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Chemical Micro-Process Engineering. Fundamentals Modelling and Reactions

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Angewandte
Books
Chemie
Chemical Micro-Process
Engineering
Fundamentals,
Modelling and
Reactions. By Volker
Hessel, Steffen
Hardt and Holger
Lwe. Wiley-VCH,
Weinheim 2004.
674 pp., hardcover
E 189.00.—ISBN
3–527–30741–9
Anyone familiar with the field of microdevices applied to chemistry may at first
think about this new book as the second
edition of the earlier book entitled
Microreactors which was published in
2000. However, although two of the
three authors were involved in the earlier book, the present book is definitely
a completely new one. With almost 700
pages, it provides a detailed picture of
the field of microstructured devices for
chemistry. However, the title is a little
puzzling. It invites comparison with textbooks dealing with (macro)-chemical
process engineering, and also raises
many questions. To what extent do the
fundamentals of mass and heat transfer,
fluid dynamics, and other elementary
processes involved in chemical processing change on going from chemical process engineering to chemical microprocess engineering? How are scale-up
issues to be dealt with? How small
should the channels or other structural
components of a reactor be, for it to be
considered under this title? What are
the design rules associated with this
new technology? ..
The book is organized in only (!)
five chapters of about 130 pages each,
except for the last one with only 80
Angew. Chem. Int. Ed. 2004, 43, 6583 – 6585
pages. The book could have been presented in two volumes, the first containing Chapters 1 and 2, which deal with
more fundamental issues, and the
second grouping together the last three
chapters, which are concerned with applications. Microfabrication techniques are
not covered, since those were addressed
in the first book published in 2000.
The first chapter deals with the analysis of chemical microprocess technology. It is a kind of “pot-pourri”, which
covers many aspects related to microsystems: from process intensification to the
impact on society, and to ecology and
social acceptance. It also includes the
impacts on chemical engineering,
micro-TAS (total analysis systems),
mixing, scale-up and scale-out issues,
green chemistry, a comprehensive
review of on-going research programmes devoted to microsystems for
chemistry around the world, and even
a survey of publications in the nonscientific literature. Two points could have
deserved more attention. First, the
examples only describe the uses of
microstructured reactors, but none deal
with other unit operations such as separation (filtration, decantation, etc).
Second, only very little space (8 pages)
is devoted to fundamental universal
principles, and this concerns only fluidsolid reactors and is based on only one
reference. However, this chapter is an
impressive performance in view of the
enormous amount and diversity of information collected.
Chapter 2 provides tools for the
modeling of microdevices, either microreactors or micromixers. A large part of
this chapter is devoted to an introduction to modeling techniques, such as
computational fluid dynamics (CFD).
Although it is not specific to microdevices, this chapter will certainly be appreciated by readers not familiar with reactor modeling. Only one page is devoted
to the modeling of the coupling of mass
and heat transfer with catalytic reactions
in porous media. This is very little in
view of the large number of applications
of microstructured reactors with solid
catalysts. However, phenomena that
can prevail in microfluidics, such as wetting, nanoflows, boundary slip, and surface-roughness effects are addressed.
The third chapter presents a review
of gas-solid catalytic reactions and reacwww.angewandte.org
tors. This is an area where microstructured reactors have been shown to give
clear advantages, because of their interesting mass- and heat-transfer properties and the ability to precisely control
residence time distributions. The first
half of the chapter describes, with
many examples, photographs, schemes,
and—last but not least—metrics, the different arrangements of microstructured
elements to obtain the desired flow pattern, pressure drop, mass or heat
exchange capabilities, etc. In the
second part, as many as 14 oxidation
processes, 4 hydrogenations, 3 dehydrogenations, and others (eliminations,
additions, oxidative coupling) are carefully reviewed. For each reaction, the
motives for and benefits from performing the process in microstructured reactors, as well as typical results, are provided.
Chapter 4, devoted to liquid and
liquid–liquid reactions, is organized in
the same way as Chapter 3. Thus, microreactors are described first, followed by
applications. Very simple “microreactors”, such as capillary HPLC columns,
tubing, or porous-polymer rods that do
not require sophisticated microfabrication techniques but still provide micrometer dimensions, can be used effectively. With liquids, and by using more
advanced microfabrications, the technique of electroosmotic flow is introduced, as well as photo- and electrochemical microreactors, and coupled
systems consisting of a micro-heatexchanger and a microreactor. Chemists
engaged in organic synthesis will enjoy
this chapter, where many reactions are
described. These include aliphatic and
aromatic nucleophilic and electrophilic
substitutions, catalytic transformations
(e.g., Suzuki and Sonogashira couplings), free-radical substitutions, additions (epoxidations, cycloaddition),
eliminations, rearrangements, oxidations (catalyzed, electro-, or photo-promoted) and some inorganic reactions,
just to name a few. Interesting examples
of industrial applications of microreactors, e.g., nitrations, production of azo
pigments and polyacrylates, and
Grignard addition to carbonyls are also
described.
The last chapter reports on gas–
liquid reactions. Mixing or contacting a
gas and a liquid in a microvolume,
- 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6583
Books
while still ensuring a large interfacial
area for mass transfer and a well-controlled flow, is not an easy task, because
of the capillary forces that dominate in
microstructures. Film contactors, dispersive mixing, and even trickling flow have
been used. In analogy to Chapters 3
and 4, the first part describes gas–
liquid microreactors, while applications
are detailed in a second section which
encompasses fluorination of aromatics
and aliphatics, hydrogenations of nitro
derivatives and of carbon–carbon
double bonds, oxidations of alcohols,
etc.
This book is a must for anyone interested in the application of microdevices
to chemistry, and is of interest for chemists seeking new reactions, new conditions, and new catalysts, as well as for
chemical engineers interested in process
intensification. Again, one may complain about the lack of universal principles leading to “ready-to-use” design
rules. These are not yet available,
because a more basic understanding of
microstructured components is lacking,
despite many ongoing research programs. However, because of its highly
informative contents with many references, analyses of literature data, and critical evaluations of existing microsystems, this book is a true handbook of
microdevices applied to chemistry,
from which readers can derive valuable
information for their own work.
Claude de Bellefon
Laboratoire de G4nie des Proc4d4s
Catalytiques
CNRS ESCPE Lyon
Villeurbanne (France)
DOI: 10.1002/anie.200485187
6584
Biocatalysis
By Andreas S. Bommarius and Bettina R. Riebel. WileyVCH, Weinheim
2004. 611 pp.,
hardcover
E 129.00.—ISBN
3–527–30344–8
Enzymes have been used in biocatalysis
for more than a century; however, their
use received a tremendous boost in the
past few decades, mostly as a consequence of developments in enzyme discovery, molecular biology, and protein
design. Biocatalysts are used in a variety
of areas, including laundry detergents,
paper and pulp processing, food production, and organic synthesis. In the latter
area, they are especially employed for
the synthesis of optically pure compounds for pharmaceutical and agricultural applications.
To use biocatalysts efficiently and
competitively, one needs knowledge
about their availability, catalytic function, production, and the design of processes. This, in turn, needs expertise in
such diverse areas as microbiology,
molecular biology, fermentation technology, computer modeling, analytical
methods, organic chemistry, and reaction engineering. Usually, one can only
find textbooks that cover one or just a
few of these fields in sufficient depth,
while the other areas are hardly touched
on.
Bommarius and Riebel have now
succeeded in writing a book that covers
all of these different areas and aspects
that are important to biocatalysis. Certainly the major challenge was to condense and distil the vast amount of information in this area. This has resulted in
an excellent work of a little over 600
pages.
The book is divided into three major
parts, with a total of 20 chapters. Several
of these deal with basic fields and tools
(introduction, characterization, isolation and preparation, molecular biology
methods, enzyme reaction engineering).
In addition, rather advanced areas of
enzyme manufacture, protein character-
- 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
ization, protein engineering—including
rational protein design and directed
evolution—and reactions in unconventional media are covered. Some of
these chapters deal with methods that
should already be well-known to an
undergraduate student. On the other
hand, bearing in mind the interdisciplinary nature of biocatalysis, some areas
such as molecular biology methods
might not be familiar to a chemist or
an engineer, whereas the fine chemistry
background might be rather new to a
biologist. I consider the broad coverage
of methods from different areas to be
rather useful, and certainly not superfluous. Several chapters deal with applications of enzymes: their use as additives
(in detergents, textiles, pulp and paper,
animal feed) or as true catalysts in the
production of basic, fine, and bulk
chemicals. A positive feature is that the
content is not restricted to the use of
single enzymes (an area that is commonly regarded as clearly defining “Biocatalysis” as distinct from “Biotransformation”, which rather involves wholecell systems, and often more than one
enzyme, in the production process).
Thus, the chapters also include examples
of the latter type, such as the production
of 1,3-propandiol or indigo using engineered E. coli cells. Some rather new
trends, such as systems biology and the
impact of bioinformatics on the discovery, evolution, and design of biocatalysts, are also addressed.
In view of the strong background of
Andy Bommarius in the fine chemicals
industry (he worked at Degussa AG,
Germany, for more than a decade), it is
not surprising that the book includes a
critical comparison of biocatalysis with
chemical methods, in which the two
competing approaches are evaluated in
detail. The design of biocatalytic processes is discussed for a range of examples, such as the production of high-fructose corn syrup and the synthesis of
enantiomerically pure l-amino acids
and chiral alcohols. In addition to the
broad and in-depth coverage of many
topics, further positive aspects of the
book are the summaries at the beginning
of each chapter, and the inclusion of a
wide variety of up-to-date examples
from various biocatalytic processes,
with many details and related background information. Rather disappointAngew. Chem. Int. Ed. 2004, 43, 6583 – 6585
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