL co. (MOND) LTD. Dutch Application 6403,078 Pd is deposited in adherent layers on surfaces by chemical plating from a bath containing Pd (11), an unsymmetrical dimethyl hydrazine and NH, and/or one or more aliphatic triamines.

JOHNSON, MATTHEY & CO LTD.

BRAZING Brazing Alloys THE INTERNATIONAL NICKEL co. (MOND) LTD. British Patent 976,660 A brazing alloy for the production of ceramic-to- ceramic and ceramic-to-metal joints consists of 30-75 wt.% Pd, 2-9 wt.% T i and the remainder, except for impurities, Ni, preferably taken in a 3 :z Pd :Ni ratio.

Brazing Alloys AEROJET-GENERAL CORP. US. Patent 3,148,053 Brazing alloys suitable for use in a vacuum furnace comprise r-77 wt. % Au, 1-59 wt. % Pd and 20-61 wt.% Ni, Cr or their mixtures.

CATALYSIS Removal of Alkynes from Hydrocarbon Mixtures

British Patent 974,038 Alkynes are removed from a hydrocarbon mixture containing alkadienes by passing a solution of H, dissolved in such a mixture together with gaseous H, in an upflow stream through a fixed bed con-

SHELL INTERNATIONALE RESEARCH MIJ. N.V.

67

sisting of a macroporous support carrying 0.1-5 wt.76 Pd catalyst.

Platinum and Palladium Oxide Catalysts in the Production of 2-Ethyl-pyridine WEB LEUNA-WERKE "WALTER ULBRICHT" British Patent 974,I 13 a-Ethyl-pyridine is produced by heating 2-(p-hydroxyethy1)-pyridine to 250-400°C in an H, atmosphere and in the presence of a catalyst consisting of A1,0, and Pd or Pt oxide.

Platinurn Group Metal Phosphatide Hydrogenation Catalysts CENTRAL SOYA CO. INC. British Patent 974,432 Phosphatide material is hydrogenated by contacting Pd, Pt, Rh or their mixtures supported on C, A1,0,, CaCO, or diatomaceous earth with H, and then contacting 0.05-1.0 wt.% of the hydrogenated catalyst with the phosphatide and H,.

Production of Snlphonamides CIBA LTD. British Patent 974,983 A Pd/C hydrogenation catalyst is used in the production of 1,4-endoalkylene-cyclohexane-2- sulphonamides by the reaction of sulphonyls with NH, or amine followed by hydrogenation and if desired also N-alkylation or N-acylation.

Derivatives of 1-Phenyl-2-aminoethanol

British Patent 975,291 The production of I-phenyl-2-aminoethanol derivatives involves a hydrogenation stage in the presence of Pt or Pd/C catalyst.

Production of Carboxylic Acid Esters

British Patent 975,709 Carboxylic acid esters of unsaturated monohydric alcohols are produced by contacting an olefine with a Pd salt, a carboxylate, which is ionised under the reaction conditions, and a redox system in a carboxylic acid.

Production of Cyclohexanone ALLIED CHEMICAL CORP. British Patent 976,339 Cyclohexanone is produced by the hydrogenation of phenol at 150-225"C, 2.46-10.5 kg/cm2 and in the presence of 5% Pd/C catalyst promoted with 1000-7000 p.p.m. of combined Na based on wt. of catalyst and 1-10 p.p.m. of phenol of an inorg- anic sodium compound.

Production of Aromatic Halogen-containing Compounds

British Patent 976,438 Halogen-substituted aromatic compounds are produced by subjecting an aromatic sulphonyl halide to thermal decomposition at 300-40Ooc

IMPERIAL CHEMICAL INDUSTRIES LTD.

IMPERIAL CHEMICAL INDUSTRIES LTD

MONSANTO CHEMICALS LTD.


and in the presence of I'd or Pt or an oxide or halide thereof as a catalyst.

Process for Preparing Esters

British Patent 976,613 Ethylenically unsaturated esters are produced by reacting an alkene in the vapour phase with a carboxylic organic acid and an 0,-containing gas in the presence of a catalyst comprising a Group VIII noble metal and/or its salt or oxide, e.g. Pd/C or PdX,, where X is halogen, or RhCl,.

Platinum Group Metal Catalysts

British Patent 978,261 Pt group metal catalysts are produced by intro- ducing an appropriate metal into a crystalline alumino-silicate zeolite, or into a reaction mixture for preparing such a zeolitey so that the metal is distributed on or within the crystalline structure of the zeolite, followed by thermal treatment at 250-1100~F so that the Pt group metal is catalytically activated.

Production of Cyclododecanone Oxime and its Hydrochloride

British Patent 978,497 The hydrogenation of 2-chlorocyclododecanone- (I)-oxime or a corresponding compound containing one or two olefinic bonds, if carried out at 0-130°C in an inert solvent and in the presence of dispersed, supported Pd or Pt catalyst, yields cyclododecanone oxime HCl.

Hydrocracking Process

British Patent 978,613 Hydrocarbon oils are hydrocracked at 288-454°C and 75-136 atm H, pressure in the presence of a catalyst containing 0.0~-3.0 wt.% Pd or other Pt group metal on a precalcined base consisting of 37-88 wt.yo SiO, and 63-12 wt.% A1,0,.

Alpha-acetoxypropionaldehyde AJINOMOTO CO. INC. British Patent 980,239 The reaction between liquid vinyl acetate and H, and CO at 3o-18o0C and above 50 kg/cmz pressure, if carried out in an organic solvent and in the presence of 0.001--1.0 g/l Rh in the form of its carbonyl, or Rh-containing substance which is converted to carbonyl under the reaction conditions, results in the formation of m-acetoxypropionaldehyde.

Preparation of Dipyridyls

British Patent 981,353 2,z'-Dipyridyls or their alkyl derivatives are produced by heating pyridine or its alkyl derivatives of t-jo-45o"C in the presence of 1-50 wt.%,

NATIONAL DISTILLERS & CHEMICAL CORP.

SOCONY MOBIL OIL CO. INC.

BADISCHE ANILIN- & SODA-FABRIK A.G.

UNIVERSAL OIL PRODUCTS CO.


alumina catalyst supporting about 5 wt.% finely divided Rh, 0 s or Ir.

Hydrazine Derivatives

British Patent 981,460 N,H, derivatives of formula OHPH-CH,-NR- NHR are produced by the hydrogen reduction of OHPH-CH2NR-NH, in alcoholic solution in the presence of R,CO and a PtO catalyst.

Hydrocarbon Conversion Catalysts

British Patents 981,691-9 Hydrocarbon conversion catalysts useful as catalysts for isomerisation, the production of halogenated hydrocarbons and dehydrohalogena- tion comprise a refractory metal oxide supporting o.oi-5 wt.% Pt group metal, preferably Pt or Pd, o.oi-ro wt.% alkali or alkaline earth metal and 1.0-15 wt.% retained halogen, preferably C1.

Platinum Catalyst for the Oxidation of Exhaust Gases

U.S. Patent 3~48,036 An exhaust gas converter uses as the oxidation catalyst A1,0, spheres supporting 0.i wt.% Pt.

Catalyst Structures

U.S. Patent 3,i-jO,OII Double skeleton catalyst structures are produced by applying a finely divided supporting skeleton material on a conductive substrate base, sintering at 6oo-11oo"C, embedding a finely divided Raney alloy of Pt, Pd, Re, Ag, W, Mo or Ni activated by a Pt group metal, sintering the laminate and dissolving out the soluble component.

Isomerisation Catalyst

U.S. Patent 3,150,073 A reforming and isomerisation process for hydrocarbons utilises 0.6 wt.% Pt/A1,0, catalyst, 0.5-5 moles H, /mole hydrocarbon and is operated at 600-950°F and ioo-600 p.s.i.g.

Production of Cyclohexane PHILLIPS PETROLEUM co. US. Patent 3,r5oYrg5 Activated charcoal supporting 0.01-5 wt.% Pt is used as a dehydrocyclisation catalyst in the production of C,HIZ from a mixture of n-C,HI4 and methylcyclopentane.

Dehydrogenation Catalyst EDOGAWA K.K.K.K. US. Patent 3,150,930 In the cyclic production of H,O,, tetra-hydro- anthraquinone is dehydrogenated to the corresponding anthraquinone at 80-3oo0C, I atm, with an C,H, or C,H, or H, acceptor and Pd catalyst supported by A1,0,, MgO,, etc.

T. J. SMITH & NEPHEW LTD.

THE BRITISH PETROLEUM CO. LTD

UNlVERSAL OIL PRODUCTS CO.

VARTA A.G. & SIEMENS-SCHUCKERTWERKE A.G.

CITIES SmVICE RESEMCH & DEVELOPMENT CO.

Decolourisation of Phthalic Acids

U.S. Patent 3,151,r54 Phthalic acids are decolourised by contacting their solutions in a polar solvent with Pt, Pd, Rh, but preferably PtO,, catalyst and H, at ioo-250°C and SO-zoo0 p.s.i. followed by acidification and recovery of crystalline acid.

Catalysts in the Preparation of Ketones

U.S. Patent 3,151,167 The contacting of an epoxide with an alcohol solution of [Rh(CO),], or [Ir(CO)J, causes a molecular rearrangement to R-CO-CH,R'.

Paraffin Conversion Catalysts PHILLIPS PETROLEUM co. U.S. Patent 3,151,180 6-2oC aliphatic paraffins are converted to the corresponding olefines by contacting them with an a-Al,O, of o.or-5 mz/g surface area supporting Pt, Pd or Rh, at 85o-io5o"F and at atmospheric to roo p.s.i.g. pressure and with 0.5-10 moles HZ per one mole hydrocarbon.

Catalysts

U.S. Patent 3,152,092 A Pt /Ale03 hydrogenative gasoline reforming catalyst is produced by forming sorptive Al,Os granules by the dehydration of bayerite, subjecting them to humidification and carbonation treatment, impregnating them with a Pt compound and heating at elevated temperature to provide a predominantly dry -q-AlzOs carrier with a minor amount of Pt-containing compound.

Hydrogenation Catalysts PHILLIPS PETROLEUM co. U.S. Patent 3,I52,i44 Sulpholenes are hydrogenated to sulpholanes by adding H,O, to the feed and hydrogenating in the presence of Al,03 or diatomaceous earth supporting Pt, Pd or their mixtures as catalyst.

Hydrocracking Catalysts

U.S . Patent 3,152,980 Hydrocarbon charges containing at least 1 wt.% pyrenes are hydrocracked in two stages in the presence of 0.05-20 wt.% Pt or Pd series noble metal supported on a composite of solid refractory oxides.

Hydrogenation Catalysts

U . S . Patent 3,153,095 N, N-Dialkylhydrazines are produced by contacting lower N, N-nitrosodialkylamines with 0.5-1.5 wt.% urea, biuret, etc., to prevent catalyst poisoning and then hydrogenating them in the presence of a refractory oxide- or C-supported Pt, Pd, Rh or I r catalyst.

RICHFIELD OIL CORPORATION.

DIAMOND ALKALI CO.

AIR PRODUCTS AND CHEMICALS INC.


COMMERCIAL SOLVENTS CORP.


Arylnaphthene Production STAMICARBON N.V. U.S. Patent 3,153,678 Aryl or alkaryl napthenes are produced by treating an aromatic hydrocarbon or an alkyl- substituted aromatic hydrocarbon with H, below 100 atm and 250°C in the presence of a hetero- polyacid, e.g. phosphomolybolic acid and 0.1-35 wt.% Pt, Pd, Ir, Os, Rh or Ru supported on a refractory oxide, based on the wt. of such acid.

Production of Hydrogen Iodide

US. Patent 3,154,382 HI is produced by reacting H, and I, at 100-400°C in the presence of a composite catalyst consisting of A1,03, 0.01-1.0 wt.% Pt and 0.1-8 wt.% halogen combined with A1,0,.

Demetallisation of Heavy Petroleum Oils

U. S. Patent 3,154,480 Metallic impurities are removed from petroleum residues boiling at 900-1500°F by contacting them with finely divided Pt/Al,O, catalyst, subjecting them at 200-600°F to high energy ionising radiation followed by separation of the catalyst on which the metallic impurities have been adsorbed.

Production of 5-Aminofurans

U.S. Patent 3,154,543 Catalytic hydrogenation of a nitrofuran in the presence of a solvent comprising CH,COOC,H, and absolute C z H 5 0 H in a 3:1 volume ratio and a catalyst consisting of charcoal supporting 5 wt.% Pd, if carried out at 2-3 atm, yields the corresponding 5-aminofurans.

Reduction Catalysts

U.S. Patent 3~54,584 Diaminotoluenes are produced by reducing dinitrotoluenes with H, in the presence of rg-r5o p.p.m. Pt or Pd catalyst and carrying out the reduction in H,O/C,H,OH mixture at IIO- 140T and 1-10 atm.

Oxidation of Olefines

Olefines are converted to carbonyl compounds by contacting them at 5o-16o0C and a p H of 0.5-6 with 0, and a liquid catalyst system comprising H,O, a Pt, Pd, Rh, Ru or I r salt and a redox system containing a metal showing several valencies under these reaction conditions.

Reforming Catalysts

U.S. Patent 3,155,605 Naphtha fractions are reformed catalytically by fractionating them to concentrate substantially all

EL PAS0 NATURAL GAS PRODUCTS CO.

ESSO RESEARCH & ENGINEERING CO.

THE NORWICH PHARMACAL CO.


PARBWERKE HOECHST A.G. U.S. Patent 3,154,586


alkyl cyclopentones in the lower naphtha fraction and reforming this fraction in the usual conditions in the presence of a steamed Pt/A1,0, catalyst and 0.001-0.7 wt.% S.

Catalytic Igniters

US. Patent 3,156,094 A catalytic ignition system incorporated into turbojet thrust augmentors utilises a fiow permeable Pt or Pt alloy disc and a metering disc dynamically loaded against the catalyst element.

Dehydrogenation Catalysts SHELL OIL CO. U.S. Patent 3,156,735 Olefinic hydrocarbons are oxidatively dehydrogenated by contacting them at 40O--j5O0c, in admixture with 0, with a catalyst comprising a low surface area solid support and 0.05-5 wt.% Au and Pt, Pd, Rh, Ru or Ir taken in a ratio of 0.2-25 atoms of Au per atom of the said noble metal.

Hydrocarbon Conversion Catalysts

U.S. Patent 3,157,590 An improved isomerisation-cracking process for petroleum distillates utilises a Group VIII metal catalyst, preferably 0.1-1 wt.% Pt or PtO supported on an active Si02-A1203 support.

Production of Cyclohexanone Oxime

U.S. Patent 3,r57,702 Cyclohexanone oxime is produced by hydrogenating nitrocyclohexane in the presence of a 5% Pd/C,H, black catalyst containing 1% of Mg promoter and Pb acetate in a 1 :s Pb :Pd ratio.

Isomerisation Catalysts

U.S. Patent 3,158,662 5-6 C paraffins are isomerised by contact with a supported Pt catalyst containing 0.3-0.6 wt.% Pt and 5-15 wt.% AlC1, at 200-400°F, 400-1500 p.s.i. and in the presence of Hz

Hydrogenation Catalyst

The hydrogenation of pyridylcarboxylic and pyridylalkanoic acids at O-IOO~C, I-1000 atm and in the presence of 0.5-5 wt.% Rh/C or Rh/A1,0, catalyst will result in the formation of the corresponding piperidylcarboxylic and C-piperidylal- kanoic acids.

Catalyst

The (PtC1,-C,H,), complex has been used as a catalyst in the production of organosilicon compounds by reacting aliphatically unsaturated compounds with those containing Si-H bonds.

GENERAL ELECTRIC GO., NEW YORK

CALIFORNIA RESEARCH CORE’.

E. I. DU PONT DE NEMOURS & CO.


ABBOTT LABORATORIES U.S. Patent 3,159,639

GENERAL ELECTRIC CO. U.S. Patent 3,159,662


Production of u- Acyloxy-propionaldehydes AJINOMOTO CO. INC. French Patent 1,361,797 The reaction in a liquid phase at elevated temperatures and pressures between a vinyl ester of fatty acids and H, and Co in the presence of a Rh catalyst yields a-acyloxy-propionaldehydes.

Precious Metal Hydrogenation Catalysts SHIONOGI & CO LTD French Patent 1,361,980 Unsaturated morphinanes may be hydrogenated with H, in the presence of Pt or Pd catalyst.

Glyoxal Production

French Patent 1,363,089 Glyoxal is produced by reacting C,H, at o-1oo"C with 1-40 wt.7: HNO, and in the presence of o.oo01--I wt.% Pd salt, preferably PdC1, or Pd(NO3) 2.

Hydrocracking Catalysts

French Patent 1,364,001 A catalyst for the hydrocracking of hydrocarbon oils consists of a refractory oxide of 50-90 wt.% SiO, and 10-50wt.y~ Al,O,,part ofwhichmay be replaced by MgO, or B,03, carrying 0.1-20 wt.?/, Ag or Cu and 0.1-5 wt.% Pd, Rh, Ru or their mixtures.

Hydrogenation Catalysts

ET DES ACIERES ELECTRIQUES D'UGINE French Patent 1,364,577 Methylamines are produced by the gaseous phase hydrogenation of HCN with H, at elevated pressure, below 250°C and in the presence of a refractory metal oxide-supported Group VIII noble meta1, preferably Pd or Pt.

Hydroforming Catalysts

French Patent 1,365,520 Gaseous or liquid hydrocarbons are hydroformed at 550-750°C above 7 kgjcm, and in the presence of 1.3-5.5 moles H,O, H, and 0.1-0.5 wt.% of a refractory oxide-supported Pt, Pd, Rh, Ru, 0 s or I r catalyst.

Isomerisation Catalysts

French Patent 1,365,885 Ethylenic hydrocarbons are produced by the isomerisation of ethylenic hydrocarbon mixtures in the presence of a catalyst comprising a complex of a Pt, Pd, Rh, Ru or I r halide and the ethylenic hydrocarbon, at elevated temperature and pressure.

Production of Organosilicon Compounds

French Patent 1,366,279 Organosilicon compounds are produced by


SHELL INTERNATIONALE RESEARCH MIJ. N.V.

STE. D'ELECTRO-CHIMIE, D'ELECTRO-METALLURGIE


THE BRITISH PETROLEUM CO. LTD.

COMPAGNIE FRANCAISE THOMSON-HOUSTON


contacting an aliphatic compound with an Si compound having at least one Si-H bond in the presence of an Rh catalyst produced by reacting RhC1,.3H,O with compounds capable of giving an olefinic, carboxylate or substituted organoxy complex of Rh.

Production of Alkyl Aromatic Compounds

German Patent 1,178,065 Diary1 alkanes are converted to alkyl aromatic compounds by heating at 300-600°C in the presence of a refractory metal oxide catalyst and also a Pt or Pd dehydrogenation catalyst.

BATAAFSCHE PETROLEUM MI]. N.V.

Beta-chloroalkyl Chloroformate Production

German Patent 1,179,922 The reaction of 1,z-alkylene oxides with phosgene in the vapour phase is catalysed by a Group VIII metal chloride on a support, e.g. Rh Cl,/Al,O,.

Production of Vinyl Carboxylatcs

The reaction of C,H,, 0, and carboxylic acid to produce vinyl acetate and higher homologues is catalysed by a mixture of a Pd, Rh or Pt salt and a Cu, Zn, Hg, Pb, Cr, Mn, Fe or Ni salt.

Removal of Formic Acid from 2-8C Fatty Acids

German Patent 1,180,360 HCOOH is removed from 2-8C saturated fatty acids by vapour phase degradation at 80-220°C using a catalyst consisting of 0.05-5 wt.% Pt/ A1,0, with a neutral surface and a specific area of 20-400 m2/g.

Production of Adipodinitrile

German Patent 1,181,197 Adipodinitrile is produced by the hydrogenative scission of 1,2-dicyanocyclobutane in the presence of Pt or Rh catalyst.

Partial Diene Hydrogenation

German Patent 1,181,700 Cyclic compounds with at least two double bonds are reduced to cyclo-olefines by molecular H in the presence of a Pd catalyst poisoned by Cu, Ag, Zn, Cd, Hg, Th, Pb, Sb, Fe, etc.

Catalyst SOCONY MOBIL OIL CO. German Patent 1,183,480 Mixtures of various Al,03,3H,0 are impregnated with a Pt compound to give 0.01-5 wt.% Pt in the final compound and HNO, and then dried and calcined.


NIPPON GOSEI K.K.K.K. German Patent 1,179,928

SHELL INTERNATIONALE RESEARCH MIJ.

E. I. DU PONT DE NEMOURS & CO.


Olefine Oxidation

German Patent 1,183,488 The oxidation of olefines to aldehydes and/or ketones is catalysed by a Cu salt catalyst activated with a Pd salt with a Cu:Pd ratio of ~o-~oo:I.

Reforming of Naphtha

Dutch Application 208,826 Pt/A1,03 catalyst is used in treating high S, high boiling naphtha in a multiple zone reformation process.

Hydrogenation of Tetracycline Precursors

Dutch Application 226,460 A supported Pd catalyst is used in the production of tetracyline by catalytic hydrogenation.

FARBWERKE HOECHST A.G.


AMERICAN CYANAMID CO.

q -Caprolactam Production TEIJEN LTD. Dutch Application 64.02,303 The caprolactam is produced from q-caprolactone, 7)-hydroxycapronamide or amides of 7-hydroxy- caproic acid by reaction with NH3 in the presence of a hydrogenation catalyst, e.g. Pt /C or Pd/C. (See also No. 64.02,312).

Hydrogenation of Hydrocarbons U.S. RUBBER co. Dutch Application 64.02,424 Organic compounds, such as heterocyclic compounds, are hydrogenated non-destructively using a Pt metal sulphide catalyst with H,.

Reforming Catalyst

Dutch Application 64.03,228 A catalyst consists of a noble metal deposited on a refractory oxide, e.g. Pt /A1,03, which has been modified with 0.05-1.5 wt.% S.

Selective Hydrogenation of Trienes J. R. GEIGY A.G. Dutch Application 64.04143 Pd catalysts can be used for selective hydrogenation when they are used in the presence of a cyclic compound source of H.

Production of Organic Isocyanates

Dutch Application 64.10,490 Organic nitro compounds are reacted with CO in the presence of a noble metal catalyst, e.g. PdCl,, to form organic isocyanates.

UNIVERSAL. OIL PRODUCTS CO.

AMERICAN CYANAMID CO.

FUEL CELLS Fuel Cells LEESONA CORP. British Patent 975,314 Electrodes for fuel cells are made by forming an

electrode structure by bonding a layer of zeolite to a ceramic structure or a zeolite layer of different pore size, ion-exchanging the naturally occurring ions of the zeolite for Pt, Pd, Rh ions and heating the composite at 600-1000°C to stabilise it.

Fuel Cells

British Patent 976,796 A fuel cell suitable for use with liquid com- bustible fuels comprises an electrolyte container, an aqueous electrolyte and an electrode assembly consisting of Pt coated wire screen anode and cathode placed 0-001--1.0 mm away on each side of a ro-lo% porous membrane with a 5-508 pore.

Hydrogen Diffusion Electrodes LEESONA CORP. U.S. Patent 3,148,089 Fuel cells utilise fuel electrodes in the form of H diffusion tubes constructed of Pd or Pd/Ag alloys containing 5-40 wt.% Ag.

Fuel Cell Electrodes IONICS INC. U.S. Patent 3,152,014 A fuel cell consisting of a pair of spaced porous electrodes each of which is in contact with an ion-permeable membrane uses as both oxidant and fuel electrodes a porous C impregnated with Pt or preferably a porous structure activated by Rh, Pt, I r or Pd.

Palladium Electrode for Fuel Cells

ET LUBRIPIANTS French Patent 1,368,109 An electrode for fuel cells operating at 150-30O"C is constituted by a thin Pd foil of practically negligible porosity yet permeable to H.

ESSO RESEARCH A N D ENGINEERING CO.

INSTITUT PRANCAIS DU PETROLE, DES CARBURANTS

TEMPERATURE MEASUREMENT Multi-junction Thermocouples G. S. BACHMAN British Patent 974,070 Multi-junction thermocouple suitable for refractory furnaces utilises wires of Pt used in conjunction with Pt-Ir or Pt-Rh alloy wires arranged so that, when part of the junction wire is eroded, the Pd wire or strip, placed between the junction wires, melts and provides a new hot junction.

Electrical Resistance Elements

British Patent 981,807 Electrical resistance elements suitable for use as heater elements or as thermocouple elements consist of a sintered refractory ceramic material core and a Pt group metal or its alloy as the external layer which will not alloy with the ceramic at the operating temperature.

JOHNSON, MATTHEY & CO. LTD.


PLATINUM METALS REVIEW...ketone (Fig. 4) or di-n-propyl ketone. The following is a very interesting...

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Transcript of PLATINUM METALS REVIEW...ketone (Fig. 4) or di-n-propyl ketone. The following is a very interesting...