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Microwave-assisted preparation of a new esterification catalyst from wasted flint kaolin

2012; Elsevier BV; Volume: 103; Linguagem: Inglês

10.1016/j.fuel.2012.07.017

1873-7153

Alex de Oliveira, Laura Rafaela da Silva Costa, Luíza Helena de Oliveira Pires, Luís Adriano Santos do Nascimento, Rômulo Simões Angélica, Carlos Emmerson Ferreira da Costa, José Roberto Zamian, Geraldo Narciso da Rocha Filho,

Layered Double Hydroxides Synthesis and Applications

Amazon flint kaolin, considered useless from an economic and industrial point of view, was calcined at 850 and 950 °C to obtain metakaolin samples. These samples were subsequently treated with sulfuric acid (4 M) by assisted heating with microwave radiation. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy and N2 physisorption; the surface acidity was determined by titration with 0.2 M KOH. The materials obtained were used as catalysts in the esterification of oleic acid with methanol. Metakaolin that was calcined at 850 °C and activated at 400 W for 15 min presented a surface area of 187 m2 g−1, yielding acidic sites with a concentration of 4.32 mmol g−1 and a conversion of 96.5% (115 °C, 40 min, molar ratio of oleic acid: methanol 1:60). In addition to a lower preparation time, the flint metakaolin activated by microwave radiation gave a catalytic performance equivalent or superior to the one prepared by reflux, as well as it showed considerably reduced reaction time and temperature.