Upgrading of Bitumen in the Presence of Hydrogen and Carbon Dioxide in Supercritical Water

Upgrading of bitumen was examined in supercritical water (SCW) and its mixtures with hydrogen and carbon dioxide using semibatch reactors. Coke formation became prominent above 673 K in SCW and 693 K for SCW + H 2 + CO 2 . Coke yield in SCW was higher than that in SCW + H 2 + CO 2, implying that coke formation is suppressed in SCW + H 2 + CO 2 . The asphaltenes obtained with SCW + H 2 + CO 2 had higher H/C atomic ratios than those of the raw asphaltene or asphaltene obtained with SCW. The average molecular structures of raw asphaltene, as well as asphaltene in SCW and in SCW + H 2 + CO 2, were estimated. From the properties of asphaltene, repolymerization during decomposition of asphaltene was probably inhibited in SCW + H 2 + CO 2 . Furthermore, the oil formed in SCW + H 2 + CO 2 was removed from the reactor more easily than that in SCW. The removal of oil from the reactor and the hydrogenation of asphaltene through reverse water-gas-shift reaction probably suppressed coke formation in SCW + H 2 + CO 2 .