Removal of Nickel and Vanadium from Heavy Oils Using Supercritical Water

Abstract

Heavy oils require substantial cracking in order to be economically refined to produce usable products. One major problem affecting the economics of refining heavy oils is the metal compounds contained in many of these oils which poison the catalyst used to crack the oil. Demetallization methods include physical, chemical, electrochemical, catalytic and supercritical water (SCW) techniques. Few of these methods are viable and/or efficient for the demetallization of heavy oil. This paper discusses the SCW based demetallization process by reviewing the open literature. The potential benefits of SCW based demetallization of heavy oils are also explored. Water partial pressure (WPP) has a moderate effect on the reaction of metalloporphyrins (MPs) in SCW; but temperature has a remarkably high effect. Metal removal is sensitive to the conversion of MP and increases exponentially with higher conversion. The kinetics are consistent with first-order dependency on MP disappearance. The reaction mechanism can be explained in terms of the free radical mechanism, but additional experiments and analysis are required to understand the fate of the metal after reaction. This non-catalytic SCW based upgrading process has the potential to allow production of refined fuel from heavy oils.