The VSPP set up at HWP-Talcher is intended for synthesis of D2EHPA, TOPO, TAPO & DNPPA. In the synthesis of D2EHPA, the entire process is divided into two Groups of operations. Each group operation is carried out in series in two different Reactors. The first set of operations consists of the operation steps 1 & 2 i.e. up to chlorination of DOP and is carried out in the 1st Reactor. After processing as above, the same charge is transferred into 2nd Reactor to take up second set of operation i.e. steps 3 to 5.

The first Reactor is then made ready to take up first set of operation of the next batch parallel with the operation of second Reactor for 1st batch.

The Synthesis process involves mainly five steps as given below:

• Esterification reaction between phosphorous tri-chloride (PCl₃) and 2-Ethyl Hexanol (ROH) to produce the first intermediate Di- Octyl Phosphite (DOP).
  Raw Materials used:
  • Phosphorous tri-chloride (PCl₃)
  • Ethyl Hexanol (ROH) (R = C₈H₁₇)

  Reaction medium : n-Hexane

  Reaction involved

  PCl₃(l) + 3ROH(l) ---------> (RO)₂(O)H(l) + RCl(l) + 2HCl(g)

  (Di-Octyl Phosphite, DOP)

  R = C₈H₁₇ ( 2 Ethyl Hexyl radical )

• Chlorination (Oxidation) of the DOP formed in the first step with Chlorine gas to from the second intermediate Di-Octyl Phosphochloridate(DOPC).
  Raw Materials used:
  • DOP from Step.1
  • Chlorine
  Reaction involved

  (RO)₂(O)H (l) + Cl₂ (g) ---------> (RO)₂(O)Cl (l) + HCl (g)

  (Di-Octyl Phosphochloridate)

  R = C₈H₁₇ (2 Ethyl Hexyl radical)

• Hydrolysis of the DOPC formed in 2nd step with Sodium Hydroxide solution (NaOH) to form raw D2EHPA.
  Raw Materials used:
  • D-Octyl Phosphochloridate from step 2
  • 2. Aqueous NaOH solution
  Reaction involved

  (RO)₂(O)Cl (l) + NaOH ---------> (RO)₂(P)(O)OH + NaCl (aq)

  (D2EHPA)

  R = C₈H₁₇ (2 – Ethyl Hexyl radical)

• Water / dilute alkali washing of the raw product to remove undesirable impurities.
• Final purification by vacuum distillation to obtain the product of desired quality.