Catalysis By Ceria And Related Materials (2nd Edition)

Alessandro Trovarelli, Paolo Fornasiero

• Publisher: ICP
• Year: 2013
• Print ISBN:
  9781848169630
• Edition: 2
• eBook ISBN:
  9781848169654
• Topic: Biological Sciences
• Subtopic: Science General
• Index: Biological Sciences

This book follows the 2002 edition of Catalysis by Ceria and Related Materials, which was the first book entirely devoted to ceria and its catalytic properties. In the ten years since the first edition a massive amount of work has been carried out in the field, and ceria has gained a prominent position in catalysis as one of the most valuable material for several applications. This second edition covers fundamental and applied aspects of the latest advances in ceria-based materials with a special focus on structural, redox and catalytic features. Special emphasis is given to nano-engineered and nano-shaped systems which are a key factor in the predictive and rational design of ceria with novel properties.

In addition, the book presents recent advances in emerging and traditional large-scale applications of ceria in catalysis, such as the treatment of emissions from mobile sources (including diesel and gasoline engines). The primary readership includes catalysis and material science researchers from academy and industry and postdoctorate and graduate students in chemistry, chemical engineering and physics.

Contents:

• Crystal and Electronic Structures, Structural Disorder, Phase Transformation, and Phase Diagram of Ceria–Zirconia and Ceria-Based Materials (Masatomo Yashima)
• Understanding Ceria-Based Catalytic Materials: An Overview of Recent Progress (Juan José Delgado, Eloy del Río, Xiaowei Chen, Ginesa Blanco, José María Pintado, Serafín Bernal and José Juan Calvino)
• Investigation of the Oxygen Storage and Release Kinetics of Model and Commercial Three-Way Catalytic Materials by Transient Techniques (Angelos M Efstathiou and Stavroula Y Christou)
• Interaction of Nitrogen Oxides with Ceria-Based Materials (Avelina García-García and Agustin Bueno-López)
• Atomistic Modelling of Ceria Nanostructures: Introducing Structural Complexity (Dean C Sayle and Thi X T Sayle)
• Two-Dimensional and Three-Dimensional Ceria-Based Nanoarchitectures (Zhen-Xing Li, Wei Feng, Chao Zhang, Ling-Dong Sun, Ya-Wen Zhang and Chun-Hua Yan)
• Core-Shell-Type Materials Based on Ceria (Matteo Cargnello, Raymond J Gorte and Paolo Fornasiero)
• New Developments in Ceria-Based Mixed Oxide Synthesis and Reactivity in Combustion and Oxidation Reactions (Benjaram M Reddy, Thallada Vinod Kumar and Naga Durgasri)
• Design and Modeling of Active Sites in Metal–Ceria Catalysts for the Water Gas Shift Reaction and Related Chemical Processes (Jose A Rodriguez)
• Ceria-Based Gold Catalysts: Synthesis, Properties, and Catalytic Performance for the WGS and PROX Processes (Donka Andreeva, Tatyana Tabakova and Lyuba Ilieva)
• Ceria-Based Formulations for Catalysts for Diesel Soot Combustion (Eleonora Aneggi, Carla de Leitenburg and Alessandro Trovarelli)
• Ceria and Its Use in Solid Oxide Cells and Oxygen Membranes (Christodoulos Chatzichristodoulou, Peter T Blennow, Martin Søgaard, Peter V Hendriksen and Mogens B Mogensen)
• Transformation of Oxygenated Compounds Derived from Biomass into Valuable Chemicals Using Ceria-Based Solid Catalysts (Laurence Vivier and Daniel Duprez)
• Ceria-Based Catalysts for Air Pollution Abatement (Anna Maria Venezia, Leonarda Francesca Liotta, Giuseppe Pantaleo and Alessandro Longo)

Readership: Graduate students and researchers in the fields of chemistry, physics, materials science and chemical engineering.

CHAPTER 1

CRYSTAL AND ELECTRONIC STRUCTURES, STRUCTURAL DISORDER, PHASE TRANSFORMATION, AND PHASE DIAGRAM OF CERIA–ZIRCONIA AND CERIA-BASED MATERIALS

Masatomo Yashima

Department of Chemistry and Materials Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-W4-17, O-okayama, Meguro-ku, Tokyo, 152-8551, Japan

1.1 Phase Diagram of the Ce–O System and Structural Properties of Fluorite-Type CeO₂

Cerium exhibits both the +4 and +3 oxidation states.¹ The change of oxidation state between +4 and +3 is the key for the catalysis of ceria-based materials. Thus, the phase diagram of the Ce–O system is important for ceria-based catalysts. The Ce–O system contains a number of crystalline phases (Fig. 1.1).^1–3 Table 1.1 shows some of the phases and their space groups in the Ce–O system.^3–10 There is a disagreement in the literature concerning both the composition and the structure of intermediate phases.

Cerium dioxide CeO₂ has a fluorite-type structure (space group

),^3–7 which is named after the mineral form of calcium fluoride. Figures 1.2(a)–(c) show the crystal structure of cerium dioxide CeO₂. The cerium and oxygen atoms are located at the 4a 0,0,0 and 8c1/4,1/4,1/4 sites, respectively.

Figure 1.1 Phase diagrams of the Ce–O system. (a) Phase diagram of CeO_y, 1.7 ≤ y ≤ 2.0, temperature range 630 ≤ T ≤ 1270 K.^{1, 2} (b)–(d) Calculated phase diagrams of the Ce–O system. Mole fraction of O is x in Ce_1-xO_x (b) 0.0 ≤ x ≤ 1.0, 500 ≤ T ≤ 4500 K, (c) 0.55 ≤ x ≤ 0.70, 500 ≤ T ≤ 3000 K, (d) 0.63 ≤ x ≤ 0.67, 600 ≤ T ≤ 1200 K.³ Reprinted with permission from Elsevier.

The coordination number of the oxygen atoms is four (CN = 4) and the structure consists of OCe₄ tetrahedra (Fig. 1.2(b)). The coordination number of the Ce cations is eight (CN = 8). The crystal structure consists of CeO₈ cubes (Fig. 1.2(c)).

The unit-cell parameter a of CeO₂ increases with temperature (Fig. 1.3(a)).⁵ The atomic displacement parameters of both Ce and O (B (Ce) and B(O)) also increase with temperature (Fig. 1.3(b)).⁵ The higher B(O) values (B(O) > B(Ce)) suggest that the oxygen anions are mobile compared with the Ce cations.

Table 1.1 Some phases and space groups of cerium oxides.

Note: The numbers n and m refer to the stoichiometry compound Ce_nO_2n–2m.

The large thermal vibration of oxygen atoms in CeO₂ is confirmed also by the nuclear-density distribution (Fig. 1.3(c)).^6,7 The nuclear-density map indicates that the distribution of oxide ions increases with an increase of temperature.⁷ The bulges towards the <111> direction are clearly observed for the oxide ions in CeO₂ indicating anisotropic thermal motion.^6,7 This complicated disorder of the oxide ions is responsible for ionic conduction in ceria-based electrolytes. Two possible diffusion paths, in the direction <111> and along the c axis, have been suggested for CeO₂ over a wide temperature range. These features have also been observed in the fast oxide-ion conductor Bi₂O₃.¹² Both CeO₂ and Bi₂O₃ have a cubic fluorite-type structure, suggesting that this disorder and the possible diffusion paths are characteristic of compounds with a cubic fluorite-type structure.

Figure 1.1 shows that the fluorite-structured CeO_2-x has a solid solution phase. The unit-cell parameter of CeO_2-x increases with an increase of defect concentration x^1,13 because the ionic radius of Ce³⁺ is higher than that of Ce⁴⁺. For a coordination number of 8 (CN = 8), the ionic radius of Ce³⁺ after Shannon¹⁴ is r(Ce³⁺,8) = 1.143 Å, while that of Ce⁴⁺ is smaller, r(Ce⁴⁺,8) = 0.97 Å.

Figure 1.2 (a) Crystal structure of the cubic fluorite-type ceria CeO₂. (b) Crystal structure of ceria with OCe₄ tetrahedra. (c) Crystal structure of ceria with CeO₈ cubes. These figures were drawn with the program VESTA.¹¹

1.2 Phases and Structure of Zirconia and Ceria–Zirconia Solid Solutions

Ceria–zirconia materials exhibit high catalytic activity and are used for exhaust gas cleaning.¹⁵ To understand the catalytic activity of ceria–zirconia materials, a knowledge of the phases and the crystal structure of zirconia and ceria–zirconia solid solutions is important.

Figure 1.3 Temperature dependence of (a) unit-cell parameter a and (b) atomic displacement parameters of the cubic fluorite-type CeO₂.⁵ Reprinted with permission from Yashima et al.⁵ Copyright 2003 Elsevier. (c) Nuclear-density distribution of the fluorite-type CeO₂ at 1770 K.^{6, 7} Reprinted with permission from Yashima et al.⁶ Copyright 2004 American Institute of Physics.

1.2.1 Phase transi...

Table of contents

• Cover
• Title Page
• Copyright
• Preface
• Contents
• Chapter 1 Crystal and Electronic Structures, Structural Disorder, Phase Transformation, and Phase Diagram of Ceria–Zirconia and Ceria-Based Materials
• Chapter 2 Understanding Ceria-Based Catalytic Materials: An Overview of Recent Progress
• Chapter 3 Investigation of the Oxygen Storage and Release Kinetics of Model and Commercial Three-Way Catalytic Materials by Transient Techniques
• Chapter 4 Interaction of Nitrogen Oxides with Ceria-Based Materials
• Chapter 5 Atomistic Modelling of Ceria Nanostructures: Introducing Structural Complexity
• Chapter 6 Two-Dimensional and Three-Dimensional Ceria-Based Nanoarchitectures
• Chapter 7 Core-Shell-Type Materials Based on Ceria
• Chapter 8 New Developments in Ceria-Based Mixed Oxide Synthesis and Reactivity in Combustion and Oxidation Reactions
• Chapter 9 Design and Modeling of Active Sites in Metal–Ceria Catalysts for the Water Gas Shift Reaction and Related Chemical Processes
• Chapter 10 Ceria-Based Gold Catalysts: Synthesis, Properties, and Catalytic Performance for the WGS and PROX Processes
• Chapter 11 Ceria-Based Formulations for Catalysts for Diesel Soot Combustion
• Chapter 12 Ceria and its Use in Solid Oxide Cells and Oxygen Membranes
• Chapter 13 Transformation of Oxygenated Compounds Derived from Biomass into Valuable Chemicals Using Ceria-Based Solid Catalysts
• Chapter 14 Ceria-Based Catalysts for Air Pollution Abatement
• Index