Synthesis of Tetrahydrofuran

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Synthesis of Tetrahydrofuran

Post  yufei on Tue Jun 21, 2011 4:08 pm

Tetrahydrofuran (simplified as THF) is a kind of colorless liquid with a taste similar to that of ethyl ether. It can be dissolved in water and many other organic solvents. It is venenous with the maximum permissible concentration in the air reaching 200 multiply 10-6. As one of the strongest polar ethers, tetrahydrofuran can be used as a solvent with medium polarity in the process of chemical reactions and extraction. Because of its wide usage as an important organic synthetic raw material and a fine solvent, tetrahydrofuran is still called “alcahest”. In addition, it can be considered as raw material for organic chemical industry and fine chemical industry and is widely used in resinsolvent, reactive solvent, chemical intermediate and chromatographic solvent.

There are four composite methods for tetrahydrofuran production, namely, furfural extraction process, Reppe process, butadiene chlorination process and MAH hydrogenation process.

Furfural extraction process: in the process, various agricultural wastes including corn cobs, oat hulls and bagasses can be used as raw materials and are boiled in dilute H2SO4 to hydrolyze their pentosan into pentose. After the process of dehydration, pentose can be conversed into furfural. With ZnO、Cr2O3 and MnO2 as catalysts, furfural can be separated from carbonyl in water vapour at 40O℃ and then furan is produced. With nickel as catalyst, furan can produce tetrahydrofuran through hydrogenation at 80℃. Furfural extraction process created by Du Pont Company is the oldest method to produce tetrahydrofuran. In 1992, the first set of industrial equipment adopting the process put into operation.

Reppe process: the process was invented by the cooperation of IG Company in German with Doctor Reppe. It takes formaldehyde and ethyne as raw materials to produce 1, 4-butanediol at first step. Under the existence of acidic ion exchange resin, tetrahydrofuran can be obtained through dehydration. This is the main method to produce tetrahydrofuran all over the world.

Butadiene chlorination process: this method chloridizes butadiene into the mixture of 3, 4- and 1, 4- dichlorobutylene. After the separation of hydrogen cyanide, 3, 4- dichlorobutylene can be conversed into chloroprene which can be used as monomer component for neoprene production. With PCA-Na as catalyst at 110℃ under normal pressure, 1, 4- dichlorobutylene can be conversed into 1, 4- butanediol and further into tetrahydrofuran.

MAH hydrogenation process: the process was first invented by Du Pont Company. It makes use of NiMoOx、Co-MoOx and NixCrOy as catalysts and conducts liquidi phase hydrogenation under 78MPa. However, because of high reaction pressure, large catalysts dosage and large production cost, Du Pont Company did not realize industrial production through this method. In 1960s, the method was improved using copper catalyst. The new method can produce tetrahydrofuran through gas phase hydrogenation at 250℃ with pressure lower than 3,9MPa. This method has many advantages. For example, the source of raw materials is rather rich with a low price. In addition, the process of operation is relatively simple and the production cost has been reduced much. Many institutes in our country have already paid great attention to the method, such as Research Institute of Petroleum Processing.

yufei

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