Biodiesel production from sunflower oil by tungsten oxide supported on zirconium doped MCM-41 silica

A series of zirconium doped MCM-41 silica supported WOx solid acid catalysts, with WO3 loading ranging from 5 to 25 wt%, has been prepared by impregnation with ammonium metatungstate. After activation at 700 degrees C. these catalysts are active in the transesterification of sunflower oil with methanol at 200 degrees C, with a biodiesel yield higher than 80% after 2.5 h of reaction. The maximum activity (82 wt% of FAME yield) is found for the catalyst with 15 wt% WO3 loading, which is able to simultaneously catalyze the esterification and transesterification of simulated used oils, with an acidity degree as high as 9.1%. Moreover, this catalytic activity is maintained in the presence of 5 wt% of water and after three cycles of reutilisation, without any treatment of the catalyst. (C) 2010 Elsevier B.V. All rights reserved.