The bifunctional active sites on carbon supported Fe-Mo bimetallic catalyst to improve Kraft lignin liquefaction

Abstract

Carbon-supported Fe-Mo bimetallic catalysts were synthesized for the thermal catalytic ethanolysis of lignin to liquid fuels composed of aromatic monomers. A yield of 40.7 wt % of lignin oil, consisting of 38.8 wt % phenol monomers and 39.3 wt % benzeneacetaldehyde monomers, was obtained in the presence of Fe-Mo-P catalysts (1:0.5) at 290 °C for 4 h in the supercritical ethanol solvent (6.5 MPa). The catalysts exhibited a rich distribution of α-MoC nanoparticles, Fe0 nanoclusters, surface oxygen defects, and active species of Mo6+ and phosphoric acid on the graphitized microporous carbon substrate. The synergistic effects of these active components were crucial for enhancing lignin liquefaction efficiency. The ethanolysis of the lignin model compound revealed that the Fe-Mo bimetallic catalyst can facilitate double cracking of C-C/C-O bonds under supercritical ethanol conditions. In situ Raman and FT-IR characterization were performed to monitor the transformation of the Fe-Mo bimetallic catalyst from the precursor to the carbon material, including the dehydration and carbonization of the organic precursor.