Abstract: A porous solid acid catalyst having high concentration of acidic sites and a large surface area includes a porous silica support and a sulfonated carbon layer disposed within the pores of the silica support. The catalyst, in certain embodiments, has a concentration of —SO3H groups of at least about 0.5 mmol/g and a predominant pore size of at least about 300 ?. The catalyst is used to catalyze a variety of acid-catalyzed reactions, including but not limited to alkylation, acylation, etherification, olefin hydration and alcohol dehydration, dimerization of olefin and bicyclic compounds, esterification and transesterification. For example, the catalyst can be used to catalyze esterification of free fatty acids (FFAs) and, in certain embodiments, to catalyze transesterification of triglycerides in fats and oils.