The object of this study was to determine the kinetics and mechanism of the autocatalytic hydrolysis of tri-n-butylphosphate (TBP) in a hydrocarbon diluent (odourless kerosene (OK) or n-dodecane) by concentrated aqueous sodium hydroxide, typically 8.5 mol.dm<SUP>-3</SUP>. The reaction products are sodium dibutylphosphate (NaDBP) and butanol. Specific attention was paid to the formation of a third liquid phase during the reaction, the induction and autocatalytic periods of the reaction, and the importance of sodium hydroxide concentration. The induction period is shown to be the result of a homogeneous hydrolysis in the aqueous phase prior to third phase formation and the relevant second order homogeneous rate constants are determined. The NaDBP formed during this period is shown to be solubilised in both the organic and aqueous phases, the solubility of NaDBP in the TBP/diluent phase having a marked dependence on the phase composition. This dependence is speculated to be due to the formation of inverse micelles of NaDBP. Once these two phases are saturated with NaDBP the third phase is formed and autocatalysis begins. At low hydroxide concentrations no third phase is formed, all the NaDBP formed being solubilised in the aqueous phase and therefore no autocatalysis is observed. It is shown that the formation of the third phase eliminates the induction period and provides a homogeneous reaction solvent in which both reactants dissolve, the reaction being first order in both hydroxide ion and TBP, the second order homogeneous rate constants being determined. A simplistic kinetic model for the autocatalytic period of the reaction is presented and used in a computer simulation. The agreement between the simulated and experimentally observed data is discussed. NMR analysis is used to study the change in middle phase composition during the reaction. Further NMR studies on samples provided from the industrial process currently being used show that after six hours significant amounts of secondary hydrolysis occur forming sodium monobutylphosphate (Na<SUB>2</SUB>MBP).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636178 |
| Date | January 1995 |
| Creators | Burgess, D. J. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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