(99e) Supercritical Water to Upgrade Petroluem Feedstock

Upgrading of low-value petroleum feedstock has been challenged by many research groups to have maximum process economy. In spite of various available technologies such as hydroprocessing and coking processes, strict market situation is stimulating emerging of new technologies which are utilizing newly found chemistry and physics related to hydrocarbon resources. One of the promising approaches is to use supercritical water as a reaction medium for petroleum upgrading. Unique properties of water in supercritical state are believed to facilitate certain reactions such as cracking, desulfurization, and demetallization. Furthermore, cage effect of supercritical water is proposed to reduce the amount of produced coke even at high temperature reaction, i.e., 400 ? 450 oC. Reaction occurring in supercritical water is basically radical-mediated one like thermal cracking, and shows high selectivity of cracking of heavy fractions toward light- and middle-distillate range hydrocarbons. After treatment with supercritical water, asphaltene content was dropped very much while saturate, olefin, and aromatic contents increased. C13-NMR clearly indicated that aromatic compounds were generated by the treatment and thus some amount of hydrogen was suggested to be released through dehydrogenation reaction. Sulfur and metal contents were decreased by the treatment. Thiophenic sulfur compounds showed much less difference from reactivity of paraffinic sulfur compounds such as thiol and sulfide than those generally observed in catalytic hydroprocessing. Most of sulfur, released from mother matrix with aid of supercritical water, was transformed to hydrogen sulfide.