Comparative study between catalysts for esterification prepared from kaolins

The esterification of free fatty acids (FFA) is an alternative for the production of biodiesel from oils with high concentrations of FFA. In this paper, catalysts for the esterification of oleic acid with methanol were prepared from two Amazon kaolins (Century and flint ) and two standard kaolins (KGa-1b and KGa-2) that were thermally treated at 950 °C and leached with 4 M sulfuric acid solutions. The activated metakaolin samples were characterized by X-ray diffraction, scanning electron microscopy, N 2 adsorption–desorption and pyridine adsorption studies using TG/DTG and FTIR analysis. The leached metakaolin prepared from Century showed the lowest Al content, the highest number of acidic sites (250.5 μmolPy/g) and offered larger conversion values. The influences of reaction parameters, such as temperature and time, were also investigated. Based on the catalytic results, kaolin was found to be a promising raw material for the production of new solid acid catalysts for the esterification of FFA. In particular, Amazonian flint kaolin, previously considered unusable for biofuel, was found to be amenable to production.