Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

Abstract

Table of Contents 1. Introduction 2. Experimental Methods 2.1. Materials 2.1.1. Metal-Substituted MFI Frameworks 2.1.2. Cu-Substituted Zeolites 2.1.3. Cr/SiO2 Phillips catalyst 2.1.4. CuCl2/Al2O3 2.1.5. Metal-Supported Catalysts 2.2. Techniques and Experiential Set-ups 2.2.1. X-ray Beam Optimization: Energy Selection 2.2.2. X-ray Beam Optimization: Harmonic Rejection 2.2.3. X-ray Absorption Spectroscopy: Acquisition Setups for Standard and Time-Resolved Experiments 2.2.4. X-ray Emission Spectroscopy: Acquisition Setup 2.2.5. High-Energy Resolution Fluorescence Detected (HERFD) XANES and EXAFS and Range-Extended EXAFS Spectroscopy 2.2.6. In Situ and Operando Cells for Hard and Soft XAFS 2.2.7. Experimental Set-Ups for Micrometer-Resolved Experiments 2.3. EXAFS and XANES Theory and Data Analysis 2.3.1. Brief Historical Overview 2.3.2. Single-Scattering Approximation 2.3.3. Multiple-Scattering Expansion 2.3.4. Codes for EXAFS Data Analysis 2.3.5. Codes for XANES Data Analysis 2.3.6. Codes for XES Spectra Simulation 2.3.7. Codes for Handling the Huge Numbers of Spectra Generated in Time or Space Resolved Experiments 2.3.8. Debye–Waller Factors and Disorder 2.3.9. Differential XAFS Approach 2.4. Atomic XAFS or AXAFS 2.4.1. Brief Historical Overview 2.4.2. Physical Principles of AXAFS 2.5. Other Related Techniques 2.5.1. X-ray Magnetic Circular Dichroism (XMCD) 2.5.2. Diffraction Anomalous Fine Structure (DAFS) 2.5.3. Extended Energy-Loss Fine Structure (EXELFS) 2.5.4. Total scattering: the pair distribution function (PDF) approach 3. Metal Isomorphous Substitution in Zeolitic Frameworks: Ti, Fe, and Ga 3.1. Relevance of Ti-, Fe-, and Ga-Silicalite-1, and B-CHA in the Field of Catalysis 3.2. TS-1 3.2.1. Brief Historical Overview on the Role Played by EXAFS and XANES Techniques in Understanding the Nature of Ti Sites in TS-1 3.2.2. Template Burning in TS-1: XANES, EXAFS, and XES Results Compared with Adsorption of Ligand Molecules 3.2.3. Effect of the Amount of Incorporated Heteroatom 3.2.4. Modeling of [Ti(OSi)4] Perfect Sites in Interaction with Ligands by an Ab Initio Periodic Approach: Comparison with EXAFS Results 3.2.5. Reactivity of Framework Ti Species toward H2O2/H2O 3.3. Fe- and Ga-Silicalite 3.3.1. Role of EXAFS in Understanding the Effect of Template Burning in Ga- and Fe-Substituted Silicalite 3.3.2. Role of EXAFS in the Debate Concerning the Nuclearity of Extraframework Fe Species in Zeolites 3.3.3. Fe-Substituted Silicalite: What Has Been Learnt from XANES 3.3.4. Reactivity of Extraframework Fe Species Hosted in the MFI Channels toward N2O and NO 3.3.5. New Frontiers of XAS/XES Techniques Applied to the Characterization of Fe-Zeolites 3.4. B-CHA 3.4.1. Template Burning in B-SSZ-13 an example of low energy XAFS 3.4.2. Reactivity of B-SSZ-13 toward NH3 3.5. Other Metal Isomorphous Substitutions 4. Cation-Exchanged Zeolites: The Copper Case Study 4.1. Preparation of Cu+-Exchanged Zeolites Exhibiting a Model Compound Character 4.2. Cu+-ZSM-5 4.2.1. XANES Characterization of Intrazeolitic Cuprous Carbonyl Complexes in Cu+-ZSM-5 4.2.2. EXAFS Determination of the Structure of Cu+(CO)n Complexes 4.3. Cu+-MOR 4.3.1. XANES and EXAFS Study of Cu+(CO)n Complexes Hosted in Cu+–MOR: Comparison with Cu+-ZSM-5 4.4. Reactivity toward NO: In Situ Cu+ → Cu2+ Oxidation in Cu+-ZSM-5 and Cu+-MOR 4.4.1. Temperature Dependent NO Reaction in Cu+-ZSM-5 4.4.2. Temperature-Dependent NO Reaction in Cu+-MOR 4.5. Bent mono-(μ-oxo)dicupric and bis(μ-oxo)dicopper Biomimetic Inorganic Models for NO Decomposition and Methane Oxidation in Cu-ZSM-5: Comparison with Fe-ZSM-5 5. Structure and Reactivity of Metallorganic Frameworks Probed by In Situ XAFS and XES 5.1. Adsorption of CO on Cu2+ Sites in Cu3(BTC)2 or HKUST-1 5.2. Adsorption of O2 on Cr2+ Sites in Cr3(BTC)2 5.2.1. XANES Study 5.2.2. XES Study 5.3. Adsorption of NO, CO, and N2 on Ni2+ sites in Ni-CPO-27 6. Cr/SiO2 Phillips Catalyst: In Situ Ethylene Polymerization 6.1. Relevance of the Catalyst and Still Open Questions 6.2. XAFS Applied on the Phillips Catalyst 6.2.1. A 4 wt % Cr/SiO2 Sample: XAFS in Transmission Mode 6.2.2. A 0.5 wt % Cr/SiO2 Sample: XAFS in Fluorescence Mode 6.3. SEXAFS Applied on the Phillips Catalyst: Bridging the Gap between Heterogeneous Catalysis and Surface Science 6.3.1. Brief Overview on SEXAFS Applied to Catalysis 6.3.2. SEXAFS Applied to a Planar Model of the Phillips Catalyst 7. Space-Resolved X-rays Experiments 7.1. Brief Introduction to X-ray Space-Resolved Studies in Catalysis 7.2. Cu/ZnO Case Study 8. Time-Resolved XAFS on Catalyst at Work: OPERANDO Experiments 8.1. Brief Introduction to Time-Resolved Studies in Catalysis 8.2. CuCl2/Al2O3 Case Study 8.2.1. Industrial Relevance of the CuCl2/Al2O3 System 8.2.2. Preliminary in Situ XAFS Experiments 8.2.3. Operando Experiments 9. XAS and XES Studies on Supported Metal Nanoparticles 9.1. XAFS Applied to Supported Metal Nanoparticles: A Brief Overview 9.2. Preparation of Pd-Supported Catalysts Follow