A non-catalytic, supercritical methanol route for producing high-yield saturated and aromatic compounds from de-oiled asphaltenes

Upgrading of de-oiled asphaltenes (DOAs), i.e., the heavy fraction obtained after solvent deasphalting of vacuum residue, was investigated in supercritical methanol (scMeOH) without using external catalysts and molecular hydrogen. Process parameters, including temperature (350-400 degrees C), reaction time (30-120 min), and additive (formic acid), were explored to optimize the yielnof light oil with few impurities. As a result of the beneficial in-situ hydrogen-donation ability and reactivity of scMeOH, its use resulted in higher DOA conversion, increased light-fraction yield, and fewer impurities as compared to those obtained in supercritical water (scH(2)O). Higher reaction temperatures and residence times increased the DOA conversion to low-molecular-weight saturates and aromatics. With the addition of formic acid as a secondary source of H-2 in scMeOH at 400 degrees C, a 16.7 wt% DOA concentration, and a 90 min residence time, a remarkably high liquid oil yield of 83.9 wt% was obtained. The produced light fraction oil contains a low asphaltene content (0.53 wt%) and few impurities (S, 2.74 wt%; Fe, 19.6 ppm; Ni, non-detectable; V, 18 ppm). In addition, the maltenes content (i.e., saturates + aromatics) was 78.3% and the naphtha-to-diesel fraction was 18 wt% in the light-fraction oil; these results indicate effective cracking, desulfurization, and demetallization in the scMeOH medium with formic acid. A plausible reaction mechanism for scMeOH-based upgrading is discussed. (C) 2016 Elsevier B.V. All rights reserved.