text: Acid catalysis is mainly used for organic chemical reactions. Many acids can function as sources for the protons. Acid used for acid catalysis include hydrofluoric acid (in the alkylation process), phosphoric acid, toluenesulfonic acid, polystyrene sulfonate, heteropoly acids, zeolites.
  Strong acids catalyze the hydrolysis and  transesterification of esters, e.g. for processing fats into biodiesel. In terms of mechanism, the carbonyl oxygen is susceptible to protonation, which enhances the electrophilicity at the carbonyl carbon.