In-situ spectroscopy in heterogeneous catalysis

281 Pages·2002·29.677 MB·English

by  James F Haw

James F. Haw
In-Situ Spectroscopy
in Heterogeneous Catalysis
In-Situ Spectroscopy in Heterogeneous Catalysis. By James F. Haw
Copyright O 2002 Wiley-VCH Verlag GmbH & Co. KGaA
ISBN: 3-527-30248-4
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l n-S it u Spectroscopy
in Heterogeneous Catalysis
Edited by
James F. Haw
^WILEY-VCH
Editor This book was carefully produced.
Nevertheless, editor, authors and publisher do
Prof. Dr. James F. Haw not warrant the information contained therein to
Loker Hydrocarbon Research Institute be free of errors. Readers are advised to keep in
and Department of Chemistry mind that statements, data, illustrations,
University of Southern California procedural details or other items may
University Park inadvertently be inaccurate.
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© Wiley VCH Verlag GmbH, Weinheim, 2002
Printed on acid-free paper.
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in other languages). No part of this book may be
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Composition pagina media gmbh, Hemsbach
Printing Strauss Offsetdruck, Mörlenbach
Cover Shown on the cover is the ^f"8 Großbuchbinderei J. Schäffer
methanol-to-olefm catalyst HSAPO-34 GmbH & C°' KG' Grunstadt
containing reactants, intermediates,
products, and a deactivating species, lbbN
pyrene.
The image is deliberately blurred for
artistic effect but also to suggest that the
mechanism is just coming into focus
through in situ studies.
VII
Contents
1 Overview of In Situ Methods in Catalysis I
1.1 Introduction I
1.2 Catalytic Materials 2
1.3 Compromises 4
1.3.1 Reactor Design 5
1.3.2 Catalyst Composition and Feed 7
1.3.3 Temperature 8
1.3.4 Theoretical Calculations - A Promising Future 9
1.4 Spectators 10
1.5 Future Prospects for In Situ Studies of Catalysis 10
1.6 My Introduction to In Situ Studies of Catalysis 11
2 In Situ Catalysis and Surface Science Methods 15
2.1 Introduction 15
2.2 Surface Science Tools 16
2.2.1 Sum Frequency Generation (SFG)-surface specific vibrational
spectroscopy 17
2.2.2 The high-pressure high-temperature Scanning Tunneling
Microscope (STM) 19
2.3 Applications of In Situ Methods in Surface Science to Catalysis 20
2.3.1 High-Pressure SFG Studies 20
2.3.1.1 Ethylene hydrogenation on Pt(lll) 20
2.3.1.2 Propylene hydrogenation and dehydrogenation on Pt(lll) 26
2.3.1.3 Cyclohexene hydrogenation and dehydrogenation on Pt(lll) and
Pt(lOO) 31
2.3.1.4 CO oxidation on Pt(l 11) 36
2.3.2 High-Pressure STM Studies 42
2.3.2.1 High-pressure CO on Pt(lll) [33] 42
2.3.2.2 High-pressure NO on Rh(lll) 43
VMM Contents
2.3.2.3 Tip-induced catalysis [36-38] 46
Preparation of hydrocarbon clusters 46
Tip-catalyzed hydrogenation of hydrocarbon clusters 47
Tip-catalyzed oxidation of hydrocarbon clusters 50
2.4 Challenges and Future Directions 51
3 In Situ N M R 53
3.1 Introduction 53
3.2 Methods of In Situ NMR 55
3.2.1 General Considerations 55
3.2.2 In Situ NMR of Photocatalysis 56
3.2.3 In Situ NMR of Thermal Reactions in Sealed MAS Rotors 57
3.2.4 Sealed Rotors with Transient Heating 60
3.2.5 In Situ MAS Flow Probes 65
3.2.6 Magic-Angle Hopping Flow Probes 65
3.2.7 In Situ NMR using Quench Reactors 65
3.3 Applications of In Situ NMR to Methanol-to-Olefm Catalysis 70
3.3.1 Overview 70
3.3.2 HSAPO-34 Catalyst Structure 73
3.3.3 Pulse-Quench In Situ NMR of the Hydrocarbon Pool on
HSAPO-34 75
3.3.4 Correlation of Product Selectivity (GC) with Catalyst Structure
(NMR) 76
3.4 Some Limitations of In Situ NMR 78
4 Theoretical Catalysis: Methods, Applications, and Future
Directions 87
4.1 Introduction 87
4.2 Theoretical Methods 88
4.2.1 Classical Mechanics 88
4.2.1.1 Force fields 88
4.2.1.2 Classical mechanical techniques 90
Energy minimization 90
Monte Carlo simulation 91
Molecular dynamics simulation 91
4.2.1.3 Prediction of experimental data with classical mechanical
methods 93
4.2.2 Quantum Mechanics 93
4.2.2.1 S emiempirical methods 93
4.2.2.2 Ab initio methods 94
4.2.2.3 Density functional theory 96
4.2.2.4 Prediction of experimental data by quantum mechanical
methods 97
NMR properties 98
Contents IX
4.3 Model Systems 99
Our common quantum mechanical strategy 101
4.4 Applications of Theoretical Methods to Catalysis 101
4A.I Diffusion of Adsorbates in Silicalite 101
4.4.2 Theoretical Characterization of Zeolite Acidity 102
4.4.3 Solvent-Assisted Proton Transfer in Catalysis by Zeolite Solid
Acids 105
4.4.4 Activation of Br0nsted Acids by Lewis Acids: The Creation of New
Solid Acid Catalysts 107
4.4.5 Carbenium Ion Chemistry on Solid Acids: Theoretical NMR 108
4.4.6 Base Catalysis by Metal Oxide Surfaces 110
4.5 Future Developments in Computational Catalysis 112
4.5.1 Computing Power 112
4.5.2 Approvements in General Methodology 112
4.5.3 Plane-Wave DFT 112
4.5.4 Combinatorial Catalysis 113
5 In Situ Ultraviolet Raman Spectroscopy 121
5.1 Introduction 121
5.2 Instrumentation and Experimental Methods 124
5.2.1 The Spectrometer 124
5.2.2 The Fluidized Bed Sample Cell 125
5.2.3 Raman Tribometer 129
5.3 Two Examples of Results 130
5.3.1 Coke Formation in the Methanol-to-Gasoline Reaction 130
5.3.2 Lubricant Chemistry 133
5.4 Summary 137
6 In Situ Infrared Methods 139
6.1 Introduction 139
6.2 Experimental Aspects 140
6.2.1 In situ cells for transmission Spectroscopy 140
6.2.2 Diffuse Reflectance Spectroscopy 142
6.2.3 Infrared Emission Spectroscopy 143
6.2.4 Infrared Microspectroscopy 145
6.2.5 Reflection-Absorption Infrared Spectroscopy (RAIRS) 145
6.2.6 Sum Frequency Generation Spectroscopy (SFG) 146
6.2.7 Picosecond Infrared Spectroscopy 147
6.3 Recent Applications of in situ Infrared Spectroscopy 148
6.3.1 Zeolite Catalysts 148
6.3.1.1 Low-temperature bond migration in olefins 148
6.3.1.2 Methanol conversion over acid zeolites 151
6.3.1.3 Side-chain alkylation of toluene 156
6.3.1.4 Selective Catalytic Reduction (SCR) of NO 157
X
X Contents
6.3.2 Oxide Catalysts 159
6.3.2.1 S elective catalytic reduction of N O by ammonia over
vanadia/titania 159
6.3.2.2 In situ DRIFTS study of NO reduction by CH over LaO 162
4 2 3
6.3.2.3 Picosecond Infrared Spectroscopy on Single-Crystal Oxide
Surfaces 164
6.3.3 Supported Metal Catalysts 166
6.3.3.1 Alkane reactions over bifunctional zeolites 166
6.3.3.2 DRITS study of NO decomposition over carbon-supported Rh and
Pd 168
6.3.3.3 DRIFTS study of NO reduction by propene 168
X
6.3.4 Metal Surfaces 171
6.3.4.1 In situ RAIRS study of kinetic oscillations in the Pt(lOO) NO + CO
system 171
6.3.4.2 RAIRS studies of electrocatalysis 173
6.4 Conclusions and Future Prospects 175
7 In situ XAS Characterization of Heterogeneous Catalysts 179
7.1 Introduction: X-ray Absorption Spectroscopy (XAS) 179
7.2 Information Content of XAS 181
7.2.1 X-ray Absorption Near-Edge Spectrum (XANES) 181
7.2.1.1 Elemental analysis 181
7.2.1.2 Oxidation state and site symmetry 181
7.2.1.3 Empirical analysis of XANES 182
7.2.2 Extended X-ray Absorption Fine Structure (EXAFS) 183
7.3 Scope of Applicability of XAS 184
7.3.1 Applicability to Elements 184
7.3.1.1 Low-Z elements (C, N, O, and F) 185
7.3.1.2 Mg, AI, and Si 185
7.3.1.3 P, S,andCl 186
7.3.1.4 High-energy edges (Z > 21) 186
7.3.2 Accessible In Situ Conditions 186
7.4 Mechanics of Measurement 187
7.4.1 The XAS Spectrometer - The Beamline 188
7.4.2 Detectors 188
7.4.2.1 Ion chambers 188
7.4.2.2 Solid-state detectors 188
7.4.2.3 Proportional counters 189
7.4.2.4 Electron yield detectors 189
7.5 Limitations 189
7.6 Examples of Applications 191
7.6.1 Mo/H-ZSM5 Catalyst for Non-oxidative CH Reactions 191
4
7.6.2 Cu/ZnO Methanol Synthesis Catalyst 191
Contents XI
8 In Situ Measurement of Heterogeneous Catalytic Reactor Phenomena
using Positron Emission 195
8.1 Introduction 195
8.1.1 Positron Emission and Positron-Electron Annihilation 196
8.1.2 Detection Methods Based on Positron Emission 197
8.1.3 Positron Emission Tomography (PET), Particle Tracking (PEPT) and
Profiling (PEP) 199
8.2 PEP Detectors and the Synthesis of Labeled Molecules Containing
Positron-Emitting Isotopes 201
8.2.1 The TU/e PEP Detector 201
8.2.2 The Improved PEP Detector 203
8.2.3 Synthesis of Radiolabeled Molecules 206
8.2.3.1 UCO, UCO ,11CH C H 206
2 3 5 11
8.2.3.2 13NO, 13NH 208
3
8.2.3.3 15OO, N15O 208
2
8.3 Applications of PEP in Catalysis 209
8.3.1 Measurement of Mass Transfer and Adsorption Properties of
Alkanes in Zeolite Packed-Bed Reactors 210
8.3.1.1 The labeled-pulse method (in situ tracer pulse
chromatography) 210
Experimental details 211
Data analysis (modelling) 212
Numerical evaluation of the model 217
Results 218
8.3.1.2 By leak injection: tracer exchange positron emission profiling
(TEX-PEP) 220
Experimental details 220
Modelling 222
Results 224
8.3.2 Measruement of the Reaction Kinetics of CO Oxidation on
Pt/Ceria/Alumina Using nCO 225
8.3.2.1 Experimental details 225
8.3.2.2 Modelling 226
8.3.2.3 Results 229
8.4 Other (Potential) Applications of PEP in Catalysis Research 230
List of Symbols used 23 7
9 TAP Reactor Studies 237
9.1 Introduction 237
9.1.1 What is the TAP Method? 237
9.1.2 How Can We Classify the TAP Method? 238
9.1.3 What is the TAP Method for? 239
XII Contents
9.2 Description and Operation of the TAP Reactor System 23 9
9.2.1 The TAP Reactor System 239
9.2.2 Types of Experiments 243
Single-pulse experiments to derive diffusivities (of) and heats of
adsorption (AH ) 243
flds
Series of pulse experiments from a single valve 245
Series of sequential-pulse experiments from separate valves (two
reactants) 246
Experiments with continuous viscous gas flow at low pressure
(<10 mbar) 246
Experiments with continuous viscous gas flow at high pressure
(1 to 3 bar) 246
Temperature-programmed experiments 247
Experiments with isotopes 248
9.3 Modeling the TAP Experiment 248
9.3.1 The Basis of TAP Pulse Modeling - Description of Gas
Transport 249
9.3.2 Analytical Solution for TAP Pulse Experiments 250
9.3.3 Numerical Solution for TAP Pulse Experiments 251
9.3.4 Reactor Models 252
9.3.4.1 One-zone reactor model 252
Example of a simple adsorption - desorption - diffusion case 253
9.3.4.2 Three-zone reactor model 254
9.3.5 What is the Best Model? 254
9.4 Selected Applications in Heterogeneous Catalysis 255
9.4.1 Historical Overview 255
9.4.2 Investigation of Non-reactive Interactions of Gases with Solid
Catalysts 256
9.4.2.1 Diffusion coefficients 256
9.4.2.2 Irreversible interaction 256
9.4.2.3 Reversible interaction 257
9.4.2.4 Competitive interaction of different gases 258
9.4.2.5 Adsorption/desorption properties in the presence of chemical
reaction 259
9.4.3 Determination of Reaction Mechanisms 259
9.4.3.1 Reaction sequences 260
9.4.3.2 Information about gaseous short-lived intermediates 261
9.4.3.3 Information about adsorbed short-lived intermediates 262
9.4.3.4 Identification of different active sites and properties of the reacting
solid 264
9.5 Concluding Remarks 265
Subject Index 271