Many reactions, extractions, separations and other operations in the chemical process industries (CPI) involve the use of organic solvents. In addition to handling and disposal issues, organic solvents can pose a number of environmental concerns, such as atmospheric and land toxicity. In many cases, conventional organic solvents are regulated as volatile organic compounds (VOCs). In addition, certain organic solvents are under restriction due to their ozone-layer-depletion potential.
Supercritical carbon dioxide is an attractive alternative in place of traditional organic solvents. CO2 is not considered a VOC. Although CO2 is a greenhouse gas, if it is withdrawn from the environment, used in a process, and then returned to the environment, it does not contribute to the greenhouse effect. There have been an increasing number of commercialized and potential applications for supercritical fluids. This article summarizes the fundamentals of supercritical CO2 properties and processing, and presents a number of current and potential applications.
Above its critical values, a compound’s liquid-vapor phase boundary no longer exists and its fluid properties can be tuned by adjusting the pressure or temperature.…