Upgrading of bitumen in supercritical fluids

An upgrading process for heavy oils and bitumens, based on the use of activated carbon catalysts, was investigated in a bench-scale plug flow reactor. Good results were obtained at pressures as low as 7.0 MPa at temperatures of 400–450°C. The process required the presence of hydrogen gas and a hydrogen-rich solvent in a supercritical state. If the solvent was a highly saturated alkane, very little solvent decomposition occurred. A number of n-alkanes were tested as solvents, as well as paraffinic petroleum cuts and donor solvents such as tetralin and decalin. A range of values of other operating parameters was also investigated. With an Athabasca bitumen coker feed, bitumen conversions to distillable liquids of 82–88% by weight (95–105% vol%) were achieved, with 6–8 wt% (coke+pitch) yields. Demetallization was almost 100%, and hydrodesulfurization and hydrodenitrification levels of over 80% also resulted. Under similar conditions, a conventional Co/Mo hydrotreating catalyst gave higher hydrogen uptake but lower pitch conversion, supporting the concept that carbon-based catalysts may give a unique product distribution and utilize hydrogen more effectively. It is postulated that four conditions must be met to obtain the favorable results found in this work: there must be a significant level of supercritical fluid; there must be a highly saturated or paraffinic supercritical solvent present; hydrogen gas must be present; and there must be an activated carbon catalyst used which may also have incorporated in it a catalytically active metal.