Green processes that upgrade biomass feedstocks and recycled bio-waste can both help meet our growing energy demands as well as reduce our overall carbon footprint. One promising technology is hydrothermal liquefaction (HTL), which breaks down wet organic solids at moderate temperatures and high pressures to form a carbon rich oil phase. While the bio-oil formed has a high heating value, the process often produces other byproducts such as solid biochar, carbon dioxide and wide distribution of organics that are water soluble. To design an economical HTL process, the water soluble organic byproducts must be minimized to increase oil product yields and reduce wastewater generation. In particular, metal oxide catalysts are an active and hydrothermal stable option for HTL upgrading chemistry. CeZrOx, in particular, is active for acid coupling reactions which simultaneously increase the carbon number of the product and decrease its oxygen to carbon ratio, both of which act to increase the oil yield and decrease the carbon loss to the aqueous phase. In our study, we sought to understand the key reactions that take place in the HTL process when using CeZrOx as a catalyst. HTL conversion of food waste at 300 °C and 20.7 MPa was performed without the use of a catalyst, with CeZrOx or with Na2CO3 catalyst. Compared to uncatalyzed and Na2CO3 HTL reactions, CeZrOx was shown to have improved HTL oil yields, increased product energy content and reduced total organic content in the water phase. Subsequently, tests were performed to expose CeZrOx to hot liquid water conditions at 300 °C and 20.7 MPa for up to 165 hours. Post-run characterization was performed using both XRD and DR-UV to verify the hydrothermal stability of CeZrOx. In addition, CeZrOx catalyst activity was evaluated for reaction of small oxygenated molecules as model compounds for water soluble food waste products. CeZrOx was shown to be highly active and reusable in aldehyde coupling reactions, with the primary product being branched alkenes. Lastly, an energy analysis was performed to illustrate the improvement in lifetime energy recovery using CeZrOx relative to other homogenous HTL

Aldehyde chemistry using CeZrOx catalyst for aqueous hydrocarbon upgrading

256th National Meeting (2018)

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