LAUSR

Two main limitations in heavy oil are the recovery and upgrading process, which emphasizes aquathermolysis as an alternative approach to reduce viscosity and increase oil quality simultaneously. In addition to facilitating solubilization of asphaltene, hot water (subcritical and supercritical) injected into the heavy oil reservoir also serves as a hydrogen donor. The main purpose of this article is to review catalytic aquathermolysis of heavy oil over zirconia, which is a robust oxide. Zirconia-based nanocatalysts are promising due to their high oxygen storage capacity, acidity, and stability in sub- and supercritical water. The article also elaborates on various methods to fabricate nanosized zirconia with different shapes and sizes by sol–gel, spray pyrolysis, electrospinning, and hydrothermal techniques.