Orthovanadate intercalated CuFe-LDO catalyzed hydrothermal liquefaction of microalgae for low nitrogen bio-oil production

Hydrothermal liquefaction (HTL) of microalgae for bio-oil production is a promising strategy to avoid extensive fossil fuel utilization, while tandem amidation and Maillard reactions during hydrolysis of cellular compounds unavoidably result in formation of nitrogen containing (N -containing) compounds, reducing quality of bio-oil. Accordingly, VO43 intercalated Cu-Fe layered double oxides named as Cu2Fe-VO4-LDO is firstly synthesized to both catalyze hydrolysis of cellular compounds and block N -containing compounds formation. The results indicate Cu2Fe-VO4-LDO can improve bio-oil yield from 19.32 to 20.32 wt%, with decrease of N/C ratio from 0.70 of control to 0.67 of experimental group, and increase of H/C ratio from 0.129 to 0.132. The insert of VO43 provides more strong -acid sites, which are beneficial to hydrolysis of cellular compounds. Meanwhile, more strong -base sites of Cu2Fe-VO4-LDO promote decarboxylation of fatty acids and removing amino -group of amino acids, subsequently improve production of alkanes. Furthermore, the reversible oxidation of VO43 promotes oxidation of reducing sugars, blocking tandem amidation and Maillard reaction between intermedia of hydrolyzed lipids, carbohydrates, and proteins. This work reports a methodology for synthesis of Cu2Fe-VO4-LDO with strong acid -base sites and reversible oxidize interlayer sites, providing a strategy to simultaneously improve biooil yield and reduce its N/C ratio.