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Über dieses Buch

This thesis presents a combination of material synthesis and characterization with process modeling. In it, the CO2 adsorption properties of hydrotalcites are enhanced through the production of novel supported hybrids (carbon nanotubes and graphene oxide) and the promotion with alkali metals. Hydrogen is regarded as a sustainable energy carrier, since the end users produce no carbon emissions. However, given that most of the hydrogen produced worldwide comes from fossil fuels, its potential as a carbon-free alternative depends on the ability to capture the carbon dioxide released during manufacture. Sorption-enhanced hydrogen production, in which CO2 is removed as it is formed, can make a major contribution to achieving this. The challenge is to find solid adsorbents with sufficient CO2 capacity that can work in the right temperature window over repeated adsorption-desorption cycles. The book presents a highly detailed characterization of the materials, together with an accurate measurement of their adsorption properties under dry conditions and in the presence of steam. It demonstrates that even small quantities of graphene oxide provide superior thermal stability to hydrotalcites due to their compatible layered structure, making them well suited as volume-efficient adsorbents for CO2. Lastly, it identifies suitable catalysts for the overall sorption-enhanced water gas shift process.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

This chapter presents the motivation of the research, the objectives of the work and the structure of the thesis.
Diana Iruretagoyena Ferrer

Chapter 2. Literature Review

In this chapter relevant background for the present work is reviewed covering some principles of gas-solid adsorption and the characteristics of promising groups of CO2 adsorbents for carbon capture and storage. The CO2 adsorption properties of layered double hydroxides (LDHs) and their derivatives produced upon thermal treatment (layered double oxides) are described in more detail. Additionally, the strategies reported so far to improve the adsorption performance of LDHs are discussed. The last part of the chapter focuses on hydrogen production highlighting the importance of process intensification by sorption-enhancement.
Diana Iruretagoyena Ferrer

Chapter 3. Experimental Methods

The standard procedures followed to test and characterise a range of LDH based adsorbents and catalysts are described. The use of a thermogravimetric analyser and the design and operation of a packed bed column used to carry out CO2 adsorption measurements are explained in detail. In addition, the experimental setup used to conduct a preliminary screening of catalysts for the sorption-enhanced methanol-to-shift reaction is presented.
Diana Iruretagoyena Ferrer

Chapter 4. Layered Double Hydroxides Supported on Multi-walled Carbon Nanotubes for CO2 Adsorption

This chapter is concerned with the study of layered double hydroxides supported on multi-walled carbon nanotubes. The chapter begins describing the methodology used to synthesise LDHs and LDH/carbon hybrids. Subsequently, the structural and physical properties of the adsorbents are examined by a range of characterisation techniques. Finally the adsorption capacity and thermal stability of the materials are reported.
Diana Iruretagoyena Ferrer

Chapter 5. Layered Double Hydroxides Supported on Graphene Oxide for CO2 Adsorption

This chapter is concerned with the study of layered double hydroxides supported on graphene oxide. The chapter begins describing the methodology used to synthesise LDHs and LDH/carbon hybrids. Subsequently, the structural and physical properties of the adsorbents are examined by a range of characterisation techniques. The adsorption capacity and thermal stability of the materials are reported. Finally, the description of CO2 adsorption equilibrium data under dry conditions using Langmuir, Freundlich and Toth isotherms is included.  
Diana Iruretagoyena Ferrer

Chapter 6. Influence of Alkali Metals on Layered Double Hydroxides Supported on Graphene Oxide for CO2 Adsorption

The effect of alkali metals on the CO2 adsorption performance of unsupported and GO supported layered double hydroxides is investigated. A comparative study of promoting the effect of sodium, potassium and caesium on the adsorbents is presented. In addition, the influence of promoting the adsorbents by impregnation and by leaving residual alkali ions from the synthesis is discussed.
Diana Iruretagoyena Ferrer

Chapter 7. CO2 Adsorption on Unsupported and Graphene Oxide Supported Layered Double Hydroxides in a Fixed-Bed

This chapter addresses the CO2 adsorption kinetics and equilibria of LDH and LDH/GO hybrids under dry and wet conditions using breakthrough curve responses obtained in a fixed-bed column. A comparative study between temperature-swing and isothermal N2 purge experiments is presented. In addition, a mathematical model based on the linear driving force approximation is used to describe the dry experiment profiles.
Diana Iruretagoyena Ferrer

Chapter 8. Sorption-Enhanced Methanol-to-Shift for H2 Production: Thermodynamics and Catalyst Selection

This chapter is divided in two main sections. The first part of the chapter presents a preliminary thermodynamic study to assess the viability of producing hydrogen by the sorption-enhanced methanol-to-shift (SEMTS). In the second section, the suitability of different solid catalysts for the SEWGS and SEMTS is evaluated by conducting the reverse water gas shift and methanol decomposition in temperature-programmed reaction experiments. Some catalysts were further studied in longer-term stability tests under water gas shift conditions.
Diana Iruretagoyena Ferrer

Chapter 9. Conclusions and Future Work

This chapter presents the overall conclusions, contribution of the research and recommendations for future work.
Diana Iruretagoyena Ferrer

Backmatter

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