Fig. 1: Reaction coordinate diagram for a typical zeolite catalyzed, aqueous-phase reaction.

Initially, the reactant (R) is solvated by the liquid phase outside the porous catalyst and the proton in the catalyst is not hydrated (a). The hydration of the proton by water forms the specific acid (b), which is followed by the adsorption of R in the catalyst pore (c). The hydrogen bonding or protonation of R in the catalyst pore is accompanied by a partial or complete de-solvation of the proton (d), which is followed by the acid catalyzed chemical transformation by going through a transition state (TS). Water molecules in brown and red are involved in the specific acid solvation sphere and in the TS, respectively. The solid curved lines represent the zeolite pore walls. The enthalpy changes (ΔH), apparent activation energy (E_{a, app}), and intrinsic activation energy (E_{a, int}) are dependent on interactions with the solvent environment.