Microwave-modified hydrotalcites for the transesterification of soybean oil

The effects of hydrothermal treatment (traditional and microwave-assisted) in the catalytic activity of hydrotalcite were studied in the soybean oil methanolysis for a biofuel production. The catalysts were produced by coprecipitation (pH >= 10) and then characterized by x-ray diffraction, infrared spectroscopy, scanning electron microscopy, surface chemical composition, N-2 physisorption at 77 K and surface basicity. Reactions were carried out at 180 degrees C for 60, 120 and 180 min, molar ratio methanol:soybean oil of 12:1 and 5 wt% of the catalyst. The microwave treatment reduced the aluminum content of catalyst lamellae and increased the surface basicity. The best yield of methyl esters was 95.6% for the catalyst treated by microwave at 110 degrees C for 300 min. The high yield of methyl esters shows that the use of microwaves in the synthesis of hydrotalcite can reduce the preparation time and increase the industrial competitiveness of this material as a catalyst in the biofuels industry.