The equilibrium-limited steady-state nonisothermal behavior of an integral packed-bed reactor is described for the liquid-phase synthesis of ethyl tert-butyl ether with a model that is inherently consistent with thermodynamics. It involves a coupled one-dimensional mass- and enthalpy-balance equations with temperature-dependent thermochemical properties and reaction equilibria. The model accounts for the nonideal nature of the liquid-phase reaction system by utilizing species activities in the rate expression for the reversible reaction, which is also consistent with thermodynamic equilibrium. Experiments agreed well with theory with all of the kinetic, thermodynamic and other physicochemical parameters being obtained from independent experiments, indicating that the theoretical approach is robust. Further, the results clearly endorse the use of species activities rather than concentration, or mole fractions, in the rate expression for the nonideal liquid-phase reactions. There is a paucity of such studies in the literature, especially for liquid-phase nonisothermal packed-bed reactor analysis.