We performed hydrothermal liquefaction of brown macroalga (Saccharina latissima) in the presence of homogenous and heterogenous catalysts such as KOH, Na2CO3, Pd/C, HZSM-5, Ce/HZSM-5, and Ni/SiO2-Al2O3 in hot compressed water, to investigate their effects on product yield and composition in the biocrude. To investigate hydrocarbon production, we used methanol as co-solvent (methanol-to-water 1/4 vol.%) and as the only liquefaction solvent. We carried out the experiments in a batch reactor at 330oC and 120-130 bar, and varying temperature, algae-to-water ratio, residence time, and pretreatment method. The biocrude yields ranged from 12.9 to 25.7 wt.% and that of solid residue ranged from 5.0 to 22.4 wt.%, while gas yields ranged from 15.7 to 31.3 wt.%. The dissolved organics in the aqueous phase constituted the largest fraction of the products (23.8-39.9 wt.%). The catalysts that showed the most promise to produce hydrocarbons in water medium were HZSM-5 (0.6 wt.%), Ce/HZSM-5 (0.5 wt.%), and Pd/C (0.2 wt.%). The maximum biocrude yield of 25.7% was obtained using methanol as a liquefaction co-solvent. Temperature and residence time were found to be the most important factors affecting yield. The biocrude was found to be a complex mixture of aldehydes, ketones, ethers, phenols, hydrocarbons, fatty-acids, and heterocyclic nitrogenous compounds. We further subjected the obtained biocrude to upgrading in a pyrolyzer with HZSM-5 catalyst, which was found to be most effective at the biocrude-to-catalyst ratio 1:5, producing 4.1 wt.% hydrocarbons yield, primarily composed of aromatics. These results show promise in assessing the prospect of utilizing S. latissima as a natural source to produce transportation fuels and high-value chemicals.

Date of publication

Spring 2023

Document Type




Persistent identifier


Committee members

Fernando Resende, Aaditya Khanal, Mohammad Biswas


Master of Science in Mechanical Engineering

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