Preface Free

The use of pressurised-solvent systems is becoming ever-more important, especially with the growing legislation restricting the use of conventional organic solvents in industrial chemical processes, as well as the strict guidelines for minimal solvent residues in consumer products. The use of high-pressure systems enables the possibility to design clean, sustainable and environmentally friendly processes, as well as generate novel products with unique properties. The use of supercritical fluids and also pressurised solvent systems is of global interest for use in extraction, reaction and materials processing. The motivation for this book is to have an in-depth overview of the latest research in the field of high pressure solvent systems: the current status, advances and developments that have been carried out in the past few years, as well as the limitations and drawbacks that need to be addressed.

The scope of the book is to explore the range and utility of high-pressure solvent systems in a variety of different chemical applications, from extraction and fractionation to reactions, separations (chromatography) and material processing. The book brings together recent advances in supercritical technology (both from a chemical as well as engineering perspective) and other pressurised-solvent systems such as superheated water technology and gas-expanded liquids. Wherever possible, the greenness and economic viability of the different solvent systems have been highlighted. This book should appeal to industrialists, academics, postgraduate and undergraduate students alike.

The authors have been carefully selected from around the world, including contributors from Europe, North America, Asia and South America. Some highlights of this book include a number of important areas including the following.

This book not only introduces the subject of pressurised-solvent systems and discusses the increasing importance of their use in industrial applications but it touches on the social, environmental and political drivers for utilising these solvent systems in comparison to conventional organic solvents. It also highlights the potential new opportunities for pressurised-solvent systems.

The use of supercritical carbon dioxide (scCO₂) as a solvent for the extraction of hydrophobic molecules from plant materials (namely agricultural residues and food waste) will be described including extraction of waxes, essential oils, bioactive metabolites etc., which are utilised in a host of applications ranging from cosmetics, nutraceuticals and pharmaceuticals to detergents, lubricants coatings, etc. A comparison with conventional solvent extraction systems will be presented.

scCO₂ has been used in the advanced processing and synthesis of green materials, both as a solvent and an anti-solvent. Examples of experimental set-ups from the literature will be cited and the processing of materials such as powders, coatings, films, aerogels, etc. will be discussed. This book will also discuss the developments in polymer research within supercritical fluids over the past few years.

Despite nearly 30 years of investigation, supercritical fluids are still regarded as an emerging field for electrochemical processes. Various aspects of electrochemical studies and processes such as electrodeposition and voltammetry in supercritical fluids will be discussed.

Gas-expanded liquids (GXLs) are emerging as promising solvents for a range of applications including reactions, extractions and separations. The most commonly utilised GXLs are CO₂-expanded liquids (CXLs), and various applications of GXLs are highlighted.

Other aspects of research covered in this book include catalysis in supercritical solvents, use of pressurised systems for the deconstruction of biomass, and also power generation with supercritical fluids.

The editors would like to thank their families and friends for their continuous support during the preparation of this book. Dr Hunt would like to especially thank his wife for her love and support. Dr Attard would like to especially thank his mother, father, Joseph and Sophie.

The editors hope that you find this book informative and interesting.

Andrew J. Hunt, Khon Kaen University, Thailand Thomas M. Attard, University of York, UK