(46a) Hydrotreating catalyst performance during extended processing of pyrolysis oils to aviation and marine fuels

Hydrotreating is a crucial process in upgrading lignocellulosic biomass-derived pyrolysis oils into high-quality biofuels, where hydrogen is utilized to remove oxygen, sulfur, and nitrogen in the presence of a specialized catalyst under high temperature and pressure conditions. These environmental-friendly biofuels have great potential in replacing petroleum-based fuels in various transportation sectors, such as trucking, shipping, and aviation, to reduce greenhouse gas emissions. However, most hydrotreating experiments have been of short duration and potential operational problems, such as catalyst deactivation and catalyst bed fouling and plugging, could not be assessed. In this contribution, we will share results from four hydrotreating experiments of long durations from the production of sustainable aviation fuel (SAF) and marine fuel, which were all accomplished within the past year by our group. Catalytic fast pyrolysis (CFP) oils produced from woody biomass were hydrotreated for SAF production for 400-600 h time on stream (TOS). During the extended hydrotreating process, the deoxygenation activity remained constant with the product oxygen content below the detection limit (<0.01 wt%); the hydrogenation ability initially decreased but remained constant after 350-400 h; there were no visible signs of catalyst bed fouling and plugging. Up to 57 wt% of the hydrotreated products fell into the SAF range with most properties meeting ASTM D4045 and D7566 guidelines, which indicates a good potential for the product as a jet fuel blendstock. For marine fuel production, stabilized pyrolysis oil (SPO) was hydrotreated under mild conditions for 1000 h TOS total. As a result, 1 gallon of the hydrotreated product was produced and then blended with very-low sulfur fuel oil (VLSFO) for engine testing. SPO was produced through hydrogenating fast pyrolysis bio-oil, where the most reactive oxygenates were hydrogenated, for example, aldehydes were converted to alcohols, and anhydrosugars and acids reduced. However, during the prolonged process of hydrotreating SPO, significant catalyst bed fouling-caused pressure increase was observed. To prevent the potential plugging issue, the catalyst bed was replaced after 340 h TOS, and the reaction temperature was increased and the SPO flow rate was decreased for the last 200 h TOS when using the new catalyst bed.