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Rare earths namely lanthanum (La), neodymium (Nd) and cerium (Ce) obtained from the monazite concentrate processing were comprehensively characterized using XRF, XRD, FTIR, N2 adsorption–desorption, CO2/NH3-TPD and SEM to reveal their catalytic performance in esterification of oleic acid for biodiesel production. The effect of calcination temperatures (500–1000 °C) on the catalyst properties and biodiesel conversion was also investigated. The catalytic performances of the catalysts were tested under the conditions of catalyst loading 3 wt%, molar ratio of oil to methanol 1:20, reaction temperature 200 °C, stirring rate 600 rpm for 5 h. It is interesting that the Ce catalyst calcined at 1000 °C showed the best performance and the highest FAME content of 78.54% could be achieved, even its acid sites was very low, which is probably associated to the availability of oxygen vacancies at high calcination temperature. The La catalysts calcined at 600 °C exhibited the balancing of strong Lewis acid and Lewis basic sites, which is related to the catalytic activity with FAME content of 74.44%. For the catalytic performance of Nd catalysts, the FAME content of 63.60% was obtained at calcination temperature of 500 °C, which was lower than those La and Ce catalysts. © 2022 The Author(s) |
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