Hydrothermal Liquefaction of <i>Saccharina latissima</i>: Effects of Catalysts, Temperature, Residence Time, and Biomass-to-Water Ratio
Mayokun Oke, Fernando L.P. Resende
Abstract
We performed hydrothermal liquefaction of brown macroalgae ( Saccharina latissima ) in the presence of homogeneous and heterogeneous catalysts such as KOH, Na 2 CO 3, Pd/C, HZSM-5, Ce/HZSM-5, and Ni/SiO 2 –Al 2 O 3 in hot compressed water to investigate their effects on product yield and composition of the biocrude. We investigated the effect of the temperature, algae-to-water ratio, residence time, and pretreatment method. The biocrude yields ranged from 12.9 to 23.6 wt % and that of solid residue ranged from 5.0 to 30.8 wt %, while gas yields ranged from 15.7 to 28.3 wt %. The dissolved organics in the aqueous phase constituted the largest fraction of the products (23.8–39.9 wt %). The following catalysts (5 wt % loading) produced the best yields of hydrocarbons: HZSM-5 (0.6 wt %), Ce/HZSM-5 (0.5 wt %), and Pd/C (0.2 wt %). The HZSM-5 catalyst was further used to investigate hydrocarbon production under varying operating conditions. The maximum biocrude yield of 23.6 wt % was obtained using the Ce/HZSM-5 catalyst. 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. These results show promise in assessing the prospect of utilizing S. latissima as a natural source to produce transportation fuels and high-value chemicals.