Optimization of trimetallic Cu–Cr–Ca nanoparticle-catalyzed transesterification of amla (Phyllanthus emblica L.) seed oil: analytical characterization and fuel properties of biodiesel

Abstract

Renewable energy sources are experiencing a surge in demand, motivating substantial study into biodiesel synthesis from non-edible oil sources as a strategy to offset the conflict between food and fuel. The present work focuses on optimizing the trimetallic Cu–Cr–Ca oxide nanoparticle-catalyzed transesterification of a non-food amla (Phyllanthus emblica L.) seed oil, producing high yields of good quality amla oil methyl esters (AOMEs)/biodiesel. Response surface methodology was used to optimize the transesterification process by employing a central composite design with a total of 30 experimental trials, including (2⁴) factorial, (2(2)) axial, and (6) central points. The transesterification process was catalyzed by a newly synthesized trimetallic Cu–Cr–Ca nano-catalyst. Statistical analysis demonstrated the model's significance (p < 0.0001) with a high predicted R² value (0.9958) closely aligned with an adjusted R² value (0.9982). The optimal AOME yield of 92% was achieved at a 9 : 1 methanol-to-oil molar ratio, using 3 g of Cu–Cr–Ca catalyst at 85 °C and 5 h. GC-MS analysis of the produced methyl esters revealed the presence of 85.98% unsaturated and 14.03% saturated fatty acids, indicating the successful accomplishment of the transesterification reaction. FTIR ester stretching peaks at 1734 and 1739 cm⁻¹ further confirmed the completion of transesterification. The fuel properties of AOMEs show potential as an alternative green energy fuel compared with ASTM standards, supporting the optimized nano-catalyzed transesterification for producing Phyllanthus emblica L. seed oil biodiesel with acceptable physico-chemical properties.