Combustion Synthesis of the MgAl<sub>2</sub>O<sub>4</sub> Using Glycerin from the Production of Biodiesel

Abstract

This work aims to investigate the glycerin from the biodiesel as fuel in the combustion synthesis into two routes, one for high temperature called direct route, in order to inhibit the formation of acrolein and compare it with the conventional combustion synthesis at low temperatures, using as fuels saccharose, pure glycerin, pure glycerin gel, glycerin from biodiesel, biodiesel from glycerin dried 24 h, biodiesel from glycerin gel dried 24 h to obtain the magnesium aluminate spinel (MgAl2O4). The synthesis was performed from the mixture of the precursors (Al (NO3)3.9H2O and Mg (NO3)2.6H2O) in water with the addition of the fuels. In the direct route case, the mixture was placed in a furnace heated to 500°C followed by calcination at different temperatures for 2 h. In the conventional route cases, the mixtures were slowly heated to 800°C for 2 h. The obtained powders, product of the combustion reactions, were characterized by X-ray diffraction (XRD), laser scattering particle size analyzer and scanning electron microscopy (SEM). The results showed that the product (powder) obtained by direct reaction was the MgAl2O4 as the only crystalline phase formed with particle sizes of approximately 41 μm. Even so, small particles with sizes of about 30 nm were also observed according to measurements on SEM images.