Esterification of free fatty acids to biodiesel over heteropolyacids immobilized on mesoporous silica

Tungstophosphoric acid (PW) molybdophosphoric acid (PMo) and tungstosilicic acid (SiW) immobilized on SBA-15 were used as catalysts in the esterification of palmitic acid with methanol at 60 C Catalysts were characterized by N-2 adsorption FUR X-ray diffraction ICP-AES and TEM All catalysts exhibited high catalytic activity in palmitic acid esterification with methanol It was observed that the catalytic activity decreases in the follow series PW1-SBA-15 > SiW-SBA-15 > PMo-SBA-15 A series of PW immobilized on SBA-15 with different PW loadings from 27 wt% to 8 3 wt% were prepared It was observed high catalytic activity with low amount of tungstophosphoric acid immobilized on SBA-15 In order to optimize the reaction conditions the effect of different parameters such as catalyst loading carbon length of the alcohol and temperature molar ratio of fatty acid to methanol in the presence of PW3-SBA-15 were studied PW3-SBA-15 catalyst can be separated from reaction system for re-use It was observed a small leaching of the PW from SBA-15 to liquid phase PW3-SBA-15 catalyst was also used in the esterification of stearic and oleic acid with methanol High catalytic activity was observed (C) 2010 Elsevier BV All rights reserved