Mild Hydrotreating of Biomass Pyrolysis Oils to Produce a Suitable Refinery Feedstock

Fast pyrolysis produces a liquid product that represents ̃ 70% of the mass of the starting material. However, since the raw oil is highly corrosive, largely immiscible with hydrocarbons, and only partly volatile, it is unsuitable for use in a conventional petroleum refinery or as a finished fuel. Catalytic hydroprocessing can remove oxygen to make a gasoline-or diesel-like product, but the processing costs have not been attractive. Economic analysis suggests that mild hydroprocessing, leaving 7 wt % oxygen in the pyrolysis oil reduce hydrotreating costs to a range that is more economically viable. If the physical and chemical properties of the mildly hydrotreated products were acceptable, these materials could potentially be available for coprocessing in a petroleum refinery leveraging the economies of scale and existing refining infrastructure to produce a lower-cost product. Mildly hydrotreated pyrolysis oil with low acidity, good miscibility with hydrocarbons, and high volatility was generated in a semibatch laboratory reactor. A 0.5-L sample was produced at 360° C, 2500 psig hydrogen, with a hydrogen flow of 0.22 sl/g-oil/h and 10 wt % nickel-molybdenum/Al ₂O ₃ catalyst. Yields were 36% light product (7% oxygen) and 30% liquid residue. This oil will be subjected to further physical and chemical tests to determine the technical feasibility of co-processing in a petroleum refinery.