Tetrahydrofuran (also known as tetramethylene oxide, and THF) is a clear, colourless, volatile, and water-miscible liquid. It has low viscosity at standard temperature and has the formula C4H8O.
Tetrahydrofuran was traditionally produced using the Furfural process where furfural, extracted from corn husks, is used as the raw material in production. However, the disadvantage of this method is that supply depended on agricultural conditions and, could not therefore be relied upon, so a move was made to the fully synthetic Reppe process.
In the Reppe process, ethyne and formaldehyde are used as the raw materials that produce 1,4 butanediol, at the first step. Tetrahydrofuran can then be obtained by dehydration under the existence of an acidic ion exchange resin. This is currently the main method of extraction employed throughout the world.
Another method is a butadiene chlorination process but the method most likely to be employed in the future is one that was developed by DuPont. This involves oxidising n-butane to create maleic anhydride and this is then followed by catalytic hydrogenation. It is a relatively simple process and one that is of interest to chemical producers.
The world annual production of tetrahydrofuran is approximately 200,000 tonnes and it is predicted that demand and production will grow as the Chinese economy continues to expand.
Storage and Distribution
Tetrahydrofuran is stored in tightly sealed metal drums and/or amber glass containers. It has a specific gravity of 0.89 and a flashpoint of -17.2° C (closed cup) and is highly flammable. It should be stored in a cool, dry, and well-ventilated area that is free from the risk of ignition. For transportation purposes, tetrahydrofuran is classified as packing group III and hazard class 3 and should be labeled as an irritant.
Tetrahydrofuran has many uses in the industrial marketplace. It is a versatile industrial solvent for natural and synthetic resins and is a solvent used in the production of nylon. It is also an industrial solvent for PVC.
Tetrahydrofuran is also a valuable chemical intermediate as it is a precursor to polymers, such as poly (tetramethylene ether) glycol. The primary use of this polymer is the production of elastomeric polyurethane fibres like Spandex. It is also an intermediate in the natural gas industry where it is a natural gas odourant.
It is also used as a reaction medium, primarily in the pharmaceutical industry, in processes such as Grignard syntheses or lithium aluminium hydride reductions.