Catalytic Materials: Relationship Between Structure and Reactivity

454 Pages·1984·7.519 MB·English

by  Thaddeus E. Whyte, Jr., Ralph A. Dalla Betta, Eric G. Derouane, and R. T. K. Baker (Eds.)

Catalytic Materials: Relationship
1 Between Structure and Reactivity
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
ACS SYMPOSIUM SERIES 248
Catalytic Materials: Relationship
Between Structure and Reactivity
Thaddeus E. Whyte, Jr., EDITOR
Catalytica Associates, Inc.
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0
0
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8.f Ralph A. Dalla Betta, EDITOR
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0 Catalytica Associates, Inc.
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bk- Eric G. Derouane, EDITOR
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10 Mobil Technical Center
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doi: R. T. K. Baker, EDITOR
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9 Exxon Research & Engineering Co.
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5,
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e: Based on the 1983 State-of-the-Art Symposium sponsored by
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atio San Francisco, California,
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American Chemical Society, Washington, D.C. 1984
In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
Library of Congress Cataloging in Publication Data
Catalytic materials.
(ACS symposium series, ISSN 0097-6156; 248)
"Based on the 1983 state-of-the-art symposium
sponsored by the Division of Industrial and
Engineering Chemistry, San Francisco, California, June
13-16, 1983."
1
0 Includes bibliographies and indexes.
0
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8.f 1. Catalysts—Congresses.
24 I. Whyte, Thaddeus Ε., 1937- . II. American
4-0 Chemical Society. Division of Industrial and
8 Engineering. III. Series.
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k- QD505.C387 1984 541.3'95 84-2776
b ISBN 0-8412-0831-X
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on Copyright © 1984
cati American Chemical Society
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
ACS Symposium Series
M. Joan Comstock, Series Editor
Advisory Board
Robert Baker Geoffrey D. Parfitt
1 U.S. Geological Survey Carnegie-Mellon University
0
0
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8.f Martin L. Gorbaty Theodore Provder
24 Exxon Research and Engineering Co. Glidden Coatings and Resins
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4-
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9 Herbert D. Kaesz James C. Randall
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k- University of California— Los Angeles Phillips Petroleum Company
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10 Rudolph J. Marcus Charles N. Satterfield
10. Office of Naval Research Massachusetts Institute of Technology
oi:
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4 | Marvin Margoshes Dennis Schuetzle
98 Technicon Instruments Corporation Ford Motor Company
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5, Research Laboratory
pril Donald E. Moreland
A USDA, Agricultural Research Service Davis L. Temple, Jr.
e: Mead Johnson
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D W. H. Norton
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o J. T. Baker Chemical Company Charles S. Tuesday
cati General Motors Research Laboratory
ubli Robert Ory
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USDA, Southern Regional C. Grant Willson
Research Center IBM Research Department
In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
FOREWORD
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w0 The ACS SYMPOSIUM SERIES was founded in 1974 to provide
8.f a medium for publishing symposia quickly in book form. The
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0 format of the Series parallels that of the continuing ADVANCES
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98 IN CHEMISTRY SERIES except that in order to save time the
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k- papers are not typeset but are reproduced as they are sub­
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oi: of the Series Advisory Board and are selected to maintain the
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8 previously published papers are not accepted. Both reviews
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
PREFACE
THE CHARACTERIZATION OF CATALYST STRUCTURES has undergone revolu­
tionary developments in recent years. Powerful novel techniques and instru­
mentation are now used to analyze catalyst structure before, during, and
after use. Many of these advances are responsible for placing the field of
catalysis on an improved scientific basis. These developments have resulted
1
0 in a better understanding of catalytic phenomena, and therefore improve­
0
8.pr ments in commercial catalysts and the discovery of new systems. The
4
2 application of advanced electronics and computer analysis has optimized
0
84- many of these analytical tools. These developments are especially evident in
9
k-1 spectroscopy, zeolite structure elucidation, and microscopy; several other
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1/ techniques have also been developed. Thus, the difficult goal of unraveling
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10 the relationships between the structure and reactivity of catalytic materials is
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1 finally within reach.
doi: Spectroscopic developments have accelerated advances in the field of
4 | catalysis. This volume analyzes the impact on catalyst structure and reac­
8
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1 tivity of EXAFS, SIMS, Mossbauer, magic-angle spinning N MR
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pril (MASNMR), and electron-energy-loss vibrational spectroscopy. Many of
A these techniques are combined with other analytical tools such as thermal
ate: decomposition and temperature-programmed reactions.
D
n The major effect of new advanced techniques on catalyst structure is
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ati found in zeolite catalysis. N MR techniques, especially MASNMR, have
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bli helped to explain aluminum distribution in zeolites and to increase our
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MASNMR, combined with TEM, STEM, XPS, and diagnostic catalytic
reaction probes, has advanced our knowledge of the critical relationship
between the structure and reactivity patterns of zeolites in the chemical fuels
industry. Throughout the symposium upon which this book is based, many
correlations were evident between theoretical quantum mechanical calcula­
tions and the structures elucidated by these techniques.
Improvements in the resolution and versatility of microscopic tech­
niques have come about rapidly. TEM, STEM, and high-resolution electron
microscopy have helped the catalytic chemist to analyze the effects of metal-
support interactions and particle-size effects—developments that will proba­
bly lead to improvements in commercial technologies. Several novel analyti­
cal methods, arising from very clever experimentation, were discussed at the
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
symposium. These included photoacoustic spectroscopy, inelastic tunneling
spectroscopy, and Rutherford back-scattering spectrometry.
Thus the catalytic scientist is now very close to achieving the goal of
establishing clear relationships between the structure and reactivity of cata­
lytic materials. The next breakthrough will be the deliberate design of
specific structures to improve the activity and selectivity of catalytic mate­
rials.
THADDEUS Ε. WHYTE, JR. ERIC G. DEROUANE
Catalytica Associates, Inc. Mobil Technical Center
Mountain View, California Princeton, New Jersey
RALPH A. DALLA BETTA R. T. K. BAKER
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0 Catalytica Associates, Inc. Exxon Research & Engineering Co.
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8.pr Mountain View, California Clinton, New Jersey
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84- January 1984
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In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
1
Thermal Decomposition of Iron Pentacarbonyl
on Titania
Genesis of Fe/TiO Catalysts
2
J. PHILLIPS
Department of Chemical Engineering, The Pennsylvania State University, University Park,
PA 16802
J. A. DUMESIC
Department of Chemical Engineering, University of Wisconsin-Madison, Madison, WI 53706
1
0
0 Mössbauer spectroscopy and volumetric gas phase
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8.c analysis were used to study the nature of surface
24 species formed during the decomposition of Fe(CO)
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4- on cleaned titania powder. The titania was pretreated
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9 so as to produce samples with different hydroxyl
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k- group and Ti3+ concentrations. It was found that
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1/ the presence of Ti3+ did not affect the nature of
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10 the iron species which formed. The extent of decom­
10. position was found to be proportional to the
oi: hydroxyl group density. On all surfaces, low
d
4 | temperature (383 K) decomposition led to the forma­
8 tion of an Fe2+ species and an Fe° species (possibly
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5, 1 Fe(CO)2), both of which were probably associated
April wveirthy hsuigrhfalyc e dhisypderrosxeydl ognro tuhpes . suTpphoerste. spHecigiehs t wemerpee ra­
e: ture decomposition (673 K) led to nearly complete
Dat conversion of the metal to the Fe2+ species. A very
on small fraction of the iron apparently sintered to
ati form metallic iron particles during the high tempera­
c
bli ture treatment. Prolonged reduction of these sample
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P in hydrogen at ca. 700 Κ led to the formation of

small metallic iron particles (less than 9 nm in
size).
One area of current interest in heterogeneous catalysis is under­
standing the effects of metal-support interactions on the catalytic
properties of Group VIII metals. Recently it has been found that
the interaction between T1O2 supports and metal particles is
particularly strong. This interaction has been denoted as a
"strong metal-support interaction"(SMSI). Indeed, Tauster et al.
(1) showed that following a high temperature reduction (ca. 770 K)
in hydrogen, noble metals (e.g., Ru, Rh, Pd, Os, Ir, Pt) supported
on T1O2 ^0n ot ac*sorb hydrogen or carbon monoxide. On other
refractory supports (e.g., Si0, AI2O3), and even on T1O2 following
2
0097-6156/84/0248-0003$06.00/0
© 1984 American Chemical Society
In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
4 CATALYTIC MATERIALS
low temperature reduction in hydrogen, particles of these metals
adsorb hydrogen and carbon monoxide readily. Another area of
research in catalysis is the use of metal carbonyl clusters for
the preparation of supported metal catalysts (e.g., 2,3). These
clusters offer the potential opportunity for preparing catalysts
with novel properties (e.g., having particularly high dispersions).
Of importance in this respect is the interaction of the support
with the various metal species formed during decarbonylation of
the clusters. Such species include metal subcarbonyl species,
metal cations and metal crystallites.
The present paper focuses on the interactions between iron
and titania for samples prepared via the thermal decomposition of
iron pentacarbonyl. (The results of ammonia synthesis studies
over these samples have been reported elsewhere (4).) Since it
has been reported that standard impregnation techniques cannot be
01 used to prepare highly dispersed iron on titania (4), the use of
0
h iron carbonyl decomposition provides a potentially important cata
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8. lyst preparation route. Studies of the decomposition process as
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02 a function of temperature are pertinent to the genesis of such
84- Fe/Ti02 catalysts. For example, these studies are necessary to
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1 determine the state and dispersion of iron after the various
k-
b activation or pretreatment steps. Moreover, such studies are
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2 required to understand the catalytic and adsorptive properties of
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0.1 these materials after partial decomposition, complete decarbony
doi: 1 wlaast iouns edo r ihny dtrhoisg esnt urdeyd utcot imoonn.i tIonr sthhoer ts,t Matöes sobfa uierron s pienc tcraotsacloypsyt s
4 | prepared by the decomposition of iron carbonyl. Complementary
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9 information about the amount of carbon monoxide associated with
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5, iron was provided by volumetric measurements.
pril
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on Ti02 Preparation
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u Ti0 powder obtained from the Cabot corporation (Cab-O-Ti) was
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used in these investigations. This material has a surface area
of between 50 and 70 m2/g and is reportedly 99.9% pure Ti0. This
2
material was 'cleaned* using a method similar to that of Munuera
et al. (5) and Cornaz et al. (6). This method reportedly removes
the organic contaminants from titania. The possible presence of
organic contaminants led Gebhardt and Herrington (7) to raise
questions regarding the accuracy of early studies of titania
surface structure. In brief, the titania was cleaned using the
following sequence of steps : (i) heating the fresh powder in a
pyrex vessel to 670 Κ (or higher) in flowing oxygen, (ii) pumping
on the powder (10~2pa) for one hour while heating the sample to
570 K, (iii) boiling the partially dehydroxylated Ti0 in deionized
2
water for ten minutes, and (iv) drying the Ti0 (12 hours) at
2
380 K. This procedure produces organic free, completely hydroxy-
In Catalytic Materials: Relationship Between Structure and Reactivity; Whyte, T., el al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1984.