A novel peanut shell-derived biochar/KOH heterogeneous catalyst for biodiesel production from waste cooking oil: RSM optimization and diesel engine performance assessment

چکیده مقاله

A heterogeneous catalyst was synthesized via the pyrolysis of agricultural waste, employing KOH-activated biochar derived from peanut shells. This catalyst offers an innovative and cost-effective solution for converting waste cooking oil (WCO) into biodiesel. Its structural and chemical properties were characterized through various techniques, including XRD, FT-IR, EDS/mapping, TEM, SEM, and BET analysis. To identify the optimal reaction parameters, response surface methodology (RSM) was applied. Under the optimized conditions a WCO-to-methanol molar ratio of 1:12, catalyst loading of 4.75 wt%, reaction duration of 4 h, and a constant temperature of 65 °C, a maximum biodiesel yield of 94% was achieved. The catalyst demonstrated good recyclability, maintaining an efficiency of 78.65% after seven consecutive cycles. Engine performance analysis revealed that, under full load conditions, increasing the biodiesel content in the fuel blend from 0 to 30 vol% resulted in a 27.27% rise in brake specific fuel consumption. Consequently, brake thermal efficiency decreased by 12.45%, and exhaust gas temperature dropped by 29.14%. Under maximum load conditions, the use of B30 fuel resulted in emission reductions of 38% in carbon monoxide and 14.02% in unburned hydrocarbons. These results demonstrate that biodiesel fuel blends produced with KOH-activated peanut shell biochar contribute to carbon emission reduction. Moreover, elevated levels of CO₂ and NO_x emissions were observed, reaching 30.42 and 32.90%, respectively. This research introduces a sustainable and environmentally feasible method for producing biodiesel, which enhances catalyst performance and reduces carbon emissions.