Supercritical Carbon Dioxide as a Green Solvent
Supercritical Carbon Dioxide as a Green Solvent
Gregory Absillis
June 2009
The majority of chemical processes in chemical synthesis are carried out in solution and organic solvents usually are the first choice. To satisfy this demand, 15 billion kilograms of organic are produced worldwide each year. [1] These solvents often bear considerable risk due to their toxicity, flammability or environmental hazards. Furthermore, they have to be separated from the products and recycled or disposed at the end of the process, increasing the overall production cost. Although they play a valuable role, organic solvents are responsible for significant air, soil and water pollution. One important effort in the development of environmentally friendly chemical processes is the reduction of solvent use through the development of solvent-free processes and more efficient recycling protocols. Since most of these approaches necessitate a pollution prevention program the replacement of organic solvents by environmentally benign reaction media is preferred. Ionic liquids, fluorous biphase systems and water are currently being studied as solvent alternatives. Another actively studied alternative is supercritical carbon dioxide (spCO2). All have potential benefits and disadvantages that need to be considered. [13]
Although supercritical fluids are known since the discovery of the critical temperature 175 years ago, their use as reaction media for organic synthesis emerged only during the last 1015 years. Especially the use of scCO2 as a solvent for selective extraction and synthesis processes attracts considerable interest. Not only is scCO2 used in diverse areas as dry cleaning, dying of fabrics and polymers, metal degreasing and material processing, its application in food chemistry is nowadays even more established. The main commercial example is the production of decaffeinated coffee. [4] This paper aims to analyze the use of scCO2 as a decaffeinating agent for coffee beans
Gregory Absillis
June 2009
The majority of chemical processes in chemical synthesis are carried out in solution and organic solvents usually are the first choice. To satisfy this demand, 15 billion kilograms of organic are produced worldwide each year. [1] These solvents often bear considerable risk due to their toxicity, flammability or environmental hazards. Furthermore, they have to be separated from the products and recycled or disposed at the end of the process, increasing the overall production cost. Although they play a valuable role, organic solvents are responsible for significant air, soil and water pollution. One important effort in the development of environmentally friendly chemical processes is the reduction of solvent use through the development of solvent-free processes and more efficient recycling protocols. Since most of these approaches necessitate a pollution prevention program the replacement of organic solvents by environmentally benign reaction media is preferred. Ionic liquids, fluorous biphase systems and water are currently being studied as solvent alternatives. Another actively studied alternative is supercritical carbon dioxide (spCO2). All have potential benefits and disadvantages that need to be considered. [13]
Although supercritical fluids are known since the discovery of the critical temperature 175 years ago, their use as reaction media for organic synthesis emerged only during the last 1015 years. Especially the use of scCO2 as a solvent for selective extraction and synthesis processes attracts considerable interest. Not only is scCO2 used in diverse areas as dry cleaning, dying of fabrics and polymers, metal degreasing and material processing, its application in food chemistry is nowadays even more established. The main commercial example is the production of decaffeinated coffee. [4] This paper aims to analyze the use of scCO2 as a decaffeinating agent for coffee beans
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