(99c) Catalytic Hydrothermal Liquefaction of Food Waste Using Inexpensive Catalysts
- Conference: AIChE Spring Meeting and Global Congress on Process Safety
- Year: 2019
- Proceeding: 2019 Spring Meeting and 15th Global Congress on Process Safety
- Group: Emerging Technologies in Clean Energy
Tuesday, April 2, 2019 - 2:20pm-2:45pm
Hydrothermal liquefaction (HTL) is a promising method of the conversion of organic waste and biomass streams with high water content, into a carbon rich bio-oil, along with bio-char and residual aqueous phases. However, organic compounds partitioning into the HTL aqueous phase reduce the oil recovery and require costly water purification steps. Therefore, in order to reduce the water-soluble HTL organics, carbon-carbon and other coupling reactions are desirable to increase the product molecular weight, hence the oil phase solubility. Catalysts can promote such coupling reactions. In the literature, both homogenous and heterogeneous catalysts are utilized with HTL to increase the bio-oil yields and energy recovery[5-8]. Recently, we reported the use of CeZrOx catalyst for HTL of food waste. CeZrOx catalyzed HTL showed significant improvement to the bio-oil yield and energy recovery compared to non-catalyzed and Na2CO3-catalyzed HTL, while reducing the organic content of the aqueous phase. Using model compounds, it was shown that CeZrOx promotes carbon-carbon coupling aldol reactions. In addition, CeZrOx exhibits hydrothermal stability at 300°C. However, this is a relatively expensive catalyst material containing the rare earth metal cerium.
In this study, we evaluated the catalytic viability of inexpensive acid and base solid oxide catalysts, including red mud (Bayer process waste), red art clay and fly ash (from coal combustion power plants) using batch HTL reactions on a representative consumer food waste at 300 °C and 20.7 MPa. HTL bio-oil products were evaluated for their energy content using higher heating values and total organic content of the aqueous phase product was determined using total organic carbon (TOC) analyzer. The results show that red mud and red clay improved the total oil recovery relative to non-catalyzed HTL reactions by reacting water-soluble organics.
This work was funded by a Department of Energy SBIR (Grant Number DE-SC0015784). Carla Roma, Caroline Murphy, Lawrence Valeros and Joseph Esposito supported the experimental work on this project.
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