Immobilized L-arginine on methacrylate polymer as reusable heterogeneous catalyst for crude palm oil transesterification

The development of enviromentally friendly and reusable heterogenous catalyst has attracted significant attention for sustainable biodiesel production from low-cost feedstocks such as crude palm oil (CPO). This study aims to synthesize and evaluate an L-arginine immobilized methacrylate-based porous polymer as an efficient and reusable heterogenous base catalyst for CPO transesterification. In this study, a porous polymer synthesized from glycidyl methacrylate (GM) and ethylene glycol dimethacrylate (EGD), denoted as poly(GM-co-EGD), was employed as a support matrix for L-arginine immobilization to develop an efficient heterogeneous base catalyst for the transesterification of CPO. The catalyst was prepared via free radical polymerization followed by covalent immobilization of L-arginine onto the porous polymer framework. FESEM analysis revealed a well-developed interconnected porous morphology, which was further supported by textural characterization showing a high BET surface area of 650 m² g⁻¹ and a total pore volume of 2.07 cm³ g⁻¹. FTIR spectra confirmed the successful chemical bonding between L-arginine and the polymer matrix. Thermogravimetric analysis indicated good thermal stability of the polymeric catalyst up to 120 °C, suitable for transesterification conditions. The basic strength evaluated using Hammett indicators showed moderate-to-strong basicity (9.9 < H_ < 12), while quantitative back titration with benzoic acid revealed that the catalyst with a poly(GM-co-EGD):L-arginine ratio of 1:2 exhibited the highest total basicity of 1.01 mmol g⁻¹. Process optimization using Response Surface Methodology with a Box–Behnken design produced a highly accurate quadratic model (R² = 0.9992). Under optimal conditions, a biodiesel yield of 82.34 ± 1.08% was achieved, consistent with model predictions. The catalyst maintained stable performance over five consecutive cycles, demonstrating its potential as a green and sustainable catalyst for biodiesel production from CPO.