Alternatives to Traditional Thermal Distillation

Distillation of organic solvents is a necessary part of academic research.  Typically, researchers use the distillation process to remove water, oxygen, and other contaminants from organic solvents.  This process can be hazardous for several reasons:

• Reactive metals are used as drying agents
• Many organic solvents are flammable, and the heat required in the distillation process can present a fire hazard
• Flasks have to be cleaned at regular intervals
• The distillation process takes place over several hours.  So, at times, the distillation unit is left  unattended
• The remaining drying agent may need to be     neutralized and disposed of as hazardous waste

In 2003, the American Chemical Society (ACS) published a journal article on alternatives to solvent purification.  The ACS suggested solvent purification processing systems as cost-effective alternatives to the traditional thermal still.

The solvent purification systems use stainless steel columns    to retain the solvent.  Dry argon gas is used to force the solvent over columns that contain activated alumina and copper catalyst.  The alumina removes the water and the copper catalyst removes the oxygen.

Initially, the commercial purification column has a higher cost, but the article suggests that the annual operating costs are lower because larger volumes of solvent can be purified by one column.  Additionally, the authors suggest that the solvent purification system is more effective than the traditional thermal still for other reasons:

1. The quality of the solvent purification system meets the tests for removing water, oxygen, and peroxide contaminants.
2. Solvent purification systems have automatic controls that shut down the system if overheating occurs.
3. More than one column can be purchased to allow purification of more than one solvent at a time.
4. The purification system operates at room temperature.  Heat is not required to purify the solvent.

The following table includes data from the article that compares the set up costs, operational costs, and solvent purity for the solvent still and purification column.

The distillation process will continue to be an important aspect of research. Since the process may require the use of reactive metals and heat, less hazardous alternatives should be considered. The column purification system could be a reasonable, cost-effective alternative to this necessary process.

References:

Cournoyer, Michael E. and Dare, Jeffrey H., “The Use of Alternative Solvent Purification Techniques,” Journal of Chemical Health and Safety [online] 2003, July/August, 15-18.

Grubbs, Robert H., et. al, “Safe and Convenient Procedure for Solvent Purification,” Organometallics 1996, 15, 1518-1520.