Surface modified magnesium oxides for production of biodiesel via heterogeneous base catalyst transesterification of palm oil

Abstract

Surface morphology of prepared alkaline earth metal oxide MgO contributes to the effect of basicity and reactivity in heterogeneous catalysis reactions. In this study, two methods to prepare surface modified MgO were employed for comparison. The first method is by conventional (CP-MgO) and the second method by aerogel (AP-MgO). The methods of preparation will differentiate the effect of size and morphology towards basicity and reactivity. For conventional method, commercial magnesium oxide (CM-MgO) was first transformed into its hydroxide, CP-Mg(OH)2 followed by heat under vacuum at 10-3 mbar. For aerogel method, magnesium ribbon was transformed into its magnesium hydroxide AP-Mg(OH)2 followed by heat and vacuum as in conventional method. In both methods, magnesium hydroxides were heated under vacuum at temperatures 100, 200, 300, 400, 500, 600 and 700°C respectively. The surface modified magnesium oxides were then characterized. Detailed characterization involving Fourier Transform Infra-Red (FTIR), Thermogravimetry Analysis (TGA), X-Ray Powder Diffraction (XRD), Nitrogen Gas Adsorption, Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX) and basicity titration has allowed a rationale explanation for the high chemical reactivities. In this study, the prepared aerogel APMgO, had a high surface area compared to the conventional CP-MgO. This is however due to the smaller nano particle size of AP-MgO as compared to CP-MgO. The main factors of AP-MgO which contributes to the high reactivity are due to the pore volume and size distribution, unusual surface morphologies, and trace residual surface of –OH and –OCH3. This will then effect the percentage conversion of transesterification reaction when compared to CP-MgO. To study the reactivity both of the best prepared CP-MgO and AP-MgO were used in base heterogeneous catalyst for transesterification of palm oil to fatty acid methyl ester or also known as biodiesel. The resulting transesterification reaction of palm oil to biodiesel was then studied using Gas Chromatography equipped with Flame Ionization Detector (GCFID) and the highest percentage conversion of biodiesel of the best catalyst used was AP-MgO at 700 oC is 94.3%. Further analysis of the biodiesel products was then characterised using FTIR and Gas Chromatography equipped with Mass Spectrometry (GC-MS) to determine the components of complex organic mixtures.