Hydrotreating the Organic Fraction of Biomass Pyrolysis Oil to a Refinery Intermediate

The effect of the catalyst type, hydroprocessing conditions, and feed preparation on the mild hydrotreating of biomass pyrolytic lignin was examined. Pyrolytic lignin oils were produced by water separation at 1:1 and 3:1 water/oil mass ratios. Hydrotreating was performed in a semi-batch reactor at three severities using sulfided NiMo/Al₂O₃, Pd/C, and Pt/C catalysts. Over half of the carbon in the pyrolytic lignin could be converted to a low-oxygen (<5%), low-acid, volatile, hydrocarbon-miscible liquid product. This was achieved with all three catalysts at the most severe condition (400°C and 2450 psig) and with Pt/C at somewhat less severe conditions. Nuclear magnetic resonance (NMR) analyses indicated that the remaining oxygen is largely phenolic in character. Hydrotreating of the organic fraction (pyrolytic lignin) gave oil with better properties, lower O and lower acidity, than hydrotreating of the whole oil at equivalent conditions.