Co-processing of biocrudes from hydrothermal liquefaction (HTL) of biomass and wastes with petroleum streams in refinery hydroprocessing has significant potential to accelerate the production of renewable transportation fuels in the near term. However, HTL biocrudes with some problematic characteristics can potentially cause faster deactivation of the catalysts, which is one of the biggest barriers to the adaption of biocrude in the current refinery process. In this work, we investigated the deactivation modes of a sulfide NiMo/Al<sub>2</sub>O<sub>3</sub> hydrotreating catalyst used for co-processing HTL biocrude (from wastewater sludge) with straight-run diesel. Spent catalysts were collected after co-processing diesel with different biocrudes after &gt; 300 hours' time on stream and characterized by various techniques. Their catalytic activities were evaluated by model compound testing. Loss of catalyst activity was observed after co-processing biocrudes. No structural change of the catalyst after co-processing biocrudes was observed and catalyst deactivation is largely due to catalyst fouling by carbonaceous species and metal contaminants (such as Fe and K) from biocrudes. Inorganic contaminant deposition leads to the external coating of the catalyst pellets on the top of the reactor, whereas the carbonaceous species potentially bind near the sulfide active phase, thereby blocking access to the active edge sites. Pretreatment of the HTL biocrude can reduce problematic species and alleviate catalyst deactivation during co-processing.

Impact of co-processing biocrude with petroleum stream on hydrotreating catalyst stability

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