Tanaka, K.
Solvent-free Organic Synthesis
Second, Completely Revised and Updated Edition
2009
ISBN: 978-3-527-32264-0
Lefler, J.
Principles and Applications of Supercritical Fluid Chromatography
2009
ISBN: 978-0-470-25884-2
Wasserscheid, P., Welton, T. (eds.)
Ionic Liquids in Synthesis
Second, Completely Revised and Enlarged Edition
2008
ISBN: 978-3-527-31239-9
Sheldon, R. A., Arends, I., Hanefeld, U.
Green Chemistry and Catalysis
2007
ISBN: 978-3-527-30715-9
Lindstrom, U. M. (ed.)
Organic Reactions in Water
Principles, Strategies and Applications
2008
ISBN: 978-1-4501-3890-1
Volume 4
Supercritical Solvents
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ISBN: 978-3-527-32590-0
For several centuries, Chemistry has strongly contributed to a fast and almost unlimited trend of progress and innovation that have deeply modified and improved human life in all its aspects. But, presently, chemistry is also raising fears about its immediate and long-term impact on environment, leading to a growing demand for development of “green chemistry” preserving environment and natural non-renewable resources. Changing raw materials to renewable sources, using low energy-consumption processes, reprocessing all effluents and inventing new environment-friendly routes for the manufacture of more efficacious products are immense challenges that will condition the future of mankind.
In this context of sustainable development, Supercritical Fluids (SCF) and Gas-Expanded Liquids (GXL) are of rapidly-growing interest because either they are non-toxic and non-polluting solvents (like carbon dioxide or water) or they help one to avoid harmful intermediates through new processing routes. After two decades of development of new extraction/fractionation/purification processes using SCFs - mainly CO2 - with about 250 industrial-scale plants now in operation around the world, other applications have been and will be at the centre of new developments for the present decade and the coming one:
It has to be understood that moving to SCF or GXL media for chemical synthesis shall not be considered as a “simple” substitution of “classical” organic solvents, but imposes a complete “reset” of knowledge of synthesis routes, reaction schemes and parameters. One main difference is related to the physico-chemical properties of these fluids that are both “tunable” solvents and separation agents. Some are also reactants at the same time. Because of these properties, reaction rate and selectivity are very different from those observed in liquid media, as well exemplified by hydrogenation reactions over heterogeneous catalysts. Moreover, many new environmentally-friendly processes using CO2 and water lead to innovative high-tech materials (especially nano-structured materials), biomass conversion and waste treatment such as, for example, PET-residues recycling by hydrothermal depolymerisation.
This is why this new edition, deeply revised and dealing with new areas, arrives at an optimal moment when scientists and engineers are facing the new challenges of sustainable development and demand for higher-performance products. In the fast-changing world of science, this update is a necessary tool offered to help the scientific community appreciate the opportunities presented by these fluids and to prepare chemists and engineers to incorporate these techniques in their process “tool-box”.
March 2009
Reactions under supercritical conditions have been used for industrial production on various scales for most of the 20th century, but the current intense academic interest in the science and applications of supercritical fluids (SCFs) dates from the mid 1980's (Figure 1) and the application of SCFs in the chemical synthesis of organic molecules or materials became a “hot topic” starting in the early 1990's. Processes involving SCFs can be conducted in a fully homogeneous monophasic fluid or in biphasic systems. Biphasic conditions can involve a supercritical or subcritical gas as the upper phase and a gas-expanded liquid (GXL) below. The optimum situation is often a delicate balance of thermodynamic and kinetic boundaries for a given transformation. This book is intended to introduce the reader to the wide range of opportunities provided by the various synthetic methodologies developed so far for synthesis in SCFs and GXLs.
Applications of SCFs include their use as solvents for extractions, as eluents for chromatography, and as media for chemical reactions. All of these are worthy topics for extensive scientific and technical discussion, and in fact have been topics of books in the past. We decided that a satisfactory coverage of all three topics would not be possible in a single monograph of a reasonable size, and therefore we chose to cover only one. While extractions such as decaffeination of coffee and chromatography such as the supercritical CO2-based preparative chromatography used in the pharmaceutical industry are great examples of the environmental and economic benefits of SCFs, we focus here on chemical synthesis where the fluid is not only used as a mass separation agent, but also directly affects the molecular transformation.
Supercritical fluids and gas-expanded liquids may be alternatives to liquid solvents, but they are neither simple nor simply replacements of solvents. The experimental chemist could not modify a written synthetic method by simply crossing out the word “benzene” and replacing it with the words “supercritical carbon dioxide”. Many other modifications to the procedure would be necessary, not only because of the need for pressurized equipment but also because of the inferior solvent strength of many SCFs. On the other hand, additional degrees of freedom in the reaction parameters emerge from the high compressibility of SCFs, allowing density to be introduced as an important variable. At the same time, mass transfer can be greatly enhanced in the presence of SCFs. Selective separation and compartmentalization of elementary processes in multiphase systems offer another parameter that can be exploited especially in catalytic processes. These are only some of the reasons why the result of a chemical synthesis can sometimes be dramatically changed, often for the better, by this solvent switch. If such beneficial effects can be combined with the benign nature of many SCFs such as CO2 or H2O, they can contribute to the development of more sustainable chemical processes, explaining why SCFs and GXLs are often referred to as “Green Solvents”.
It is only fair to say that we are still far away from a detailed understanding of all the effects of using SCFs and GXLs. More basic research will be needed before we learn how to exploit the benefits in the most efficient way. In the meantime, it is our hope that the chemist or engineer considering using one of these fluids as a medium for a reaction will turn to this volume to find out both what has been done, how to do it, and, more importantly, what new and innovative directions are yet to be taken.
At this point, we must offer a safety warning and disclaimer. Supercritical fluids are used at high pressures and in some cases at elevated temperatures. The chemist contemplating their use must become acquainted with the safety precautions appropriate for experiments with high pressures and temperatures. Some SCFs also have reactive hazards. The safety considerations mentioned in Chapters 1 and 2 are meant neither to be comprehensive nor to substitute for a proper investigation by every researcher of the risks and appropriate precautions for a contemplated experiment.
We have selected the chapter topics to guide the reader through the process of planning and carrying out chemical syntheses in SCFs and GXLs. The subjects include a brief overview of the historical development and current use, as well as a description of equipment, methods, and phase behaviour considerations. The properties of biphasic conditions and gas-expanded liquids are spelled out in chapter 4, and all these themes are elaborated upon in the largest part of the book which is devoted to various types of chemical reactions involving SCFs and GXLs as solvents and/or reactants. The emphasis is on synthetic reactions, rather than reactions tested for the purpose of investigating near-critical phenomena.
This book represents a partial update of our 1999 book on “Chemical Synthesis Using Supercritical Fluids”, but most of the chapters are entirely new and the selection of topics is not the same. We therefore encourage readers, if they want more information, to look up the 1999 book.
The contributors to the present volume, all leading experts in the field, have given us a wide view of the types and methods of chemistry being performed in supercritical fluids and expanded liquids. Many of the techniques that the reader will find described in these pages have been laboriously developed by these contributors and their colleagues. We gratefully thank all of the contributors for agreeing to take time out from their research schedules to write chapters for this volume.
We also thank the following people and institutions for providing us with information or photographic material on the historical aspects and the industrial use of SCFs: Dr. J. Abeln (Forschungszentrum Karlsruhe), Dr. U. Budde (Schering AG), Dr. H.-E. Gasche (Bayer AG), Dr. P. Møller (Poul Møller Consultancy), Dr. T. Muto (Idemitsu Petrochemical), Prof. G. Ourisson and the Académie des Sciences, Dr. A. Rehren (Degussa AG), M.-C. Thooris (Ecole Polytechnique Palasieau) and representatives of Eco Waste Technology and General Atomics.
Special thanks are due to Dr. Markus Höslcher at ITMC, RWTH Aachen, and Drs. Elke Maase and Lesley Belfit at Wiley-VCH for their competent help and collaboration in producing this book. Furthermore, we wish to express our sincere thanks to all the members of our research groups, for their talents and their enthusiasm, which make our research efforts devoted to SCFs and GXLs so much fun.
Finally, and most importantly, we dedicate our own contribution to this book to our wives and families, for all their love and understanding throughout the years and especially during the preparation of this volume.
February 2009
Paul T. Anastas joined Yale University as Professor and serves as the Director of the Center for Green Chemistry and Green Engineering there. From 2004–2006, Paul was the Director of the Green Chemistry Institute in Washington, D.C. Until June 2004 he served as Assistant Director for Environment at the White House Office of Science and Technology Policy where his responsibilities included a wide range of environmental science issues including furthering international public-private cooperation in areas of Science for Sustainability such as Green Chemistry. In 1991, he established the industry-government-university partnership Green Chemistry Program, which was expanded to include basic research, and the Presidential Green Chemistry Challenge Awards. He has published and edited several books in the field of Green Chemistry and developed the 12 Principles of Green Chemistry.
Philip Jessop is the Canada Research Chair of Green Chemistry at Queen's University in Kingston, Ontario, Canada. After his Ph.D. (Inorganic Chemistry, UBC, 1991) and a postdoctoral appointment at the University of Toronto, he took a contract research position in the Research Development Corp. of Japan under the supervision of Ryoji Noyori, investigating reactions in supercritical CO2. As a professor at the University of California-Davis (1996–2003) and then at Queen's University, he has studied green solvents, the conversion of waste CO2 to useful products, and aspects of H2 chemistry. He has presented popular chemistry shows to thousands of members of the public. Distinctions include the Canadian Catalysis Lectureship Award (2004), a Canada Research Chair (2003 to present), and the NSERC Polanyi Award (2008). He has chaired the 2007 CHEMRAWN and ICCDU Conference on Greenhouse Gases, will chair the 2010 3rd International IUPAC Conference on Green Chemistry, and serves as Technical Director of GreenCentre Canada.
Walter Leitner was born in 1963. He obtained his Ph.D. with Prof. Henri Brunner at Regensburg University in 1989 and was a Postdoctoral Fellow with Prof. John M. Brown at the University of Oxford. After research within the Max-Planck-Society under the mentorship of Profs. Eckhard Dinjus (Jena) and Manfred T. Reetz (Mülheim), he was appointed Chair of Technical Chemistry and Petrochemistry at RWTH Aachen University in 2002 as successor to Prof. Willi Keim. Walter Leitner is External Scientific Member of the Max-Planck-Institut für Kohlenforschung and Scientific Director of CAT, the joint Catalysis Research Center of RWTH Aachen and the Bayer Company.
His research interests are the molecular and reaction engineering principles of catalysis as a fundamental science and key technology for Green Chemistry. In particular, this includes the development and synthetic application of organometallic catalysts and the use of alternative reaction media, especially supercritical carbon dioxide, in multiphase catalysis. Walter Leitner has published more than 170 publications in this field and co-edited among others the first edition of “Synthesis using Supercritical Fluids” and the handbook on “Multiphase Homogeneous Catalysis”. Since 2004, he serves as the Scientific Editor of the Journal “Green Chemistry” published by the Royal Society of Chemistry. The research of his team has been recognized with several awards including the Gerhard-Hess-Award of the German Science Foundation (1997), the Otto-Roelen-Medal of Dechema (2001), and the Wöhler-Award of the German Chemical Society (2009).
Douglas C. Barnes
University of Leeds
School of Chemistry
Leeds LS2 9JT
UK
Uwe Beginn
University of Osnabrück
Institute for Chemistry
Organic Materials Chemistry
Barbarastrasse 7
49076 Osnabrück
Germany
Teresa De Diego
Universidad de Murcia
Facultad de Química
Departamento de Bioquímica y Biología Molecular “B” e Inmunología
P.O. Box 4021
30 100 Murcia
Spain
Charles A. Eckert
Georgia Institute of Technology
School of Chemical and Biomolecular Engineering
School of Chemistry and Biochemistry
Specialty Separations Center
Atlanta, GA 30332
USA
Neil R. Foster
The University of New South Wales
School of Chemical Sciences and Engineering
Sydney 2052
Australia
Roger Gläser
University of Leipzig
Institute of Chemical Technology
Linnéstrasse 3
04103 Leipzig
Germany
Jason P. Hallett
Georgia Institute of Technology
School of Chemical and Biomolecular Engineering
School of Chemistry and Biochemistry
Specialty Separations Center
Atlanta, GA 30332
USA
Buxing Han
Chinese Academy of Sciences
Institute of Chemistry
Beijing National Laboratory for Molecular Sciences
Beijing 100080
China
Ulrich Hintermair
RWTH Aachen
Institut für Technische Chemie
Worringerweg 1
52074 Aachen
Germany
José L. Iborra
Universidad de Murcia
Facultad de Química
Departamento de Bioquímica y Biología Molecular “B” e Inmunología
P.O. Box 4021
30 100 Murcia
Spain
Philip G. Jessop
Queen's University
Department of Chemistry
90 Bader Lane
Kingston
ON K7L 3N6
Canada
Andrea Kruse
Technische Universität Darmstadt
Ernst-Berl-Institut für Technische und Makromoleculare Chemie
Technische Chemie I
Petersenstrasse 20
64287 Darmstadt
Germany
Walter Leitner
RWTH Aachen
Institut für Technische Chemie
Worringerweg 1
52074 Aachen
Germany
Charles L. Liotta
Georgia Institute of Technology
School of Chemical and Biomolecular Engineering
School of Chemistry and Biochemistry
Specialty Separations Center
Atlanta, GA 30332
USA
Zhemin Liu
Chinese Academy of Sciences
Institute of Chemistry
Beijing National Laboratory for Molecular Sciences
Beijing 100080
China
Pedro Lozano
Universidad de Murcia
Facultad de Química
Departamento de Bioquímica y Biología Molecular “B” e Inmunología
P.O. Box 4021
30 100 Murcia
Spain
Frank P. Lucien
The University of New South Wales
School of Chemical Sciences and Engineering
Sydney 2052
Australia
Patricia Ann Mabrouk
Northeastern University
Department of Chemistry and Chemical Biology
360 Huntington Avenue
Boston, MA 02115
USA
Raffaella Mammucari
The University of New South Wales
School of Chemical Sciences and Engineering
Sydney 2052
Australia
Martyn Poliakoff
University of Nottingham
Department of Chemistry
Nottingham NG7 2RD
UK
Pamela Pollet
Georgia Institute of Technology
School of Chemical and Biomolecular Engineering
School of Chemistry and Biochemistry
Specialty Separations Center
Atlanta, GA 30332
USA
Christopher M. Rayner
University of Leeds
School of Chemistry
Leeds LS2 9JT
UK
Paul M. Rose
University of Leeds
School of Chemistry
Leeds LS2 9JT
UK
Katherine Scovell
University of Nottingham
Department of Chemistry
Nottingham NG7 2RD
UK
James M. Tanko
Virginia Polytechnic Institute and State University
Department of Chemistry
Blacksburg, VA 24061
USA
Nils Theyssen
Max-Planck-Institut für Kohlenforschung
Kaiser-Wilhelm-Platz 1
45470 Mülheim
Germany
G. Herbert Vogel
Technische Universität Darmstadt
Ernst-Berl-Institut für Technische und Makromolekulare Chemie
Technische Chemie I
Petersenstrasse 20
64287 Darmstadt
Germany