Applied Energy, Vol.134, 283-289, 2014
Biodiesel production via esterification of oleic acid catalyzed by picolinic acid modified 12-tungstophosphoric acid
Esterification of free fatty acids with alcohols catalytic by acid catalysts can synthesize sustainable production of biofuel. In this work, 12-tungstophosphoric acid was modified by picolinic acid to prepare solid acid catalyst (PA-HPW) and applied to the esterification, which was proved to be an efficient catalyst for the esterification of oleic acid and alcohols. For characterization of the catalysts, XRD, FT-IR, SEM and potentiometric titration method were employed. These analyses showed that there was no decomposition of the Keggin structure of 12-tungstophosphoric acid during preparation and esterification. The PA-HPW catalyst presented high acidity and good stability in esterification mixtures. Various reaction parameters, such as methanol/oleic acid molar ratio, catalyst dosage, reaction temperature and time were systematically examined. A quantitative conversion (100%) of oleic acid was achieved, using the most active modified catalyst at 80 degrees C with a 7 wt % catalyst/oleic acid ratio for 5 h, at a 10:1 of alcohol/acid mole ratio. The catalyst can be easily recovered and reused, which indicated that the PA-HPW catalyst is a promising new type of heterogeneous acid catalyst for conversion of free fatty acid feeds to biodiesel. (C) 2014 Elsevier Ltd. All rights reserved.