Abstract
The hydro-upgrading reactivity of the vacuum residue produced in PSU 1 t/day plant for Wandoan coal was examined, using commercial NiMo/γ-Al2O3 catalysts in relation to the structure of its asphaltene, to find a way for the complete conversion of the coal to oil. The asphaltene content in the original residue was reduced to 5% on d.a.f. coal base under conditions, 450°C, 15MPa H2, 60min, 1.5 solvent/residue ratio, and solvent composition of 75% 1, 2, 3, 10b-tetrahydrofluoranthene 4HFL and 25% pyrene. Such conditions removed completely the preasphaltene, while 17% of organic residue remained. Hydrogen donor 4HFL and aromatic hydrogen-shuttler pyrene were effective to convert residual asphaltene and preasphaltene. The catalyst of large pore was suitable for the conversion of preasphaltene while the conversion of asphaltene requires hydrocracking activity.
Brown & Ladner parameters of the asphaltene before and after the hydrotreatment were calculated based on elemental analyses, 1H and 13C-NMR, VPO and GPC. Although the molecular weight of the asphaltene stayed around 600, the degree of aromaticity and condensation increased after the hydrotreatment. The conversion of asphaltene to oil is suggested to require reduction of molecular weight while the remaining asphaltene suffers the dehydrogenation, dealkylation and some condensation reactions. The origin of inert asphaltene is briefly discussed.
