DuPont brings innovative THF technology onstream

02 September 1996 00:00  [Source: ICB]

A new low cost clean technology for the production of tetrahydrofuran (THF) from butane will be brought onstream by DuPont by the end of the year, at its Asturias plant in Spain.

The new process contains three important innovations: the use of a circulating fluidised bed (CFB) for partial oxidation of n-butane; attrition-resistant catalyst particles for use in the CFB, and the development of a highly selective catalyst for the hydrogenation of maleic acid to THF.

Butane is converted to maleic anhydride, which is then absorbed in water to form maleic acid. The crude maleic acid is catalytically hydrogenated to THF, which is recovered after extractive distillation.

DuPont says the use of the CFB makes the process superior to fixed-bed and conventional fluidised bed reactors. CFBs are particularly suitable for processes incorporating fast reactions requiring reversible catalysts deactivation, or reactions where an intermediate product is desired.

However, CFBs can cause higher rates of particle attrition. To overcome this DuPont used vanadium phosphorus oxides, normally used for butane oxidation, encapsulated in a microporous silica shell. According to DuPont, these exhibited three times the attrition resistance of commercial fluid catalytic cracking catalysts in standard tests.

The final innovation is the development of a selective catalyst for the hydrogenation of maleic acid to THF, 1,4-butanediol or to mixtures of the two, according to the conditions within the reactor. The catalyst contains 1-6% palladium and 3-6% rhenium by weight, deposited on carbon substrates. The catalysts give a 100% conversion of reactants and DuPont says the ratio of THF to 1,4-butanediol can be controlled easily.

The output of the 45 000 tonne/year Asturias plant will be used to make polymethylene ether glycol (PMTEG) for the production of Spandex fibres and elastomers, at a plant in the Netherlands.

A second new process to convert THF to Terathane (PTMEG) will be used at plants under construction at LaPorte, Texas, and at Ulsan, Korea. The 20 000 tonne/year plant at LaPorte is due onstream Q1 1997 while the 30 000 tonne/year plant at Ulsan is due onstream Q4 1998.

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