Observation of the heavy crude oil dissolution behavior under supercritical condition of water

In development of on-site partial upgrading technology of the bitumen by using supercritical water as a reaction solvent, it is important to understand the role of water in the reaction field. Therefore experiments were carried out using a batch reactor system operating with varying reaction pressure at a temperature of 703 K, and reaction time of 15 min. From the results such as the viscosity and the boiling point distribution of oil product etc., it can be seen that higher density supercritical water inhibits the cracking of bitumen to lower molecular weight substance. In the case of water with alkali it is found that alkali also helps to inhibit the cracking to lower molecular weight substances. Furthermore, the amount of the hydrogen became higher. It was inferred that some mechanism of hydrogen generation takes place with the addition of alkali. In experiments using a continuous flow reactor system at a temperature of 703 K, it was confirmed that higher density supercritical water also inhibits the thermal cracking. However, that heavy ingredient of bitumen was collected in the reaction chamber bottom simultaneously. These findings suggest that bitumen and supercritical water did not become homogenous phase in reactor. To clarify the phase behavior of bitumen and supercritical water, visible type autoclave was used for in-situ observation. Water and bitumen or its fractions divided by solvents fractionation were put into the visible-type autoclave, dissolution of bitumen or its fractions to water was observed with increasing temperature above critical temperature of pure water. Under these conditions, there were two phases which were separated by an interface were observed. On the other hand, synthesis oil which has bitumen components expect of asphaltane (pentane insoluble) was dissolved to supercritical water. Result shows that heavier portion of asphaltane cannot be dissolved to supercritical water. These components had become coke in thermal cracking of bitumen was considered. Based on this observation result, the anti-coking effect of supercritical water was thought that it is necessary to consider the dispersion of the supercritical water molecular to the asphaltene like components of bitumen.