(727e) Continuous Hydrotreatment of Sewage Sludge and Spirulina Algae Biocrudes from Hydrothermal Liquefaction: Different Catalysts for Different Organic Contaminants

Unprecedented global warming and raising public awareness are the driving factors to decarbonize long-haul transportation sector. In this regard, biomass could be a potential renewable source for the production of sustainable, carbon-neutral liquid fuels. Hydrothermal liquefaction (HTL) followed by catalytic hydrotreatment is one of the most promising pathways to covert varying feedstocks into drop‑in fuels. The energetically dense black viscous product from HTL (“biocrude”), contains a diverse organic pool with considerable amount of oxygen (~5‑18%), nitrogen (~1-8%) and metallic content (~0.1‑0.6%). The presence of these organic contaminant results in poor miscibility with fossil fuels and poses new and exciting challenges e.g. thermal instability of biocrude at high temperatures which are indispensable for complete hydrodenitrogenation. This is why special attention is needed not only to realize this complex biocrude mixture but also to select different catalysts which performs best to saturate and remove certain organic contaminants under optimized conditions.

In this work, we utilized advanced analytical tools (i.e. FT‑ICR MS etc.) and observed different classes of organometallics and nitrogen compounds from sewage sludge and Spirulina algae biocrude. From these results, we utilized three different types hydrotreating catalysts based on their porosity and nickel loading on γ‑Al₂O₃ support and successfully demonstrate smooth continuous hydroprocessing operations (Figure 1) for hundreds of hours without coke formation, catalyst deactivation, and reactor plugging. Finally, 100% deoxygenation and ~96% denitrogenation were achieved. Furthermore, hydrotreated products underwent true-boiling point fractional distillation and showed on‑spec metal content, density, pour point, cloud point and HHV for diesel and jet fuel.

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