<![CDATA[The development of environmentally friendly catalysts for converting waste cooking oil (WCO) into renewable energy continues to attract significant attention. In this study, mesoporous boehmite (γ-AlOOH) was synthesized from alumina derived from Lapindo mud, using Sapindus rarak extract (SRE) as a natural soft template. The saponins present in SRE play a role in regulating structure, controlling crystal growth, and enhancing porosity during the hydrothermal synthesis process. Characterization results confirmed the formation of orthorhombic γ-AlOOH, with improved physicochemical properties observed as the SRE concentration increased. The catalyst synthesized with 50 wt% SRE exhibited a surface area of 85.72 m²/g and a well-defined mesoporous structure. Nickel was subsequently incorporated into the 50 wt% SRE-derived γ-AlOOH to generate bifunctional catalytic sites, which are essential for the deoxygenation of WCO into biofuel. Process parameter optimization was conducted using response surface methodology (RSM) with a Box–Behnken design. The optimal reaction conditions were identified as 4 hours of reaction time, a temperature of 350°C, and a catalyst concentration of 5 wt%, resulting in a product yield of 78.37%. GC–MS analysis revealed that the products were predominantly composed of C15–C21 hydrocarbons, indicating biofuel formation via decarboxylation, hydrodeoxygenation, and decarbonylation pathways. This study demonstrates that γ-AlOOH synthesized using an SRE-based template is a promising and sustainable catalyst for biofuel production from WCO.]]>
