Combustible ionic liquids by design: is laboratory safety another ionic liquid myth?

Area of Science:

• Chemistry
• Materials Science
• Chemical Engineering

Background:

• Ionic liquids (ILs) are frequently promoted for their non-flammability, a perceived advantage over volatile organic compounds (VOCs).
• This perception of inherent safety may lead to complacency when handling ILs near thermal hazards.
• However, the flammability of ILs is a complex issue influenced by their chemical structure and thermal behavior.

Purpose of the Study:

• To critically evaluate the safety claims regarding the non-flammability of ionic liquids.
• To identify the factors contributing to the combustibility of certain ionic liquids.
• To inform safer handling practices for ionic liquids in various applications.

Main Methods:

• Analysis of the heats of formation for various ionic liquids.
• Assessment of oxygen content in ionic liquid structures.
• Investigation of decomposition products generated under thermal stress.

Main Results:

• A significant number of ionic liquids, including commercially available ones, possess positive heats of formation, indicating inherent instability.
• The presence of oxygen in the molecular structure of some ILs contributes to their combustibility.
• Decomposition of ILs can generate flammable or toxic byproducts, increasing fire risks.

Conclusions:

• The non-flammability of ionic liquids is not a universal characteristic and should not be assumed.
• Combustibility risks are associated with specific chemical properties like positive heats of formation and oxygen content.
• Careful assessment of IL properties and handling procedures near heat sources are crucial for ensuring safety.