Stabilization of Pyrolysis Oil Model Compounds: Comparison of Catalyst Performance and Sulfur Sensitivity

It is necessary to find sustainable alternatives to the conventional fossil fuels used by the transportation sector today. For the hard-to-abate aviation and heavy transport, liquid hydrocarbon fuels derived from biomass via pyrolysis are a viable option. Biomass pyrolysis oils need upgrading by hydroprocessing before they can be further processed into fuels at a refinery. Due to reactor plugging and catalyst deactivation in one-step hydroprocessing, it has been proposed to add a stabilization step at a lower temperature to convert the most reactive compounds in pyrolysis oil, such as carbonyls, to less reactive species such as alcohols. Three different catalysts, Ni/Al2O3, sulfided NiMo/Al2O3, and Pt/Al2O3, were studied for stabilizing three different model compounds, furfural, guaiacol, and octanoic acid, alone and as a mixture in a batch reactor at 90 bar initial H2 pressure and 180 °C. The order of performance was determined to be Ni/Al2O3 > Pt/Al2O3 > sulfided NiMo/Al2O3 in these conditions. The Ni/Al2O3 catalyst showed both the highest overall conversion, the most fully hydrogenated compounds, and the highest carbonyl conversion. The effect of adding 1172 wt-ppm sulfur to the feed was also investigated, which showed that Ni/Al2O3 was the most sensitive catalyst to sulfur poisoning.