For the first time, the AVTB-derived asphaltenes (containing very high concentrations of sulfur (7.70 wt % S) and nitrogen (1.08 wt % N)) were hydrotreated over novel MgO-supported Fe, Ni, NiMo. and CoMo catalysts in supercritical toluene at 380 degrees C under hydrogen of 5 MPa (cold pressure) in a batch reactor. The supercritical toluene alone without any catalyst was found to be effective for conversion of the highly aromatic as'phaltenes (AS) to less aromatic maltenes (MA) through a thermal cracking mechanism. All the MgO-supported catalysts proved to be effective for hydro-conversion of AS to MA in supercritical toluene. The activities of these catalysts for AS conversion showed the order of sequence of Fe/MgO < Ni/MgO < CoMo/MgO < NiMo/MgO. Among all the MgO-supported catalysts tested, NiMo/MgO was Found to be the most active one Col. promoting the removal of sulfur and AS. The sulfur/nitrogen/AS removal efficiencies for the NiMo/MgO catalyst increased with the treatment time, and the efficiencies at 120 Mill of treatment attained as high as 43%, 30%, and 70%, respectively. The MgO-supported catalysts showed excellent performance for preventing and retarding the formation of highly condensed aromatics or coke in the hydro-treatment of AS in supercritical toluene. Willi the presence of NiMo/MgO catalyst, hydro-treating AS in the supercritical toluene for it reaction time tip to 120 min produced a strikingly low yield (<0.7%) of toluene-insoluble product.