Decarbonylation of Fatty Acids to Alkenes over CoPc/MWCNT: Active Sites and Reaction Mechanism

The decarbonylation of biomass-derived fatty acids offers a green and sustainable route to high-value long-chain alkenes. Nitrogen-doped carbon-supported cobalt (Co-NC) catalysts have emerged as promising candidates for fatty acid decarbonylation, attributed to their exceptional catalytic activity and cost-effectiveness. However, identifying the active sites and elucidating the reaction mechanism remain significant challenges. To address these issues, we developed Co single-atom-rich catalysts (CoPc/MWCNT and pyrolyzed derivatives CoPc/MWCNT-X) via the impregnation of cobalt phthalocyanine onto multiwalled carbon nanotubes (MWCNTs), followed by pyrolysis. These catalysts exhibited a high stearic acid decarbonylation activity, increasing the heptadecene yield from 12.9 to 47.4%, with an alkene-to-alkane ratio of up to 4.3. Comprehensive characterization and control experiments conclusively demonstrated that Co single-atom sites serve as the active sites, while coexisting Co/CoO nanoparticles showed negligible activity and no synergistic effects. In situ DRIFTS revealed carbonyl group adsorption on Co single atoms, with DFT calculations confirming directional alkene production via C–O bond cleavage. This work establishes a facile synthetic strategy for high-performance decarbonylation catalysts and unambiguously identifies the critical single-atom active sites while enabling a profound understanding of fatty acid conversion mechanisms.