Nanoporous materials : science and engineering

917 Pages·2004·43.771 MB·English

by  G Q Lu, (Professor), X S Zhao

N a n o p o r o us
M a t e r i a ls
S c i e n ce a nd E n g i n e e r i ng
edited by
G. Q. Lu
University of Queensland, Australia
X. S. Z h ao
National University of Singapore, Singapore
Imperial College Press
Published by
Imperial College Press
57 Shelton Street
Covent Garden
London WC2H 9HE
Distributed by
World Scientific Publishing Co. Pte. Ltd.
5 Toh Tuck Link, Singapore 596224
USA office: 27 Warren Street, Suite 401^02, Hackensack, NJ 07601
UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
NANOPOROUS MATERIALS: SCIENCE AND ENGINEERING
Series on Chemical Engineering
Copyright © 2004 by Imperial College Press
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or
mechanical, including photocopying, recording or any information storage and retrieval system now known or to
be invented, without written permission from the Publisher.
For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center,
Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from
the publisher.
ISBN 1-86094-210-5
ISBN 1-86094-211-3 (pbk)
Editor: Tjan Kwang Wei
Printed in Singapore by World Scientific Printers (S) Pte Ltd
Preface
In the last decade, we have witnessed a rapid growth in research and
development of nanotechnology, especially nanostructured materials.
Nanoporous materials as an important class of nanostructured materials
possess high specific surface area, large pore volume, uniform pore size,
and rich surface chemistry. These materials present great promises and
opportunities for a new generation of functional materials with improved
and tailorable properties for applications in adsorption, membranes,
sensors, energy storage, catalysis and photocatalysis, and biotechnology,
etc.
Interest in making materials from nanoscale building blocks arose from
discoveries that by controlling the size in the range of 1-100 nm and the
assembly of such constituents, one could alter and prescribe the properties
of the assembled nanostructures. Nanoscale phenomena and objects have
been around for some time. Catalysts, for example, are mostly nanoscale
particles, and catalysis is a nanoscale phenomenon. What is new and
different now is the degree of understanding and deliberate control and
precision that the new nanoscale techniques afford. Instead of discovering
new materials by random search (trial-and-error), we can now design them
systematically. Nanoporous materials can have long-range structural order
or disordered structure and contain pores of the dimension of a few
nanometers to tens of nanometers. Some applications such as catalysis
take advantage of high surface area and pore confinement effects.
Synthesis and processing of nanoporous materials with controllable
structures and properties require new approaches such as molecular
templating and intercalation in a bottom-up manner.
From a practical standpoint, a large specific surface for nanoparticles is
most desired for catalysis. However, fine powder catalysts can cause
serious operational problems such as agglomeration, difficulties in
loading, pressure drop, and separation of catalyst from the reaction
products. A feasible approach to generating a large and accessible surface
area of catalyst but avoiding the morphology of fine powder is to create a
composite or immobilized structure. One can disperse nanoparticles of
metals or oxides in an inorganic support to stabilize the discrete
nanoparticles, meanwhile maintaining most of their surface accessible to
reactant molecules. However, the conventional methods of preparing the
catalysts such as impregnation often result in agglomerated catalyst
particles in the support, thus decreasing the active surface area, and
uniformity of the active centers. With nanostructuring techniques, active
metal or oxide precursors can be incorporated or grafted on the
nanoporous support during synthesis thus not only increase the control in
catalyst particle size, surface area and dispersion, but also eliminating the
cost and problems associated with impregnation.
Since the early 1990s, a large number of microporous and mesoporous
materials have found wide applications in catalysis. Major breakthroughs
in materials synthesis such as the templated synthesis of mesoporous
molecular sieves M41S and porous clay heterostructures have opened
exciting avenues for designing new classes of nanoporous materials based
on molecular templating and self-assembly principle (with pore
dimensions between 1 to 10 nm). These materials offer great potential for
applications in separation and catalysis, particularly reactions involving
large and bulky molecules. We are excited at the prospect of an explosion
of revolutionary discoveries at nanoscale. The new millennium presents
opportunities as well as challenges to scientists and engineers working in
this dynamic field of nanoporous materials in terms of the tailor-design,
synthesis and characterization for specific functionalities and applications.
The main objectives of this book are to provide the readers with an
overview of the field of nanoporous materials and to present the latest
advances in various areas from synthesis, characterization, surface
modification to adsorption and separation processes, and biological and
catalytic applications. Fundamentally, this book contains chapters dealing
with important issues in synthesis of nanoporous materials of various
compositions, characterization techniques, surface modification/
functionalization, catalyst design and nanostructure tailoring, and
adsorption/separation application including bioseparation. This book
presents 28 comprehensive chapters reviewing the state of the art in the
field of nanoporous materials contributed by some of the finest scientists
in the world in this field.
With an overview of nanoporous materials in chapter 1, chapters 2-10
describe some general strategies for the synthesis of nanoporous materials
such as the nonionic block copolymer template method, the synthesis of
composite materials with a zeolite framework, preparation of hydrophobic
membranes using sol-gel technique, macroporous materials templated by
colloidal crystals, and carbon nanotubes. The advances in characterization
of nanoporous materials by physical adsorption in combination with
simulation, and modification and functionalization of nanoporous
materials are covered in chapters 11-16. In addition to traditional pore
evaluation methods such as the BJH method based on Kelvin equation for
pore size determination, the development of microscopic methods, such as
the non-local-density functional theory (NLDFT) or computer simulation
methods (e.g. monte-carlo and molecular-dynamic simulations), which
allow the description of the configuration of adsorbed molecules in pores
on a molecular level (elaborated in chapters 11 and 12). Surface
functionalization of nanoporous materials by grafting, co-condensation
routes, and molecularly designed dispersion methods, surface alumination
to alter acidity, as well as measurement of surface acidity can be found in
chapters 13-16. Recent developments in the catalytic applications of
nanoporous materials, ranging from acidic catalysis to base catalysis, from
shape-selective catalysis to environmentally friendly catalysis, are
presented in chapters 17-21. Adsorption- and separation processes
involving nanoporous materials are subjects of chapters 22-28.
Nanoporous materials for the removal of pollutants in gas or liquid phase
are elaborated. Separation and immobilization of enzymes are reviewed in
chapters 26 and 27.
We would like to thank the authors of the chapters for their valuable and
timely contributions, and for their patience and cooperation in the editing
process. We hope that this book would be a useful reference for senior
students, graduate students and researchers in materials chemistry,
physical and colloid chemistry, chemical engineering, materials science,
biotechnology and nanotechnology.
Finally, we would like to express our sincere thanks to Professor Ralph T
Yang, University of Michigan, the Series Editor of Chemical Engineering
for Imperial College Press for his kind invitation to contribute this volume.
We would also like to thank the Editor in Imperial College Press, Tjan
Kwang Wei for his great assistance. We are very grateful to Sharon
Mathiesen for her wonderful help with manuscript management and
editing. Last but not the least, to our respective families for their love,
understanding and support in this endeavor.
G.Q (Max ) Lu George X S Zhao
Brisbane, Australia Singapore
November, 2003
Contents
Preface ........................................................................................ v
1. Nanoporous Materials-an Overview .................................. 1
1.1 Introduction ........................................................................ 1
1.2 Classification of Nanoporous Materials ............................. 4
1.3 Properties and Characterization of Nanoporous
Materials ............................................................................ 5
1.4 Major Opportunities in Applications ................................... 6
1.5 Concluding Remarks ......................................................... 11
References .................................................................................... 13
2. Advances in Mesoporous Materials Templated by
Nonionic Block Copolymers .............................................. 14
2.1 Introduction ........................................................................ 14
2.2 Siliceous Mesoporous Materials ........................................ 16
2.3 Wall Structures of Mesoporous Materials Templated by
Amphiphilic Block Copolymers .......................................... 22
2.4 Morphology of Mesoporous Materials Templated by
Block Copolymers .............................................................. 24
2.5 Non-siliceous Structures .................................................... 28
2.6 Applications ....................................................................... 33
2.7 Conclusion Remarks .......................................................... 38
2.8 Acknowledgements ............................................................ 38
References .................................................................................... 39
3. Zeolite/Mesoporous Molecular Sieve Composite
Materials .............................................................................. 47
3.1 Introduction ........................................................................ 47
3.2 Mechanisms of Zeolite Germination .................................. 48
ix
This page has been reformatted by Knovel to provide easier navigation.
x Contents
3.3 Synthesis Strategies for Zeolite/MMS Composites ............ 51
3.4 Catalytic Properties ............................................................ 84
3.5 Future Challenges ............................................................. 90
3.6 Conclusion ......................................................................... 93
3.7 Acknowledgements ............................................................ 93
References .................................................................................... 93
4. Chromium-containing Ordered Nanoporous Materials .... 101
4.1 Introduction ........................................................................ 101
4.2 Materials and Methods ...................................................... 103
4.3 Results and Discussion ..................................................... 106
4.4 Conclusion ......................................................................... 118
4.5 Acknowledgements ............................................................ 119
References .................................................................................... 119
5. Surfactant-templated Mesostructured Materials:
Synthesis and Compositional Control .............................. 125
5.1 Introduction ........................................................................ 125
5.2 Synthesis Routes ............................................................... 126
5.3 Compositions of Mesostructured and Mesoporous
Materials ............................................................................ 140
5.4 Conclusions and Outlook ................................................... 151
5.5 Acknowledgments .............................................................. 152
References .................................................................................... 152
6. Organic Host-guest Structures in the Solid State ............ 165
6.1 Introduction ........................................................................ 166
6.2 Host Design Principles ....................................................... 168
6.3 C Symmetry and Halogen...Halogen Interaction in
3
Host Design ....................................................................... 170
6.4 Wheel-axle Host Lattice ..................................................... 177
6.5 Design of Layered Host: Crystal Engineering .................... 179
6.6 Gas Storage in Interstitial Voids ........................................ 182
6.7 Guest Selectivity in Inclusion ............................................. 184
This page has been reformatted by Knovel to provide easier navigation.
Contents xi
6.8 Conclusions ....................................................................... 185
6.9 Acknowledgement ............................................................. 185
References .................................................................................... 185
7. Nonsurfactant Route to Nanoporous Phenyl-modified
Hybrid Silica Materials ....................................................... 188
7.1 Introduction ........................................................................ 188
7.2 Methods ............................................................................. 191
7.3 Results and Discussion ..................................................... 192
7.4 Conclusions ....................................................................... 202
7.5 Acknowledgements ............................................................ 202
References ................................................................................... 202
8. 3D Macroporous Photonic Materials Templated by
Self Assembled Colloidal Spheres .................................... 206
8.1 Introduction ........................................................................ 206
8.2 A Survey of Photonic Bandgap .......................................... 207
8.3 Nanolithography for Photonic Crystals .............................. 211
8.4 Self-assembly Approaches to 3D Photonic Crystals ......... 212
8.5 Fabrication of Intentional Defects in 3D Photonic
Crystals .............................................................................. 226
8.6 Acknowledgements ............................................................ 228
References .................................................................................... 228
9. Hydrophobic Microporous Silica Membranes for Gas
Separation and Membrane Reactors ................................. 237
9.1 Introduction ........................................................................ 237
9.2 Inorganic Membranes ........................................................ 238
9.3 Hydrothermal Stability and Hydrophobicity-key Areas of
Improvement ...................................................................... 243
9.4 Membrane Reactors .......................................................... 251
9.5 Perspective and Concluding Remarks ............................... 256
9.6 Acknowledgement ............................................................. 257
References .................................................................................... 257
This page has been reformatted by Knovel to provide easier navigation.
xii Contents
10. Synthesis and Characterization of Carbon Nanotubes
for Hydrogen Storage ......................................................... 263
10.1 Introduction ........................................................................ 264
10.2 Construction, Structure and Unique Properties of
Carbon Nanotubes ............................................................. 266
10.3 Synthesis of Carbon Nanotubes ........................................ 271
10.4 Surface and Pore Structure of Carbon Nanotubes ............ 279
10.5 Experimental Investigations on Hydrogen Uptake in
Carbon Nanotubes ............................................................. 286
10.6 Theoretical Predictions and Simulations of Hydrogen
Uptake in Carbon Nanotubes ............................................ 295
10.7 Possible Hydrogen Adsorption Sites in Carbon
Nanotubes ......................................................................... 303
10.8 Future Research Topics and Remarks .............................. 308
10.9 Acknowledgement ............................................................. 309
References .................................................................................... 309
11. Physical Adsorption Characterization of Ordered and
Amorphous Mesoporous Materials ................................... 317
11.1 Introduction ........................................................................ 317
11.2 Surface and Pore Size Analysis by Physisorption:
General Aspects ................................................................ 322
11.3 Pore Condensation and Adsorption Hysteresis ................. 328
11.4 Pore Size Analysis of Mesoporous Solids ......................... 345
11.5 Concluding Remarks ......................................................... 355
11.6 Acknowledgements ............................................................ 356
11.7 References ........................................................................ 356
12. Molecular Simulation of Adsorption in Porous
Materials .............................................................................. 365
12.1 Introduction ........................................................................ 366
12.2 Simulation Techniques ...................................................... 366
12.3 Thermodynamics ............................................................... 369
12.4 Adsorption in Spaces with Simple Geometries .................. 372
12.5 Adsorption Heterogeneity .................................................. 380
This page has been reformatted by Knovel to provide easier navigation.