Catalytic hydrothermal liquefaction of Spirulina over bifunctional catalyst to produce high-quality biofuel

In this study, five different bifunctional catalysts (NiO/SAPO-34, NiO/ZSM-5, NiO/USY, NiO/gamma-Al2O3 and NiO/SiO2) are characterized and applied for the hydrothermal liquefaction (HTL) of Spirulina to produce biofuel. The X-ray diffraction (XRD), ammonia desorption measurement (NH3-TPD) and Brunauer-Emmet-Teller (BET) analysis results show that NiO/SAPO-34 and NiO/USY catalysts have the better physical properties compared to the other three catalysts, resulting in the higher bio-oil yields of 59.85 wt% and 59.12 wt%, respectively. Then the bio-oil samples are characterized by elemental analysis, Gas Chromatography-Mass Spectrometry (GC-MS) and Thermo-gravimetric analysis (TGA). Results indicate that the bio-oil obtained over NiO/USY catalyst has the highest higher heating value (HHV) due to the higher C and H content as well as the lower O and N content. What's more, it contains the most hydrocarbons (20.58%) and light oil components (72.91%) with NiO/USY catalyst. Consequently, NiO/USY is considered to be the best bifunctional catalyst for the HTL of Spirulina.