Stable sulfated zirconia can be prepared by impregnation with zirconium sulfate on a mesoporous silica type MCM and ulterior calcination at 750 degrees C. The thermal decomposition of this salt leads to the formation of monoclinic/tetragonal zirconia with some sulfate ions strongly retained, which are acidic and enable to produce the ethanolysis of sunflower oil at 200 degrees C. With only 14.6 wt% of catalyst containing 30% of zirconium sulfate, 91.5 wt% of biodiesel formation is attained. The catalysts are stable and no leaching of sulfate species to the reaction medium is found. Moreover, these catalysts give rise to the simultaneous esterification of FFAs and the transesterification of triglycerides even with 9% of FFAs. The activity of this catalyst is still maintained in the presence of 5 wt% of water and after three catalytic cycles without any treatment. (C) 2011 Elsevier B.V. All rights reserved.