Nuclear Magnetic Resonance in Modern Technology

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Series C: Mathematical and Physical Sciences - Vol. 447

Nuclear Magnetic Resonance in Modern Technology edited by

Gary E. Maciel Department of Chemistry, Colorado State University, Fort COllins, Colorado, U.S.A.

Springer-Science+Business Media, B.V.

Proceedings of the NATO Advanced Study Institute on Nuclear Magnetic Resonance in Modern Technology Sarigerme Park (Dalaman), Turkey August 16 - September 4, 1992

A C.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-94-010-4325-0 ISBN 978-94-011-0756-3 (eBook) DOI 10.1007/978-94-011-0756-3

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TABLE OF CONTENTS

Preface vii

Introduction G. E. Maciel ix

Chapter 1. Introduction to NMR and Modern Technology E.W. Randall 1

Chapter 2. Foundations and Strategies of Multidimensional NMR R. Freeman 23

Chapter 3. Applications of High-Resolution NMR to Soluble Polymers A. Zambelli, A. Proto and L. Oliva 57

Chapter 4. High Resolution NMR: Applications to Biological Systems L.W. Jelinski 73

Chapter 5. Line Broadening in Solids R. Dupffie 87

Chapter 6. Basic Cross Polarization Magic Angle Spinning C.S. Yannoni 105

Chapter 7. NMR Studies of Solid Polymers and Resins: An Introduction G.R. Hatfield 127

Chapter 8. NMR Characterization of Solid Fossil Fuels. Coal and Oil Shale G.E. Maciel and O. Erbatur 165

Chapter 9. NMR in Industrial Process Control and Quality Control G.E. Maciel 225

Chapter 10. Solid State NMR Investigation of Zeolites and Related Materials C.A. Fyfe and G.T. Kokotailo 277

VI

Chapter 11. NMR Study of Glasses ad Ceramics R. Dupree 339

Chapter 12. Averaging Effects in NMR J.S. Waugh 359

Chapter 13. NMR in the Study of Surfaces; 1 H CRAMPS and 29Si CP-MAS Studies of Silica G.E. Maciel 401

Chapter 14. Cross-Polarization Processes Involving Less Common Pairs of Nuclei C.A. Fyfe, K.T. Mueller and K.C. Wong-Moon 447

Chapter 15. NMR of Polymer Composites and Blends W.S. Vee man 483

Chapter 16. Applications of NMR Spectroscopy to Surfaces and Catalysts: Acidic Sites and Adsorbed Species H. Pfeifer 499

Chapter 17. Introduction to DOR NMR A. Samoson 525

Chapter 18. NMR Imaging: Introduction and Survey L.W. Jelinski 547

Chapter 19. High Resolution NMR Imaging of Solids W.S. Veeman 563

Index 593

PREFACE

This volume represents the primary lectures of the NATO

Advanced Study Institute (ASI) on "Nuclear Magnetic Resonance in

Modern Technology," which was held at Sarigerme Park (near the

Dalaman Airport) on the southern Aegean shore of Turkey from

August 23 to September 4, 1992. As indicated in the title, this ASI

was aimed at examining, displaying, and perhaps influencing, the

role of nuclear magnetic resonance (NMR) in modern technological

activity. The lectures summarized in this volume and the numerous

short contributed talks and posters were primarily aimed at the

question, "What is NMR doing in support of modern technology?"

During the main discussion periods and the numerous small

scheduled meetings of specific interest groups this same topic was

also addressed, along with questions like, "What could or should NMR

be doing in support of modern technology?" With this kind of subject

orientation, the organizers attempted to include a large

participation at the ASI from scientists and engineers from diverse

private industries in which NMR does, or perhaps should, play a

substantial role in supporting or optimizing technology. Perhaps

because of a combination of worldwide industrial contractions and

residual corporate nervousness regarding the then recent Gulf War

(which caused a one-year postponement of this ASI), the

participation from private industry was numerically disappointing.

We hope that this book will serve to bring the role of NMR in modern

industry to the attention of numerous industrial scientists and

engineers who were unable to attend the AS!. vii

viii

For the success of the ASI, we are grateful to many people.

This certainly includes the lecturers for providing excellent

lectures, notes and ultimately chapters, the students and other

participants for the stimulation that they

provided, and Dr. Oktay Erbatur and Dr. Gaye Erbatur and their

assistants, who handled all of the local arrangements in Turkey. The

AS! arrangements and the site were outstanding, and the Turkish

hospitality was superb. Of course, we are grateful to NATO for the

basic grant that made possible the AS! on "Nuclear Magnetic

Resonance in Modern Technology." We also thank the U.S. National

Science Foundation for travel grants to graduate students, the U.S.

Naval Research European Office for co-sponsoring this AS! with a

substantial grant, and the following private companies (listed in

alphabetical order), whose financial contributions substantially

enhanced the quality of the ASI in all respects: BP International,

Doty SCientific, DSM Research, IBM, Nabisco Brands, Otsuka­

Chemagnetics, Unilever, Union Carbide, and W. R. Grace. I also wish

to thank Cheryl Tyler, Barbara Wilson and Vicky Pan for their help in

preparing the final manuscript.

Gary E. Maciel,

Fort Collins, Colorado, USA

INTRODUCTION

GARY E. MACIEL Department of Chemistry Colorado State University

Fort Collins, CO 80523 USA

This book covers a variety of very fundamental topics in

chemistry and physics, in most cases with the aim of preparing the

reader to understand technological applications of NMR that are

described in this volume or elsewhere. With a publication date that

comes at approximately the fiftieth anniversary of the discovery of

NMR,' this book is timely, in the sense of providing an excellent

view of the substantial role that this maturing, yet dynamic

phenomenon/technique is having in modern technology.

The level of most of the coverage in this volume is

approximately that which would be appropriate for a graduate

chemistry student with an elementary introduction in the following

basic principles of NMR:

1. The NMR spectrum (Fig. 1 B) of a sample is its frequency

response, due to nuclear spin transitions (Fig. 1 A), induced by a

radiofrequency (rf) radiation field (B 1) in the presence of a static

magnetic field (80 ). 2 In "high resolution" experiments the spectrum

is typically dominated by the chemical shift, a measure of the

shielding (0) of a nucleus from the unadulterated effect of the

applied static field Bappl due to the local field generated by

circulations of electrons induced by Bappl(Bo = BapPI(l- 0) ); and by

"indirect" (J) coupling between nuclei in a molecule, reflecting the

interaction between spins mediated (communicated) by the bonding

electrons involved with the coupled nuclei. 3

ix

x

A

yh ~E =-2 B = hu

1t 0

hu

J

B ~

J J ( )( )

G(m)

1 ~ , I f-ro roa Ib roC 0 COo 0

Figure 1. The NMR spectrum as a frequency response for transitions of a spin-1/2 system in a magnetic field, Bo' A) Energy levels and transitions, where Bo is the field experienced by the spins as a result of a large static applied field, Bappl ' B) Frequency response NMR spectrum, showing three different chemical environments with chemical shifts 0a' 0b' 0c (corresponding to shieldings O"a' O"b and o"c'

respectively, and resonance frequencies (J)~ (J)~ and (J)~), and J coupling between the spins of environments band' c with a pattern that is characteristic of protons in a ~C HC -CH% moiety.

Xl

2. In modern Fourier transform (FT) NMR experiments,4 as first

demonstrated by Ernst and Anderson,5 the frequency-response

spectrum G(m) is obtained by Fourier transformation of the time­

response get) of the voltage induced in the rf coil by the transverse

(x-y) magnetization following a pulse of rf energy at or near the

resonance frequency (Figure 2).

x

A z

, \ ,

------~~----~' y

rf coil

B

get)

t-+-

Fourier) transform

G(m)

Figure 2. The basis of Fourier transform (FT) NMR. A) The effect of a 90° pulse of rf energy on the magnetization vector Mo' showing the decay of transverse (x-y) magnetization (with a time constant T 2) and re-establishment of longitudinal (z) magnetization (with a time constant T 1 ). 8) Fourier transformation of the time-response (oscillatory decay), get), due to the x component of magnetization, generating the frequency response spectrum, G(m). This figure shows the simple case of one chemical shift and no J couplings.

xii

3. Following a 900 rf pulse (as depicted in Fig. 2), the z

component of the macroscopic magnetization returns exponentially

to its thermodynamic equilibrium value Mo with a time constant T,

(the so-called spin lattice relaxation time), while the transverse

(xy) component of magnetization decays exponentially to zero, with

a time constant T 2 (the transverse or spin-spin relaxation time) in

the absence of inhomogeneous effects (such as a non-uniform

magnetic field).4

4. A useful concept in NMR is the "rotating frame," a cartesian

axis system (x', y', z') that rotates about its z axis (z'), which is

colinear with Bo ' at the oscillation frequency u of the rf field,

B,(t) = 2iB 1cos21tut (which can be viewed as two counter-rotating

fields, B, and B~, one rotating clockwise and one counterclockwise

about the z' axis). One of these rotating fields (B,) is chosen to

define one axis of the rotating frame, as seen in Figure 3A. Figure

A Z=Z B Z=Z ,

Bo

-- -- - -- y y - - - - _y)(p = 21tVt = rot x' -- -y

x x

Figure 3. The rotating frame (x', y', z') in relation to the static laboratory frame (x, y, z). A) One rotating component (B,) of B, (t) defining the x' axis of the rotating frame. B) Precession of a magnetization vector following a 900 pulse (ending at t = 0) for the "on resonance" condition,-roo = ro = 21t u.

xiii

3B shows the precession, following a 900 pulse at t = 0, of a

magnetization vector with a resonance frequency roo exactly equal to

the rotating-frame frequency, roo = 21tV.

5. Following a 90° rf pulse (at or near resonance), if the rf field

B 1 is phase-shifted by 900 instead of being shut off (Figure 3B), the

vector B 1 becomes colinear with the net magnetization vector M,

with no torque exerted by B 1 on M (Figure 3C). In this so-called

"spin-lock" condition, the transverse (xy) component of

magnetization decays to zero exponentially with a time constant T 1 p

that is referred to as the rotating-frame spin-lattice relaxation

time (Figure 3D).4

A z' B

'" '" x' ~ ~ -pha;e shift x'

z' c

M x'

z'

8, ---",-,...,..,......--y'

M

Figure 4. A) At the end of a 900 pulse, the rf field B 1 is phase shifted by 900

• B) The "spin-lock" condition. C) Exponential decay of the transverse component of M and B 1 in the spin-lock condition, with a characteristic time constant T 1 p.

There are some sections of this book in which additional

theoretical background is required. This is especially true in

Chapters 1 2 and 1 7. However, most of the coverage has been built up

from the kind of background represented by Figures 1 , 2, 3 and 4.

xiv

After Randall's general overview of the history of NMR in

technological applications (Chapter 1), Freeman presents an

introduction (Chapter 2) to multidimensional NMR, with applications

to high-resolution experiments on liquid samples. This is followed

by a chapter describing the application of high-resolution NMR

techniques in the characterization of soluble polymers (Chapter 3),

by Zambelli, Proto and Oliva, and by Jelinski's chapter on high­

resolution NMR applications to some biological systems (Chapter 4).

The next two chapters in the book, by Dupree (Chapter 5) and

Yannoni (Chapter 6), lay the fundamental groundwork on interactions

and techniques for solid-state NMR applications. This is followed by

Hatfield's chapter on the characterization of solid polymers (Chapter

7) and a chapter by Maciel and Erbatur on the characterization of

solid fossil fuels, mainly coal (Chapter 8). A chapter by Maciel on

NMR in industrial process control and quality control applications

(Chapter 9) draws on both liquid-sample and solid-sample NMR

characteristics and explores time-domain (mainly relaxation)

strategies in some detail. Chapters by Fyfe and Kokotailo (Chapter

10) on NMR investigations of zeolite-type materials and by Dupree

on NMR studies of ceramics and glasses (Chapter 11) complete the

initial survey of solid-state NMR applications in industry.

Waugh's chapter on averaging effects in NMR (Chapter 12)

begins a series of chapters that are concerned primarily with more

advanced topics in solid-state NMR. This series includes a chapter

by Maciel on NMR studies of silica surfaces (Chapter 13), a chapter

by Fyfe, Mueller and Wong-Moon on cross polarization among

uncommon pairs of nuclei (Chapter 14), a chapter by Veeman on NMR

xv

studies of polymer composites and blends (Chapter 15), a chapter by

Pfeifer on NMR studies of surfaces, especially acidic catalytic

surfaces (Chapter 16), and a chapter on double-rotation (DOR)

experiments for quadrupolar nuclei (Chapter 17) by Samoson.

The final two chapters of this volume are devoted to NMR

imaging. Jelinski's chapter provides an introduction and overview of

the subject (Chapter 18), and Veeman's chapter focuses on high­

resolution NMR imaging techniques for solids (Chapter 19).

The array of primary lectures represented by these chapters

provides an extensive overview of the basic principles and use of

NMR in modern technological applications, especially for solid

samples. At the ASI, these lectures were supplemented by some

excellent contributed talks and posters, and stimulating discussions

with an excellent group of students and participants.

References

1. F. Bloch, W. W. Hansen and M. Packard, Phys. Rev., 70, 474 (1946).

2. J. A. Pople, W. G. Schneider and H. J. Bernstein, "High-resolution Nuclear Magnetic Resonance," McGraw Hill, New York, 1959.

3. E. D. Becker, "High Resolution NMR: Theory and Chemical Applications," 2nd edition, Academic Press, New York, 1980.

4. T. C. Farrar and E. W. Becker, "Pulse and Fourier Transform NMR. Introduction to Theory and Methods," Academic Press, New York, 1971.

5. R. R. Ernst and W. A. Anderson, Rev. Sci. Instrum., 37, 93 (1966).