The production of CO2 by burning is harmful to the environment and adds to the Green House effect. However, using existing carbon dioxide can lead to some environmental benefits. For example we’re not creating any CO2 when we put bubbles into our soft drinks. We’re using existing carbon dioxide when this is done.
We can use existing carbon dioxide as a solvent instead of many of the harsh petroleum based solvents, that would ultimately need to be disposed of. Carbon dioxide is a very non polar solvent and we can make it behave very much like hexane or heptane. Those solvents have a myriad of uses.
When we use carbon dioxide as a solvent we very often recycle it and use it over and over again. It is “cleaned” going from a liquid to a gas, back to a liquid. So, there is no net increase in the amount of CO2 in the environment.
We can use carbon dioxide as a liquid for many applications… But we can increase its range of uses tremendously, if we increase the temperature and pressure above 31C and 72 BAR, above the supercritical point. By increasing the temperature and pressure above this point, we increase CO2’s solvent capabilities immensely. By manipulating the pressure of the CO2 above its supercritical point, we can make the ”solvent” behave like a myriad of petroleum based solvents, but without the deleterious environmental impact.
By increasing the pressure of the CO2 in the supercritical range, we can make it simulate more and more polar solvents. This changes the solvating characteristics and allows us to fractionate.
So, in distillation, one fractionates by manipulating boiling points. However, when using supercritical carbon dioxide, instead of boiling points, one fractionates by manipulating the pressure to dissolve or precipitate compounds in or out of the solution.
Stay tuned for more about supercritical fluids.
Carbon Dioxide Gets a Bad Rap Sometimes.
