Fe-Ni bimetallic-modified lignin-based biochar catalysts for enhanced aromatic hydrocarbon production via ex-situ catalytic fast pyrolysis of lignin

The extraction of lignin-derived pyrolysis oils has received much attention as a potential alternative to conventional petroleum-based fuels and chemicals. This study presented a one-step synthesis approach to prepare Fe-Ni bimetallic-modified lignin-based biochar (xFe-yNi/LC) catalysts, and investigated the effects of bimetallic interactions on aromatic hydrocarbon formation and its pathways during the ex-situ catalytic fast pyrolysis of enzymatically hydrolyzed lignin. The results demonstrated that the combination of Fe and Ni not only modified the porous structure of the catalyst but also formed Fe-Ni alloy, regulating the content of Lewis acid sites to enhance aromatic hydrocarbon production. When the catalyst was 20Fe-5Ni/LC, the Lewis acid site content reached a maximum of 38.68 μmol/g. Additionally, the aromatic hydrocarbon content reached a peak value of 19.06 area% when the ratio of lignin to 20Fe-5Ni/LC was 1:2. This represented an improvement of 47.98 % compared to the lignin pyrolysis without the catalyst. The bimetallic catalyst exhibited excellent thermal stability, with the aromatic hydrocarbon content still achievable at 8.66 area% after four cycles of experiments.