Supported Silicotungstic Acid Catalyst for Catalysis of Tetrahydrofuran

Tetrahydrofuran is a kind of low toxic solvent with high polarity and low boiling point. It is widely used in surface coatings, anticorrosive coatings and film coatings. Its main uses are polytetramethylene ether glycol (PTMEG), polyurethane elastomer and polyurethane artificial leather. It is also used as a solvent in esterification and polymerization to synthesize some hormone drugs in medicine.

Furfural method is mainly used to produce tetrahydrofuran in China. This method consumes more raw materials, has complex process, small scale, low output and serious environmental pollution. The preparation of tetrahydrofuran by liquid phase cyclization dehydration of 1,4-butanediol with phosphoric acid/sulphuric acid as catalyst is simple and has high catalytic activity, but phosphoric acid/sulphuric acid corrodes the equipment seriously, and the liquid acid catalyst and product separation are difficult to pollute the environment.

Some researchers have proposed a supported silicotungstic acid catalyst, which can solve the drawbacks of environmental pollution. The preparation of this catalyst needs kaolin as carrier.

The preparation process of the catalyst: dissolve silicotungstic acid in distilled water, make the volume of silicotungstic acid solution equal to the pore volume of the carrier, and impregnate it on the carrier (i.e. equal pore volume impregnation method). The carrier is kaolin, calcined at 120-220 ℃ for 2-6 hours, and stirred every 20-40 minutes during the calcination process to make the silicotungstic acid uniformly loaded on the carrier. The content of Silicotungstic Acid in the catalyst is the mass ratio of Silicotungstic Acid in impregnating solution to that of impregnated kaolin. The mass percentage of Silicotungstic Acid in the prepared catalyst is between 5% and 25%.

Test method of catalyst activity: 1,4-butanediol of 150 ml was heated to boil at 230 ~℃ and 0.5g catalyst was added to react. With the reaction proceeding, the concentration of 1,4-butanediol and tetrahydrofuran in the product and reactant of distillation was analyzed by gas chromatography, and the conversion and selectivity were calculated. Finally, it was concluded that the reaction time of kaolin containing 5% silicotungstic acid was 180%. The conversion and selectivity of minute catalyst are higher than 95%.

Therefore, the supported silicotungstic acid catalyst has good catalytic activity for the cyclization and dehydration of 1,4-butanediol to prepare tetrahydrofuran, which is pollution-free, low cost and high efficiency.

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