Table Of ContentStudies in Surface Science and Catalysis
Advisory Editors: 6. Delmon and J.T. Yates
Vol. 53
CATALYSTS IN PETROLEUM
REFINING 1989
Proceedings of the Conference on Catalysts in Petroleum Refining,
Kuwait, March 5-8,1989
Sponsored by Kuwait Institute for Scientific Research, Kuwait Foundation for
the Advancement of Sciences, Kuwait National Petroleum Company, Kuwait
University and Gulf Cooperation Council.
Editors
D.L. Trimm
School of Chemical Engineering and Industrial Chemistry, University of New
South Wales, Kensington, N. S. W., Australia
S. Akashah and M.A bsi-Halabi
Kuwait Institute for Scientific Research, Safat, Kuwait
and
A. Bishara
Kuwait University, Department of Chemical Engineering, Safat , Kuwait
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IX
FOREWOBD
This volume presents the proceedings of the Conference on Catalysts in Petroleum
Refining, held in Kuwait between March 5 and 8, 1989. This meeting was the
first international conference on catalysis in the oil industry to be held in the Middle
East, despite the fact that the area is one of the main sourcea of crude oil and a
major user of petroleum related catalysts. It bean tribute to the increasing technical
infra-structure which is growing in variow Middle East countries
The papers and the audience came from all over the world, and an excellent
balance was struck in selecting articles both from academia and industry. Current
trends in the oil industry focused attention mainly on heavy end hydrotreating, but
other processes also gained their share of attention. One invaluable feature of the
meeting was the two panel discussions where participants took the opportunity to
obtain " off the record " advice on many real and immediate problems
Over 230 participants enjoyed the scientific programme and the superb hospitality
offered by the hosts From H.H. the Crown Prince and Prime Minister on
downwards, the intemt and welcome was overwhelming. Not least enjoyed was the
chance to see one of the mast modem refineries in the world at work.
The 8ucces9 of the meeting is only partly reflected in these proceedings Never-
theless, they give some flavour of the high standards obaerved throughout the confer-
ence. The conference will be held again in the Middle East in 1993, and one looks
forward to an event which has much to live up to.
D. L. TBIMM
X
PREFACE
This Conference on Catalysts in Petroleum Refining was located in Kuwait in response
to the importance of the region to oil production and processing. Recognising the need to
treat hcavier and heavier ends of the barrel, attention was focused on hydrotreating and resid
processing, although significant interest was focused on catalytic aspects of the processing
of lighter fractions. An important part of the conference was the opportunity to participate
in pancl discussions based 0x1 industrial and academic expericncc in the field.
The proceedings reflect the important role of catalysis in petroleum refining and thc
effect of factors such as enviromental legislation on the industry. They also show the errier-
gence of significant scientific expertise in the Middle East - the cradlc of the oil industry.
Well over 200 participants from all over thc world enjoyed some excellcnt presentations.
The task of editor-in-chief can be impossible or delightful. My task was made dc-
lightful by the efforts of superb scientific aiidd editorial committees, whose iiaiiies are listed
hclow. Particular thanks are also duc to Dr. Saed Akashah and thc secretarial staff at
the Kuwait Institute of Scientific Research - for their friendship, their hard work and their
efficiency.
D.L .TRIMM
XI
ORGANIZING COMMITTEE
Dr. Sad Akashah Chairman Kuwait Institute for Scientific Research
Mr. Adnan Abdul Mohsen Rapporteur Kuwait Foundation for Advancement of Sciences
Mr. Abdul Rahman Al-Jasser Coordinator Kuwait Institute for Scientific Research
Dr. Anwar Abdullah Member Gulf Cooperation Council
Dr. Ahmed Bishara Member Kuwait University
Dr. Abbas Ali Khan Member Kuwait Foundation for Advancement of Sciences
Mr. Ramzi Nuseibeh Member Kuwait National Petroleum Company
Dr. Mamun Absi-Halabi Member Kuwait Institute for Scientific Research
Mr. Abdel Moniem Ahmed Member Kuwait Institute for Scientific Research
SCIENTIFIC ADVISORY COMMITTEE
Dr. Ahmed Bishara Chairman, Kuwait University KUWAIT
Dr. David Trimm Member, University of New South Wales AUSTRALIA
Dr. BUy Crynes Member, University of Oklahoma U.S.A.
Dr. Siegfried Nowak Member, Academic der When Schatten der DDRAUSTRALIA
Dr. Bernard Delmon Member, Universite’ Catholique de Louvain GDR
Dr. Henrik Topsoe Member, Halder T o p DENMARK
Dr. Mamun Absi-Halabi Member, Kuwait Institute for Scientific Research KUWAIT
SCIENTIFIC COMMITTEE
Dr. Mamun Absi-Halabi Chairman Kuwait Institute for Scientific Research
Dr. Anthony Stanislaus Rapporteur Kuwait Institute for Scientific Research
Dr. Sohal Al-Fulaij Member Kuwait Institute for Scientific Research
Dr. Suleiman Diab Member Kuwait Institute for Scientific Research
Dr. Mohammed Fahim Member Kuwait Institute for Scientific Research
Dr. Ali Katrib Member Kuwait University
Mr. Mustafa Embaby Member Kuwait National Petroleum Company
XI1
ACKNOWLEDGEMENT
The Catalysts in Petroleum Refining Conference was organised and held in Kuwait in
order to aquaint the participants with latest development in catalytic processes in Petroleum
refining and to provide a forum of exchange of ideas and views among the scientists and
engineers.
The Organizing Committee was deeply honoured by the patronage of H.H. The
Crown Prince and Prime Minister Sheikh Saad Al-Abdullah Al-Salem Al-Sabali
and his personal interest in the conference and the participants.
The Organizing Committee is also grateful for the support and sponsership of Kuwait
Institute of Scientific Research, Kuwait Foundation for the Advancement of Sciences, Kuwait
National Petroleum Company, Kuwait University and the Gulf Cooperation Council.
We are also appreciative of Elsevier Science Publishing company for their help and
cooperation and the members of the International Advisory Committee and the Scientific
Committee for their diligence and hard work
Finally, I thank my colleagues on the Organising Committee for the trust and the
honour of chairing this conference.
DR. SAED AKASHAH
CHAIRMAN
ORGANIZING COMMITTEE
D.L. Trimm et al. (Editors), Catalysts in Petroleum Refining 1989 1
0 1990 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
ADVANCES IN HYDROPURIFICATION CATALYSTS AND
CATALYSIS
Bernard DELMON
Unit6 de Catalyse et Chimie des MatCriaux DivisCs, Place Croix du Sud 1, 1348 Louvain-la-Neuve
(Belgium)
ABSTRACT
This contribution is an attempt to examine most important problems, at a fundamental level,
determining the future development of hydrotreating catalysts and further progresses in the
corresponding processes. The discussion is centered on the sulfided catalysts associating
molybdenum (or tungsten) with cobalt, nickel or iron.
A first section deals with characterization. Much progress has been made with respect to the
oxide precursor form. Recent advances concerning the activated (sulfided) form are impressive.
These advances are outlined. Additional tools, possibly those depending on the adsorption of probe
molecules, must be developed for deciding on critical issues. One such issue is whether activity is due
to a phase associating the Group VIII and the Group VI metal (so called "Co-Mo-S" and similar
phases), to special cobalt sulfides, to contacts between Group VI and Group VIII sulfides (remote
control) or to other causes.
A second section deals with preparation, activation, ageing and regeneration. Except for the
first item, only scarce data have been published. The very short discussion corresponding to this
section recalls recent advances in the understanding of activation and simulated regeneration, indicates
the areas where more knowledge is needed, and points to results having direct bearing on fundamental
issues.
The third section is devoted to mechanisms. Kinetic data are not discussed. New data and
speculations on the molecular mechanism of adsorption and hydrogenolysis of heteroatom containing
molecules are presented, and their possible consequences discussed. The connections of these
mechanisms with the real nature of the active catalyst are examined, with respect to structure of the
active center, supply of hydrogen to the active center and cooperation between Group VI and Group
VIII elements.
1. INTRODUCTION
The transformation to usable products of a very large proportion of crude oil rests on the
various cracking and hydrotreating processes. In the future, both groups of processes will also be the
key to the use of other natural hydrocarbon sources: tar sands, oil shales and biomass. They are also
necessary for making usable coal liquefaction products.
Considering only the second group, a volume of feed corresponding to about one third of the
total volume of oil extracted is hydrotreated. In spite of this exceptional importance of hydrotreating,
fundamental research on the corresponding catalysts and the way they work only began to take greater
importance after the first oil crisis. Even presently, many technical advances are still based on
empirical considerations. Typical, in this respect, is the development of catalysts with special pore
2
structures in the case of heavy feeds. The approach was successful to a certain extent. But it had to
neglect almost completely the chemistry of the process, for the simple reason that the latter was, and
still is, practically unknown.
For a relatively long period, industry was not very interested in a fundamental understanding
of the corresponding catalysts and reactions. The catalysts were cheap, and quantity could
compensate for quality. But a more detailed knowledge became necessary when the hydrotreating
processes became more complex and diversified: hydropurification (removal of S, N, 0, metals,
etc ...), hydroconversion (e.g. production of jet fuels or lubricants), and hydrocracking (mild or heavy
hydrocracking, with many different requirements according to cases). Now, the situation has become
normal, comparable to that in other fields of catalysis, in the sense that a reasonable number of
fundamental investigations are dedicated to the various aspects of hydrotreating. A fruitful exchange
of information between scientists conducting basic research and engineers in charge of the applied
developments is now beginning to take place.
The objective of the present contribution is to outline what we personally believe to be the
essential factors and the promising concepts with respect to the development of catalysts and processes
in the field of hydrotreating. We shall focus on fundamental data. The reasons are the following.
Basic research will some day show that a given feature is essential in HDS catalysts: this could be the
existence of a mixed Co-Mo-S phase, the role of a cooperation between phases or remote control, the
role of a cobalt sulfide of special structure in epitaxy with a given support, or possibly something not
yet mentioned. Industry controls sufficiently well the preparation techniques for being able to create
economically this particular feature in commercial catalysts. Basic research will also unveil the
mechanisms of the various catalytic reactions and side processes involved, and their kinetics. Then,
chemical engineering will provide the guideline for designing catalysts of optimal pore size, size
distribution and structure. This will be substantially more accurate, and the practical results will be
substantially better than what has been obtained empirically. These two groups of basic information,
namely the nature of the catalytic system and the reaction mechanism, are sufficient at present. It is
thus essential to focus our attention on them, in order to critically evaluate the available data, to
emphasize the important advances and to speculate on further desirable research. This is what we
shall try to do.
Scientific literature concerning hydrotreating catalysts has become extremely vast. However,
taking into account the above-mentioned objective, only a relatively limited number of papers provide
useful infomiation. One reason is that adequate characterization of the catalysts at the various stages
of their elaboration is not easy (essentially, as prepared, namely as oxide precursor, and as activated,
i.e. sulfided). On the other hand, quite a few papers are inadequate because of the use of test reactions
or reaction conditions which have been shown to be irrelevant (this is the case, in particular, of
reactions at atmospheric pressure or below, of reactions with improperly sulfided catalysts or of
removal of nitrogen or oxygen without proper addition of a proportion of sulfur sufficient to maintain
the catalyst in the sulfided state). Other papers do not provide sufficient basic information concerning
the reaction; for example, the analysis of a complex feed and the corresponding product might bc
insufficient. In principle, interesting results, namely results making some interpretations possible, can
be obtained with catalysts which are not extensively characterized, or in cases where analysis is
relatively incomplete. However, another serious problem may arise. It is that the corresponding
papers deal only with a couple of catalysts instead of series of systematically changing composition or
texture, or series activated under systematically varying conditions. Similarly, the number of reactions
studied, the number of reaction parameters and the extent of their rotation may be insufficient.
For these reasons, this contribution will not compile all papers published in the field. Rather, it
is intended to present our own views. We wish, in this manner, to subject them to the criticisms of
our colleagues working in the industry, applied research institutes, universities and research
laboratories. We would also wish to help stimulate research on a few decisive issues and propose
some crucial experiments.
We shall lay emphasis on hydropurification, especially sulfur removal. We shall touch on
hydroconversion, at least the hydrogenation of unsaturated molecules. The problem of the acidity
bringing about isomerisation, cracking and coking will be almost completely left aside. The reason for
this choice (possibly only partially justified) is that we believe that the most decisive problems in
hydrotreating are the nature of the phase or phases, or the surface features, whichever the case,
responsible for the catalytic activity and the mechanism of the reactions which take place on this
catalytic system.
A first section will deal with the characterization of catalysts, essentially the activated, namely
sulfided, catalysts. We wish to outline the existing possibilities in characterization and to indicate
crucial points which deserve attention in priority.
The second section will deal with what could be called the life or the history of catalysts, from
their preparation to their deactivation and death. This part will not be much detailed and will leave
space for independent review papers which hopefully should be written in the near future. We
essentially wish to emphasize the fact that hydrotreating catalysts can be extremely diverse in their
architecture and activity according to preparation, activation, ageing and regeneration and to highlight a
few important problems.
The third section, in our opinion the most important one, deals with mechanisms mentioning
new, sometimes surprising, certainly always stimulating, speculations. One aspect of the mechanism
is the interaction of reactant molecules with the surface, account taken of the active functions of the
latter and mechanism of hydrogenation and breaking of the heteroatom-carbon bond. Another aspect
deals with the promotion of the activity of Mo (or W) by Group VIII metals.
In the short conclusion of the paper, we wish to suggest that the advances in characterization,
role of preparation, activation and ageing on activity, and mechanisms will have a strong impact on the
future development of new catalysts and processes.
2. PHYSICO-CHEMICAL CHARACTERIZATION OF THE CATALYSTS
2.1. The precursor form (supported oxides)
Remarkable progress has been made in the characterization of the precursor form of the
hydropurification catalysts, namely the association of Mo or W with Co, Ni or Fe as oxides, deposited
on alumina. The essential features were fundamentally understood ten years ago (refs. 1-3), and
4
recent investigations with modern techniques essentially reproduce these results (refs. 4-6). Part of
the Group VIII metal gets trapped as a sort of pseudoaluminate in the support. The remaining metals
form a sort of bidimensional, non-stoechiometric, molybdate or tungstate of the Group VIII metal in
very strong interaction with alumina (refs. 2, 3,7).
The systematic use of the characterization techniques which became available during thc
seventies (refs. 1-3, 8- 15) certainly contributes to explaining the improvements of the commercial
catalysts: excellent dispersion of the oxide phase, minimization of the fraction of the Group VIII metal
trapped in the support, controlled distribution in the depth of the pellet, minimization of the unwanted
effects such as formation of aluminum molybdate or cobalt molybdate, elimination of impurities
working against dispersion, etc.. . In practice, all the essential information can be obtained by skilled
use of ESCA-XPS, Analytical Electron Microscopy (AEM), and conventional microprobe analysis.
UV Diffuse Reflectance Spectroscopy and ISS can also be used.
It is not clear whether the fact that Mo is tetrahedrically or octahedrically coordinated by
oxygen is very important with respect to the properties of the activated catalyst (after sulfidation),
namely whether this coordination very much influences the structure of the sulfides and the final
catalytic properties. There are strong indications that the details of the activation procedure have a
much more important influence and overshadow every detail, except dispersion, distribution and
trapping of the Group VIII metal in alumina. Nevertheless, methods like Raman Spectroscopy or
EXAFS might be used if this characterization turns out to be. essential.
A large number of investigations on "partial" catalysts (e.g. with only Co or Mo) or with
complete catalysts doped with a third element, or containing both Co and Ni (ref. 16), suggests that
the same methodology can be used with all oxide precursors :
general references : (refs. 14, 17-19)
Li : (refs. 20, 21)
Na : (refs. 22-29)
K : (ref. 20)
F : (refs. 30-32)
B : (refs. 33, 34)
P : (refs. 35-39)
The future advances in the characterization of the oxide precursors will certainly concern new,
more rapid and cheaper methods, the detection of the new phases which form with the additives (in
very small proportion, because of the low concentration of the latter) and the detection of non-uniform
distribution or of local accumulation of these additives.
2.2. The active, sulfided form: overall picture
In the course of time, focus of interest on the characterization of hydrotreating catalysts has
shifted from the oxide precursor to the sulfided, catalytically active form. A full characterization is
indeed needed for the understanding of the factors determining activity, for controlling the activation
procedure, and for evaluating the efficiency of regeneration.
