ABSTRACTS: January 199132-46

(1)

ABSTRACTS

of current literature on the platinum metals and their alloys

PROPERTIES

Electrical Properties, Stability, and

Applications of Ultrathin Porous Pt Films

on

S i 0 2

Technol. A, 1990, 8 , (4), 3591-3597

The morphology of 25

di

porous Pt films deposited on thermally grown SiO, at mom temperature and 25OOC is presented. The impedance was measured over the range 100 Hz to 1 MHz. At 1 kHz, the impedance was measured in electric fields up to 250 V/cm at temperatures - 192 to 140OC. The AC impedance of the 25

hi

Pt fdm deposited at room temperature decreased by 25% in 21 days at 15OOC in room air, but the AC impedance of the Pt film deposited at 25OOC did not change.

Volatilization of Pt-Rh Alloys

at

High

Temperature

Met.), 1990, 11, (2), 12-17

Studies of the volatilisation of Pt-7Rh and Pt-Rh-Au alloys at high temperature showed that the volatilisation loss of the alloys at 1200-135OoC obey a parabola-straight line rule, and the transposition time from the parabola loss to straight line loss decreased with increasing temperature. The volatilisation loss increased with increasing Rh content and by addition of Au to

Pt-Rh

alloys. The activation energy of volatilisation of Pt-7Rh-3Au alloy is 167 kJ/mol.

Columnar Epitaxy of PtSi

on

Si(

11 1)

NIEH, Appl. Phys. Lett., 1990, 57, (7), 686-691 Columnar grains of PtSi surrounded by high quality epitaxial Si were obtained by ultrahigh vacuum codeposition of Si and

Pt

in an 8:l ratio on Si(ll1) substrates heated to 610-810OC. The areal density of columns varied from 120 to 3.8/pm1, and layers with thicknesses from 100 nm to 1 pn were displayed. The PtSi grains are also epitaxial and have one of three variants of the relation defmed by PtSi(OlO)//Si(l ll), with PtSiIOO11//Si<l lo>.

Properties of a Platinum-Yttrium-Boron

K. SCHWARZ and w. MOLLE, Neue Hiitte, 1990, 35,

The properties of a Pt-0.03Y alloy was improved by adding a small amount of B. The addition of B resulted in an increase in the rate of internal oxidation and a fme dispersion of the Y oxide particles was obtained. High creep rupture strength, a high creep resistance and a decreased grain growth were found. R. NOWROOZI-ESFAHANI and G. J. MACLAY,J. VUC. SCi.

Y. NING, D. DENG and Y. WANG, Guijinshu (Precious

R. W. FATHAUER, Q. F. XIAO, S. HASHIMOT0 and C. W.

Alloy

(lo), 391-393

Magnetic and Transport Properties of the

UTIn Series (T

=

Rh,

Pd and Pt)

v.

H. TRAN and R.

mOC,

J . Magn. M a p . Muter.,

Magnetic susceptibility, magnetisation, electrical resistivity and magnetoresistivity measurements have been performed for the U(Rh, Pd, Pt)In series crystallising in the hexagonal Fe,P type structure. Results for URhIn are reported for the first time. An- tiferromagnetic ordering in URhIn and UPtIn with a Nee1 temperature of 7 and 22 K and metamagnetic transitions in fields of

-

1.5 and 3.5 T a t 4.2 K have been observed, respectively. Resistivity anomalies at low temperatures have been observed. UPdIn was antiferromagnetic with a N&l temperature of 20 K.

Effects of High Concentration CO and

C 0 2

on

Hydrogen Permeation through

the

Palladium Membrane

M. MNO,

c.

NISHIMURA and M. KOMAKI, Muter. Ttans., JIM, 1990, 31, (5), 404-408

The effects of high concentrations of CO and C 0 2 on the H permeation characteristics of a Pd membrane 0.7 mm thick, 12 mm diameter cut kom cold-rolled Pd plate, followed by annealing were investigated us-

ing pure H I , H 2 - C 0 (10%,50%), and H2-50%C02 at 423-723 K and pressures 0.9-250 kPa. Deteriora- tion in H permeability and diffusivity in the Pd membrane occurred for H,-C0(10%,50%) gas below 523

K with a concentration dependence on CO, while only slight deterioration occurred for H,-50%C02 gas below 473 K. Results are explained by different adsorption energies of CO and CO, at the Pd surface. Deterioration in H 2 permeability is attributed to a decrease in effective area for H I dissociation by the weak adsorption of CO.

Kinetic Description of the Transition

from a One-Phase to a Two-Phase

Growth

Regime in

AlPd Lateral Diffu-

sion

Couples

1990, 88, (3), 287-294

B. BJANPAIN, J. W. MAYER, J. C. LIU and K . N . TU,

3.

Appl. Phys., 1990, 68, (7), 3259-3267

The kinetics of the solid-state reaction between

Al

and Pd is studied in the geometry of a lateral A-Pd diffusion couple at 250-43OOC. The f m t reaction phase is the crystalline AllPd2 (6) phase and after its growth to a critical length, the quasicrystalline decagonal

All

Pd(y’) phase starts to grow in between the

Al

and the AllPd2 phases. The first-phase All Pd I and second-phase

Al

Pd grow simultaneously. Excellent agreement between the data and the model is found. From the analysis the effective interface growth constant for the AllPd is extracted as a function of temperature.

(2)

Electrical Resistivity Changes Due

to

Interstitial Hydrogen

in

Palladium-Rich

Substitutional

Alloys

and T. B. FUNAGAN,

3.

Mater. sci., 1990, 25, (9),

The changes in electrical resistivity of Pd solid solution alloys, alloyed with Ag, Au, Cu, Y, Ce, Ti, Zr, V,

Nb

and Ta, with H concentration were measured at 301 K up to t(WM)=1.5 x lo-*. The H was introduced by electrolysis and measurements of electrode potential were also made. The specific electrical resistivity of H-free Pd alloys increased with increasing solute contents.

K. BABA, U. MIYAGAWA, K. WATANABE, Y. SAKAMOTO

3910-3916

Internal Oxidation of Pd-40Ag-1RE

(RE=Sm, Eu, Gd) Alloys and Their

Properties

Y. LI, H. DAI and Y. NING, Guijimhu (precious Met.),

The internal oxidation of Pd-4OAg-1RE (RE=Sm,

Eu,

Gd) alloy wires and their properties were studied in air at 800-1200°C. For the alloys containing Sm or

Gd, the oxidation rate along the grain boundaries was higher than that of grains in some parts. It is conclud- ed that the internal oxidation of Pd-40Ag-1RE alloys is controlled by volume diffusion.

Microstructural Stability of Diluted Pb-

Cu-(Sn-Se-Pd)

Alloys

Z . Metallkde., 1990, 81, (8), 594-600

The evolution of microstructure was followed in homogeneous, fme grained Pb-Cu, Pb-Cu-Sn-Se and Pb-Cu-Sn-Se-Pd alloy optically, by SEM and by microanalytical identification of phases and measure- ment of several microstructural parameters, at temperatures between 323 and 423 K for 4 to 700 h. Small Cu and Se additions substantially reduce Pb grain size; Pd acts as a grain stabiliser during heat treatments. Grain size distributions in one or two dimensions are lognormal and invariant with treatment temperature and time. The Pd containing alloys have high microstructural stability at the temperatures studied, making them suitable for chemical plant application.

1990, 11, (2), 18-22

A. DE LA TORRE, P. ADEVA, G. CARUANA and M. ABALLE,

Magnetic Properties of Nonequilibrium

Fe-Pd Alloys Produced by DC Triode

K. SUMIYAMA, H. FUJIMORI, M. KATAOKA, J. Y. KIM and

s. L. ZHANG, Jpn.

3.

Appl. Phys., Part 2, Lett., 1990,

Sputter-deposited Fe, -xPd, alloys of

-

1OOpm thickness were prepared by

DC

triode sputtering. The single b.c.c. phase was obtained for x = 0-0.25 in contrast to the MITOW single b.c.c. of x=O-O.O3 in the equilibrium phase diagram. The lattice constant and the magnetisation increased by annealing below 500 K and decreased by annealing above 500 K.

sputtering

29,

(3,

1261-1265

The

(a+/$

Hydrogen Miscibility Gaps

in

Hydrogenated Palladium-Rich Pd-Y (Gd)-

Ag Ternary

Alloys

3.

Less-Common Met., 1990, 166, (l), 45-56 Pd-rich Pd-Y(Gd)-Ag ternary alloys were investigated as possible diffusion membranes for H pdication, and their alloying behaviour and the extent of (a +/.I)

H miscibility gaps in hydrogenated alloys were studied. Metallographic and X-ray studies of anneal- ed P d ~ ~ ~ x ~ y ( Y ( G d ) ) , A g y alloy with a Ag content y of 5-24 at.% and x in at.% giving the value of the content of Y and/or Gd, indicate that every one of these alloys forms as a single a-Pd phase. It was found that the (a

+

p)

H miscibility gaps in the hydrogenated alloys with any given Ag content decrease gradually as the content of Y and/or Gd increases, and the critical compositions for the disappearance of the miscibility gaps are approximately isoelectronic.

Do Thermal Spikes Contribute

to

the Ion-

Induced Mixing of Ni

into

Zr, Ti, and Pd?

Appl. Phys. Lett., 1990, 57, (14), 1407-1409 Low-temperature ion beam miXing rates for Pd-Ni, Ni-Ti and Zr-Ni bilayers greatly exceeded binary col- lision estimates, and appeared quite sensitive to thermodynamic driving forces. In the absence of a temperature dependence such a behaviour is usually ascribed to interdiffusion within thermal spikes. It is suggested that interdiffusion within a thermal spike of the Vineyard-Johnson type is not the dominant mechanism.

Y. SAKAMOTO, F. L. CHEN, M. FURUKAWA and K. MINE,

P. BBRGESEN, D. A. LILIENF'ELD and H. H. JOHNSON,

On

the

Constitution of the Pd-Te System

up

to

28 at.% Te

M. KELM, A.

GRTZEN,

H. KLEYKAMP and H. PEN- TINGHAUS,

3.

Less-common Met., 1990, 166, (I),

The constitution of the Pd-Te system was completed in the Pd-rich range up to 28 at.% Te and at XOOOC. The solid solution between Pd and Te has a maximum Te content of 16.3 at.% at -77OOC. The system shows a eutectic with 23.0 at.% Te at 773OC. Three phases Pd,,Te, (19 at.% Te), Pd,Te, (26 at.% Te) and dimorphic Pd3Te (25 at.% Te) were observed in the subsolidus region.

Structure Changes

on

Relaxation of

Dif-

ferently Cooled Pdo.

s35Sio.165

Alloy

Glass

Mater. Sci., 1990, 25, (lo), 4477-4482

The radial distribution function

(RDF)

of X-ray diffraction was studied for liquid-quenched Pd, . 81J

Si,,. 165 alloy glasses in relation to cooling conditions.

The atomic distance ( r , ) , total co-ordination number (n) and volume (V) were obtained by a first peak of RDF. The faster the cooling rate, the larger the r ,

,

n and V become. Based on the relaxation theory, it is shown that linear changes in r ,

,

n and V with the thickness (0) indicate the reciprocal cooling rate. 125-133

Y. NISHI, H. =NO, S. UCHIDA and K. OGURI,

3.

(3)

High-Temperature Oxidation of

Rhodium

L. A. CAROL and G. S. MA", oxid. Met., 1990, 34, (1/2), 1-12

The oxidation kinetics of Rh were measured in air at 1 atm at temperatures 600-1000°C. The oxidation weight gain proceeds logarithmically at 6OO-65OoC, followed by power law behaviour at >800°C. The logarithmic growth kinetics comes from thickening of hexagonal

Rh,O,

scales. The transition reflects a thickening of hexagonal and orthorhombic Rh,O, scales. Over 800OC the growth kinetics result from thickening of a predominantly orthorhombic Rh,O, scale. At 1000°C the oxide becomes volatile.

The Controlled Oxidation of the High

Chromium Steel Alloys Fe40Cr and

Fe4OCr3Ru

M. J. VAN STADEN and J. P. ROUX,

&PI.

surf. sci.,

1990, 44, (4), 263-269

Fe40Cr steel with and without 3% Ru added were exposed to 0 at different temperatures in an UHV system to fmd out how the Ru enhanced the corrosion resistance of the alloy. Cr was oxidised before Fe in both Fe4OCr and Fe40Cr3Ru, but only in the Ru alloy did the

G

also enrich the surface, at temperatures over 275OC, to form a substantial oxide, possibly because of an attractive interaction between Fe and Ru in the bulk.

New

Compounds in the 30-40 at.% Ru

Range of

the

Rare Earth-Ruthenium

(R-Ru) Systems

A. PALENZONA and F. CANEPA, J . LeSS-COmnUm Met.,

1990, 162, (l), 267-272

New compounds were prepared and identified in the rare earth-Ru (R-Ru) systems and a complete compound formation scheme was constructed. Two new crystal structures were found and completely resolv- ed. Y,Ru, and Er,Ru,, while for a third one (RRuJ the complexity of the structure prevented any structural determination.

CHEMICAL COMPOUNDS

Complex Formation of Platinum with

Tm(II) in Aqueous Solution of Malic Acid

Obshch. Khim., 1990, 60, (8), 1846-1851

Studies of the interaction of K,PtCl, with SnCI,.ZH,O in 1 M malic acids at 2OoC showed the formation of bimetallic Pt(I1) complexes of anion type with maximum content of SnC, H, 0; ligands, with the molar ratio=5. Chloride ions in (Me, N) I [Pt(SnCl 1 and (Me, N)

[Pt

,

(SnCI,)

,

I

dissolved in the malic acid were completely replaced by malate-anions, thus preserving the Pt-Sn bond. During heating, Pt-Sn complexes undergo inter- molecular conversion, which result in the formation of bimetallic compounds with Pt oxidation order

-

1. P. G. ANTONOV, T. P. LUTSKO and I. A. AGANOV, Zh.

Synthesis and X-Ray Crystal Structure of

Trimesitylrhodium(III)

HURSTHOUSE and G. WILKINSON,

3.

Chem. soc., Chem. Commun., 1990, (18), 1242-1243

The first neutral homoleptic aryl of Rh(III), Rh(2,4,6-Me1C,H,),, was prepared by interaction of RhCl, (C, H, S)

,

and mesitylmagnesium bromide. X-ray crystal studies showed that there is "agostic" interaction between Rh and an orrho-CHi, group in a distorted fac-octahedral geometry but no evidence for agostic H bonding was found. H NMR spectra over a temperature range indicate synchronised rotation of the mesityl group about the Rh-C bond.

A

Novel Zwitterionic otho-Metallated

Ruthenium@) Phenolate

N. BAG, s. B. CHOUDHURY, G. K. LAHIRI and A.

CHAKRAVORTY,J. Chem. SOC., Chem. Commun., 1990,

Decarbonylative metallation of the dialdehyde by [Ru(PPh ,)

,

Cl

,

I produced the unusual complex [Ru(MeL)(CO)(PPh,) ,(CI)l. X-ray crystallographic studies showed that the Ru"P, C, ClO co-ordination unit has a single net negative charge and the Ru(MeL) fragment incorporates a four-membered C,O-chelated phenolato function with a neighbouring monoprotonated azomethine moiety.

Preparation of Uniform Colloidal Metallic

Ruthenium and Its Cornpounds

R. S. HAY-MOTHERWELL, B. HLlSSAIN-BATES, M. B.

(22), 1626-1627

F. PORTA, W. P. HSU and E. MATIJEVIC, COhidS surf.,

Colloidal spherical particles with narrow size distribution of a Ru double salt, (NH,)

,

Ru"10(NO).2Ru1VOC0, S H , 0 were obtained by ageing solutions of RuCl, containing K, SO, and urea at elevated temperatures. The amor- phous product was readily converted to RuO, by calcination at 400%. The same original powder, dried and heated at 250-3OOOC in a stream of H, yielded metallic Ru.

1990, 46, (l), 63-74

ELECTROCHEMISTRY

Electrochemical Behaviour of Basal

Single Crystal Pt Electrodes in Alkaline

Medium

E. MORALL~N, J . L. V k Q U E Z and A. ALDAZ,

3.

Elec- troanul. Chem. Interfacial Electrochem., 1990, 288,

The electrochemical behaviour of basal single crystal Pt electrodes in 0.1 M NaOH has been studied. The voltammogram for the Pt(ll1) surface orientation shows two clearly defmed zones; one corresponds to weak H adsorption states and the other could ten- tatively be assigned to strong H adsorption states. The voltammogram for a pt( 100) surface shows four different H states while for the Pt(ll0) orientation only one H state is obtained.

( 1 8 ~ 2 ) ~ 217-228

(4)

Electrochemical Oxidative Cleavage of

the

Platinum-Hydrogen

Bond

in

truns-[PtHCl(PEt

3)

I

L. CHEN and J. A. DAVIES, h r g . China. Acta, 1990, 175, (l), 41-45

The electrochemical oxidation of the Pt(I1) hydride, nuns-[PtHCl(PEt,),l, in CH,CN containing NBu,ClO, at a Pt gauze electrode produces almost exclusively Pt(I1) complexes as products, none of which contain Pt-H bonds; zrans-[PtCl(solvent) (PEt,),]+ is the major oxidation product. Titrations on the electrochemically oxidised solutions show that

Pt-H

cleavage occurs with H+ formation. The overall oxidation process is therefore: H-

-.

H + and not

Pt(II)

-+ Pt(1V).

Reactor Control and

Reaction

Kinetics

for

Electrochemical Urea Oxidation

J. F. PATZER, S. K. WOLFSON and S. J. YAO, Chem. Eng. Sci., 1990, 45, (8), 2777-2784

The electrochemical oxidation of urea on anodic

Pt

surfaces to NH, and C 0 2 was studied in the range 0.5-1.1

V

relative to Ag/AgCl to develop a model to mimic the experimentally observed phenomena. The model indicates maximum urea current utilisation can be achieved by appropriately controlling the applied current density in the system.

The

absolute urea conversion rate can be maintained by increasing the available Pt surface m a .

A New Fluoride Resistant Ceramic Elec-

trode

for

Electrochemical EMuent Treat-

ment Processes

s. K. HARNSBERGER and I . ROMODA, Plat. Sut$ Finish., 1990, 77, (7), 40-42

The effect of F ion on two inert anode materials,

Pt-

clad

Nb

and Ir oxide-coated Ti, and a new Ir oxide- coated Ti suboxide ceramic electrode was determined to find its effect when used for treating electrolyte ef- fluent. The materials were tested under laboratory conditions in a HI SO, acid-based fluoride containing solution. The ceramic material had superior corrosion resistance and hence longer life than either of the metal oxides.

Corrosion

Resistance

and

Electro-

chemical Behaviour of Platinised Porous

Titanium Electrodes

in

Acid Media dur-

ing

Water Electrolysis

L. S. NANOVA, T. G. BOGATSKAYA, L. A. MIKHAILOVA, S. G. OGRYZ’KCbZHUKOVSKAYA, L. M. YAKIMENKO, G. P. BELYAKOV, A. G. VAGANOV and S. D. KHODKEVICH, Elecmkhimiya, 1990, 26, (6), 696-700

Studies were performed of the corrosion resistance of platinised porous Ti electrodes with a Pt layer deposited either galvanically or by ionic coverage us- ing a magnetron, on thin (0.5 mm) porous (30%) Ti base during polarisation by a high density current of up to 1.0 Ncm’ in 10% H I SO, solution. Cumulative data of tested elecuodes in a compartment with solid polymeric electrolyte are given.

Rectifying Bilayer Electrodes: Layered

Conducting Polymers on Platinum

w.

TORRES and M. A. FOX, Chem. Muter., 1990,2, (3),

The preparation of sequential bilayer structures made from any pair of polybithiophene, (I), polypyrrole, (11) and poly(3-bromothiophene), (III) by anodic electropolymerisation on Pt electrodes is described, and the electrochemical properties of the junction between the two conducting polymers are discussed. The polymers in the outer layers of the electrodes PtAAI and PtAIIAI can be trapped in the oxidised state for several hours and charge can be released from the outer layers via an appropriate redox couple in solution.

Hydrochloric Acid Electrolysis

Using

Solid Polymer Electrolytes.

II. Gas Purity

and Current Efficiency

and H. TAKENAKA, Denki Kagaku, 1990, 58, (51,

459-464

Current efficiencies and purities of H and c1 in HCl acid electrolysis by membrane-elecuocatalyst com- posites of Ir-PtNafion 117iPt-Ir prepared by chemical plating were investigated over the range 1.7-12 molkg HCl concentrations, and temperatures 25-75OC and current densities up to 100 Ndm2. Cathodic current efficiencies of 97-98% were found.

The Electroxidation

of

Methanol

in the

Potential Region of Platinum-Oxygen

Layer

H. MTSUI and A. KUNUGI, Bull. Chem. SOC. Jpn.,

Methanol oxidation at a

Pt

electrode in 0.5 mol/dm’

H2 SO, at high potentials was retarded by the formation of an 0 layer and a new type of retarding substance from MeOH. During retardation due to the formation of 0 layer, the rate of MeOH oxidation decreased and increased with increasing 0 coverage and potential, respectively. Reverse effects in 0

coverage and potential concurrently occurred when the potential was variable. At low 0 coverage, the decreased effect from 0 coverage was more notable than the increased effect from the potential, but this reversed at medium coverages.

Electrochemical Activity

of Silicides of

Some Transition Metals

for

the Hydrogen

Evolution Reaction

in

Acidic Solutions

306-31 1

I. UEHARA, Y. KAWAMI, N . WAKABAYASHI, M. MOTONE

1990, 63,

(3,

1427-1432

A. K. VIJH, G. BELANGER and R. JACQUES, h t .

J.

Hvdmgen E w ~ , 1990, 15, (ll), 789-794

The H evolution reaction was examined on silicides of transition metals in H,SO, solutions. The highest rates were observed on Pt and Pd silicides, followed by those of Cu, Cr and Ni. If Fe silicides are used as typical transition metal silicides their electrocatalytic activity for the H evolution reaction is enhanced con- siderably by electrodepositing traces of Ru, and especially

Pt

on their surfaces.

(5)

Morphological Changes

in

Silver

Col-

loidal Particles during Oxidative Treat-

ment

in

Complex Solutions of Gold and

Palladium

STASHONOK, Vest. Akad. Navuk BSSR, Ser. Khim.

The treatment of polychromatic imaging Ag particles in H,PdCI, and HAuCl, solutions resulted in a change in the spectral and colour properties of an im- age. During the process, the spectral Ag particles transform to Ag shells with Pd and Au particles being ultradispersed on a surface.

Poly@yrrole-2,2'-bipyridyl Rhodium(m)

Complexes)

Modified

Electrodes:

Molecular Materials

for

Hydrogen Evolu-

tion and Electrocatalytic Hydrogenation

vLAcnornuLos,

3.

Electmanal. Chem. Interfacial

Electmchem., 1990, 291, (1&2), 243-249

The synthesis and electropolymerisation of new [Rh"'(L),Cl,]+BF,- complexes, where L = 2,2'- bipyridine bearing pendant pyrrole units, and the electrochemical behaviour of the resulting polymers are examined. Films of this material are highly stable for bulk electrocatalytic reactions, especially for effi- ciently reducing water to H , and for the hydrogenation of cyclohexanone to cyclohexanol.

The

Electrochemical

Reduction

of

**Cp*Rh Complexes**

u. KOELLE,

3.

Electrwnal. Chem. Interfacial Elec-

The electrochemical reduction of ICp*RhCl,l,(l) or [(Cp*Rh)@-Cl), IPF, (2) in methylene chloride and acetone and of [(Cp*Rh)(pOH),lPF, and Cp*Rh(acetone),'+ in acetone was investigated by cyclic voltammeuy and coulomeuy. An involved stepwise reduction sequence with electron transfer,

Cl- loss and disproportionation from (1) or (2) produces the novel blue, air-sensitive, binuclear RU" species [Cp*RhClll.

Application

of

Ion ImplantationlRBS

to

the Study of Electrocatalysis

E. J. KELLY, C. E. VALLET and C. W. WHITE,

3.

Elec- tmchem. SOC., 1990, l37, (8), 2482-2491

Ir-implanted Ti near-surface alloys were prepared by ion implantation, characterised by Rutherford backscattering (RBS) and subsequently anodically oxidised to form electrocatalytically active Ir,Ti ,-,O, /Ti electrodes, and their electrochemical behaviour in acidic chloride, sulphate and perchlorate solutions was studied. The specific catalytic activities (rate per catalyst surface site) of Ir,Ti,-,O,/Ti and Ru,Ti I -,O, /Ti and their relative catalytic activities were evaluated. Ir,Ti, .,O

,

/Ti was only 45% as effective a catalyst for Cl, evolution as Ru,Ti I .,/Ti, but it was far more stable, with a corrosion rate of only 5% that of Ru,Ti, .,O,/Ti.

M. V. ARTEM'EV, G. A. BRAMTSKII and B. D.

N m k , 1990, (3), 33-37

I. M. F. DE OLIVEIRA, J.C. MOUTET and N.

mchem., 1990, 292, (1&2), 217-229

Catalytic Oxidation of Methanol by

Ruthenium Oxides

B. J. KENNEDY, A.

w.

SMITH and F. E. WAGNER, Awt.

J. Chem., 1990, 43, (9, 913-921

The electrocatalytic behaviour of Ru oxidelC electrodes for 0 evolution and MeOH oxidation in acid solutions is reported. The electrodes were characterised by various techniques which showed the Ru to be present as a mixture of Ru" oxides, including the stable rutile phase. Electrochemical studies show that a Rum species promotes the catalytic oxidation of MeOH, while surface-bound RuO, is involved in the 0 evolution reaction.

Topotactic

Two-Phase

Reaction

of

Ruthenium Dioxide (Rutile)

in

Lithium

Nonaqueous Cell

T. OHZUKU, K. SAWAI and T. HIRAI,

3.

Electrochem.

Electrochemical and X-ray diffraction studies were performed for the reduction of RuO, with r u d e structure in 1M LiClO, propylene car- bonate: 1,2-dimethoxyethane (1: 1) solution. RuO, was topotactidly reduced to LiRuO, which is othorhombic via an intermediate phase having a tetragonal lattice. The reaction was reversible. Although three phases coexisted during the reduction of RuO, and oxidation of Li,,,RuO, the reaction was classified as a topotactic two-phase reaction where an intermediate phase existed between the

RuO,

and LiRuO, phases.

SOC., 1990, 137, (lo), 3004-3010

PHOTOCONVERSION

A n Ultramicrostructured Photoelectrode

System Composed

of

TiO, Single Crystal

and Layered SiO, and Pt Thin

Film

Len.

Jpn., 1990, (8), 1343-1346

An ultramicrostructured photoelectrode system composed of a TiO, single crystal and thin fdms of SiO, and Pt was prepared by exposing the vertical section of the layered SiO, and Pt f h . The SiO, layer is -140 nrn thick. The electrode showed photoresponse under irradiation in the presence of

NH3,

water vapour, EtOH and acetone. This may be the first microphotoelectrode system which can work in the gas phase.

Photocatalytic One-Step Syntheses of

Cyclic

Imino

Acids by Aqueous Semicon-

ductor Suspensions

K. IZAWA,

3.

Org. Chem, 1990, 55, (21), 5551-5553 Photocatalytic cyclisation using aqueous suspensions of TiO, or CdS loaded with

Pt

oxides under

Ar at

room temperature was applied to the one-step syn-

thesis of optically active cyclic imino acids, pipecolinic acid and proline from the cr,w-diamino carboxylic aads and their Nu-substituted derivatives.

M. HIRAMOTO, K. HASHIMOT0 and T. SAKATA, Chem.

B. OHTANI, S. TSURU, S.-I. NISHIMOTO, T. KAGIYA and

(6)

A Direct Absorber ReactorlReceiver for

Solar Thermal Applications

R. E. HOGAN, R. D. SKOCYPEC, R. B. DIVER, J. D. FISH, M. GARRAIT and J. T . RICHARDSON, chem. Eng. sci.,

1990, 45, (8), 2751-2758

A novel catalytic reactor concept of 3.5 kW is described where concentrated radiant solar energy is directly absorbed on Rh/Al,O,, thus avoiding the heat- transfer limitations of conventional tubular reactors for high-flux conditions.

Photocatalytic Asymmetric Reduction of

3-Methyl-2-Oxobutanoic Acid with Chiral

R

h

o

Complexes and Powdery Semicon-

ductors

H. WANG, T. SAKATA, M. AZUMA, T. OHTA and H. TAKAYA, Chm. h t t .

3p.,

1990, (8), 1331-1334 Photocatalytic asymmetric reduction of the title acid giving 2-hydroxy-3-methylbutanoic acid has been performed at up to enantiomeric excess of 60% in aqueous MeOH with chiral BINAP-Rh(1) complexes and semiconductor photocatalysts, TiO, or

U S .

The efficiency of the asymmetric reduction is still low, but the asymmetric hydrogenation of a-ketocarboxylic acid has been obtained without using H,

.

Simultaneous Photodissociation of

H,

and PMe

,

Ph from OsH, (PMe, Ph)

:

Pro-

duction

of Dimeric and Paramagnetic

Osmium Polyhydrides

J. W. BRUNO, J. C. HUFFMAN, M. A. GREEN, J. D. ZUBKOWSKI, W. E. HATFIELD and K. G. CAULTON, Orga~metallics, 1990, 9, (9), 2556-2567

Concurrent photodissociation of H, and PMe,Ph

(=P)

from OsH,P, in benzene, THF and EtOH has been proved by chemical trapping. It is the fmt polyhydride to undergo two distinct photoprocesses with comparable efficiencies. The fmal products observed on photolysis of OsH, P

,

under vacuum is an equilibrium mixture of Os,H,P, and Os,H,P,. The former is also photosensitive, leading to products of P-CH

,

cleavage (0s

,

H, (PMe

,

Ph), (p-PMePh) ,),

as well as to a product of Os-H heterolysis, tOs,H,P,+l [trans-OsH,P,-l, which contains a uni- que paramagnetic polyhydride anion.

Spectral,

Photophysical

and

Photochemical Properties of Ru(bpy)

*

+

on Porous Vycor

Glass

H. D. GAFNEY, Coord. Chem. Rev., 1990, 104, (l),

The properties of Ru(bpy)

:+

adsorbed on porous Vycor glass have been charactaised. The complex is immobilised on the glass surface and can be quenched by 0,

,

N,O and SO2. Other forms of quenching are discussed, as are the few differences in behaviour due to the Ru being on a solid support and not in a fluid medium. The net photoredox chemistry initiates with a two-photon ionisation of Ru(bpy)

:+.

Electron con- duction may occur by a surface mechanism. 113-141

A Luminescence Quenching Study on the

Localization Problem of R~(bpy)~’+

in

Micelles and Hemimicelles

J. T. KUNJAPPU, P. SOMASUNDARAN and N. J. TURRO,

3.

Phys. Chm., 1990, 94, (l), 8464-8468

Quenching studies on the luminescence emission of compound Ru(bpy)

:+

with femyanide ion, 9-methylanthracene and dioxylstearic acids were carried out in hemimicellar and micellar aggregates to gain insight into the location of this Raman and luminescence probe. Ru(bpy)

,*+

is bound to a more nonpolar hemimicellar hydrophobic region. Stern- Volmer constants for the doxylstearic acid quenching of its luminescence in micelles indicated that the optical electron in the metal-ligand charge-transfer state of the probe molecule resides in a bipyridyl ring which appears to be close to position 7 of the stearic acid chain.

Conversion of Light

into

Electricity with

Trinuclear Ruthenium Complexes

Ad-

sorbed on Textured Ti02

Films

VLACHOPOULOS and M. GRXTZEL, Helvetica Chim.

A series of CN-bridged trinuclear Ru complexes of structure

[RuL,(p-(CN)Ru(CN)L,‘),I,

where L = 2,2‘-bipyridine-4,4-dicarboxylic acid and L’=2,2’-bipyridine (l), and other bipyridines, etc, have been synthesised. The two carboxylic functions act as interlocking groups through which the dye is attached at the TiO, film surface. The interlocking groups provide strong electronic coupling, allowing charge injection to proceed at quantum yields close to 100%. Monochromatic incident photon-toturrent conversion effxiencies are >SO% in some cases. Regenerative cells with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have optimal results with (l), giving a fd factor of 75% and a power conversion efficiency of 11.3% at 520 M. K. NAZEERUDDIN, P. LISKA, J. MOSER, N .

Acts, 1990, 73, (6), 1788-1803

nm.

Design of Antenna-Sensitizer Poly-

nuclear Complexes. Sensitization of

Titanium

Dioxide

with

[Ru(bpy),

R. AMADELLI, R. ARGAZZI,

c.

A. BIGNOZZI and F. SCAN- MI LA,^. Am. chem.

soc., 1990,112,

(20), 7099-7103 The use of antenna-sensitiser molecular devices is proposed as a possible strategy to increase the light harvesting eficiency of sensitised semiconductors. The cyano-bridged trinuclear complex

and stuhed. The complex adsorbs on T i 0 2 via the negatively charged -Ru(bpy(COO) ,)

,-

central unit. Photophysical and photoelectrochemical studies were performed and emission and excitation spectra showed that in this complex the light energy absorbed by the terminal Ru(bpy) ,(CN)

,

(antenna) groups is eff- ciently funnelled to the central -Ru(bpy(COO),),- (sensitiser) fragment.

(CN)

2 I 2

RU(bPY(C00)

2

1

2 ,

-

t Ru(bpy!, (CN), 1 Ru(bpy(COO)

,

1 I’-

was prepared

(7)

ELECTRODEPOSITION AND

SURFACE COATINGS

Deposition of Transition Metal and Mixed

Metal

Thin Films

from Organometallic

Precursors

H. D. KAESZ, R. S. WILLIAMS. R. F. HICKS, J. I . ZINK. Y.-J. CHEN, H.-J. MihLER, 2 . XUE, D. XU, D. K. SHUH

527-534

and Y . K. KIM, New

3.

Chem., 1990, 14, (6/7),

High purity films of Pt, Ir, Rh, Ni and Re have been grown by organometallic chemical vapour deposition OMCVD (a), while thin fdms of Pt, Rh or Ir have been grown by photo-assisted OMCVD of volatile hydrocarbon precursors, but these contained more C than films grown under (a). Short-path OMCVD for organometallic precursors of limited volatility was used to deposit films of intermetallic compounds, PtGa, and CoGa. Substrates to be coated are placed in the reaction tube at the temperature needed for controlled decomposition of the precursor complexes. The various hydrocarbon derivatives, carrier gases, substrates, light sources, temperatures and means of producing thin films are discussed.

Preparation of Thin Palladium

Films

by

Use of an Electroless Plating Technique

s. UEMIYA, H. s w , T. MATSUDA and E. KIKUCHI, Nippon Kagaku Kaishi, 1990, ( 6 ) , 669-675

An electroless plating technique was used to prepare supported thin Pd fdms permeable only to H. Before plating, Pd nuclei were depositied on the outer surface of a porous tube by sensitisation and activation treatments with Sn(1I) chloride and Pd(I1) chloride solutions, respectively. The rate of Pd deposition during plating was related to the Pd nuclei concentration, which increased with repeated number of treatments. Sn deposition retarded Pd deposition, but treating with AgNO, solution before activation promoted the formation of Pd nuclei. An alkaline solution was used to plate the Pd on the porous glass tube, twice as fast as conventional plating methods.

APPARATUS AND TECHNIQUE

An Oxygen Sensor Composed

of

Tightly

Stacked

Membrane/Electrode/Elec-

trolyte

K . KATAKURA, A. NOMA, z . OGUMI and 2.-I. TAKEHARA, Chem. Lett. Jpn., 1990, (8), 1291-1294

An 0, sensor which operates at room temperature has been constructed using Nafion, a porous Pt cathode directly deposited on Nafion and a polyethylene (PE) film directly covering the cathode surface. The sensor is amperometric and all the com- ponents are tightly stacked. The 0, reduction current is limited by the 0 diffusion rate through the diffusion-limiting PE fdm and it changes in propor- tion to 0 concentration of gases up to 100%.

Platinum Metal Etching

in a

Microwave

Oxygen Plasma

c . H. CHOU and J . PHILLIPS,

3.

Appl. Phys., 1990,65,

The etching of Pt foils in an 0 plasma generated in a flow-type microwave system was studied as part of a general effort to understand the etching of metals in both plasma and chemical systems. It was found that very rapid etching ( - 6 k s ) took place even at low power inputs of 200 W. The principal plasma parameters, including oxygen atom and ion concentrations, and electron temperature, were measured as a function of distance below the microwave coupler. Etching of pt in an 0 plasma jet resulted from the concomitant action of 0 atoms and high energy electrons.

( 5 ) , 2415-2423

Use of Oxide Electrodes for Proton-

Conductor

Gas

Sensor

N. MIURA, K . KANAMARU, Y . SHIMIZU and N. YAMAZOE, Solid State Zonics, 1990, 4 / 4 1 , (Part I),

An amperometric proton-conductor CO sensor operative at room temperature was developed by using a Pt/SnO, and a Pt/WO, electrode. The CO sensitivity of this sensor was about 7 times higher than the H, sensitivity and the 90% response time was

-

3 minutes. The sensor became H, selective when a Pt- black electrode was combined with a Pt/WO, electrode. Sensing mechanisms are discussed.

452-455

The Hydrolysis

Products of cis-Dichloro-

diammineplatinum(I1). 3.

Hydrolysis

Kinetics

at

Physiological pH

s. E. MILLER and D. A. HOUSE, Znorg. Chim. Acta,

The rate of hydrolysis of cis-PtCI,(NH,), has been measured in non-buffered aqueous solutions at I =0.2 M NaClO, and T=45OC at constant pH over the range 4.0-8.5; the reverse reaction was also monitored. This allowed models for the hydrolysis of cis-PtCI,(NH,)

,

under physiological conditions to be tested, and shows that the Rosenberg model for Pt(I1) transport in vivo may need modification.

1990, 173, (l), 53-60

Study by UV-Visible Potential-Modulated

Reflectance

Spectroscopy

of

the

Chemisorption of

CO, Methanol and

Ethanol on Several Noble Metal Elec-

trodes

1. A. CARAM and c . GUTI~RREZ, J. Electroanal. Chem. Interfacial. Electrochem., 1990, 291, (1&2), 289-294 The title method has been used as a technique to determine the energy of electronic transitions in chemisorbed carbonyls and the type of bonding of CO. This was used to examine the electroadsorption of CO, MeOH and EtOH on Pt, Pd, Rh, Ru and Au electrodes. A maximum is reported, which depends only on the type of bonding of CO to the surface, i.e. linear, bridge-bonded or multiply bonded.

(8)

Manufacture

and

Performance

of

Rhodium/Carbon

Mdtilayer

X-Ray

Mirrors

P. BOHER, P. HOUDY, P. KAIKATI, hi. OUAHABI and R. BAR~HEWITZ, Appl. Phys. Lett., 1990, 57, (8),

A diode r.f. sputtering technique was used to produce Rh/C multilaym for application in the soft X-ray region. In situ kinetic ellipsometry, grazing X-ray reflectivity and absolute soft-X-ray reflectivity are us-

ed to make measurements. A model assuming a quasi-sharp

C-Rh

interface (4

hi

thick) and a diffus-

ed Rh-C interface (22

hi)

in the stack is used to fit the reflectivity curves at three experimental wavelengths. Reflectivities as high as 22% at 13.3

hi

and 24% at 44.7

A

were measured on a 17 riod multilayer strumre having a period of =69 r O n e interface is relatively ideal and it is sufiicient to give good reflectivities.

The Use of RuO,

in

Studies of Polymer

Blends by Scanning Electron Microscopy

B. OHLSSON and B. TORNELL,

3.

Appl. Pol$n. Sci.,

Flat samples of blends of polypropylene (PP) and

styrene-ethylene-butylene-styrene (SEBS) were con- trasted with RuO, and studied by SEM having a back-scattering electron (BSE) detector. The SEBS phase had bright areas with dark dots and the PP phase was dark. The dots were unstained

EB-

domains of the triblodr SEBS polymer. This method gave high resolution images due to the intrinsic electrical conductivity on the surface from the deposited Ru species; the RuO, vapour gave electrical conductivity to the stained areas. This method allows a BSE detector to be used in morphological studies.

834-836

1990, 41, (5/6), 1189-1196

HETEROGENEOUS

CATALYSIS

A Heterogeneous “Ligand-Accelerated”

Reaction: Enantioeelective Hydrogena-

tion

of Ethyl Pyruvate Catalyzed by

Cinchona-Modified Pt/AI

0 ,

Catalysts

M. GARLAND and H.-U. BLASER, J . A m Chem. Soc.,

The effect of low modifier concentrations on the rate and enantioselectivity of ethyl pyruvate hydrogenation catalysed by Pt/AI,O, modified with 10,lldihydrocinchonidine (HCd) was studied in order to test the concept of “ligand-accelerated” catalysis for a modified heterogeneous system. The reaction mechanism was found to be in complete agreement with a simple two-cycle mechanism. The adsorption of HCd on the

Pt

surface must be reasonably strong and/or only a small fraction of the surface Pt is modifiable. Simple geometric considera- tions indicate that a modified ensemble should be one adsorbed cinchona molecule and 10-20 Pt atoms.

1990, lU, (19), 7048-7050

Sulphur-Resistant Character

of

Titania-

Supported Platinum Catalysts

Y. CHEN, Y. CHEN, w. LI and

s.

SHENG, Appl. Catal.,

The resistance of Pt/TiO, catalysts to H,S was studied by pulse reactions with Pt/AI,O, as a reference. Pt/TiO, was found to be much more resistant than Pt/AI,O, to H , S poisoning. The results showed that in TiO, there is labile 0 that can react with H,S to form SO, or SO,, which leave the catalyst. Thus, with the F’t/TiOz system a con- siderable part of S contamination is “auto- regenerated” and the poisoning effect of S on

Pt

is therefore mitigated. However, for the Pt/AI,O, system, H,S decomposes on Pt giving H, and

PtS.

1990, 63, (l), 107-115

Study of Pt-Ga/Al,O,Catalysts.

I. The

Reaction of n-Hexane over Pt-Ga/AI,O,

(Dalian, China), 1990, 11, (4), 259-264

The reduction and chemisorption properties of the Pt-Ga/Al,O, catalysts were studied during n-heme conversion in a flow microreactor. The addition of Ga into Pt/AI,O, improved its stability, and the catalyst containing >3.5% Ga promoted n-hexane conversion. The selectivity for aromatisation, isomerisation and hydrocracking could be adjusted by changing the Ga content of the catalyst.

Role

of

Sulfur

in

Catalytic Reforming of

Hydrocarbons

on

Platinum-Rhenium/

Alumina

Eng. Chem. Res., 1990, 29, (9), 1801-1807

Cyclohexane and n-heptane reforming were studied on 0.3-0.3% Pt-Re/AI,0,-0.95%

Cl catalyst in the

presence of S. The combined effect of

Re-S

and Pt-Sj (where

Si

is the irreversible form of Pt) that modified the Pt ensemble size and the electronic interactions caused the hydrogenolysis and dehydmyclisation activities to decrease. Due to the added effect of Re-S decreasing the ensemble size, the fewer “available” free Pt crystallites on Pt-Re/AI,O, compared to Pt/AI,O, means the toxicity of reversible S was greater for the bimetallic catalysts.

Y.-H. SUN, S.-Y. CHEN and S.-Y. PENG,

3.

cataf.

G. hi. BICKLE, J. N. BELTRAhUNI and D. D. DO, hd.

XPS Studies of Pt-Sn Naphtha Reforming

Catalysts

Y

.-x.

LI, J. hi. STENCEL and B. H. DAVIS, Appl. Catal.,

X P S studies of Pt-Sn catalysts with porous and non-

porous AI,O, and SiO, gel surface areas of 250 m’/g and 110 mz/g, and 700 mz/gr respectively, were performed. Both Pt(0) and Sn(0) were observed in the reduced samples. Sn(O), and alloy formation, occurs when Pt and Sn are added as a complex dissolved in acetone. The ratio of Pt(0) to Sn(0) varies, at constant Pt loading, with the total amount of Sn added in the preparation. This Pt:Sn ratio varies from about 0.4 to about 6 for the catalysts studied.

1990, 64, (1-2), 71-81

(9)

Molecular

Die

Catalysis:

Hexane

Aromatization over PtlKL

s. J. TAUSTER and J. J. STEGER, J . Cazal., 1990, 125,

Studies of n-hexane aromatisation over 0.6-0.8% Pt/KL, prepared by exchanging zeolite L powder with Pt(NH,),Cl, solution at room temperature for 20 h, and l%Pt/SiO, catalysts were performed at 510°C, 100 psig pressure, with a H,/hexane mole ratio of 6. Pt/KL catalysts showed a much greater selectivity for hexane aromatisation than Pt/SiO, catalysts and a strong preference for cracking the terminal C-C bond as opposed to interior bonds.

Preparation of Platinum Cluster Catalyst

Supported on Porous Chelate

Resin- Metal

Complexes for Hydrogenation of

Olefin and Diene

Chem. Lett. Jpn., 1990, (S), 819-822

Catalysts of

Pt

clusters/chelate resin-metal complexes of Na(I), Mg(II), and AI(II1) were prepared by reduction of

F’t

ions immobilised on the high porosity sup- ports. The catalytic activity of the supported clusters increased in the order: Na(I)<Mg(II)<Al(III), which is consistent with increase in surface area of the resin. (2), 387-389

N. TOSHIMA, T. TERANISHI, H. ASANUMA and Y . SAITO,

Selective Acetylene Hydrogenation in

Mixtures with Ethylene

in

the Presence of

a

Palladium Catalyst

Neftekhimiya, 1990, 30, (4), 453-457

Studies of hydrogenation of C, H

,

-C, H, mixture on

Pdly-Al,O, catalyst performed at 311-373 K in a wide range of reagents concentrations showed the formation of C,H, from the intermediate compound systems ZH,-C,H, (where Z are new active centres of the catalyst) which proceeds in two paralled routes. It is shown that in the case of C,H,-C,H, interaction, the mechanism of ethylene and acetylene with H, is the same as that during hydrogenation of in- dividual hydrocarbons.

I. M. ZHVANETSKY and A. S. BERENBLYUM,

The Effect of Bismuth

on

the Selective

Oxidation of Lactose on Supported

Palladium Catalysts

Carbohydrate Res., 1990, 204, 121-129

The selective oxidation of lactose by 0, has been studied in a batch reactor containing an aqueous slurry of 0.5 kmol/m’ and 1.0 kg/m’ of Pd/C promoted by Bi. This resulted in 100% selectivity to Na lactobionate up to conversions of 95% in the pH 7-10 range and at UD to 333K. A maximum initial reaction- H. E. J. HENDRIKS, B. F. M. KUSTER and G. B. MARIN,

-

Kinetics

of

Liquid-Phase Hydrogenation

Catalyst

rate of 0.47 mollkg s occurred at molar Bi:Pd of

similar selectivities.

of

cimamaldehyde

Over a

pt-snmylon

0.5-0.67. Other aldoses could be oxidised with

E. TRONCONI, C. CRISAFULLI, S. GALVAGNO, A. WNATO, G . NERI and R . PIETROPAOLO, Ind. Eng.

Chem. Res., 1990, 29, (9), 1766-1770

The kinetics of liquid-phase hydrogention of cinnamyl alcohol and cinnamaldehyde over Pt/nylon and Sn-Pt/nylon catalysts were studied. The kinetics of cinnamaldehyde hydrogenation over Sn-Pt/nylon at 1O-6O0C were interpreted on the basis of a two-site model, where B sites, associated with Sn, were involved in hydrogenation of cinnamaldehyde and hydrocinnamaldehyde, whereas A sites, associated with Pt, catalysed cinnamyl alcohol hydrogenations. The results show strong adsorption of cinnamyl alcohol on Pt sites, which also explains the apparent negative activation energies of some rate constants.

Carbon

Monoxide Restructuring of

Palladium Crystallite Surfaces

Cutal., 1990, 124, (2), 488-502

Six Pd/Al, 0 catalysts, with dispersions ranging from 3 to 86% were studied during repeated cycles of exposure to CO at 25OC and reduction at 300OC. CO cycling lowers the dispersion of all the samples by 20 to 50%. The loss of surface sites was higher on the small crystallites. The adsorption capacity recovered with oxidation at 55OoC and reduction at 300OC. The H solubility in the bulk of the Pd crystallites was not affected by CO cycling. Surface restructuring may be used to enhance the catalytic activity of Pd. R. F. HICKS, H. QI, A. B. KOOH and L. B. FISCHEL,

7. Activity and Selectivity of 1-Hexene Con-

version

on

SAPO-11 and PdSAPO-11

S. J. CHOUNG and J. B. BUTT, Appl. catal., 1990, 64,

The activity and selectivity patterns for 1-hexene reactions were compared at 15O-45O0C for four different kinds of acidic zeolites (H-mordenite, HZSM-5, SAPO-11 and Pd/SAPO-I 1) with different acid properties and geometric structure. The Pd/SAPO-11 catalyst gave enhanced double bond shift (DBS) selectivity and less cracking at higher temperatures in comparison to unloaded SAPO-11. There was a strong correlation between the shift from DBS to cracking with total acidity.

(1-2), 173-189

An

Infrared Study of the Hydrogenation

of Carbon Monoxide and Carbon Dioxide

at

High Pressure over Pd/La,O,

n. D. BURKETT, s. D. WORLEY and c . n. DAI, Chem.

A new high-pressure IR cell reactor has been used to study the reactions of CO and CO, with H, over Pd/La,O, films at a pressure of 8300 TOR. The activation energy for the CO, hydrogenation (25.1 kcal/mol) which produces MeOH is higher than that reported elsewhere for the analogous CO hydrogenation reaction. The CO, reaction may proceed through hydrogenation of adsorbed CO, rather than by direct hydrogenation of CO, over Pd/La 0 j .

Phys. Lett., 1990, 173, (5,6), 430-434

(10)

Structure-Sensitivity of the Deactivation

of

Pd/SiO

for

Methylcyclopropane

Hydrogenolysis by CO

J. B. BUTT and

c.

L. M. JOYAL,

3.

Chem. SOC., Faraday

Trans., 1990, 86, (16), 2911-2917

Pd/SiO, catalysts with 5-8Ooh metal exposed have been characterised for reactivity for methylcyclopropane hydrogenolysis as a function of CO poisoning. The CO surface coverage and metal crystallite size are important in the deactivation behaviour of the catalyst. &treatment conditions help to determine reaction and deactivation structure sensitivity patterns. As CO coverage increases a monotonic decrease in activity occurs for large Pd particles, while catalysts with >40% metal exposed have a near-step drop in activity between 20-30% coverage.

Effects of Promoters of PalladiumlSilica

Catalysts

for

the Synthesis of Methanol

H. s. HAHM and w. Y. LEE, Appl. Coral., 1990,65, (l),

Methanol synthesis from syngas on promoted Pd/SiO, catalysts was carried out at 1-20 atm (H:CO=2) and 230-310OC. The effects of Ca, K or La promoters on the activity and selectivity for methanol formation were studied. The highest methanol activity was achieved with O . h t . % Ca pro- moted Pd/SiO, catalysts and was about four times higher than that of non-promoted catalyst. 1-9

Effects of Cerium Addition on the CO-NO

Reaction

Kinetics

over

Alumina-

Supported Rhodium Catalysts

s. H. OH,

3.

Caul., 1990, 124, (2), 477-487 Laboratory reactor studies showed that the addition of

Ce

to a low-loaded Rh/Al,O, catalyst resulted in changes in CO-NO reaction kinetics, mainly suppres- sion of N, 0 formation, decreased apparent activation energy, and a shift to a positive-order dependence of the rate on NO partial pressure. The Ce-induced modification of the kinetics leads to increases in the NO reduction activity at low temperatures.

Effect of Potassium on the Formation of

Isocyanate Species

in the

NO

+

CO

Reac-

tion on Rhodium Catalyst

8. NOVAK and F. SOLYMOSI,

3.

catal., 1990, 125, (I), 112-122

Adsorption and IR spectroscopic studies of the effect of K on the formation of isocyanate species in the NO

+

CO reaction on supported Rh catalysts showed that the addition of K to 5% Rh/Al,O, significantly decreased the uptake of H,, CO and NO at 300 K. Preadsorbed K caused a significant increase in the formation of the NCO complex, with the maximum intensity obtained for a sample containing 2.5% K. The same effect was observed on Rh/SiO, catalyst where two NCO species were identified (2180cm-

'

for Rh-NCO and 2310cm- for Si-NCO).

CO Adsorption on Rhodium(1) and on

Metallic Rhodium Supported on Titanium

Dioxide

ESPIN~S and L. A. ORO,

3.

Mol. catal., 1 9 0 , 62, (2),

The interaction between a cationic organometallic Rh(1) compound and TiO, in acetone leads to Rh(I)/TiO,. The reduction with H, at atmospheric pressure and ambient temperature yields a supported metallic Rh catalyst which is active in 1-hexene hydrogenation. The precursor and catalyst have been

characterised, and the predominant species is dicar- bony1 on both. Dissociative CO adsorption is discussed.

J. HERRERO, C. BLANCO, A. R. GONZLEZ-ELIPE, J. P.

171-177

Selectivity Changes

in

the Ring-Opening

Reaction of Methylcyclopentane

over

Rhodium Catalysts Caused by the Addi-

tion of Silver and Metal-Support In-

teractions

R. J. FENOGLIO, G. M. -2 and D. E. RESASCO, Appl. Catal., 1990, 63, (2), 319-332

The hydrogenolysis of methylcyclopentane (MCP) was studied over Rh-Ag/TiO, catalysts after various reduction/oxidation treatments. The addition of Ag resulted in a decrease in activity, accompanied by an increase in the selectivity toward n-hexane (n-Hx). This increase in selectivity was enhanced when Ag and Rh are impregnated simultaneously and when the catalysts are reduced at 773 K. The selectivity changes can be interpreted in terms of a shift in the ring-opening mechanism. This shift is caused by a blockage of large ensembles required to constitute the multi-site complexes. This blockage would be more effective when Ag and TiO, species are simultaneously present on the Rh surface.

Carbon

Dioxide

Hydrogenation on

Rhodium Supported on Transition Metal

Oxides. Effect

of Reduction Temperature

on Product Distribution

and M. GRAzIANI, Appl. caral., 1990, 65, (I),

Studies of the effects of metal reduction conditions during CO hydrogenation on Rh/TiO, and Rh/Nb,O, catalysts showed the presence of C,-C, hydrocarbons which followed Anderson-Schulz- Flory statistics. For Rh/TiO,, the role of CO as an intermediate in CO, hydrogenation was clearly evident. In both catalysts, the formation of the SMSI state (strong metal-support interaction) during high temperature reduction greatly affected catalytic activities and selectivities. The differences in the general behaviour of the two oxides as far as the reversibility of the SMSI in the reaction conditions was concerned was ascribed to thermodynamic and/or kinetic constraints in the formation of SMSI during high temperature reduction.

A. TROVARELLI, C. MUSTAZZA, G. DOLCETTI, 1. KAXPAR

129-142

(11)

Synthesis of Hydrocarbons and Alcohols

from CO and H 2 over Co-Rh Catalysts

A. L. LAPIDUS, Z. NOVAK, M. M. SAVEL'EV, B. LYUKKE, T. ZIMMERMAN, S. D. PIROZHKOV, KH. E. MANEK, S. D. SOMINSKII and L. F. RAR, Zzv. Akad. Nauk SSSR, Ser. Khim., 1990, (8), 1707-1709

Studies of synthesis of hydrocarbons and alcohols from CO and H2 (CO:H,= 1:2) over Co catalysts promoted by addition of Rh and Cu were performed at 250-3OO0C and pressure of 0.1-6.0 MPa. The results show that 4.5% Co-0.1% Rh-5:10% Cu/TiO, catalysts are highly active in the above synthesis and have much higher selectivity in regards to the formed alcohols as compared to the traditional Co-catalysts.

Immobilization of Rhodium Complexes

with Chiral Cationic Water Soluble

Ligands on Nafion-H and Other Strongly

Acidic Cation Exchange Resins

Chem., 1990, 397, (l), 109-117

Rhodium complexes of the chiral cationic water solubleligands,

[(S,

S)-2,4-bis[-bis(-p-N,N-dimethyl- ammoniumpheny1)phosphinolpentanel'

+,

etc., were immobilised on cation exchange resins. All these supported complexes catalyse the asymmetric hydrogenation of dehydroaminoacid derivatives with no detectable loss of Rh into the substrate phase. Rates and enantioselectivities depend on the ligand and the nature of the exchange resin.

IR Study of CO Adsorption and Its In-

teraction with Oxygen over Ir/A1203

Catalyst

H.-Y. LOU,

Y.-z.

CHU,

c.4.

xu

and Y.-s. ZHOU,

3.

Catal., 1990, 11, (4), 284-289

An IR study of the behaviour of CO adsorption and its interaction with 0 over Ir/Al

,

0, catalyst showed that CO adsorption on Ir/Al,O, with high Ir loading was an activation process, and the intensity of the adsorbed CO band increased with the increase in adsorption temperature from ambient to 300OC. The amount of adsorbed CO at 15OOC was approximately one half that of the maximum. The migration of ad-

sorbed CO and 0 was increased by increasing the temperature.

I. T6TH, B. E. HANSON and M. E. DAVIS,

3.

Organomel.

Zeolite A-Supported Ru Catalysts

J. C. S. WU, J. G. GOODWIN and M. DAVIS,

3.

catal.,

1990, 125, (2), 488-500

A number of zeolite A-supported Ru catalysts were prepared either by addition of Ru precursor to the zeolite A synthesis gel [ZSI with resulting metal being dispersed intrazeoliticdy, although not uniformly, or by surface deposition of Ru on zeolite A with metal particles primarily on the external surfaces of the zeolite crystallites. With the exception of the strong molecular sieving effect on the reaction of cyclopropane found for RuNaNZSI, the most important effect on the catalysis was Ru particle size.

Surface Structure and Catalysis for

CO

Hydrogenation of the Supported Ru

Species Derived from the Ru (CO)

12

In-

organic Oxides

K. ASAKURA and Y . IWASAWA,

3.

Chem. soc., Faraday Trans., 1990, 86, (14), 2657-2662

Supported Ru cluster particles were prepared by the surface reaction of Ru,(CO),, with inorganic oxides followed by H, reduction at 723 K. On

V,O,

the cluster was converted to three-atomic-layer Ru metal particles, while one-atomic-layer [Rul, clusters were formed on SiO, (n=12) and TiO, (n=6). Clusters [Ru,(OZ),l (Z=Al or Mg) with Ru-0 surface bonds were formed on Al,O, (n=6), K-doped Al,O, (n=6) and MgO (n=3). CH, was predominantly formed on [Rul ,,/SiO, . The bRu atom clusters with Ru-Ru distances of 0.262-0.265 nm had the highest selectivity for C, -C, hydrocarbon formation. Metallic [Ru16 clusters on TiO, had higher activity than [Ru,(OAl),I clusters bonded to the surface through 0 atoms. The smallest surface-bound clusters on MgO produced mainly CH, and CO,.

HOMOGENEOUS CATALYSIS

A

New Platinum-Based Catalyst System

for Olefm Asymmetric Homogeneous

Hydroformylation

Organomet. Chem., 1990, 397, (l), 119-125 A number of Pt(I1) diphosphino complexes in com- bination with SnCI, are known to be active in olefm hydroformylation. It is now reported that the complex [Pt(C,H,)(( +) -DIOP)I interacts with [ptCl,((+)-DIOP)l to give catalysts active in the hydroformylation of styrene and 1-hexene. The activities of the systems depend upon the molar ratio of the two Pt complexes and the nature of the substrate. The systems display good chemioselectivity and in- duce asymmetry in the branched aldehydes formed. 2-Phenylpropanal can be isolated in -27% optical purity from styrene hydroformylation.

Evidence

for

a

Bis(aUrylidene)

silacyclopropane Intermediate

in

the

Platinum-Mediated Formation

of

a

Silacyclobutene

MCPHAIL,

3.

Am. Chem. Soc., 1990, 112, (20),

The treatment of Ph,Si(CECCMe,), with a cationic Pt-H reagent resulted in the formation of a

4-alkylidene-I-silacyclobutenyl ring system. Acetic acid cleaves at Pt-C bond to yield alkenylsilane products, showing the intermediate formation of a Pt, Si- palkenylidene complex. ROH reagents react with a proposed bis(alkylidene)silacyclopropane intermediate to initiate ring opening and to form q 3 -

butadienyl complexes (where R=H, Me, Et or Ph). The R = H complex ion structure was confirmed.

S. PAGANELLI, U. MAlTEOLI and A. SCRWANTI,

3.

A. C. DEMA, C. M. LUKEHART, A. T. MCPHAIL and D. R.

7229-7233