PrintMetals Content and Total Acid Number
Metals Content
Most common metals that are found in crude oil are included in organometallic compounds like nickel, vanadium iron and copper, ranging in concentration from a few ppm up to 1000 ppm by weight, depending on the source of crude oil. Similar to sulfur species, the metallic compounds tend to concentrate in the higher-boiling fraction of crude oil. Higher metal contents also require treatment during petroleum refining because of the corrosion activity of some metals and their tendency to accumulate on catalyst surfaces, thus deactivating the catalysts in a number of refinery processes. Metal content can be measured using a standard EPA Method 3040.
Total Acid Number
Acidity of crude oil is measured by titration with potassium hydroxide (KOH), using the standard method ASTM D664. The measured acidity is expressed as the Total Acid Number (TAN) that is equivalent to milligrams of KOH required to neutralize 1 gram of oil. This number is particularly important to control corrosion in the distillation columns through selection of corrosion-resistant alloys for surfaces that come into contact with oil.