ABSTRACT
The search for new environmentally benign nonaqueous solvents, which can easily be recovered/ recycled, and the use of robust, selective, and ef- cient catalysts are two of the main goals for the development of green/ sustainable chemical processes [1]. Solvents are usually used as auxiliary materials in chemical synthesis, where they act as media for mass transport, reaction, and product separation. The vast majority of solvents used in academic and industrial laboratories are molecular liquids, belonging to the group of volatile organic compounds (VOCs). They are responsible for a large part of the environmental problems of processes in the chemical industry, and have a great impact on cost, safety, and health (e.g., toxic, ammable, or corrosive compounds). Furthermore, their recovery and
3.1 Introduction: Toward a green chemical industry .............................. 31 3.2 Biotransformations in nonaqueous environments ............................ 34 3.3 Ionic liquids and enzymes..................................................................... 38
3.3.1 Essential solvent properties of ionic liquids for biocatalysis ................................................................................... 38
3.3.2 Enzyme catalysis in ionic liquids ............................................. 40 3.3.3 Stability and stabilization of enzymes in ionic liquids ......... 44
3.4 Green biocatalytic processes with downstream ................................. 46 3.4.1 Enzymatic membrane reactor based on ILs ............................ 47 3.4.2 Bioprocesses in IL/ supercritical carbon dioxide biphasic
systems ......................................................................................... 48 3.4.3 Bioprocesses in sponge-like ILs ................................................ 55
3.5 Prospects .................................................................................................. 57 Acknowledgments ........................................................................................... 58 References .......................................................................................................... 58
reuse are often associated with energy-intensive distillation and sometimes cross-contamination. The substitution or elimination of VOCs is not an easy task, because they are key elements for chemical processes (e.g., dilution of the reactants or the catalysts; to provide an environment where reactants meet, assistance for the homogeneous distribution of the energy needed for the reaction activation, or dissipation of the energy generated by an exothermal reaction; effects on performance of the catalysts; to facilitate product separation by changes in product solubility; etc.) [2].
