Process intensification for heavy oil upgrading using supercritical water

Demand for light hydrocarbons has been steadily increasing in the market with a corresponding decrease in heavy hydrocarbon demand. Therefore, there is a need to develop environmentally friendly and efficient technologies for conversion of heavy molecular weight hydrocarbons. Supercritical fluids (SCF) are attracting increased attention as solvents for green chemistry and among those supercritical water (SCH2O) is promising for the upgrading of heavy hydrocarbons. Because of a sharp decrease in its dielectric constant, water loses its polarity when brought to the supercritical conditions and its properties starts to resemble the properties of hydrocarbons and becomes an excellent solvent for organic compounds. Moreover, increased ionic product of water leads to an increasing [H3O+] concentration and thus promotes the reactions requiring the addition of an acid. Solvation power enables the extraction of lighter compounds while increased [H3O+] concentration makes the reactive extractions of heavy hydrocarbons possible. As a result of its favorable properties, a wide variety of process intensification studies have been carried out using near critical or SCH2O such as combined distillation-cracking-fractionation and in some cases even without the utilization of catalysts and/or hydrogen. In this review, recent advances on reactions of hydrocarbons occurring in a SCH2O environment will be highlighted. Fundamental aspects of these reactions including their thermodynamics and kinetics will be discussed. Experimental and theoretical developments on phase equilibria of relevant water-hydrocarbons systems will be presented. (c) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.