Catalytic Hydrothermal Liquefaction of Microalgae for Bio-oil Production over Silylated SBA-15 with High Hydrothermal Stability

This paper mainly describes the application of silylated SBA-15 with high hydrothermal stability in catalytic hydrothermal liquefaction (HTL) of Dunaliella (D.) tertiolecta to produce bio-oil. The results indicated that selection of silylation reagent species contributes to improve hydrothermal stability of SBA-15 at 613 K through substituting hydroxyl group on SBA-15 surface. The grafting of silane on SBA-15 had an impact on pore size, wall thickness, specific surface area, pore volume, and other structure characteristics, while not influencing the ordered mesoporous pore structure. When silylated SBA-15 was used as catalyst, D. tertiolecta conversion and bio-oil yield decreased slightly due to adsorption of furan and other compounds on mesoporous structure of SBA-15. Silylated SBA-15 inhibited ammonolysis, Maillard, and other reactions, resulting in decreased acid, ester, amide, and N-containing heterocyclic content in bio-oil. Meanwhile, the content of aldehydes and ketones increases, among which furfural derivatives were the main substances (>70%). Highly selective HTL is realized over silylated SBA-15 with high hydrothermal stability.