Supercritical Carbon Dioxide as Green Solvent
Carbon dioxide is a readily available, cheap, recyclable and is non-toxic and non-flammable. Above the temperature of 31. 6 oC and pressure of 73 atm carbon dioxide exhibits physical properties, which are intermediate between those of gases and liquids. These conditions are called supercritical conditions and are readily achievable using commercially available equipment. Supercritical carbon dioxide is able to dissolve a range of chemical substances including organic substrates, catalysts, and light gases.
Its main advantage however comes from the fact that this solvent can be easily turned into a gas by simply releasing the pressure leaving no solvent residues and requiring no evaporation or separation. As such it is widely used as an alternative to conventional solvents with numerous applications such as: extraction and purification of specialty chemicals and useful natural products, an alternative solvent in coatings industry, (replacing 40-90% of volatile solvents), degreasing and dry cleaning applications.
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It is also increasingly applied as a solvents in synthetic industrial processes. Green Chemistry Centre of Excellence for Industry has extensively explored the application of this solvent in extraction of valuable natural products or high tech materials, in development of novel materials and in clean organic synthesis. We have also explored the application of this solvent in biologically catalysed reactions and worked on development of homogeneous catalysts soluble in supercritical carbon dioxide.
Supercritical Carbon Dioxide in Organic Synthesis Researchers at the Green Chemistry Centre of Excellence for Industry have developed novel synthetic reactions, which in conventional solvents give mixtures of products, but in supercritical carbon dioxide yielded just a single product. This is due to unique tunable properties of supercritical fluids allowing much greater control over reactions than is possible with conventional solvents, and enabling fine-tuning of the solvent properties to favour one particular pathway.
Such control over reaction selectivity is remarkable, and clearly demonstrates the potential of supercritical carbon dioxide as a reaction medium. Benefits of using the Green Chemistry Centre of Excellence for Industry: Applied a clean solvent Improved control and fine-tuning of process Developed a remarkably selective synthetic process for industrially important synthetic reactions Minimised waste Increased atom utilisation Minimised handling and purification procedures Alternative Solvents: Supercritical CO2 – Chemistry, The University o… http://www. york. ac. uk/chemistry/research/green/industry/casestudies/co2/ 1