Upgrading of bitumen by hydrothermal visbreaking in supercritical water with alkali

This study aimed to clarify the characteristics of the upgrading reaction of bitumen in supercritical water with alkali compared to pyrolysis, and to obtain more information about desulfurization in supercritical water with alkali. The results are summarized as follows: (1) The main components of the oil produced were paraffins and aromatics for pyrolysis and supercritical water cracking with and without alkali. The visbreaking mechanisms may be the same or very similar. (2) The time dependencies of the visbreaking and desulfurization reactions were similar, but the effects of water were opposite: visbreaking was more extensive with lower water content in a short reaction time, whereas desulfurization proceeded with high water content over a long reaction time. (3) Many thiophenes were formed in the oil produced, but benzothiophene (BT) and dibenzothiophene (DBT) were hardly detected in the case of supercritical water cracking with and without alkali. These BT and DBT were relatively easily decomposed or desulfurized in the supercritical water with alkyl. (4) Vanadium in the oil product decreased to ca. 10%. About 60% was found in the aqueous phase.