Catalytic hydrothermal liquefaction of microalgae over mesoporous silica-based materials with site-separated acids and bases

In this study, four kinds of porous silica-based materials with site-separated acids and bases were prepared, the catalysts possess both micropores and mesopores with a specific surface areas ranging from 764 m 2 /g to 1016 m 2 /g. Moreover, the effects of the catalysts on the yield and quality of bio-oil derived from hydrothermal liquefaction (HTL) of microalgae Chlorella were investigated. The results showed that the catalyst had no obvious change on the bio-oil yield, but they exhibited good performance in the improving of bio-oil quality. Catalyst with acids inside and outside of the pores worked best in denitrification of the bio-oil while catalyst with bases inside and outside of the pores achieved the minimum sulfur content of the bio-oil (0.65%). GC–MS analysis indicated that the catalyst with site-separated acids and bases showed magnified selectivity to hydrocarbons (over 50% of peak area). Furthermore, the catalyst could increase the low boiling fraction (<400 °C) of the bio-oil to from 68% to 81%. At last, the plausible mechanism of catalyst on HTL was proposed. This study could provide valuable information for production of high quality bio-oil in future researches.