James F. Haw In-Situ Spectroscopy in Heterogeneous Catalysis

Transcription

1 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:

2 Related Titles from Wiley-VCH Niemantsverdriet, J. W. Spectroscopy in Catalysis. An Introduction Second Edition 2000, ISBN X Sheldon, R. A.; van Bekkum, H. Fine Chemicals through Heterogeneous Catalysis ISBN Ertl, G.; Knözinger, G.; Weitkamp, J. Preparation of Solid Catalysts ISBN Ertl, G.; Knözinger, G.; Weitkamp, J. Handbook of Heterogeneous Catalysis 5 Volume Set ISBN

3 l n-s it u Spectroscopy in Heterogeneous Catalysis Edited by James F. Haw ^WILEY-VCH

4 Editor Prof. Dr. James F. Haw Loker Hydrocarbon Research Institute and Department of Chemistry University of Southern California University Park Los Angeles CA USA This book was carefully produced. Nevertheless, editor, authors and publisher do not warrant the information contained therein to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate. Library of Congress Card No.: applied for British Library Cataloguing-in-Publication Data: A catalogue record for this book is available from the British Library. Die Deutsche Bibliothek - CIP Cataloguingin-Publication-Data A catalogue record for this publication is available from Die Deutsche Bibliothek Wiley VCH Verlag GmbH, Weinheim, 2002 Printed on acid-free paper. All rights reserved (including those of translation in other languages). No part of this book may be reproduced in any form - by photoprinting, microfilm or any other means - not transmitted or translated into machine language without written permission from the publisher. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. Composition pagina media gmbh, Hemsbach Printing Strauss Offsetdruck, Mörlenbach Cover Shown on the cover is the ^f" 8 Großbuchbinderei J. Schäffer GmbH & methanol-to-olefm catalyst HSAPO-34 C ' KG ' Grunstadt containing reactants, intermediates, lbbn products, and a deactivating species, 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.

5 VII Contents 1 Overview of In Situ Methods in Catalysis I 1.1 Introduction I 1.2 Catalytic Materials Compromises Reactor Design Catalyst Composition and Feed Temperature Theoretical Calculations - A Promising Future Spectators Future Prospects for In Situ Studies of Catalysis My Introduction to In Situ Studies of Catalysis 11 2 In Situ Catalysis and Surface Science Methods Introduction Surface Science Tools Sum Frequency Generation (SFG)-surface specific vibrational spectroscopy The high-pressure high-temperature Scanning Tunneling Microscope (STM) Applications of In Situ Methods in Surface Science to Catalysis High-Pressure SFG Studies Ethylene hydrogenation on Pt(lll) Propylene hydrogenation and dehydrogenation on Pt(lll) Cyclohexene hydrogenation and dehydrogenation on Pt(lll) and Pt(lOO) CO oxidation on Pt(l 11) High-Pressure STM Studies High-pressure CO on Pt(lll) [33] High-pressure NO on Rh(lll) 43

6 VMM Contents Tip-induced catalysis [36-38] 46 Preparation of hydrocarbon clusters 46 Tip-catalyzed hydrogenation of hydrocarbon clusters 47 Tip-catalyzed oxidation of hydrocarbon clusters Challenges and Future Directions 51 3 In Situ N M R Introduction Methods of In Situ NMR General Considerations In Situ NMR of Photocatalysis In Situ NMR of Thermal Reactions in Sealed MAS Rotors Sealed Rotors with Transient Heating In Situ MAS Flow Probes Magic-Angle Hopping Flow Probes In Situ NMR using Quench Reactors Applications of In Situ NMR to Methanol-to-Olefm Catalysis Overview HSAPO-34 Catalyst Structure Pulse-Quench In Situ NMR of the Hydrocarbon Pool on HSAPO Correlation of Product Selectivity (GC) with Catalyst Structure (NMR) Some Limitations of In Situ NMR 78 4 Theoretical Catalysis: Methods, Applications, and Future Directions Introduction Theoretical Methods Classical Mechanics Force fields Classical mechanical techniques 90 Energy minimization 90 Monte Carlo simulation 91 Molecular dynamics simulation Prediction of experimental data with classical mechanical methods Quantum Mechanics S emiempirical methods Ab initio methods Density functional theory Prediction of experimental data by quantum mechanical methods 97 NMR properties 98

7 Contents 4.3 Model Systems 99 Our common quantum mechanical strategy Applications of Theoretical Methods to Catalysis 101 4A.I Diffusion of Adsorbates in Silicalite Theoretical Characterization of Zeolite Acidity Solvent-Assisted Proton Transfer in Catalysis by Zeolite Solid Acids Activation of Br0nsted Acids by Lewis Acids: The Creation of New Solid Acid Catalysts Carbenium Ion Chemistry on Solid Acids: Theoretical NMR Base Catalysis by Metal Oxide Surfaces Future Developments in Computational Catalysis Computing Power Approvements in General Methodology Plane-Wave DFT Combinatorial Catalysis In Situ Ultraviolet Raman Spectroscopy Introduction Instrumentation and Experimental Methods The Spectrometer The Fluidized Bed Sample Cell Raman Tribometer Two Examples of Results Coke Formation in the Methanol-to-Gasoline Reaction Lubricant Chemistry Summary In Situ Infrared Methods Introduction Experimental Aspects In situ cells for transmission Spectroscopy Diffuse Reflectance Spectroscopy Infrared Emission Spectroscopy Infrared Microspectroscopy Reflection-Absorption Infrared Spectroscopy (RAIRS) Sum Frequency Generation Spectroscopy (SFG) Picosecond Infrared Spectroscopy Recent Applications of in situ Infrared Spectroscopy Zeolite Catalysts Low-temperature bond migration in olefins Methanol conversion over acid zeolites Side-chain alkylation of toluene Selective Catalytic Reduction (SCR) of NO X 157 IX

8 X Contents Oxide Catalysts S elective catalytic reduction of N O by ammonia over vanadia/titania In situ DRIFTS study of NO reduction by CH 4 over La 2 O Picosecond Infrared Spectroscopy on Single-Crystal Oxide Surfaces Supported Metal Catalysts Alkane reactions over bifunctional zeolites DRITS study of NO decomposition over carbon-supported Rh and Pd DRIFTS study of NO X reduction by propene Metal Surfaces In situ RAIRS study of kinetic oscillations in the Pt(lOO) NO + CO system RAIRS studies of electrocatalysis Conclusions and Future Prospects In situ XAS Characterization of Heterogeneous Catalysts Introduction: X-ray Absorption Spectroscopy (XAS) Information Content of XAS X-ray Absorption Near-Edge Spectrum (XANES) Elemental analysis Oxidation state and site symmetry Empirical analysis of XANES Extended X-ray Absorption Fine Structure (EXAFS) Scope of Applicability of XAS Applicability to Elements Low-Z elements (C, N, O, and F) Mg, AI, and Si P, S,andCl High-energy edges (Z > 21) Accessible In Situ Conditions Mechanics of Measurement The XAS Spectrometer - The Beamline Detectors Ion chambers Solid-state detectors Proportional counters Electron yield detectors Limitations Examples of Applications Mo/H-ZSM5 Catalyst for Non-oxidative CH 4 Reactions Cu/ZnO Methanol Synthesis Catalyst 191

9 Contents XI 8 In Situ Measurement of Heterogeneous Catalytic Reactor Phenomena using Positron Emission Introduction Positron Emission and Positron-Electron Annihilation Detection Methods Based on Positron Emission Positron Emission Tomography (PET), Particle Tracking (PEPT) and Profiling (PEP) PEP Detectors and the Synthesis of Labeled Molecules Containing Positron-Emitting Isotopes The TU/e PEP Detector The Improved PEP Detector Synthesis of Radiolabeled Molecules U CO, U CO 2, 11 CH 3 C 5 H NO, 13 NH OO, N 15 2 O Applications of PEP in Catalysis Measurement of Mass Transfer and Adsorption Properties of Alkanes in Zeolite Packed-Bed Reactors The labeled-pulse method (in situ tracer pulse chromatography) 210 Experimental details 211 Data analysis (modelling) 212 Numerical evaluation of the model 217 Results By leak injection: tracer exchange positron emission profiling (TEX-PEP) 220 Experimental details 220 Modelling 222 Results Measruement of the Reaction Kinetics of CO Oxidation on Pt/Ceria/Alumina Using n CO Experimental details Modelling Results Other (Potential) Applications of PEP in Catalysis Research 230 List of Symbols used TAP Reactor Studies Introduction What is the TAP Method? How Can We Classify the TAP Method? What is the TAP Method for? 239

10 XII Contents 9.2 Description and Operation of the TAP Reactor System The TAP Reactor System Types of Experiments 243 Single-pulse experiments to derive diffusivities (of) and heats of adsorption (AH flds ) 243 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 Modeling the TAP Experiment The Basis of TAP Pulse Modeling - Description of Gas Transport Analytical Solution for TAP Pulse Experiments Numerical Solution for TAP Pulse Experiments Reactor Models One-zone reactor model 252 Example of a simple adsorption - desorption - diffusion case Three-zone reactor model What is the Best Model? Selected Applications in Heterogeneous Catalysis Historical Overview Investigation of Non-reactive Interactions of Gases with Solid Catalysts Diffusion coefficients Irreversible interaction Reversible interaction Competitive interaction of different gases Adsorption/desorption properties in the presence of chemical reaction Determination of Reaction Mechanisms Reaction sequences Information about gaseous short-lived intermediates Information about adsorbed short-lived intermediates Identification of different active sites and properties of the reacting solid Concluding Remarks 265 Subject Index 271