A highly efficient solid acid catalyst could serve not only as a pretreatment catalyst to remove free fatty acids (FFA) from the triglycerides, but also as a catalyst for the conversion of the oil to biodiesel. To examine the catalytic performance of the mesoporous silica nanoparticle (MSN) solid acid catalysts, the catalytic properties of the sulfonic acid-functionalized mesoporous silicas were tested for the methyl esterification of a common FFA (palmitic acid) with excess methanol. MSN-SO3H-BSA had significantly higher activity than the other MSN materials. While the overall conversion achieved using MSN-SO3H-BSA was similar to H2SO4, the initial reactivity of the solid catalyst was higher than for H2SO4. Esterification of FFA with methanol releases water that is known to limit the extent of the esterification reaction. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (San Diego, CA Spring 2005).