LAUSR

Abstract The Mg-Fe hydrotalcites with a constant molar ratio (Mg/Fe 2.5:1) were synthesized from two types of precursors (chlorides and nitrates of metals) and thermally pre-treated at different temperatures (500 and 600 °C). It was found that the crystallite size of hydrotalcite increases with an increasing aging time. The synthesized materials were tested in the transesterification of rapeseed oil. All synthesized materials were characterized by several techniques such as X-ray Powder Diffraction, thermogravimetric analysis with a mass spectrometer, the determination of specific surface area, pore size distribution and basicity of oxides. It was found that crystallite size, the amount of the crystalline phase and specific surface area were almost the same for both precursors. After calcination, the mixed oxides from the nitrate precursors revealed higher amount of basic sites and population of stronger basic sites than from the chloride precursors. The rehydration, i.e. the restoration of a layered structure, successfully proceeded for hydrotalcite synthesized from nitrates calcined at 500 °C. However, in the case of chlorides, the hydrotalcite had to be calcined at 600 °C so that the rehydration was successful. The materials synthesized from chlorides have a lower conversion (25%) than material synthesis from nitrates (60%).