Table Of ContentStudies inSurface Scienceand Catalysis
AdvisoryEditors:B.Delmon andJ.T. Yates
Vol. 44
SUCCESSFUL DESIGN
OF CATALYSTS
Future Requirements and
Development
Proceedings oftheWorldwide Catalysis Seminars, July, 1988,
onthe Occasion ofthe 30thAnniversaryofthe
Catalysis SocietyofJapan
Editor
T.lnui
DepartmentofHydrocarbonChemistry, Faculty ofEngineering,
Kyoto University, Sskyo-ku, Kyoto 606, Japan
ELSEVIER Amsterdam- Oxford- NewYork- Tokyo 1989
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IX
PREFACE
Catalyst research during the last decade
In the last decade, in the wakeof the oil crisi~ rapid advances have been
made in various aspects of synthetic chemistry concerned with one-carbon
compounds, so-called C chemistry, especially in the u.s.A., the EEC and Japan.
1
"c,
The name chemistry" was preferred to "petrochemistry", or "oil-based
chemistry", as the latter could be called C chemistry since ethylene is the
2
representative starting compound. In the initial stages of C, chemistry
researc~ it was considered a coal-based chemistry, since coal resources are
ten times as great as oil resources. Accordingly, syngas and methanol are
traditionally considered the major starting materials in this field of
chemistry.
The synthesis of various objective compounds from such simple molecules can
only be achieved with the aid of well-designed catalysts and modern instruments
able to precisely analyze surfaces, solid states, and active species. It is
noteworthy that a large number of scientists and engineers from many countries
have concentrated their efforts during recent years on this common objective.
That is why the growing importance of C chemistry has been accompanied by a
1
marked increase in activities concerning the scientific and engineering aspects
of catalytic processeL
New trends in catalyst research
The current economic status of oil and the many technological obstacles to
the industrialization of processes related to C, chemistry, have made research
and development efforts in this field very conservative.
Despite this, it is essential to carryon the search for new petroleum
engineering techniques, to further our knowledge of petrochemistry, and to
pursue syntheses of new energy resources based on both insufficient-use
fractions from petroleum refineries and on alternative raw materials, and this
for two main reasons. In the first place we must ensure the complete use of
invaluable oil, and therefore various types of alkanes have been targeted for
forming valuable high-performance fuels and chemical building blocks such as
BTX. Secondly, we must aim at a more effective use of natural gas. Since the
beginnings of C, chemistry, worldwide natural-gas consumption has roughly
doubled and is now running at an equivalent level to that of oil. Natural gas
is now regarded as the intermediate resource between oil and coal.
x
Natural gas is primarily methane, which is the most chemically stable organic
compound but is inconvenient to transport from the site of production to the
place of commercial use. However, it can be treated, separated, and purified
more easily than coal or even oil.
Thus, C compounds from methane to heavy hydrocarbons, which might be called
n
C chemistry, are becoming the targets of modern catalyst chemistry.
n
Successful design of catalysts to answer future requirements
Although only two large-scale industrialized processes, Monsanto's acetic
acid synthesis process and Mobil's methanol-to-gasoline process, have been
developed, a number of breakthroughs in heterogeneous and homogeneous catalyst
chemistry have been made. The most evident advances have occurred in shape-
selective microporous crystalline catalysts such as pentasil-type zeolites like
ZSM-5 and a variety of other metallosilicates, various kinds of alumino-
phosphates and their family compounds, and recently, the first molecula~ sieve
with pores larger than twelve tetrahedral atoms, VPI-5. Furthermore, even in
conventional zeolites, novel uses are now being developed by combining
compounds of catalyst metals and organometallic compounds. Technologies for
separation and purification using pressure-swing adsorption and membranes have
also been developed and form the basis for well-controlled catalytic reactions.
In addition to progress in material science and instrument engineering, there
have been advances in computer science which have made catalyst design and the
state of reacting molecules visible in three-dimensional graphics.
All of this knowledge must be put to use in the research and development of
the new catalysts and catalytic processes to meet future requirements.
Fruitful results anticipated as a result of direct communications of worldwide
research
The Catalysis Society of Japan (CSJ) marks its 30th anniversary in July this
year, having been founded shortly after the First International Congress on
Catalysis was held in 1956. As one of the events to mark this anniversary, a
Worldwide Catalysis Seminar was held: after the 9th International Congress on
Catalysis in Calgary, Canada, June-July 1988, about 25 Japanese researchers
working on catalysis visited and held seminars in four countries - each seminar
focused on a specific subject, yet a1so covered a wide range of subjects in
catalysis from the fundamental to the industrial stages, and considered how
best to achieve the "Successful Design of Catalysts - Future Requirements and
Development", the actual title of this book.
XI
The seminars were:
U.S.A.-JAPAN CATALYSIS SEMINAR (July 5, 1988 in Philadelphia, PA):
PROGRESS ~ SURFACE ANALYSIS OF CATALYSTS
FRANCE-JAPAN CATALYSIS SEMINAR (July 7, 1988 in Paris):
DESIGN OF COMPOSITE CATALYSTS
ITALY-JAPAN CATALYSIS SEMINAR (July 8, 1988 in Bologna):
ADVANCES ~ ZEOLITIC CATALYSTS
GERMANY-JAPAN CATALYSIS SEMINAR (July 11, 1988 in Frankfurt/M):
ADVANCES ~ INDUSTRIAL CATALYSTS
In principle, two plenary lectures and three invited talks were planned for
scientists from each country in the two-country seminars. I believe that this
kind of opportunity for direct communication and discussion of the common
problems (energy, resources, chemicals) facing human beings represents a
significant and successful way to secure future international cooperation in
the field of catalysis researc~
From the early planning stages, the full support of Dr. Teruo Yasui
(Kuraray Co.), Professor Kozo Tanabe (Hokkaido University) and Mr. K.. Yamauchi
(Kyowa Hakko Co.) has been invaluable. Also Professor Kenji Tamaru (Tokyo
Science University), Professor Gary L. Haller (Yale University, U.S.A.),
Dr. G. Martino (FPI, France), Dr. Orfeo Forani (Snamprogetti, Italy) and
D~ Wolfgang H~lderich (BAS~ ~~~) expressed their warm approval of the
plan and its spirit, and have since cooperated fully in its realization.
Professor Haller agreed to become chairman at the U.S.A.-Japan seminar, and
the team became completed when Dr. Pierre Ch. Gravelle, Professor Ferrucio
Trifiroo and Professor D. Behrens joined us as chairmen for the France-Japan,
Italy-Japan and Germany-Japan seminars, respectively.
The anticipated success of such a never-before-tried project will have been
due to the efforts of all of those mentioned above and the contributors from
each country. I would like to express mysincere and hearty thanks to all of
them.
Finally, I would a~so like to express my thanks to Associate Professor Akira
Miyamoto and secretaries Mrs. Mari Hirai and Mrs. Mayumi Ogino of my laboratory
for their dedicated assistance in managing the tremendous amount of
correspondenC:e.
TOMOYUKI INUI
T.Inui (Editor),SuccessfulDesign ofCatalysts 3
©1988ElsevierSciencePublishersB.V.,Amsterdam- PrintedinThe Netherlands
SURFACE STATE AND CATALYTIC PROPERTIES OFNi-P AND Pd-P FILMS PREPARED BY RF
SPUTTERING METHOD
TOSHINOBU IMANAKA
Department of Chemical Engineering, Faculty of Engineering Science, Osaka
University, Toyonaka, Osaka 560, Japan
ABSTRACT
Ni-P and Pd-P thin films with various P concentration were prepared by using
the RF sputtering method. In the Ni-P films, phosphorus below 25 atom% of P
donated electrons to nickel, while phosphorus above 25 atom% of P accepted
electrons from nickel. With the Pd-P films, phosphorus accepted electrons from
palladium. The selectivity for the partial hydrogenation of diolefins and
acetylene altered with the electron density of metal. The low electron density
of metal was favorable for the partial hydrogenation. The high selectivity
(>99%) was obtained in the hydrogenation of diolefins and acetylene over the
Pd-P films.
INTRODUCTION
Metal phosphide is usually prepared by a reaction of aqueous solution of
metal salts with sodium hypophosphite. For example, nickel phosphide is
prepared by the reduction of nickel salts using NaH in water or ethyl
2P02
alcohol (ref. 1). The phosphorus concentration in such nickel phosphide was in
the range of 40-48 atom%of P depending on the sort of nickel salts. A
sputtering technique is often used to prepare thin films. Especially, a
reactive sputtering method is excellent to prepare alloy thin films. Namely, a
composition and a thickness of films are easily controlled by varying sputtering
conditions. Using the RF sputtering method, Ni-(B, P)(ref. 2) and Pd-(B, P)
(ref. 3) thin film alloys with various B or P concentration have been easily
prepared by changing the sputtering conditions because both metal and B or P
atom is simultaneously deposited on the glass substrate from gas phase. The
individual characterizations of the Ni-(B, P)(ref. 2) and the Pd-(B, P)(ref. 3)
films have been preViously reported elsewhere. In this investigation, Ni, Pd,
and their phosphides have been mainly compared in terms of their structure,
surface state, and catalytic properties which are evaluated by X-ray diffraction
(XRD), X-ray photoelectron spectroscopy (XPS) and the hydrogenation of diolefins
and acetylene.
4
EXPERIMENTAL
The metal phosphide films have been prepared by using the RF sputtering
technique (ref. 4). The target was pure Ni, Pd plates. Phosphorus source was
PH diluted with H (5.37 vol%). Asputtering atmosphere was a mixed gas of Ar
3 2
(99.9995%) at a pressure of 0.05 Torr (1 Torr=133.3 Pa) and PH The glow
3+H2•
discharge was carried out in various PH partial pressures.
3
The structure and surface state of metal phosphide films were measured by
Shimazu VD-l X-ray diffractometer with CuKa radiation of 30 kV, 20 rnA and
Shimazu ESCA-7S0 X-ray photoelectron spectrometer with Mg Ka radiation of 8 kV,
30 rnA.
The hydrogenation of diolefins and acetylene was carried out using a
conventional closed circulation system at appropriate temperature (Ni-P: 373 K,
Pd-P:273 K). The ratio of H was 6 and total pressure in the system was
2/olefin
140 Torr. The products obtained by the hydrogenation reaction were analyzed
using a gas chromatgraph with a thermal conductivity detector. The Pd-P films
-3
were heated at 573 Kfor 1 h in a vacuum (10 Torr). The effect of heat
treatment was also examined on the selectivity for the partial hydrogenation of
diolefins and acetylene.
RESULTS AND DISCUSSION
Surface composition
The surface composition of the metal phosphide films was changed with the
partial pressure of PH in the discharge gas. The composition was evaluated
3+H2
on the basis of the XPS peak area ratios of the P2p level to the core levels of
each metal (Ni2p3/2 or Pd3d). The P concentration in the metal phosphide films
increased with increasing PH partial pressure. Ni and Pd films
3+H2 60P40 7SP25
were prepared under the atmosphere of the mixed gas of Ar 0.05 Torr and PH
3+H2
0.20 Torr.
Structure of film
The XRD measurement was carried out for the alloy films deposited with the
efficient thickness (above 200 nm). Figure 1 presents XRD patterns of the
crystalline nickel plate used as the target, the nickel film prepared by the
glow discharge under the condition of Ar gas atmosphere only, and the nickel
phosphide film under the Ar+PH gas mixture. Three peaks due to Miller
3+H2
indices (Ill), (200), and (220) of Ni fcc structure appeared at 44.5, 51.8, and
76.5 degrees in the nickel plate and the Ni film obtained by sputtering in Ar
atmosphere. However, there was no peak in the Ni-P films. It is evident that
the Ni-P films prepared by the addition of P to Ni become an amorphous state,
while the Ni film crystallizes.
Figure 2 represents XRD patterns of the Pd-P films with various surface
5
CuKcx
Ni(200)
51.8
Ni(111)
44.5
Ni(220)
76.5
Ul
0.
o
<,
;:..,
.j..I
.r!
Ul
C
Q)
.j..I
C
H
c
80 70 60 50 40
26/deg
Fig. 1. X-ray diffraction patterns of the Ni-P films.
a)Ni plate" b)Ni film, c)Ni film.
69P3l
composition. Two peaks due to Miller indices (Ill) and (200) of Pd fcc
structure appeared at 40.3 and 46.5 degrees in the pure Pd film. Below 25 atom%
of P in the Pd-P films, only one peak appeared near Pd(lll) peak (Fig. 2-b,c).
The peak position shifted to the lower angle of 26 and the peak became smaller
6
50 45 40 35
28/deg
Fig. 2. X-ray diffraction patterns of the Pd-P films.
,
aa))P10d018o• bb)1)P0d0807,Pc1)25,00c),Pdd7)570P33•, d)Pd75P25. Scale of peak intensity (X cps):
and broader with increasing P concentration. Above 25 atom% of P, the Pd-P
films became an amorphous state (Fig. 2-d).
Surface state
All the binding energies of XP spectra were corrected by a contaminant carbon
(C1s=285.0 eV). XP spectra of the P2p and the NiZp3/2 levels for the Ni-P
films are shown in Fig. 3. In the P2p levels, phosphorus interacting with
nickel (130.0 eV) increased and phosphorus oxide (PZOS' 133.9 eV) decreased with
increasing P concentration. In the Ni2p3/2 levels, the main peak due to nickel
metal appeared at 853.4 eV accompanying the satellite peaks in a region of
higher binding energies.
The Ni2p3/2 spectra were separated into five or six Gaussian peaks. The
examples of peak separations for the Ni2p3/2 spectra of the Ni film is
38P62
shown in Fig. 4. Peaks 1 and 2 were assigned to the main peaks and the peak 2
was employed to correct the asymmetry of the main peak. Peaks 3, 4, and 5 were
7
P2p Nj2p~
J l
140 130 860 850
Binding energy/ev
Fig. 3. X-ray photoelectron spectra of PZp and NiZp3/Z levels for the Ni-P
films.
a)Ni b)Ni c)Ni d)Ni e)Ni f)Ni
lOO' 93P7, 74PZ6' 60P40, 39P6l, 19P8l"
assigned to the satellite peaks. The peak 5 is attributable to a satellite peak
rather than to a nickel oxide peak, because it appears at 857.8 eV.
The satellite intensity was employed in order to estimate quantitatively the
electron density of nickel. The satellite intensity (I was calculated using
sat)
the formula appeared in the earlier paper (ref. 5)
In/(n + n )
sat sat, sat main
where n and n are the areas of the satellite peaks (peaks 3, 4, and 5)
sat main
and the main peaks (peaks 1 and Z), respectively. The dependence of the
satellite intensity calculated by using this formula on the P concentration in
the Ni-P films is shown in Fig. 5.
