Seaweed-derived biochar with multiple active sites as a heterogeneous catalyst for converting macroalgae into acid-free biooil containing abundant ester and sugar substances

A series of environmentally friendly and low-cost seaweed-derived biochar catalysts (SDBCs) were prepared. Results indicated that metals modified SDBCs at high temperature displayed highly developed porous structures and more aromatic rings with no less than 6 benzene rings along with defects and heteroatoms. The inorganic minerals were mostly present in the form of NaCl and KCl in the seaweed-derived biochars. Subsequently, the performance of SDBCs was examined through ex-situ catalytic pyrolysis of Enteromorpha clathrate. Results demonstrated that biooils from catalytic pyrolysis exhibited higher (H/C)(eff) and HHVs in comparison to the control. Interestingly, the carboxylic acids were decreased significantly after using SDBCs. The mechanism is that a significant amount of hydroxyl groups existed in biochar could react with carboxylic group to form FAMEs. Additionally, the metals Cu, Ce and Fe loaded on the BC-800 catalyst had particular effects on the C-C bond and - C = O - units in the pyrolysis volatiles. It was suggested that Cu-BC-800 catalyst was a promising metal modified biochar catalyst for producing acid-free biooils containing abundant esters and sugars.

Automated summary

The study demonstrated that metal-modified seaweed-derived biochar catalysts can effectively improve the quality of pyrolysis biooils and reduce the content of carboxylic acids.