Clean approach for catalytic biodiesel production from waste frying oil utilizing K2CO3/Orange peel derived hydrochar via RSM Optimization.

Energy worldwide crisis devotes the concern of the scientific forums to find better solutions for an efficient and economical energy source instead of the conventional Petro-fuels. Herein, this study addresses the utilization of plant waste-derived heterogeneous catalysts for efficient biodiesel (BD) production from waste frying oil (WFO). Hydrochar is fabricated from orange peels to valorize the waste-to-fuel approach through utilizing plant residue and WFO to make the whole process more economical and environmentally benign. Hydrothermal carbonization of orange peels is used for the fabrication of hydrochar. Then, a novel potassium carbonate/orange peel-derived activated hydrochar (KC/OAH) heterogeneous catalyst is employed for a competent methanolysis of WFO. Various characterization techniques are employed to elucidate the physicochemical properties of the proposed materials. The evaluated optimal mass ratio of the catalyst composition is 2:1 K2CO3: OAH (2-KC/1-OAH). Next, a central composite design (CCD) via response surface methodology (RSM) is utilized to disclose the optimum operational parameters at which the reaction is implemented. Optimum conditions of 4.4 wt %, 6.6:1 methanol to oil molar ratio, and 108 min reaction time at a fixed reaction temperature of 50 °C result in biodiesel conversion of c.a. 89.2 %. A low minimum selling price (MSP) of biodiesel of 1.12 $/kg is developed, which confirms the low cost of the overall process to produce the biodiesel. The significant leaching of K+ (2-KC/1-OAH) necessitates chemical regeneration via re-soaking of the spent catalyst in K2CO3, which restores the activity and provides the same high biodiesel conversion as the genuine catalyst. Ultimately, the physico-chemical properties of the produced biodiesel are found to be compatible with international limits, which elevates the safe usage of this fuel in automobile engines.