A Study on metal removal in crude oil using low-molecular-mass organic acids

Abstract

Crude oil contains several metal contaminants such as iron, vanadium and nickel, and these trace metals have deleterious effect on oil refinery. For example, they can contribute to corrosion of plant unit, heat exchanger fouling. Among the problematic situations caused by metals in crude oil, catalyst deactivation is of major concern in oil refinery. In other words, metals such as vanadium, nickel and iron can cover the surface of the catalysts and disturb their normal activity. Because of these reasons, the demand for demetallization in crude oil has been increased for the past few decades. Some part of metals in crude oil can be removed by electric desalter, when they exist as form of inorganic salts such as inorganic oxides or sulfides. However, large portions of metals are usually in the form of organometallic complexes, which are difficult to be removed in desalting process because of their oleophilic characteristic and poor solubility in water. Iron can also exist as a complex form with various organic compounds, such as a form of iron carboxylate. We used iron standard solution (1,000 μg/g, in 75 cSt hydrocarbon oil), iron (III) 2-ethylhexanoate and iron (III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate) as model compounds. These model compounds were reacted with aqueous solution of several organic acids. As a result, organic acids such as citric acid and ethylenediaminetetraacetic acid (EDTA) disodium salt shows remarkable effect in removal of iron from model compounds. Maleic acid was also effective for removal of iron showing positive results.