Transesterification of rapeseed oil to biodiesel over Zr-dopped MgAl hydrotalcites

• Zr modification of standard MgAl hydrotalcites causes an increase of their basicity.
• ZrMgAl hydrotalcites were applied for the first time to synthesis of biodiesel from rapeseed oil.
• Introduction Zr atoms to the structure of MgAl hydrotalcite causes an increase conversion of glycerides to nearly 100%.
• Reaction parameters of transesterification process were optimized.

Zr-dopped Mg–Al hydrotalcites with different Zr/Mg molar ratios were prepared and characterized by powder X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), thermogravimetric and differential thermal analysis (TGA-DTA) and scanning electron micrograph (SEM). It was confirmed by XRD that the materials had a similar to Mg-Al hydrotalcite structure. The hydrotalcite catalyst calcined at 773 K. In the study of the selected reaction conditions such as the reaction time and the amount of added catalyst were evaluated. It was found that modification of double layered structure of MgAl hydrotalcite with tetravalent cation Zr4+ resulted in significant increase in catalytic activity in transesterification of rapeseed oil as compared to described in the literature results for MgAl hydrotalcites. The highest conversion of oil 99.9% was obtained for hydrotalcite with molar ratio of Zr: Mg: Al = 0.45: 2.55: 1.00.

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