TABLE OF CONTENTS Organic solvents have played a key role in the development of many useful products. They are used, for example, to produce pharmaceuticals of the required purity, to ensure the easy flow and good finish of gloss paints, to formulate inks that dry successfully, and in aerosol applications. In the latter three consumer applications all the solvent is lost to the atmosphere whereas in industrial applications 'end-of-pipe' solutions can be installed to recover much of the solvent for reuse or safe disposal, and for energy recovery. In chemical manufacture, organic solvents are widely used in a variety of unit operations including extraction, recrystallization and the dissolution of solids for ease of handling. One of the key roles organic solvents play in the chemical industry, however, is that of reactant solvent allowing the homogenization of a reactant mixture, speeding up reactions through improved mixing, and in addition reducing energy consumption. Solvents also contribute to safety by acting as a heat sink for exothermic reactions. Many of the applications discussed above use volatile organic compounds (VOCs) as solvents because of their ease of removal or evaporation. VOCs have a significant vapour pressure at room temperature and are released from many sources including process industries and most forms of transport, the latter being responsible for the majority of VOC emissions.
The main environmental issue concerned with VOCs is their ability to form low-level ozone and smog through free radical air oxidation processes. The EPA has published a...
