Sulfated aluminas were synthesized via the sol-gel method by means of the addition of different ions during the gelling of titanium alkoxide. Both the Lewis and Brönsted acid sites were formed, depending on the sulfate precursor. The catalytic activity of sulfated aluminas was tested by performing the esterification reaction of free fatty acids with ethanol at 86°C by using a fatty acid-alcohol with a molar ratio of 1:10 and 3 wt.% of catalyst. The selectivity towards ethyl ester was 100% in all the catalysts. Through this study, we found that sulfated aluminas showed a higher activity in the esterification reaction than unsulfated γ-alumina. It has been found that the conversion of oleic acid varies according to the sulfate precursor (NH4)2SO4 > H2SO4 > NiSO4, which affects both the acidity strength and textural properties of the catalysts.