Tributyl phosphate

Tributyl phosphate, known commonly as TBP, is an organophosphorus compound with the chemical formula (CH3CH2CH2CH2O)3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of phosphoric acid with n-butanol.

Tributyl phosphate
Spacefill model of Tributyl phosphate
Ball and stick model of Tributyl phosphate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.004.365
KEGG
UNII
Properties
C12H27O4P
Molar mass 266.318 g·mol−1
Appearance Colorless to pale-yellow liquid[1]
Density 0.9727 g/mL
Melting point −80 °C (−112 °F; 193 K)
Boiling point 289 °C (552 °F; 562 K)
0.4 g/L[2]
Vapor pressure 0.004 mmHg (25°C)[1]
Hazards
Safety data sheet External MSDS
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
1
2
1
Flash point 146.1 °C (295.0 °F; 419.2 K)
Lethal dose or concentration (LD, LC):
1189 mg/kg (mouse, oral)
3000 mg/kg (rat, oral)[3]
227 ppm (cat, 4–5 h)
123 ppm (rat, 6 h)
117 ppm (rat)
2529 ppm (rat, 1 h)[3]
2214 ppm (cat, 5 h)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 5 mg/m3[1]
REL (Recommended)
 TWA 0.2 ppm (2.5 mg/m3)[1]
IDLH (Immediate danger)
 30 ppm[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Production

Tributyl phosphate is manufactured by reaction of phosphoryl chloride with n-butanol.[4]

POCl3 + 3 C4H9OH → PO(OC4H9)3 + 3 HCl

Production is estimated at 3,000–5,000 tonnes worldwide.[5]

Use

TBP is a solvent and plasticizer for cellulose esters such as nitrocellulose and cellulose acetate. It forms stable hydrophobic complexes with some metals; these complexes are soluble in organic solvents as well as supercritical CO2. The major uses of TBP in industry are as a component of aircraft hydraulic fluid, brake fluid, and as a solvent for extraction and purification of rare-earth metals from their ores.[5]

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, it is used as an anti-foaming agent in detergent solutions, and in various emulsions, paints, and adhesives. It is also found as a de-foamer in ethylene glycol-borax antifreeze 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 can be used as a heat-exchange medium.[6] TBP is used in some consumer products such as herbicides and water-thinned paints and tinting bases.[7]

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.

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.[8]

Hazards

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

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References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0625". National Institute for Occupational Safety and Health (NIOSH).
  2. Velavendan, P; Sachithanantham, Ganesh; Pandey, N.K.; Geetha, R; Ahmed, M; Mudali, Kamachi; Natarajan, Rajamani (2012). "Studies on solubility of TBP in aqueous solutions of fuel reprocessing". Journal of Radioanalytical and Nuclear Chemistry. 295 (2): 1113–1117. doi:10.1007/s10967-012-1945-1.
  3. "Tributyl phosphate". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. G. R. Dutton and C. R. Noller (1943). "n-Butyl phosphate". Organic Syntheses.; Collective Volume, 2, p. 109
  5. "Tributyl Phosphate | SIDS Initial Assessment Profile" (PDF). Japan Chemical Industry Ecology-Toxicology & Information Center. Archived from the original (PDF) on 2007-10-11.
  6. "Tributyl Phosphate Product Information". Great Vista Chemicals.
  7. "Tributyl Phosphate". Scorecard.
  8. "Yongbyon - North Korean Special Weapons Facilities". GlobalSecurity.org.
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