Assessing the potential of different nano-composite (MgO, Al2O3-CaO and TiO2) for efficient conversion of Silybum eburneum seed oil to liquid biodiesel

This study investigated the potential of nano-composite MgO, Al2O3-CaO and TiO2 for efficient conversion of novel non edible seed oil of Silybum eburneum into liquid biodiesel. Silybum eburneum contains oil contents (37.7%) and low free fatty acid (FAA) value (0.16 mg KOH/g). The synthesized heterogeneous nano-catalysts were characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Energy Dispersive X-Ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM) techniques. The highest conversion efficiency was achieved (91% biodiesel yield) using MgO catalyst followed by Al2O3-CaO and TiO2 at 0.1% catalysts loading. The optimized experimental variables comprised of molar ratio (1:3), temperature (70 degrees C), reaction time (3 h.) and stirring rate (600 rpm) using reflux transesterification route. The XRD analysis showed the sizes of the crystal lattices with a sequence of 13 nm for MgO, 29 nm for Al2O3-CaO and 37 nm for TiO2 which reveals that smaller the size of the crystal structure, higher will be the conversion efficiency. The SEM of MgO showed exclusively porous lamellar like smooth surface highly agglomerated with nano entities with a particle size of 50 +/- 10 nm length or width and about 20 nm thickness. SEM images of Al2O3-CaO nano-particles showed the size range from 27 nm to 75 nm having irregular morphology including spherical as well as rod shape with smooth surface and different size. The diameter of the microsphere calculated was about 26 mu m. SEM for TiO2 demonstrated that the average size was from 68.7 nm to 87.3 nm with interring particle dimension. The shape was proved to be sponge-like with spherical nano-holes. The FT-IR and EDX analysis of the catalyst also supported the study results. Gas Chromatography Mass Spectroscopy (GCMS), Nuclear Magnetic Resonance NMR and FT-IR results confirmed the conversion efficiency of applying nano-catalysts. The results observed a novel finding that the conversion efficiency may increase with reducing the size and increasing the surface area of the nano-heterogeneous catalysts. The prepared composites are cheaper and can be applied for industrial scale production of biomass energy making it more cost effective and economically feasible. (C) 2017 Elsevier B.V. All rights reserved