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
Fernando Resende, Aaditya Khanal, Mohammad Biswas
Master of Science in Mechanical Engineering
Oke, Mayokun A., "HYDROTHERMAL LIQUEFACTION OF SACCHARINA LATISSIMA FOR THE PRODUCTION OF BIOFUEL" (2023). Mechanical Engineering Theses. Paper 24.
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