(621e) Impact of Co-Processing Bio-Crude with Petroleum Stream on Hydrotreating Catalyst Deactivation

Co-processing of bio-crudes, from hydrothermal liquefaction (HTL) of biomass or wet wastes, in current refinery process such as hydrotreating with petroleum streams has great potential to produce green transportation fuels in the near term. However, one of the risks is the possible faster deactivation of the hydrotreating catalysts caused by co-processing HTL bio-crude, especially considering some problematic characteristics of HTL bio-crudes such as high content of nitrogen containing species, oxygenates, and inorganics. They can potentially lead to the poisoning of catalyst active sites by strongly adsorbing molecules like nitrogen compounds and the blocking of the pore structure or fouling the catalyst active sites by coke formation from oxygenates or inorganic deposition. In this research, we developed an understanding of the deactivation mechanism of a NiMo/Al₂O₃ hydrotreating catalyst for co-processing a wastewater sludge HTL bio-crude with straight run diesel or vacuum gas oil. Spent catalysts after testing petroleum feed and co-processing different bio-crudes have been collected after >300 hours’ time on stream (TOS) testing. These catalysts have been characterized by various techniques such as physisorption, chemisorption, elemental analysis, ICP-OES, TGA-MS, and SEM-EDX for their chemical and physical properties. Their catalytic activity has also been evaluated by model compound testing including hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of cyclohexene (CHE) to quantitively determine the concentration of different active sites. The results indicate more carbonaceous species and inorganic deposits (such as Fe and Si) on the external surface of spent catalysts at the top of the reactor when co-processing untreated bio-crude compared with pretreated bio-crude, diesel only or fresh ones, which leads to severe loss of catalyst active sites. A clear understanding of the deactivation behavior particularly caused by bio-crudes is highly desirable and critical to improve hydrotreating catalyst/process to enable co-processing renewable feedstocks and incorporate biogenic carbon in fuels.