Acid number In Petroleum Products

Question 1

Procedure A (unsweetened or received)

Answer 1

• secure burette in vertical position and fill with 0.1 N alcoholic potassium hydroxide (KOH)
• add 100mL of TAN to 300mL Erlenmeyer flask
• add ~8-9 drops of p-Naphtobenzein Indicator (solvent turns orange)
• titration solvent w/0.1 N KOH from orange to green (won’t take very much). Volume should be recorded as blank unless burette is refilled
• add 100mL of sample to same flask. Sample should return to orange color. If sample doesn’t return to orange, it is basic and you should INFORM THE UNIT THAT YOU NEED A RESAMPLE
• Titrate sample back to green (endpoint is considered definite when color stays green for 15 seconds)
• record mL if Titrant used . If burette refilled, use volume titrated as final volume. If not, subtract blank from final volume to obtain result

Question 2

Procedure B (sweetened sample)

Answer 2

• measure 150mL of sample (75%mark on 200mL graduate) and place in 500mL round flask
• add 100mL sweetening reagent (blue solution to 500mL round flask
• add large magnetic stir bar and stopper flask; stir for 30 minutes vigorously
• after stirring 30 minutes, transfer liquid to 500mL separatory funnel and allow layers to separate
• discard blue aqueous layer, after draining, swirl and remove any sweetening garnet on sides allowing them to sink to bottom. Drain remaining sweetening reagent.
• filter sample through acid free filter paper into clean graduate or directly into 500mL separatory funnel
• add approximately 50mL 0.1 N sulfuric acid and shake w/intermittent venting for 1 minute. Allow layers to separate and discard lower acidic layer.
• wash hydrocarbons w/100mL DI water by shaking and venting for 1 minute. Allow layers to separate and remove lower water layer. Repeat for total 3x
• after last water layer removed, filter through acid-free filter paper (discard first 10mL through filter due to possible water contamination) into clean 200mL graduate. Collect at least 100mL of sweetened sample.
• follow procedure A

Question 3

Purpose

Answer 3

Determine acid number in petroleum products, petroleum distillates and other hydrocarbons by colorimetric titration. Products may contain acidic constituents present as additives or as degradation products formed during service, such as oxidation products. Relative amount of acids can be determined by titrating with bases. Acid number used as guide in quality control of lubricating oil formulations. Limited to light colored distillates since color hard to determine with dark products.