Methanolysis of low-FFA waste cooking oil with novel carbon-based heterogeneous acid catalyst derived from Amazon açaí berry seeds

Performance of a novel acid heterogeneous catalyst derived from seeds of Amazon açaí berry, an abundant waste biomass in Brazil, was evaluated on the methanolysis of waste cooking oil with low FFA. The MeOH-to-Oil ratios (10:30–10:60 w/v), catalyst dosages (6–10 wt% of oil), times (90–210 min), temperatures (55–65 °C) and stirring speeds (400–600 rpm) were organized in a Box-Behnken factorial design studied at 95% confidence level. All product phases were characterized by BET, XRD, TGA-DTG, FT-IR, SEM, pH and pHpzc. Catalyst showed excellent textural properties, low crystallinity, a mesoporous highly-amorphous structure, thermal stability and great adherence of –SO3H groups (1.76 mmol g−1). Conversion of WCO varied between 45.9 and 97.1%. Process optimization and validation resulted in 89% maximum optimal conversion when variables were 10:38 (w/v), 61 °C, 8.25 wt% of WCO, 209 min and 400 rpm. Catalyst reached 11 cycles of reuse and showed statistically higher performance than H2SO4 and KOH in homogeneous form, also higher than other activated carbon-derived catalysts. Costs of production were considerably lower than that of Amberlyst-15®. At 95% confidence level, heterogeneous acid catalyst derived from açaí berry seeds can figure among other biomass-derived catalysts reported in the literature.