New and Future Developments in Catalysis

Activation of Carbon Dioxide

Steven L Suib

• Publisher: Elsevier
• Year: 2013
• eBook ISBN: 9780444538833
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

New and Future Developments in Catalysis is a package of books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes.This volume presents a complete picture of all carbon dioxide (CO2) sources, outlines the environmental concerns regarding CO2, and critically reviews all current CO2 activation processes. Furthermore, the volume discusses all future developments and gives a critical economic analysis of the various processes. - Offers in-depth coverage of all catalytic topics of current interest and outlines future challenges and research areas - A clear and visual description of all parameters and conditions, enabling the reader to draw conclusions for a particular case - Outlines the catalytic processes applicable to energy generation and design of green processes

Chapter 1

Catalytic Processes for Activation of CO₂

Narcís Homs^a,b, Jamil Toyir^c and Pilar Ramírez de la Piscina^a, ^aDepartament de Química Inorgànica and Institut de Nanociència i Nanotecnologia, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain, ^bCatalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1, 08930 Barcelona, Spain, ^cUniversité Sidi Mohamed Ben Abdellah, Faculté Polydisciplinaire, B.P 1223, Taza, Morocco

1.1 Introduction

CO₂ can be considered a carbon source rather than just a greenhouse gas (GHG) that needs to be mitigated. As a result of tough policies on GHG emissions, CO₂ has turned out to be a strategic carbon source, available as free or even with a financial return if adequate technology is applied for CO₂ capture and recycling. From this perspective, an attractive opportunity is emerging for a new CO₂-based economy. The chemical recycling of CO₂ and its reuse in the production of fuels or other chemicals is attractive from both an environmental perspective and in terms of fossil source independency. CO₂ is released as a by-product in the chemical and petrochemical industry and in fermentation processes and currently, new technological possibilities based on membranes and absorbents are opening up for its separation and capture. High purity CO₂ is available from such sources; indeed, some such emissions are already used in the production of chemicals such as CO₂ from the ammonia industry which is fed to urea plants or CO₂ from fermentation which is recycled into the beverage industry after appropriate cleaning. Moreover, large-scale emissions of CO₂ come from power plants fueled by natural gas and from the cement industry; in these cases undesired impurities must be taken into account before the CO₂ becomes useful. However, these sources can be considered an opportunity for large-scale recycling of CO₂. In what follows we will consider different options for the reuse of CO₂ by means of chemical recycling.

We must bear in mind that CO₂ is classified as a stable, almost inert molecule. To activateCO₂, it is necessary to overcome its considerable Gibbs energy of formation:

. Nevertheless, CO₂ use is thermodynamically possible via numerous reactions involving its reduction or its incorporation into other compounds.

The reduction of CO₂ by the cleavage of the C

O bond(s) and the formation of new C—H or C—C bond(s) can be accomplished using a reductant. In this case, the action of an appropriate catalyst can convert CO₂ into a potential energy vector. This recycling pathway requires a large input of energy and usually H₂ as the reductant, and leads to fuels such as methane and methanol. In this context, two aspects must be taken into account: the production of H₂ and the energy source. If the energy comes from renewable sources and the H₂ does not come from fossil fuels, does the overall process merit further interest. Nowadays, we can engage optimized electrolysis of water to supply the H₂, thus avoiding the fossil fuel starting material. The use of non-constant wind energy or electrical energy produced at night can be used to obtain H₂, thereby matching the necessity to store such excess energy. In fact, storage of H₂ itself is necessary; one nice way to accomplish this is to incorporate the hydrogen into a liquid fuel. Then, since the products obtained from the catalytic hydrogenation of CO₂ can be directly used as fuels, overall this process could be seen as a means of electrical energy storage and transport. However, the recycling of CO₂ to fuels implies its immediate release into the environment.

The incorporation of CO₂ into chemicals as a C₁ building block is the other approach to its reuse. In this case, lower energy input is required since the whole CO₂ molecule is used without the need to cleave the C

O bond(s). However, to accomplish a desired reaction, the action of a catalyst is also usually necessary. In this CO₂ recycling pathway, different parameters need to be taken into account to determine the viability of a proposed process. The amount of CO₂ fixed and the overall energy balance of the complete chemical route, together with the value of the product produced, could indicate how feasible this process is. Large-scale production of highly valued polymers could be performed using recycled CO₂, thus also diminishing the use of fossil resources. In this way, if highly stable long-life materials are produced, the CO₂ storage could be very long term and therefore the release of CO₂ into the environment could be very slow.

In recent years, extensive research has been carried out into these aspects of CO₂ reuse and numerous publications have appeared [1–12]. This chapter therefore presents recent advances in the conversion of CO₂ into fuels and desirable chemical products by using heterogeneously catalyzed processes, which are summarized in Figure 1.1.

Figure 1.1 Catalytic routes for CO₂ activation in heterogeneous phase leading to fuels and chemicals.

The chapter is divided in different sections. After the Introduction, the second section is dedicated to the reactions of CO₂ with hydrogen; particular attention is paid to large-scale processes that produce synfuels: methanol, dimethyl ether (DME), methane and higher hydrocarbons and alcohols. Then, CO₂-reforming processes of methane and alcohols, and dehydrogenation processes using CO₂ are presented in Section 1.3. Catalytic processes based on CO₂ insertion into organic compounds to form carbonates or carboxylic acids are discussed in Section 1.4. In the last part, future trends in the catalytic conversion of CO₂ are presented with a particular focus on processes that aim to produce strategic chemicals or fuels using renewable energy sources.

1.2 Reactions of CO₂ with hydrogen

1.2.1 Hydrogenation of CO₂ to Methanol

Methanol is extensively used as a starting material for the production of several bulk chemicals and liquid fuels [2]. Furthermore, the use of methanol as a medium for the storage and transportation of hydrogen and as fuel in direct methanol fuel cells (DMFC) could increase demand for it in a future.

Nowadays, methanol production uses syngas (a CO/CO₂/H₂ mixture) produced from fossil sources and Cu/ZnO-based catalysts. However, methanol production from CO₂ and hydrogen (Eq. (1.1)) is now considered a serious alternative which could contribute to ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Introduction
• Contributors
• Chapter 1. Catalytic Processes for Activation of CO2
• Chapter 2. Surface Science Studies of Carbon Dioxide Chemistry
• Chapter 3. Mechanistic Understanding of Catalytic CO2 Activation from First Principles Theory
• Chapter 4. Catalytic Activation and Conversion of Carbon Dioxide into Fuels/Value-Added Chemicals Through C—C Bond Formation
• Chapter 5. Catalytic Transformation of CO2 into Value-Added Organic Chemicals
• Chapter 6. Application of Carbon Dioxide in Hydrogen Storage: Homogeneous Hydrogenation of Carbon Dioxide and Dehydrogenation of Formic Acid
• Chapter 7. Recent Advances on the Catalysts for Activation of CO2 in Several Typical Processes
• Chapter 8. Catalytic Synthesis of CO Free Hydrogen
• Chapter 9. Transition-Metal-Catalyzed C—C Bond Forming Reactions with Carbon Dioxide
• Chapter 10. Electro-Catalytic Reduction of Carbon Dioxide
• Chapter 11. Carbon Dioxide Reforming of Methane to Syngas over Mesoporous Material Supported Nickel Catalysts
• Chapter 12. Chemical Functions of Dense Phase CO2 as Accelerator/Modifier in Organic Synthetic Reactions
• Chapter 13. Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides
• Chapter 14. Environmental Concerns Regarding CO2
• Chapter 15. Catalyst Development for CO2 Activation to Produce Syn-Gas through CO2 Reforming of CH4: Mitigation of Carbon Formation on Ni-Based Catalysts
• Chapter 16. Carbon Dioxide as Soft Oxidant and Promoter in Oxidation Catalysis
• Chapter 17. Biomimetic Approaches to Reversible CO2 Capture from Air. N-Methylcarbaminic Acid Formation in Rubisco-Inspired Models
• Chapter 18. CO2 Adsorption in Porous Materials
• Chapter 19. Carbon Dioxide Activation and Conversion
• Chapter 20. Photocatalytic Conversion of Carbon Dioxide into Fuels Using Layered Double Hydroxides Coupled with Hydrogen or Water
• Chapter 21. CO2 Capture by CaO-Based Sorbents and Sorption Enhanced Reaction Systems
• Index