The Demetallization of Residual Fuel Oil and Petroleum Residue

Heavy residual fractions were treated to remove metal contaminants by nonconventional methods, such as centrifugation, solvent extraction, and contacting the material with various chemicals and chelating agents. The centrifugal method was found to be effective in reducing water-soluble metal salts and the Na/V mass ratio was reduced from about 0.5 to about 0.1. The extraction method using polar solvent (ethyl acetate) was found to be very effective for removal of oil-soluble metals from heavy residual fractions. Among the acids used in the chemical treatment method, sulfuric acid showed the most promising results. Although sulfuric acid effectively removed sulfur and metals along with the resinous and asphaltic substances from petroleum, the formation of an emulsion was always a serious problem; when broken it yielded darkened oil and a lot of acid sludge. Most of the chemical agents appeared to be effective for the demetallization of heavy oils and residue. The contact of heavy residual fractions with aqueous solutions of FeCl3 and SnCl4 (0.1-0.5 M range) in acidic solution appeared to be effective. A pretreatment step before the traditional hydroprocessing methods is recommended for the upgrading of heavy oils.