Petroleum Products — Determination of base Number by Potentiometric

Release Time

2024-03-29 15:05


The REX Ti-50 Automatic Potential Titrator allows quick and simple determinations of the base number of petroleum products. The constituents that may be considered to have basic characteristics include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, and salts of heavy metals.

 

1.Standard Reference

ASTM D2896-21《Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration》

ASTM D2896-21 specifies a method for the determination of basic constituents in petroleum products by titration with perchloric acid in glacial acetic acid.

2.The Principle

This test method can be used to determine base number >300 mg KOH/g. However, the precision statement in Section 19 has been obtained only on base number ≤300 mg KOH/g.

 The sample is dissolved in an essentially anhydrous mixture of chlorobenzene and glacial acetic acid and titrated with a solution of perchloric acid in glacial acetic acid using potentiometric titrimeter. A glass indicating electrode and a reference electrode are used, the latter being connected with the sample solution by means of a salt bridge. The meter readings are plotted against the respective volumes of titrating solution, and the end point is taken at the inflection in the resulting curve.

Potentiometric Titrimeters, either automatic recording or manual.

Glass Electrode, pH 0 to 11, general-purpose type.

Reference Electrode, silver/silver chloride (Ag/AgCl) reference electrode with a nonaqueous bridge.

3.Recommended Configuration

  1. Ti-50 Automatic Potential Titrator 
    1. Range:(-2000.00~2000.00) mV
    2. mV Accuracy:±0.03% or ±0.2mV
    3. 1 extra burette driver can be installed (optional).
    4. Replaceable burette with high-accuracy (10 ml or 20 ml selectable).
    5. Support acid-base titration, non-aqueous aqueous phase titration, constant titration, REDOX titration, precipitation titration, complexation titration
    6. Support the following titration modes: DET (dynamic equivalence point titration), MET (monotone equivalence point titration), SET (Preset Endpoint Titration) and MAT (manual titration).
    7. Titration methods, curves and results are displayed in detail.

  1. Auxiliary titration unit 20mL
  2. Burette valve device 20mL (SC5.461.057)
  3. Anti-diffusion capillary
  4. Electrodes982211 Non Aqueous pH Titration Electrode

 

4. Titration Setting for forward titration

  1. Non-aqueous aqueous phase titration
  2. Sample: MET (monotone equivalence point titration)

Pre-adding(ml):1ml

Each adding (ml): 0.01ml

Equilibrium time3s

Max waiting of endpoint judgement (s): 10s

  1. Blank Sample: MET (monotone equivalence point titration)
  2. Titration curve

Calculate the base number, BN, as follows:

BN, mg KOH/g =【(E - F*NA *56.1/S

 

where:

E = HClO4 solution used to titrate the sample to the  inflection point on the titration curve, mL,

F = volume corresponding to E for blank titration at same potential as sample, mL

NA = normality of HClO4 solution, and

S = sample, g.

 

5.Titration Setting for back titration

Occasionally certain used oils give no inflection in the forward titration mode, in which case a back titration modification with sodium acetate titrant is employed.

 Some used oils give no inflection point or only a very poor one with forward titration. When this situation is encountered, the following modified test method may be used. In this modified test method, excess standard HClO4 solution is added to the sample, then the excess HClO4 solution is back titrated with standard sodium acetate solution

  1. Non-aqueous aqueous phase titration
  2. Sample: MET (monotone equivalence point titration)

Pre-adding(ml):2ml

Each adding (ml): 0.05ml

Equilibrium time20s

Max waiting of endpoint judgement (s): 20s

  1. Blank Sample: MET (monotone equivalence point titration)
  2. Titration curve

 

 Calculate the base number, BN, as follows:

BN, mg KOH/g =【(G - H)*NB *56.1/S

where:

G = volume of standard sodium acetate used in the standardization, mL

NB = normality of the sodium acetate solution,

H = volume of standard sodium acetate used in the sample back titration, mL, and

S = weight of sample, g.