This work has studied a range of acidic catalysts which have been prepared through the modification of mesoporous silica materials. Specifically we have prepared -SO3H modified materials (in the presence and absence of a hydrophobic component) and-COOH and -CN materials. We have characterized these catalysts using TEM, TGA, TPD of probe molecules and IR and we have analysed their activity in the esterification of octanoic acid and the transesterification of triacetin. Activity in the esterification reaction (in which all catalysts are active) is not determined by the acid site concentration of the catalyst while the activity of active catalysts in the transesterification reaction (in which only -SO3H materials are active) appears related to acid site concentration. (C) 2011 Elsevier B.V. All rights reserved.