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Combinatorial Chemistry &
High Throughput Screening
ISSN: 1386-2073
Combinatorial Chemistry &
High Throughput Screening
Volume 10, Number 1, January 2007
Contents
Combinatorial Heterogeneous Catalysis (Part 1)
Guest Editor: József L. Margitfalvi
Editorial from Editor-in-Chief
Pp.1-2
Editorial from Guest Editor
Pp. 3-4
Discovery of New Heterogeneous Catalysts for the Selective
Oxidation of Propane to Acrolein Pp. 5-12
Kwang S. Oh, Do K. Kim, Wilhelm F. Maier and Seong I.
Woo
[Abstract] [Full
text article]
Zeolite Synthesis Modelling with Support Vector Machines:
A Combinatorial Approach Pp. 13-24
Jose M. Serra, Laurent A. Baumes, Manuel Moliner, Pedro
Serna and Avelino Corma
[Abstract] [Full
text article]
High Throughput Screening of Low Temperature CO Oxidation
Catalysts Using IR Thermography Pp. 25-35
Stephen Cypes, Alfred Hagemeyer, Zach Hogan, Andreas Lesik,
Guido Streukens, Anthony F. Volpe Jr., W. Henry Weinberg and
Karin Yaccato
[Abstract] [Full
text article]
Computational Methods in the Development of a Knowledge-Based
System for the Prediction of Solid Catalyst Performance
Pp. 37-50
Joanna Procelewska, Javier L. Galilea, Frederic Clerc,
David Farrusseng and Ferdi Schüth
[Abstract] [Full
text article]
Retrospective Hit-Deconvolution of Mixed Metal Oxides:
Spotting Structure-Property-Relationships in Gas Phase Oxidation
Catalysis Through High Throughput Experimentation
Pp. 51-57
Stephan A. Schunk, Andreas Sundermann and Hartmut Hibst
[Abstract] [Full
text article]
Implementation of the Multi-Channel Monolith Reactor
in an Optimisation Procedure for Heterogeneous Oxidation Catalysts
Based on Genetic Algorithms Pp. 59-70
Christian Breuer, Martin Lucas, Frank-Walter Schütze
and Peter Claus
[Abstract] [Full
text article]
Characterization of Trimetallic Pt-Pd-Au/CeO2
Catalysts Combinatorial Designed for Methane Total Oxidation
Pp. 71-82
András Tompos, József L. Margitfalvi, Mihály
Hegedus, Ágnes Szegedi, Jose Luis G. Fierro and Sergio
Rojas
[Abstract] [Full
text article]
Abstracts
[Back to top]
Editorial from Editor-in-Chief
As Combinatorial Chemistry & High Throughput Screening
begins its tenth year of publication, I would like to look
back at some of the highlights of these last ten years. The
initial effort to organize this journal was carried out in
1997 by John M. Pezzuto, when he was my colleague here at
the University of Illinois, Chicago. Due to a wealth of other
commitments, John Pezzuto stepped down from his role as the
founding editor of the journal, and I accepted the position
as Editor-in-Chief. Today, John Pezzuto is on the Editorial
Board of CCHTS and is Professor and founding Dean
of the College of Pharmacy of the University of Hawaii.
The first issue of CCHTS, consisting of four issues,
appeared in 1998. The next year, the publication frequency
was increased from four to six issues per year. Due to the
worldwide growth of research in combinatorial chemistry and
high throughput screening, the publication frequency of CCHTS
was increased again to eight issues when volume 4 was published
in 2001. At eight issues per year, CCHTS became the
leader in this field. By 2006, the large number of papers
in the publication queue prompted us to expand volume 9 to
10 issues per year, which established a new standard. The
benefit of frequent publication is that CCHTS has
minimal time between paper acceptance and publication.
From its inception, CCHTS has occupied a unique position
in the peer reviewed literature by focusing on the publication
of review articles and original research papers in combinatorial
chemistry, high throughput screening, and the interface of
these related fields. To the best of my knowledge, no other
journal specializes in this combination of topics. In addition,
the editorial policy of CCHTS has always been to
publish papers in all areas of combinatorial chemistry and
high-throughput screening, and this policy will continue with
volume 10. For example, readers of CCHTS this year
should expect to see papers ranging from the use of high throughput
screening for the optimization of solid-phase catalysts for
different chemical reactions (see this issue) to combinatorial
library synthesis using multicomponent reactions.
A reflection of the breadth of the readership of CCHTS
is the citation of papers published in this journal. Please
note the ten most cited papers appearing to date in CCHTS,
which are cited in order below [1-10]. Approximately half
of these papers concern combinatorial chemistry, such as combinatorial
chemical synthesis or computational rational design of combinatorial
libraries, and the other half of these highly cited papers
address high throughput screening methods and applications,
such as the application of fluorescence polarization to HTS
or virtual screening of combinatorial libraries. I would like
to congratulate the corresponding author Peter Schulz-Knappe
and his colleagues for contributing the most highly cited
paper so far to CCHTS [1]. In this paper, the term,
“peptidomics”, was coined, which is defined as
the process of analyzing and visualizing peptides and small
proteins from biological samples. In addition, I would like
to acknowledge Reto Crameri who served as the guest editor
for the special issue in which this peptidomics paper appeared.
As in the past, regular issues of CCHTS will be alternated
with special issues focusing on a single topic of current
interest. Some of these special issues will be organized by
members of our Editorial Board and others will be organized
by guest editors who will introduce fresh perspectives and
unique expertise to the journal. Readers should note that
all papers published in CCHTS are peer reviewed whether
they appear in a special issue on a hot topic or in a regular
issue.
Papers published in CCHTS receive high visibility,
since they are abstracted and indexed by the major services
including Chemical Abstracts, BIOSIS, CAB Abstracts, EMBASE,
BIOBASE, Science Citation Index-Expanded, MEDLINE, and Current
Contents (Life Sciences). Through the combination of frequent
publication, peer review and high visibility, Combinatorial
Chemistry & High Throughput Screening remains a unique
and essential scientific journal defining the intersection
of the interdependent disciplines of combinatorial chemistry
and HTS. I would like to thank the distinguished members of
the Editorial Board, the Regional Editors, the guest editors,
the authors, and of course you, the readers, for the continuing
success of our journal.
The 10 most cited papers appearing in Combinatorial Chemistry
& High Throughput Screening from 1998 to 2006 (according
to the Web-of-Science, produced by Thomson Scientific, Philadelphia,
PA; accessed on-line January 4, 2007 at http://scientific.thompson.com).
[1] Schulz-Knappe, P.; Zucht, H.D.; Heine, C.; Jurgens, M.;
Hess, R.; Schrader, M. Peptidomics: The comprehensive analysis
of peptides in complex biological mixtures. Comb. Chem.
High Throughput Screen., 2001, 4(2),
207-217. Cited 64 times.
[2] Lee, S.K.; Mbwambo, Z.H.; Chung, H.S.; Luyengi, L.; Gamez,
E.J.C.; Mehta, R.G.; Kinghorn, A.D.; Pezzuto, J.M. Evaluation
of the antioxidant potential of natural products. Comb.
Chem. High Throughput Screen., 1998,
1(1), 35-46. Cited 63 times.
[3] Nasir, M.S.; Jolley, M.E. Fluorescence polarization: An
analytical tool for immunoassay and drug discovery. Comb.
Chem. High Throughput Screen., 1999,
2(4), 177-190. Cited 54 times.
[4] Domling, A. Isocyanide based multicomponent reactions
in combinatorial chemistry. Comb. Chem. High Throughput
Screen., 1998, 1(1), 1-22.
Cited 53 times.
[5] Xue, L.; Bajorath, J. Molecular descriptors in chemoinformatics,
computational combinatorial chemistry, and virtual screening.
Comb. Chem. High Throughput Screen., 2000,
3(5), 363-372. Cited 45 times.
[6] Masimirembwa, C.M.; Thompson, R.; Andersson, T.B. In vitro
high throughput screening of compounds for favorable metabolic
properties in drug discovery. Comb. Chem. High Throughput
Screen., 2001, 4(3), 245-263.
Cited 42 times.
[7] Sun, C.M. Recent advances in liquid-phase combinatorial
chemistry. Comb. Chem. High Throughput Screen., 1999,
2(6), 299-318. Cited 42 times.
[8] Ugi, I.; Heck, S. The multicomponent reactions and their
libraries for natural and preparative chemistry. Comb.
Chem. High Throughput Screen., 2001,
4(1), 1-34. Cited 34 times.
[9] Matter, H.; Baringhaus, K.H.; Naumann, T.; Klabunde, T.;
Pirard, B. Computational approaches towards the rational design
of drug-like compound libraries. Comb. Chem. High Throughput
Screen., 2001, 4(6), 453-475.
Cited 33 times.
[10] Drolet, D.W.; Jenison, R.D.; Smith, D.E.; Pratt, D.;
Hicke, B.J. A high throughput platform for systematic evolution
of ligands by exponential enrichment (SELEX™). Comb.
Chem. High Throughput Screen., 1999,
2(5), 271-278. Cited 32 times.
Richard B. van Breemen
(Editor-in-Chief)
University of Illinois
College of Pharmacy
833 S. Wood Street
Chicago
IL 60612
USA
E-mail: breemen@uic.edu
[Back to top]
Editorial from Guest Editor
Combinatorial Heterogeneous Catalysis
These special issues (Vol. 10, No. 1 and
Vol. 10, No. 2) are devoted to progress
in the area of Combinatorial Heterogeneous Catalysis (CHC),
which can be considered to be the general application of combinatorial
and high-throughput methods and strategies in materials research.
Heterogeneous catalysis plays a vital role if our everyday
lives. All pollution-free and environmentally friendly industrial
processes in oil refineries, chemical plants, and power energy
stations need highly active and selective catalysts. Catalysts
are used in cars and trucks to remove harmful products of
incomplete oxidation of gasoline or diesel fuel. The plastics
used in everyday life are prepared by applying very specific
highly active and selective catalysts, and this list can be
continued. Better catalysts reduce productions costs, reduce
the formation of wasteful by-products, and help to decrease
atmospheric pollution. These are the main reasons that the
search for new and better catalysts is a permanent R &
D task.
In general, combinatorial approaches are intended to find
the optimum formulation in various pharmaceutical or engineering
materials including catalysts, with the shortest interval
and minimum amount of unit cost. In this case the focus is
laid on the optimum performance with decreased overall costs.
All combinatorial approaches are based on the diversity of
the system investigated. This diversity determines the parameter
space where the optimum performance may be found. In combinatorial
materials research, including CHC, the following key components
of diversity can be distinguished: (i) compositional; (ii)
process; and (iii) structural. The structural diversity is
determined by the first two components. In order to move in
a large experimental space towards the optimum performance,
the following requirements must be fulfilled: (i) high throughput
methods in synthesis, testing, and analysis; (ii) highly reliable
and reproducible analytical methods; (iii) effective optimization
and information mining tools; and (iv) appropriate data handling
and management methods.
Today, combinatorial heterogeneous catalysis is a well-acknowledged
area of catalysis sciences, although a definite part of our
scientific community still remains quite critical. Methods
of combinatorial catalysis are widely used both in applied
and academic laboratories. Symyx Technologies was the first
company devoted to the area of combinatorial heterogeneous
catalysis. Among the followers are the Dutch company Avantium
Technologies, the German group “hte GmbH”, etc.
In the last 10 years, most of the large oil and chemical companies
created their own laboratories in combinatorial catalysis.
In academia, various combinatorial heterogeneous laboratories
have emerged in various countries, such as Australia, Japan,
Korea, Singapore, Germany, the Netherlands, Belgium, France,
UK, Norway, Spain, Hungary, Canada, USA, China, India, and
Mexico. These laboratories may be considered as the pioneers
in this field. Consequently, there is considerable geographical
diversity in the location of key laboratories.
The importance of this field has been documented by various
international meetings fully or partly devoted to CHC. Most
of the international meetings in the field of heterogeneous
catalysis have an independent section devoted fully to high
throughput and combinatorial methods. In several highly ranked
meetings (Europacat, International Catalysis Congress), round
table discussions took place that were excellent forums for
listening to both the pros and the cons of CHC. It should
be mentioned that there is a special “heterogeneous
catalysis” section at the Gordon Research Conferences
devoted to the field of combinatorial materials research.
If we look back to the first publications in the area of CHS,
we see that the focus has been on the methodology and the
use of high-throughput techniques and technologies. In this
period, gas phase catalytic reactions were usually investigated.
Today, after ten years of practice in this field, the area
of activity in CHC has been expanded considerably. Combinatorial
methods are used today to develop catalysts for applications
such as (i) gas and liquid phase reaction both at atmospheric
and high pressures; (ii) electro-catalysts for fuel cell technology;
and (iii) photo-catalysts for water splitting and environmental
control. New sophisticated preparation methods, such as inkjet
printing, laser ablation, co-spattering, etc., are also being
applied. The use of micro-reactor technologies and complete
atomization and robotization is now common. In addition, ever
more attention is now being paid on optimization, information
mining, and data handling - in other words, on the development
of a complex informatic workflow.
This approach is also reflected by the content of this special
issue, where new aspects of combinatorial heterogeneous catalysis
are discussed, such as the use of methods of computational
chemistry, application of prediction and modeling tools, use
of new visualization and optimization methods, and description
of a complex new informatic platform. In addition, new preparation
and screening methods are also described and the use of high-throughput
method for “knowledge extraction” is presented
as well.
As guest editor, have tried my best to increase the geographical
diversity of the authors. This effort is reflected by the
selection of authors representing different countries including
Australia, France, Germany, Hungary, Japan, Korea, Spain,
The Netherlands, and the United States. Altogether, 13 contributions
will be published in two parts.
I would like to thank all the authors and reviewers for their
contributions, help and cooperation. I hope that this special
issue will help the existing and newly forming groups all
around the world to strengthen the position and acceptance
of combinatorial heterogeneous catalysis. I also believe that
as more success stories are published in this field, resistance
from the academic society will diminish. In this case, we
can also hope that the results obtained using combinatorial
and high-throughput methods can be freely published in leading
catalysis journals, too. I would also suggest for all of those
who are still skeptical and are against the use of “combi”
approaches in academic research to visit as many “combi”
laboratories as possible and talk and listen to students and
young scientists working successfully in this field. When
you will look into the proud eyes of these young people, you
will get the right message portraying the future of combinatorial
heterogeneous catalysis.
József L. Margitfalvi
(Guest Editor)
Department of Organic Catalysis
Institute of Surface Chemistry and Catalysis
Chemical Research Center
Hungarian Academy of Sciences
Budapest
Hungary
E-mail: joemarg@chemres.hu
[Back to top]
Discovery of New Heterogeneous Catalysts for the Selective
Oxidation of Propane to Acrolein
Kwang S. Oh, Do K. Kim, Wilhelm F. Maier and Seong I.
Woo
[Full
text article]
Combinatorial synthesis and screening technique have been
applied to investigate the catalytic activity and selectivity
of ternary and quaternary mixed-metal oxide catalysts for
the selective oxidation of propane. The catalyst libraries
were prepared via a modified sol-gel method using
a synthesis robot and library design software, and examined
for the catalytic activities in a simple high-throughput reactor
system connected to a mass spectrometer for product analysis.
Ternary Mo-Cr-Te, V-Cr-Sb, and Mo-V-Cr catalysts have been
selected for potential candidate by composition spread approach.
In a next generation composition spread library, the composition
space of these three ternary compositions was sampled. Screening
of this 198-member library provided substantial evidence that
each ternary system has its own optimum composition where
acrolein formation is highest. In addition, the composition
space of the quaternary reference system Mo-V-Te-Nb mixed-oxides
has also been prepared and sampled.
[Back to top]
Zeolite Synthesis Modelling with Support Vector Machines:
A Combinatorial Approach
Jose M. Serra, Laurent A. Baumes, Manuel Moliner, Pedro
Serna and Avelino Corma
[Full
text article]
This work shows the application of support vector machines
(SVM) for modelling and prediction of zeolite synthesis, when
using the gel molar ratios as model input (synthesis descriptors).
Experimental data includes the synthesis results of a multi-level
factorial experimental design of the system TEA:SiO2:Na2O:Al2O3:H2O.
The few parameters of the SVM model were studied and the fitting
performance is compared with the ones obtained with other
machine learning models such as neural networks and classification
trees. SVM models show very good prediction performances and
generalization capacity in zeolite synthesis prediction. They
may overcome overfitting problems observed sometimes for neural
networks. It is also studied the influence of the type of
material descriptors used as model output.
[Back to top]
High Throughput Screening of Low Temperature CO Oxidation
Catalysts Using IR Thermography
Stephen Cypes, Alfred Hagemeyer, Zach Hogan, Andreas Lesik,
Guido Streukens, Anthony F. Volpe Jr., W. Henry Weinberg and
Karin Yaccato
[Full
text article]
The catalytic oxidation of carbon monoxide to carbon dioxide
is an important process used in several areas such as respiratory
protection, industrial air purification, automotive emissions
control, CO clean-up of flue gases and fuel cells. Research
in this area has mainly focused on the improvement of catalytic
activity at low temperatures. Numerous catalyst systems have
been proposed, including those based on Pt, Pd, Rh, Ru, Au,
Ag, and Cu, supported on refractory or reducible carriers
or dispersed in perovskites. Well known commercial catalyst
formulations for room temperature CO oxidation are based on
CuMn2O4 (hopcalite) and CuCoAgMnOx mixed
oxides. We have applied high-throughput and combinatorial
methodologies to the discovery of more efficient catalysts
for low temperature CO oxidation. The screening approach was
based on a hierarchy of qualitative and semi-quantitative
primary screens for the discovery of hits, and quantitative
secondary screens for hit confirmation, lead optimization
and scale-up. Parallel IR thermography was the primary screen,
allowing one wafer-formatted library of 256 catalysts to be
screened in approximately 1 hour. Multi-channel fixed bed
reactors equipped with imaging reflection FTIR spectroscopy
or GC were used for secondary screening. Novel RuCoCe compositions
were discovered and optimized for CO oxidation and the effect
of doping was investigated for supported and bulk mixed oxide
catalysts. Another family of active hits that compare favorably
with the Pt/Al2O3 benchmark is based
on RuSn, where Sn can be used as a dopant (e.g. RuSn/SiO2)
and/or as a high surface area carrier (e.g., SnO2
or Sn containing mixed metal oxides). Also, RuCu binary compositions
were found to be active after a reduction pretreatment with
hydrogen.
[Back to top]
Computational Methods in the Development of a Knowledge-Based
System for the Prediction of Solid Catalyst Performance
Joanna Procelewska, Javier L. Galilea, Frederic Clerc,
David Farrusseng and Ferdi Schüth
[Full
text article]
The objective of this work is the construction of a correlation
between characteristics of heterogeneous catalysts, encoded
in a descriptor vector, and their experimentally measured
performances in the propene oxidation reaction. In this paper
the key issue in the modeling process, namely the selection
of adequate input variables, is explored. Several data-driven
feature selection strategies were applied in order to obtain
an estimate of the differences in variance and information
content of various attributes, furthermore to compare their
relative importance. Quantitative property activity relationship
techniques using probabilistic neural networks have been used
for the creation of various semi-empirical models. Finally,
a robust classification model, assigning selected attributes
of solid compounds as input to an appropriate performance
class in the model reaction was obtained. It has been evident
that the mathematical support for the primary attributes set
proposed by chemists can be highly desirable.
[Back to top]
Retrospective Hit-Deconvolution of Mixed Metal Oxides:
Spotting Structure-Property-Relationships in Gas Phase Oxidation
Catalysis Through High Throughput Experimentation
Stephan A. Schunk, Andreas Sundermann and Hartmut Hibst
[Full
text article]
Complex multi-element lead structures of mixed metal oxides
that may be identified as hits during high throughput experimentation
(HTE) campaigns, can be deconvoluted retrospectively on the
basis of simple binary and ternary oxides as illustrated in
the current example of a hit found in an ammoxidation reaction.
On the basis of the performance of the simple binary and ternary
mixed metal oxides structure property relationships can be
established, that give insight into the roles of the different
components of the complex mixed metal oxides and may also
help in establishing a reaction mechanism and converting the
hit into a development candidate.
[Back to top]
Implementation of the Multi-Channel Monolith Reactor
in an Optimisation Procedure for Heterogeneous Oxidation Catalysts
Based on Genetic Algorithms
Christian Breuer, Martin Lucas, Frank-Walter Schütze
and Peter Claus
[Full
text article]
A multi-criteria optimisation procedure based on genetic algorithms
is carried out in search of advanced heterogeneous catalysts
for total oxidation. Simple but flexible software routines
have been created to be applied within a search space of more
then 150,000 individuals. The general catalyst design includes
mono-, bi- and trimetallic compositions assembled out of 49
different metals and depleted on an Al2O3
support in up to nine amount levels. As an efficient tool
for high-throughput screening and perfectly matched to the
requirements of heterogeneous gas phase catalysis - especially
for applications technically run in honeycomb structures -
the multi-channel monolith reactor is implemented to evaluate
the catalyst performances. Out of a multi-component feed-gas,
the conversion rates of carbon monoxide (CO) and a model hydrocarbon
(HC) are monitored in parallel. In combination with further
restrictions to preparation and pre-treatment a primary screening
can be conducted, promising to provide results close to technically
applied catalysts. Presented are the resulting performances
of the optimisation process for the first catalyst generations
and the prospect of its auto-adaptation to specified optimisation
goals.
[Back to top]
Characterization of Trimetallic Pt-Pd-Au/CeO2
Catalysts Combinatorial Designed for Methane Total Oxidation
András Tompos, József L. Margitfalvi, Mihály
Hegedus, Ágnes Szegedi, Jose Luis G. Fierro and Sergio
Rojas
[Full
text article]
In the present work, the role and the effect of platinum and
gold on the catalytic performance of ceria supported tri-metallic
Pt-Pd-Au catalysts have been studied. The optimum composition
of these tri-metallic supported catalysts has been discovered
using methods and tools of combinatorial catalyst library
design. Detailed catalytic, spectroscopic and physico-chemical
characterization of catalysts in the vicinity of the optimum
in the given compositional space has been performed. The temperature-programmed
oxidation of methane revealed that the addition of Pt and
Au to Pd/CeO2 catalyst resulted in higher conversion
values in the whole investigated temperature range compared
to the monometallic Pd catalyst. The time-on-stream experiments
provided further evidence for the high-stability of tri-metallic
catalysts compared to the monometallic one. Kinetic studies
revealed the stronger adsorption of methane on Pt-Pd/CeO2
catalysts than over Pd/CeO2. XPS analysis showed
that Pt and Au stabilize Pd in a more reduced form even under
condition of methane oxidation. FTIR spectroscopy of adsorbed
CO and hydrogen TPD measurements provided indirect evidences
for alloying of Pt and Au with Pd. CO chemisorption data indicated
that tri-metallic catalysts have increased accessible metallic
surface area. It is suggested that advantageous catalytic
properties of tri-metallic Pt-Au-Pd/CeO2 catalysts
compared to the monometallic one can be attributed to (i)
suppression of the formation of ionic forms of Pd(II), (ii)
reaching an optimum ratio between PdO and PdO species,
and (iii) stabilization of Pd in high dispersion. The results
also indicate that PdO– PdO ensemble sites
are required for methane activation.
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