Co-Processing of Deoxygenated Pyrolysis Bio-Oil with Vacuum Gas Oil through Hydrocracking

The co-processing of deoxygenated pyrolysis bio-oil with vacuum gas oil was studied in a hydroprocessing pilot plant. The bio-oil used as the biogenic component of the feed was produced by fast pyrolysis of forest biomass and pretreated via hydrodeoxygenation to improve its chemical stability. Two blends containing 5 and 7.5% deoxygenated bio-oil in hydrotreated vacuum gas oil were tested for hydrocracking at reaction temperatures of 385-400 degrees C, including tests with pure vacuum gas oil to establish a baseline for the study. Testing over 2154 catalyst hours showed that pyrolysis bio-oil co-processing did not impact much baseline hydrocracking selectivity, yielding similar amounts of naphtha and diesel at a given conversion of material boiling above 343 degrees C, but with increasing hydrogen consumption levels proportional to the amount of bio-oil in the feed. Periodic monitoring of catalyst stability during continuous operation showed no signs of enhanced catalyst aging as a result of co-processing the pyrolysis bio-oil blends. Characterization of the distillation fractions from the hydrocracked liquid products revealed differences in hydrocarbon-type composition and fuel properties for the same product streams from different bio-oil blends. The naphtha fraction from the 7.5% co-processing blend showed better octane number with respect to the other naphtha products, owing to its reduced paraffinic content. The diesel products from the two co-processing blends were slightly higher in aromatic content than the baseline diesel product, which caused a loss in cetane index. This study suggests that it is feasible to co-process pyrolysis bio-oil through hydrocracking provided that it has undergone pretreatment to stabilize reactive oxygen components.