(639a) Supercritical Water Upgrading of Heavy Oils: Historical Perspective

Continuous increases in the sulfur content and average molecular weight of remaining petroleum reserves are straining refinery capacity using current technologies.  New technologies are required for cleaner, energy efficient utilization of sulfur rich heavy oils.   Treating heavy oils and bitumen in supercritical water has been known since the 1980s to reduce their molecular weight distributions and sulfur contents.  Crucially, supercritical water treatment does not promote coke formation, does not require catalysts, and reduces heavy oil asphaltene content.  However, commercialization has been held back by contradictory literature data and a lack of fundamental understanding of the chemical reactivity, thermodynamic phase behavior, and transport phenomena at supercritical conditions.  This paper will present an overview of the historical development of supercritical water upgrading of heavy crude oils, with a focus on identifying knowledge gaps in several key areas: 1) the role of water, 2) the role of phase behavior and mixing, 3) the chemical mechanism, 4) the use of catalysts, and 5) the fate of sulfur bearing compounds.