EFFECT OF PORE STRUCTURE OF NI-MO/AL2O3 CATALYSTS IN HYDROCRACKING OF COAL DERIVED AND OIL SAND DERIVED ASPHALTENES

Effect of catalyst pore structure was studied by using four unimodal Ni-Mo/Al2O3 having different median pore diameters (MPD, 120-730 angstrom) for hydrocracking (425-degrees-C, 1 h, 4.9 MPa H2) of the asphaltenes derived from Akabira coal (Aka-Asp) and Athabasca oil sand bitumen (Aosb-Asp). The asphaltene conversions increased with increasing catalyst MPD up to 290 angstrom and then remained constant or decreased up to 730 angstrom. Aka-Asp has a much smaller molecular size but a higher aromaticity than Aosb-Asp, whereas conversion of the former appeared to be more sensitive to pore size. Higher oil yields were obtained with large-pore catalysts, while the highest oil yield from Aosb-Asp was still remarkably lower than that from Aka-Asp. Maximum hydrodeoxygenation activity appeared at an MPD of 150 angstrom for runs of both asphaltenes, while an MPD of 290 angstrom corresponded to the highest activity for hydrodesulfurization of the sulfur-rich Aosb-Asp. Characteristics of used catalysts are also discussed.