(183d) Upgrading of Petroleum Vacuum Residue Using Supercritical Hydrocarbon Solvents in Batch and Continuous Systems

As demands for transport fuels and lighter oils have increased, petroleum industries have been forced to refine low-quality extra heavy oils. Among the heavy feedstocks, petroleum vacuum residue (VR), which is the heaviest fraction of crude oil, has high boiling points over 520 °C and contains about 5 wt. % of sulfur, 0.5 wt. % of nitrogen, and organometallic compounds such as nickel and vanadium. Generally, heavy feedstocks can be converted into light products by either carbon rejection process or hydro-conversion process. However, it is difficult for extra heavy oils to be converted into liquid fuels by the conventional upgrading processes due to the high concentration of impurities and asphaltenes.

 In the study, supercritical upgrading process (SUP) was applied to upgrade vacuum residue (VR) to light products with small amount of coke formation in batch and continuous systems. Since the physical and transport properties at near-critical region of fluid are altered sensitively, the parametric study for the SUP was required to elucidate optimum operating conditions, depending on various hydrocarbon solvents. The upgrading results were evaluated on residue conversion, coke formation, and product distribution (naphtha, middle distillate, vacuum gas oil, and residue) at various operating conditions; temperature (350-450 °C), hydrogen partial pressure (0-3.45 MPa), reaction time (5-30 min). In addition, further study on a continuous system was conducted on the basis of the results from the batch system. In the continuous system, residence time worked as one of key operating parameters to suppress the coke formation.