Investigation of Biocrude Production from Spirulina via Catalytic Hydrothermal Liquefaction with the Ru/ZrO2-SiO2 Catalyst

Hydrothermal liquefaction (HTL) is a promising technology for converting wet biomass to liquid fuels. However, the biocrude yield and quality in this process are unsatisfactory without catalysts. Herein, a Ru/ZrO2-SiO2 catalyst was prepared with the NaBH4 reducing method for the HTL of Spirulina. The results demonstrated the successful deposition of Ru particles onto the ZrO2-SiO2 carrier, resulting in improved crystallinity and a more stable internal structure. The effect of different loading ratios of Ru particles on biocrude production was investigated. The findings revealed a gradual decrease in biocrude yield with increasing loading ratio of Ru particles. Meanwhile, the energy recovery (ER) rate exhibited a trend of first increasing and then decreasing, with a peak of 67.51% observed at a 4 parts per thousand loading molar ratio. The GC-MS results indicated an increase in hydrocarbon content, accompanied by a decrease in carboxylic acids and esters, demonstrating the hydrodeoxygenation effect of Ru. Additionally, the impact of the Ru/ZrO2-SiO2 dosage on the HTL of Spirulina was examined. The highest biocrude yield of 53.89% was attained with a 15% catalyst dosage, while the highest ER rate of 68.29% was observed at a 10% catalyst dosage.