Carbon dioxide – probably the most frequently mentioned chemical compound in the world media today. Its role in adverse environmental changes and the ways to minimize it present one of the great societal challenges that humanity will be facing in the coming decennia.
In contrast to other “passive” methods (reduction of CO2 emissions at source or CCS technologies), the chemical valorisation of carbon dioxide and its conversion into useful products creates value and it is an indispensable method for sustainable chemical manufacturing. Traditional chemical manufacturing relies on non-renewable fossil energy sources for power and raw materials. To achieve a manufacturing paradigm shift towards better sustainability, it is necessary to use both renewable energy and renewable carbon sources, such as CO2, recycled carbon and biomass, to make fuels and chemicals. It is definitely not easy to valorise CO2 into value products due to the high chemical stability of CO2 and thermodynamic barriers in several chemical transformation routes. However, the already classical process of urea synthesis clearly shows that the chemical conversion of carbon dioxide can be technically and economically feasible.
The idea behind this book is to give the reader a possibly complete and up-to-date overview of the variety of ways carbon dioxide can be chemically valorised. The individual book chapters have been written by the leading experts in the field. The methods and technologies presented are grouped into three broad categories:
Thermochemical and catalytic CO2 valorisation
Renewable energy-based CO2 valorisation
Biochemical CO2 valorisation.
Following a general introduction on turning CO2 into fuels and chemicals (Chapter 1), various ways of homogeneous (catalytic and non-catalytic) methods of valorisation are discussed. Chapters 2 and 3, respectively focus on carboxylation and carbonylation reactions utilizing CO2. Modern developments in urea synthesis are presented in Chapter 4, while Chapter 5 discusses homogeneous hydrogenation of carbon dioxide. Finally, homogeneous CO2 co-polymerization and coupling is presented in Chapter 6. In the section dedicated to heterogeneous processes, Chapters 7–10 discuss hydrogenation, methanation, methane dry reforming and water gas shift reactions, respectively, while Chapter 11 focuses on heterogeneous co-polymerization of CO2.
The second part of the book is dedicated to renewable energy-based CO2 valorisation. The chapters in this part present different routes of direct or indirect transformation of some renewable primary energy source (mostly solar, but also wind) into chemical energy. Included here are CO2 valorisation methods utilizing electricity, which in the long term will be predominantly generated from renewable sources.
Accordingly, processes presented in Chapters 12–14 follow the energy transformation path: solar/wind → electricity → light → chemical and include artificial photosynthesis and photocatalytic CO2 reduction, respectively. On the other hand, direct solar → thermal → chemical catalytic CO2 splitting processes are reviewed in Chapter 15.
Chapters 16–18 look from different angles at the electrochemical reduction of carbon dioxide. Chapter 19 discusses the application of microwaves in the catalytic dry reforming of methane. Chapters 20 and 21 analyse the use of different types of plasmas in CO2 conversion.
The part on biochemical CO2 valorisation consists of three contributions. Chapters 22 and 23 discuss enzymatic and microbial conversion, respectively, while Chapter 24 concentrates on hydrothermal CO2 reduction using biomass derivatives as reductants.
The final Chapter 25 presents the life cycle analysis aspects of CO2 valorisation.
We would like to express our gratitude to all the authors that have contributed to this book. Chemical valorisation of carbon dioxide is an important and challenging way to go. We hope that the book will fulfil its role of a comprehensive and up-to-date information source for readers in academia and industry alike.