Modern Trends in Solvent Use
There are many different solvents in use across the majority of the chemical manufacturing industries, particularly for the production of fine chemicals. The reason for this is the large number of beneficial roles a solvent can perform in a process or product. These benefits extend to extraction and separation processes, formulations, and cleaning products. The solvent must also be compatible with the materials it comes into contact with; use of several chemical functionalities often leads to corrosion or reactivity. In some instances, a volatile solvent is required, but at other times a non-volatile solvent is needed for environmental reasons, or perhaps a reaction must be performed at high temperature in the liquid phase or a substrate with a high melting point needs to be softened or melted. Other important physical properties include viscosity, vapour pressure, water solubility, density and surface tension. On top of this, health and safety principles may rule out solvents that are popular because of their versatility, price, and broad solvency power. This means many different types of solvent are used, and the favoured solvents within different sectors evolve over time. To illustrate the (changing) uses of solvents in synthesis and manufacturing, pharmaceuticals, polymers, materials, and biomass processing are all discussed. In addition, summaries of solvent use in formulations, and cleaning applications of solvents, are also provided.