Zinc oxide supported silver nanoparticles as a heterogeneous catalyst for production of biodiesel from palm oil

Biodiesel, also called fatty acid methyl esters (FAME), a promising alternative to petroleum diesel, has become more attractive in recent years due to its environmental friendliness coupled with its accessibility from renewable resources. This work investigated the novel zinc oxide supported silver nanoparticles (ZnO@Ag NPs) catalyzed transesterification of palm oil to biodiesel. Novel ZnO@Ag NPs were synthesized via homogeneous precipitation of Zn(OH)(2) and reduction of Ag(I) to Ag (0). During the preparation of nanocatalyst, polyethylene glycol (PEG 4000) played a dual role as both the surfactant and reducing agent. The synthesized NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and BET analysis. Biodiesel formation was confirmed by H-1 and C-13 NMR spectroscopic analysis. In addition, different constituents of FAME were identified using GC-MS analytical technique. Under the optimum reaction conditions (methanol to oil ratio, 10:1, catalyst loading, 10 wt%, temperature 60 degrees C and time, 60 min), the percentage conversion of triglycerides to corresponding FAME was 97% as determined by H-1 NMR. Catalyst recyclability tests confirmed that ZnO@Ag NPs could be reused at least for five successive cycles without appreciable loss in its activity.