Total Acid Number In Crude Oils

Question 1

PH Calibration

Answer 1

A pH calibration should be completed before each sample batch or and standards are analyzed.

1. Select workplace icon
2. Determination series tab
3. Select sample table, and load pH calibration table
4. Place 4.00, 7.00, and 10.00 buffers into plastic titration cups in 1,2, and 3rd positions.
5. Place cup of 100mL pure DI water with 2 drops of acidified (10% HCl) water in position 12 and start sequence.
   Acceptable slope=95-105

Question 2

Prepare Samples

Answer 2

• Crude oil samples shake for 2 minutes, venting periodically
• Place clean titration cup in scale and rare.
• Add 20 mL of sample to titration cup and record weight to nearest 0.1 mg
• Add 125mL TAN to titration cup, and repeat for second sample placing in 5&6.
• For heavier samples (API gravity of

Question 3

Prepare Standards (Stds)

Answer 3

• Place clean titration cup in balance and rare.
• Add 20 mL of acid number std to titration cup and record weight to nearest 0.1mg
• Add 125 mL of TAN to titration cup and place in position 3. Repeat and place in position 4 for 2nd std

Question 4

Prepare blanks

Answer 4

• All blanks, stds, and samples run in duplicate.
• Blanks prepared by adding 125mL of Neutralization Number Solution (TAN) to plastic titration cup
• place blanks in 1 and 2
• Blanks run for each batch of samples or new solvent. Second blank value will be saved for formula. Blank should be below 0.5mL
• If 2nd blank dials to register an endpoint, one can be manually entered by opening graph and adding endpoint
• variable for blank will need to be modified for each sample if 2nd blank is not good

Question 5

Program Instrument

Answer 5

• Workplace>Determination Series>Sample Table>load>and select Acid number table
• double click each sample to edit weight and click apply
• make sure 145mL of 2-propanol is in position 11, 145mL of toluene in 10, and acidized water from pH step in 12.

Question 6

Data Analysis

Answer 6

• endpoint for acid # is approximately -275 mV
• if multiple endpoints, use accurate blank and sample data taken closest to -275 mV
• software will calculate, however if necessary here is formula

Question 7

Purpose

Answer 7

Analyze products and lubricants for acidic constituents. May be used to indicate relative changes occurring in oil during use under oxidizing conditions regardless of color or properties of resulting oil. Test not for absolute acidic property that can be used to predict performance of oil under service conditions. No general relationship between corrosion and acid number is known. However, this number can indicate how corrosive the material is to crude unit.

Question 8

QC std

Answer 8

To make:
• Add 5 mL glacial acetic acid to 2000mL volumetric flask. Fill flask to line with plant 4 kerosene and mix well. This is stock solution
• From stock solution, remove 50mL and place in 1000mL volumetric flask (this becomes 1:8000). Fill flask to line with plt 4 kerosene and mix well, this is std

Question 9

Troubleshoot

Answer 9

Check correct probe
•Run pH cal if operation of probe is in question (required slope=95-105)
• clean probe with toluene and DI water
• freshen inner storage solution (probe) (Tetraethyl ammonium bromide)
If new probe in service, empty LiCl solution from probe, rinse with DI water and rinse/fill with Tetraethyl ammonium bromide
Check Titrant
• Check 0.1 N potassium hydroxide exchange unit is connected to 805 dosimat
•Visually confirm there are no air bubbles in Titrant buret. If bubbles dose entire buret and refill 2 times, until bubbles are dosedz
Tiamo Software
•verify end points were identified correctly
•verify correct sample table loaded
•verify correct weights entered