Mg-Al mixed oxides with a different Mg/Al molar ratio (from 1.8 to 7.2) were prepared by thermal pre-treatment of hydrotalcite-like precursors at 450 degrees C and used as catalysts for transesterification of rapeseed oil. The goal of the work is to study the influence of Mg/Al molar ratio on the total concentration of basic sites, crystallite size of MgO, specific surface area, yield of ester and leaching of magnesium from the catalyst to liquid products. It was found that the total concentration of basic sites decreases and the crystallite size of MgO, specific surface area and the yield of ester increase with an increasing Mg/Al molar ratio for Mg-Al-Na mixed oxides pre-treated at 450 degrees C. There was observed only negligible magnesium leaching from solid Mg-Al mixed oxides to the liquid phases. (C) 2014 Elsevier B.V. All rights reserved.