Upgrading Crude Glycerol and Waste Grease to Aromatics via Synergistic Olefin-Aldehyde Coupling

Synergistic glycerol-grease pyrolysis yields high aromatics and deoxygenation rate • Olefin-aldehyde coupling at acid sites reduces carbon loss and boosts aromatization • DFT proves coupling thermodynamically favored over conventional aromatization • Broad feedstock scope and LCA‑confirmed environmental benefits The inefficient valorization of crude glycerol, a major biodiesel byproduct, severely limits the carbon economy of biorefining. Herein, we report a catalytic co‑pyrolysis strategy that synergistically converts crude glycerol and waste grease into aromatics over a rice husk silica-derived Ni/ZSM-5 catalyst, improving carbon utilization. The synergy is driven by an olefin-aldehyde coupling pathway on the acid sites of ZSM-5, where glycerol‑derived propenal reacts with grease‑derived olefins to form readily aromatized cyclic intermediates, minimizing secondary cracking and redirecting carbon toward liquid aromatics. This achieves >85.0% aromatic selectivity with a space-time yield of 1.8 g arom ·h -1 ·g catal -1 , representing an eightfold enhancement over glycerol‑alone catalytic pyrolysis. This coupling mechanism is thermodynamically superior to the traditional Ni-mediated aromatization pathway. Its applicability to diverse fatty acids and real waste oils highlights broad feedstock adaptability. This work establishes a scalable carbon‑efficient route for aromatic production from wastes, offering lower carbon footprint and higher energy gain than conventional alternatives. Download: Download high-res image (233KB) Download: Download full-size image