Tributyl phosphate

Tributyl phosphate (TBP), n-tributyl phosphate, or tri-n-butyl phosphate, is an odorless liquid, colorless to pale yellow in appearance, with applications in industrial and nuclear chemistry. It is slightly flammable and moderately dangerous to humans. It is an ester of orthophosphoric acid and n-butanol. It is a very good solvent.

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History

Section pending.

Production

Tributyl phosphate is manufactured by esterification of orthophosphoric acid with butyl alcohol.

This is a high volume chemical with production estimated at 3,000 – 5,000 tonnes worldwide. [1]

Use

Industrial

TBP is a solvent and plasticizer for cellulose esters (eg. nitrocellulose and cellulose acetate). It forms stable hydrophobic complexes with some metals; these complex are soluble in organic solvents and in supercritical CO₂.

The major uses of TBP in industry are as a component of aircraft hydraulic fluid and as a solvent for extraction and purification of rare earth metals from their ores. [2]

TBP finds its use as a solvent in inks, synthetic resins, gums, adhesives (namely for veneer plywood) and herbicide and fungicide concentrates.

As it has no odour, together with a large amount of eg. isopropyl alcohol it finds use as anti-foaming agent in most detergent solutions, and in various emulsions, paints, and adhesives. It is also found as a defoamer in ethylene glycol-borax antifreze solutions.

In oil-based lubricants addition of TBP increases the oil film strength. It is used also in mercerizing liquids, where it improves their wetting properties.

It is also used as a heat exchange medium. [3]

Consumer Products

TBP is used in some consumer products such as herbicides and water thinned paints and tinting bases. [4]

Nuclear Chemistry

A 15-40% (usually about 30%) solution of tributyl phosphate in kerosene or dodecane is used in the liquid-liquid extraction (solvent extraction) of uranium, plutonium and thorium from spent uranium nuclear fuel rods dissolved in nitric acid, as part of a nuclear reprocessing process known as PUREX.

Because of this, the shipment of 20 tons of tributyl phosphate to North Korea from China in 2002, coinciding with the resumption of activity at Yongbyon Nuclear Scientific Research Center, was seen by the United States and the International Atomic Energy Agency as cause for concern; that amount was considered sufficient to extract enough material for perhaps three to five potential nuclear weapons.

Hazards

The material will burn, but (in the absence of significant vaporization) should not pose a particular explosive hazard. Inhalation and ingestion should be avoided due to possible central nervous system effects. A lab coat and safety glasses should be worn; a tributyl phosphate is not presently known to be, or suspected of being, a carcinogen, but may be mutagenic or have reproductive effects; consult the substance's MSDS for full details (see link at bottom).

In contact with concentrated nitric acid the TBP-kerosene solution forms hazardous and explosive red oil.

Sources

Material Safety Data Sheet (MSDS) for tributyl phosphate

See also

• Red oil