SULFONATED CELLULOSIC FABRIC CATALYST FOR BIODIESEL PRODUCTION FROM WASTE OILS

This work reports the synthesis of a bio-based acid catalyst derived from recycled cellulosic fabric, functionalized via sulfonic grafting, for the conversion of waste cooking oils into biodiesel. The resulting material exhibits a high acid density (1.31 mmol Hg) and a low pHpzc (~2.3), promoting substrate adsorption and protonation. Its catalytic performance was evaluated under various reaction conditions (70 120 C, 5 20 wt% catalyst loading, methanol-to-oil molar ratios of 3:1 15:1). The best operating conditions (90 C, 15 wt%, 9:1 ratio, and 10 h) yielded a FAME conversion of 97%, comparable to commercial resins.The bifunctional catalysis enables single-step transformation of highly degraded oils (acid value 4.8 mg KOH/g, viscosity 42.3 mm/s), as confirmed by GC-MS (>95% conversion) and H NMR (OCH peak at 3.7 ppm). The biodiesel produced meets EN 14214 and ASTM D6751 requirements, with a viscosity of 4.54 mm/s, density of 0.885 g cm, and residual acid value of 0.38 mg KOH/g. The catalyst demonstrates good durability, with conversion decreasing from 97% to 90% after five reuse cycles, confirming SOH site stability and its relevance for circular lipid valorization processes.