Low-Temperature Selective Catalytic Reduction Catalysts

Contents
1 The Harm of NOx and Its Emission 1
1.1 NOx 1
1.1.1 The Characteristic of NOx 1
1.1.2 The Harm of NOx 2
1.2 The Formation Mechanism of NOx 4
1.2.1 NOx Formation Mechanism and the Interfering Factors 4
1.2.2 Sources of NOx 6
References 8
2 NOx Emission Control Technologies (NOx Emission Abatement) 11
2.1 Introduction 11
2.1.1 Pre-combustion and Combustion Modification 11
2.1.2 Post-combustion Methods 13
2.2 SCR Process Configurations 14
2.2.1 HD-SCR Configuration 15
2.2.2 LD-SCR Configuration 17
2.2.3 TE-SCR Configuration 17
2.3 Low-Temperature SCR Catalyst 17
2.4 Low-Temperature SCR Mechanism 19
2.4.1 Eley-Rideal (E-R) Mechanism 19
2.4.2 L-H Mechanism 20
2.5 Application of Density Functional Theory (DFT) in the Study of Low Temperature SCR Catalyst 21
References 22
3 Preparation of Catalysts 25
3.1 General Process of NH3-SCR Catalysts Preparation 25
3.2 Precipitation Method 25
3.2.1 Precipitating Classical Theory 26
3.2.2 Factors Affecting Catalyst Performance in the Precipitation Method 28
3.2.3 Brief Conclusion 30
3.3 Sol-Gel Method 30
3.3.1 Fundamentals of Sol-Gel Process 31
3.3.2 Sol-Gel Methods for Preparing Supported Metals 31
3.3.3 Brief Conclusion 33
3.4 Impregnation Method 33
3.4.1 Impregnating Solution Preparation 34
3.4.2 The Influencing Factors of the Impregnation Method 35
3.4.3 Brief Conclusion 36
3.5 Hydrothermal Method 36
3.5.1 Basic Concepts of Hydrothermal Method 36
3.5.2 Principles of Hydrothermal Synthesis Methods 37
3.5.3 Brief Conclusion 38
References 39
Catalyst Characterization 41
4.1 Electron Microscopy 41
4.1.1 Scanning Electron Microscope (SEM) 41
4.1.2 Transmission Electron Microscope (TEM) 43
4.2 BET Surface Area 46
4.2.1 BET Theory 46
4.2.2 The Calculations of BET Surface Area 48
4.2.3 Drawbacks and Limitations 48
4.3 X-Ray Diffraction Techniques 49
4.3.1 Foundations of Crystallography 49
4.3.2 Powder XRD Diffraction Analysis 51
4.3.3 Application of X-Ray Diffraction in Catalyst Research 52
4.4 X-Ray Photoelectron Spectroscopy Techniques 55
4.4.1 The Features of XPS Spectra 56
4.4.2 Case Study 56
4.5 Temperature-Programmed Analysis Technique 58
4.5.1 Temperature-Programmed Desorption (TPD) 58
4.5.2 Temperature-Programmed Reduction (TPR) 60
4.6 Raman Spectroscopy 61
4.6.1 Basic Principles of Analysis 62
References 64
MnOx-Based SCR Catalyst 69
5.1 Introduction 69
5.2 Single Manganese Oxide Catalysts 70
5.2.1 Effect of Oxidation State and Crystal Structure on Catalytic Performance 70
5.2.2 Effect of Specific Surface Area and Surface Acidity on Catalytic Performance 71
5.2.3 Effect of Morphology and Exposed Crystalline Surfaces on Catalytic Performance 72
5.3 Multi-metal Manganese Oxide Catalysts 73
5.4 Supported Manganese Oxide-Based Catalysts 77
5.4.1 MnOx-Based Catalysts Supported on Ti02 78
5.4.2 MnOx-Based Catalysts Supported on AI2O3 81
5.4.3 MnOx-Based Catalysts Supported on Carbon Materials 82
References 83
Ceria-Based SCR Catalysts 87
6.1 Introduction 87
6.2 Single Ceria-Based Catalysts 88
6.2.1 Effect of Precursor and Calcination Temperature on Catalytic Performance 88
6.2.2 Effect of Preparation Method on Catalytic Performance 90
6.2.3 Effect of Morphology and Exposed Crystalline Surfaces on Catalytic Performance 92
6.3 Composite Ceria-Based Catalysts 93
6.3.1 Mn-Ce Composite Oxide System 93
6.3.2 Ce-Cu Composite Oxide System 94
6.3.3 Ce-Ti Composite Oxide System 95
6.4 Supported Ceria-Based Catalysts 97
6.4.1 CeO2 as the Support 97
6.4.2 CeO2 as the Surface Loading Component 97
References 102
Cu-Based and Fe-Based SCR Catalysts 105
7.1 Introduction 105
7.2 Cu-Based SCR Catalysts 105
7.2.1 Copper Oxide-Based Catalyst 105
7.2.2 Copper Based Molecular Sieve Catalyst 106
7.2.3 Core-Shell Structure in Copper Based NH3-SCR Catalysts 107
7.3 Fe-Based SCR Catalysts 109
7.3.1 Iron Oxide-Based Catalyst 109
7.3.2 Fe Based Molecular Sieve 112
References 112
Chemical Deactivation and Resistance of Low-Temperature SCR Catalyst 115
8.1 Introduction 115
8.2 Deactivation Mechanism of SCR Catalysts by Various Elements 116
8.2.1 S02 and H20 116
8.2.2 Alkali Metals/Alkali-Earth Metals 120
8.2.3 Heavy Metals 121
8.3 Deactivation Resistance 123
8.3.1 Resistance to SO2 or/and H2O Poisoning 123
8.3.2 Resistance to Alkali/Alkaline Metal Poisoning 125
8.3.3 Resistance to Heavy Metal Poisoning 126
References 128